Radka Michalková

Overexpression of biliverdin reductase A leads to ROS-independent sensitization of ovarian adenocarcinoma cells to gemcitabine

Biliverdin reductase A (BLVRA) is a key enzyme in bilirubin metabolism, where it reduces biliverdin to bilirubin. Bilirubin is a potent antioxidant that protects cells from oxidative stress. Therefore, reduced or deregulated BLVRA activity may contribute to increased oxidative DNA damage, which is one of the factors leading to the neoplastic transformation of cells. Human ovarian adenocarcinoma A2780 cells were transfected with a PiggyBac vector to achieve BLVRA overexpression. A2780 clones showing the most significant BLVRA gene overexpression were analyzed by proteomics and flow cytometry to assess rective oxygen species (ROS) production. Our results indicate that BLVRA overexpression increases the sensitivity of A2780 cells to doxorubicin and gemcitabine, with the most pronounced effect observed in the J clone. In this clone, the highest level of BLVRA overexpression correlated with significant alterations in the p53 signaling pathway. Upregulation of key effectors such as Bax and CDKN2A indicates a potential role for BLVRA in promoting pro-apoptotic responses. Moreover, BLVRA overexpression increased the sensitivity of A2780 cells to gemcitabine independently of ROS. This study broadens our understanding of BLVRA in ovarian cancer. In cells with intact p53 signaling, BLVRA overexpression can paradoxically enhance cytotoxic response to certain drugs, particularly gemcitabine.

The Induction of G2/M Phase Cell Cycle Arrest and Apoptosis by the Chalcone Derivative 1C in Sensitive and Resistant Ovarian Cancer Cells Is Associated with ROS Generation

Ovarian cancer ranks among the most severe forms of cancer affecting the female reproductive organs, posing a significant clinical challenge primarily due to the development of resistance to conventional therapies. This study investigated the effects of the chalcone derivative 1C on sensitive (A2780) and cisplatin-resistant (A2780cis) ovarian cancer cell lines. Our findings revealed that 1C suppressed cell viability, induced cell cycle arrest at the G2/M phase, and triggered apoptosis in both cell lines. These effects are closely associated with generating reactive oxygen species (ROS). Mechanistically, 1C induced DNA damage, modulated the activity of p21, PCNA, and phosphorylation of Rb and Bad proteins, as well as cleaved PARP. Moreover, it modulated Akt, Erk1/2, and NF-κB signaling pathways. Interestingly, we observed differential effects of 1C on Nrf2 levels between sensitive and resistant cells. While 1C increased Nrf2 levels in sensitive cells after 12 h and decreased them after 48 h, the opposite effect was observed in resistant cells. Notably, most of these effects were suppressed by the potent antioxidant N-acetylcysteine (NAC), underscoring the crucial role of ROS in 1C-induced antiproliferative activity. Moreover, we suggest that modulation of Nrf2 levels can, at least partially, contribute to the antiproliferative effect of chalcone 1C.

Exploring the Antiproliferative and Modulatory Effects of 1-Methoxyisobrassinin on Ovarian Cancer Cells: Insights into Cell Cycle Regulation, Apoptosis, Autophagy, and Its Interactions with NAC

Ovarian cancer, a highly lethal malignancy among reproductive organ cancers, poses a significant challenge with its high mortality rate, particularly in advanced-stage cases resistant to platinum-based chemotherapy. This study explores the potential therapeutic efficacy of 1-methoxyisobrassinin (MB-591), a derivative of indole phytoalexins found in Cruciferae family plants, on both cisplatin-sensitive (A2780) and cisplatin-resistant ovarian cancer cells (A2780 cis). The findings reveal that MB-591 exhibits an antiproliferative effect on both cell lines, with significantly increased potency against cisplatin-sensitive cells. The substance induces alterations in the distribution of the cell cycle, particularly in the S and G2/M phases, accompanied by changes in key regulatory proteins. Moreover, MB-591 triggers apoptosis in both cell lines, involving caspase-9 cleavage, PARP cleavage induction, and DNA damage, accompanied by the generation of reactive oxygen species (ROS) and mitochondrial dysfunction. Notably, the substance selectively induces autophagy in cisplatin-resistant cells, suggesting potential targeted therapeutic applications. The study further explores the interplay between MB-591 and antioxidant N-acetylcysteine (NAC), in modulating cellular processes. NAC demonstrates a protective effect against MB-591-induced cytotoxicity, affecting cell cycle distribution and apoptosis-related proteins. Additionally, NAC exhibits inhibitory effects on autophagy initiation in cisplatin-resistant cells, suggesting its potential role in overcoming resistance mechanisms.