The role if insulin-like growth factor binding protein-2 (IGFBP-2) in mediating chemoresistance in breast cancer cells has been demonstrated, but the mechanism of action is unclear. This study aimed to further investigate the role of IGFBP-2 in the DNA damage response induced by etoposide in MCF-7, T47D (ER+ve), and MDA-MB-231 (ER-ve) breast cancer cell lines. In the presence or absence of etoposide, IGFBP-2 was silenced using siRNA in the ER-positive cell lines, or exogenous IGFBP-2 was added to the ER-negative MDA-MB-231 cells. Cell number and death were assessed using trypan blue dye exclusion assay, changes in abundance of proteins were monitored using Western blotting of whole cell lysates, and localization and abundance were determined using immunofluorescence and cell fractionation. Results from ER-positive cell lines demonstrated that upon exposure to etoposide, loss of IGFBP-2 enhanced cell death, and this was associated with a reduction in P-DNA-PKcs and an increase in γH2AX. Conversely, with ER-negative cells, the addition of IGFBP-2 in the presence of etoposide resulted in cell survival, an increase in P-DNA-PKcs, and a reduction in γH2AX. In summary, IGFBP-2 is a survival factor for breast cancer cells that is associated with enhancement of the DNA repair mechanism.
胰岛素样生长因子结合蛋白-2（IGFBP-2）在介导乳腺癌细胞化疗耐药中的作用已被证实，但其作用机制尚不明确。本研究旨在进一步探究IGFBP-2在依托泊苷诱导的MCF-7、T47D（ER阳性）和MDA-MB-231（ER阴性）乳腺癌细胞系DNA损伤反应中的作用。在依托泊苷存在或缺失条件下，通过siRNA在ER阳性细胞系中沉默IGFBP-2表达，或在ER阴性的MDA-MB-231细胞中外源性添加IGFBP-2。采用台盼蓝染色排除法评估细胞数量与死亡情况，通过全细胞裂解液蛋白质印迹法监测蛋白丰度变化，并运用免疫荧光和细胞分馏技术测定蛋白定位与丰度。ER阳性细胞系实验结果显示：暴露于依托泊苷时，IGFBP-2缺失会促进细胞死亡，该现象与磷酸化DNA-PKcs减少及γH2AX增加相关。相反，在ER阴性细胞中，依托泊苷存在条件下添加IGFBP-2可提高细胞存活率，同时增加磷酸化DNA-PKcs并减少γH2AX。综上所述，IGFBP-2作为乳腺癌细胞的生存因子，其作用机制与增强DNA修复功能密切相关。
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