Laboratory of Genetic Toxicology, Federal University of Health Sciences of Porto Alegre (UFCSPA), Sarmento Leite st 245, Porto Alegre, RS, Brazil.
Cardiology Institute of Rio Grande do Sul/ University Foundation of Cardiology (ICFUC), Porto Alegre, RS, Brazil.
BMC Cancer. 2021 Apr 22;21(1):448. doi: 10.1186/s12885-021-08188-7.
The advances in colorectal cancer (CRC) treatment include the identification of deficiencies in Mismatch Repair (MMR) pathway to predict the benefit of adjuvant 5-fluorouracil (5-FU) and oxaliplatin for stage II CRC and immunotherapy. Defective MMR contributes to chemoresistance in CRC. A growing body of evidence supports the role of Poly-(ADP-ribose) polymerase (PARP) inhibitors, such as Olaparib, in the treatment of different subsets of cancer beyond the tumors with homologous recombination deficiencies. In this work we evaluated the effect of Olaparib on 5-FU cytotoxicity in MMR-deficient and proficient CRC cells and the mechanisms involved.
Human colon cancer cell lines, proficient (HT29) and deficient (HCT116) in MMR, were treated with 5-FU and Olaparib. Cytotoxicity was assessed by MTT and clonogenic assays, apoptosis induction and cell cycle progression by flow cytometry, DNA damage by comet assay. Adhesion and transwell migration assays were also performed.
Our results showed enhancement of the 5-FU citotoxicity by Olaparib in MMR-deficient HCT116 colon cancer cells. Moreover, the combined treatment with Olaparib and 5-FU induced G2/M arrest, apoptosis and polyploidy in these cells. In MMR proficient HT29 cells, the Olaparib alone reduced clonogenic survival, induced DNA damage accumulation and decreased the adhesion and migration capacities.
Our results suggest benefits of Olaparib inclusion in CRC treatment, as combination with 5-FU for MMR deficient CRC and as monotherapy for MMR proficient CRC. Thus, combined therapy with Olaparib could be a strategy to overcome 5-FU chemotherapeutic resistance in MMR-deficient CRC.
结直肠癌（CRC）治疗的进展包括确定错配修复（MMR）途径的缺陷，以预测辅助 5-氟尿嘧啶（5-FU）和奥沙利铂对 II 期 CRC 和免疫治疗的益处。MMR 缺陷导致 CRC 对化疗的耐药性。越来越多的证据支持聚（ADP-核糖）聚合酶（PARP）抑制剂，如奥拉帕利，在除同源重组缺陷肿瘤之外的不同癌症亚群中的治疗作用。在这项工作中，我们评估了奥拉帕利对 MMR 缺陷和功能正常的 CRC 细胞中 5-FU 细胞毒性的影响及其相关机制。
用人结肠癌细胞系 HT29（MMR 功能正常）和 HCT116（MMR 缺陷）进行 5-FU 和奥拉帕利治疗。通过 MTT 和集落形成实验评估细胞毒性，通过流式细胞术评估细胞凋亡诱导和细胞周期进程，通过彗星实验评估 DNA 损伤。还进行了细胞黏附和 Transwell 迁移实验。
我们的结果表明，奥拉帕利增强了 MMR 缺陷的 HCT116 结肠癌细胞中 5-FU 的细胞毒性。此外，奥拉帕利与 5-FU 联合治疗诱导这些细胞 G2/M 期阻滞、凋亡和多倍体形成。在 MMR 功能正常的 HT29 细胞中，奥拉帕利单独降低集落形成存活率，诱导 DNA 损伤积累，并降低黏附和迁移能力。
我们的结果表明，奥拉帕利的加入可能有益于 CRC 的治疗，特别是对 MMR 缺陷的 CRC 与 5-FU 联合治疗，以及对 MMR 功能正常的 CRC 作为单药治疗。因此，奥拉帕利联合治疗可能是克服 MMR 缺陷 CRC 中 5-FU 化疗耐药性的一种策略。
