Role of Crk Adaptor Proteins in Cellular Migration and Invasion in Human Breast Cancer

摘要

The Crk adaptor proteins (CrkI, CrkII and CrkL) play an important role during cellular signalling by mediating the formation of protein complexes. We examined how the loss of Crk would affect tumor progression using RNA interference, as well as examining the consequences of Crk over-expression. For each cancer cell line tested, loss of Crk expression corresponded with a significant decrease in cell migration, invasion, and adhesion, demonstrating that Crk adaptor proteins play an important role in integrating signals of highly malignant cancer cell lines. To formally test this in vivo, Crk was down- regulated using shRNA in breast cancer cells that have a high propensity to form bone metastases. Loss of Crk was associated with a significant decrease in the formation of bone metastases, as well as growth at both the primary and secondary sites. Loss of Crk was also associated with decreases in Rac and Cdc42 activation. These data demonstrate that Crk adaptor proteins play a role in breast cancer progression, however whether Crk proteins can lead to breast cancer development has not been addressed. To test this, transgenic mice over- expressing Crk in the mammary epithelium were established. Transgenic CrkI and CrkII mice undergoing puberty were found to have delayed ductal outgrowth. In post-pubertal CrkII mice, precocious ductal branching was observed, which was associated with enhanced proliferation. Focal mammary tumors or hyperplasias appeared in 18% of CrkII transgenic animals, with an average latency of 14 months. Thus, the present study demonstrates that the Crk adaptor proteins play an important role in integrating signals for mammary gland development and breast cancer progression.