Solaimuthu Balakrishnan, Lichtenstein Michal, Hayashi Arata, Khatib Anees, Plaschkes Inbar, Nevo Yuval, Tanna Mayur, Pines Ophry, Shaul Yoav D
Department of Biochemistry and Molecular Biology, The Institute for Medical Research Israel-Canada, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem 9112001, Israel.
Info-CORE, Bioinformatics Unit of the I-CORE Computation Center, Hebrew University of Jerusalem, Jerusalem 9112001, Israel.
Cancers (Basel). 2022 Nov 9;14(22):5508. doi: 10.3390/cancers14225508.
Fumarate hydratase (FH) is an evolutionary conserved TCA cycle enzyme that reversibly catalyzes the hydration of fumarate to L-malate and has a moonlight function in the DNA damage response (DDR). Interestingly, FH has a contradictory cellular function, as it is pro-survival through its role in the TCA cycle, yet its loss can drive tumorigenesis. Here, we found that in both non-cancerous (HEK-293T) and cancerous cell lines (HepG2), the cell response to FH loss is separated into two distinct time frames based on cell proliferation and DNA damage repair. During the early stages of FH loss, cell proliferation rate and DNA damage repair are inhibited. However, over time the cells overcome the FH loss and form knockout clones, indistinguishable from WT cells with respect to their proliferation rate. Due to the FH loss effect on DNA damage repair, we assumed that the recovered cells bear adaptive mutations. Therefore, we applied whole-exome sequencing to identify such mutated genes systematically. Indeed, we identified recurring mutations in genes belonging to central oncogenic signaling pathways, such as JAK/STAT3, which we validated in impaired FH-KO clones. Intriguingly, we demonstrate that these adaptive mutations are responsible for FH-KO cell proliferation under TCA cycle malfunction.
延胡索酸水合酶（FH）是一种进化保守的三羧酸循环酶，它可逆地催化延胡索酸水合生成L-苹果酸，并且在DNA损伤应答（DDR）中具有兼性功能。有趣的是，FH具有矛盾的细胞功能，因为它通过在三羧酸循环中的作用促进细胞存活，但其缺失却可驱动肿瘤发生。在这里，我们发现，在非癌细胞系（HEK-293T）和癌细胞系（HepG2）中，基于细胞增殖和DNA损伤修复，细胞对FH缺失的反应可分为两个不同的时间框架。在FH缺失的早期阶段，细胞增殖速率和DNA损伤修复受到抑制。然而，随着时间的推移，细胞克服了FH缺失并形成基因敲除克隆，其增殖速率与野生型细胞无异。由于FH缺失对DNA损伤修复有影响，我们推测恢复的细胞带有适应性突变。因此，我们应用全外显子组测序来系统地鉴定此类突变基因。事实上，我们在属于核心致癌信号通路的基因中鉴定出了反复出现的突变，如JAK/STAT3，我们在受损的FH基因敲除克隆中对其进行了验证。有趣的是，我们证明这些适应性突变是三羧酸循环功能异常情况下FH基因敲除细胞增殖的原因。
