Induction of TAp73 by platinum-based compounds to overcome drug resistance in p53 dysfunctional chronic lymphocytic leukemia

Selective synergistic anticancer effects of cisplatin and oridonin against human p53-mutant esophageal squamous carcinoma cells

Oridonin (ORI) is known to pose anticancer activity against cancer, which could induce the therapeutic impact of chemotherapy drugs. However, such simple combinations have numerous side effects such as higher toxicity to normal cells and tissues. To enhance the therapeutic effects with minimal side effects, here we used ORI in combination with cisplitin (CIS) against different esophageal squamous cell carcinoma (ESCC) cell lines in vitro, to investigate the synergistic anticancer effects of the two drugs against ESCC. Calcusyn Graphing Software was used to assess the synergistic effect. Apoptosis, wound healing and cell invasion assay were conducted to further confirm the synergistic effects of ORI and CIS. Intracellular glutathione (GSH) and reactive oxygen species assay, immunofluorescence staining and western blot were used to verify the mechanism of synergistic cytotoxicity. ORI and CIS pose selective synergistic effects on ESCC cells with p53 mutations. Moreover, we found that the synergistic effects of these drugs are mediated by GSH/ROS systems, such that intracellular GSH production was inhibited, whereas the ROS generation was induced following ORI and CIS application. In addition, we noted that DNA damage was induced as in response to ORI and CIS treatment. Overall, these results suggest that ORI can synergistically enhance the effect of CIS, and GSH deficiency and p53 mutation, might be biomarkers for the combinational usage of ORI and CIS.

The p53 Protein Family in the Response of Tumor Cells to Ionizing Radiation: Problem Development

Survival mechanisms are activated in tumor cells in response to therapeutic ionizing radiation. This reduces a treatment's effectiveness. The p53, p63, and p73 proteins belonging to the family of proteins that regulate the numerous pathways of intracellular signal transduction play a key role in the development of radioresistance. This review analyzes the p53-dependent and p53-independent mechanisms involved in overcoming the resistance of tumor cells to radiation exposure.

Suppression of minichromosome maintenance 7 expression sensitizes chronic lymphocytic leukemia cells to fludarabine

Chronic lymphocytic leukemia (CLL) constitutes the largest percentage of adult leukemia cases in Western countries. Classically, fludarabine (Flu) is an effective drug used as a first-line therapy for CLL; however, Flu resistance limits its clinical effect. Minichromosome maintenance (MCM) complex components 2-7 exert important functions in maintaining genomic stability. Replication stress occurs upon dysregulation of MCM7, which potentiates malignant phenotypes. In this study, primary CLL cells and CLL-derived cell lines displayed elevated MCM7 expression. In CD40-stimulated primary CLL cells, MCM7 inhibition resulted in increased Flu-induced apoptosis and delayed repair of DNA damage. In the MEC-1 and EHEB cell lines, knockdown of MCM7 with lentivirus significantly inhibited cell proliferation and promoted cell cycle arrest at S phase. Moreover, MCM7 silencing sensitized both cell lines to Flu by increasing replication stress. The combination of Flu administration with MCM7 inhibition represents a novel approach to reverse Flu resistance in CLL.