Effect of cycline D1 (CCND1) gene polymorphism on tumor formation and behavior in patients with prolactinoma

The objective of this study was to investigate the effect of G870A gene polymorphism of CCND1 on the formation and behavioral features of prolactinomas. One hundred and thirteen patients with prolactinoma and 108 age and gender matched control were included in the study. The patients were divided into two groups as noninvasive and invasive tumors. CCND1 G870A gene polymorphism was compared in patients/control and invasive/noninvasive groups. A and G allele frequencies were found as 41.7% and 58.3% in the controls, and 61.1% and 38.9% in the patients (p<0.01). Rates of G/G, G/A and A/A genotypes were found as 11.8%, 55.9% and 32.4% in the noninvasive group, and 15.6%, 44.4% and 40.0% in the invasive group, respectively. Differences between patient and control groups were significant but were not between invasive and noninvasive groups in terms of the allele frequencies and genotype distribution. Mean tumor size and serum levels of prolactin at the time of diagnosis and change in these values after the treatment were not found statistically significant in genotype subgroups. CCND1 G870A gene polymorphism may be an important factor in the early stages of the tumor formation. However, it did not affect the features of the tumor.     

Regulation of IGF-1-dependent cyclin D1 and E expression by hEag1 channels in MCF-7 cells: The critical role of hEag1 channels in G1 phase progression

Insulin-like Growth Factor-1 (IGF-1) plays a key role in breast cancer development and cell cycle regulation. It has been demonstrated that IGF-1 stimulates cyclin expression, thus regulating the G1 to S phase transition of the cell cycle. Potassium (K⁺) channels are involved in the G1 phase progression of the cell cycle induced by growth factors. However, mechanisms that allow growth factors to cooperate with K⁺ channels in order to modulate the G1 phase progression and cyclin expression remain unknown. Here, we focused on hEag1 K⁺ channels which are over-expressed in breast cancer and are involved in the G1 phase progression of breast cancer cells (MCF-7). As expected, IGF-1 increased cyclin D1 and E expression of MCF-7 cells in a cyclic manner, whereas the increase of CDK4 and 2 levels was sustained. IGF-1 stimulated p21^WAF1/Cip1 expression with a kinetic similar to that of cyclin D1, however p27^Kip1 expression was insensitive to IGF-1. Interestingly, astemizole, a blocker of hEag1 channels, but not E4031, a blocker of HERG channels, inhibited the expression of both cyclins after 6-8 h of co-stimulation with IGF-1. However, astemizole failed to modulate CDK4, CDK2, p21^WAF1/Cip1 and p27^Kip1 expression. The down-regulation of hEag1 by siRNA provoked a decrease in cyclin expression. This study is the first to demonstrate that K⁺ channels such as hEag1 are directly involved in the IGF-1-induced up-regulation of cyclin D1 and E expression in MCF-7 cells. By identifying more specifically the temporal position of the arrest site induced by the inhibition of hEag1 channels, we confirmed that hEag1 activity is predominantly upstream of the arrest site induced by serum-deprivation, prior to the up-regulation of both cyclins D1 and E.     

MiR-489 regulates chemoresistance in breast cancer via epithelial mesenchymal transition pathway

To investigate the role of microRNAs in the development of chemoresistance and related epithelial–mesenchymal transition (EMT), we examined the effect of miR-489 in adriamycin (ADM)-resistant human breast cancer cells (MCF-7/ADM). MiR-489 was significantly suppressed in MCF-7/ADM cells compared with chemosensitive parental control MCF-7/WT cells. Forced-expression of miR-489 reversed chemoresistance. Furthermore, Smad3 was identified as the target of miR-489 and is highly expressed in MCF-7/ADM cells. Forced expression of miR-489 both inhibited Smad3 expression and Smad3 related EMT properties. Finally, the interactions between Smad3, miR-489 and EMT were confirmed in chemoresistant tumor xenografts and clinical samples, indicating their potential implication for treatment of chemoresistance.     

siRNA-cyclin D1对乳腺癌MCF-7细胞增殖的抑制作用

研究小干扰RNA(small interfering RNA,siRNA)对乳腺癌MCF-7细胞株cyclin D1表达的抑制及对细胞增殖的影响。化学合成针对cyclin D1基因的siRNA,转染MCF-7细胞株;分别应用荧光定量PCR和免疫印迹测定cyclin D1 mRNA和蛋白的表达,CCK-8测定细胞的增殖活性,流式细胞仪检测细胞周期,软琼脂培养检测细胞克隆形成能力。在实验中,10、50、100 nmol/L siRNA-cyclin D1分别使MCF-7细胞cyclin D1 mRNA表达降低了57．85%、63．22%和68．02%,蛋白表达降低了51．13%、62．09%、77．68%。转染siRNA-cyclin D1后,细胞增殖受到抑制,细胞周期阻滞于G1期,软琼脂克隆形成率降低。结果提示siRNA可以有效抑制MCF-7细胞株中cyclin D1的表达,使细胞周期阻滞于G1期,从而抑制细胞增殖。     

Cyclin D1 G870A Polymorphism and Risk of Nasopharyngeal Carcinoma: A Case-Control Study and Meta-Analysis

Background

Cyclin D1 (CCND1) plays a key role in cell cycle regulation. It is a well-established human oncogene which is frequently amplified or overexpressed in cancers. The association between CCND1 G870A polymorphism and cancer risk has been widely assessed. However, a definitive conclusion between CCND1 G870A polymorphism and risk of nasopharyngeal carcinoma (NPC) remains elusive.

Methods

We firstly performed a hospital-based case-control study involving 165 NPC cases and 191 cancer-free controls in central-south China, and then conducted a meta-analysis with six case-control studies to evaluate the association between NPC risk and CCND1 G870A polymorphism.

Results

The case-control study found a significant association between CCND1 G870A polymorphism and NPC risk in various comparison models (AA vs. GG: OR = 2.300, 95% CI 1.089–4.857, p = 0.029; AG vs. GG: OR = 2.832, 95% CI 1.367–5.867, p = 0.005; AA/AG vs. GG: OR = 2.597, 95% CI 1.288–5.237, p = 0.008; AA vs. AG/GG: OR = 0.984, 95% CI 0.638–1.518, p = 0.944). Further meta-analysis showed that there was no significant association between CCND1 G870A polymorphism and NPC risk in overall analysis. In the stratified analysis by race, however, significant associations were only found in Caucasians (for the allele model A vs. G: OR = 0.75, 95% CI 0.59–0.97, p = 0.03; for the co-dominant model AA vs. GG: OR = 0.52, 95% CI 0.32–0.86, p = 0.01; for the dominant model AA/AG vs. GG: OR = 0.49, 95% CI 0.32–0.74, p<0.01; for the recessive model AA vs. AG/GG: OR = 0.90, 95% CI 0.61–1.34, p = 0.60).

Conclusions

A significant association between CCND1 G870A polymorphism and NPC risk was found in the central-southern Chinese population. The meta-analysis indicated that CCND1 G870A polymorphism may contribute to the development of NPC in Caucasians.     

MicroRNA‐551b‐3p inhibits tumour growth of human cholangiocarcinoma by targeting Cyclin D1

MicroRNAs (miRNAs) are powerful regulators in the tumorigenesis of cholangiocarcinoma (CCA). Previous studies report that miR‐551b‐3p acts as an oncogenic factor in ovarian cancer, but plays a tumour suppressive role in gastric cancer. However, the expression pattern and potential function of miR‐551b‐3p were still unclear in CCA. Therefore, this study aimed to explore the expression of miR‐551b‐3p and its role as well as molecular mechanism in CCA. Analysis of TCGA dataset suggested that miR‐551b‐3p was under‐expressed in CCA tissues compared to normal bile duct tissues. Furthermore, our data confirmed the decreased levels of miR‐551b‐3p in CCA samples and cell lines. Interestingly, TCGA data suggested that low miR‐551b‐3p level indicated reduced overall survival of CCA patients. Gain‐ and loss‐of‐function experiments found that miR‐551b‐3p inhibited the proliferation, G1‐S phase transition and induced apoptosis of CCA cells. In vivo experiments revealed that ectopic expression of miR‐551b‐3p inhibited tumour growth of CCA in mice. Further investigation demonstrated that miR‐551b‐3p directly bond to the 3′‐UTR of Cyclin D1 (CCND1) mRNA and negatively regulated the abundance of CCND1 in CCA cells. An inverse correlation between miR‐551b‐3p expression and the level of CCND1 mRNA was detected in CCA tissues from TCGA dataset. Notably, CCND1 knockdown showed similar effects to miR‐551b‐3p overexpression in HuCCT‐1 cells. CCND1 restoration rescued miR‐551b‐3p‐induced inhibition of proliferation, G1 phase arrest and apoptosis in HuCCT‐1 cells. In summary, miR‐551b‐3p inhibits the expression of CCND1 to suppress CCA cell proliferation and induce apoptosis, which may provide a theoretical basis for improving CCA treatment.     

Cyclin D1 (CCND1) G870A gene polymorphism is an ethnicity-dependent risk factor for digestive tract cancers: a meta-analysis comprising 20,271 subjects

Published data on the association between Cyclin D1 (CCND1) G870A gene polymorphism and digestive tract cancers (DTC) are inconclusive. We carried out a meta-analysis of published case-control studies to derive a more precise estimation of the association. Relevant studies were identified from PubMed, EMBASE, and China National Knowledge Infrastructure up to February 1st, 2011. Crude odds ratios (OR) and 95% confidence intervals (CI) were used to investigate the strength of the association. Data were available from a total of 33 case-control studies with 8534 cases and 11,737 controls. The combined results based on all studies showed that there was a statistically significant link between CCND1 G870A polymorphism and DTC risk (GG vs. AA: OR=0.83, 95%CI=0.71-0.96). In the analysis of ethnic groups, we found the A allele carriers had a significantly increased DTC susceptibility among Caucasians, but not among Asians. When stratified for tumor location, the results based on all studies only showed the variant allele 870A might have a significantly increased risk of colorectal cancer (CRC), especially of rectal cancer (GG vs. AA: OR=0.71, 95%CI=0.58-0.89). When stratifying by the stage and histological differentiation of CRC, we only observed that patients had a significantly higher frequency of CCND1 870 AA than non-cancer patients among Caucasians. The A allele carriers (hetero- or homozygotes) were significantly more common in cases with a family history of CRC than in controls. There was no evidence of publication bias for CCND1 G870A polymorphism with DTC risk. In summary, this meta-analysis demonstrates that the CCND1 G870A polymorphism may be an ethnicity-dependent risk factor for DTC. And this genetic variant may increase the risk of rectal cancer, but not colon cancer.     

Cyclin D1 G870A polymorphism is associated with an increased risk of hepatocellular carcinoma in the Turkish population: Case–control study

Background: A common G to A polymorphism (G870A) in the splice donor region of exon 4 of cyclin D1 (CCND1) gene generates two mRNAs (cyclin D1a and D1b) through an alternative splicing at the site of this polymorphism. Cyclin D1a and b proteins differ in their COOH-terminus, a region involved in protein degradation. We examined the association between this CCDN1 genotype and the susceptibility to hepatocellular carcinoma (HCC) in a Turkish population. Methods: The genotype frequency of this polymorphism was determined by using a polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) assay. Hospital-based case–control study was designed consisting of 160 diagnosis subjects with hepatocellular carcinoma and 160 cancer-free control subjects matched on age, gender, smoking and alcohol status. Results: The allele frequencies of case subjects (A, 0.55; G, 0.45) were significantly different from those of control subjects (A, 0.42; G, 0.58) (p = 0.002). The odds ratios (ORs) for the CCND1 870 GA and AA genotypes when compared with the GG genotypes were 1.39 (95% confidence interval [CI] 0.82–2.36, p = 0.22) and 2.52 (95% CI 1.38–4.62, p = 0.003) respectively. The presence of at least one CCND1 870A allele was associated with increased risk for HCC (OR, 1.73; 95% CI, 1.06–2.82, p = 0.03). When combining the GG and GA genotypes as a reference genotype, we found that the OR for the AA genotype was 2.06 (95% CI 1.24–3.44, p = 0.006). Conclusion: Our results suggest that the CCND1 G870A single nucleotide polymorphism is associated with an increased risk of HCC in our Turkish population.     

Potential role of CCND1 G870A genotype as a predictor for urothelial carcinoma susceptibility and muscle-invasiveness in Taiwan

The cell cycle regulator cyclin D1 (CCND1) is thought to play a major role in the transition of cell cycle from G1 to S phase. It is known that a common CCND1 G870A genotype is associated with bladder cancer in Japan and China, but not in the Western World. There is neither a report about its role in Taiwan's population, nor its genetic role of CCND1 G870A in another worldwide urothelial cancer, upper tract urothelial cancer (UTUC). Therefore, we aimed at investigating the role of CCND1 G870A in both bladder cancer and UTUC in Taiwanese cohorts. The CCND1 G870A genotypes of 171 (101 bladder cancer and 70 UTUC) patients and 243 control subjects were determined by PCR-RFLP and their correlation with clinical and histopathological data was evaluated. The genotype analysis results showed that CCND1 GG genotype was associated with a lower risk overall in urothelial (P = 0.008, OR = 0.44, 95% CI = 0.24-0.81) and bladder cancer patients (P = 0.008, OR = 0.34, 95% CI = 0.15-0.76) than those of the AA genotype. In addition, patients carrying the AG genotype had a 0.29-fold lower odds ratio of muscle-invasive cancer procession (95% CI = 0.12-0.70) compared with those carrying the AA genotype in bladder cancer patients. Surprisingly, the GG genotype had a 5.88-fold higher odds ratio of muscle-invasive cancer procession (95% CI = 1.08-32.01) compared with those carrying the AA genotype in UTUC. No association between any CCND1 G870A genotype and higher-grade risk was found. Our results suggest that the G allele of the CCND1 G870A polymorphism may be a potential predictive and prognostic biomarker to distinguish between bladder cancer and UTUC in Taiwan.     

Cyclin D1 (G870A) polymorphism and risk of cervix cancer: a case control study in north Indian population

Cyclin D1 (CCND1) is a key regulatory protein, playing a critical role in the transition from G1 to S phase of the cell cycle. We have evaluated the association between CCND1 A870G polymorphism and risk of cervix cancer in north Indian women by using PCR-RFLP method. This association was estimated by computing odds ratio (ORs) and a 95% Confidence Intervals (95% CI) using a Multivariate Logistic Regression Analysis. No significant association was observed between CCND1 genotypes and overall risk of cervix cancer. But when stratified histologically, statistically significant (OR: 3.7, 95% CI: 1.56-8.87, P: 0.001) increased risk of squamous cell carcinoma (SCC) was observed for individuals with AA genotype. Thus our findings suggest that CCND1 (G870A) polymorphism may be associated with increased risk of SCC of the uterine cervix in north Indian women.     

Fibroblast growth factor 8 increases breast cancer cell growth by promoting cell cycle progression and by protecting against cell death

Fibroblast growth factor 8 (FGF-8) is expressed in a large proportion of breast cancers, whereas its level in normal mammary gland epithelium is low. Previous studies have shown that FGF-8b stimulates breast cancer cell growth in vitro and in vivo. To explore the mechanisms by which FGF-8b promotes growth, we studied its effects on cell cycle regulatory proteins and signalling pathways in mouse S115 and human MCF-7 breast cancer cells. We also studied the effect of FGF-8b on cell survival. FGF-8b induced cell cycle progression and up-regulated particularly cyclin D1 mRNA and protein in S115 cells. Silencing cyclin D1 with siRNA inhibited most but not all FGF-8b-induced proliferation. Inhibition of the FGF-8b-activated ERK/MAPK pathway decreased FGF-8b-stimulated proliferation. Blocking the constitutively active PI3K/Akt and p38 MAPK pathways also lowered FGF-8b-induced cyclin D1 expression and proliferation. Corresponding results were obtained in MCF-7 cells. In S115 and MCF-7 mouse tumours, FGF-8b increased cyclin D1 and Ki67 levels. Moreover, FGF-8b opposed staurosporine-induced S115 cell death which effect was blocked by inhibiting the PI3K/Akt pathway but not the ERK/MAPK pathway. In conclusion, our results suggest that FGF-8b increases breast cancer cell growth both by stimulating cell cycle progression and by protecting against cell death.     

Estrogens down-regulate p27Kip1 in breast cancer cells through Skp2 and through nuclear export mediated by the ERK pathway

The cyclin-dependent kinase (CDK) inhibitor p27Kip1 plays a key role in growth and development of the mammary epithelium and in breast cancer. p27Kip1 levels are regulated through ubiquitin/proteasome-mediated proteolysis, promoted by CDK2 and the F box protein Skp2 at the G1/S transition, and independent of Skp2 in mid-G1. We investigated the respective roles of Skp2 and subcellular localization of p27Kip1 in down-regulation of p27Kip1 induced in MCF-7 cells by estrogens. 17beta-Estradiol treatment increased Skp2 expression in MCF-7 cells; however, this increase was prevented by G1 blockade mediated by p16Ink4a or the CDK inhibitor roscovitine, whereas down-regulation of p27Kip1 was maintained. Exogenous Skp2 prevented growth arrest of MCF-7 cells by antiestrogen, coinciding with decreased p27Kip1 expression. Under conditions of G1 blockade, p27Kip1 was stabilized by inhibition of CRM1-dependent nuclear export with leptomycin B or by mutation of p27Kip1 (Ser10 --> Ala; S10A) interfering with CRM1/p27Kip1 interaction. Antisense Skp2 oligonucleotides and a dominant-interfering Cul-1(1-452) mutant prevented down-regulation of p27Kip1S10A, whereas Skp2 overexpression elicited its destruction in mitogen-deprived cells. Active mediators of the extracellular signal-regulated kinase (ERK) pathway including Raf-1caax induced cytoplasmic localization of p27Kip1 in antiestrogen-treated cells and prevented accumulation of p27Kip1 in these cells independent of Skp2 expression and coinciding with ERK activation. Genetic or chemical blockade of the ERK pathway prevented down-regulation and cytoplasmic localization of p27Kip1 in response to estrogen. Our studies indicate that estrogens elicit down-regulation of p27Kip1 in MCF-7 cells through Skp2-dependent and -independent mechanisms that depend upon subcellular localization of p27Kip1 and require the participation of mediators of the Ras/Raf-1/ERK signaling pathway.     

Med19 is involved in chemoresistance by mediating autophagy through HMGB1 in breast cancer

Adriamycin (ADM)-based regimens are the most effective chemotherapeutic treatments for breast cancer. However, intrinsic and acquired chemoresistance is a major therapeutic problem. Our goal was to clarify the role of mediator complex subunit 19 (Med19) in chemotherapy resistance and to elucidate the related molecular mechanisms. In this study, ADM-resistant human cells (MCF-7/ADM) and tissues exhibited increased Med19 expression and autophagy levels relative to the corresponding control groups. Additionally, MCF-7/ADM cells showed changes in two selective markers of autophagy. There was a dose-dependent increase in the light chain 3 (LC3)-II/LC3-I ratio and a decrease in sequestosome 1 (P62/SQSTMl) expression. Furthermore, lentivirus-mediated Med19 inhibition significantly attenuated the LC3-II/LC3-I ratio, autophagy-related gene 3 (Atg3) and autophagy-related gene 5 (Atg5) expression, P62 degradation, and red fluorescent protein-LC3 dot formation after treatment with ADM or rapamycin, an autophagy activator. Furthermore, the antiproliferative effects of ADM, cisplatin (DDP), and taxol (TAX) were significantly enhanced after suppressing Med19 expression. Notably, the effects of Med19 on autophagy were mediated through the high-mobility group box-1 (HMGB1) pathway. Our findings suggest that Med19 suppression increased ADM chemosensitivity by downregulating autophagy through the inhibition of HMGB1 signaling in human breast cancer cells. Thus, the regulatory mechanisms of Med19 in autophagy should be investigated to reduce tumor resistance to chemotherapy.     

CCND1 G870A polymorphism interaction with cigarette smoking increases lung cancer risk: meta-analyses based on 5008 cases and 5214 controls

Evidence indicates CCND1 G870A polymorphisms as a risk factor for a number of cancers. Increasing studies have been conducted on the association of CCND1 G870A polymorphism with lung cancer risk. However, the results were controversial. The aim of the present study was to derive a more precise estimation of the relationship. Meta-analyses examining the association between CCND1 G870A polymorphism and lung cancer were performed. Subgroup analyses regarding ethnicity, smoking status, histological types and source of controls were also implemented. All eligible studies for the period up to May 2012 were identified. The overall data from ten case–control studies including 5,008 cases and 5,214 controls indicated that variant A allele may have an association with increased lung cancer risk (AA vs GG: OR = 1.21; 95 % CI = 1.08–1.36, dominant model: OR = 1.09; 95 % CI = 1.00–1.19, recessive model: OR = 1.23; 95 % CI = 1.01–1.49). In the subgroup analysis by ethnicity, A allele may elevate lung cancer risk among Asians but not Caucasians or Mixed ethnicities. In smoking status subgroup, A allele was shown to associate with increased lung cancer risk among smokers but not non-smokers. In the subgroup analysis by histological types, increased cancer risks were shown in adenocarcinoma but not squamous cell carcinoma, under the homozygote comparison and recessive models. Collectively, the results of the present study suggest that CCND1 G870A polymorphism might be a low-penetrant risk factor for lung cancer, particularly among Asians and smokers. Moreover, homozygous AA alleles might have a correlation with increased lung adenocarcinoma susceptibility.     

Expression of splice variants of 1α-hydroxylase in mcf-7 breast cancer cells

1,25-Dihydroxyvitamin D₃ (calcitriol) is the most active natural metabolite of Vitamin D₃. It has strong antiproliferative and differentiating effects on various cell types including breast cancer cells. 25-Hydroxyvitamin D₃-1α-hydroxylase (1α-hydroxylase, CYP27B1) is one of the key enzymes in the formation of calcitriol. It has been found in breast cancer cells suggesting an autocrine regulation of formation of calcitriol in these cells. Alternative splicing of the encoding genes for this enzyme can possibly play a role in regulating the enzyme level and can explain tissue specific variations of 1α-hydroxylase activity. Splice variants containing intron 1 may encode for truncated proteins with deletion of protein domains which are essential for its enzymatic activity. In order to obtain more information on the abundance of 1α-hydroxylase splice variants, we performed a highly specific nested touchdown PCR in MCF-7 cells. The full-length sequence of 1α-hydroxylase and two different splice variants of this enzyme containing intron 1 were isolated. By Western blot technique we then confirmed the protein products of the full-length enzyme and its splice variants. We hypothesize that that the expression of splice variants can lead to a quantitatively lower expression of the mRNA of the full-length enzyme. The abundance of less active 1α-hydroxylase protein variants can alter the local synthesis of calcitriol in the cells and may explain variations of enzymatic activity in different cells and tissues.     

Modulation of beta-catenin by cyclin-dependent kinase 6 in Wnt-stimulated cells

Beta-catenin is implicated in quite different cellular processes, which require a fine-tuned regulation of its function. Here we demonstrate that cyclin-dependent kinase 6 (CDK6), in association with cyclin D1 (CCND1), directly binds to beta-catenin. We showed that CCND1-CDK6 phosphorylates beta-catenin on serine 45 (S45). This phosphorylation creates a priming site for glycogen synthase kinase 3beta (GSK3beta) and is both necessary and sufficient to initiate the beta-catenin phosphorylation-degradation cascade. Moreover, co-immunoprecipitation assays using Wnt3a-conditioned medium reveals that while Wnt stimulation leads to the dissociation of beta-catenin from axin and casein kinase Ialpha (CKIalpha), Wnt treatment promotes an increase in CCND1 level and the association of beta-catenin with CCND1-CDK6. Furthermore, Wnt3a-stimulated cytosolic beta-catenin levels were higher in CDK6 knockout mouse embryonic fibroblasts (CDK6-/- MEFs) compared to wild-type MEFs. Thus, the CCND1-CDK6 complex is like to negatively regulate Wnt signaling by mediating beta-catenin phosphorylation and its subsequent degradation in Wnt-stimulated cells.     

Loss of CDKN2A expression is a frequent event in primary invasive melanoma and correlates with sensitivity to the CDK4/6 inhibitor PD0332991 in melanoma cell lines

We have investigated the potential for the p16‐cyclin D‐CDK4/6‐retinoblastoma protein pathway to be exploited as a therapeutic target in melanoma. In a cohort of 143 patients with primary invasive melanoma, we used fluorescence in situ hybridization to detect gene copy number variations (CNVs) in CDK4, CCND1, and CDKN2A and immunohistochemistry to determine protein expression. CNVs were common in melanoma, with gain of CDK4 or CCND1 in 37 and 18% of cases, respectively, and hemizygous or homozygous loss of CDKN2A in 56%. Three‐quarters of all patients demonstrated a CNV in at least one of the three genes. The combination of CCND1 gain with either a gain of CDK4 and/or loss of CDKN2A was associated with poorer melanoma‐specific survival. In 47 melanoma cell lines homozygous loss, methylation or mutation of CDKN2A gene or loss of protein (p16^INK4A) predicted sensitivity to the CDK4/6 inhibitor PD0332991, while RB1 loss predicted resistance.