Tribbles 2 mediates cisplatin sensitivity and DNA damage response in epithelial ovarian cancer

Aim was to identify methylated genes with functional involvement in cisplatin‐resistance development of epithelial ovarian cancer (EOC). Genome‐wide analyses of hypermethylated CpG‐islands in resistant cell lines in combination with qRT‐PCR analyses were used to identify epigenetically silenced genes. EOC‐Type‐II tumors were analyzed for gene methylation and expression and TCGA data were interrogated in‐silico. Experiments revealed 37 commonly hypermethylated genes in resistant cells of which Tribbles 2 (TRIB2) showed the most pronounced downregulation on mRNA level and was characterized further. TRIB2 showed a reactivation after 5′‐Aza‐Cytidine treatment in resistant cells but a cisplatin‐dependent, prominent upregulation on mRNA level in sensitive cells, only. Re‐expression in resistant A2780 cells increased the sensitivity to cisplatin and other DNA‐damaging agents, but not taxanes. Contrary, knockdown of TRIB2 increased resistance to cisplatin in sensitive cells. TRIB2 was involved in the induction of a cisplatin‐dependent cell cycle arrest and apoptosis by influencing p21 and survivin expression. An increased Pt‐DNA‐adduct formation in TRIB2 re‐expressing cells did not translate in higher levels of dsDNA damage (yH2AX‐foci). Thus, TRIB2 is potentially involved in the signal transduction from nucleotide excision repair of intrastrand cross links. Importantly, patient stratification of two homogenous cohorts of EOC‐Type‐II patients from Jena (n = 38) and the TCGA (n = 149) by TRIB2 mRNA expression consistently revealed a significantly decreased PFS for patients with low TRIB2 levels (log‐rank p < 0.05). Tumors from resistant patients expressed the lowest levels of TRIB2. Downregulation of TRIB2 contributes to platin‐resistance and TRIB2 expression should be validated as prognostic and predictive marker for EOC.     

hMS H2重组质粒对人卵巢癌细胞顺铂敏感性的影响

目的：研究hMSH2重组质粒对卵巢癌顺铂敏感性方面的影响。方法：构建重组真核表达质粒pCAN－hMSH2,通过酶切及测序法对重组质粒进行鉴定。采用脂质体转染技术对卵巢癌耐药细胞SKOV3／DDP进行瞬时转染,对照组为未转染细胞和SKOV3敏感细胞;hMSH2在细胞内的表达变化由Western blotting和RT－PCR进行检测;四甲基偶氮唑蓝（MTT）法对细胞的顺铂敏感性进行检测;耐药细胞的凋亡情况通过Hoechst染色法检测。结果：重组质粒pCAN－hMSH2转染进SKOV3／DDP后,经RT－PCR和Western blotting检测证实转染成功,hMSH2的表达得到增强;MTT结果提示转染后的卵巢癌耐药细胞对顺铂的敏感性明显增强;Ho-echst染色发现,转染后耐药细胞的凋亡明显增强。结论：hMSH2基因转染后能提高其在SKOV3／DDP细胞中的表达,增强SKOV3／DDP细胞对顺铂的敏感性,促进在顺铂作用下的凋亡。     

外源性p53基因增加卵巢癌细胞对顺铂的敏感性

 目的 探讨外源性ｐ５３基因转染对人卵巢癌细胞株的化疗敏感性的影响。方法用脂质体介导的转染技术，将人野生型ｐ５３基因的真核表达载体导入不表达ｐ５３的卵巢癌ＳＫＯＶ－３细胞中，经Ｇ４１８筛选，Ｎｏｒｔｈｅｒｎｂｌｏｔ及Ｗｅｓｔｅｒｎｂｌｏｔ鉴定后，观察其对顺铂作用后的 ＳＫＯＶ－３细胞的集落形成及凋亡的影响。结果 外源性Ｐ５３基因在转染细胞中有效表达，并增强了顺铂对ＳＫＯＶ－３细胞集落形成的抑制作用及促进了顺铂诱导的细胞凋亡。结论 外源性ｐ５３基因能增加卵巢癌细胞对顺铂的敏感性，两者联合作用能更大程度地杀灭肿瘤细胞。     

The kinase RSK2 modulates the sensitivity of ovarian cancer cells to cisplatin

Platinum-based chemotherapy (e.g. cisplatin, carboplatin) is standard of care for many types of cancer including ovarian cancer, however, the efficacy of treatment is hampered by the development of therapy resistance. The mechanisms behind platinum resistance are not completely understood. Here, we have investigated the role of the family of p90 Ribosomal S6 kinases (RSK), important downstream mediators of ERK1/2, in the response to cisplatin chemotherapy. Strikingly, whereas treatment with cisplatin did not alter the levels of RSK1 in response to cisplatin treatment, the structurally related RSK2 protein was downregulated in an ovarian cancer cell line (A2780). Furthermore, we found that knockdown of RSK2, in contrast to knockdown of RSK1, gave rise to enhanced cisplatin sensitivity in a cisplatin sensitive as well as a cisplatin-resistant A2780 cell line. These results indicate that RSK2 is regulated in response to cisplatin treatment, and this downregulation may contribute to the cytotoxic action of cisplatin. Since RSK2 is frequently amplified in a growing number of cancers, this may have implications for the sensitivity of these tumours to platinum-based cytotoxics.     

Metallothionein gene expression and resistance to cisplatin in human ovarian cancer

Intracellular thiols have been proposed as mediators of resistance to alkylating agents and cisplatin. As metallothionein is the predominant protein thiol, we examined its relationship to cisplatin resistance in human ovarian cancer cell lines. A human ovarian carcinoma cell line, A2780, derived from an untreated patient, was treated with cisplatin in several ways and the induced resistance to cisplatin ranged from 13- to 68-fold. The degree of resistance was dependent upon the method of selection. The drug-resistant cell lines also developed low levels of cross-resistance to cadmium. Additional cell lines established from untreated patients or ovarian cancer patients refractory to cisplatin- and/or carboplatin-containing combination chemotherapy were studied. The most cisplatin-resistant cell lines, OVCAR-8 and -10, were from patients previously treated with intensive chemotherapy. OVCAR-8 was relatively cross-resistant to cadmium while OVCAR-10 appeared relatively sensitive. Cell lines were examined for expression of metallothionein mRNA to evaluate the relationship between cisplatin resistance, cadmium cross-resistance and metallothionein expression. Only two of the cell lines with in vitro-induced resistance to cisplatin, 2780E80 and 2780CP70B3, had detectable metallothionein mRNA. The other cell lines selected in vitro for cisplatin resistance, as well as the parental A2780 ovarian cancer cell line, showed no expression at our level of detection. There was variable expression of metallothionein among the OVCAR cell lines. Cell lines from untreated patients, OVCAR-5 and -7, did express metallothionein, while the most cisplatin-resistant cell lines, OVCAR-8 and -10, did not. We also examined cisplatin induction of metallothionein mRNA in the cell lines. Only 2780CP70B3 among the cell lines with in vitro-induced cisplatin resistance showed increased expression after short-term exposure to cisplatin. OVCAR-4 also had a slight increase in expression after exposure to cisplatin. Mouse C127 cells transfected with a bovine papilloma virus-metallothionein gene construct were compared for cisplatin sensitivity to the same cell type transfected with bovine papilloma virus alone. In this model system, metallothionein expression did not influence cisplatin cytotoxicity. On the basis of these studies, we conclude that there is no causal relationship between metallothionein expression and cisplatin resistance.     

Intraoperative intraperitoneal chemotherapy with cisplatin in epithelial ovarian cancer

Objective

To assess retrospectively the feasibility of intraoperative intraperitoneal (IP) chemotherapy with cisplatin in epithelial ovarian cancer.

Methods

IP chemotherapy during optimal staging surgery was performed in 10 patients who were diagnosed with primary epithelial ovarian cancers between April 2008 and February 2011. Cisplatin (70 mg/m² in 1 L normal saline solution) was administered in the abdominal cavity for 24 hours postoperatively and then adjuvant chemotherapy was started 2-4 weeks after surgery. Perioperative toxicity of the combined treatment was evaluated until the initiation of postoperative adjuvant chemotherapy.

Results

A total of 23 adverse events were observed in 9 of 10 patients (grade 1, 7; grade 2, 13; grade 3, 3; grade 4, 0). In descending order of frequency, adverse events affected the gastrointestinal system (n=14), hematologic system (n=6), pulmonary system (n=2), and genito-urinary system (n=1). The adverse events did not affect adjuvant systemic chemotherapy schedules. One patient experienced disease recurrence in the liver 16 months after surgery. The remaining 9 patients have been well controlled by chemotherapy and/or observation during the follow-up period of 4 to 39 months after surgery.

Conclusion

Intraoperative IP chemotherapy with cisplatin during surgical procedures is considered feasible for the treatment of primary epithelial ovarian cancer. Further studies, including long-term, prospective and comparative trials, are needed to validate the efficacy of this combined therapy.     

原发性上皮性卵巢癌组织中c-erbB2基因扩增及其临床意义

目的检测原发性上皮性卵巢癌组织中ｃｅｒｂＢ２基因扩增,以探讨其在卵巢癌临床诊治中的价值。方法采用Ｓｏｕｔｈｅｒｎ印迹技术,结合特异性ｃｅｒｂＢ２探针,对１０８例原发性上皮性卵巢癌及３４例良性、７例交界性卵巢肿瘤手术切除组织做ＤＮＡ扩增。结果原发性上皮性卵巢癌ｃｅｒｂＢ２基因扩增频率为３２．４％（３５／１０８）,而良性、交界性卵巢肿瘤均未出现扩增（Ｐ＜０．００１）,且ｃｅｒｂＢ２基因的扩增和上皮性卵巢癌的ＦＩＧＯ分期（Ｐ＝０．０２５）、肿瘤细胞分化程度（Ｐ＝０．０１１）及初次手术后残存肿瘤的大小（Ｐ＜０．００１）呈正相关。经对８４例ＩＩ～ＩＶ期原发性上皮性卵巢癌进行预后分析,结果表明,ｃｅｒｂＢ２基因扩增为影响预后的独立因素,ｃｅｒｂＢ２基因扩增阴性者３年生存率为５７．７％,而阳性者为２８．４％,两者差异具有显著性（Ｐ＝０．０１６）。结论ｃｅｒｂＢ２基因扩增可能和原发性上皮性卵巢癌的发生有关,ｃｅｒｂＢ２基因扩增阳性患者恶性程度高,手术成功率低,预后明显差于阴性患者。检测癌组织中ｃｅｒｂＢ２基因的扩增,将有助于对卵巢癌患者的病情监测和预后判断。     

Inhibition of FGFR2 and FGFR1 increases cisplatin sensitivity in ovarian cancer

Fibroblast Growth Factors (FGFs) have been implicated in malignant transformation, tumor mitogenesis, angiogenesis and chemoresistance. The aim of this study was to determine which FGFs and FGFRs play functional roles in epithelial ovarian cancer. Restriction enzyme analysis of mRNA revealed that transformation was associated with a switch in FGFR2 and FGFR3, from the IIIc to the IIIb isoform. There was widespread expression of FGFs, including FGF7, in all tissues but, FGF3 and FGF19 were expressed by malignant cell lines and cancer tissue but were not present in normal tissue. Using FGFR-specific shRNAi we demonstrated that reductions in FGFR2 inhibited proliferation of ovarian cancer cell lines in vitro (>50%, p < 0.006) and reduced cisplatin IC₅₀ (>60%, p < 0.0001). Cell cycle analysis revealed increased cisplatin sensitivity was associated with increased G2/M arrest and increased apoptosis. FGFR2 shRNAi reduced growth rates of ovarian tumor xenografts by 20% (p < 0.006) and when combined with cisplatin caused a 40% reduction in proliferation rates (p < 0.007). In contrast, RNAi-induced reductions in FGFR1 increased SKOV3 cell numbers, with associated changes in cell cycle but had no effect on ES 2 cells. However, the cisplatin IC₅₀ was reduced (>50%, p < 0.0001) by FGFR1 shRNAi in both cell lines and there was increased apoptosis (46–50%) compared with control cells (35%) (p < 0.004). Together our data suggest that combining FGFR2 inhibitors with platinum-containing cytotoxic agents for the treatment of epithelial ovarian cancer may yield increased antitumor activity. However, data on the inhibition of FGFR1 suggest that broad spectrum FGFR inhibitors may have unexpected effects on proliferation.Key words: ovarian cancer, fibroblast growth factor, fibroblast growth factor receptor, shRNAi, cisplatin     

CDKN2A gene inactivation in epithelial sporadic ovarian cancer.

The tumour suppressor gene CDKN2A, located on chromosome 9p21, encodes the cell cycle regulatory protein p16. Inactivation of the CDKN2A gene could lead to uncontrolled cell growth. In order to determine the role of CDKN2A in the development of sporadic ovarian cancer, loss of heterozygosity at 9p21-22, homozygous deletion, mutation and methylation status of the CDKN2A gene as well as CDKN2A expression were examined in a panel of serous papillary ovarian cancer. The frequency of loss of heterozygosity (LOH) for one or more informative markers at 9p21-22 was 65% (15/23). The most common deleted region was located between interferon (IFN)-alpha and D9S171. Homozygous deletions and mutations of the CDKN2A gene were not found. There was no evidence of methylation in exon 1, but methylation in exon 2 of CDKN2A gene was found in 26% (6/23). Absence of CDKN2A gene expression was shown in 27% (6/22) at mRNA level and 21% (4/19) at protein level. These data suggest that the CDKN2A gene is involved in the tumorigenesis of ovarian cancer, but the mechanisms of CDKN2A gene inactivation in serous papillary ovarian cancer remains unclear.     

Overexpression of DDB2 enhances the sensitivity of human ovarian cancer cells to cisplatin by augmenting cellular apoptosis

Cisplatin is one of the most widely used anticancer agents, displaying activity against a wide variety of tumors. However, development of drug resistance presents a challenging barrier to successful cancer treatment by cisplatin. To understand the mechanism of cisplatin resistance, we investigated the role of damaged DNA binding protein complex subunit 2 (DDB2) in cisplatin‐induced cytotoxicity and apoptosis. We show that DDB2 is not required for the repair of cisplatin‐induced DNA damage, but can be induced by cisplatin treatment. DDB2‐deficient noncancer cells exhibit enhanced resistance to cell growth inhibition and apoptosis induced by cisplatin than cells with fully restored DDB2 function. Moreover, DDB2 expression in cisplatin‐resistant ovarian cancer cell line CP70 and MCP2 was lower than their cisplatin‐sensitive parental A2780 cells. Overexpression of DDB2 sensitized CP70 cells to cisplatin‐induced cytotoxicity and apoptosis via activation of the caspase pathway and downregulation of antiapoptotic Bcl‐2 protein. Further analysis indicates that the overexpression of DDB2 in CP70 cells downregulates Bcl‐2 expression through decreasing Bcl‐2 mRNA level. These results suggest that ovarian cancer cells containing high level of DDB2 become susceptible to cisplatin by undergoing enhanced apoptosis.     

Aberrant DNA methylation of T-cell leukemia, homeobox 3 modulates cisplatin sensitivity in bladder cancer

The development of resistance to cisplatin during treatment of bladder cancer constitutes a major obstacle to curing bladder cancer. The identification of epigenetic biomarker molecules for cisplatin resistance and the elucidation of the function of the identified genes in bladder cancer will provide useful information. We found that the candidate gene TLX3 was unmethylated in cisplatin sensitive cells and methylated in resistant cells. The suppression of TLX3 expression using TLX3-specific shRNA in parental cells increased cisplatin resistance. Contrarily, overexpression of TLX3 in resistant cells induced increased sensitivity to cisplatin. We found that 22 (21%) out of 110 clinical samples of bladder cancer showed the methylated pattern using the COBRA assay in TLX3. We found a correlation between TLX3 methylation and the sensitivity to cisplatin in the clinical samples by SDI test. Cisplatin sensitivity was closely associated with the methylation status of TLX3. These findings showed that the TLX3 methylation may be useful as a novel biomarker for cisplatin resistance and can be used to design therapies to counteract the resistance against cisplatin in bladder cancer.     

PAFR对卵巢癌细胞顺铂敏感性的影响及机制研究

背景与目的：目前卵巢癌的治疗方式仍是手术及术后辅助铂类药物为主的化疗,但复发率高,容易耐药。前期研究已证实血小板活化因子受体（platelet-activating factor receptor,PAFR）在上皮性卵巢癌中高表达,且能促进卵巢癌细胞增殖、侵袭及转移。探索顺铂（cisplatin,CDDP）作用后卵巢癌细胞中PAFR的表达变化及其对卵巢癌细胞CDDP敏感性的影响,并对其机制进行初步探讨,旨在为卵巢癌靶向治疗及克服CDDP耐药提供新方法。方法：采用蛋白质印迹法（Western blot）及实时荧光定量聚合酶链反应（real-time fluorescence quantitative polymerase chain reaction,RTFQ-PCR）检测不同浓度的CDDP作用于卵巢癌细胞株（SKOV-3和CAOV-3）不同时间后各组细胞PAFR的表达情况。采用Western blot及免疫荧光法验证CDDP作用于卵巢癌细胞后核因子κB（nuclear factor Kappa-B,NF-κB）/p65及缺氧诱导因子-1α（hypoxia inducible factor-1α,HIF-1α）的表达。采用Western blot及RTFQ-PCR检测小RNA干扰沉默NF-κB及HIF-1α后PAFR的表达情况。采用细胞增殖和凋亡实验检测抑制PAFR表达后对卵巢癌细胞CDDP敏感性的影响。采用Western blot验证CDDP和（或）PAFR抑制剂作用细胞后下游信号通路关键分子P70S6K/AKT/ERK的变化情况。结果：CDDP能够引起卵巢癌细胞中PAFR表达升高,并呈现剂量及时间依赖性（P＜0.01）。CDDP能够引起转录因子NF-κB及HIF-1α的核聚集,沉默NF-κB及HIF-1α后,CDDP诱导的PAFR表达下降。PAFR特异性小分子拮抗剂WEB2086或RNA干扰抑制PAFR表达均能显著提高卵巢癌细胞对于CDDP的敏感性,即细胞增殖能力明显降低（P＜0.01）,而凋亡率明显升高（P＜0.01）。CDDP作用于卵巢癌细胞后,表达升高的PAFR能够激活下游的AKT及ERK信号通路分子。结论：CDDP作用于卵巢癌细胞后能够引起转录因子NF-κB及HIF-1α的核聚集从而上调PAFR的表达。抑制PAFR表达能够增加卵巢癌细胞对CDDP的敏感性,可能成为卵巢癌靶向治疗的新方法。     

miR-483-5p在上皮性卵巢癌中的表达及其对顺铂敏感性的影响

背景与目的：顺铂是目前临床上治疗上皮性卵巢癌的一线化疗药物之一,但许多患者对铂类药物耐药。miR-483-5p在肺癌中过表达,然而目前尚未见miR-483-5p在上皮性卵巢癌中的研究。该研究检测miR-483-5p在上皮性卵巢癌组织和上皮性卵巢癌细胞系中的表达并探讨其对上皮性卵巢癌细胞对顺铂敏感性的影响。方法：采用实时荧光定量聚合酶链反应(real-time fluorescent quantitative polymerase chain reaction,RTFQ-PCR)检测43例上皮性卵巢癌患者的肿瘤组织、8例正常卵巢组织和5种上皮性卵巢癌细胞系中miR-483-5p的表达情况;通过慢病毒上调或敲低卵巢癌细胞miR-483-5p表达,应用CCK-8实验检测miR-483-5p对上皮性卵巢癌细胞系顺铂敏感性的影响。结果：上皮性卵巢癌组织中miR-483-5p表达明显高于正常卵巢组织(P<0.01)。此外,miR-483-5p在晚期上皮性卵巢癌组织中的表达水平显著高于早期肿瘤组织(P<0.05)。5种上皮性卵巢癌细胞系中SKOV3细胞表达miR-483-5p的量最低;miR-483-5p在上皮性卵巢癌顺铂耐药A2780/CP细胞中表达量最高。上调SKOV3细胞中miR-483-5p的表达能够降低上皮性卵巢癌细胞对顺铂的敏感性,并下调p21及Bcl-2的表达;下调A2780/CP细胞miR-483-5p的表达能够增加细胞对顺铂的敏感性,并上调p21及Bcl-2的表达。结论：miR-483-5p在上皮性卵巢癌组织中高表达并对顺铂耐药,可以作为临床预测上皮性卵巢癌对顺铂敏感性的生物标志物之一。     

溶血磷脂酸抑制顺铂诱导的卵巢癌细胞凋亡

目的：探讨溶血磷脂酸（lysophosphatidic acid,LPA）对顺铂诱导的卵巢癌细胞凋亡的抑制作用及其作用机制。方法：体外培养卵巢癌细胞株SKOV3,采用MTT法检测LPA对顺铂（cisplatin,DDP）作用后卵巢癌细胞株SKOV3增殖活性的影响,Hoechst33258荧光染色观察凋亡细胞,用FCM法分析细胞周期变化和细胞凋亡率,DNA片段凝胶电泳观察凋亡细胞的DNA“梯状”条带,免疫细胞化学法及RT-PCR法分别检测细胞凋亡相关蛋白及其mRNA的表达。结果：LPA能降低DDP对SKOV3细胞生长的抑制作用,同时增加G0/G1期细胞比例,降低S期细胞比例和凋亡率。Hoechst33258染色检测示LPA作用后凋亡小体明显减少。DNA片段凝胶电泳示LPA作用后不产生明显的凋亡片段。10μmol/L的LPA作用SKOV3细胞48h后,bcl-2基因及其蛋白表达水平升高,而bax基因及其蛋白表达水平降低（P〈0.01）。结论：LPA可通过上调bcl-2基因及蛋白表达,下调bax基因及蛋白表达,抑制DDP诱导的卵巢癌细胞凋亡。因此,针对LPA的治疗有望提高DDP疗效,改善卵巢癌患者的预后。     

TSA增强人卵巢癌顺铂耐药株C13对顺铂敏感性的体外研究

目的：本研究探讨组蛋白去乙酰化酶抑制剂triChoStatin A（TSA）联合化疗药物顺铂（DDP）处理人卵巢癌顺铂耐药株C13＊的协同效应。方法：MTT法观察TSA、DDP、TSA＋DDP对C13＊细胞增殖的影响；克隆形成实验分别检测DDP、TSA＋DDP处理C13＊的克隆形成率；流式细胞仪检测凋亡和分析细胞周期；Hochest33258观察凋亡细胞形态。结果：40nmol／L TSA处理C13＊12h，细胞的凋亡率为2．99％，MTT显示生长未受明显影响；TSA＋DDP组较DDP组C13＊对DDP的作用更为敏感，在DDP为20～30μmol／L时差异显著（P〈0．05）。结论：一定浓度的TSA和DDP联合应用可以增强人卵巢癌顺铂耐药株C13＊对顺铂的敏感性。     

The Effect of the MDM2-p53 Loop on the Sensitivity of Ovarian Cancer Cells to Cisplatin

OBJECTIVE To explore whether MDM2 transfection can alter the MDM2-p53 autoregulatory feedback loop so as to change the sensitivity of ovarian cancer cell lines to cisplatin. METHODS The ovarian cancer cell line A2780 expressing wild-type P53 and the ovarian cancer cell line SKOV-3 with the p53 null type were stably transfected with pCMV-MDM2 or pCMV as a control. The blocked expression of P53 was determined by Western blots. Cytotoxicity was assessed using the MTT assay and the trypan blue exclusion assay. Flow cytometry was used to detect changes in the cell cycle and removal of platinum -DNA adducts was measured by atomic absorption spec-troscopy. RESULTS (1) Parental A2780 and A2780-V cells (IC50= 15.14±1.39 μmol) have similar cisplatin sensitivities, whereas sensitivity to cisplatin in A2780-M cells (IC50=7.98±1.32 μmol) was 2 to 3 fold greater (P=0.001). The trypan blue exclusion assay demonstrated that cisplatin killed a higher percentage of A2780-M cells compared to A2780-V cells. There was no significant change following MDM2 transfection in SKOV-3 cells. (2) After cisplatin treatment, A2780-M cells showed a pronounced S-phase arrest, however, A2780 cells with the intact wild-type P53, arrested primarily at the G2/M transition. (3) Platinum uptake was similar for all of the A2780 cell lines after ciaplatin treatment, but the removal of plat-inum-DNA adducts was reduced in the A2780-M cells compared with A2780-V cells. CONCLUSION MDM2 increases cisplatin cytotoxicity in ovarian cancer cells by blocking the expression of p53 through the MDM2-p53 autoregulatory feedback loop.