Gene Summary

Gene:GJB2; gap junction protein, beta 2, 26kDa
Summary:This gene encodes a member of the gap junction protein family. The gap junctions were first characterized by electron microscopy as regionally specialized structures on plasma membranes of contacting adherent cells. These structures were shown to consist of cell-to-cell channels that facilitate the transfer of ions and small molecules between cells. The gap junction proteins, also known as connexins, purified from fractions of enriched gap junctions from different tissues differ. According to sequence similarities at the nucleotide and amino acid levels, the gap junction proteins are divided into two categories, alpha and beta. Mutations in this gene are responsible for as much as 50% of pre-lingual, recessive deafness. [provided by RefSeq, Oct 2008]
Databases:OMIM, VEGA, HGNC, Ensembl, GeneCard, Gene
Protein:gap junction beta-2 protein
Source:NCBIAccessed: 26 August, 2015


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 26 August 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Up-Regulation
  • Promoter Regions
  • Esophageal Cancer
  • Microdissection
  • Lung Cancer
  • Porokeratosis
  • Dermatologic Agents
  • serum-glucocorticoid regulated kinase
  • High-Throughput Nucleotide Sequencing
  • Ichthyosis
  • Mutation
  • Young Adult
  • Immediate-Early Proteins
  • Chromosome Deletion
  • Chromosomal Proteins, Non-Histone
  • Skin Cancer
  • Immunohistochemistry
  • Chromosome 13
  • Dapsone
  • Genetic Markers
  • Connexins
  • Southern Blotting
  • Colorectal Cancer
  • Squamous Cell Carcinoma
  • Microsatellite Repeats
  • DNA Methylation
  • Nevus
  • retinoic acid binding protein II, cellular
  • Histones
  • Keratitis
  • Deafness
  • Cell Communication
  • Drug Therapy, Combination
  • Multiple Primary Neoplasms
  • DNA Mutational Analysis
  • CpG Islands
  • Breast Cancer
  • Oligonucleotide Array Sequence Analysis
  • Tumor Markers
  • Selenomethionine
  • Gene Expression Profiling
Tag cloud generated 26 August, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

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: GJB2 (cancer-related)

Sirnes S, Lind GE, Bruun J, et al.
Connexins in colorectal cancer pathogenesis.
Int J Cancer. 2015; 137(1):1-11 [PubMed] Related Publications
The connexins constitute a family of integral membrane proteins that form channels between adjacent cells. These channels are assembled in plasma membrane domains known as gap junctions and enable cells to directly exchange ions and small molecules. Intercellular communication via gap junctions plays important roles in regulating cell growth and differentiation and in maintaining tissue homeostasis. This type of cell communication is often impaired during cancer development, and several members of the connexin protein family have been shown to act as tumor suppressors. Emerging evidence suggests that the connexin protein family has important roles in colorectal cancer development. In the normal colonic epithelial tissue, three connexin isoforms, connexin 26 (Cx26), Cx32 and Cx43, have been shown to be expressed at the protein level. Colorectal cancer development is associated with loss of connexin expression or relocalization of connexins from the plasma membrane to intracellular compartments. Downregulation of connexins in colorectal carcinomas at the transcriptional level involves cancer-specific promoter hypermethylation. Recent studies suggest that Cx43 may constrain growth of colon cancer cells by interfering with the Wnt/β-catenin pathway. There is also increasing evidence that the connexins may have potential as prognostic markers in colorectal cancer. This review discusses the role of connexins in colorectal cancer pathogenesis, as well as their potential as prognostic markers and targets in the prevention and treatment of the disease.

Han SS, Kim WJ, Hong Y, et al.
RNA sequencing identifies novel markers of non-small cell lung cancer.
Lung Cancer. 2014; 84(3):229-35 [PubMed] Related Publications
INTRODUCTION: The development of reliable gene expression profiling technology increasingly impacts our understanding of lung cancer biology. Here, we used RNA sequencing (RNA-Seq) to compare the transcriptomes of non-small cell lung cancer (NSCLC) and normal lung tissues and to investigate expression in lung cancer tissues.
METHODS: We enrolled 88 male patients (mean age, 61.2 years) with NSCLC. RNA-Seq was performed on 88 pairs of NSCLC tumor tissue and non-tumor tissue from 54 patients with adenocarcinoma and 34 patients with squamous cell carcinoma. Immunohistochemistry was performed to validate differential candidate gene expression in a different NSCLC group.
RESULTS: RNA-Seq produced 25.41 × 10(6) (± 8.90 × 10(6)) reads in NSCLC tissues and 24.70×10(6) (± 4.70 × 10(6)) reads in normal lung tissues [mean (± standard deviation)]. Among the genes expressed in both tissues, 335 were upregulated and 728 were downregulated ≥ 2-fold (p < 0.001). Four upregulated genes - CBX3, GJB2, CRABP2, and DSP - not previously reported in lung cancer were studied further. Their altered expression was verified by immunohistochemistry in a different set of NSCLC tissues (n = 154). CBX3 was positive in 90.3% (139 cases) of the samples; GJB2, in 22.7% (35 cases); CRABP2, in 72.1% (111 cases); and DSP, in 17.5% (27 cases). The positive rate of CRABP2 was higher in adenocarcinoma than squamous cell carcinoma (p < 0.01).
CONCLUSIONS: CBX3 and CRABP2 expression was markedly increased in lung cancer tissues and especially CRABP2 may be promising candidate genes in lung adenocarcinoma.

Li JY, Berger MF, Marghoob A, et al.
Combined melanocytic and sweat gland neoplasm: cell subsets harbor an identical HRAS mutation in phacomatosis pigmentokeratotica.
J Cutan Pathol. 2014; 41(8):663-71 [PubMed] Related Publications
Phacomatosis pigmentokeratotica (PPK) is characterized by the co-existence of epidermal nevi and large segmental speckled lentiginous nevi of the papulosa type. PPK, previously explained as 'twin spot' mosaicism due to the postzygotic crossing-over of two homozygous recessive mutations, has recently been shown to derive from one postzygotic activating RAS mutation. Epidermal nevi, including those in PPK, are known to give rise to neoplasms such as trichoblastoma and basal cell carcinoma. Within speckled lentiginous nevi, Spitz nevi and melanoma have been well documented. We report a case of PPK with a combined melanocytic and adnexal neoplasm presenting where the nevi conjoined. Using next-generation sequencing techniques, we were able to identify the same HRAS G13R mutation within both components of the tumor, and to show the absence of additional mutated modifier genes in a panel of 300 cancer-related genes. Given the genetic findings in this rare tumor-type, we suggest that this case may be used as a model for understanding the development of biphenotypic neoplasia or intratumoral heterogeneity in some cases.

Xiao J, Zhang G, Qiu P, et al.
Tanshinone IIA increases the bystander effect of herpes simplex virus thymidine kinase/ganciclovir gene therapy via enhanced gap junctional intercellular communication.
PLoS One. 2013; 8(7):e67662 [PubMed] Free Access to Full Article Related Publications
The bystander effect is an intriguing phenomenon by which adjacent cells become sensitized to drug treatment during gene therapy with herpes simplex virus thymidine kinase/ganciclovir (HSV-tk/GCV). This effect is reported to be mediated by gap junctional intercellular communication (GJIC), and therefore, we postulated that upregulation of genes that facilitate GJIC may enhance the HSV-tk/GCV bystander effect. Previous findings have shown Tanshinone IIA (Tan IIA), a chemical substance derived from a Chinese medicine herb, promotes the upregulation of the connexins Cx26 and Cx43 in B16 cells. Because gap junctions are formed by connexins, we hypothesized that Tan IIA might increase GJIC. Our results show that Tan IIA increased GJIC in B16 melanoma cells, leading to more efficient GCV-induced bystander killing in cells stably expressing HSV-tk. Additionally, in vivo experiments demonstrated that tumors in mice with 10% HSV-tk positive B16 cells and 90% wild-type B16 cells became smaller following treatment with the combination of GCV and Tan IIA as compared to GCV or Tan IIA alone. These data demonstrate that Tan IIA can augment the bystander effect of HSV-tk/GCV system through increased gap junction coupling, which adds strength to the promising strategy that develops connexins inducer to potentiate the effects of suicide gene therapy.

Coggshall K, Farsani T, Ruben B, et al.
Keratitis, ichthyosis, and deafness syndrome: a review of infectious and neoplastic complications.
J Am Acad Dermatol. 2013; 69(1):127-34 [PubMed] Related Publications
Keratitis, ichthyosis, and deafness (KID) syndrome is a rare genodermatosis associated with mutations in the connexin 26 gene. Although characterized by this clinical triad, KID syndrome predisposes to a heterogeneous spectrum of cutaneous manifestations and complications, both infectious and neoplastic in nature. Chronic mucocutaneous candidiasis and/or superinfection of skin lesions commonly occur and warrant aggressive therapeutic intervention. Benign neoplasms, namely trichilemmal tumors, have also been reported and can herald malignant growth and invasive disease. Squamous cell carcinoma of both mucosa and skin, especially acral sites, occurs in approximately 15% of patients. The pathogenesis of KID syndrome can be at least partially explained by the role of connexin 26 in intercellular communication and carcinogenesis, but the precise mechanism of disease remains unclear. Treatment strategies, which have ranged from antifungals and antibiotics to systemic retinoids, pose an ongoing challenge given the spectrum of disease. A review of the literature, with a particular focus on infection and malignancy associated with KID syndrome, and updates on the pathogenesis of disease, is discussed.

Groesser L, Herschberger E, Sagrera A, et al.
Phacomatosis pigmentokeratotica is caused by a postzygotic HRAS mutation in a multipotent progenitor cell.
J Invest Dermatol. 2013; 133(8):1998-2003 [PubMed] Related Publications
Phacomatosis pigmentokeratotica (PPK) is a rare epidermal nevus syndrome characterized by the co-occurrence of a sebaceous nevus and a speckled lentiginous nevus. The coexistence of an epidermal and a melanocytic nevus has been explained by two homozygous recessive mutations, according to the twin spot hypothesis, of which PPK has become a putative paradigm in humans. However, the underlying gene mutations remained unknown. Multiple tissues of six patients with PPK were analyzed for the presence of RAS, FGFR3, PIK3CA, and BRAF mutations using SNaPshot assays and Sanger sequencing. We identified a heterozygous HRAS c.37G>C (p.Gly13Arg) mutation in four patients and a heterozygous HRAS c.182A>G (p.Gln61Arg) mutation in two patients. In each case, the mutations were present in both the sebaceous and the melanocytic nevus. In the latter lesion, melanocytes were identified to carry the HRAS mutation. Analysis of various nonlesional tissues showed a wild-type sequence of HRAS, consistent with mosaicism. Our data provide no genetic evidence for the previously proposed twin spot hypothesis. In contrast, PPK is best explained by a postzygotic-activating HRAS mutation in a multipotent progenitor cell that gives rise to both a sebaceous and a melanocytic nevus. Therefore, PPK is a mosaic RASopathy.

Stoletov K, Strnadel J, Zardouzian E, et al.
Role of connexins in metastatic breast cancer and melanoma brain colonization.
J Cell Sci. 2013; 126(Pt 4):904-13 [PubMed] Free Access to Full Article Related Publications
Breast cancer and melanoma cells commonly metastasize to the brain using homing mechanisms that are poorly understood. Cancer patients with brain metastases display poor prognosis and survival due to the lack of effective therapeutics and treatment strategies. Recent work using intravital microscopy and preclinical animal models indicates that metastatic cells colonize the brain, specifically in close contact with the existing brain vasculature. However, it is not known how contact with the vascular niche promotes microtumor formation. Here, we investigate the role of connexins in mediating early events in brain colonization using transparent zebrafish and chicken embryo models of brain metastasis. We provide evidence that breast cancer and melanoma cells utilize connexin gap junction proteins (Cx43, Cx26) to initiate brain metastatic lesion formation in association with the vasculature. RNAi depletion of connexins or pharmacological blocking of connexin-mediated cell-cell communication with carbenoxolone inhibited brain colonization by blocking tumor cell extravasation and blood vessel co-option. Activation of the metastatic gene twist in breast cancer cells increased Cx43 protein expression and gap junction communication, leading to increased extravasation, blood vessel co-option and brain colonization. Conversely, inhibiting twist activity reduced Cx43-mediated gap junction coupling and brain colonization. Database analyses of patient histories revealed increased expression of Cx26 and Cx43 in primary melanoma and breast cancer tumors, respectively, which correlated with increased cancer recurrence and metastasis. Together, our data indicate that Cx43 and Cx26 mediate cancer cell metastasis to the brain and suggest that connexins might be exploited therapeutically to benefit cancer patients with metastatic disease.

Bijnsdorp IV, Rozendaal L, van Moorselaar RJ, Geldof AA
A predictive role for noncancerous prostate cells: low connexin-26 expression in radical prostatectomy tissues predicts metastasis.
Br J Cancer. 2012; 107(12):1963-8 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: It is important to identify markers that predict whether prostate cancer will metastasise. The adjacent noncancerous cells (influenced by the tumour cells) may also express potential markers. The objective of this study was to determine the influence of cancer cells on noncancerous cells and to assess the value of the cell-communication protein connexin-26 (Cx26) as a marker to predict the development of metastasis.
METHODS: The effect of conditioned medium (CM) from PrCa cells on in vitro noncancerous cell proliferation, migration and invasion and Cx26 expression was determined. Connexin-26 expression was investigated in prostatectomy tissues from 51 PrCa patients by immunohistochemistry and compared with various clinicopathological parameters.
RESULTS: Proliferation, migration and invasion of noncancerous cells were influenced by CM from the PrCa cell lines. Importantly, a clear relation was found between low Cx26 expression in the noncancerous tissue in prostatectomy sections and the risk of development of metastasis (P<0.0002). Kaplan-Meier analysis showed a relation between low Cx26 expression in noncancerous tissues and time to biochemical recurrence (P=0.0002).
CONCLUSION: Measuring Cx26 expression in the adjacent noncancerous tissues (rather than cancer tissues) of prostatectomy sections could help to identify high-risk patients who may benefit from adjuvant therapy to decrease the risk of metastasis.

Li BX, Yamanaka K, Xiao X
Structure-activity relationship studies of naphthol AS-E and its derivatives as anticancer agents by inhibiting CREB-mediated gene transcription.
Bioorg Med Chem. 2012; 20(23):6811-20 [PubMed] Free Access to Full Article Related Publications
CREB (cyclic AMP-response element binding protein) is a downstream transcription factor of a multitude of signaling pathways emanating from receptor tyrosine kinases or G-protein coupled receptors. CREB is not activated until it is phosphorylated at Ser133 and its subsequent binding to CREB-binding protein (CBP) through kinase-inducible domain (KID) in CREB and KID-interacting (KIX) domain in CBP. Tumor tissues from various organs present higher level of expression and activation of CREB. Thus CREB has been proposed as a promising cancer drug target. We previously described naphthol AS-E (1a) as a small molecule inhibitor of CREB-mediated gene transcription in living cells. Here we report the structure-activity relationship (SAR) studies of 1a by modifying the appendant phenyl ring. All the compounds were evaluated for in vitro inhibition of KIX-KID interaction, cellular inhibition of CREB-mediated gene transcription and inhibition of proliferation of four cancer cell lines (A549, MCF-7, MDA-MB-231 and MDA-MB-468). SAR indicated that a small and electron-withdrawing group was preferred at the para-position for KIX-KID interaction inhibition. Compound 1a was selected for further biological characterization and it was found that 1a down-regulated the expression of endogenous CREB target genes. Expression of a constitutively active CREB mutant, VP16-CREB in MCF-7 cells rendered the cells resistant to 1a, suggesting that CREB was critical in mediating its anticancer activity. Furthermore, 1a was not toxic to normal human cells. Collectively, these data support that 1a represents a structural template for further development into potential cancer therapeutics with a novel mechanism of action.

Pushpavalli SN, Ramaiah MJ, Lavanya A, et al.
Imidazo-benzothiazoles a potent microRNA modulator involved in cell proliferation.
Bioorg Med Chem Lett. 2012; 22(20):6418-24 [PubMed] Related Publications
MicroRNAs are endogenously expressed tiny non-coding RNAs that control gene expression at the post-transcriptional level and regulate processes of cell growth, differentiation, proliferation and apoptosis. Aberrant expression of microRNAs correlates with various cancers. Our experiments demonstrated that imidazo-benzothiazole conjugates caused apoptosis in colon cancer cells by modulating the expression of microRNAs. In vivo study in Drosophila melanogaster has exhibited inhibitory action on bantam microRNA, the homolog of human miR-542-5p that is involved in deciding the cellular cues that regulate the balance between proliferation and apoptosis. The expression of direct targets of bantam such as Hid and HDAC-6 were affected upon compound treatment. Interestingly, these conjugates downregulate the genes involved in microRNA biogenesis such as Drosha, Pasha and Dicer-1. Our findings have elucidated the microRNA inhibitory role of imidazo-benzothiazole conjugates.

Wang Y, Wang Z, Joshi BH, et al.
The tumor suppressor Caliban regulates DNA damage-induced apoptosis through p53-dependent and -independent activity.
Oncogene. 2013; 32(33):3857-66 [PubMed] Related Publications
We previously identified Caliban (Clbn) as the Drosophila homolog of human Serologically defined colon cancer antigen 1 gene and demonstrated that it could function as a tumor suppressor in human non-small-cell lung cancer (NSCLC) cells, although its mode of action was unknown. Herein, we identify roles for Clbn in DNA damage response. We generate clbn knockout flies using homologous recombination and demonstrate that they have a heightened sensitivity to irradiation. We show that normal Clbn function facilitates both p53-dependent and -independent DNA damage-induced apoptosis. Clbn coordinates different apoptosis pathways, showing a two-stage upregulation following DNA damage. Clbn has proapoptotic functions, working with both caspase and the proapoptotic gene Hid. Finally, ecotopic expression of clbn(+) in NSCLC cells suppresses tumor formation in athymic nude mice. We conclude that Caliban is a regulator of DNA damage-induced apoptosis, functioning as a tumor suppressor in both p53-dependent and -independent pathways.

Easton JA, Donnelly S, Kamps MA, et al.
Porokeratotic eccrine nevus may be caused by somatic connexin26 mutations.
J Invest Dermatol. 2012; 132(9):2184-91 [PubMed] Free Access to Full Article Related Publications
Porokeratotic eccrine ostial and dermal duct nevus, or porokeratotic eccrine nevus (PEN), is a hyperkeratotic epidermal nevus. Several cases of widespread involvement have been reported, including one in association with the keratitis-ichthyosis-deafness (KID) syndrome (OMIM #148210), a rare disorder caused by mutations in the GJB2 gene coding for the gap junction protein connexin26 (Cx26). The molecular cause is, as yet, unknown. We have noted that PEN histopathology is shared by KID. The clinical appearance of PEN can resemble that of KID syndrome. Furthermore, a recent report of cutaneous mosaicism for a GJB2 mutation associated with KID describes linear hyperkeratotic skin lesions that might be consistent with PEN. From this, we hypothesized that PEN might be caused by Cx26 mutations associated with KID or similar gap junction disorders. Thus, we analyzed the GJB2 gene in skin samples from two patients referred with generalized PEN. In both, we found GJB2 mutations in the PEN lesions but not in unaffected skin or peripheral blood. One mutation was already known to cause the KID syndrome, and the other had not been previously associated with skin symptoms. We provide extensive functional data to support its pathogenicity. We conclude that PEN may be caused by mosaic GJB2 mutations.

Lazic T, Li Q, Frank M, et al.
Extending the phenotypic spectrum of keratitis-ichthyosis-deafness syndrome: report of a patient with GJB2 (G12R) Connexin 26 mutation and unusual clinical findings.
Pediatr Dermatol. 2012 May-Jun; 29(3):349-57 [PubMed] Related Publications
Keratitis-ichthyosis-deafness (KID) syndrome is a rare ectodermal dysplasia, characterized mainly by the presence of hyperkeratotic skin lesions, neurosensory hearing loss, and vascularizing keratitis. Most mutations that have been discovered as a cause of KID syndrome are autosomal dominant, found in exon 2 of the Connexin (Cx) 26 gene. A G12R (p.Gly12Arg) is a GJB2 mutation reported in only two patients with KID syndrome to date. This article describes a patient with the G12R mutation and KID syndrome with interesting additional features, which include a porokeratotic eccrine ostial and dermal duct nevus, follicular occlusion triad, and unusual persistent oral mucosal papules. We compare this patient's phenotype with the only two other patients described with the same (G12R) mutation. The phenotypic heterogeneity of KID syndrome, inexplicable according to our current understanding of these proteins, speaks to the complexity of the connexin system and its overlapping expression patterns in different tissues.

Liu LM, Yan MG, Yang DH, et al.
The expression of protein inhibitor of activated signal transducers and activators of transcription 3 in the evolutionary process of gastric cancer.
Eur J Intern Med. 2011; 22(5):e31-5 [PubMed] Related Publications
OBJECTIVE: To study the expression of PIAS3 (protein inhibitor of activated signal transducers and activators of transcription 3) in the evolutionary process of gastric cancer.
METHODS: Samples were taken from the endoscopic biopsy specimens of 125 patients. Gastric mucosal lesions were diagnosed in HE staining, and chronic atrophic gastritis (CAG) with intestinal metaplasia (IM) were distinguished in AB-PAS and HID-AB staining. The expressions of PIAS3 gene in different types of gastric mucosal lesions were detected by immunocytochemistry and in situ hybridization. The results were analyzed using IPP 6.0 image analysis system, from which the average optical density was obtained of positive cells.
RESULTS: There were 25 patients with chronic superficial gastritis (CSG), 87 CAG (30 with complete intestinal IM, 27 with incomplete intestinal IM, 21 with complete colonic IM, 9 with incomplete colonic IM), 8 dysplasia (DYS) and 5 gastric cancer (GC). In the expressions of PIAS3 mRNA and protein, a difference was not found between the patients with CSG and those with CAG with complete or incomplete intestinal IM; however, a significant difference was statistically found among patients with CSG (or intestinal IM), complete colonic IM, incomplete colonic IM, DYS and GC, expression levels of which stepped down one by one.
CONCLUSIONS: There are differences in the PIAS3 expression from different stages of gastric precancerous conditions/lesions to GC, which may reveal a close relationship between expression reduction or loss of PIAS3 and gastric tumorigenesis.

Bennàssar A, Ferrando J, Grimalt R
Congenital atrichia and hypotrichosis.
World J Pediatr. 2011; 7(2):111-7 [PubMed] Related Publications
BACKGROUND: Alopecia present from birth includes a broad differential diagnosis and often represents a diagnostic and therapeutic challenge for the involved physician.
DATA SOURCES: An initial correct diagnosis and classification is essential because structural hair defects may be the expression of a genetic disorder affecting hair growth, part of a congenital syndrome with accompanying hair malformations, or a marker for an underlying metabolic disorder and may impact the mental and physical development of a child. Pathological hair loss rarely occurs in the first year of life; however, it may be a leading symptom of many congenital diseases.
RESULTS: In recent years, the clinical and microscopic features of hereditary hair shaft disorders have been characterized and classified. Furthermore, significant progress has been made in our knowledge of genes that control the normal development and differentiation of hair follicles, and thus the research is to define and classify the hair disorders within a genetic basis.
CONCLUSIONS: In this article we discuss several types of genotrichosis and provide a practical classification based on their clinical features.

Natsuga K, Akiyama M, Shimizu H
Malignant skin tumours in patients with inherited ichthyosis.
Br J Dermatol. 2011; 165(2):263-8 [PubMed] Related Publications
Inherited ichthyoses are rare genodermatoses caused by mutations in the genes involved in epidermal development. Although there have been case reports on patients with ichthyosis who developed skin malignancies, it is still unknown whether or not patients with ichthyosis have an increased risk of skin malignancies. Here, we review case series of skin malignancies in patients with ichthyosis and show biological findings which might lead to cancer susceptibility. A survey of the literature revealed 28 cases of inherited ichthyoses with skin malignancy, including 12 cases of keratitis-ichthyosis-deafness (KID) syndrome, seven of autosomal recessive congenital ichthyosis, three of Netherton syndrome and six of miscellaneous ichthyosis. Twenty-four of the 28 cases developed single or multiple squamous cell carcinomas (SCCs). The age at diagnosis of the first skin malignancy ranged from 15 to 54 years. As patients with these particular subtypes of ichthyosis seem to be prone to skin malignancies, including SCC, at an unusually young age, routine cancer surveillance of these patients is strongly recommended.

Sirnes S, Honne H, Ahmed D, et al.
DNA methylation analyses of the connexin gene family reveal silencing of GJC1 (Connexin45) by promoter hypermethylation in colorectal cancer.
Epigenetics. 2011; 6(5):602-9 [PubMed] Related Publications
Gap junctions are specialized plasma membrane domains consisting of channels formed by members of the connexin protein family. Gap junctional intercellular communication is often lost in cancers due to aberrant localization or downregulation of connexins, and connexins are therefore suggested to act as tumor suppressor genes in various tissues. The aim of this study was to investigate the expression pattern and DNA promoter methylation status of connexins in colorectal cancer. Expression of six (GJA1, GJA9, GJB1, GJB2, GJC1 and GJD3) connexin genes was detected in normal colonic tissue samples. GJC1 expression was reduced in colorectal carcinomas compared to normal tissue samples. All analyzed connexins were hypermethylated in colon cancer cell lines, although at various frequencies. GJA4, GJB6 and GJD2 were hypermethylated in 60% (29/48), 25% (12/48) and 96% (46/48) of primary colorectal carcinomas, respectively. However, the methylation status was not associated with gene expression. GJC1 has two alternative promoters, which were methylated in 42% (32/76) and 38% (25/65) of colorectal tumors, and in none of the normal mucosa samples. Expression of GJC1 was significantly lower in methylated compared with unmethylated samples (p < 0.01) and was restored in cell lines treated with the demethylating drug 5-aza-2'deoxycytidine. Taken together, DNA hypermethylation of the promoter region of GJC1, encoding connexin45, is an important mechanism in silencing gene expression in colorectal cancer.

Garcia-Rodríguez L, Pérez-Torras S, Carrió M, et al.
Connexin-26 is a key factor mediating gemcitabine bystander effect.
Mol Cancer Ther. 2011; 10(3):505-17 [PubMed] Related Publications
Gemcitabine is a nucleoside analogue with anticancer activity. Inside the cell, it is sequentially phosphorylated to generate the active drug. Phosphorylated nucleoside analogues have been shown to traffic through gap junctions. We investigated the participation of gap junctional intercellular communication (GJIC) as a possible mechanism spreading gemcitabine cytotoxicity in pancreatic tumors. Immunohistochemical analysis of pancreatic cancer biopsies revealed increased connexin 26 (Cx26) content but loss of connexins 32 (Cx32) and 43 (Cx43) expression. Cx26 abundance in neoplastic areas was confirmed by Cx26 mRNA in situ hybridization. Heterogeneity on the expression levels and the localization of Cx26, Cx32, and Cx43 were identified in pancreatic cancer cells and found to be associated with the extent of GJIC, and correlated with gemcitabine bystander cytotoxic effect. The abundance of Cx26 at the contact points in tumoral regions prompted us to study the involvement of Cx26 in the GJIC of gemcitabine toxic metabolites and their influence on the antitumoral effects of gemcitabine. Knockdown of Cx26 led to decreased GJIC and reduced gemcitabine bystander killing whereas overexpression of Cx26 triggered increased GJIC and enhanced the gemcitabine cytotoxic bystander effect. Gemcitabine treatment of mice bearing tumors, with a high GJIC capacity, resulted in a significant delay in tumor progression. Interestingly, gemcitabine administration in mice bearing tumors that overexpress Cx26 triggered a dramatic tumor regression of 50% from the initial volume. This study shows that Cx26 participates in the gap junction-mediated bystander cytoxic effect of gemcitabine and provides evidence that upregulation of Cx26 improves gemcitabine anticancer efficacy.

Nomura S, Maeda K, Noda E, et al.
Clinical significance of the expression of connexin26 in colorectal cancer.
J Exp Clin Cancer Res. 2010; 29:79 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Connexin26 (Cx26) is one of the connexins (Cxs) family members which form gap junction channels. Cx26 is considered to be a tumor suppressor gene. However, recent studies revealed that over expression of Cx26 is associated with a poor prognosis in several human cancers. This study investigated the correlation between Cx26 expression and the clinicopathological features and P53 expression in colorectal cancer.
METHODS: One hundred and fifty-three patients who underwent a curative resection were studied. Tissue samples were investigated by immunohistochemical staining using antibodies for Cx26 and P53. Moreover, apoptotic cells were detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining.
RESULTS: Cx26 expression was found in 83 cases (54.2%) and P53 expression in 71 cases (46.4%). A correlation was observed between the Cx26 expression and recurrence, histology, and p53 expression (P < 0.05). Cx26 positive tumors had significantly longer survival than Cx26 negative tumors (P < 0.05). A multivariate Cox analysis demonstrated that Cx26 expression was an independent prognostic factor (P < 0.05). However, no significant correlation was observed between Cx26 and AI.
CONCLUSION: This study suggests that Cx26 expression is an independent prognostic factor in patients that undergo a curative resection of colorectal cancer.

Bruzzoni-Giovanelli H, Fernandez P, Veiga L, et al.
Distinct expression patterns of the E3 ligase SIAH-1 and its partner Kid/KIF22 in normal tissues and in the breast tumoral processes.
J Exp Clin Cancer Res. 2010; 29:10 [PubMed] Free Access to Full Article Related Publications
SIAH proteins are the human members of an highly conserved family of E3 ubiquitin ligases. Several data suggest that SIAH proteins may have a role in tumor suppression and apoptosis. Previously, we reported that SIAH-1 induces the degradation of Kid (KIF22), a chromokinesin protein implicated in the normal progression of mitosis and meiosis, by the ubiquitin proteasome pathway. In human breast cancer cells stably transfected with SIAH-1, Kid/KIF22 protein level was markedly reduced whereas, the Kid/KIF22 mRNA level was increased. This interaction has been further elucidated through analyzing SIAH and Kid/KIF22 expression in both paired normal and tumor tissues and cell lines. It was observed that SIAH-1 protein is widely expressed in different normal tissues, and in cells lines but showing some differences in western blotting profiles. Immunofluorescence microscopy shows that the intracellular distribution of SIAH-1 and Kid/KIF22 appears to be modified in human tumor tissues compared to normal controls. When mRNA expression of SIAH-1 and Kid/KIF22 was analyzed by real-time PCR in normal and cancer breast tissues from the same patient, a large variation in the number of mRNA copies was detected between the different samples. In most cases, SIAH-1 mRNA is decreased in tumor tissues compared to their normal counterparts. Interestingly, in all breast tumor tissues analyzed, variations in the Kid/KIF22 mRNA levels mirrored those seen with SIAH-1 mRNAs. This concerted variation of SIAH-1 and Kid/KIF22 messengers suggests the existence of an additional level of control than the previously described protein-protein interaction and protein stability regulation. Our observations also underline the need to re-evaluate the results of gene expression obtained by qRT-PCR and relate it to the protein expression and cellular localization when matched normal and tumoral tissues are analyzed.

Inose T, Kato H, Kimura H, et al.
Correlation between connexin 26 expression and poor prognosis of esophageal squamous cell carcinoma.
Ann Surg Oncol. 2009; 16(6):1704-10 [PubMed] Related Publications
BACKGROUND: Failure of gap junction formation affects the development of various types of cancer. We aimed to clarify the clinicopathologic outcome and prognostic significance of connexin (Cx) 26 in human esophageal squamous cell carcinoma (ESCC).
METHODS: Immunohistochemical staining for Cx26 was performed on surgical specimens obtained from 123 patients with ESCC.
RESULTS: There was no positive staining for Cx26-specific expression in normal esophageal squamous cells. Primary ESCC with Cx26-positive expression was detected in the cytoplasm of cancer cell nests in 60 cases. Cx26 expression was correlated with N (lymph node metastasis, P = 0.014) and the number of metastatic lymph nodes (P = 0.047). The 5-year survival rates of ESCC patients with Cx26-positive expression were significantly lower than those with Cx26-negative expression (positive, 39.7%; negative, 65.7%; P = 0.007). By multivariate analysis, tumor-node-metastasis (TNM) clinical classification (T, P < 0.001; N, P = 0.002; M, P = 0.046) and Cx26 (P = 0.024) were independent prognosis predictors of ESCC.
CONCLUSIONS: These results suggest that abnormal expression of Cx26 participates in the progress of ESCC.

Nojima H, Ohba Y, Kita Y
Oleamide derivatives are prototypical anti-metastasis drugs that act by inhibiting Connexin 26.
Curr Drug Saf. 2007; 2(3):204-11 [PubMed] Related Publications
Despite considerable research, metastasis remains a major challenge in the clinical management of cancer. Recent reports show that abnormally augmented expression of Cx26 is responsible for the enhanced spontaneous metastasis of mouse BL6 melanoma cells. The function of Cx26 appears to be responsible for this phenotype since exogenous expression of a dominant-negative form of Cx26 and oleamide derivatives called MI-18 and MI-22 that specifically inhibit Cx26-mediated gap junction-mediated intercellular communications (GJIC) prevent the spontaneous metastasis of BL6 cells. As expected from their structural similarity to oleic acid (the major component of olive oil), both MI-18 and MI-22 are safe drugs; nonetheless, they are potent inhibitors of the spontaneous metastasis of BL6 mouse melanoma cells. Thus, they are a novel prototype of an anti-metastasis drug that has minimal side effects. While the primary tumors do not necessarily show strong Cx26-immunostaining signals, pronounced Cx26 expression is detected in the highly invasive tumor regions; it is also more frequently observed in metastasized tumors. Thus, Cx26 expression may be useful as a prognostic tool that can predict the existence of highly metastatic cancer cells in clinical samples.

Endoh H, Ishibashi Y, Yamaki E, et al.
Immunohistochemical analysis of phosphorylated epidermal growth factor receptor might provide a surrogate marker of EGFR mutation.
Lung Cancer. 2009; 63(2):241-6 [PubMed] Related Publications
PURPOSE: Overexpression of EGFR is found in several malignancies including lung cancers. Recently, EGFR mutation has been shown to correlate with responsiveness to tyrosine kinase inhibitors (TKI). Although antibodies against phophorylated EGFR have been used in vitro, phosphorylated EGFR has yet not been examined well in resected non-small cell lung cancers (NSCLCs).
EXPERIMENTAL DESIGN: We studied the immunohistochemistry of anti-EGFR and phosphorylated EGFR in 97 resected NSCLCs, examined the relationship with EGFR mutation, and performed quantitative RT-PCR of the EGFR gene in the TaqMan assay.
RESULT: EGFR mutation was seen in 27% of 97 NSCLCs and 37% of 70 adenocarcinomas. EGFR was stained in 60% of 97 NSCLCs. Phosphorylation of tyrosine 845 (pY845) and 1068 (pY1068) was positive in 49% and 48%, respectively. The observed correlation with EGFR mutation and pY845 or pY1068 was statistically significant (P=0.0001 for pY845, P<0.0001 for pY1068, chi square test), although phospho-EGFR status was not associated with a particular mutation type. pY1068-positive tumors also correlated with female, light smoker, and adenocarcinoma histology, but not with mRNA expression. Moreover, patients with pY1068-positive tumors showed prolonged survival (P=0.0093, log-rank test).
CONCLUSION: It is possible that immunohistochemistry of phosphorylated EGFR can substitute for EGFR mutation analysis. Further investigation is necessary to determine whether phospho-EGFR immunohistochemistry predicts response to TKIs and survival benefit.

Curtin JF, Candolfi M, Puntel M, et al.
Regulated expression of adenoviral vectors-based gene therapies: therapeutic expression of toxins and immune-modulators.
Methods Mol Biol. 2008; 434:239-66 [PubMed] Free Access to Full Article Related Publications
Regulatable promoter systems allow gene expression to be tightly controlled in vivo. This is highly desirable for the development of safe, efficacious adenoviral vectors that can be used to treat human diseases in the clinic. Ideally, regulatable cassettes should have minimal gene expression in the "OFF" state, and expression should quickly reach therapeutic levels in the "ON" state. In addition, the components of regulatable cassettes should be non-toxic at physiological concentrations and should not be immunogenic, especially when treating chronic illness that requires long-lasting gene expression. In this chapter, we will describe in detail protocols to develop and validate first generation (Ad) and high-capacity adenoviral (HC-Ad) vectors that express therapeutic genes under the control of the TetON regulatable system. Our laboratory has successfully used these protocols to regulate the expression of marker genes, immune stimulatory genes, and toxins for cancer gene therapeutics, i.e., glioma that is a deadly form of brain cancer. We have shown that this third generation TetON regulatable system, incorporating a doxycycline (DOX)-sensitive rtTA(2)S-M2 inducer and tTS(Kid) silencer, is non-toxic, relatively non-immunogenic, and can tightly regulate reporter transgene expression downstream of a TRE promoter from adenoviral vectors in vitro and also in vivo.

Zhu CC, Bornemann DJ, Zhitomirsky D, et al.
Drosophila histone deacetylase-3 controls imaginal disc size through suppression of apoptosis.
PLoS Genet. 2008; 4(2):e1000009 [PubMed] Free Access to Full Article Related Publications
Histone deacetylases (HDACs) execute biological regulation through post-translational modification of chromatin and other cellular substrates. In humans, there are eleven HDACs, organized into three distinct subfamilies. This large number of HDACs raises questions about functional overlap and division of labor among paralogs. In vivo roles are simpler to address in Drosophila, where there are only five HDAC family members and only two are implicated in transcriptional control. Of these two, HDAC1 has been characterized genetically, but its most closely related paralog, HDAC3, has not. Here we describe the isolation and phenotypic characterization of hdac3 mutations. We find that both hdac3 and hdac1 mutations are dominant suppressors of position effect variegation, suggesting functional overlap in heterochromatin regulation. However, all five hdac3 loss-of-function alleles are recessive lethal during larval/pupal stages, indicating that HDAC3 is essential on its own for Drosophila development. The mutant larvae display small imaginal discs, which result from abnormally elevated levels of apoptosis. This cell death occurs as a cell-autonomous response to HDAC3 loss and is accompanied by increased expression of the pro-apoptotic gene, hid. In contrast, although HDAC1 mutants also display small imaginal discs, this appears to result from reduced proliferation rather than from elevated apoptosis. The connection between HDAC loss and apoptosis is important since HDAC inhibitors show anticancer activities in animal models through mechanisms involving apoptotic induction. However, the specific HDACs implicated in tumor cell killing have not been identified. Our results indicate that protein deacetylation by HDAC3 plays a key role in suppression of apoptosis in Drosophila imaginal tissue.

Nakajima K, Nakano H, Takiyoshi N, et al.
Papillon-Lefèvre syndrome and malignant melanoma. A high incidence of melanoma development in Japanese palmoplantar keratoderma patients.
Dermatology. 2008; 217(1):58-62 [PubMed] Related Publications
Papillon-Lefèvre syndrome (PLS) is a rare autosomal-recessive genodermatosis characterized by palmoplantar hyperkeratosis and severe early-onset periodontitis. The development of malignant cutaneous neoplasms within the hyperkeratotic lesions of the syndrome is quite rare. Here, we report on a 51-year-old Japanese woman with PLS associated with recurrent malignant melanoma (MM). Mutation analysis of the cathepsin C gene revealed that the proband was homozygous for a missense mutation, c.415G-->A, which is predicted to result in the amino acid substitution p.G139R. Including our case, 4 families have been described as having PLS with MM, 3 of which are Japanese, implying a high incidence of melanoma development in Japanese PLS patients. We suggest that hereditary palmoplantar keratoderma (PPK) in Japanese patients might be predisposed to MM. A literature review revealed that in 18 cases of MM-associated PPK, 13 (76%) were Japanese, suggesting a high incidence of MM in Japanese PPK patients. This tendency might be attributable to the high frequency of acral lentiginous melanoma in Japanese subjects, in contrast to a lower frequency of this subtype in Caucasians.

Ezumi K, Yamamoto H, Murata K, et al.
Aberrant expression of connexin 26 is associated with lung metastasis of colorectal cancer.
Clin Cancer Res. 2008; 14(3):677-84 [PubMed] Related Publications
PURPOSE: Connexin 26 (Cx26) is one of the gap junction-forming family members classically considered to be tumor suppressors. However, recent studies show association of elevated expression of Cx26 with poor prognosis in several human malignancies. Furthermore, Cx26 has been observed to be indispensable to spontaneous metastasis of melanoma cells. Here, we assessed Cx26 expression in primary colorectal cancer (CRC) and the metastatic lesions to elucidate its role in metastasis.
EXPERIMENTAL DESIGN: Cx26 expression was assessed in 25 adenomas, 167 CRCs, and normal mucosa, together with the metastatic lesions.
RESULTS: Normal mucosa and adenomatous tissue expressed Cx26 mainly in the plasma membrane, whereas cancer cells mostly contained Cx26 in the cytoplasm. The incidence of aberrant Cx26 expression varied widely in CRC (mean, 49.5 +/- 35.5%), and the expression levels were confirmed by Western blot and quantitative reverse transcription-PCR. Clinicopathologic survey revealed association of high expression with less differentiated histology and venous invasion (P = 0.0053 and P = 0.0084, respectively). Notably, high Cx26 expression was associated with shorter disease-free survival and shorter lung metastasis-free survival in 154 curatively resected CRC sets (P = 0.041 and P = 0.028, respectively). Survey of metastatic lesions revealed that lung metastasis, but not liver and lymph nodes metastases, expressed higher Cx26 than the CRC series or corresponding primary CRCs (P < 0.0001 and P = 0.0001, respectively).
CONCLUSIONS: These findings suggest that aberrant expression of Cx26 plays an essential role in lung metastasis. Thus, Cx26 is a promising therapeutic target, particularly for CRC patients who develop lung metastasis.

Naoi Y, Miyoshi Y, Taguchi T, et al.
Connexin26 expression is associated with aggressive phenotype in human papillary and follicular thyroid cancers.
Cancer Lett. 2008; 262(2):248-56 [PubMed] Related Publications
Connexin26 (Cx26), a component of GAP junctions and until recently believed to be a tumor suppressor gene, has been shown to play an important role in lymphatic invasion as well as lymph node and distant metastases in squamous lung cancer and breast cancer. In the study presented here, we investigated Cx26 expression in human papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) and its relationship with various clinicopathological parameters. Of 69 PTCs, 33 were positive for Cx26 (47.8%), as were five of 11 FTCs (45.5%), all follicular thyroid adenomas (n=22) and normal thyroid tissues (n=20) were negative for Cx26. A statistically significant association was observed between Cx26 expression and large tumor size (p=0.028 for PTC) and lymph node metastases (p=0.053 (marginally significant) for PTC and p=0.035 for FTC). Presence of intra-glandular dissemination of tumor cells was significantly (p=0.048) more frequent in Cx26-positive (30.3%) than Cx26-negative PTCs (11.1%). Lymphatic vessel invasion was more frequent in Cx26-positive PTCs (6.1%) than in Cx26-negative PTCs (0%) though the difference was not statistically significant. These results suggest that Cx26 may be implicated in the pathogenesis of PTC and FTC and is associated with the biologically aggressive phenotypes of these tumors.

Luo C, Mori I, Goshima F, et al.
Replication-competent, oncolytic herpes simplex virus type 1 mutants induce a bystander effect following ganciclovir treatment.
J Gene Med. 2007; 9(10):875-83 [PubMed] Related Publications
Cells expressing herpes simplex virus (HSV) thymidine kinase (tk) are killed by ganciclovir (GCV). Adjacent cells without HSV-tk also die, a phenomenon known as the 'bystander effect'. However, there is no evidence that replication-competent HSV induces a bystander effect in the presence of GCV. Therefore, we investigated the bystander effect in HEp-2 cells infected with replication-competent, oncolytic HSV-1 mutants, hrR3 and HF10. In cells infected at a multiplicity of infection (MOI) of 3, GCV did not induce apoptosis. At low MOIs of 0.3 and 0.03, however, a number of adjacent, uninfected cells apoptosed following GCV treatment. Irrespective of GCV treatment, HEp-2 cells expressed minimal levels of connexin 43 (Cx43). However, Cx43 expression was enhanced by GCV in response to infection with HF10 at an MOI of 0.3, but not at an MOI of 3. Expression of other proteins involved in gap junctions, including Cx26 and Cx40, was not augmented under these conditions. The PKA and PI3K signal transduction pathways are likely involved in enhanced Cx43 expression as inhibitors of these pathways prevented Cx43 upregulation. These results suggest that infection with replication-competent HSV-1 induces the bystander effect in cells treated with GCV because of efficient intercellular transport of active GCV through abundant gap junctions.

McLachlan E, Shao Q, Laird DW
Connexins and gap junctions in mammary gland development and breast cancer progression.
J Membr Biol. 2007; 218(1-3):107-21 [PubMed] Related Publications
The development and function of the mammary gland require precise control of gap junctional intercellular communication (GJIC). Here, we review the expression and function of gap junction proteins, connexins, in the normal mouse and human mammary gland. We then discuss the possible tumor-suppressive role of Cx26 and Cx43 in primary breast tumors and through the various stages of breast cancer metastasis and consider whether connexins or GJIC may actually promote tumorigenesis at some stages. Finally, we present in vitro data on the impact of connexin expression on breast cancer cell metastasis to the bone. We observed that Cx43 expression inhibited the invasive and migratory potentials of MDA-MB-231 breast cancer cells in a bone microenvironment, provided by the MC3T3-E1 mouse osteoblastic cell line. Expression of either Cx26 or Cx43 had no effect on MDA-MB-231 growth and adhesion under the influence of osteoblasts and did not result in regulation of osteogenic gene expression in these breast cancer cells. Furthermore, connexin-expressing MDA-MB-231 cells did not have an effect on the growth or differentiation of MC3T3-E1 cells. In summary, we conclude that connexin expression and GJIC are integral to the development and differentiation of the mammary gland. In breast cancer, connexins generally act as tumor suppressors in the primary tumor; however, in advanced breast tumors, connexins appear to act as both context-dependent tumor suppressors and facilitators of disease progression.

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