Abelson interactor 1 (Abi1) in colorectal cancer. From synaptic plasticity to tumor cell migration]

Background. Invasion and metastatic dissemination of tumor cells defines the prognosis of patients with colorectal cancer (CRC). The Abelson interactor 1 (Abi1), a 65 kD substrate of the eponymous Abelson tyrosine kinase, interacts with phosphatidylinositol-3-kinase (PI3K) and heterogeneous nuclear ribonucleoprotein K (hnRNP K) and is a key regulator of cytoskeletal reorganization during synaptic maturation and cellular migration. Aim. The aim of this study was the analysis of Abi1 expression patterns and to elucidate the role in cytoskeletal reorganization in colorectal carcinoma cells. Material and methods. The methods used in this study were immunohistochemistry; immunofluorescence microscopy; liposomal transfection and protein analysis by Western blotting. Results. The results showed that Abi1 is expressed at the invasive front of colorectal carcinomas and localizes to the leading edge of lamellipodia in cultured colorectal carcinoma cells. A phosphorylated isoform of Abi1 that stains positively in these microcompartments disappears after treatment with the tyrosine kinase inhibitor STI571 (GlivecA (R)). The RNA interference (RNAi) approach knockdown of Abi1 as well as treatment with STI571 induce a shift in cellular morphology from broad lamellipodia-like to thin filopodia-like cellular protrusions. Discussion. The initial results support a central role for phosphorylated Abi1 in the formation of lamellipodia-like cellular protrusions as a prerequisite for cellular migration of colorectal carcinoma cells. As phosphorylation of Abi1 could be pharmaceutically targeted with STI571, this indicates a possible therapeutic option to prevent the gain of a metastatic phenotype in colorectal cancer. This possibility will be further evaluated in ongoing research.