SORBS1 serves a metastatic role via suppression of AHNAK in colorectal cancer cell lines

Cbl-associated protein (CAP) is encoded by the sorbin and SH3 domain-containing 1 (SORBS1) gene. CAP has been reported to be associated with the actin cytoskeleton, receptor tyrosine kinase signaling and cell adhesion through interactions with various proteins. It may be hypothesized that SORBS1 has numerous unknown functions, which may include providing a favorable condition for metastasis. Although CAP has been demonstrated to possess a number of functions, the role of this protein has only been reported in metabolic signaling pathways and its function in cancer remains to be elucidated. In the present study, SORBS1 expression was detected in colorectal cancer cell lines divided into the primary group and the metastatic group by reverse transcription-quantitative PCR and western blot analysis. In addition, SORBS1 expression was manipulated by vector transfection and lentivirus transduction. The metastatic role of SORBS1, as determined by assessing its effects on cell proliferation and migration, was determined by colony formation assay, cell cycle analysis and Boyden chamber assay. To elucidate the SORBS1-binding protein, immunoprecipitation was performed. Co-localization of SORBS1 and AHNAK nucleoprotein (AHNAK) was identified by confocal microscopy. Notably, the protein expression levels of CAP were higher in SNU-769A and SW480 cells than in SNU-769B and SW620 cells. In addition, the number of colonies in the SORBS1-overexpressing group was significantly increased compared with that of the control group, as determined using the colony formation assay; the SORBS1 overexpression group formed >8-fold more colonies than the control group. The proliferative ability of the SORBS1 overexpression group was also significantly increased compared with the control group over the entire incubation period. Cell migration assays revealed that the number of migrated SORBS1-knockdown cells was reduced compared with the control in both HCT-116 and SNU-C4 cell lines; migration area was decreased to 31 and 26% in HCT-116 and SNU-C4 cell lines, respectively. Consequently, it was confirmed that SORBS1 could form a complex with AHNAK, which functions as a tumor suppressor through inhibition of phosphorylated-ERK and Rho-associated coiled-coil containing protein kinase 1. In conclusion, SORBS1 may serve a crucial role in cancer growth and migration via inhibition of AHNAK expression.