Li J N, Gorospe M, Chrest F J, Kumaravel T S, Evans M K, Han W F, Pizer E S
Department of Pathology, Johns Hopkins Medical Institutions, Gerontology Research Center, National Institut on Aging, Baltimore, Maryland 21224, USA.
Cancer Res. 2001 Feb 15;61(4):1493-9.
Fatty acid synthetic metabolism is abnormally elevated in tumor cells, and pharmacological inhibitors of the anabolic enzyme fatty acid synthase (FAS), including the natural product cerulenin and the novel synthetic compound c75, are selective inhibitors of tumor cell growth. We have recently reported that these two FAS inhibitors both produce rapid, potent inhibition of DNA replication and S-phase progression in human cancer cells, as well as apoptotic death. Here we report an additional characterization of the cellular response to FAS inhibition. RKO colon carcinoma cells were selected for study because they undergo little apoptosis within the first 24 h after FAS inhibition. Instead, RKO cells exhibited a biphasic stress response with a transient accumulation in S and G2 at 4 and 8 h that corresponds to a marked reduction in cyclin A- and B1-associated kinase activities, and then by accumulation of p53 and p21 proteins at 16 and 24 h and growth arrest in G1 and G2. The response of RKO cells to FAS inhibition resembled a genotoxic stress response, but DNA damage did not appear to be an important downstream effect of FAS inhibition, because none was detected using the single cell gel electrophoresis assay (comet assay) to assess DNA damage. p53 function is probably important in protecting RKO cells from FAS inhibition because, similar to many other tumor lines, RKO cells expressing a dominant negative mutant p53 gene underwent extensive apoptosis within 24 h after FAS inhibition. Sensitization of cells to FAS inhibitors by the loss of p53 raises the possibility that these agents may be clinically useful against malignancies carrying p53 mutations. Whereas induction of apoptosis appeared related to accumulation of the substrate, malonyl-CoA, after FAS inhibition, the cytostatic effects were independent of malonyl-CoA accumulation and may have resulted from product depletion.
脂肪酸合成代谢在肿瘤细胞中异常升高，而合成代谢酶脂肪酸合酶（FAS）的药理抑制剂，包括天然产物浅蓝菌素和新型合成化合物c75，是肿瘤细胞生长的选择性抑制剂。我们最近报道，这两种FAS抑制剂均能快速、有效地抑制人类癌细胞中的DNA复制和S期进程，以及诱导凋亡死亡。在此，我们报告了对FAS抑制的细胞反应的进一步特征。选择RKO结肠癌细胞进行研究，因为它们在FAS抑制后的最初24小时内几乎不发生凋亡。相反，RKO细胞表现出双相应激反应，在4小时和8小时时S期和G2期短暂积累，这与细胞周期蛋白A和B1相关激酶活性的显著降低相对应，然后在16小时和24小时时p53和p21蛋白积累，细胞在G1期和G2期生长停滞。RKO细胞对FAS抑制的反应类似于基因毒性应激反应，但DNA损伤似乎不是FAS抑制的重要下游效应，因为使用单细胞凝胶电泳分析（彗星试验）评估DNA损伤时未检测到DNA损伤。p53功能可能在保护RKO细胞免受FAS抑制方面很重要，因为与许多其他肿瘤细胞系一样，表达显性负性突变p53基因的RKO细胞在FAS抑制后24小时内发生广泛凋亡。p53缺失使细胞对FAS抑制剂敏感，这增加了这些药物可能对携带p53突变的恶性肿瘤具有临床疗效的可能性。虽然凋亡诱导似乎与FAS抑制后底物丙二酰辅酶A的积累有关，但细胞生长抑制作用与丙二酰辅酶A的积累无关，可能是由于产物耗竭所致。
