Loss of MLH1 sensitizes colon cancer cells to DNA-PKcs inhibitor KU60648
Loss of MLH1 sensitizes colon cancer cells to DNA-PKcs inhibitor KU60648
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DOI：
10.1002/mc.22640
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发表时间：
2017-07-01
影响因子：
4.6
通讯作者：
Brieger, Angela
中科院分区：
文献类型：
--
作者：
Hinrichsen, Inga;Ackermann, Anne;Brieger, Angela
MLH 1的生殖系突变导致近50%的Lynch综合征患者的肿瘤生成，约15%的散发性结直肠癌由于启动子超甲基化而表现出MLH 1缺陷。虽然这些肿瘤的侵袭性较低，但标准化疗对这些患者的益处仍在讨论中。最近，研究表明，对DNA-PKcs抑制剂KU60648的敏感性与MMR蛋白MSH 3的丢失有关。然而，MSH 3的丢失是继发性的，是MMR缺陷的结果，并且在MLH 1缺陷的肿瘤中经常可检测到。因此，我们检测了MLH 1、MSH 2、MSH 6和MSH 3在不同的MMR缺陷和熟练细胞系中的表达，并通过分析细胞活力和存活率来确定它们对KU60648的敏感性。照射后通过γ H2 AX检测监测MLH 1依赖的双链断裂（DSB）修复能力。包括一组12个结肠癌细胞系，两对细胞，其中MLH 1敲低与具有相同遗传背景的对照进行比较，以及一个MLH 1过表达的MLH 1缺陷细胞系。总之，我们发现MLH 1和/或MSH 3缺陷细胞对KU60648的敏感性显著高于MMR熟练细胞，并且MLH 1在MLH 1缺陷细胞中的过表达导致细胞敏感性降低。KU60648的效率似乎与DSB修复能力降低有关。由于结肠肿瘤MLH 1表达的分子检测是一种临床标准，我们认为MLH 1是一种更好的标志物，更多的患者将受益于KU60648治疗。
Germline mutations of MLH1 are responsible for tumor generation in nearly 50% of patients with Lynch Syndrome, and around 15% of sporadic colorectal cancers show MLH1-deficiency due to promotor hypermethylation. Although these tumors are of lower aggressiveness the benefit for these patients from standard chemotherapy is still under discussion. Recently, it was shown that the sensitivity to the DNA-PKcs inhibitor KU60648 is linked to loss of the MMR protein MSH3. However, loss of MSH3 is rather secondary, as a consequence of MMRdeficiency, and frequently detectable in MLH1-deficient tumors. Therefore, we examined the expression of MLH1, MSH2, MSH6, and MSH3 in different MMR-deficient and proficient cell lines and determined their sensitivity to KU60648 by analyzing cell viability and survival. MLH1-dependent ability of double strand break (DSB) repair was monitored after irradiation via gamma H2AX detection. A panel of 12 colon cancer cell lines, two pairs of cells, where MLH1 knock down was compared to controls with the same genetic background, and one MLH1-deficient cell line where MLH1 was overexpressed, were included. In summary, we found that MLH1 and/or MSH3-deficient cells exhibited a significantly higher sensitivity to KU60648 than MMR-proficient cells and that overexpression of MLH1 in MLH1-deficient cells resulted in a decrease of cell sensitivity. KU60648 efficiency seems to be associated with reduced DSB repair capacity. Since the molecular testing of colon tumors for MLH1 expression is a clinical standard we believe that MLH1 is a much better marker and a greater number of patients would benefit from KU60648 treatment.