背景:由于一种独特的可塑性形式:多倍体巨细胞(PGCC)的可塑性,在癌症中可能会出现基因组不稳定性和化学抗性。这些细胞在化疗的应激下形成并具有高于二倍体的染色体含量。PGCC然后能够通过不对称的子细胞出芽过程重新填充肿瘤。PGCC已在卵巢癌组织学中观察到,包括致命的和常见的高级别浆液性卵巢癌(HGSC)。我们先前发现,破坏自噬细胞再循环过程的药物在临床前HGSC模型中是独特有效的。虽然自噬诱导与PGCC相关,以前从未研究过自噬调节是否与PGCC生命周期和这种形式的肿瘤细胞可塑性相互作用。
方法:CAOV3和OVCAR3卵巢癌细胞系用卡铂或多西他赛处理以诱导PGCC形成。显微镜用于表征和定量由化疗形成的PGCC。两种临床上可用的抑制自噬的药物,羟氯喹和奈非那韦,和临床上可用的自噬激活剂,雷帕霉素,用于测试这些自噬调节剂对PGCC诱导和随后从PGCC形成集落的影响。使用结晶紫染色的集落形成测定来定量PGCC生命周期的肿瘤再繁殖阶段。
结果:自噬抑制剂不能阻止OVCAR3或CAOV3细胞中PGCC的形成。雷帕霉素自身不诱导PGCC形成,也不通过化疗加剧PGCC形成。然而,羟氯喹可防止卡铂(27%抑制)或多西他赛(41%抑制)诱导的CAOV3PGCC中的有效集落形成,以及OVCAR3细胞(95%和77%,分别)。奈非那韦类似地防止卡铂(64%抑制)或多西他赛(94%抑制)诱导的CAOV3PGCC以及OVCAR3细胞(89%和80%,分别)。雷帕霉素还令人惊讶地防止PGCC集落生长(52-84%抑制)。
结论:虽然先前观察到的与PGCC形成相关的自噬不太可能是PGCC形成所必需的,自噬调节药物严重损害HGSCPGCCs形成集落的能力。使用羟氯喹的临床试验,奈非那韦,和/或雷帕霉素化疗后可能是未来的兴趣。
BACKGROUND: Genomic instability and chemoresistance can arise in cancer due to a unique form of plasticity: that of polyploid giant cancer cells (PGCCs). These cells form under the stress of chemotherapy and have higher than diploid chromosome content. PGCCs are able to then repopulate tumors through an asymmetric daughter cell budding process. PGCCs have been observed in ovarian cancer histology, including the deadly and common form high-grade serous ovarian carcinoma (HGSC). We previously discovered that drugs which disrupt the cellular recycling process of autophagy are uniquely efficacious in pre-clinical HGSC models. While autophagy induction has been associated with PGCCs, it has never been previously investigated if autophagy modulation interacts with the PGCC life cycle and this form of tumor cell plasticity.
METHODS: CAOV3 and OVCAR3 ovarian cancer cell lines were treated with carboplatin or docetaxel to induce PGCC formation. Microscopy was used to characterize and quantify PGCCs formed by chemotherapy. Two clinically available drugs that inhibit autophagy, hydroxychloroquine and nelfinavir, and a clinically available activator of autophagy, rapamycin, were employed to test the effect of these autophagy modulators on PGCC induction and subsequent colony formation from PGCCs. Crystal violet-stained colony formation assays were used to quantify the tumor-repopulating stage of the PGCC life cycle.
RESULTS: Autophagy inhibitors did not prevent PGCC formation in OVCAR3 or CAOV3 cells. Rapamycin did not induce PGCC formation on its own nor did it exacerbate PGCC formation by chemotherapy. However, hydroxychloroquine prevented efficient colony formation in CAOV3 PGCCs induced by carboplatin (27% inhibition) or docetaxel (41% inhibition), as well as in OVCAR3 cells (95% and 77%, respectively). Nelfinavir similarly prevented colony formation in CAOV3 PGCCs induced by carboplatin (64% inhibition) or docetaxel (94% inhibition) as well as in OVCAR3 cells (89% and 80%, respectively). Rapamycin surprisingly also prevented PGCC colony outgrowth (52-84% inhibition).
CONCLUSIONS: While the autophagy previously observed to correlate with PGCC formation is unlikely necessary for PGCCs to form, autophagy modulating drugs severely impair the ability of HGSC PGCCs to form colonies. Clinical trials which utilize hydroxychloroquine, nelfinavir, and/or rapamycin after chemotherapy may be of future interest.