Search

In mammalian cells, DNA damage response initiates repair by error-free homologous recombination (HRR) or by error-prone non-homologous end joining (NHEJ). DNA damage is detected by PARP proteins that facilitate this repair, both in normal cells and in cancer cells. Cells containing BRCA1/2 mutations have an HRR-deficient repair mechanism which may result in unrepaired one-ended double-strand breaks and stalled replication forks, considered as the most lethal cell damage. Here, we review the state of the art of the role of Poly (ADP-ribose) polymerase (PARP) inhibitors as a precision-targeted anticancer drug in BRCA1/2-mutated female breast cancer. Although knowledge is incomplete, it is assumed that the main role of the archetype PARP1 in the cell nucleus is to detect and adhere to single-strand breaks. This mediates possible damage repair, after which cells may continue replication; this process is called synthetic lethality. As for PARP clinical monotherapy, progression-free survival has been observed using the FDA- and EMA-approved drugs olaparib and talazoparib. In the case of combined drug therapy, a synergy has been demonstrated between veliparib and platinum drugs. Information regarding adverse effects is limited, but hematological effects have been described. However, there is need for multicenter trials, preferably conducted without commercial guidance and funding. Some of the available trials reported resistance to PARP inhibitors. In this review, we also describe the various causes of resistance to PARP inhibitors and research indicating how resistance can be overcome. [ABSTRACT FROM AUTHOR]

Objective: G protein-coupled receptor 43 (GPR43), a receptor for short-chain fatty acids, plays a role in suppressing tumor growth; however, the detailed underlying mechanism needs to be comprehensively elucidated. In this study, we investigated the role of GPR43 in inhibiting tumor growth using ApcMin/+, a murine model of intestinal tumors.Materials and Methods: Using GPR43-/- ApcMin/+ and GPR43+/- ApcMin/+ mice, the number of tumors was analyzed at the end of the experimental period. Immunohistochemistry, quantitative polymerase chain reaction, and Western blotting were performed to analyze cellular proliferation and proliferation-associated signal pathways.Results: Our results revealed that GPR43 deficiency resulted in increased tumor numbers in ApcMin/+ mice. Ki67 was highly expressed in GPR43-/- mice (p > 0.05). Increased expression levels of proinflammatory cytokines, including interleukin-6 and tumor necrosis factor-α, and amino acid transporters were not observed in GPR43-deficient mice compared to GPR43-sufficient mice. Furthermore, GPR43-deficient tumor tissues showed enhanced mammalian target of rapamycin-mediated phosphorylated ribosomal protein S6 kinase beta-1 (p > 0.05) and phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (p > 0.05), but not Akt (protein kinase B) phosphorylation (p = 0.7088).Conclusion: Collectively, GPR43 affords protection against tumor growth at least partly through inhibition of the mammalian target of rapamycin complex 1 pathway. [ABSTRACT FROM AUTHOR]