Drug Resistance Group, Centre for Cancer Research and Cell Biology, Queen's University Belfast, Belfast, Northern Ireland.
Cancer Res. 2011 Feb 1;71(3):1071-80. doi: 10.1158/0008-5472.CAN-10-0714. Epub 2010 Dec 10.
Oncogenic mutations in Kras occur in 40% to 45% of patients with advanced colorectal cancer (CRC). We have previously shown that chemotherapy acutely activates ADAM17, resulting in growth factor shedding, growth factor receptor activation, and drug resistance in CRC tumors. In this study, we examined the role of mutant Kras in regulating growth factor shedding and ADAM17 activity, using isogenic Kras mutant (MT) and wild-type (WT) HCT116 CRC cells. Significantly higher levels of TGF-α and VEGF were shed from KrasMT HCT116 cells, both basally and following chemotherapy treatment, and this correlated with increased pErk (phosphorylated extracellular signal regulated kinase)1/2 levels and ADAM17 activity. Inhibition of Kras, MEK (MAP/ERK kinase)1/2, or Erk1/2 inhibition abrogated chemotherapy-induced ADAM17 activity and TGF-α shedding. Moreover, we found that these effects were not drug or cell line specific. In addition, MEK1/2 inhibition in KrasMT xenografts resulted in significant decreases in ADAM17 activity and growth factor shedding in vivo, which correlated with dramatically attenuated tumor growth. Furthermore, we found that MEK1/2 inhibition significantly induced apoptosis both alone and when combined with chemotherapy in KrasMT cells. Importantly, we found that sensitivity to MEK1/2 inhibition was ADAM17 dependent in vitro and in vivo. Collectively, our findings indicate that oncogenic Kras regulates ADAM17 activity and thereby growth factor ligand shedding in a MEK1/2/Erk1/2-dependent manner and that KrasMT CRC tumors are vulnerable to MEK1/2 inhibitors, at least in part, due to their dependency on ADAM17 activity.
致癌突变 Kras 发生在 40%至 45%的晚期结直肠癌（CRC）患者中。我们之前已经表明，化疗会使 ADAM17 急性激活，导致 CRC 肿瘤中生长因子脱落、生长因子受体激活和耐药性。在这项研究中，我们使用同基因 Kras 突变（MT）和野生型（WT）HCT116 CRC 细胞，研究了突变 Kras 在调节生长因子脱落和 ADAM17 活性中的作用。KrasMT HCT116 细胞中 TGF-α 和 VEGF 的脱落水平明显更高，无论是基础水平还是化疗后，这与增加的 pErk（磷酸化细胞外信号调节激酶）1/2 水平和 ADAM17 活性相关。抑制 Kras、MEK（MAP/ERK 激酶）1/2 或 Erk1/2 抑制可消除化疗诱导的 ADAM17 活性和 TGF-α 脱落。此外，我们发现这些作用不是药物或细胞系特异性的。此外，MEK1/2 抑制在 KrasMT 异种移植物中导致 ADAM17 活性和生长因子脱落的显著降低，这与肿瘤生长明显减弱相关。此外，我们发现 MEK1/2 抑制在 KrasMT 细胞中单独或与化疗联合使用时均能显著诱导细胞凋亡。重要的是，我们发现 MEK1/2 抑制在体外和体内均依赖于 ADAM17。总之，我们的研究结果表明，致癌性 Kras 以 MEK1/2/Erk1/2 依赖性方式调节 ADAM17 活性，从而调节生长因子配体脱落，并且 KrasMT CRC 肿瘤对 MEK1/2 抑制剂敏感，至少部分原因是它们对 ADAM17 活性的依赖性。
