Ataxia-telangiectasia mutated and ataxia telangiectasia and Rad3-related kinases as therapeutic targets and stratification indicators for prostate cancer

AZD1390, an Ataxia telangiectasia mutated inhibitor, enhances cisplatin mediated apoptosis in breast cancer cells

Genomic instability is often caused by deficiencies in DNA damage repair pathways, making therapeutic targeting of DDR beneficial for cancer patients with specific DDR functions. ATM kinase plays a critical role in various cellular processes and its deficiency increases sensitivity to DDR-targeted agents in different cancers. Recent studies highlight ATM inhibition as a potential clinical target, with AZD1390 being a notable ATM inhibitor due to its potent and selective inhibition, ability to accumulate at DNA breaks. The study aimed to evaluate the potential anti-cancer effects of AZD1390, a key component of the DNA damage response, in breast cancer cells. The impact of the combination of AZD1390 and cisplatin on various parameters such as cell viability, proliferation, colony formation capacity, DNA damage, reactive oxygen species (ROS) levels, mitochondrial membrane potential, cell cycle progression, and cell death in breast cancer cells was evaluated using several methodologies, including WST-1 assays, real-time cell analysis, colony formation assays, comet assays, DCF-DA, MMP/JC-1 staining assays, flow cytometry along with Western blot analysis. We found that AZD1390 and cisplatin displayed synergistic antitumor effects in breast cancer cells at low doses. Addinationaly exhibited significant anti-proliferative effects in colony formation and real-time cell proliferation experiments, increasing intracellular ROS levels and mitochondrial membrane potential.The combined treatment also arrested the cell cycle at the G2-M point. Furthermore, combination of AZD1390 with cisplatin enhances its apoptotic effects in MCF-7 and MDA-MB-231 cells. These findings could aid in developing new treatments for breast cancer that exploit the genomic instability of cancer cells.

Enzymatic approaches against SARS-CoV-2 infection with an emphasis on the telomere-associated enzymes

The pandemic phase of coronavirus disease 2019 (COVID-19) appears to be over in most countries. However, the unexpected behaviour and unstable nature of coronaviruses, including temporary hiatuses, re-emergence, emergence of new variants, and changing outbreak epicentres during the COVID-19 pandemic, have been frequently reported. The mentioned trend shows the fact that in addition to vaccine development, different strategies should be considered to deal effectively with this disease, in long term. In this regard, the role of enzymes in regulating immune responses to Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has recently attracted much attention. Moreover, several reports confirm the association of short telomeres with sever COVID-19 symptoms. This review highlights the role of several enzymes involved in telomere length (TL) regulation and explains their relevance to SARS-CoV-2 infection. Apparently, inhibition of telomere shortening (TS) through inhibition and/or activation of these enzymes could be a potential target in the treatment of COVID-19, which may also lead to a reduction in disease severity.

Targeting E2F Sensitizes Prostate Cancer Cells to Drug-Induced Replication Stress by Promoting Unscheduled CDK1 Activity

Simple Summary

E2F1 and E2F2 are highly expressed in many cancer types, but their contribution to malignancy is not well understood. Here we aimed to define the impact of E2F1/E2F2 deregulation in prostate cancer. We show that inhibition of E2F sensitizes prostate cancer cells to drug-induced replication stress and cell death. We found that E2F target genes involved in nucleotide biosynthesis contribute to maintaining genome stability in prostate cancer cells, but their enzymatic activity is insufficient to prevent replication stress after E2F1/E2F2 depletion. Instead, E2F1/E2F2 hinder premature CDK1 activation during S phase, which is key to ensure genome stability and viability of prostate cancer cells. From a therapeutic perspective, inhibiting E2F activity provokes catastrophic levels of replication stress and blunts xenograft growth in combination with drugs targeting nucleotide biosynthesis or DNA repair. Our results highlight the suitability of targeting E2F for the treatment of prostate cancer.

Abstract

E2F1/E2F2 expression correlates with malignancy in prostate cancer (PCa), but its functional significance remains unresolved. To define the mechanisms governed by E2F in PCa, we analyzed the contribution of E2F target genes to the control of genome integrity, and the impact of modulating E2F activity on PCa progression. We show that silencing or inhibiting E2F1/E2F2 induces DNA damage during S phase and potentiates 5-FU-induced replication stress and cellular toxicity. Inhibition of E2F downregulates the expression of E2F targets involved in nucleotide biosynthesis (TK1, DCK, TYMS), whose expression is upregulated by 5-FU. However, their enzymatic products failed to rescue DNA damage of E2F1/E2F2 knockdown cells, suggesting additional mechanisms for E2F function. Interestingly, targeting E2F1/E2F2 in PCa cells reduced WEE1 expression and resulted in premature CDK1 activation during S phase. Inhibition of CDK1/CDK2 prevented DNA damage induced by E2F loss, suggesting that E2F1/E2F2 safeguard genome integrity by restraining CDK1/CDK2 activity. Importantly, combined inhibition of E2F and ATR boosted replication stress and dramatically reduced tumorigenic capacity of PCa cells in xenografts. Collectively, inhibition of E2F in combination with drugs targeting nucleotide biosynthesis or DNA repair is a promising strategy to provoke catastrophic levels of replication stress that could be applied to PCa treatment.