CHD4 regulates platinum sensitivity through MDR1 expression in ovarian cancer: A potential role of CHD4 inhibition as a combination therapy with platinum agents

Platinum sensitivity is an important prognostic factor in patients with ovarian cancer. Chromodomain-helicase-DNA-binding protein 4 (CHD4) is a core member of the nucleosome remodeling and deacetylase complex, which functions as a chromatin remodeler. Emerging evidence indicates that CHD4 could be a potential therapeutic target for cancer therapy. The purpose of this study was to clarify the role of CHD4 in ovarian cancer and investigate its therapeutic potential focusing on platinum sensitivity. In an analysis of the Cancer Genome Atlas ovarian cancer dataset, CHD4 gene amplification was associated with worse overall survival. CHD4 mRNA expression was significantly higher in platinum-resistant samples in a subsequent clinical sample analysis, suggesting that CHD4 overexpression conferred platinum resistance to ovarian cancer cells, resulting in poor patient survival. In concordance with these findings, CHD4 knockdown enhanced the induction of apoptosis mediated by cisplatin in ovarian cancer cells TOV21G and increased cisplatin sensitivity in multiple ovarian cancer cells derived from different subtypes. However, CHD4 knockdown did not affect the expression of RAD51 or p21, the known targets of CHD4 in other cancer types that can modulate platinum sensitivity. Knockdown and overexpression assays revealed that CHD4 positively regulated the expression of multi-drug transporter MDR1 and its coding protein p-glycoprotein. In addition, a first-in-class CHD4/SMARCA5 inhibitor ED2-AD101 showed synergistic interactions with cisplatin. Our findings suggest that CHD4 mediates platinum sensitivity by modulating MDR1 expression in ovarian cancer. Further, CHD4 suppression has a potential to be a novel therapeutic strategy in combination with platinum agents.

Expression of multidrug resistance marker MDR1 in patients with ovarian cancer and its possible predictive significance.

e17530 Background: Despite the progress made in diagnosis and treatment, ovarian cancer (OC) is still the third most common genital cancer. Poor results of therapy for various forms of OC stimulate the search for fundamentally new approaches to the treatment. One of the main reasons for resistance to chemotherapeutic agents includes multidrug resistance (MDR) of tumor cells. The most characterized of its various mechanisms is the elevated activity of the ABC family protein - ABCB1 (Pgp or MDR1). The purpose of the study was evaluation of the expression of this ABC transporter as a predictive factor in platinum-containing chemotherapy in OC patients. Methods: 100 patients aged 29-79 years with advanced stage IIIC - IV OC with/without ascites were recruited between 2016 and 2020. Depending on the treatment results, patients were divided into 2 groups: group 1 (n = 59) - patients with platinum sensitivity; group 2 (n = 41) - patients with platinum resistance during the treatment or within 6 months after its completion. IHC analysis was performed using rabbit polyclonal anti-MDR1 antibodies (Affinity Biosciences) diluted 1:600 and the Reveal Polyvalent HRP-DAB Detection System. The percentage and the intensity of staining were assessed: 0, 1+ weak, 2+ moderate, 3+ strong. MDR1 expression was considered positive when staining was detected in more than 10% (cut-off) tumor cells with intensities of 2+ and 3+. Statistical analysis of results was performed in the Statistica 13.0 program (StatSoftInc., USA). Results: Patients with MDR1+ prevailed in group 2 (98%), and patients with MDR1- in group 1 (32%). The average expression of MDR1 in tumor cells in group 2 (64.0±7.0) was statistically significantly higher by 1.7 times (p = 0.003) than in group 1 (37.2±6.8) by the Mann-Whitney U-test. When distributed according to Pearson's χ2 criterion, positive MDR1 as a risk factor in the platinum-resistant group increased the risks of refractory to platinum therapy by 19 times (95% CI 2.4-148.8). Conclusions: The study demonstrated predictive significance of the MDR1 biomarker in platinum treatment in patients with ovarian cancer.

MiR-200c Sensitizes Breast Cancer Cells to Carboplatin Treatment by Decreasing MDR1 Expression

Background: Breast cancer (BC) is one of the most common cancers worldwide and is associated with a high rate of cancer mortality in women. Resistance to chemotherapy is considered a significant problem and a major challenge for the treatment of patients with BC. miR-200c belongs to a family of miRNAs that act as tumor inhibitors. The expression level of miR-200c has been reported to be decreased in cancers, especially in BC. The increased miR-200c expression can be considered as a potent inhibitor of drug resistance and tumor progression. Methods and Results: The current study examined the effect of miR-200c on enhancing the BC cells' sensitivity to Carboplatin through targeting MDR1 expression. To perform functional analyses, mimic miR-200c transfected to MCF7 cells. Then, the viability of the cells was investigated via MTT assay. Finally, the expression of associated genes assessed using qRT-PCR. The results indicated that downregulation of miR-200c was occurred in MCF7 cells in comparison to control. Besides, restoring miR-200c expression by regulating the expression level of the apoptotic gene reduces the viability of cancer cells. Moreover, miR-200c increased the sensitivity of MCF7 cells to Carboplatin via reducing the MDR1 gene expression. Conclusions: This study provided valuable data showing that miR-200c enhances the effect of carboplatin as a clinically approved chemotherapeutic agent, and restoring its expression could be considered as a promising targeted adjuvant therapy for BC management.

M2 Macrophages Infiltrating Epithelial Ovarian Cancer Express MDR1: A Feature That May Account for the Poor Prognosis

Multi drug resistance protein 1 (MDR1) expression on tumor cells has been widely investigated in context of drug resistance. However, the role of MDR1 on the immune cell infiltrate of solid tumors remains unknown. The aim of this study was to analyze the prognostic significance of a MDR1+ immune cell infiltrate in epithelial ovarian cancer (EOC) and to identify the MDR1+ leucocyte subpopulation. MDR1 expression was analyzed by immunohistochemistry in 156 EOC samples. In addition to MDR1+ cancer cells, we detected a MDR1+ leucocyte infiltrate (high infiltrate >4 leucocytes per field of view). Correlations and survival analyses were calculated. To identify immune cell subpopulations immunofluorescence double staining was performed. The MDR1+ leucocyte infiltrate was associated with human epidermal growth factor receptor 2 (HER2) (cc = 0.258, p = 0.005) and tumor-associated mucin 1 (TA-MUC1) (cc = 0.202, p = 0.022) expression on cancer cells. A high MDR1+ leucocyte infiltrate was associated with impaired survival, especially in patients whose carcinoma showed either serous histology (median OS 28.80 vs. 50.64 months, p = 0.027, n = 91) or TA-MUC1 expression (median OS 30.60 vs. 63.36 months, p = 0.015, n = 110). Similar findings for PFS suggest an influence of MDR1+ immune cells on the development of chemoresistance. A Cox regression analysis confirmed the independency of a high MDR1+ leucocyte infiltrate as prognostic factor. M2 macrophages were identified as main part of the MDR1+ leucocyte infiltrate expressing MDR1 as well as the M2 marker CD163 and the pan-macrophage marker CD68. Infiltration of MDR1+ leucocytes, mostly M2 macrophages, is associated with poor prognosis of EOC patients. Further understanding of the interaction of M2 macrophages, MDR1 and TA-MUC1 appears to be a key aspect to overcome chemoresistance in ovarian cancer.

Pterostilbene Enhances Cytotoxicity and Chemosensitivity in Human Pancreatic Cancer Cells

Gemcitabine (GEM) drug resistance causes high mortality rates and poor outcomes in pancreatic ductal adenocarcinoma (PDAC) patients. Receptor for advanced glycation end products (RAGE) involvement in the GEM resistance process has been demonstrated. Therefore, finding a safe and effective way to inhibit receptors for RAGE-initiated GEM resistance is urgent. Pterostilbene (PTE), a natural methoxylated analogue derived from resveratrol and found in grapes and blueberries, has diverse bioactivities, such as antioxidative, anti-inflammatory, and anticancer qualities. The overall research objective was to determine the potential of PTE to enhance tumor cytotoxicity and chemosensitivity in PDAC cells. Our results have demonstrated that PTE induced S-phase cell cycle arrest, apoptosis, and autophagic cell death and inhibited multidrug resistance protein 1 (MDR1) expression by downregulating RAGE/PI3K/Akt signaling in both MIA PaCa-2 and MIA PaCa-2 GEMR cells (GEM-resistant cells). Remarkably, convincing evidence was established by RAGE small interfering RNA transfection. Taken together, our study demonstrated that PTE promoted chemosensitivity by inhibiting cell proliferation and MDR1 expression via the RAGE/PI3K/Akt axis in PDAC cells. The observations in these experiments indicate that PTE may play a crucial role in MDR1 modulation for PDAC treatment.