Downregulation of RBBP6 variant 1 during arsenic trioxide-mediated cell cycle arrest and curcumin-induced apoptosis in MCF-7 breast cancer cells

Probing the Effects of Retinoblastoma Binding Protein 6 (RBBP6) Knockdown on the Sensitivity of Cisplatin in Cervical Cancer Cells

Cervical cancer is a major cause of death in women despite the advancement of current treatment modalities. The conventional therapeutic agent, cisplatin (CCDP), is the standard treatment for CC; however, resistance often develops due to the cancer's heterogeneity. Therefore, a detailed elucidation of the specific molecular mechanisms driving CC is crucial for the development of targeted therapeutic strategies. Retinoblastoma binding protein 6 (RBBP6) is a potential biomarker associated with cell proliferation and is upregulated in cervical cancer sites, exhibiting apoptosis and dysregulated p53 expression. Furthermore, RBBP6 has been demonstrated to sensitize cancer cells to radiation and certain chemotherapeutic agents by regulating the Bcl-2 gene, thus suggesting a crosstalk among RBBP6/p53/BCL-2 oncogenic signatures. The present study, therefore, investigated the relationship between cisplatin and RBBP6 expression in CC cells. Herein, we first explored bioinformatics simulations and identified that the RBBP6/p53/BCL-2 signaling pathway is overexpressed and correlated with CC. For further analysis, we explored the Genomics of Drug Sensitivity in Cancer (GDSC) and found that most of the CC cell lines are sensitive to CCDP. To validate these findings, RBBP6 was silenced in HeLa and Vero cells using RNAi technology, followed by measurement of wild-type p53 and Bcl-2 at the mRNA level using qPCR. Cells co-treated with cisplatin and siRBBP6 were subsequently analyzed for apoptosis induction and real-time growth monitoring using flow cytometry and the xCELLigence system, respectively. Cancer cells in the co-treatment group showed a reduction in apoptosis compared to the cisplatin-treated group. Moreover, the real-time growth monitoring revealed a reduced growth rate in RBBP6 knockdown cells treated with cisplatin. Although wild-type p53 remained unchanged in the co-treatment group of cancer cells, Bcl-2 was completely repressed, suggesting that RBBP6 is necessary for sensitizing cervical cancer cells to cisplatin treatment by downregulating Bcl-2. The Vero cell population, which served as a non-cancerous control cell line in this study, remained viable following treatment with both siRBBP6 and cisplatin. Findings from this study suggest that RBBP6 expression promotes cisplatin sensitivity in HeLa cells through Bcl-2 downregulation. Knockdown of RBBP6 limits apoptosis induction and delays cell growth inhibition in response to cisplatin. The knowledge obtained here has the potential to help improve cisplatin efficacy through personalized administration based on the expression profile of RBBP6 among individual patients.

Long noncoding RNAs (lncRNAs) in HIV-mediated carcinogenesis: Role in cell homeostasis, cell survival processes and drug resistance

There is accruing data implicating long non-coding RNAs (lncRNAs) in the development and progression of non-communicable diseases such as cancer. These lncRNAs have been implicated in many diverse HIV-host interactions, some of which are beneficial to HIV propagation. The virus-host interactions induce the expression of HIV-regulated long non-coding RNAs, which are implicated in the carcinogenesis process, therefore, it is critical to understand the molecular mechanisms that underpin these HIV-regulated lncRNAs, especially in cancer formation. Herein, we summarize the role of HIV-regulated lncRNAs targeting cancer development-related processes including apoptosis, cell cycle, cell survival signalling, angiogenesis and drug resistance. It is unclear how lncRNAs regulate cancer development, this review also discuss recent discoveries regarding the functions of lncRNAs in cancer biology. Innovative research in this field will be beneficial for the future development of therapeutic strategies targeting long non-coding RNAs that are regulated by HIV, especially in HIV associated cancers.

P53-Related Anticancer Activities of Drimia calcarata Bulb Extracts Against Lung Cancer

Current lung cancer treatment strategies are ineffective, and lung cancer cases continue to soar; thus, novel anticancer drugs and targets are needed, and medicinal plants are promising to offer better alternatives. This study was aimed at analysing two p53 splice variants during the potential anticancer activities of Drimia calcarata (Dc) methanol and water extracts against different human lung cancer cell lines of varying p53 mutation status, and these included mutant H1573 and mutant H1437 and p53-wild type (A549) cells. The anticancer activities of the Dc extracts were assessed by establishing the cytotoxic effect and the apoptosis-inducing capacity of these extracts, using the MTT assay and Annexin V analysis, respectively, with the latter confirmed using fluorescence microscopy. The molecular mechanisms induced by these extracts were further evaluated using cell cycle analysis and RT-PCR. Both extracts demonstrated safety against noncancerous lung MRC-5 fibroblasts and exhibited significant anticancer potency (p < 0.001) against the H1437 (IC₅₀ values: 62.50 μg/ml methanol extract and 125 μg/ml WE), H1573 (IC₅₀ value: 125 μg/ml for both extracts) and A549 (IC₅₀ value: 500 μg/ml ME). The water extract had no effect on the viability of A549 cells. Treated H1437 cells underwent p53-dependent apoptosis and S-phase cell cycle arrest while H1573 treated cells underwent p53-independed apoptosis and G0/G1 cell cycle arrest through upregulation of p21 mRNA expression levels. The expression levels of STAT1, STAT3, STAT5A and STAT5B genes increased significantly (p < 0.001) following the treatment of H1573 cells with ME and WE. Treatment of H1437 cells with ME upregulated the STAT1, STAT3, STAT5A and STAT5B mRNAs. Our results indicate that the proliferative inhibitory effect of D. calcarata extracts on A549 and H1573 cells is correlated with the suppression of Bcl-2, STAT3 and STAT5B while that is not the case in H1437 cells. Thus, our results suggest that the dysregulation of anti-apoptotic molecules Bcl-2, STAT3, STAT5A and STAT5B in H1437 may play a role in cancer cell survival, which may consequently contribute to the development of p53-mutated non-small human lung cancer. Our results indicate that D. calcarata is a promising source of anticancer agents for the treatment of p53-mutant human non-small lung cancer cells than the p53-wild type human non-small lung cancer cells.