Knockdown of Wip1 Enhances Sensitivity to Radiation in HeLa Cells Through Activation of p38 MAPK

DNA damage response revisited: the p53 family and its regulators provide endless cancer therapy opportunities

Antitumor therapeutic strategies that fundamentally rely on the induction of DNA damage to eradicate and inhibit the growth of cancer cells are integral approaches to cancer therapy. Although DNA-damaging therapies advance the battle with cancer, resistance, and recurrence following treatment are common. Thus, searching for vulnerabilities that facilitate the action of DNA-damaging agents by sensitizing cancer cells is an active research area. Therefore, it is crucial to decipher the detailed molecular events involved in DNA damage responses (DDRs) to DNA-damaging agents in cancer. The tumor suppressor p53 is active at the hub of the DDR. Researchers have identified an increasing number of genes regulated by p53 transcriptional functions that have been shown to be critical direct or indirect mediators of cell fate, cell cycle regulation, and DNA repair. Posttranslational modifications (PTMs) primarily orchestrate and direct the activity of p53 in response to DNA damage. Many molecules mediating PTMs on p53 have been identified. The anticancer potential realized by targeting these molecules has been shown through experiments and clinical trials to sensitize cancer cells to DNA-damaging agents. This review briefly acknowledges the complexity of DDR pathways/networks. We specifically focus on p53 regulators, protein kinases, and E3/E4 ubiquitin ligases and their anticancer potential.

Dynamical modeling of miR-34a, miR-449a, and miR-16 reveals numerous DDR signaling pathways regulating senescence, autophagy, and apoptosis in HeLa cells

Transfection of tumor suppressor miRNAs such as miR-34a, miR-449a, and miR-16 with DNA damage can regulate apoptosis and senescence in cancer cells. miR-16 has been shown to influence autophagy in cervical cancer. However, the function of miR-34a and miR-449a in autophagy remains unknown. The functional and persistent G1/S checkpoint signaling pathways in HeLa cells via these three miRNAs, either synergistically or separately, remain a mystery. As a result, we present a synthetic Boolean network of the functional G1/S checkpoint regulation, illustrating the regulatory effects of these three miRNAs. To our knowledge, this is the first synthetic Boolean network that demonstrates the advanced role of these miRNAs in cervical cancer signaling pathways reliant on or independent of p53, such as MAPK or AMPK. We compared our estimated probability to the experimental data and found reasonable agreement. Our findings indicate that miR-34a or miR-16 may control senescence, autophagy, apoptosis, and the functional G1/S checkpoint. Additionally, miR-449a can regulate just senescence and apoptosis on an individual basis. MiR-449a can coordinate autophagy in HeLa cells in a synergistic manner with miR-16 and/or miR-34a.

Anticancer drug and ionizing radiation-induced DNA damage differently influences transcription activity and DDR-related stress responses of an endothelial monolayer

The endothelium contributes to the pathophysiology of adverse effects caused by conventional (genotoxic) anticancer therapeutics (cAT). The relevance of structurally different types of cAT-induced DNA lesions for eliciting selected endothelial stress responses is largely unknown. Here, we analyzed the cAT-induced formation of DNA double-strand breaks (DSB), transcription blockage and DNA damage response (DDR) in time kinetic analyses employing a monolayer of primary human endothelial cells (HUVEC). We observed that the degree of cAT-induced transcription blockage, the number of DSB and activation of DDR-related factors diverge. For instance, ionizing radiation caused the formation of numerous DSB and triggerd a substantial activation of ATM/Chk2 signaling, which however were not accompanied by a significant transcription inhibition. By contrast, the DNA cross-linking cAT cisplatin triggered a rapid and substantial blockage of transcription, which yet was not reflected by an appreciable number of DSB or increased levels of pATM/pChk2. In general, cAT-stimulated ATM-dependent phosphorylation of Kap1 (Ser824) and p53 (Ser15) reflected best cAT-induced transcription blockage. In conclusion, cAT-induced formation of DSB and profound activation of prototypical DDR factors is independent of the inhibition of RNA polymerase II-regulated transcription in an endothelial monolayer. We suggest that DSB formed directly or indirectly following cAT-treatment do not act as comprehensive triggers of superior signaling pathways shutting-down transcription while, at the same time, causing an appreciable stimulation of the DDR. Rather, it appears that distinct cAT-induced DNA lesions elicit diverging signaling pathways, which separately control transcription vs. DDR activity in the endothelium.

Wip1 regulates SKOV3 cell apoptosis through the p38 MAPK signaling pathway

The aim of the present study was to explore the effect of silencing wild-type p53-induced phosphatase 1 (Wip1) on apoptosis of human ovarian cancer SKOV3 cells. SKOV3 cells cultured in vitro were divided into three groups: untreated cells, cells transfected with control small interfering RNA (siRNA) and cells transfected with siRNA targeting Wip1. Flow cytometry analysis was used to detect cell apoptosis. Western blot analysis was performed to determine expression of tumor protein 53 (p53), cleaved caspase-3, caspase-3, BCL2 associated X (Bax), BCL2 apoptosis regulator (Bcl-2), p38 mitogen-activated protein kinase (p38 MAPK) and phosphorylated (p)-p38 MAPK. Reverse transcription-quantitative polymerase chain reaction was used to detect expression of p53, Bax, Bcl-2 and caspase-3 mRNAs. Compared with control, apoptosis of SKOV3 cell was significantly increased following Wip1 siRNA silencing. Wip1 silencing also resulted in a significant increase of p53 and p-p38 MAPK expression, as well as increased cleaved caspase-3/caspase-3 and Bax/Bcl-2 protein ratios. No significant differences were observed in apoptosis and apoptosis-related protein expression in the control siRNA transfected cells. The present study demonstrated that Wip1 silencing promotes apoptosis of human ovarian cancer SKOV3 cells by activation of the p38 MAPK signaling pathways and through subsequent upregulation of p53, and cleaved caspase-3/caspase-3 and Bax/Bcl-2 protein ratios. Overall, the findings of the present study suggest that targeting Wip1 may be a potential therapeutic avenue for the treatment of human ovarian cancer in the future.

Wild-type p53-induced phosphatase 1 is a prognostic marker and therapeutic target in bladder transitional cell carcinoma

Wild-type p53-induced phosphatase (Wip1) is an established oncogene and is associated with development of multiple forms of human cancer. However, the expression and role of Wip1 in human bladder transitional cell carcinoma (TCC) remains to be elucidated. In the present study, immunohistochemistry demonstrated that Wip1 was overexpressed in bladder TCC tissues compared with corresponding normal bladder tissues in 106 bladder TCC cases (P<0.0001). Furthermore, high expression levels of Wip1 were significantly associated with increasing tumor size (P=0.002), pathological grade (P=0.025), clinical T stage (P=0.001) and lymph nodal metastasis (P=0.003). Kaplan-Meier survival analysis identified that patients with high Wip1 expression levels exhibited a lower overall survival time (P<0.0001), and Cox proportional hazards regression model analysis demonstrated that Wip1 expression was an independent prognostic factor in patients with bladder TCC (P=0.025). In addition, downregulation of Wip1 expression by transfection with small interfering RNA in bladder cancer cells inhibited cell proliferation, invasion and migration (P<0.05), along with the upregulation of p53 protein levels (P<0.05). These findings suggest that Wip1 may function as a potential prognostic marker and therapeutic target in bladder cancer.