Department of Oncogene Regulation, Chittaranjan National Cancer Institute, 37, S.P. Mukherjee Road, Kolkata 700026, West Bengal, India.
Department of Pathology, Nil Ratan Sircar Medical College and Hospital, Kolkata 700014, India.
Gene. 2023 Dec 20;888:147746. doi: 10.1016/j.gene.2023.147746. Epub 2023 Aug 30.
Cervical cancer (CACX) is one of the top causes of cancer death in women globally. The involvement of several cellular pathways in carcinogenesis is still poorly understood. Here, we focused to evaluate the contributory role of Mismatch Repair (MMR) pathway genes-MLH1 and MSH2 in CACX and their association with chemo-tolerance of the disease. For this purpose, molecular profiles (expression/promoter methylation/deletion) of the genes were analysed in both normal cervical epithelium and tumour tissue, also validated in in-silico dataset as well. Later on, prognostic importance of the genes was identified through analysis of their methylation/expression status in plasma DNA of circulating tumour cells (CTCs) and cisplatin-tolerant CACX cell lines respectively. It was found that the expression profile of MLH1 and MSH2 genes was considerably reduced from undifferentiated basal-parabasal layers of normal cervical epithelium towards progression of the disease. Further analysis showed that frequent deletion [34-48%] and promoter methylation events [28-46%] of the genes were the plausible reasons for their reduced expression during tumorigenesis. Incidentally, the prevalence of MLH1 [32%] and MSH2 [27%] promoter methylation found in CTCs of plasma of the clinically advanced CACX patients implicated their prognostic importance of the disease. In addition, the patients having high alterations of those genes resulted in poor patient outcomes even after the therapy. In in-depth analysis of this result in cisplatin-tolerant CACX cell lines, we discovered that increased promoter methylation frequency of those genes at higher concentrations of cisplatin and gradual accumulation of the cells in the G2/M phase of the cell cycle were the rational causes for their reduced expression and MMR deficiency in the system. Hence, it is possible to conclude that the gradual down-regulation of MLH1 and MSH2 proteins may be a key event for MMR pathway inactivation in CACX. This might also be associated with chemo-tolerance and overall poor survival among the patients.
宫颈癌 (CACX) 是全球女性癌症死亡的主要原因之一。细胞癌变过程中涉及的多个细胞途径仍知之甚少。在这里，我们专注于评估错配修复 (MMR) 途径基因-MLH1 和 MSH2 在 CACX 中的作用及其与疾病化疗耐受性的关系。为此，我们分析了这些基因在正常宫颈上皮和肿瘤组织中的分子特征（表达/启动子甲基化/缺失），并在计算机数据集上进行了验证。后来，通过分析循环肿瘤细胞 (CTC) 中血浆 DNA 的基因甲基化/表达状态以及耐顺铂的 CACX 细胞系中的基因表达状态，确定了这些基因的预后意义。结果发现，MLH1 和 MSH2 基因的表达谱从未分化的基底-副基底层向疾病进展方向显著降低。进一步分析表明，基因的频繁缺失[34-48%]和启动子甲基化事件[28-46%]是其在肿瘤发生过程中表达降低的可能原因。偶然的是，在临床晚期 CACX 患者血浆 CTC 中发现 MLH1[32%]和 MSH2[27%]启动子甲基化的发生率表明其对疾病具有预后意义。此外，即使在治疗后，这些基因发生高改变的患者预后较差。在对耐顺铂的 CACX 细胞系中进行深入分析时，我们发现这些基因在顺铂浓度较高时启动子甲基化频率增加，以及细胞逐渐积累到细胞周期的 G2/M 期，是导致其表达降低和 MMR 缺陷的合理原因。因此，可以得出结论，MLH1 和 MSH2 蛋白的逐渐下调可能是 CACX 中 MMR 途径失活的关键事件。这也可能与患者的化疗耐受性和整体生存率低有关。
