Berg R W, Werner M, Ferguson P J, Postenka C, Vincent M, Koropatnick D J, Behrend E
Cancer Research Laboratories, The London Regional Cancer Centre, London, Ontario, Canada.
J Pharmacol Exp Ther. 2001 Aug;298(2):477-84.
Chemotherapeutic agents targeting thymidylate synthase (TS) are effective against human tumors. Efficacy is limited by drug resistance, often mediated by TS overexpression. Treatment of HeLa cells in vitro with an antisense oligodeoxynucleotide (ODN 83) targeting human TS mRNA reduces TS mRNA and protein levels, inhibits cell proliferation, and sensitizes cells to TS-targeting drugs (Ferguson et al., 1999). The present study investigates the mechanism by which ODN 83 inhibits cell proliferation and examines its antitumor efficacy in vivo. ODN 83 treatment did not induce apoptosis in HeLa cells in vitro but caused accumulation of cells at G2/M. In contrast, TS-targeting chemotherapeutics arrest at G1 or S. Antisense down-regulation reduced TS mRNA levels in human colon cancer (HT29) cells by 40% in vitro, resulted in G2/M arrest, and reduced proliferation without enhanced cell death. Growth of HT29 tumors in immunocompromised mice was significantly inhibited when antisense ODN 83 treatment began promptly after tumor implantation and was accompanied by a 40% reduction in TS protein levels. Growth of tumors allowed to reach 400 mm3 prior to ODN administration was unaffected by antisense ODN 83. Radiolabeled ODNs were localized to the tumor periphery but evenly distributed in normal tissue. Thus, down-regulation of TS mRNA and protein by antisense ODN treatment exerts a novel G2/M cell cycle block without increasing cell death and inhibits HT29 tumor cell growth in vivo. Antisense ODN 83 may be an effective therapy for colon carcinoma, alone or in combination with TS-targeting cytotoxic drugs.
靶向胸苷酸合成酶（TS）的化疗药物对人类肿瘤有效。疗效受到耐药性的限制，耐药性通常由TS过表达介导。用靶向人类TS mRNA的反义寡脱氧核苷酸（ODN 83）体外处理HeLa细胞可降低TS mRNA和蛋白质水平，抑制细胞增殖，并使细胞对靶向TS的药物敏感（Ferguson等人，1999年）。本研究调查了ODN 83抑制细胞增殖的机制，并检测了其体内抗肿瘤疗效。ODN 83处理在体外未诱导HeLa细胞凋亡，但导致细胞在G2/M期积累。相比之下，靶向TS的化疗药物使细胞停滞在G1期或S期。反义下调在体外使人类结肠癌细胞（HT29）中的TS mRNA水平降低40%，导致G2/M期停滞，并减少增殖而不增加细胞死亡。当在肿瘤植入后立即开始用反义ODN 83处理时，免疫缺陷小鼠体内HT29肿瘤的生长受到显著抑制，同时TS蛋白水平降低40%。在给予ODN之前肿瘤体积达到400 mm3的肿瘤生长不受反义ODN 83的影响。放射性标记的ODN定位于肿瘤周边，但在正常组织中均匀分布。因此，反义ODN处理下调TS mRNA和蛋白质水平可产生一种新的G2/M期细胞周期阻滞，而不增加细胞死亡，并在体内抑制HT29肿瘤细胞生长。反义ODN 83单独或与靶向TS的细胞毒性药物联合使用可能是结肠癌的一种有效治疗方法。
