Capping Actin Protein Overexpression in Human Colorectal Carcinoma and Its Contributed Tumor Migration

Abstract

Objective: Human colorectal cancer (CRC) is the third most common cancer; patients with metastatic colorectal cancer (mCRC) show poor prognosis than those with CRC cases. There are no reliable molecular biomarkers for the diagnosis of CRC prognosis except with pathological features. Therefore, it is urgent to develop a biomarker for diagnosis and/or prediction of human CRC. In addition, capping actin protein (CapG) belongs to the gelsolin family and has been reported to contribute on tumor invasion/metastasis in multiple human cancers. Here, we are the first to evaluate the expression of CapG in human CRCs.

Study design: To investigate the expression levels of CapG in human tissue array by immunohistochemistry (IHC) staining. Moreover, the mRNA and protein levels were also confirmed in four CRC cell lines and determined using real-time RT-PCR and Western blotting. Finally, a Matrigel transwell invasion assay was used to evaluate the invasion ability in CapG high or low expression cells.

Results: We demonstrated that CapG could be determined in the normal colon tissue and human CRC specimens. However, CapG was significantly overexpressed in the mCRC specimens compared with that in CRC specimens and normal cases. It was also detectable in the four CRC cell lines including mRNA and protein levels. We also found that knockdown of the expression of CapG reduced tumor migration.

Conclusions: In this study, we suggested that CapG could be used as a biomarker for metastatic CRC in the clinical specimens. Moreover, our in vitro study demonstrated that CapG might contribute on tumor metastasis in human CRCs.

Figure 1

CapG expresses in the human colorectal carcinoma and normal specimens in tissue microarray. A tissue microarray was used to examine the expression of CapG by immunohistochemistry; the expression index of CapG in the human colon tissues was quantified by a pathologist, and scores of the specimens were also organized depending on the pathologic diagnosis with normal, colorectal carcinoma, and metastatic colorectal carcinoma. ^∗ p < 0.05.

Figure 2

The mRNA and protein expression levels of CapG in four human colorectal carcinoma cell lines. Four human CRC cell lines including HT29, DLD-1, HCT116, and SW1116 were used to analyze the expressions of (a) mRNA and (b) protein of CapG. GAPDH was used as a loading control.

Figure 3

The ability of cellular migration was determined in HT29 cells. (a) A control shRNA and a CapG shRNA were transfected separately into HT29 cells, and the protein expression of CapG was determined by Western blotting. (b) A transwell migration assay was used to evaluate tumor migration ability in cells after 24 h chemoattractant with FBS. Invaded cells in the bottom chamber were stained with 2% crystal violet solution, and (c) the numbers were counted. ^∗∗∗ p < 0.001.