Epithelial–mesenchymal transition (EMT) is a cell plasticity process required for metastasis and chemoresistance of carcinoma cells. We report a crucial role of the signal adaptor proteins CRK and CRKL in promoting EMT and tumor aggressiveness, as well as resistance against chemotherapy in colorectal and pancreatic carcinoma. Genetic loss of either CRKL or CRK partially counteracted EMT in three independent cancer cell lines. Strikingly, complete loss of the CRK family shifted cells strongly toward the epithelial phenotype. Cells exhibited greatly increased E‐cadherin and grew as large, densely packed clusters, completely lacked invasiveness and the ability to undergo EMT induced by cytokines or genetic activation of SRC. Furthermore, CRK family‐deficiency significantly reduced cell survival, proliferation and chemoresistance, as well as ERK1/2 phosphorylation and c‐MYC protein levels. In accordance, MYC‐target gene expression was identified as novel hallmark process positively regulated by CRK family proteins. Mechanistically, CRK proteins were identified as pivotal amplifiers of SRC/FAK signaling at focal adhesions, mediated through a novel positive feedback loop depending on RAP1. Expression of the CRK family and the EMT regulator ZEB1 was significantly correlated in samples from colorectal cancer patients, especially in invasive regions. Further, high expression of CRK family genes was significantly associated with reduced survival in locally advanced colorectal cancer, as well as in pan‐cancer datasets from the TCGA project. Thus, CRK family adaptor proteins are promising therapeutic targets to counteract EMT, chemoresistance, metastasis formation and minimal residual disease. As proof of concept, CRK family‐mediated oncogenic signaling was successfully inhibited by a peptide‐based inhibitor.

中文翻译：

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CRK衔接蛋白作为SRC / FAK信号转导上皮-间质转化和结肠直肠癌侵袭的必要成分的新作用。

上皮间质转化（EMT）是癌细胞转移和化学耐药所必需的细胞可塑性过程。我们报告了信号适配器蛋白CRK和CRKL在促进EMT和肿瘤侵袭性以及对大肠癌和胰腺癌的化学耐药性中的关键作用。在三个独立的癌细胞系中，CRKL或CRK的遗传损失部分抵消了EMT。令人惊讶的是，CRK家族的完全丧失使细胞强烈朝着上皮表型转移。细胞表现出大大增加的E-钙黏着蛋白，并生长成大而密集的簇，完全缺乏侵袭性，并且缺乏由细胞因子或SRC的遗传激活诱导的EMT的能力。此外，CRK家族缺陷会大大降低细胞存活，增殖和化学抗药性，以及ERK1 / 2磷酸化和c-MYC蛋白水平。因此，MYC靶基因表达被鉴定为由CRK家族蛋白正调控的新标志性过程。从机制上讲，CRK蛋白被确定为粘着斑上SRC / FAK信号转导的关键放大器，通过依赖于RAP1的新型正反馈回路介导。表达CRK家族和EMT调节剂ZEB1在大肠癌患者的样品中，特别是在浸润区域中，显着相关。此外，CRK家族基因的高表达与局部晚期结直肠癌以及TCGA项目的全癌数据集的存活率降低显着相关。因此，CRK家族衔接子蛋白是有望抵消EMT，化学抗性，转移形成和最小残留疾病的治疗靶标。作为概念的证明，CRK家族介导的致癌信号已被基于肽的抑制剂成功抑制。