KLLN; killin, p53-regulated DNA replication inhibitor
The protein encoded by this intronless gene is found in the nucleus, where it can inhibit DNA synthesis and promote S phase arrest coupled to apoptosis. The expression of this DNA binding protein is upregulated by transcription factor p53. [provided by RefSeq, Dec 2012]
Mahdi H, Mester JL, Nizialek EA, et al. Germline PTEN, SDHB-D, and KLLN alterations in endometrial cancer patients with Cowden and Cowden-like syndromes: an international, multicenter, prospective study. Cancer. 2015; 121(5):688-96 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
BACKGROUND: Endometrial cancer has been recognized only recently as a major component of Cowden syndrome (CS). Germline alterations in phosphatase and tensin homolog (PTEN; PTEN_mut+), succinate dehydrogenase B/C/D (SDHB-D; SDHx_var+), and killin (KLLN_Me+) cause CS and Cowden syndrome-like (CSL) phenotypes. This study was aimed at identifying the prevalence and clinicopathologic predictors of germline PTEN_mut+, SDHx_var+, and KLLN_Me+ in CS/CSL patients presenting with endometrial cancer. METHODS: PTEN and SDHB-D mutation and KLLN promoter methylation analyses were performed for 371 prospectively enrolled patients (2005-2011). PTEN protein was analyzed from patient-derived lymphoblast lines. The PTEN Cleveland Clinic (CC) score is a weighted, regression-based risk calculator giving the a priori risk for PTEN_mut+. Demographic and clinicopathologic features were correlated with the specific gene. RESULTS: Germline PTEN_mut+, SDHx_var+, and KLLN_Me+ were found in 7%, 9.8%, and 10.5% of informative samples, respectively. Predictors of PTEN_mut+ included an age ≤ 50 years (odds ratio [OR] for an age < 30 years, 6.1 [P = .015]; OR for an age of 30-50 years, 4.4 [P = .001]), macrocephaly (OR, 14.4; P < .001), a higher CC score (OR for a 1-U increment, 1.35; P < .001), a PTEN protein level within the lowest quartile (OR, 5.1; P = .039), and coexisting renal cancer (OR, 5.7; P = .002). KLLN_Me+ patients were on average 8 years younger than KLLN_Me- patients (44 vs 52 years, P = .018). Predictors of KLLN_Me+ were a younger age and a higher CC score. On the other hand, no clinical predictors of SDH_var+ were found. CONCLUSIONS: Clinical predictors of PTEN and KLLN alterations, but not SDHx_var+, were identified. These predictors should alert the treating physician to potential heritable risk and the need for referral to genetic professionals. High-risk cancer surveillance and prophylactic surgery of the uterus may be considered for KLLN_Me+ patients similarly to PTEN_mut+ patients.
Beamer LC Cowden syndrome: what oncology nurses need to know about increased risk of developing certain cancers. Oncol Nurs Forum. 2014; 41(5):555-7 [PubMed] Related Publications
Cowden syndrome (CS) is a genetic disorder characterized by multiple benign tissue growths (i.e., hamartomas) and an increased risk of developing specific cancers, such as breast, thyroid, kidney, endometrial, or colorectal cancer (Genetics Home Reference, 2012). This genetic syndrome was named after a person diagnosed with the disorder (Lloyd & Dennis, 1963). CS is part of a larger syndrome called PTEN hamartomatous syndrome, which also includes Bannayan-Riley-Ruvalcaba syndrome, PTEN-related Proteus syndrome, and Proteus-like syndrome (Eng, 2014).
Wang Y, Roma A, Nolley R, et al. Nuclear KLLN expression associates with improved relapse-free survival for prostate carcinoma. Endocr Relat Cancer. 2014; 21(4):579-86 [PubMed] Related Publications
Men with organ-confined prostate cancer (CaP) are often treated with radical prostatectomy. Despite similar postoperative characteristics, a significant proportion of men with an intermediate risk of progression experience prostate-specific antigen (PSA)-defined failure, while others have relapse-free survival (RFS). Additional prognostic markers are needed to predict the outcome of these patients. KLLN is a transcription factor that regulates the cell cycle and induces apoptosis in cancer cells. We have shown that KLLN is an androgen-regulated gene and that loss of KLLN expression in primary CaP is associated with high Gleason score. In this retrospective study, we evaluated KLLN expression in the high-grade malignancy components from 109 men with intermediate risk CaP. Patients with nuclear KLLN-negative tumors had significantly higher preoperative serum PSA levels (12.24±2.37 ng/ml) and larger tumor volumes (4.61±0.71 cm(3)) compared with nuclear KLLN-positive patients (8.35±2.45 ng/ml, P=0.03, and 2.66±0.51 cm(3), P<0.0001, respectively). None of the nuclear KLLN-positive tumors had capsular penetration, whereas 34% of nuclear KLLN-negative tumors (P=0.004) had capsular penetration. Maintaining KLLN expression in tumor nuclei, but not in cytoplasm or stroma, associated with improved RFS after surgery (P=0.002). Only 7% of patients with nuclear KLLN-positive tumors had tumor recurrence, while 60% of patients in the KLLN-negative group developed PSA-defined failure with median relapse time of 6.6 months (P=0.0003). Our data suggest that KLLN expression may be used as a prognostic marker to predict outcome for intermediate risk patients, which could provide useful information for postoperative management.
Wang Y, Yu Q, He X, et al. Activation of AR sensitizes breast carcinomas to NVP-BEZ235's therapeutic effect mediated by PTEN and KLLN upregulation. Mol Cancer Ther. 2014; 13(2):517-27 [PubMed] Related Publications
NVP-BEZ235 is a newly developed dual PI3K/mTOR inhibitor, being tested in multiple clinical trials, including breast cancer. NVP-BEZ235 selectively induces cell growth inhibition in a subset, but not all, breast cancer cell lines. However, it remains a challenge to distinguish between sensitive and resistant tumors, particularly in the pretreatment setting. Here, we used ten breast cancer cell lines to compare NVP-BEZ235 sensitivity and in the context of androgen receptor (AR) activation during NVP-BEZ235 treatment. We also used female SCID mice bearing breast tumor xenografts to investigate the beneficial effect of dihydrotestosterone/NVP-BEZ235 combination treatment compared with each alone. We found that AR-positive breast cancer cell lines are much more sensitive to NVP-BEZ235 compared with AR-negative cells, regardless of PTEN or PI3KCA status. Reintroducing AR expression in NVP-BEZ235 nonresponsive AR-negative cells restored the response. DHT/NVP-BEZ235 combination not only resulted in a more significant growth inhibition than either drug alone, but also achieved tumor regression and complete responses for AR(+)/ER(+) tumors. This beneficial effect was mediated by dihydrotestosterone (DHT)-induced PTEN and KLLN expression. Furthermore, DHT could also reverse NVP-BEZ235-induced side effects such as skin rash and weight loss. Our data suggest that AR expression may be an independent predictive biomarker for response to NVP-BEZ235. AR induction could add benefit during NVP-BEZ235 treatment in patients, especially with AR(+)/ER(+) breast carcinomas.
Nizialek EA, Peterson C, Mester JL, et al. Germline and somatic KLLN alterations in breast cancer dysregulate G2 arrest. Hum Mol Genet. 2013; 22(12):2451-61 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
PTEN is a well-described predisposition gene for Cowden syndrome (CS), a familial cancer syndrome characterized by a high risk of breast and other cancers. KLLN, which shares a bidirectional promoter with PTEN, causes cell cycle arrest and apoptosis. We previously identified germline hypermethylation of the KLLN promoter in 37% of PTEN mutation-negative CS/CS-like (CSL) patients. Patients with germline KLLN hypermethylation have an increased prevalence of breast and renal cancers when compared with PTEN mutation carriers. We have consequently sought to identify and characterize germline KLLN variants/mutations in CS/CSL and in apparently sporadic breast cancer patients. KLLN variants in CS/CSL patients are rare (1 of 136, 0.007%). Interestingly, among 438 breast cancer patients, 13 (3%) have germline KLLN variants when compared with none in 128 controls (P = 0.049). Patients with KLLN variants have a family history of breast cancer when compared with those without (P = 0.02). We demonstrate that germline KLLN variants dysregulate the cell cycle at G2. Of 24 breast carcinomas analyzed, 3 (13%) have somatic KLLN hemizygous deletions, with somatic loss of the wild-type allele in a patient with germline KLLN p.Leu119Leu. Of 452 breast carcinomas in The Cancer Genome Atlas project, 93 (21%) have KLLN hemizygous or homozygous deletions. This is the first study to associate germline KLLN variants with sporadic breast cancer and to recognize somatic KLLN deletions in breast carcinomas. Our observations suggest that KLLN may be a low penetrance susceptibility factor for apparently sporadic breast cancer.
Wang Y, He X, Yu Q, Eng C Androgen receptor-induced tumor suppressor, KLLN, inhibits breast cancer growth and transcriptionally activates p53/p73-mediated apoptosis in breast carcinomas. Hum Mol Genet. 2013; 22(11):2263-72 [PubMed] Related Publications
Androgen receptor (AR) expression by immunohistochemistry correlates with better prognosis and survival among breast cancer patients. We and others have shown that AR inhibits proliferation and induces apoptosis in breast cancer cells. However, the mechanism of AR's anti-tumor effect in breast cancer is still not fully understood. Our recent study indicates that AR upregulates expression of tumor suppressor gene PTEN by promoter activation in breast cancer. KLLN, encoding KLLN protein, is a newly identified gene, which shares a bidirectional promoter with PTEN and is transcribed in the opposite direction. So far, the function of KLLN has never been studied in tumorigenesis. Here, we define KLLN as a tumor suppressor in breast carcinomas, which inhibits tumor growth and invasiveness. After analyzing 188 normal breast and 1247 malignant breast cancer tissues, we observed the loss of KLLN in multiple breast cancer subtypes and this decreased KLLN expression associates with tumor progression and increasing histological grade in invasive carcinomas. We characterize KLLN, for the first time, as a transcription factor, directly promoting the expression of TP53 and TP73, with consequent elevated apoptosis and cell cycle arrest in breast cancer cells. We demonstrate, in vitro and in murine xenograph models, that both KLLN and PTEN are AR-target genes, mediating androgen-induced growth inhibition and apoptosis in breast cancer cells. Our observations suggest that KLLN might be used as a potential prognostic marker and novel therapy target for breast carcinomas.
Wang Y, Radhakrishnan D, He X, et al. Transcription factor KLLN inhibits tumor growth by AR suppression, induces apoptosis by TP53/TP73 stimulation in prostate carcinomas, and correlates with cellular differentiation. J Clin Endocrinol Metab. 2013; 98(3):E586-94 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
CONTEXT: KLLN is a newly identified gene with unknown function and shares a bidirectional promoter with PTEN. OBJECTIVE: The objective of the study was to analyze the relationship between KILLIN (KLLN) expression and prostate cancer and the potential tumor suppressive effect. DESIGN: We conducted an in silico analysis to compare KLLN expression in normal prostate and matched primary carcinoma tissues. We subsequently used immunohistochemistry to examine KLLN expression and association with Gleason grade and score in 109 prostatectomy samples. KLLN's tumor-suppressive effect was studied in androgen-dependent and androgen-independent cell models. PATIENTS: Patients were diagnosed with peripheral zone prostate carcinomas without metastasis at the time of prostatectomy. Each patient's primary tumor comprised at least 2 tumoral regions with different Gleason grades. RESULTS: KLLN expression decreased from normal prostate tissue to primary carcinomas (P < .0001). The loss of epithelial and stromal KLLN expression is associated with poor differentiation and high Gleason scores (P < .0001), consistent with our in vitro observation that KLLN inhibits tumor cell proliferation and invasiveness. KLLN decreases prostate-specific antigen levels and suppresses androgen-mediated cell growth by inhibiting androgen receptor (AR) transcription. As an androgen receptor-regulated target, KLLN also functions as a transcriptional activator, directly promoting the expression of TP53 and TP73, with consequent elevated apoptosis, regardless of AR status. CONCLUSIONS: Our observations suggest that KLLN is a transcription factor directly regulating AR, TP53, and TP73 expression, with a role in prostate carcinogenesis. Loss of KLLN associates with high Gleason scores, suggesting that KLLN might be used as a potential prognostic marker for risk management and as a novel therapy target for advanced prostate carcinomas.
Thompson ER, Gorringe KL, Choong DY, et al. Analysis of KLLN as a high-penetrance breast cancer predisposition gene. Breast Cancer Res Treat. 2012; 134(2):543-7 [PubMed] Related Publications
KLLN is a p53 target gene with DNA binding function and represents a highly plausible candidate breast cancer predisposition gene. We screened for predisposing variants in 860 high-risk breast cancer families using high resolution melt analysis. A germline c.339_340delAG variant predicted to cause premature termination of the protein after 57 alternative amino acid residues was identified in 3/860 families who tested negative for BRCA1 and BRCA2 mutations and in 1/84 sporadic breast cancer cases. However, the variant was also detected in 2/182 families with known BRCA1 or BRCA2 mutations and in 2/464 non-cancer controls. Furthermore, loss of the mutant allele was detected in 2/2 breast tumors. Our data suggest that pathogenic mutations in KLLN are rare in breast cancer families and the c.339_340delAG variant does not represent a high-penetrance breast cancer risk allele.
Ngeow J, Mester J, Rybicki LA, et al. Incidence and clinical characteristics of thyroid cancer in prospective series of individuals with Cowden and Cowden-like syndrome characterized by germline PTEN, SDH, or KLLN alterations. J Clin Endocrinol Metab. 2011; 96(12):E2063-71 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
CONTEXT: Thyroid cancer is believed to be an important component of Cowden syndrome (CS). Germline PTEN and SDHx mutations and KLLN epimutation cause CS and CS-like phenotypes. Despite the established association, little is known about the incidence and clinical features of thyroid cancer found in CS/CS-like patients. OBJECTIVE: The aim of the study was to compare incidence, clinical, and histological characteristics of epithelial thyroid cancers in CS/CS-like individuals, in the context of PTEN, SDHx, and KLLN status. DESIGN AND PARTICIPANTS: The study encompassed a 5-yr, multicenter, prospective accrual of 2723 CS and CS-like patients, all of whom had comprehensive PTEN analysis. SDHx mutation analysis occurred in those without PTEN mutations/variations and elevated manganese superoxide dismutase (MnSOD) levels. KLLN epimutation analysis was performed in the subset without any PTEN or SDHx mutation/deletion/ variant/polymorphism. MAIN OUTCOME MEASURES: Gene-specific thyroid cancer histologies, demographic and clinical information, and adjusted standardized incidence rates were studied. RESULTS: Of 2723 CS/CS-like patients, 664 had thyroid cancer. Standardized incidence rates for thyroid cancer were 72 [95% confidence interval (CI), 51-99; P < 0.001] for pathogenic PTEN mutations, 63 (95% CI, 42-92; P < 0.001) for SDHx variants, and 45 (95% CI, 26-73; P < 0.001) for KLLN epimutations. All six (16.7%) diagnosed under age 18 yr carried pathogenic PTEN mutations. Follicular thyroid cancer was overrepresented in PTEN mutation-positive cases compared to those with SDHx and KLLN alterations. PTEN frameshift mutations were found in 31% of patients with thyroid cancer compared to 17% in those without thyroid cancer. CONCLUSIONS: CS/CS-like patients have elevated risks of follicular thyroid cancer due to PTEN pathogenic mutations and of papillary thyroid cancer from SDHx and KLLN alterations. Children presenting with thyroid cancer should be tested for PTEN mutations.
Bennett KL, Campbell R, Ganapathi S, et al. Germline and somatic DNA methylation and epigenetic regulation of KILLIN in renal cell carcinoma. Genes Chromosomes Cancer. 2011; 50(8):654-61 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
We recently identified germline methylation of KILLIN, a novel p53-regulated tumor suppressor proximal to PTEN, in >1/3 Cowden or Cowden syndrome-like (CS/CSL) individuals who are PTEN mutation negative. Individuals with germline KILLIN methylation had increased risks of renal cell carcinoma (RCC) over those with PTEN mutations. Therefore, we tested the hypothesis that KILLIN may be a RCC susceptibility gene, silenced by germline methylation. We found germline hypermethylation by combined bisulfite restriction analysis in at least one of the four CpG-rich regions in 23/41 (56%) RCC patients compared to 0/50 controls (P < 0.0001). Of the 23, 11 (48%) demonstrated methylation in the -598 to -890 bp region in respect to the KILLIN transcription start site. Furthermore, 19 of 20 advanced RCC showed somatic hypermethylation upstream of KILLIN, with the majority hypermethylated at more than one CpG island (13/19 vs. 3/23 with germline methylation, P < 0.0001). qRT-PCR revealed that methylation significantly downregulates KILLIN expression (P = 0.05), and demethylation treatment by 5-aza-2'deoxycytidine significantly increased KILLIN expression in all RCC cell lines while only increasing PTEN expression in one line. Furthermore, targeted in vitro methylation revealed a significant decrease in KILLIN promoter activity only. These data reveal differential epigenetic regulation by DNA promoter methylation of this bidirectional promoter. In summary, we have identified KILLIN as a potential novel cancer predisposition gene for nonsyndromic clear-cell RCC, and the epigenetic mechanism of KILLIN inactivation in both the germline and somatic setting suggests the potential for treatment with demethylating agents.
Bennett KL, Mester J, Eng C Germline epigenetic regulation of KILLIN in Cowden and Cowden-like syndrome. JAMA. 2010; 304(24):2724-31 [PubMed] Article available free on PMC after 01/03/2016 Related Publications
CONTEXT: Germline loss-of-function phosphatase and tensin homolog gene (PTEN) mutations cause 80% of Cowden syndrome, a rare autosomal-dominant disorder (1 in 200,000 live births), characterized by high risks of breast, thyroid, and other cancers. A large heterogeneous group of individuals with Cowden-like syndrome, who have various combinations of Cowden syndrome features but who do not meet Cowden syndrome diagnostic criteria, have PTEN mutations less than 10% of the time, making molecular diagnosis, prediction, genetic counseling, and risk management challenging. Other mechanisms of loss of function such as hypermethylation, which should result in underexpression of PTEN or of KILLIN, a novel tumor suppressor transcribed in the opposite direction, may account for the remainder of Cowden syndrome and Cowden-like syndrome. OBJECTIVE: To determine whether germline methylation is found in Cowden syndrome or Cowden-like syndrome in individuals lacking germline PTEN mutations. DESIGN, SETTING, AND PARTICIPANTS: Nucleic acids from prospective nested series of 123 patients with Cowden syndrome or Cowden-like syndrome and 50 unaffected individuals without PTEN variants were analyzed for germline methylation and expression of PTEN and KILLIN at the Cleveland Clinic, August 2008-June 2010. Prevalence of component cancers between groups was compared using the Fisher exact test. MAIN OUTCOME MEASURES: Frequency of germline methylation in PTEN mutation-negative Cowden syndrome and Cowden syndrome-like individuals. Prevalence of component cancers in methylation-positive and PTEN mutation-positive individuals. RESULTS: Of 123 patients with Cowden syndrome or Cowden-like syndrome, 45 (37%; 95% confidence interval [CI], 29%-45%) showed hypermethylation upstream of PTEN but no transcriptional repression. The germline methylation was found to transcriptionally down-regulate KILLIN by 250-fold (95% CI, 45-14 286; P = .007) and exclusively disrupted TP53 activation of KILLIN by 30% (95% CI, 7%-45%; P = .008). Demethylation treatment increased only KILLIN expression 4.88-fold (95% CI, 1.4-18.1; P = .05). Individuals with KILLIN -promoter methylation had a 3-fold increased prevalence of breast cancer (35/42 vs 24/64; P < .0001) and a greater than 2-fold increase of kidney cancer (4/45 vs 6/155; P = .004) over individuals with germline PTEN mutations. CONCLUSIONS: Germline KILLIN methylation is common among patients with Cowden syndrome or Cowden-like syndrome and is associated with increased risks of breast and renal cancer over PTEN mutation-positive individuals. These observations need to be replicated.