Molecular mechanism underlying the functional loss of cyclindependent kinase inhibitors p16 and p27 in hepatocellular carcinoma

Hepatocellular carcinoma （HCC） is one of the most common human cancers, and its incidence is still increasing in many countries. The prognosis of HCC patients remains poor, and identification of useful molecular prognostic markers is required. Many recent studies have shown that functional alterations of cellcycle regulators can be observed in HCC. Among the various types of cell-cycle regulators, p16 and p27 are frequently inactivated in HCC and are considered to be potent tumor suppressors, p16, a G1-specific cell-cycle inhibitor that prevents the association of cyclindependent kinase （CDK） 4 and CDK6 with cyclin DI, is frequently inactivated in HCC via CpG methylation of its promoter region, p16 may be involved in the early steps of hepatocarcinogenesis, since p16 gene methylation has been detected in subsets of pre-neoplastic liver cirrhosis patients, p27, a negative regulator of the G1-S phase transition through inhibition of the kinase activities of Cdk2/cyclin A and Cdk2/cyclin E complexes, is now considered to be an adverse prognostic factor in HCC. In some cases of HCC with increased cell proliferation, p27 is overexpressed but inactivated by sequestration into cyclin D1-CDK4-containing complexes. Since loss of p16 is closely related to functional inactivation of p27 in HCC, investigating both p16 and p27 may be useful for precise prognostic predictions in individuals with HCC.

Effect of 5-Aza-2'-deoxycytidine on the P16 tumor suppressor gene in hepatocellular carcinoma cell line HepG2

INTRODUCTIONHepatocellular carcinoma (HCC) is one of the mostcommon human malignancies worldwide[1,2], and isclosely associated with infection of HBV and HCVand contamination of aflatoxin B1[3-6]. Althoughthe molecular mechanisms of hepatocarcinogenesisremain poorly understood, an increasing number ofgenetic abnormalities have been recognized[7-10],for example, the p16 gene[11,12] the p53gene[13-18], the E-cadherin gene[19], and the c-mycgene[20].

胰腺癌中Ring1B、LSD1及P16表达及其与预后的关系

目的:探讨胰腺癌中E3泛素连接酶亚单位Ring1B、组蛋白赖氨酸特异性去甲基化酶1(LSD1)及细胞周期调节因子P16表达与及其与患者预后的关系。方法:用免疫组化法检测85例胰腺癌患者手术标本(癌组织与癌旁组织)中LSD1、Ring1B与P16蛋白的表达及分布,并选取其中6对癌组织和癌旁组织,用qRT-PCR和Western blot法检测mRNA和蛋白表达;分析三者在胰腺癌组织中表达的相关性,及其与患者生存的关系。结果:免疫组化结果显示,Ring1B与LSD1蛋白主要表达于细胞浆,P16主要表达于胞核;Ring1B与LSD1在胰腺癌组织中表达明显高于癌旁组织,而P16的表达明显低于癌旁组织(均P<0.05);在胰腺癌组织中Ring1B、LSD1的表达与P16的表达均呈负相关(r=-476;r=-0.673,均P<0.05)。qRTPCR结果显示,胰腺癌组织中Ring1B和LSD1的mRNA的平均相对表达量均明显高于癌旁组织(8.908vs.1.947;7.126 vs.1.940,均P<0.05),P16的mRNA的平均相对表达量明显低于癌旁组织(1.269vs.5.237,P<0.05);Western blot结果显示,三者的蛋白表达趋势与mRNA表达一致。生存分析显示,Ring1B、LSD1高表达患者生存率均分别低于其低表达患者(χ~2=8.958,P=0.012;χ~2=8.856,P=0.010),而P16高表达患者生存率高于其低表达患者(χ~2=7.867,P=0.024)。结论:胰腺癌组织中Ring1B与LSD1表达升高,P16表达降低;Ring1B、LSD1可能分别通过组蛋白泛素化和去甲基化调控P16的表达,从而影响胰腺癌预后。

Effect of cis-9,trans-11-conjugated linoleic acid on cell cycle of gastric adenocarcinoma cell line(SGC-7901)

AIM: To determine the effect of cis -9, trans -11-conjugated linoleic acid (c9, t11-CLA) on the cell cycle of gastric cancer cells (SGC-7901) and its possible mechanism in inhibition cancer growth. METHODS: Using cell culture and immunocytochemical techniques, we examined the cell growth, DNA synthesis, expression of PCNA, cyclin A, B(1), D(1), p16(ink4a) and p21(cip/waf1) of SGC-7901 cells which were treated with various c9, t11-CLA concentrations (25, 50, 100 and 200 micromol.L(-1))of c 9, t 11-CLA for 24 and 48h, with a negative control (0.1% ethane). RESULTS: The cell growth and DNA synthesis of SGC-7901 cells were inhibited by c9, t11-CLA.SGC-7901 cells. Eight day after treatment with various concentrations of c9, t11-CLA mentioned above, the inhibition rates were 5.92%, 20.15%, 75.61% and 82.44%, respectively and inhibitory effect of c9, t11-CLA on DNA synthesis (except for 25 micromol.L, 24h) showed significantly less (3)H-TdR incorporation than that in the negative controls (P【0.05 and P【0.01). Immunocytochemical staining demonstrated that SGC-7901 cells preincubated in media supplemented with different c9, t11-CLA concentrations at various times significantly decreased the expressions of PCNA (the expression rates were 7.2-3.0%, 24h and 9.1-0.9% at 48h, respectively), Cyclin A (11.0-2.3%, 24h and 8.5-0.5%,48h), B(1) (4.8-1.8% at 24h and 5.5-0.6% at 48h)and D(1) (3.6-1.4% at 24h and 3.7%-0 at 48h) as compared with those in the negative controls(the expressions of PCNA, Cyclin A, B(1) and D(1) were 6.5% at 24h and 9.0% at 48h, 4.2% at 24h and 5.1% at 48h, 9.5% at 24h and 6.0% at 48h,respectively)(P【0.01), whereas the expressions of P16(ink4a) and P21(cip/waf1), cyclin-dependent kinases inhibitors(CDKI), were increased. CONCLUSION: The cell growth and proliferation of SGC-7901 cell is inhibited by c9, t11-CLA via blocking the cell cycle, with reduced expressions of cyclin A,B(1) and D(1) and enhanced expressions of CDKI(P16(ink4a) and p21(cip/waf1)).

Expression of positive and negative regulators of cell cycle during wound healing

OBJECTIVE: To detect the expression of cell cycle positive regulators cyclin D(1), cyclin E, CDK(2), CDK(4) and negative regulators p21(cip1), p27(kip1), p16(ink4a) and p15(ink4b) during wound healing in rats. METHODS: Open wounds of full-thickness skin, diameter 1.8 cm, on rat backs were used as the wound model. Wound tissues were harvested on postwounding days 3, 5, 7, 9, 11, 14, 21 and 30. Ki67 expression in granulation tissue was detected by immunohistochemical assay. The patterns of the expression of cyclin D(1), cyclin E, CDK(2), CDK(4) and p21(cip1), p27(kip1), p16(ink4a), p15(ink4b) were detected by Western blot. RESULTS: Cell proliferation in granulation tissue took place predominantly within the first week after injury, with the proliferation peak occurring at postwounding day 5. There were no dramatic variations in the expression of cyclin D(1), CDK(2) and CDK(4) during wound healing. Up-regulated cyclin E was maintained from day 3 to 11 after injury, and then was down-regulated. No expression of p16(ink4a) and p15(ink4b) was found. p21(cip1) was expressed only from day 7 to 14, with peak expression observed on day 9. Constitutive p27(kip1) was expressed throughout wound healing with low levels in the proliferating period of day 3 to 5 and with increased levels in the post-mitotic and remodeling stage. The expression of p21(cip1) and p27(kip1) showed an inverse gradient to that of Ki67. CONCLUSION: p21(cip1) and p27(kip1) play a supervising role in preventing the hyperproliferative tendency in tissue repair.

Epstein-Barr virus induces human nasopharyngeal epithelial cells to escape from the replicative senescence

OBJECTIVE: To observe the biological changes of primary human nasopharyngeal epithelial cells in the early stage of immortalization. METHODS: The morphological changes of nasopharyngeal epithelial cells were observed by phase contrast microscopy, and the activity profile of senescence-associated beta-galactosidase (SA-beta-Gal) was detected by SA-beta-Gal staining. The expression of p16(INK4a) protein was tested by immunochemical assay, and the life span in vitro of nasopharyngeal epithelial cells was calculated as population doublings. In addition, the expression of Epstein-Barr (EB) virus latent membrane protein 1 (LMP1) was also detected by immunofluorescence staining. RESULTS: Morphologically, cells treated with EB virus and 12-o-tetradecanoyl-phorbol-13-acetate (TPA) formed multi-layer foci, and their cellular life span in vitro was extended (about 155 days of culture). A low percentage of cells (about 4.8%) expressed SA-beta-Gal activity at late primary culture, and did not always express p16(INK4a) protein in the progression of culture. CONCLUSIONS: Nasopharyngeal epithelial cells treated with EB virus in cooperation with TPA can pass through the stage of senescence and enter the early stage of immortalization. Some changes of phenotype occur in these cells.Our results provide data for further studying the mechanism of immortalization and the establishment of a human nasopharyngeal epithelial cell line.

Effect of Yanggan Jiedu Sanjie formula on human hepatocellular carcinoma Bel-7402 cells

OBJECTIVE: To observe the effect of Yanggan Jiedu Sanjie(YGJDSJ) formula on human hepatocellular carcinoma Bel-7402 cells.METHODS: Bel-7402 cells were treated with YGJDSJ. Cell proliferation was detected by cell counting kit-8 assay. Cell apoptosis was identified by Hoechst 33258 staining and flow cytometric analysis. Cell cycle distribution was quantified by flow cytometric analysis. Caspase activities were measured by commercial kit. Cell senescence was detected by senescence-associated β-galactosidase(SA-β-gal)staining. Protein expression and phosphorylation were identified by Western blot. Protein expression was knocked-down by siRNA.RESULTS: YGJDSJ inhibited proliferation of Bel-7402 cells in a dose-and time-dependent manner.YGJDSJ induced apoptosis and activated caspase-3, 8, and 9 in Bel-7402 cells. YGJDSJ-induced apoptosis was completely abrogated by a pan caspase inhibitor, Z-VAD-FMK. YGJDSJ also induced cell senescence, up-regulated cyclin-dependent kinase inhibitor 1 a(CDKN1 a) and CDKN2 a expression and down-regulated retinoblastoma protein(RB) phosphorylation in Bel-7402 cells. Specific knockdown of CDKN1 a and CDKN2 a significantly reduced YGJDSJ-induce cell senescence in Bel-7402 cells.CONCLUSION: YGJDSJ inhibited cell proliferation,induced caspase-dependent apoptosis and CDKN1 a/CDKN2 a-RB signalling mediated cell senescence in Bel-7402 cells. Our findings suggest that YGJDSJ might be potential for hepatocellular carcinoma treatment.

CDK4/6抑制剂在乳腺癌中的研究进展

细胞周期的失调是肿瘤生长和转移的典型标志之一,通过CDK抑制剂重新建立细胞周期的调控在肿瘤靶向治疗的发展中已经成为有吸引力的方向。三种选择性靶向CDK4/6的口服药物已经被研发:palbociclib、abemaciclib和LEE011。当前的研究表明CDK4/6抑制剂与内分泌药物联合治疗激素受体阳性乳腺癌是一个新的标准。全文就细胞周期调控、乳腺癌中cyclin D-CDK4/6-Rb途径及相关蛋白p16和survivin的异常表现、CDK4/6抑制剂的相关临床试验及其结果进行总结。