AbstractChemotherapy is one of the

Abstract

Chemotherapy is one of the few effective choices for patients with advanced or recurrent gastric cancer (GC). However, the development of mutidrug resistance (MDR) to cancer chemotherapy is a major obstacle to the effective treatment of advanced GC. Additionally, the mechanism of MDR remains to be determined. In the present study, we tested IC50 of cisplating (DDP), vincristine (VCR) and 5-fluorouracil (5-FU) in SGC7901, SGC7901/DDP and SGC7901/VCR gastric cancer cells using an MTT assay. The expression of let-7b and c-Myc in these cells was detected by qPCR and western blot analysis. The relationship between let-7b and c-Myc was explored using a luciferase reporter assay. Transfection of let-7b mimic or inhibitor was used to confirm the effect of let-7b on drug sensitivity in chemotherapy via the regulation of c-Myc expression. We found that the expression of let-7b was lower in chemotherapy-resistant SGC7901/DDP and SGC7901/VCR gastric cancer cells than that in chemotherapy-sensitive SGC7901 cells. By contrast, the expression of c-Myc was higher in SGC7901/DDP and SGC7901/VCR cells than that in SGC7901 cells. Furthermore, we confirmed that let-7b suppresses c-Myc gene expression at the mRNA and protein levels in a sequence-specific manner, while transfection of let-7b mimic increases drug sensitivity in chemotherapy-resistant SGC7901/DDP and SGC7901/VCR cells by targeting downregulation of c-Myc. In SGC7901 drug-sensitive cells, however, the sensitivity of chemotherapy was significantly decreased following let-7b inhibitor transfection. The present study results demonstrated that let-7b increases drug sensitivity in chemotherapy‑resistant SGC7901/DDP and SGC7901/VCR gastric cancer cells by targeting the downregulation of c-Myc and that, let-7b mimic reverses MDR by promoting cancer stem cell differentiation controlled by double-negative autoregulatory loops (Lin28/let-7 and Myc/let-7) and a double-positive autoregulatory loop (Lin28/Lin28B/Myc) existing in GC cells, which remains to be confirmed.

結果 (中文) 1:

摘要Chemotherapy is one of the few effective choices for patients with advanced or recurrent gastric cancer (GC). However, the development of mutidrug resistance (MDR) to cancer chemotherapy is a major obstacle to the effective treatment of advanced GC. Additionally, the mechanism of MDR remains to be determined. In the present study, we tested IC50 of cisplating (DDP), vincristine (VCR) and 5-fluorouracil (5-FU) in SGC7901, SGC7901/DDP and SGC7901/VCR gastric cancer cells using an MTT assay. The expression of let-7b and c-Myc in these cells was detected by qPCR and western blot analysis. The relationship between let-7b and c-Myc was explored using a luciferase reporter assay. Transfection of let-7b mimic or inhibitor was used to confirm the effect of let-7b on drug sensitivity in chemotherapy via the regulation of c-Myc expression. We found that the expression of let-7b was lower in chemotherapy-resistant SGC7901/DDP and SGC7901/VCR gastric cancer cells than that in chemotherapy-sensitive SGC7901 cells. By contrast, the expression of c-Myc was higher in SGC7901/DDP and SGC7901/VCR cells than that in SGC7901 cells. Furthermore, we confirmed that let-7b suppresses c-Myc gene expression at the mRNA and protein levels in a sequence-specific manner, while transfection of let-7b mimic increases drug sensitivity in chemotherapy-resistant SGC7901/DDP and SGC7901/VCR cells by targeting downregulation of c-Myc. In SGC7901 drug-sensitive cells, however, the sensitivity of chemotherapy was significantly decreased following let-7b inhibitor transfection. The present study results demonstrated that let-7b increases drug sensitivity in chemotherapy‑resistant SGC7901/DDP and SGC7901/VCR gastric cancer cells by targeting the downregulation of c-Myc and that, let-7b mimic reverses MDR by promoting cancer stem cell differentiation controlled by double-negative autoregulatory loops (Lin28/let-7 and Myc/let-7) and a double-positive autoregulatory loop (Lin28/Lin28B/Myc) existing in GC cells, which remains to be confirmed.

結果 (中文) 3:

摘要：化疗是治疗晚期或复发性胃癌的有效选择之一。然而，对多药耐药（MDR）的发展，癌症化疗是晚期胃癌的有效治疗的主要障碍。此外，MDR的机制仍有待确定。在本研究中，我们测试了其cisplating（DDP），长春新碱（VCR）和5-氟尿嘧啶（5-FU）在胃癌细胞SGC7901，SGC7901／DDP和SGC7901/VCR采用MTT法检测胃癌细胞。通过荧光定量PCR和Western blot法检测let-7b和c-myc基因在这些细胞中的表达。let-7b和c-myc之间的关系用荧光素酶报告基因分析的探讨。Let-7b模仿或抑制剂转染法确定对化疗药物敏感性的影响通过let-7b c-myc基因表达的调节。我们发现，在化疗耐药的SGC7901／DDP和SGC7901/VCR胃癌细胞SGC7901细胞比化疗敏感let-7b表达量较低。对比，c-myc原癌基因的表达明显高于SGC7901／DDP和SGC7901/VCR细胞高于SGC7901细胞。此外，我们发现let-7b抑制c-myc基因的表达在一个序列特异性的mRNA和蛋白水平，而let-7b模仿增加化疗耐药的SGC7901／DDP和SGC7901/VCR细胞靶向药物敏感性下调c-myc基因转染。然而在药物敏感细胞，胃癌，化疗敏感性明显降低以下let-7b inhibitor转染。目前的研究结果表明，增加化疗药物敏感性let-7b在抗‑SGC7901/DDP和SGC7901/VCR通过下调c-myc和胃癌细胞，let-7b模仿逆转MDR的促癌干细胞分化的双负调节闭环控制（Lin28 / let-7和MYC / let-7）和双阳性调节回路（Lin28 /基因/基因）在胃癌细胞存在有待证实。