Demethylation of HIN-1 reverses paclitaxel-resistance of ovarian clear cell carcinoma through the AKT-mTOR signaling pathway

Review the progression of ovarian clear cell carcinoma from the perspective of genomics and epigenomics

Ovarian clear cell carcinoma (OCCC) is a rare subtype of epithelial ovarian cancer with unique molecular characteristics, specific biological and clinical behavior, poor prognosis and high resistance to chemotherapy. Pushed by the development of genome-wide technologies, our knowledge about the molecular features of OCCC has been considerably advanced. Numerous studies are emerging as groundbreaking, and many of them are promising treatment strategies. In this article, we reviewed studies about the genomics and epigenetics of OCCC, including gene mutation, copy number variations, DNA methylation and histone modifications.

Distinct promotor methylation at tumor suppressive genes in ovarian cancer stromal progenitor cells and ovarian cancer and its clinical implication

Aberrant CpG-island methylation affects ovarian cancer progression. The promotor methylation changes at tumor suppressive genes in ovarian cancer stromal progenitor cells (OCSPCs) and epithelial ovarian cancer (EOC) tissues and their clinical implication remains unexplored. We systemically analyzed the promoter methylation status of 40 tumor suppressor genes (TSGs) associated with cancer in paired epithelial-like and mesenchymal-like OCSPCs and ovarian cancer cells by methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA). The effect of DNA methylation on gene expression was confirmed using qRT-PCR. The differential frequencies of TSGs' promoter methylation among matched epithelial-like or mesenchymal-like OCSPCs from tissues and ascites and ovarian cancer tissues were further validated in cancer tissues and correlated with clinicopathological features and survival outcomes of patients. According to the promoter methylation frequencies of the 40 TSGs, promoters of RASSF1A were the only significantly hypomethylated in epithelial-like OCSPCs from tissues than those from ascites and bulk tumor cells (0% vs 38% vs 45%, P=0.039 by Fisher's exact test). The most frequencies at promotor hypermethylation of TSGs in mesenchymal-like OCSPCs from ascites which processed aggressiveness were CDKN2B (73%) followed by CCND2 (45%) and RASSF1A (45%). Forty-three percent (47/110) of RASSF1A and 45% of CCND2 were validated as a frequently hypermethylated gene in an independent set of 110 EOC tissues in contrast to none (0/60) and 12% (10/60) of benign ovarian cysts (both P<0.001). Functional experiments revealed overexpression of CCND2 or CDKN2B in MSc-OCSPCs decreases EMT, invasion, and spheroid formation in EOC, and abolishes DNMT1 and COL6A3 expression. However, for the expected 5-year overall survival (OS) for patients with methylated RASSF1A, CCND2, and CDKN2B, only RASSF1A was significantly worse than those without methylated RASSF1A (56% vs 80%, p=0.022). Taken together, overexpression of CCND2 and CDKN2B decreased the aggressiveness of mesenchymal-like OCSPCs from ascites which may represent a potential therapeutic target for EOC. Promotor hypomethylation at RASSF1A in OCSPCs from EOC tissues and changes to hypermethylation of EOC and OCSPCs from ascites could predict poor survival outcomes for EOC patients compared to without those changes of CCND2 and CDKN2B.

Targeting Mps1 in combination with paclitaxel inhibits osteosarcoma progression by modulating spindle assembly checkpoint and Akt/mTOR signaling

Osteosarcoma (OS) is the most common malignant bone tumor in children and adolescents and is characterized by early metastasis and frequent recurrence, which greatly affects patient prognosis and survival rates. However, the treatment of OS, its recurrence and subsequent metastasis is now at a clinical bottleneck. To explore new OS chemotherapeutic targets, investigate new therapeutic strategies and improve patient prognosis and survival rates, the roles of paclitaxel (PTX) and monopolar spindle kinase 1 (Mps1) in OS were investigated using in vivo and in vitro models. Mps1 expression was upregulated in OS samples and associated with patient survival times. Moreover, spindle assembly checkpoint (SAC) activation and upregulation of Akt/mTOR signaling were both positively associated with OS progression. PTX treatment significantly inhibited Mps1 expression, as well as migration of OS cells both in vitro. In addition, the combination of Mps1 knockdown and PTX treatment inhibited OS progression in vivo. Mps1 overexpression inhibited the expression of SAC markers and upregulated Akt and mTOR expression, while Mps1 knockdown had the opposite effect. Cells subjected to combined Mps1 knockdown and PTX treatment exhibited activation of SAC and inhibition of Akt/mTOR signaling compared with Mps1 knockdown or PTX treatment alone. Based on these observations, Mps1 inhibition combined with PTX treatment may represent a potentially effective strategy for the treatment of OS.

Collagen type VI regulates the CDK4/6-p-Rb signaling pathway and promotes ovarian cancer invasiveness, stemness, and metastasis

The expression of collagen VI in primary ovarian tumors may correlate with tumor grade and response to chemotherapy. We have sought to elucidate the role of collagen VI in promoting ovarian cancer tumor growth and metastasis. Here we examined the effects of collagen VI on ovarian carcinoma stromal progenitor cells (OCSPCs). Epithelial-like OCSPCs (epi-OCSPCs) and mesenchymal-like OCSPCs (msc-OCSPCs) were analyzed by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). Differentially expressed genes were integrated with survival-related genes using The Cancer Genome Atlas (TCGA) data and confirmed in our samples. The roles of candidate genes and signaling pathways were further explored. We found that SKOV3/msc-OCSPCs possessed greater migration, invasion, and spheroid formation than SKOV3/epi-OCSPCs (P < 0.001). Expression of collagen alpha-3 (VI; COL6A3), which encodes collagen VI, was 90-fold higher in msc-OCSPCs than in epi-OCSPCs. Analysis of TCGA data and our samples indicated that high expression of COL6A3 was correlated with advanced-stage carcinoma (P < 0.01) and shorter overall survival (P < 0.01). In vitro, adding collagen VI, msc-OCSPCs, or knockdown collagen VI in msc-OCSPCs to epithelial ovarian carcinoma (EOC) cells augmented or decreased invasion and spheroid formation. Tumor dissemination to the peritoneal cavity and lung in mice following intraperitoneal coinjection with msc-OCSPCs and SKOV3-Luc cells and intravenous injection with COL6A3 and ES2 cells derived spheroids was significantly greater compare to coinjection with SKOV3-Luc cells alone or in combination with msc-OCSPCs/shCOL6A3 cells and msc-OCSPCs and ES2 derived spheroids. Knockdown of COL6A3 abolished the expression of DNMT1, CDK4, CDK6, and p-Rb in msc-OCSPCs and EOC spheroids. In contrast, overexpression of COL6A3 enhanced the expression of CDK4, CDK6, and p-Rb in SKOV3 cells. EOC spheroid formation, invasion, tumor growth, and metastasis were inhibited when COL6A3 downstream signaling pathway was blocked using CDK4/6 inhibitor LEE011. Our results suggested that collagen VI regulates the CDK4/6-p-Rb signaling pathway and promotes EOC invasiveness, stemness, and metastasis.

Epigenetic agents in combined anticancer therapy

In the last decade, epigenetic drugs (such as inhibitors of DNA methyltransferases and histone deacetylases) have been intensively used for cancer treatment. Their applications have shown high anticancer effectivity and tolerable side effects. However, they are unfortunately not effective in the treatment of some types and phenotypes of cancers. Nevertheless, several studies have demonstrated that problems of drug efficacy can be overcome through the combined application of therapeutic modulates. Therefore, combined applications of epigenetic agents with chemotherapy, radiation therapy, immunotherapy, oncolytic virotherapy and hyperthermia have been presented. This review summarizes and discusses the general principles of this approach, as introduced and supported by numerous examples. In addition, predictions of the future potential applications of this methodology are included.

Identification of genes associated with SiHa cell sensitivity to paclitaxel by CRISPR-Cas9 knockout screening

Although chemotherapy has significantly improved the prognosis of patients with cervical cancer, many patients exhibit selective responses to chemotherapy. This study aimed to identify genes associated with the sensitivity of cervical cancer cells to paclitaxel. SiHa cells were transfected with lentiCRISPR (genome-scale CRISPR knockout library v.2) and then treated with paclitaxel or vehicle for 14 days. Subsequently, we screened for candidate genes whose loss resulted in sensitivity to paclitaxel. We obtained 374 candidates, some of which were consistent with those reported in previous studies, including ABCC9, IL37, EIF3C, AKT1S1, and several members of the PPP gene family (PPP1R7, PPP2R5B, PPP1R7, and PPP1R11). Importantly, our findings highlighted the newly identified genes that could provide novel insights into the mechanisms of paclitaxel sensitivity in cervical cancer. Cas9 technology provides a reliable method for the exploration of more effective combination chemotherapies for patients at the gene level.

Everolimus following 5-aza-2-deoxycytidine is a promising therapy in paclitaxel-resistant clear cell carcinoma of the ovary

Our previous study showed that 5-aza-2-deoxycytidine (5-aza-dC) could inhibit tumor growth by enhancing the susceptibility of ovarian clear cell carcinoma (OCCC) to paclitaxel through decreasing AKT/mTOR expressions. The objective of the study is to evaluate the antitumor efficacy of everolimus (RAD001) and 5-aza-2-deoxycytidine (5-aza-dC) by targeting AKT/mTOR and EZH2 in OCCC. Paclitaxel-sensitive and resistant OCCC cell lines were established. In vitro proliferative and apoptotic assays and flow cytometry were performed. The expressions of EZH2, PIK3IP1, phospho-AKT, phospho-mTOR and phospho-Rictor in the OCCC cell lines were evaluated by Western blotting. In vivo animal experiments with RAD001 and 5-aza-dC were performed. RAD001 alone showed significant in vitro antitumor activity and inhibited in vivo tumor growth in paclitaxel-sensitive and resistant OCCC cells. In addition, 5-aza-dC enhanced the antitumor effects when combined with paclitaxel or RAD001 in both paclitaxel-sensitive and resistant tumors. Activation of phospho-AKT ser473 and PIK3IP1 was observed in RAD001-treated paclitaxel-sensitive and resistant OCCC cells. In contrast, inhibition of phospho-AKT ser473 and EZH2 was observed with RAD001 following 5-aza-dC treatment of paclitaxel-sensitive and resistant OCCC cells. Furthermore, RAD001 following 5-aza-dC enhanced apoptosis of paclitaxel-sensitive and resistant OCCC cells. RAD001 following 5-aza-dC may be a promising treatment strategy for the treatment of both chemo-sensitive and resistant OCCC. Further clinical studies are warranted.

Overexpression of suppressor of IKBKE 1 is associated with vincristine resistance in colon cancer cells

In a previous study, the suppressor of IKBKE 1 expression level was confirmed to be higher in vincristine (VCR)-resistant HCT-8 (HCT-8/V) colon cancer cells than in non-VCR-resistant HCT-8 cells. In the current study, IKBKE 1 expression in VCR-resistant colon cancer cells was investigated further. HCT-8 and HCT-8/V human colon cancer cells were used, and polymerase chain reaction (PCR) primers were designed to amplify the IKBKE 1 gene. Fluorescence reverse transcription-quantitative PCR (RT-qPCR) was performed to detect differences in IKBKE 1 expression between sensitive and drug-resistant colon cancer cell lines. Western blotting was performed to further observe IKBKE 1 expression. Based on the RT-qPCR and western blot results, IKBKE 1 expression was observed to be markedly higher in the HCT-8/V cells, and this difference was significant (P<0.05). Thus, IKBKE 1 expression was identified to be associated with the resistance of colon cancer cells to VCR.