Upregulation of p27Kip1 by demethylation sensitizes cisplatin-resistant human ovarian cancer SKOV3 cells

Platinum-resistant ovarian cancer: From drug resistance mechanisms to liquid biopsy-based biomarkers for disease management

Resistance to platinum-based chemotherapy is a major clinical challenge in ovarian cancer, contributing to the high mortality-to-incidence ratio. Management of the platinum-resistant disease has been difficult due to diverse underlying molecular mechanisms. Over the past several years, research has revealed several novel molecular targets that are being explored as biomarkers for treatment planning and monitoring of response. The therapeutic landscape of ovarian cancer is also rapidly evolving, and alternative therapies are becoming available for the recurrent platinum-resistant disease. This review provides a snapshot of platinum resistance mechanisms and discusses liquid-based biomarkers and their potential utility in effective management of platinum-resistant ovarian cancer.

Effect of 5-aza-2'-deoxycytidine on p27Kip1, p21Cip1/Waf1/Sdi1, p57Kip2, and DNA methyltransferase 1 Genes Expression, Cell Growth Inhibition and Apoptosis Induction in Colon Cancer SW 480 and SW 948 Cell Lines

Background:

Dysregulation of the cell cycle has been reported in various cancers. Inactivation of the cyclin-dependent kinases inhibitors (CDKIs), CIP/KIP family, such as p21Cip1/Waf1/Sdi1, p27Kip1, and p57Kip2 genes because of hypermethylation has been shown in several cancers. Treatment with DNA demethylating agent 5-aza-2ˈ-deoxycytidine (5-Aza-CdR) has been indicated that affect genomic methylation and resulting in silenced genes reactivation in colon cancer. Previously, we evaluated the effect of 5-Aza-CdR on DNA methyltransferase 1 (DNMT1) gene expression in hepatocellular carcinoma (HCC) which encouraged us to design the current study. The present study aimed to evaluate the effect of 5-Aza-CdR on p21Cip1/Waf1/Sdi1, p27Kip1, p57Kip2, and DNAT1 genes expression, cell growth inhibition and apoptosis induction in colon cancer SW 480 and SW 948 cell lines.

Materials and Methods:

The effect of 5-aza-CdR on the SW 480 and SW 948 cells growth, apoptosis induction and genes expression were assessed by MTT assay, flow cytometry, and real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis respectively.

Results:

5-aza-CdR inhibited cell growth as time-and dose-dependent manner significantly (P<0.001). The agent reactivated p15INK4, p16INK4, p18INK4, and p19INK4 genes expression and induced apoptosis at a concentration of 5 μM significantly. Besides, 5-aza-CdR had a more significant effect on the SW 480 cell line in comparison to SW 948 cell line.

Conclusion:

5-Aza-CdR plays a key role in the up-regulation of p21Cip1/ Waf1/Sdi1, p27Kip1, and p57Kip2 and down-regulation of DNMT1 genes resulting in cell growth inhibition and apoptosis induction.

Epigenetics of Most Aggressive Solid Tumors: Pathways, Targets and Treatments

Highly aggressive tumors are characterized by a highly invasive phenotype, and they display chemoresistance. Furthermore, some of the tumors lack expression of biomarkers for target therapies. This is the case of small-cell lung cancer, triple-negative breast cancer, pancreatic ductal adenocarcinoma, glioblastoma, metastatic melanoma, and advanced ovarian cancer. Unfortunately, these patients show a low survival rate and most of the available drugs are ineffective. In this context, epigenetic modifications have emerged to provide the causes and potential treatments for such types of tumors. Methylation and hydroxymethylation of DNA, and histone modifications, are the most common targets of epigenetic therapy, to influence gene expression without altering the DNA sequence. These modifications could impact both oncogenes and tumor suppressor factors, which influence several molecular pathways such as epithelial-to-mesenchymal transition, WNT/β-catenin, PI3K-mTOR, MAPK, or mismatch repair machinery. However, epigenetic changes are inducible and reversible events that could be influenced by some environmental conditions, such as UV exposure, smoking habit, or diet. Changes in DNA methylation status and/or histone modification, such as acetylation, methylation or phosphorylation, among others, are the most important targets for epigenetic cancer therapy. Therefore, the present review aims to compile the basic information of epigenetic modifications, pathways and factors, and provide a rationale for the research and treatment of highly aggressive tumors with epigenetic drugs.

Cell Cycle Regulator p27 Mediates Body Mass Index Effects in Ovarian Cancer in FIGO-stages I-II

BACKGROUND/AIM

The aim of the present study was to evaluate the association between body mass index (BMI), the biomarker p27, and the clinical factors in FIGO-stages I-II ovarian cancer.

PATIENTS AND METHODS

A total of 128 patients with ovarian cancer were included in the study. For testing differences in univariate analyzes we used the Pearson's Chi-square test and the log-rank test. For multivariate analyses the logistic regression and Cox regression models were used with recurrent disease and disease-free survival as endpoints, respectively.

RESULTS

Patients with BMI ≤25 kg/m² had a significantly better 5-year disease-free survival compared with patients with BMI >25 kg/m² in the total series of patients (p=0.008), and in the series of patients (n=77) with non-serous tumors (p=0.047). Patients with p27-positive non-serous tumors had higher survival compared to patients with p27-negative non-serous tumors (p=0.020).

CONCLUSION

The cell cycle regulator p27 mediates BMI effects in ovarian cancer in FIGO-stages I-II.

Low tumour PPM1H indicates poor prognosis in colorectal cancer via activation of cancer-associated fibroblasts

BACKGROUND

Vimentin (VIM) is considered a prognostic marker in colorectal cancer (CRC). Our aim is to identify genes that fulfil a "X-low implies VIM-high" Boolean relationship and to evaluate their prognostic value and potential mechanism.

METHODS

Potential biomarkers related to VIM expression were searched using a bioinformatics approach across gene-expression arrays. Based on subgroup analysis of 2 CRC cohorts, the selected gene was tested for its association with patient's survival outcomes. The regulatory link between the selected gene and VIM was further examined with in vitro models.

RESULTS

PPM1H was identified as the top candidate in our search. Patients with PPM1H-low tumours have a lower 5-year disease-free survival rate than patients with PPM1H-high tumours in 2 independent cohorts. In multivariate Cox analysis, patients with PPM1H-low tumours were independently associated with relapse in both the discovery cohort (hazard ratio [HR], 1.362; 95% confidence interval [CI], 1.015-1.826; P = 0.039) and the validation cohort (HR for DFS, 4.052; 95% CI, 2.634-6.234; P < 0.001). PPM1H knockdown in CRC cells and growth in the corresponding conditional medium increased VIM expression and colon fibroblast proliferation, indicating a transformation of cancer-association fibroblasts (CAFs). Conversely, educated CAFs also facilitated the growth of CRC cells with low PPM1H expression.

CONCLUSIONS

Lack of tumour PPM1H expression identifies a patient subgroup with a high relapse risk, and CRC cells with low expression of PPM1H activate CAFs and inversely get promoted by CAFs.

Gastrin induces multidrug resistance via the degradation of p27Kip1 in the gastric carcinoma cell line SGC7901

Multidrug resistance (MDR) is one of the major reasons for the failure of chemotherapy-based gastric carcinoma (GC) treatments, hence, biologically based therapies are urgently needed. Gastrin (GAS), a key gastrointestinal (GI) hormone, was found to be involved in tumor formation, progression, and metastasis. In this study, quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical staining analysis revealed a high level of expression of GAS in drug-insensitive GC tissues (P<0.01) and similar results were revealed in GC cell lines SGC7901 and its multidrug-resistant variants SGC7901/VCR and SGC7901/ADR. We constructed a eukaryotic expression vector pCDNA3.1(+)/GAS for GAS overexpression and recombinant lentiviral vectors for specific siRNA (siGAS). Transfection of pCDNA3.1(+)/GAS increased (P<0.05) while transfection of siGAS (P<0.05) and co-treated with paclitaxel (TAX) and vincristine (VCR) combination (TAX-VCR) decreased (P<0.01) the cell viability of SGC7901, SGC7901/VCR and SGC7901/ADR. Apoptosis rates of SGC7901/VCR and SGC7901/ADR were reduced by pCDNA3.1(+)/GAS and increased by siGAS (P<0.05). The apoptosis rates of SGC7901/VCR, SGC7901/ADR and SGC7901 were all upregulated (P<0.01) when cells were co-treated with a combination of siGAS and TAX-VCR. Additionally, siGAS significantly downregulated the expression of Bcl-2 and multidrug-resistant associate protein (MRP1) and P-glycoprotein (Pgp) (P<0.05) in SGC7901/VCR and SGC7901/ADR cells. Moreover, GAS overexpression in SGC7901 cells significantly inhibited p27Kip1 expression but increased phosphorylation levels of p27Kip1 on Thr (187) and Ser (10) sites (P<0.05), as well as increasing nuclear accumulation of S-phase kinase-associated protein 2 (Skp2) and cytoplasmic accumulation of the Kip1 ubiquitination-promoting complex (KPC) (P<0.05). Silencing of Skp2 blocked the promoting effects of pCDNA3.1(+)/GAS on viability, the expression of MRP1 and Pgp and the inhibitory effects of pCDNA3.1(+)/GAS on apoptosis. In conclusion, we suggest that GAS contributes to the emergence of MDR of SGC7901 cells via the degradation of p27Kip1.

A systems biology approach to identify microRNAs contributing to cisplatin resistance in human ovarian cancer cells

The dysregulated microRNAs contribute to cisplatin resistance in ovarian cancer cells.