CDKN2D

Gene Summary

Gene:CDKN2D; cyclin-dependent kinase inhibitor 2D (p19, inhibits CDK4)
Aliases: p19, INK4D, p19-INK4D
Location:19p13
Summary:The protein encoded by this gene is a member of the INK4 family of cyclin-dependent kinase inhibitors. This protein has been shown to form a stable complex with CDK4 or CDK6, and prevent the activation of the CDK kinases, thus function as a cell growth regulator that controls cell cycle G1 progression. The abundance of the transcript of this gene was found to oscillate in a cell-cycle dependent manner with the lowest expression at mid G1 and a maximal expression during S phase. The negative regulation of the cell cycle involved in this protein was shown to participate in repressing neuronal proliferation, as well as spermatogenesis. Two alternatively spliced variants of this gene, which encode an identical protein, have been reported. [provided by RefSeq, Jul 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:cyclin-dependent kinase 4 inhibitor D
HPRD
Source:NCBIAccessed: 16 March, 2015

Ontology:

What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 16 March 2015 using data from PubMed using criteria.

Literature Analysis

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Tag cloud generated 16 March, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: CDKN2D (cancer-related)

Bai F, Chan HL, Smith MD, et al.
p19Ink4d is a tumor suppressor and controls pituitary anterior lobe cell proliferation.
Mol Cell Biol. 2014; 34(12):2121-34 [PubMed] Free Access to Full Article Related Publications
Pituitary tumors develop in about one-quarter of the population, and most arise from the anterior lobe (AL). The pituitary gland is particularly sensitive to genetic alteration of genes involved in the cyclin-dependent kinase (CDK) inhibitor (CKI)-CDK-retinoblastoma protein (Rb) pathway. Mice heterozygous for the Rb mutation develop pituitary tumors, with about 20% arising from the AL. Perplexingly, none of the CKI-deficient mice reported thus far develop pituitary AL tumors. In this study, we show that deletion of p19(Ink4d) (p19), a CKI gene, in mice results in spontaneous development of tumors in multiple organs and tissues. Specifically, more than one-half of the mutant mice developed pituitary hyperplasia or tumors predominantly in the AL. Tumor development is associated with increased cell proliferation and enhanced activity of Cdk4 and Cdk6 and phosphorylation of Rb protein. Though Cdk4 is indispensable for postnatal pituitary cell proliferation, it is not required for the hyperproliferative pituitary phenotype caused by p19 loss. Loss of p19 phosphorylates Rb in Cdk4(-/-) pituitary AL cells and mouse embryonic fibroblasts (MEFs) and rescues their proliferation defects, at least partially, through the activation of Cdk6. These results provide the first genetic evidence that p19 is a tumor suppressor and the major CKI gene that controls pituitary AL cell proliferation.

Kannan K, Coarfa C, Rajapakshe K, et al.
CDKN2D-WDFY2 is a cancer-specific fusion gene recurrent in high-grade serous ovarian carcinoma.
PLoS Genet. 2014; 10(3):e1004216 [PubMed] Free Access to Full Article Related Publications
Ovarian cancer is the fifth leading cause of cancer death in women. Almost 70% of ovarian cancer deaths are due to the high-grade serous subtype, which is typically detected only after it has metastasized. Characterization of high-grade serous cancer is further complicated by the significant heterogeneity and genome instability displayed by this cancer. Other than mutations in TP53, which is common to many cancers, highly recurrent recombinant events specific to this cancer have yet to be identified. Using high-throughput transcriptome sequencing of seven patient samples combined with experimental validation at DNA, RNA and protein levels, we identified a cancer-specific and inter-chromosomal fusion gene CDKN2D-WDFY2 that occurs at a frequency of 20% among sixty high-grade serous cancer samples but is absent in non-cancerous ovary and fallopian tube samples. This is the most frequent recombinant event identified so far in high-grade serous cancer implying a major cellular lineage in this highly heterogeneous cancer. In addition, the same fusion transcript was also detected in OV-90, an established high-grade serous type cell line. The genomic breakpoint was identified in intron 1 of CDKN2D and intron 2 of WDFY2 in patient tumor, providing direct evidence that this is a fusion gene. The parental gene, CDKN2D, is a cell-cycle modulator that is also involved in DNA repair, while WDFY2 is known to modulate AKT interactions with its substrates. Transfection of cloned fusion construct led to loss of wildtype CDKN2D and wildtype WDFY2 protein expression, and a gain of a short WDFY2 protein isoform that is presumably under the control of the CDKN2D promoter. The expression of short WDFY2 protein in transfected cells appears to alter the PI3K/AKT pathway that is known to play a role in oncogenesis. CDKN2D-WDFY2 fusion could be an important molecular signature for understanding and classifying sub-lineages among heterogeneous high-grade serous ovarian carcinomas.

Sonzogni SV, Ogara MF, Belluscio LM, et al.
p19INK4d is involved in the cellular senescence mechanism contributing to heterochromatin formation.
Biochim Biophys Acta. 2014; 1840(7):2171-83 [PubMed] Related Publications
BACKGROUND: During evolution, organisms with renewable tissues have developed mechanisms to prevent tumorigenesis, including cellular senescence and apoptosis. Cellular senescence is characterized by a permanent cell cycle arrest triggered by both endogenous stress and exogenous stress. The p19INK4d, a member of the family of cyclin-dependent kinase inhibitors (INK4), plays an important role on cell cycle regulation and in the cellular DNA damage response. We hypothesize that p19INK4d is a potential factor involved in the onset and/or maintenance of the senescent state.
METHODS: Senescence was confirmed by measuring the cell cycle arrest and the senescence-associated β-galactosidase activity. Changes in p19INK4d expression and localization during senescence were determined by Western blot and immunofluorescence assays. Chromatin condensation was measured by microccocal nuclease digestion and histone salt extraction.
RESULTS: The data presented here show for the first time that p19INK4d expression is up-regulated by different types of senescence. Changes in senescence-associated hallmarks were driven by modulation of p19 expression indicating a direct link between p19INK4d induction and the establishment of cellular senescence. Following a senescence stimulus, p19INK4d translocates to the nucleus and tightly associates with chromatin. Moreover, reduced levels of p19INK4d impair senescence-related global genomic heterochromatinization. Analysis of p19INK4d mRNA and protein levels in tissues from differently aged mice revealed an up-regulation of p19INK4d that correlates with age.
CONCLUSION: We propose that p19INK4d participates in the cellular mechanisms that trigger senescence by contributing to chromatin compaction.
GENERAL SIGNIFICANCE: This study provides novel insights into the dynamics process of cellular senescence, a central tumor suppressive mechanism.

Yang YL, Hung MS, Wang Y, et al.
Lung tumourigenesis in a conditional Cul4A transgenic mouse model.
J Pathol. 2014; 233(2):113-23 [PubMed] Free Access to Full Article Related Publications
Cullin4A (Cul4A) is a scaffold protein that assembles cullin-RING ubiquitin ligase (E3) complexes and regulates many cellular events, including cell survival, development, growth and cell cycle control. Our previous study suggested that Cul4A is oncogenic in vitro, but its oncogenic role in vivo has not been studied. Here, we used a Cul4A transgenic mouse model to study the potential oncogenic role of Cul4A in lung tumour development. After Cul4A over-expression was induced in the lungs for 32 weeks, atypical epithelial cells were observed. After 40 weeks, lung tumours were visible and were characterized as grade I or II adenocarcinomas. Immunohistochemistry (IHC) revealed decreased levels of Cul4A-associated proteins p21(CIP1) and tumour suppressor p19(ARF) in the lung tumours, suggesting that Cul4A regulated their expression in these tumours. Increased levels of p27(KIP1) and p16(INK4a) were also detected in these tumours. Moreover, the protein level of DNA replication licensing factor CDT1 was decreased. Genomic instability in the lung tumours was further analysed by the results from pericentrin protein expression and array comparative genomic hybridization analysis. Furthermore, knocking down Cul4A expression in lung cancer H2170 cells increased their sensitivity to the chemotherapy drug cisplatin in vitro, suggesting that Cul4A over-expression is associated with cisplatin resistance in the cancer cells. Our findings indicate that Cul4A is oncogenic in vivo, and this Cul4A mouse model is a tool in understanding the mechanisms of Cul4A in human cancers and for testing experimental therapies targeting Cul4A.

Yamada D, Hoshii T, Tanaka S, et al.
Loss of Tsc1 accelerates malignant gliomagenesis when combined with oncogenic signals.
J Biochem. 2014; 155(4):227-33 [PubMed] Related Publications
Glioblastomas frequently harbour genetic lesions that stimulate the activity of mammalian target of rapamycin complex 1 (mTORC1). Loss of heterozygosity of tuberous sclerosis complex 1 (TSC1) or TSC2, which together form a critical negative regulator of mTORC1, is also seen in glioblastoma; however, it is not known how loss of the TSC complex affects the development of malignant gliomas. Here we investigated the role of Tsc1 in gliomagenesis in mice. Tsc1 deficiency up-regulated mTORC1 activity and suppressed the proliferation of neural stem/progenitor cells (NSPCs) in a serial neurosphere-forming assay, suggesting that Tsc1-deficient NSPCs have defective self-renewal activity. The neurosphere-forming capacity of Tsc1-deficient NSPCs was restored by p16(Ink4a)p19(Arf) deficiency. Combined Tsc1 and p16(Ink4a)p19(Arf) deficiency in NSPCs did not cause gliomagenesis in vivo. However, in a glioma model driven by an active mutant of epidermal growth factor receptor (EGFR), EGFRvIII, loss of Tsc1 resulted in an earlier onset of glioma development. The mTORC1 hyperactivation by Tsc1 deletion accelerated malignant phenotypes, including increased tumour mass and enhanced microvascular formation, leading to intracranial haemorrhage. These data demonstrate that, although mTORC1 hyperactivation itself may not be sufficient for gliomagenesis, it is a potent modifier of glioma development when combined with oncogenic signals.

Gluick T, Yuan Z, Libutti SK, Marx SJ
Mutations in CDKN2C (p18) and CDKN2D (p19) may cause sporadic parathyroid adenoma.
Endocr Relat Cancer. 2013; 20(6):L27-9 [PubMed] Related Publications

Felisiak-Golabek A, Dansonka-Mieszkowska A, Rzepecka IK, et al.
p19(INK4d) mRNA and protein expression as new prognostic factors in ovarian cancer patients.
Cancer Biol Ther. 2013; 14(10):973-81 [PubMed] Free Access to Full Article Related Publications
p19(INK4d) (CDKN2D) is a negative regulator of the cell cycle. Little is known of its role in cancer development and prognosis. We aimed to evaluate the clinical significance of p19(INK4d) expression in ovarian carcinomas with respect to the TP53 accumulation status, as well as the frequency of CDKN2D mutations. p19(INK4d) and TP53 expression was evaluated immunohistochemically in 445 ovarian carcinomas: 246 patients were treated with platinum-cyclophosphamide (PC/PAC), while 199 were treated with taxane-platinum agents (TP). CDKN2D gene expression (mRNA) was examined in 106 carcinomas, while CDKN2D mutations in 68 tumors. Uni- and multivariate statistical analyses (logistic regression and the Cox proportional hazards model) were performed for patient groups divided according to the chemotherapeutic regimen administered, and in subgroups with and without TP53 accumulation. High p19(INK4d) expression increased the risk of death, but only in patients with the TP53-negative carcinomas (HR 1.61, P = 0.049 for PC/PAC-treated patients, HR 2.00, P = 0.015 for TP-treated patients). This result was confirmed by the mRNA analysis (HR 4.24, P = 0.001 for TP-treated group). High p19(INK4d) protein expression associated with adverse clinicopathological factors. We found no alterations in the CDKN2D gene; the c.90C>G (p.R30R; rs1968445) polymorphism was detected in 10% of tumors. Our results suggest that p19(INK4d) expression is a poor prognostic factor in ovarian cancer patients. Analyses of tumor groups according to the TP53 accumulation status facilitate the identification of cancer biomarkers.

Qian X, Gu L, Ning H, et al.
Increased Th17 cells in the tumor microenvironment is mediated by IL-23 via tumor-secreted prostaglandin E2.
J Immunol. 2013; 190(11):5894-902 [PubMed] Free Access to Full Article Related Publications
Tumor cell-derived molecules such as cytokines and lipid mediators play a critical role in inducing chronic inflammation in the tumor microenvironment. We found that Th17 cells were increased in the peripheral blood, spleen, and tumor tissues of mammary gland tumor-bearing mice. The Th17 cell survival factor, IL-23, was also overexpressed in tumor tissues isolated from mice and human breast cancer patients. Soluble molecules secreted from breast tumor cells, but not normal breast epithelial cells, induced IL-23 protein secretion in dendritic cells via induction of p19 mRNA expression. Our data further indicate that tumor-secreted PGE2 through EP2 and EP4 receptors enhanced IL-23 p19 gene transcription through binding to the cAMP-response element in the p19 promoter. Blocking PGE2 synthesis by NS398, a COX2 inhibitor, abrogated the enhancement of p19 expression both in vitro and in vivo. Furthermore, blocking protein kinase A (PKA) by H89 completely abrogated the inductive effects of tumor-conditioned medium and PGE2 on p19 transcription, whereas the cAMP active analog, Forskolin, mimics the PGE2 effect. Taken together, our results indicate that tumor-secreted PGE2 induces IL-23, but not IL-12, production in the tumor microenvironment, leading to Th17 cell expansion. This inductive effect of PGE2 on IL-23 p19 transcription is mediated through cAMP/PKA signaling transduction pathway.

Lin S, Wang MJ, Tseng KY
Polypyrimidine tract-binding protein induces p19(Ink4d) expression and inhibits the proliferation of H1299 cells.
PLoS One. 2013; 8(3):e58227 [PubMed] Free Access to Full Article Related Publications
The expression of polypyrimidine tract-binding protein (PTB) is up-regulated in many types of cancer. Here, we studied the role of PTB in the growth of non small cell lung cancer cells. Data showed that PTB overexpression inhibited the growth of H1299 cells at least by inhibiting DNA synthesis. Quantitative real-time PCR and Western blot analyses showed that PTB overexpression in H1299 cells specifically induced the expression of p19(Ink4d), an inhibitor of cyclin-dependent kinase 4. Repression of p19(Ink4d) expression partially rescued PTB-caused proliferation inhibition. PTB overexpression also inhibited the growth and induced the expression of p19(Ink4d) mRNA in A549 cells. However, Western blot analyses failed to detect the presence of p19(Ink4d) protein in A549 cells. To address how PTB induced p19(Ink4d) in H1299 cells, we showed that PTB might up-regulate the activity of p19(Ink4d) gene (CDKN2D) promoter. Besides, PTB lacking the RNA recognition motif 3 (RRM3) was less effective in growth inhibition and p19(Ink4d) induction, suggesting that RNA-binding activity of PTB plays an important role in p19(Ink4d) induction. However, immunoprecipitation of ribonuclearprotein complexes plus quantitative real-time PCR analyses showed that PTB might not bind p19(Ink4d) mRNA, suggesting that PTB overexpression might trigger the other RNA-binding protein(s) to bind p19(Ink4d) mRNA. Subsequently, RNA electrophoretic mobility-shift assays revealed a 300-base segment (designated as B2) within the 3'UTR of p19(Ink4d) mRNA, with which the cytoplasmic lysates of PTB-overexpressing cells formed more prominent complexes than did control cell lysates. Insertion of B2 into a reporter construct increased the expression of the chimeric luciferase transcripts in transfected PTB-overexpressing cells but not in control cells; conversely, overexpression of B2-containing reporter construct in PTB-overexpressing cells abolished the induction of p19(Ink4d) mRNA. In sum, we have shown that PTB plays as a negative regulator in H1299 cell proliferation at least by inducing p19(Ink4d) expression at transcriptional and post-transcriptional levels.

Gogolin S, Ehemann V, Becker G, et al.
CDK4 inhibition restores G(1)-S arrest in MYCN-amplified neuroblastoma cells in the context of doxorubicin-induced DNA damage.
Cell Cycle. 2013; 12(7):1091-104 [PubMed] Free Access to Full Article Related Publications
Relapse with drug-resistant disease is the main cause of death in MYCN-amplified neuroblastoma patients. MYCN-amplified neuroblastoma cells in vitro are characterized by a failure to arrest at the G(1)-S checkpoint after irradiation- or drug-induced DNA damage. We show that several MYCN-amplified cell lines harbor additional chromosomal aberrations targeting p53 and/or pRB pathway components, including CDK4/CCND1/MDM2 amplifications, p16INK4A/p14ARF deletions or TP53 mutations. Cells with these additional aberrations undergo significantly lower levels of cell death after doxorubicin treatment compared with MYCN-amplified cells, with no additional mutations in these pathways. In MYCN-amplified cells CDK4 expression is elevated, increasing the competition between CDK4 and CDK2 for binding p21. This results in insufficient p21 to inhibit CDK2, leading to high CDK4 and CDK2 kinase activity upon doxorubicin treatment. CDK4 inhibition by siRNAs, selective small compounds or p19(INK4D) overexpression partly restored G(1)-S arrest, delayed S-phase progression and reduced cell viability upon doxorubicin treatment. Our results suggest a specific function of p19(INK4D), but not p16(INK4A), in sensitizing MYCN-amplified cells with a functional p53 pathway to doxorubicin-induced cell death. In summary, the CDK4/cyclin D-pRB axis is altered in MYCN-amplified cells to evade a G(1)-S arrest after doxorubicin-induced DNA damage. Additional chromosomal aberrations affecting the p53-p21 and CDK4-pRB axes compound the effects of MYCN on the G(1) checkpoint and reduce sensitivity to cell death after doxorubicin treatment. CDK4 inhibition partly restores G(1)-S arrest and sensitizes cells to doxorubicin-mediated cell death in MYCN-amplified cells with an intact p53 pathway.

Capparelli C, Chiavarina B, Whitaker-Menezes D, et al.
CDK inhibitors (p16/p19/p21) induce senescence and autophagy in cancer-associated fibroblasts, "fueling" tumor growth via paracrine interactions, without an increase in neo-angiogenesis.
Cell Cycle. 2012; 11(19):3599-610 [PubMed] Free Access to Full Article Related Publications
Here, we investigated the compartment-specific role of cell cycle arrest and senescence in breast cancer tumor growth. For this purpose, we generated a number of hTERT-immortalized senescent fibroblast cell lines overexpressing CDK inhibitors, such as p16(INK4A), p19(ARF) or p21(WAF1/CIP1). Interestingly, all these senescent fibroblast cell lines showed evidence of increased susceptibility toward the induction of autophagy (either at baseline or after starvation), as well as significant mitochondrial dysfunction. Most importantly, these senescent fibroblasts also dramatically promoted tumor growth (up to ~2-fold), without any comparable increases in tumor angiogenesis. Conversely, we generated human breast cancer cells (MDA-MB-231 cells) overexpressing CDK inhibitors, namely p16(INK4A) or p21(WAF1/CIP1). Senescent MDA-MB-231 cells also showed increased expression of markers of cell cycle arrest and autophagy, including β-galactosidase, as predicted. Senescent MDA-MB-231 cells had retarded tumor growth, with up to a near 2-fold reduction in tumor volume. Thus, the effects of CDK inhibitors are compartment-specific and are related to their metabolic effects, which results in the induction of autophagy and mitochondrial dysfunction. Finally, induction of cell cycle arrest with specific inhibitors (PD0332991) or cellular stressors [hydrogen peroxide (H(2)O(2)) or starvation] indicated that the onset of autophagy and senescence are inextricably linked biological processes. The compartment-specific induction of senescence (and hence autophagy) may be a new therapeutic target that could be exploited for the successful treatment of human breast cancer patients.

Morishita A, Gong J, Deguchi A, et al.
Frequent loss of p19INK4D expression in hepatocellular carcinoma: relationship to tumor differentiation and patient survival.
Oncol Rep. 2011; 26(6):1363-8 [PubMed] Related Publications
p19INK4D belongs to the family of cyclin-dependent kinase inhibitors (CdkIs) that target the cyclin-dependent kinases and inhibit their catalytic activity. The role of p19INK4D in cell cycle progression in hepatocellular carcinoma (HCC) is poorly characterized. The aim of this study was to examine the expression of p19INK4D in various liver diseases including HCC and to assess its clinical significance in HCC. We examined the expression of p19INK4D by immunohistochemistry in 81 cases of various liver diseases, including 51 HCCs. We analyzed the relationship among p19INK4D expression in HCC in combination with histopathological stage, differentiation, several histopathological factors of possible prognostic value and patient survival. Immunohistochemical analysis revealed the frequent loss of p19INK4D expression consistent with the differentiation of HCC. The loss of p19INK4D expression was shown to be associated with a poor prognosis by analyzing clinicopathological features. In conclusion, we found that loss of p19INK4D protein was frequent in HCC, especially in poorly differentiated HCC, suggesting that p19INK4D may play a role in the differentiation of HCC. Furthermore, expression of p19INK4D may be an effective predictor of clinical behavior in HCC, and therefore, a new prognostic marker for HCC.

Ha L, Ponnamperuma RM, Jay S, et al.
Dysregulated ΔNp63α inhibits expression of Ink4a/arf, blocks senescence, and promotes malignant conversion of keratinocytes.
PLoS One. 2011; 6(7):e21877 [PubMed] Free Access to Full Article Related Publications
p63 is critical for squamous epithelial development, and elevated levels of the ΔNp63α isoform are seen in squamous cell cancers of various organ sites. However, significant controversy exists regarding the role of p63 isoforms as oncoproteins or tumor suppressors. Here, lentiviruses were developed to drive long-term overexpression of ΔNp63α in primary keratinocytes. Elevated levels of ΔNp63α in vitro promote long-term survival and block both replicative and oncogene-induced senescence in primary keratinocytes, as evidenced by the expression of SA-β-gal and the presence of nuclear foci of heterochromatin protein 1γ. The contribution of ΔNp63α to cancer development was assessed using an in vivo grafting model of experimental skin tumorigenesis that allows distinction between benign and malignant tumors. Grafted lenti-ΔNp63α keratinocytes do not form tumors, whereas lenti-GFP/v-ras(Ha) keratinocytes develop well-differentiated papillomas. Lenti-ΔNp63α/v-ras(Ha) keratinocytes form undifferentiated carcinomas. The average volume of lenti-ΔNp63α/v-ras(Ha) tumors was significantly higher than those in the lenti-GFP/v-ras(Ha) group, consistent with increased BrdU incorporation detected by immunohistochemistry. The block in oncogene-induced senescence corresponds to sustained levels of E2F1 and phosphorylated AKT, and is associated with loss of induction of p16(ink4a)/p19(arf). The relevance of p16(ink4a)/p19(arf) loss was demonstrated in grafting studies of p19(arf)-null keratinocytes, which develop malignant carcinomas in the presence of v-ras(Ha) similar to those arising in wildtype keratinocytes that express lenti-ΔNp63α and v-ras(Ha). Our findings establish that ΔNp63α has oncogenic activity and its overexpression in human squamous cell carcinomas contributes to the malignant phenotype, and implicate its ability to regulate p16(ink4a)/p19(arf) in the process.

Yu JH, Zhu BM, Wickre M, et al.
The transcription factors signal transducer and activator of transcription 5A (STAT5A) and STAT5B negatively regulate cell proliferation through the activation of cyclin-dependent kinase inhibitor 2b (Cdkn2b) and Cdkn1a expression.
Hepatology. 2010; 52(5):1808-18 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: Although the cytokine-inducible transcription factor signal transducer and activator of transcription 5 (STAT5) promotes proliferation of a wide range of cell types, there are cell-specific and context-specific cases in which loss of STAT5 results in enhanced cell proliferation. Here, we report that loss of STAT5 from mouse embryonic fibroblasts (MEFs) leads to enhanced proliferation, which was linked to reduced levels of the cell cycle inhibitors p15(INK4B) and p21(CIP1). We further demonstrate that growth hormone, through the transcription factor STAT5, enhances expression of the Cdkn2b (cyclin-dependent kinase inhibitor 2B) gene and that STAT5A binds to interferon-gamma-activated sequence sites within the promoter. We recently demonstrated that ablation of STAT5 from liver results in hepatocellular carcinoma upon CCl₄ treatment. We now establish that STAT5, like in MEFs, activates expression of the Cdkn2b gene in liver tissue. Loss of STAT5 led to diminished p15(INK4B) and increased hepatocyte proliferation.
CONCLUSION: This study for the first time demonstrates that cytokines, through STAT5, induce the expression of a key cell cycle inhibitor. These experiments therefore shed mechanistic light on the context-specific role of STAT5 as tumor suppressor.

Jankovic M, Robbiani DF, Dorsett Y, et al.
Role of the translocation partner in protection against AID-dependent chromosomal translocations.
Proc Natl Acad Sci U S A. 2010; 107(1):187-92 [PubMed] Free Access to Full Article Related Publications
Chromosome translocations between Ig (Ig) and non-Ig genes are frequently associated with B-cell lymphomas in humans and mice. The best characterized of these is c-myc/IgH translocation, which is associated with Burkitt's lymphoma. These translocations are caused by activation-induced cytidine deaminase (AID), which produces double-strand DNA breaks in both genes. c-myc/IgH translocations are rare events, in part because ATM, p53, and p19 actively suppress them. To further define the mechanism of protection against the accumulation of cells that bear c-myc/IgH translocation, we assayed B cells from mice that carry mutations in cell-cycle and apoptosis regulator proteins that act downstream of p53. We find that PUMA, Bim, and PKCdelta are required for protection against c-myc/IgH translocation, whereas Bcl-XL and BAFF enhance c-myc/IgH translocation. Whether these effects are general or specific to c-myc/IgH translocation and whether AID produces dsDNA breaks in genes other than c-myc and Ig is not known. To examine these questions, we developed an assay for translocation between IgH and Igbeta, both of which are somatically mutated by AID. Igbeta/IgH, like c-myc/IgH translocations, are AID-dependent, and AID is responsible for lesions on IgH and the non-IgH translocation partners. However, ATM, p53, and p19 do not protect against Igbeta/IgH translocations. Instead, B cells are protected against Igbeta/IgH translocations by a BAFF- and PKCdelta-dependent pathway. We conclude that AID-induced double-strand breaks in non-Ig genes other than c-myc lead to their translocation, and that at least two nonoverlapping pathways protect against translocations in primary B cells.

Rice KL, Hormaeche I, Doulatov S, et al.
Comprehensive genomic screens identify a role for PLZF-RARalpha as a positive regulator of cell proliferation via direct regulation of c-MYC.
Blood. 2009; 114(27):5499-511 [PubMed] Free Access to Full Article Related Publications
The t(11;17)(q23;q21) translocation is associated with a retinoic acid (RA)-insensitive form of acute promyelocytic leukemia (APL), involving the production of reciprocal fusion proteins, promyelocytic leukemia zinc finger-retinoic acid receptor alpha (PLZF-RARalpha) and RARalpha-PLZF. Using a combination of chromatin immunoprecipitation promotor arrays (ChIP-chip) and gene expression profiling, we identify novel, direct target genes of PLZF-RARalpha that tend to be repressed in APL compared with other myeloid leukemias, supporting the role of PLZF-RARalpha as an aberrant repressor in APL. In primary murine hematopoietic progenitors, PLZF-RARalpha promotes cell growth, and represses Dusp6 and Cdkn2d, while inducing c-Myc expression, consistent with its role in leukemogenesis. PLZF-RARalpha binds to a region of the c-MYC promoter overlapping a functional PLZF site and antagonizes PLZF-mediated repression, suggesting that PLZF-RARalpha may act as a dominant-negative version of PLZF by affecting the regulation of shared targets. RA induced the differentiation of PLZF-RARalpha-transformed murine hematopoietic cells and reduced the frequency of clonogenic progenitors, concomitant with c-Myc down-regulation. Surviving RA-treated cells retained the ability to be replated and this was associated with sustained c-Myc expression and repression of Dusp6, suggesting a role for these genes in maintaining a self-renewal pathway triggered by PLZF-RARalpha.

Zhang W, Zeng Z, Zhou Y, et al.
Identification of aberrant cell cycle regulation in Epstein-Barr virus-associated nasopharyngeal carcinoma by cDNA microarray and gene set enrichment analysis.
Acta Biochim Biophys Sin (Shanghai). 2009; 41(5):414-28 [PubMed] Related Publications
Previous studies have revealed that Epstein-Barr virus (EBV) was closely associated with nasopharyngeal carcinoma (NPC). This study aimed to characterize the global pathways affected in the EBV-associated NPC. Combined with microdissection, gene expression profiles in 22 NPCs and 10 non-tumor nasopharyngeal epithelial (NPE) tissue samples were analyzed. All NPC specimens served in the microarray analysis were positive for EBV, as judged by identification of the expression of EBV nuclear antigen 1 (EBNA1). Through gene set enrichment analysis (GSEA), we found that cell cycle pathway was the most disregulated pathway in NPC (P=0.000, false discovery rate q-value=0.007), which included some aberrant expressed components. We first found that overexpression of CDK4, cyclin D1, and Rb proteins, and loss of expression of proteins p16, p27, and p19 were statistically significant in NPC tissues compared with non-cancerous NPE (P<0.05) by real-time RT-PCR and tissue microarray. EBV-encoded small RNA-1 (EBER-1) hybridization signals in the NPC showed significant associations with the overexpression of Rb (P=0.000), cyclin D1 (P=0.000), CDK4 (P=0.000), and the loss of expression of p16 proteins (P=0.039). In the final logistic regression analysis model, EBER-1 and abnormal expression of p16, Rb, cyclin D1, and E2F6 were independent contributions to nasopharyngeal carcinogenesis. Through survival analysis, only cyclin D1 could predict the prognosis of NPC patients. These results suggested that cell cycle pathway was the most disregulated pathway in the EBV-associated NPC, and EBER-1 was closely associated with p16, CDK4, cyclin D1, and Rb.cyclin D1 could be the prognosis biomarker for NPC.

Zhang S, Tang Q, Xu F, et al.
RhoA regulates G1-S progression of gastric cancer cells by modulation of multiple INK4 family tumor suppressors.
Mol Cancer Res. 2009; 7(4):570-80 [PubMed] Related Publications
RhoA, a member of the Rho GTPase family, has been extensively studied in the regulation of cytoskeletal dynamics, gene transcription, cell cycle progression, and cell transformation. Overexpression of RhoA is found in many malignancies and elevated RhoA activity is associated with proliferation phenotypes of cancer cells. We reported previously that RhoA was hyperactivated in gastric cancer tissues and suppression of RhoA activity could partially reverse the proliferation phenotype of gastric cancer cells, but the underlying mechanism has yet to be elucidated. It has been reported that RhoA activation is crucial for the cell cycle G(1)-S procession through the regulation of Cip/Kip family tumor suppressors in benign cell lines. In this study, we found that selective suppression of RhoA or its effectors mammalian Diaphanous 1 and Rho kinase (ROCK) by small interfering RNA and a pharmacologic inhibitor effectively inhibited proliferation and cell cycle G(1)-S transition in gastric cancer lines. Down-regulation of RhoA-mammalian Diaphanous 1 pathway, but not RhoA-ROCK pathway, caused an increase in the expression of p21(Waf1/Cip1) and p27(Kip1), which are coupled with reduced expression and activity of CDK2 and a cytoplasmic mislocalization of p27(Kip1). Suppression of RhoA-ROCK pathway, on the other hand, resulted in an accumulation of p15(INK4b), p16(INK4a), p18(INK4c), and p19(INK4d), leading to reduced expression and activities of CDK4 and CDK6. Thus, RhoA may use two distinct effector pathways in regulating the G(1)-S progression of gastric cancer cells.

Rao SS, O'Neil J, Liberator CD, et al.
Inhibition of NOTCH signaling by gamma secretase inhibitor engages the RB pathway and elicits cell cycle exit in T-cell acute lymphoblastic leukemia cells.
Cancer Res. 2009; 69(7):3060-8 [PubMed] Related Publications
NOTCH signaling is deregulated in the majority of T-cell acute lymphoblastic leukemias (T-ALL) as a result of activating mutations in NOTCH1. Gamma secretase inhibitors (GSI) block proteolytic activation of NOTCH receptors and may provide a targeted therapy for T-ALL. We have investigated the mechanisms of GSI sensitivity across a panel of T-ALL cell lines, yielding an approach for patient stratification based on pathway activity and also providing a rational combination strategy for enhanced response to GSI. Whereas the NOTCH1 mutation status does not serve as a predictor of GSI sensitivity, a gene expression signature of NOTCH pathway activity does correlate with response, and may be useful in the selection of patients more likely to respond to GSI. Furthermore, inhibition of the NOTCH pathway activity signature correlates with the induction of the cyclin-dependent kinase inhibitors CDKN2D (p19(INK4d)) and CDKN1B (p27(Kip1)), leading to derepression of RB and subsequent exit from the cell cycle. Consistent with this evidence of cell cycle exit, short-term exposure of GSI resulted in sustained molecular and phenotypic effects after withdrawal of the compound. Combination treatment with GSI and a small molecule inhibitor of CDK4 produced synergistic growth inhibition, providing evidence that GSI engagement of the CDK4/RB pathway is an important mechanism of GSI action and supports further investigation of this combination for improved efficacy in treating T-ALL.

Ceruti JM, Scassa ME, Marazita MC, et al.
Transcriptional upregulation of p19INK4d upon diverse genotoxic stress is critical for optimal DNA damage response.
Int J Biochem Cell Biol. 2009; 41(6):1344-53 [PubMed] Related Publications
p19INK4d promotes survival of several cell lines after UV irradiation due to enhanced DNA repair, independently of CDK4 inhibition. To further understand the action of p19INK4d in the cellular response to DNA damage, we aimed to elucidate whether this novel regulator plays a role only in mechanisms triggered by UV or participates in diverse mechanisms initiated by different genotoxics. We found that p19INK4d is induced in cells injured with cisplatin or beta-amyloid peptide as robustly as with UV. The mentioned genotoxics transcriptionally activate p19INK4d expression as demonstrated by run-on assay without influencing its mRNA stability and with partial requirement of protein synthesis. It is not currently known whether DNA damage-inducible genes are turned on by the DNA damage itself or by the consequences of that damage. Experiments carried out in cells transfected with distinct damaged DNA structures revealed that the damage itself is not responsible for the observed up-regulation. It is also not known whether the increased expression of DNA-damage-inducible genes is related to immediate protective responses such as DNA repair or to more delayed responses such as cell cycle arrest or apoptosis. We found that ectopic expression of p19INK4d improves DNA repair ability and protects neuroblastoma cells from apoptosis caused by cisplatin or beta-amyloid peptide. Using clonal cell lines where p19INK4d levels can be modified at will, we show that p19INK4d expression correlates with increased survival and clonogenicity. The results presented here, prompted us to suggest that p19INK4d displays an important role in an early stage of cellular DNA damage response.

Michael LE, Westerman BA, Ermilov AN, et al.
Bmi1 is required for Hedgehog pathway-driven medulloblastoma expansion.
Neoplasia. 2008; 10(12):1343-9, 5p following 1349 [PubMed] Free Access to Full Article Related Publications
Inappropriate Hedgehog (Hh) signaling underlies development of a subset of medulloblastomas, and tumors with elevated HH signaling activity express the stem cell self-renewal gene BMI1. To test whether Bmi1 is required for Hh-driven medulloblastoma development, we varied Bmi1 gene dosage in transgenic mice expressing an oncogenic Hh effector, SmoA1, driven by a glial fibrillary acidic protein (GFAP) promoter. Whereas 100% of SmoA1; Bmi1(+/+) or SmoA1;Bmi1(+/-) mice examined between postnatal (P) days 14 and 26 had typical medulloblastomas (N = 29), tumors were not detected in any of the SmoA1;Bmi1(-/-) animals examined (N = 6). Instead, small ectopic collections of cells were present in the region of greatest tumor load in SmoA1 animals, suggesting that medulloblastomas were initiated but failed to undergo expansion into frank tumors. Cells within these Bmi1(-/-) lesions expressed SmoA1 but were largely nonproliferative, in contrast to cells in Bmi1(+/+) tumors (6.2% vs 81.9% PCNA-positive, respectively). Ectopic cells were negative for the progenitor marker nestin, strongly GFAP-positive, and highly apoptotic, relative to Bmi1(+/+) tumor cells (29.6% vs 6.3% TUNEL-positive). The alterations in proliferation and apoptosis in SmoA1;Bmi1(-/-) ectopic cells are associated with reduced levels of Cyclin D1 and elevated expression of cyclin-dependent kinase inhibitor p19(Arf), two inversely regulated downstream targets of Bmi1. These data provide the first demonstration that Bmi1 is required for spontaneous de novo development of a solid tumor arising in the brain, suggest a crucial role for Bmi1-dependent, nestin-expressing progenitor cells in medulloblastoma expansion, and implicate Bmi1 as a key factor required for Hh pathway-driven tumorigenesis.

Gedlicka C, Hager G, Weissenböck M, et al.
1,25(OH)2Vitamin D3 induces elevated expression of the cell cycle inhibitor p18 in a squamous cell carcinoma cell line of the head and neck.
J Oral Pathol Med. 2006; 35(8):472-8 [PubMed] Related Publications
BACKGROUND: 1Alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2) Vitamin D(3)] induces growth inhibition in squamous cell carcinoma (SCC) cell lines of the head and neck by arresting the cells in the G0/G1 phase of the cell cycle, probably due to an enhanced expression of p21, which could be demonstrated in other cell lines (JPPA, SCC9) before. In SCC25, a SCC cell line isolated from tongue, growth inhibition but no overexpression of p21 was detected. The retinoblastoma gene, as a direct target of G1 cyclin-CDK complexes, showed an obvious shift from the hyperphosphorylated to the hypophosphorylated form under 1,25(OH)(2)Vitamin D(3), which indicates that the growth inhibition takes place in the G0/G1 phase. To explore the possible pathway of growth inhibition in SCC25 we investigated other cell cycle inhibitors (p18, p19, p27).
METHODS: Synchronized cells were treated with 1,25(OH)(2)Vitamin D(3) over 96 h. The cell cycle status and expression of cell cycle-regulating proteins was determined by fluorescence-activated cell sorting (FACS) and Western blotting. An overexpression of p18 in 1,25(OH)(2)Vitamin D(3) vs. ethanol-treated cells was determined until 30 h in SCC25. No influence was detectable on the expression of p27 and p19.
CONCLUSION: One mechanism by which 1,25(OH)(2)Vitamin D(3) controls cell growth might be the upregulation of p21. As p21 was unsusceptible to 1,25(OH)(2)Vitamin D(3) in SCC25, other inhibiting proteins were necessary to be tested. The proven upregulation of p18 seems to be the responsible step for growth inhibition of 1,25(OH)(2)Vitamin D(3) in SCC25.

Tavera-Mendoza LE, Wang TT, White JH
p19INK4D and cell death.
Cell Cycle. 2006; 5(6):596-8 [PubMed] Related Publications
INK4 proteins are members of a family of cyclin-dependent kinase (CDK) inhibitors that function in G(1) to block the activity of CDKs 4 and 6. While they share clear structural similarities, numerous studies have shown that INK4 proteins differ in their expression patterns during development and in the adult, and have differing roles in tumor suppression. A recent study from our laboratory showed that expression of the gene encoding p19(INK4D) is induced by the hormonal form of vitamin D(3) and by retinoids, both of which signal through related nuclear receptor transcription factors. Although vitamin D(3) and retinoids have distinct developmental and physiological functions, both regulate the cell cycle and have been shown to have chemopreventive effects in a range of studies. Induction of p19(INK4D) expression contributed to cell cycle arrest by both ligands. However, knockdown of p19(INK4D) rendered cells sensitive to autophagic cell death, a remarkable phenotype given the hyperproliferative responses to loss of other INK4 proteins. We discuss the relevance of our studies and recent findings of others to the cell death observed in p19(INK4D)-deficient animals and to a possible role for p19(INK4D) induction in chemoprevention.

Riggi N, Cironi L, Provero P, et al.
Development of Ewing's sarcoma from primary bone marrow-derived mesenchymal progenitor cells.
Cancer Res. 2005; 65(24):11459-68 [PubMed] Related Publications
Ewing's sarcoma is a member of Ewing's family tumors (EFTs) and the second most common solid bone and soft tissue malignancy of children and young adults. It is associated in 85% of cases with the t(11;22)(q24:q12) chromosomal translocation that generates fusion of the 5' segment of the EWS gene with the 3' segment of the ETS family gene FLI-1. The EWS-FLI-1 fusion protein behaves as an aberrant transcriptional activator and is believed to contribute to EFT development. However, EWS-FLI-1 induces growth arrest and apoptosis in normal fibroblasts, and primary cells that are permissive for its putative oncogenic properties have not been discovered, hampering basic understanding of EFT biology. Here, we show that EWS-FLI-1 alone can transform primary bone marrow-derived mesenchymal progenitor cells and generate tumors that display hallmarks of Ewing's sarcoma, including a small round cell phenotype, expression of EFT-associated markers, insulin like growth factor-I dependence, and induction or repression of numerous EWS-FLI-1 target genes. These observations provide the first identification of candidate primary cells from which EFTs originate and suggest that EWS-FLI-1 expression may constitute the initiating event in EFT pathogenesis.

Thompson MA, Stumph J, Henrickson SE, et al.
Differential gene expression in anaplastic lymphoma kinase-positive and anaplastic lymphoma kinase-negative anaplastic large cell lymphomas.
Hum Pathol. 2005; 36(5):494-504 [PubMed] Related Publications
Anaplastic large cell lymphoma (ALCL) is an aggressive large T- or null-cell lymphoma. Most ALCLs arising in children and young adults express a constitutively active receptor tyrosine kinase, anaplastic lymphoma kinase (ALK). Anaplastic large cell lymphomas lacking ALK are clinically heterogeneous and their pathogenesis is unknown. This study is the first complementary DNA (cDNA) microarray analysis using RNA extracted from tumor tissue (7 ALK+ ALCLs and 7 ALK- ALCLs) to identify genes differentially expressed or shared between the ALK+ and ALK- tumors. Unsupervised hierarchical clustering using the top 11 most statistically significant discriminator cDNAs correctly grouped all ALK+ and ALK- tumors. Hierarchical clustering analysis using the 44 cDNAs with the greatest differential expression between ALK+ and ALK- RNAs grouped 6 of 7 ALK+ ALCLs together and 1 ALK+ ALCL with the ALK- group. In general, ALK+ tumors overexpress genes encoding signal transduction molecules (SYK , LYN , CDC37) and underexpress transcription factor genes (including HOXC6 and HOX A3 ) compared with the ALK- group. Cyclin D3 was overexpressed in the ALK+ group and the cell cycle inhibitor p19INK4D was decreased in the ALK- group, suggesting different mechanisms of promoting G 1 /S transition. Both groups had similar proliferation rates. Genes highly expressed in both ALK- and ALK+ ALCLs included kinases (LCK, protein kinase C, vav2, and NKIAMRE) and antiapoptotic molecules, suggesting possible common pathogenetic mechanisms as well.

Ceruti JM, Scassa ME, Fló JM, et al.
Induction of p19INK4d in response to ultraviolet light improves DNA repair and confers resistance to apoptosis in neuroblastoma cells.
Oncogene. 2005; 24(25):4065-80 [PubMed] Related Publications
The genetic instability driving tumorigenesis is fueled by DNA damage and by errors made by the DNA replication. Upon DNA damage the cell organizes an integrated response not only by the classical DNA repair mechanisms but also involving mechanisms of replication, transcription, chromatin structure dynamics, cell cycle progression, and apoptosis. In the present study, we investigated the role of p19INK4d in the response driven by neuroblastoma cells against DNA injury caused by UV irradiation. We show that p19INK4d is the only INK4 protein whose expression is induced by UV light in neuroblastoma cells. Furthermore, p19INK4d translocation from cytoplasm to nucleus is observed after UV irradiation. Ectopic expression of p19INK4d clearly reduces the UV-induced apoptosis as well as enhances the cellular ability to repair the damaged DNA. It is clearly shown that DNA repair is the main target of p19INK4d effect and that diminished apoptosis is a downstream event. Importantly, experiments performed with CDK4 mutants suggest that these p19INK4d effects would be independent of its role as a cell cycle checkpoint gene. The results presented herein uncover a new role of p19INK4d as regulator of DNA-damage-induced apoptosis and suggest that it protects cells from undergoing apoptosis by allowing a more efficient DNA repair. We propose that, in addition to its role as cell cycle inhibitor, p19INK4d is involved in maintenance of DNA integrity and, therefore, would contribute to cancer prevention.

Yoshida T, Iwamoto T, Adachi K, et al.
Functional analysis of the effect of forced activation of STAT3 on M1 mouse leukemia cells.
Int J Mol Med. 2005; 15(2):269-75 [PubMed] Related Publications
M1 mouse myeloid leukemia cells exhibit growth arrest and differentiation to monocytes/macrophages in response to leukemia inhibitory factor (LIF) stimulation. Although recent studies have demonstrated that STAT3 plays a central role in this process, it is unknown whether STAT3 activation alone is sufficient. To address this issue, we have established M1/STAT3ER cells, where STAT3 is selectively activated by 4-hydroxytamoxifen (4HT). 4HT stimulation did not have any effect on growth and morphology of M1/ STAT3ER cells, and did not induce the down-regulation of mRNA of c-myc and c-myb, which is necessary for M1 cell differentiation. On the other hand, mRNA of jun-B, IRF1 and p19 was increased by 4HT. DNA precipitation assay indicated that both stimulation of LIF and 4HT similarly activated STAT3ER. Introduction of a constitutive active MAP kinase kinase (MEK1) into M1/STAT3ER cells did not induce differentiation either. Together, our present data suggest that signaling other than the activation of STAT3 and MEK1 may be necessary for M1 cell-growth arrest and differentiation, while a set of early genes of LIF are induced by only STAT3 activation.

Takita J, Ishii M, Tsutsumi S, et al.
Gene expression profiling and identification of novel prognostic marker genes in neuroblastoma.
Genes Chromosomes Cancer. 2004; 40(2):120-32 [PubMed] Related Publications
To investigate the various genetic characteristics of and differences between early- and advanced-stage neuroblastoma (NB) and to identify candidate genes involved in NB progression, we performed DNA microarray analysis on 20 primary tumors. Two-way clustering analysis based on the expression pattern of approximately 500 of 1,700 genes revealed genetic subgroups in these NB tumors. Although 9 of the 13 early-stage tumors (69%) and 4 of the 6 advanced-stage tumors (67%) were classified as being in the same cluster, the remaining tumors showed different expression profiles. This indicates that both the early- and advanced-stage tumors were heterogeneous. Based on the microarray data, we identified the BIRC, CDKN2D, and SMARCD3 genes as those that are predominantly expressed in either the early or the advanced stage of NB. These genes have been reported to be associated with apoptosis, cell cycles, and the transcriptional activator, respectively. To better assess the prognostic value of the expression of these genes in NB, real-time polymerase chain reaction was carried out on 50 primary tumors. The expression of both the BIRC3 and CDKN2D genes was significantly higher in the early-stage group than in the advanced-stage group (P = 0.002 and 0.003, respectively), whereas the expression of the SMARCD3 gene was significantly reduced in the early-stage group (P = 0.02). Therefore, the BIRC, CDKN2D, and SMARCD3 genes are possible candidates for being novel prognostic markers for NB.

Bartkova J, Rajpert-De Meyts E, Skakkebaek NE, et al.
Deregulation of the G1/S-phase control in human testicular germ cell tumours.
APMIS. 2003; 111(1):252-65; discussion 265-6 [PubMed] Related Publications
Deregulated cell cycle and defective genome-integrity checkpoints are among the hallmarks of cancer. Here we summarize our recent studies of key components of the GI/S machinery in normal human spermatogenesis, and their abnormalities in testicular germ cell tumours (TGCTs), with special emphasis on carcinoma in situ lesions (CIS). Our combined immunohistochemical and immunoblotting analyses of normal human adult and fetal testes, CIS, seminomas, embryonal carcinomas, and teratomas, revealed an 'unorthodox' spectrum of defects within the so-called RB pathway in TGCTs. The early aberrations included lack of expression of the retinoblastoma tumour suppressor (pRB) and the CDK inhibitor pl9ink4d, and overexpression of cyclin D2. Progression from CIS to invasive TGCTswas associated with loss of another two CDK inhibitors and tumour suppressors: pl6ink4a and pl8ink4c. We also found the lack of pRB and pl9ink4d in fetal gonocytes, the candidate target cell for all types of TGCTs. These findings, together with the status of the Chk2-p53 DNA-integrity checkpoint, are considered in relation to the origin, biology and pathogenesis of TGCTs, and potential implications of the GI/S defects for the curability of these tumours.

Komata T, Kanzawa T, Takeuchi H, et al.
Antitumour effect of cyclin-dependent kinase inhibitors (p16(INK4A), p18(INK4C), p19(INK4D), p21(WAF1/CIP1) and p27(KIP1)) on malignant glioma cells.
Br J Cancer. 2003; 88(8):1277-80 [PubMed] Free Access to Full Article Related Publications
Cyclin-dependent kinase inhibitors (CDKIs) are considered as novel anticancer agents because of their ability to induce growth arrest or apoptosis in tumour cells. It has not yet been fully determined, however, which CDKI is the best candidate for the treatment of malignant gliomas and whether normal brain tissues are affected by CDKI expression. Using recombinant adenoviral vectors that express CDKIs (p16(INK4A), p18(INK4C), p19(INK4D), p21(WAF1/CIP1) and p27(KIP1)), we compared the antitumour effect of CDKIs on malignant glioma cell lines (A172, GB-1, T98G, U87-MG, U251-MG and U373-MG). p27(KIP1) showed higher ability to suppress the growth of all tumour cells tested than other CDKIs. Interestingly, overexpression of p27(KIP1) induced autophagic cell death, but not apoptosis in tumour cells. On the other hand, p27(KIP1) overexpression did not inhibit the viability of cultured astrocytes (RNB) nor induced autophagy. Overall, our findings suggest that gene transfer of p27(KIP1) may be a promising approach for the therapy of malignant gliomas.

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