Zhao Xiaoya, Fu Jianfei, Tang Wanfen, Yu Liangliang, Xu Wenxia
Central Laboratory, Jinhua Hospital of Zhejiang University, Jinhua 321000, Zhejiang Province, People's Republic of China.
Department of Medical Oncology, Sir Run Run Shaw Hospital, Medical School of Zhejiang University, Hangzhou 310000, Zhejiang Province, People's Republic of China.
Onco Targets Ther. 2020 May 29;13:4833-4842. doi: 10.2147/OTT.S246430. eCollection 2020.
Serine provides important precursors of protein, lipid, and nucleotide synthesis needed for tumor cell growth. Phosphoglycerate dehydrogenase (PHGDH), a key rate-limiting enzyme in the serine de novo synthesis pathway, is highly expressed in many tumor types (including gastric cancer) and negatively correlated with overall survival. Cisplatin is a chemotherapeutic drug commonly used in the treatment of gastric cancer. In this study, we mainly investigated the relationship between serine metabolism and resistance to cisplatin in gastric cancer cells, as well as the regulatory mechanism involved in this process.
We determined the effect of different concentrations of serine or a PHGDH inhibitor combined with cisplatin or oxaliplatin on the viability and apoptosis of SGC7901, BGC823, and MGC803 cells via the Cell Counting Kit-8 and Hoechst 33258 staining, respectively. Western blotting was utilized to detect the relative protein expression. Furthermore, we investigated DNA damage through the micrococcal nuclease sensitivity assay detected using agarose gels.
We found that reduced concentrations of serine or inhibition of PHGDH hindered the toxicity and pro-apoptotic effects of cisplatin on gastric cancer cells. Moreover, the addition of serine could reverse the sensitivity of gastric cancer cells to cisplatin. Moreover, we found that DNA damage was reduced by treatment with PHGDH inhibitor NCT-503 or CBR-5884. Inhibition of serine metabolism induced a decrease in H3K4 tri-methylation, which was reversed by JIB-04 (inhibitor of H3K4 demethylase). The tolerance of gastric cancer cells to cisplatin was relieved by JIB-04. Through micrococcal nuclease experiments, we further found that inhibiting the activity of PHGDH strengthened chromatin tightness.
Inhibition of serine metabolism reduced H3K4 tri-methylation and increased the density of chromatin, which leads to decreased toxicity and pro-apoptotic effect of platinum chemotherapeutic drugs on gastric cancer cells.
丝氨酸为肿瘤细胞生长所需的蛋白质、脂质和核苷酸合成提供重要前体。磷酸甘油酸脱氢酶（PHGDH）是丝氨酸从头合成途径中的关键限速酶，在许多肿瘤类型（包括胃癌）中高表达，且与总生存期呈负相关。顺铂是治疗胃癌常用的化疗药物。在本研究中，我们主要探究了丝氨酸代谢与胃癌细胞对顺铂耐药性之间的关系，以及该过程涉及的调控机制。
我们分别通过细胞计数试剂盒-8和Hoechst 33258染色，测定不同浓度的丝氨酸或PHGDH抑制剂与顺铂或奥沙利铂联合使用对SGC7901、BGC823和MGC803细胞活力和凋亡的影响。利用蛋白质免疫印迹法检测相关蛋白的表达水平。此外，我们通过琼脂糖凝胶检测微球菌核酸酶敏感性试验来研究DNA损伤情况。
我们发现，丝氨酸浓度降低或PHGDH受到抑制会阻碍顺铂对胃癌细胞的毒性作用和促凋亡效应。此外，添加丝氨酸可逆转胃癌细胞对顺铂的敏感性。而且，我们发现用PHGDH抑制剂NCT-503或CBR-5884处理可减少DNA损伤。抑制丝氨酸代谢会导致H3K4三甲基化水平降低，而H3K4去甲基化酶抑制剂JIB-04可使其逆转。JIB-04可减轻胃癌细胞对顺铂的耐受性。通过微球菌核酸酶实验，我们进一步发现抑制PHGDH的活性会增强染色质的紧密程度。
抑制丝氨酸代谢会降低H3K4三甲基化水平并增加染色质密度，从而导致铂类化疗药物对胃癌细胞的毒性作用和促凋亡效应减弱。
