Validation of cyclin D1/CDK4 as an anticancer drug target in MCF-7 breast cancer cells: Effect of regulated overexpression of cyclin D1 and siRNA-mediated inhibition of endogenous cyclin D1 and CDK4 expression

Summary We have examined the role of cyclin D1 and cyclin-dependent kinase-4 (CDK4) in the cell cycle progression and proliferation of MCF-7 breast cancer cells. Forced expression of cyclin D1 using a tetracycline-regulated expression system, and suppression of endogenous cyclin D1 and CDK4 using small interfering RNA (siRNA) were used to validate this protein complex as a drug target in cancer drug discovery. Overexpression of cyclin D1 increased both phosphorylation of the retinoblastoma gene product (RB) and passage through the G1–S phase transition, resulting in increased proliferation of cells. When cyclin D1 expression was shut off, growth rates fell below those seen in control cell lines transfected with the vector, indicating an increased dependence on this protein for proliferation. Inhibition of endogenous cyclin D1 or CDK4 expression by RNA interference resulted in hypophosphorylation of RB and accumulation of cells in G1. These results support the prevailing view that pharmacological inhibition of cyclin D1/CDK4 complexes is a useful strategy to inhibit the growth of tumors. Furthermore, since MCF-7 cells appear to be dependent on this pathway for their continued proliferation, it is a suitable cell line to test novel cyclin D1/CDK4 inhibitors.     

EXPRESSION OF CYCLIN D1 AND CDK4 IN OSTEOSARCOMA OF THE JAWS

The main cause of the cellular malignant proliferation is the disorder of cell division and growth. The alterations of proteins and genes that involved in this process correlate closely with the occurrence and vicious phenotype of neoplasm. Cyclin D1 and cyclin-dependent kinase 4 (CDK4) regulatory proteins in G1 phase have a direct bearing on carcinogenesis. Presently, gene amplification, overexpression, chromosome inversion andtranslocation of cyclin D1 and CDK4 have been discovered in ma…     

CDK4, CDK6, cyclin D1, p16(INK4a) and EGFR expression in glioblastoma with a primitive neuronal component

Glioblastoma with primitive neuroectodermal tumor-like component (GBM-PNET) is a rare variant of glioblastoma, which was renamed as glioblastoma with a primitive neuronal component (GBM-PN) in new WHO classification of tumours of the central nervous system in 2016. There are few publications on the investigation of GBM-PN. In this study, PCR mRNA arrays on 6 cases of conventional GBM and 10 cases of GBM-PN showed high mRNA level of CDK4 in GBM-PN and low mRNA level of EGFR in GBM-PN. Immunohistochemical stains on tissue microarrays with 28 cases of conventional GBM and 13 cases of GBM-PN demonstrated that CDK4 was selectively expressed in the primitive neuronal component of all GBM-PN cases while EGFR was positive in conventional GBM and glial component of GBM-PN, but was negative in the primitive neuronal component of all GBM-PN cases. Immunohistochemical stains with antibodies against proteins that interact with CDK4 in cell cycle regulation, such as CDK6, cyclin D1 and p16(INK4a), were performed on these GBM-PN and GBM cases. CDK6 was patchily positive in rare cases of GBM-PN and cyclin D1 was negative in GBM-PN cases. p16(INK4a) is traditionally known as an inhibitor of CDK4 and CDK6. p16(INK4a) might not be the inhibitor of CDK4 in GBM-PN cases because seven GBM-PN cases were positive for both CDK4 and p16(INK4a). It indicates that CDK4 and p16(INK4a) might play a crucial role in GBM-PN pathogenesis. Since CDK4 and EGFR are highly expressed in the primitive neuronal component and in the glial component of GBM-PN respectively, the combination of CDK4/6 inhibitor and targeted therapy against EGFR might be potential effective therapeutic regimen for GBM-PN. CDK4 and EGFR immuohistochemical stain patterns make the diagnosis of GBM-PN much easier.     

Notch-1 regulates Akt signaling pathway and the expression of cell cycle regulatory proteins cyclin D1, CDK2 and p21 in T-ALL cell lines

Gain-of-function mutations in Notch-1 are common in T-cell lymphoblastic leukemia (T-ALL), making this receptor a promising target for drugs such as gamma-secretase inhibitors (GSIs). However, GSIs seem to be active in only a small fraction of T-ALL cell lines with constitutive Notch-1 activity and the downstream response of Notch signaling is only partially understood. To further investigate the molecular mechanisms underlying proliferation suppression and apoptosis and explore effective downstream target genes, we used RNA interference (RNAi) technology to down-regulate the expression of Notch-1 in GSIs-resistant T-ALL cell lines. Results showed that down-regulation of Notch-1 by transfection of a small interfering RNA (siRNA) could cause SupT1 cells proliferation inhibition by inducing G₀/G₁ cell cycle arrest and apoptosis. The proliferation inhibitory and apoptotic effects resulting from down-regulation of Notch-1 may be mediated through regulating the expression of cell cycle regulatory proteins cyclin D1, CDK2 and p21 and the activity of Akt signaling. In addition, our results demonstrated that down-regulation of Notch-1 signaling could sensitize SupT1 cells to adriamycin. Taken together, cell cycle regulatory proteins and Akt signaling may be attractive targets in T-ALL.     

Comparison of deregulated expression of cyclin D1 and cyclin E with that of cyclin-dependent kinase 4 (CDK4) and CDK2 in human oesophageal squamous cell carcinoma.

The expressions of cyclin D1, cyclin E, cyclin-dependent kinase 4 (CDK4), and CDK2 were immunohistochemically examined in 90 patients with human oesophageal squamous cell carcinoma (SCC) to determine their relationship to the tumour behaviour and patient prognosis. Nuclear immunostaining of cyclin D1 and cyclin E was observed in 28 (31.1%) and 27 tumours (30.0%) respectively. Thirty-nine tumours (43.3%) and 31 tumours (34.4%) exhibited both cytoplasmic and nuclear positivity for CDK4 and CDK2 respectively. Of 28 cyclin D1-positive and 27 cyclin E-positive tumours, CDK4 was overexpressed in 12 (42.8%) tumours and CDK2 in seven (25.9%) tumours respectively. There was no significant relationship in immunopositivity between cyclin D1 and CDK4 or between cyclin E and CDK2. Simultaneous immunoreactivity for both cyclin D1 and CDK4 was significantly associated with venous invasion (P < 0.05). In a univariate analysis, the prognosis of patients with tumours that were both cyclin D1- and CDK4-positive was significantly poorer than that of patients with cyclin D1-negative tumours (P < 0.05). In a multivariate analysis, both cyclin D1 and CDK4 immunoreactivities (P < 0.01) and tumour stage (P < 0.001) were recognized as independent risk factors. In this analysis, the hazard ratio for cyclin D1-positive and CDK4-negative cases compared with cyclin D1-negative cases was significant (hazard ratio = 3.128, 95% confidence interval = 1.418-6.899, P = 0.0047). No significant prognostic relevance was detected in both cyclin E and CDK2 immunoreactivity. Our in vivo findings suggest that in human oesophageal SCC, cyclin D1 and cyclin E and their functional partners, CDK4 and CDK2, often exhibit dysregulated overexpression in many cases, and that tumours with simultaneous expression of cyclin D1 and CDK4 are frequently associated with venous invasion and have a worse prognosis, statistically. Moreover, overexpression of cyclin D1 alone may also contribute to tumour progression independent of CDK4 overexpression.     

Alteration of cyclin D1 and CDK4 gene in carcinoma of uterine cervix

Amplification and overexpression of cyclin D1 and CDK4 genes in cervical carcinoma were studied by semi-quantitative differential polymerase chain reaction assay and an immunostaining technique, respectively. Amplifications of cyclin D1 and CDK4 genes were found in 24% (27/113) and 26% (29/112) of tumors, respectively. Overexpression of cyclin D1 and CDK4 was demonstrated in 32% (21/66) and 73% (45/62) of tumors, respectively. No tumor showed CDK4 gene mutation on single strand conformational polymorphism. Sixteen percent (8/49) of the tumor specimens showed neither amplification nor overexpression. Disease stage, tumor grade and overexpression of cyclin D1 were found to be independent poor prognostic factors in cervical carcinoma.     

Loss of p27Kip1 from cyclin E/cyclin-dependent kinase (CDK) 2 but not from cyclin D1/CDK4 complexes in cells transformed by polyamine biosynthetic enzymes

Cancer cells are known to display up-regulation of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), the key enzymes in the biosynthesis of polyamines that are essential for cellular proliferation. We have shown previously that overexpression of ODC or AdoMetDC alone can induce tumorigenic transformation of rodent fibroblasts. Because the subversion of normal cell cycle control is thought to be a crucial event in cancer development, we examined ODC- and AdoMetDC-transformed fibroblasts for alterations in the cell cycle components. The level of cyclin D1 and cyclin D1-dependent kinase and total cyclin-dependent kinase (CDK) 4 activities were elevated in the ODC transformants and particularly in the AdoMetDC transformants. Cyclin E content was not elevated, but a moderate increase in cyclin E-dependent kinase activity was seen in both cells. Total CDK2 activity was increased only in the ODC-transformed cells. The amount of the p27Kip1 CDK inhibitor was greatly decreased in both transformants. Nevertheless, p27Kip1 was present in the active cyclin D1/CDK4 complexes in the cells but absent from the cyclin E/CDK2 complexes. Restoration of p27Kip1 expression in the ODC- and AdoMetDC-transformed cells by transfection resulted in growth inhibition, but not in morphological reversion. An elevation in the level of hyperphosphorylated retinoblastoma protein was observed mainly in the ODC-transformed cells. These results suggest that the expression of ODC or AdoMetDC may affect cell cycle regulation in many ways. However, the largest common effect, which is therefore potentially relevant to some aspects of transformation, appears to be the constitutive down-regulation of p27Kip1 and its loss from the cyclin/CDK2 complexes.     

Aberrant expression of nitric oxide synthase in human polyps, neoplastic colonic mucosa and surrounding peritumoral normal mucosa

The expression of nitric oxide synthase (NOS) was studied byNAD(P)H diaphorase histochemical localization method in (i)individual cells of the normal colonic mucosa (n = 13) whichserved as control, (ii) colonic polyps (n = 14), (iii) coloniccarcinoma (n = 20) and (iv) peritumoral mucosa (2 and 5 or 10cm away from the tumor). Four of the tumor specimens had normalepithelium adjacent to the cancer, which thus served as an internalcontrol. The expression of NOS activity in colon cancer wassignificantly reduced as compared to the control group of individuals(P < 0.004); undetectable in 25%, diminished in 45%, normalin 30%. On comparing the expression in normal mucosa and polypsthere was a significant reduction of the expression in polyps(P < 0.027); undetectable in 14%, reduced in 35%, normalin 51%. When compared to the peritumoral mucosa at 2 and 10cm the tumor showed a significant reduction in expression ofNOS activity (P < 0.001 and P < 0.0001 respectively).There was no significant difference seen in the expression at2 and 10 cm (P = 0.329). The peritumoral mucosa at a distanceof 2 cm away from the tumor when compared to the control mucosashowed no significant difference (P = 1.000), although thereis a tendency to a high normal expression of NOS activity inthe mucosa at a distance of 2 cm. Similarly, there was no significantdifference between the control mucosa and the peritumoral mucosaobtained at a distance of 10 cm (P = 0.383). The expressionof NOS activity in all tissues examined was abolished by preincubationof tissue with the selective NOS inhibitor L–NMMA butnot with D–NMMA. Our data showed extensive and significantreduction as identified by the NAD(P)H diaphorase method inthe expression of NOS activity, thereby reflecting the activityof nitric oxide in colon cancer and colonic polyps. The generalizedsuppression of this activity, which precedes the onset of overtneoplasia, may be an important event in colon carcinogenesis.This aberrant expression could also be compatible with the selectiveadvantage to either tumor promotion and metastatic progressionor to tumoricidal activity.     

细胞周期蛋白cyclin D1、CDK4在食管癌中的表达及其意义

目的：获得食管癌发生过程中调节Ｇ１细胞周期各种因子的作用。方法：采用抗ｃｙｃｌｉｎＤ１和ＣＤＫ４的单克隆抗体对１０例下沉食管和５０例食管鳞状上皮癌标本进行免疫组织化学染色。结果：ｃｙｃｌｉｎＤ１和ＣＤＫ４在正常食管上皮呈现较低水平的表达,在食管鳞状上皮癌中则过表达。２７／５０食管鳞状上皮癌ｙｃｙｃｌｉｎＤ１染色阳性,其中８例强阳性,１２例只表达ＣＤＫ４,１１例只表达ｃｙｃｌｉｎＤ１,１４例既表达ｃ     

Parallel cyclin E and cyclin A expression in neoplastic lesions of the uterine cervix

Cyclin E levels are high during late G1 and early S-phase in normal cells. The cyclin E expression over the cell cycle in tumours is not fully known. The impact on patient outcome by high cyclin E levels during other parts of the cell cycle than late G1- and early S-phase is unknown. We set out to study the expression of cyclin E over the cell cycle in cervical carcinomas. Using immunofluorescence staining of cyclin A, digital microscopy, and digital image analysis, we determined which cells in a tissue section that were in S- or G2-phase. M-phase cells were detected by morphology. By simultaneously staining for cyclin E, we investigated the variation in cyclin E levels over the cell cycle in cervical carcinoma lesions. In a case-control study, in which each deceased patient was matched with a patient still alive and well after >5 years of follow-up, we found that the deceased patients had a considerably higher fraction of cyclin A-positive cells staining for cyclin E than the survivors (n = 36). We conclude that parallel cyclin E and cyclin A expression is an indicator for poor outcome in cervical carcinomas. In addition, we investigated the expression pattern of cyclin E and cyclin A in consecutive biopsy samples from cervical carcinomas at different stages, as well as in human papillomavirus positive or negative adenocarcinomas in order to further study the cyclin E and cyclin A expression pattern in neoplastic lesions of the uterine cervix.     

Beta-catenin and cyclin D1 expression in human hepatocellular carcinoma

To understand the nature and roles of mutated beta-catenin in human hepatocellular carcinomas (HCCs), 57 cases of surgically resected HCCs were studied. DNAs extracted from each tumor were examined for somatic mutations of exon 3, and the protein expressions of beta-catenin, cyclin D1, and Ki-67 were observed by immunohistochemical staining. beta-catenin mutations in exon 3 were detected in 10 (17.5%) out of 57 HCCs, including nine missense mutations and one deletion mutation. All of the cases with gene alterations had the anti-HCV antibody, and tested negative for the HBs antigen in the sera. All of the mutations occurred at the serine/threonine phosphorylation sites of glycogen synthase kinase-3beta (GSK-3beta) or their neighboring residues. Significant correlation with intracellular expression (p=0.00055) was shown in the HCCs harboring beta-catenin mutations. The intracellular accumulation of beta-catenin showed significant correlation with the cyclin D1 expression (p=0.00858), and with a higher proliferation index (p=0.00072). In addition, the beta-catenin mutations showed significant association with the cyclin D1 expression (p=0.0424). These results suggest that accumulated beta-catenin proteins may bind to the lymphocyte enhancer binding factor-1 (LEF-1), form the beta-catenin/LEF-1 complex, and stimulate such promoters regulating the cell cycle as the cyclin D1 gene. This is the first report to demonstrate a significant correlation between beta-catenin and the cyclin D1 expression in human HCCs.     

大肠癌CDK4、Ki—67表达与CyclinD1、p16蛋白表达的相关性及临床意义

目的探讨CDK4、Ki-67蛋白表达与临床病理因素、预后的关系及其与CyclinD1、p16蛋白表达的关系.方法采用sp法对89例大肠癌标本进行CDK4、Ki-67、CyclinD1、p16蛋白免疫组化检测.结果CDK4核表达在组织学分级Ⅲ级与Ⅰ、Ⅱ级之间的差异有显著性(P<0.05),与术后三年生存率未见明显相关,与CyclinD1、p16蛋白表达明显相关(P<0.05).Ki-67强阳性表达在组织学分级Ⅲ级与Ⅰ、Ⅱ级之间及临床分期D期与B、C期之间的差异有显著性(P<0.05),与术后三年生存率及CyclinD1表达明显相关(P<0.05),与p16蛋白表达无明显相关.CDK4核表达组Ki-67强阳性表达明显增高.结论大肠癌CDK4核表达具有癌基因蛋白的特性,对组织分化及细胞增殖有一定的影响,Ki-67强阳性表达对评估预后、组织分化、临床进展有一定意义.CyclinD1、CDK4与p16共同参与大肠癌的发生与发展.     

大肠癌CDK4、Ki-67表达与Cyclin D1、p16蛋白表达的相关性及临床意义

目的　探讨CDK4、Ki 6 7蛋白表达与临床病理因素、预后的关系及其与CyclinD1、p16蛋白表达的关系。方法　采用sp法对 89例大肠癌标本进行CDK4、Ki 6 7、CyclinD1、p16蛋白免疫组化检测。结果　CDK4核表达在组织学分级Ⅲ级与Ⅰ、Ⅱ级之间的差异有显著性 (P <0 .0 5 ) ,与术后三年生存率未见明显相关 ,与CyclinD1、p16蛋白表达明显相关 (P <0 .0 5 )。Ki 6 7强阳性表达在组织学分级Ⅲ级与Ⅰ、Ⅱ级之间及临床分期D期与B、C期之间的差异有显著性 (P <0 .0 5 ) ,与术后三年生存率及CyclinD1表达明显相关 (P <0 .0 5 ) ,与p16蛋白表达无明显相关。CDK4核表达组Ki 6 7强阳性表达明显增高。结论　大肠癌CDK4核表达具有癌基因蛋白的特性 ,对组织分化及细胞增殖有一定的影响 ,Ki 6 7强阳性表达对评估预后、组织分化、临床进展有一定意义。CyclinD1、CDK4与p16共同参与大肠癌的发生与发展。     

周期蛋白D1在鼻咽癌细胞系中功能及意义的深入研究

目的 深入研究周期蛋白D1在鼻咽癌细胞中的表达特征及生物学功能。以Western blot方法确定D型周期蛋白在鼻咽癌细胞系中的表达谱及表达水平;利用流式细胞术双参数法,确定cyclin D1在鼻咽癌细胞中的表达分布模式;结合反义硫代磷酸化寡聚脱氧核苷酸和抗体剔除实验,分别从mRNA及蛋白质水平抑制、中和cyclinD1的表达,探讨其在鼻咽癌细胞中的生物学功能。结果 在鼻咽癌细胞中,D型周期蛋白的表达谱为D1、D2、D3均表达型,cyclinD1在两株鼻咽癌细胞均有过表达。cyclinD1在鼻咽癌细胞系中的表达呈细胞周期依赖性,在G0／G1期表达最高,S期及G2／M期下降,但仍可检测到。反义cyclinD1硫代磷酸化寡聚脱氧核苷酸和抗体剔除实验可以有效抑制蛋白质表达,抑制细胞进入S期。结论 鼻咽癌细胞系中,D型周期蛋白的表达谱为D1、D2、D3均表达型,cyclinD1在鼻咽癌细胞中有过表达,且表达呈细胞周期依赖性,cyclinD1可能是鼻咽癌细胞G1／S期进行中必不可少的细胞周期调节因子。