Catalan Institute of Oncology, Girona (ICO-Girona), Dr. Josep Trueta University Hospital, Ctra. França s/n, 17007, Girona, Catalonia, Spain.
Breast Cancer Res Treat. 2011 Apr;126(2):355-64. doi: 10.1007/s10549-010-0924-x. Epub 2010 May 11.
We here demonstrate that the anti-diabetic drug metformin interacts synergistically with the anti-HER2 monoclonal antibody trastuzumab (Tzb; Herceptin™) to eliminate stem/progenitor cell populations in HER2-gene-amplified breast carcinoma cells. When using the mammosphere culture technique, graded concentrations of single-agent metformin (range 50-1,000 μmol/l) were found to dose-dependently reduce the number of mammospheres formed by SKBR3 (a Tzb-naïve model), SKBR3 TzbR (a model of acquired auto-resistance to Tzb) and JIMT-1 (a model of refractoriness to Tzb and other HER2-targeted therapies ab initio) HER2-overexpressing breast cancer cells. Single-agent Tzb likewise reduced mammosphere-forming efficiency (MSFE) in Tzb-naïve SKBR3 cells, but it failed to significantly decrease MSFE in Tzb-resistant SKBR3 TzbR and JIMT-1 cells. Of note, CD44-overexpressing Tzb-refractory SKBR3 TzbR and JIMT-1 cells retained an exquisite sensitivity to single-agent metformin. Concurrent combination of metformin with Tzb synergistically reduced MSFE as well as the size of mammospheres in Tzb-refractory SKBR3 TzbR and JIMT-1 cells. Flow cytometry analyses confirmed that metformin and Tzb functioned synergistically to down-regulate the percentage of Tzb-refractory JIMT-1 cells displaying the CD44(pos)/CD24(neg/low) stem/progenitor immunophenotype. Given that MSFE and mammosphere size are indicators of stem self-renewal and progenitor cell proliferation, respectively, our current findings reveal for the first time that: (a) Tzb refractoriness in HER2 overexpressors can be explained in terms of Tzb-resistant/CD44-overexpressing/tumor-initiating stem cells; (b) metformin synergistically interacts with Tzb to suppress self-renewal and proliferation of cancer stem/progenitor cells in HER2-positive carcinomas.
我们在此证明，抗糖尿病药物二甲双胍与抗 HER2 单克隆抗体曲妥珠单抗（Tzb；赫赛汀™）协同作用，消除 HER2 基因扩增乳腺癌细胞中的干细胞/祖细胞群体。当使用乳腺球体培养技术时，发现单剂二甲双胍（范围 50-1000μmol/L）的浓度呈剂量依赖性地降低了 SKBR3（Tzb 初治模型）、SKBR3 TzbR（Tzb 获得性自身耐药模型）和 JIMT-1（Tzb 和其他 HER2 靶向治疗初治耐药模型）HER2 过表达乳腺癌细胞形成的乳腺球体数量。单剂 Tzb 同样降低了 Tzb 初治 SKBR3 细胞的乳腺球体形成效率（MSFE），但它不能显著降低 Tzb 耐药 SKBR3 TzbR 和 JIMT-1 细胞的 MSFE。值得注意的是，CD44 过表达的 Tzb 耐药 SKBR3 TzbR 和 JIMT-1 细胞对单剂二甲双胍仍保持极高的敏感性。二甲双胍与 Tzb 联合使用协同降低了 Tzb 耐药 SKBR3 TzbR 和 JIMT-1 细胞的 MSFE 和乳腺球体的大小。流式细胞术分析证实，二甲双胍和 Tzb 协同作用下调 Tzb 耐药 JIMT-1 细胞中表现出 CD44(pos)/CD24(neg/low)干细胞/祖细胞免疫表型的比例。鉴于 MSFE 和乳腺球体的大小分别是干细胞自我更新和祖细胞增殖的指标，我们目前的发现首次揭示：（a）HER2 过表达者的 Tzb 耐药性可以用 Tzb 耐药/CD44 过表达/肿瘤起始干细胞来解释；（b）二甲双胍与 Tzb 协同作用，抑制 HER2 阳性癌中的癌症干细胞/祖细胞的自我更新和增殖。
