Formin-like 3 regulates RhoC/FAK pathway and actin assembly to promote cell invasion in colorectal carcinoma.

AIM: To clarify the underlying mechanism of formin-like 3 (FMNL3) in the promotion of colorectal carcinoma (CRC) cell invasion. METHODS: 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. RESULTS: 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. CONCLUSION: FMNL3 regulates the RhoC/FAK signaling pathway and RhoC-dependent remodeling of actin-based protrusions to promote CRC invasion.

Increased expression of formin-like 3 contributes to metastasis and poor prognosis in colorectal carcinoma.

Formin-like 3 (FMNL3), a member of diaphanous-related formins subfamily, plays an important role in cytoskeleton reorganization, cell adhesion and cancer cell invasion in vitro. This study aimed to explore the expression of FMNL3 in colorectal carcinoma (CRC) cell-lines and tissues, and further evaluate its prognostic value and correlation with the clinicopathological parameters, and also investigate the effects of FMNL3 gene silencing on the growth and metastasis of CRC in vivo. Immunohistochemical analysis showed that FMNL3 protein was distributed in a punctuate aggregation pattern and located mainly in the cytoplasm of glandular cavity side, close to the nucleus of CRC cells. The positive rate of FMNL3 expression was 87.5% (84/96) in CRC, which was significantly higher than that in adjacent normal mucosa (30%, 9/30). Moreover, FMNL3 protein expressed far more in primary CRC with metastasis and corresponding lymph nodes metastatic CRC than in primary CRC without metastasis. Increased expression of FMNL3 was closely correlated with tumor size, differentiation, serosal invasion, and both lymph node metastasis and distant metastasis. However, it was not correlated with patients' age and gender. According to Kaplan-Meier survival analyses, patients with FMNL3 high expression level had lower overall survival rate than that with FMNL3 low expression level. Univariate and multivariate analyses revealed that high FMNL3 expression was a significant and independent prognostic predictor of patients with CRC. In addition, FMNL3 mRNA and protein levels were substantially up-regulated in CRC-metastasis-derived cell lines, as compared to those in primary-CRC-derived ones. FMNL3 gene silencing suppressed the growth and metastasis of CRC in vivo. In conclusion, FMNL3 plays an important role in the progression and metastasis of CRC and may be a novel potential prognostic predictor and therapeutic target for patients with CRC.

[Effect of Endostatin and SU6668 combined with 5-FU on human colon cancer xenograft in nude mice].

OBJECTIVE: To investigate the effect of Endostatin and SU6668 combined with 5-FU on the growth and metastasis of human colon cancer in vivo and its mechanism. METHODS: Metastatic model of human colon cancer was established by orthotopic implantation of human tumor tissue into colon wall of nude mice. Twelve days later, mice were randomly divided into saline water control, Endostatin, SU6668, Endostatin plus SU6668, and Endostatin plus SU6668 and 5-FU groups, intraperitoneal injected respectively every day for four weeks. Six weeks after implication, the tumor weight, inhibition rates, intratumoral microvessel density (MVD) and metastasis were evaluated after the mice were sacrificed. RESULTS: Compared with the control, tumor growth was significantly inhibited in mice treated respectively with Endostatin, SU6668, Endostatin plus SU6668 and Endostatin plus SU6668 and 5-FU with an inhibition rate of 0, 64.9%, 63.5%, 76.4% and 88.2% respectively,and MVD decreased significantly in treated groups [(18.10+/-5.65) vs (2.75+/-0.75), (3.17+/-0.58), (0.94+/-0.42) and (0.36+/-0.45)]. The incidences of peritoneal and region lymph node metastases were significantly inhibited in Endostatin, SU6668, Endostatin plus SU6668 and Endostatin plus SU6668 and 5-FU (90% vs 16.7%, 25%, 0 and 0; 90% vs 0, 0, 0 and 0). The growth and metastasis of human colon cancer implanted in nude mice were significantly inhibited in Endostatin, SU6668, Endostatin plus SU6668, and Endostatin plus SU6668 and 5-FU, and the effect of Endostatin plus SU6668 and 5-FU was the most obviously. CONCLUSION: Endostatin plus SU6668 and 5-FU has strong inhibitory effect both on tumor growth and metastasis of human colon cancer.