Semaphorin-3F suppresses the stemness of colorectal cancer cells by inactivating Rac1

Tumor cell stemness has been recognized as a key contributor to tumor initiation, progression and recurrence. Our previous studies have found that semaphorin-3F (SEMA3F), an axon guidance molecule in the development of central nervous system, inhibited the growth and metastasis of colorectal cancer (CRC). However, a possible role for SEMA3F in regulating cancer cell stemness remains unknown. Here, we report a novel mechanism of the acquirement of sternness of CRC cells regulated by SEMA3F. Knockdown of SEMA3F significantly promoted the self-renewal and tumorigenicity of CRC cells, and increased the expression of sternness-associated genes, while overexpressing SEMA3F reduced the sternness of CRC cells. Mechanistically, GTP-Rac1 was involved in SEMA3F mediated regulation of CRC cell sternness by targeting the Wnt/beta-catenin pathway. Clinically, GTP-Rac1 expression was inversely correlated with SEMA3F levels in CRC samples and patients with SEMA3F(low)/GTP-Rac1(high) CRC showed poorer prognosis. Our findings demonstrate the ability of SEMA3F to inhibit the sternness of human CRC cells by suppressing Rac1 activation, which suggests a novel therapeutic approach for CRC. (C) 2014 Elsevier Ireland Ltd. All rights reserved.