The antiproliferative effects of ataxia-telangiectasia mutated and ATM- and Rad3-related inhibitions and their enhancements with the cytotoxicity of DNA damaging agents in cholangiocarcinoma cells

DNA damage response mutations enhance the antitumor efficacy of ATR and PARP inhibitors in cholangiocarcinoma cell lines

Cholangiocarcinoma (CCA) is a biliary tract carcinoma that is challenging to treat due to its heterogeneity and limited treatment options. Genetic alterations in DNA damage response (DDR) pathways and homologous recombination (HR) defects are common in CCA. This has prompted interest in the use of ataxia telangiectasia and Rad3-related protein (ATR) and poly(ADP-ribose) polymerase (PARP) inhibitors to treat CCA. The present study investigated the impact of an ATR inhibitor and various PARP inhibitors, individually and in combination, on CCA cell lines with different DDR mutation profiles. DDR gene alterations in these cell lines were analyzed, and the responses of the cells to treatment with the PARP inhibitors olaparib, veliparib and talazoparib and/or the ATR inhibitor AZD6738 were evaluated. Assessments focused on cellular viability, clonogenic survival and the combination index, alongside changes in DNA damage assessed via the formation of micronuclei and γ-H2A histone family member X foci. The results revealed that the CCA cell lines with more DDR mutations exhibited greater sensitivity to single and combination treatments. Talazoparib was found to be the most potent PARP inhibitor in the CCA cell lines. The combination of AZD6738 and talazoparib demonstrated varying synergistic effects depending on the genetic background of the CCA cells, with greater efficacy in the cell lines less sensitive to single drug treatments. Mechanistically, this combination promoted the accumulation of DNA damage, including DNA double-strand breaks. Overall, the study underscores the importance of HR in CCA. It reveals an association between the extent of DDR mutations and the response to AZD6738 and PARP inhibitors in CCA, both as single agents and in combination. These findings highlight that the number of mutated genes influences variability in the drug response.

A Triphenylphosphonium-Functionalized Delivery System for an ATM Kinase Inhibitor That Ameliorates Doxorubicin Resistance in Breast Carcinoma Mammospheres

The enzyme ataxia-telangiectasia mutated (ATM) kinase is a pluripotent signaling mediator which activates cellular responses to genotoxic and metabolic stress. It has been shown that ATM enables the growth of mammalian adenocarcinoma stem cells, and therefore the potential benefits in cancer chemotherapy of a number of ATM inhibitors, such as KU-55933 (KU), are currently being investigated. We assayed the effects of utilizing a triphenylphosphonium-functionalized nanocarrier delivery system for KU on breast cancer cells grown either as a monolayer or in three-dimensional mammospheres. We observed that the encapsulated KU was effective against chemotherapy-resistant mammospheres of breast cancer cells, while having comparably lower cytotoxicity against adherent cells grown as monolayers. We also noted that the encapsulated KU sensitized the mammospheres to the anthracycline drug doxorubicin significantly, while having only a weak effect on adherent breast cancer cells. Our results suggest that triphenylphosphonium-functionalized drug delivery systems that contain encapsulated KU, or compounds with a similar impact, are a useful addition to chemotherapeutic treatment schemes that target proliferating cancers.

Glutathione-sensitive nanoparticles enhance the combined therapeutic effect of checkpoint kinase 1 inhibitor and cisplatin in prostate cancer

Prostate cancer (PCa) is the second most common malignant tumor among males. Traditional treatments for PCa, which include surgery and endocrine therapy, have shown limited success, and more effective therapies are needed. Cisplatin (DDP) is an approved chemotherapeutic drug that causes DNA damage in cancer, whereas AZD7762, an inhibitor of CHK1, can significantly inhibit DNA repair. The effective therapeutic combination of cisplatin and the DNA damage response inhibitor AZD7762 has been considered to be a potential solution to the resistance to cisplatin and the adverse reactions that occur in many cancers. However, the co-transmission of cisplatin and AZD7762 and the unsatisfactory tumor-targeting efficacy of this therapy remain problems to be solved. Here, we confirmed the combined therapeutic efficacy of cisplatin and AZD7762 in PCa. Furthermore, we show that the glutathione-targeted Cys8E nanoparticles we synthesized, which have high drug-loading capacity, remarkable stability, and satisfactory release efficiency, enhanced the therapeutic efficacy of this treatment and reduced the required dosages of these drugs both in vitro and in vivo. Overall, we propose combination therapy of cisplatin and AZD7762 for PCa and facilitate it using Cys8E nanoparticles, which allow for better drug loading release, higher release efficiency, and more accurate tumor-targeting efficacy.

DNA Damage Response Inhibitors in Cholangiocarcinoma: Current Progress and Perspectives

Cholangiocarcinoma (CCA) is a poorly treatable type of cancer and its incidence is dramatically increasing. The lack of understanding of the biology of this tumor has slowed down the identification of novel targets and the development of effective treatments. Based on next generation sequencing profiling, alterations in DNA damage response (DDR)-related genes are paving the way for DDR-targeting strategies in CCA. Based on the notion of synthetic lethality, several DDR-inhibitors (DDRi) have been developed with the aim of accumulating enough DNA damage to induce cell death in tumor cells. Observing that DDRi alone could be insufficient for clinical use in CCA patients, the combination of DNA-damaging regimens with targeted approaches has started to be considered, as evidenced by many emerging clinical trials. Hence, novel therapeutic strategies combining DDRi with patient-specific targeted drugs could be the next level for treating cholangiocarcinoma.