Department of Pathology, Beijing Tiantan Hospital, Capital Medical University, Beijing, China.
Department of Internal Medicine, Department of Pharmacology, Quillen College of Medicine, East Tennessee State University, Johnson City, United States.
Neoplasma. 2020 Mar;67(2):379-388. doi: 10.4149/neo_2020_190604N486. Epub 2020 Feb 9.
Multidrug resistance (MDR) in breast cancer treatment is the major cause leading to the failure of chemotherapy. P-glycoprotein (P-gp), the product of the human MDR1 gene, plays a key role in resistance to chemotherapy and confers cross-resistance to many structurally unrelated anticancer drugs. We have previously reported that integrin αvβ6 plays a critical role in breast cancer invasion and metastasis. However, whether and how αvβ6 is associated with P-gp and regulated by potential genetic mechanisms in breast cancer remains unclear. In the present study, we further investigated the reversal effect and underlying mechanisms of MDR in breast cancer. Two small interfering RNA constructs (pSUPER-β6shRNAs) targeting two different regions of the β6 gene have been designed to inhibit αvβ6 expression by transfecting them into adriamycin-resistant MCF-7/ADR cell lines. Suppression of αvβ6 dramatically downregulated the levels of MDR1 gene mRNA and P-gp. In particular, β6shRNA-mediated silencing of αvβ6 gene increased significantly the cellular accumulation of Rhodamine 123 and markedly decreased drug efflux ability, suggesting that β6shRNAs indeed inhibit P-gp mediated drug efflux and effectively overcome drug resistance. In addition, inhibition of integrin αvβ6 suppressed the expression of ERK1/2. Interestingly, our data demonstrate that suppression of integrin αvβ6 caused significant downregulation of Bcl-2, Bcl-xL and upregulation of caspase 3, Bad, accompanied by increasing activity of cytochrome C. A possible connection between αvβ6 and P-gp in drug resistance biology is suggested. Taken together, β6shRNA could efficiently inhibit αvβ6 and MDR1 expression in vitro and these findings may offer specifically useful means to reverse MDR in breast cancer therapy.
多药耐药（MDR）在乳腺癌治疗中是导致化疗失败的主要原因。P-糖蛋白（P-gp）是人类 MDR1 基因的产物，在化疗耐药中起着关键作用，并赋予许多结构上无关的抗癌药物交叉耐药性。我们之前报道过整合素αvβ6 在乳腺癌侵袭和转移中起着关键作用。然而，αvβ6 是否以及如何与 P-gp 相关联，并受乳腺癌中潜在遗传机制的调节，目前尚不清楚。在本研究中，我们进一步研究了乳腺癌中 MDR 的逆转作用及其潜在机制。设计了两个针对β6 基因两个不同区域的短发夹 RNA 构建体（pSUPER-β6shRNAs），通过转染阿霉素耐药 MCF-7/ADR 细胞系来抑制αvβ6 的表达。αvβ6 的抑制显著下调了 MDR1 基因 mRNA 和 P-gp 的水平。特别是，β6shRNA 介导的αvβ6 基因沉默显著增加了 Rhodamine 123 的细胞内积累，并显著降低了药物外排能力，表明β6shRNAs 确实抑制了 P-gp 介导的药物外排并有效地克服了耐药性。此外，整合素αvβ6 的抑制抑制了 ERK1/2 的表达。有趣的是，我们的数据表明，抑制整合素αvβ6 导致 Bcl-2、Bcl-xL 的表达显著下调，caspase 3、Bad 的表达上调，同时伴随着细胞色素 C 活性的增加。提示αvβ6 与 P-gp 在耐药生物学中存在联系。综上所述，β6shRNA 可以有效地抑制体外αvβ6 和 MDR1 的表达，这些发现可能为逆转乳腺癌治疗中的 MDR 提供特别有用的手段。
