Purpose
This study focused on combining irinotecan with Poly (ADP-ribose) polymerase (PARP) inhibitors to explore the potential for novel combination therapeutics in small cell lung cancer (SCLC).
Materials and Methods
We selected 10 different SCLC cell lines with diverse mutational backgrounds in DNA damage response (DDR) pathway genes to evaluate the efficacy of the combination of three PARP inhibitors and irinotecan. After the cells were exposed to the drugs for seven days, cell viability was measured, and a combination index was calculated. Apoptotic signaling was assessed via western blot, and DNA damage was evaluated using an alkaline comet assay.
Results
We assessed the synergistic effects of PARP inhibitors and irinotecan in in vitro SCLC models, which revealed increased sensitivity, particularly in cells harboring BRCA mutations. However, even in cells lacking mutations in DNA damage response pathway genes, the combination of the two drugs exhibited a synergistic effect. When treated with 50 nM irinotecan, the IC50 fold changes for PARP inhibitors were: olaparib, 1649 ± 4049; talazoparib, 25 ± 34.21; venadaparib, 336 ± 596.01. This combination enhanced apoptosis signaling and increased p-chk1 and p-p53 protein levels. Additionally, the treatment of PARP inhibitor with irinotecan increased DNA damage, as visualized by the alkaline comet assay.
Conclusion
This study provides preclinical evidence of the potential clinical benefits of combining irinotecan with PARP inhibitors in SCLC. Further clinical investigations are warranted to validate these findings for the development of more effective and personalized therapeutic strategies for SCLC patients.
Accurate detection of homologous recombination deficiency (HRD) in cancer patients is paramount in clinical applications, as HRD confers sensitivity to poly(ADP-ribose) polymerase (PARP) inhibitors. With the advances in genome sequencing technology, mutational profiling on a genome-wide scale has become readily accessible, and our knowledge of the genomic consequences of HRD has been greatly expanded and refined. Here, we review the recent advances in HRD detection methods. We examine the copy number and structural alterations that often accompany the genome instability that results from HRD, describe the advantages of mutational signature-based methods that do not rely on specific gene mutations, and review some of the existing algorithms used for HRD detection. We also discuss the choice of sequencing platforms (panel, exome, or whole-genome) and catalog the HRD detection assays used in key PARP inhibitor trials.
Purpose Up to 20% of patients with biliary tract cancer (BTC) have alterations in DNA damage response (DDR) genes, including homologous recombination (HR) genes. Therefore, the DDR pathway could be a promising target for new drug development in BTC. We aim to investigate the anti-tumor effects using poly(ADP-ribose) polymerase (PARP) and WEE1 inhibitors in BTC.
Materials and Methods We used 10 BTC cell lines to evaluate an anti-tumor effect of olaparib (a PARP inhibitor) and AZD1775 (a WEE1 inhibitor) in in vitro. Additionally, we established SNU869 xenograft model for in vivo experiments.
Results In this study, we observed a modest anti-proliferative effect of olaparib. DNA double-strand break (DSB) and apoptosis were increased by olaparib in BTC cells. However, olaparib-induced DNA DSB was repaired through the HR pathway, and G2 arrest was induced to secure the time for repair. As AZD1775 typically regulates the G2/M checkpoint, we combined olaparib with AZD1775 to abrogate G2 arrest. We observed that AZD1775 downregulated p-CDK1, a G2/M cell cycle checkpoint protein, and induced early mitotic entry. AZD1775 also decreased CtIP and RAD51 expression and disrupted HR repair. In xenograft model, olaparib plus AZD1775 treatment reduced tumor growth more potently than did monotherapy with either drug.
Conclusion This is the first study to suggest that olaparib combined with AZD1775 can induce synergistic anti-tumor effects against BTC. Combination therapy that blocks dual PARP and WEE1 has the potential to be further clinically developed for BTC patients.
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