Liu X H, Blazsek I, Comisso M, Legras S, Marion S, Quittet P, Anjo A, Wang G S, Misset J L
Institut du Cancer et d'Immunogénétique, Hôpital Paul Brousse, Villejuif, France.
Eur J Cancer. 1995 Jun;31A(6):953-63. doi: 10.1016/0959-8049(95)00050-x.
Cantharidin is a natural toxin that inhibits protein phosphatase type 2A (PP2A) and has antitumour effects in man. We have studied the synthetic analogue, norcantharidin (NCTD), which has less nephrotoxic and phlogogenic side-effects, investigating the effects on the normal haemopoietic system and leukaemia cell growth. Daily intraperitoneal (i.p.) injection of NCTD induced dose and circadian time-dependent transient leucocytosis in normal mice, but did not accelerate bone marrow (BM) regeneration, or have haemopoietic offe-effects following chronic administration. NCTD stimulated the cell cycle progression of granulocyte-macrophage colony-forming cells (GM-CFC), stimulated DNA synthesis and increased the frequency of mitotic cells in short-term human BM cultures. NCTD also stimulated the production of interleukin (IL)-1 beta, colony stimulating activity (CSA) and tumour necrosis factor (TNF)-alpha. Continuous in vitro NCTD treatment, however, inhibited both DNA synthesis and GM-CFC growth. Fluorescence-activated cell sorting (FACS) analysis of DNA profiles and cytological studies in HL-60, K-562 or MRC5V2 (fibroblast) cells indicated that low doses of NCTD accelerated the G1/S phase transition, while higher doses or prolonged incubations inhibited the cell cycle at the G2/M phases or during the formation of postmitotic daughter cells. Electron microscopy revealed that NCTD impaired the neogenesis of chromatin material and nuclear membrane during the M/G1 phase transition in K-562 cells. The biphasic effect of NCTD may be due to inhibition of PP2A activity, which regulates the cell cycle, both at the restriction point and at the G2 and M phases. Our data provide new insight into the cellular and molecular actions of NCTD, and partly explain its therapeutical effects in cancer patients.
斑蝥素是一种天然毒素，可抑制2A型蛋白磷酸酶（PP2A），对人体具有抗肿瘤作用。我们研究了合成类似物去甲斑蝥素（NCTD），其肾毒性和致炎副作用较小，研究了其对正常造血系统和白血病细胞生长的影响。正常小鼠每日腹腔注射NCTD可诱导剂量和昼夜时间依赖性的短暂白细胞增多，但不会加速骨髓（BM）再生，长期给药后也没有造血副作用。NCTD刺激粒细胞-巨噬细胞集落形成细胞（GM-CFC）的细胞周期进程，刺激DNA合成，并增加短期人BM培养物中有丝分裂细胞的频率。NCTD还刺激白细胞介素（IL）-1β、集落刺激活性（CSA）和肿瘤坏死因子（TNF）-α的产生。然而，持续的体外NCTD处理会抑制DNA合成和GM-CFC生长。对HL-60、K-562或MRC5V2（成纤维细胞）细胞进行DNA谱的荧光激活细胞分选（FACS）分析和细胞学研究表明，低剂量的NCTD加速了G1/S期转换，而高剂量或延长孵育时间则在G2/M期或有丝分裂后子细胞形成过程中抑制细胞周期。电子显微镜显示，NCTD在K-562细胞的M/G1期转换过程中损害了染色质物质和核膜的新生。NCTD的双相作用可能是由于抑制了PP2A活性，PP2A活性在限制点以及G2和M期调节细胞周期。我们的数据为NCTD的细胞和分子作用提供了新的见解，并部分解释了其在癌症患者中的治疗效果。
