Reim Florian, Dombrowski Yvonne, Ritter Cathrin, Buttmann Mathias, Häusler Sebastian, Ossadnik Monika, Krockenberger Mathias, Beier Dagmar, Beier Christoph P, Dietl Johannes, Becker Jürgen C, Hönig Arnd, Wischhusen Jörg
Department for Obstetrics and Gynecology, University of Würzburg, Würzburg, Germany.
Cancer Res. 2009 Oct 15;69(20):8058-66. doi: 10.1158/0008-5472.CAN-09-0834. Epub 2009 Oct 13.
Although trastuzumab (Herceptin) has substantially improved the overall survival of patients with mammary carcinomas, even initially well-responding tumors often become resistant. Because natural killer (NK) cell-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) is thought to contribute to the therapeutic effects of trastuzumab, we have established a cell culture system to select for ADCC-resistant SK-OV-3 ovarian cancer and MCF7 mammary carcinoma cells. Ovarian cancer cells down-regulated HER2 expression, resulting in a more resistant phenotype. MCF7 breast cancer cells, however, failed to develop resistance in vitro. Instead, treatment with trastuzumab and polyclonal NK cells resulted in the preferential survival of individual sphere-forming cells that displayed a CD44(high)CD24(low) "cancer stem cell-like" phenotype and expressed significantly less HER2 compared with non-stem cells. Likewise, the CD44(high)CD24(low) population was also found to be more immunoresistant in SK-BR3, MDA-MB231, and BT474 breast cancer cell lines. When immunoselected MCF7 cells were then re-expanded, they mostly lost the observed phenotype to regenerate a tumor cell culture that displayed the initial HER2 surface expression and ADCC-susceptibility, but was enriched in CD44(high)CD24(low) cancer stem cells. This translated into increased clonogenicity in vitro and tumorigenicity in vivo. Thus, we provide evidence that the induction of ADCC by trastuzumab and NK cells may spare the actual tumor-initiating cells, which could explain clinical relapse and progress. Moreover, our observation that the "relapsed" in vitro cultures show practically identical HER2 surface expression and susceptibility toward ADCC suggests that the administration of trastuzumab beyond relapse might be considered, especially when combined with an immune-stimulatory treatment that targets the escape variants.
尽管曲妥珠单抗（赫赛汀）已显著提高了乳腺癌患者的总生存率，但即使是最初反应良好的肿瘤也常常会产生耐药性。由于自然杀伤（NK）细胞介导的抗体依赖性细胞介导的细胞毒性（ADCC）被认为有助于曲妥珠单抗的治疗效果，我们建立了一种细胞培养系统，以筛选出对ADCC耐药的SK-OV-3卵巢癌细胞和MCF7乳腺癌细胞。卵巢癌细胞下调了HER2表达，从而产生了更具耐药性的表型。然而，MCF7乳腺癌细胞在体外未能产生耐药性。相反，用曲妥珠单抗和多克隆NK细胞处理导致单个成球细胞优先存活，这些细胞呈现CD44(高)CD24(低)的“癌症干细胞样”表型，与非干细胞相比，HER2表达显著降低。同样，在SK-BR3、MDA-MB231和BT474乳腺癌细胞系中也发现CD44(高)CD24(低)群体对免疫更具抗性。当对免疫筛选的MCF7细胞进行再扩增时，它们大多失去了观察到的表型，重新生成了一种肿瘤细胞培养物，该培养物显示出最初的HER2表面表达和对ADCC的敏感性，但富含CD44(高)CD24(低)癌症干细胞。这转化为体外克隆形成能力的增强和体内致瘤性的增强。因此，我们提供的证据表明，曲妥珠单抗和NK细胞诱导的ADCC可能会使实际的肿瘤起始细胞存活，这可以解释临床复发和进展。此外，我们观察到“复发”的体外培养物显示出几乎相同的HER2表面表达和对ADCC的敏感性，这表明可以考虑在复发后给予曲妥珠单抗，尤其是与针对逃逸变体的免疫刺激治疗联合使用时。
