PO-095 PIM kinases in the regulation of prostate cancer cell motility

Abstract

Introduction Pim kinases are constitutively active serine/threonine kinases that are upregulated by the JAK/STAT pathway and are often overexpressed in advanced human haematological and solid cancers. There they have been observed to enhance cancer cell growth, survival and energy metabolism. Using both cell-based and animal models, we have shown that PIM kinases also efficiently promote cancer cell migration, invasion and metastasis formation. In addition, we have identified several substrates to mediate the PIM-dependent effects. Material and methods Motility of PC-3 prostate cancer cells was analysed by cell-based assays, such as wound healing assays with single cell tracking method, Boyden chamber assays and adhesion assays. The effects of PIM kinases on tumour growth were studied using subcutaneous and orthotopic mouse models for human prostate cancer. The interactions of PIM kinases and their substrates were investigated by in vitro kinase assays as well as microscopic techniques such as proximity ligation assay and fluorescence lifetime imaging. To reveal PIM-dependent functions, we used PIM-selective chemical inhibitors, transient or stable PIM upregulation as well as PIM silencing by RNA interference or CRISPR/Cas9-based gene editing. Results and discussions PIM upregulation was shown to promote prostate cancer cell motility both in cell-based wound healing assays and in the orthotopically inoculated xenografts. By contrast, inhibition of PIM kinase activity by the pyrrolocarbazole compound DHPCC-9 decreased cell migration, invasion and adhesion as well as tumour growth, angiogenesis, lymphangiogenesis and formation of metastases. Furthermore, the PIM-dependent effects were shown to be mediated by the ability of PIM kinases to phosphorylate several key substrates, such as CXCR4, FOXP3, GSK3B, NFATC1 and NOTCH1. More recently, we have observed PIM kinases to influence also the actin cytoskeleton and have identified actin-regulating proteins as novel PIM substrates. Conclusion PIM kinases are promising targets for anti-cancer drug development, not only for their roles as pro-survival factors but also as pro-migratory factors. By inhibiting PIM kinases, it may be possible to simultaneously regulate many different PIM substrates that are essential for metastatic tumour growth.