Published online Sep 14, 2018. doi: 10.3748/wjg.v24.i34.3884
Peer-review started: May 7, 2018
First decision: May 23, 2018
Revised: June 16, 2018
Accepted: June 27, 2018
Article in press: June 27, 2018
Published online: September 14, 2018
To clarify the underlying mechanism of formin-like 3 (FMNL3) in the promotion of colorectal carcinoma (CRC) cell invasion.
The in vitro biological function analyses of FMNL3 were performed by gain- and loss-of function approaches. Changes in the F-actin cytoskeleton were detected by the technologies of phalloidin-TRITC labeling and confocal microscopy. The signaling pathway mediated by FMNL3 was explored by western blot, gelatin zymograph assay, co-immunoprecipitation (co-IP), immunofluorescence co-localization, and glutathione S-transferase (GST) pull-down assay.
The in vitro experimental results showed that FMNL3 significantly promoted the proliferation, invasion, and migration of CRC cells (P < 0.05 and P < 0.01). Moreover, FMNL3 regulated the remodeling of actin-based protrusions such as filopodia and lamellipodia in a RhoC-dependent manner. The western blot and gelatin zymograph assay results indicated that FMNL3 was involved in the RhoC/ focal adhesion kinase (FAK) pathway and acted as an effector of RhoC to activate the downstream signaling of p-FAK as well as p-MAPK and p-AKT. This resulted in the increased expression of matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9) and vascular endothelial growth factor (VEGF), and the subsequent promotion of CRC cell invasion. The results of TAE226, U0126 or Ly294002 treatment confirmed an essential role of FMNL3 in activation of the RhoC/FAK pathway and the subsequent promotion of CRC invasion. Co-IP, co-localization and GST pull-down assays showed the direct interaction of FMNL3 with RhoC in vivo and in vitro.
FMNL3 regulates the RhoC/FAK signaling pathway and RhoC-dependent remodeling of actin-based protrusions to promote CRC invasion.
Core tip: Formin-like 3 (FMNL3) belongs to the subfamily of diaphanous-related formins, which govern the actin-dependent processes, including cell motility and invasion. The increased expression of FMNL3 in colorectal carcinoma (CRC) was shown to contribute to metastasis and poor prognosis of patients in previous studies, however its regulatory mechanism remains unclear. This work reveals that FMNL3 plays a positive role in CRC cell proliferation, invasion and migration. Moreover, FMNL3 activates the RhoC/FAK signaling pathway, and also regulates RhoC-dependent remodeling of actin-based protrusion, such as filopodia and lamellipodia, to promote CRC cell invasion. FMNL3 can be applied as a promising specific biomarker for CRC progression and metastasis.