Published online Nov 15, 2019. doi: 10.4251/wjgo.v11.i11.971
Peer-review started: March 8, 2019
First decision: April 15, 2019
Revised: July 27, 2019
Accepted: September 12, 2019
Article in press: September 12, 2019
Published online: November 15, 2019
Processing time: 255 Days and 15.3 Hours
Cancer is a major health problem and colorectal cancer, in particular, is a devastating disease with high mortality rates mainly because of metastasis. Hence there is a need to understand the molecular basis of invasion and metastasis of colorectal cancer cells and identify novel biomarkers of this process.
Calponin 3 (CNN3) is an actin-binding protein expressed in smooth muscle and non-smooth muscle cells. It is required for cytoskeletal rearrangement and wound healing. The cancer cells, which undergo the complex process of metastasis, simply trick the body into activating the biological wound healing program to support their invasion. Thus, CNN3 could play a role in cancer cell invasion and metastasis.
The objectives of this study were to find out the expression status of CNN3 in carcinomas and dissect the potential role of CNN3 in carcinogenesis with a focus on its role in colorectal cancer invasion and response to therapy.
We initially examined CNN3 expression in colon and breast cancer cell lines as well as formalin-fixed, paraffin-embedded sections from archived sporadic colorectal carcinomas, by western blot and immunohistochemistry, respectively. The CNN3 gene was silenced by specific siRNA, in metastatic colon cancer cell line and we confirmed the silencing efficiency by western blot. We then analyzed the silenced cells, along with control siRNA-transfected cells, for changes in epithelial and mesenchymal markers, invasion, and response to 5-fluoruracil treatment. We also performed a proteomic analysis using phospho-kinase array-based panel of 45 proteins.
CNN3 showed positive expression in 6/8 breast and 9/11 colon cancer lines and in HeLa. Interestingly, the colorectal adenocarcinoma line SW480 was negative, while the cell line developed from its matching lymph node metastasis (SW620) was positive for CNN3. The CNN3 expression was fairly consistent with the metastatic phenotype in colon cancer cells. We selected SW620 for further functional analyses. The CNN3-silenced SW620 showed a reduction in collagen invasion and loss of mesenchymal markers. CNN3 silencing caused an increase in the SW620 colon cancer cell sensitivity to 5-fluorouracil. Phospho-kinase array-based proteomic analysis revealed some potential pathways of CNN3 action. CNN3 was expressed in 20/57 (35%) colon cancer cases as shown by immunohistochemistry. CNN3 was associated with a decrease in overall survival in colon cancer in silico.
These results show the involvement of CNN3 in metastasis and resistance to chemotherapy in colon cancer and suggest that significant oncogenic pathways are involved in these CNN3 actions.
These data warrant further research into the role of CNN3 in colorectal carcinogenesis. The CNN3 protein interaction can be explored by various biochemical and proteomic methods to identify the mechanism of CNN3 action. The expression of CNN3 in larger series of various carcinomas and the association with response to various therapies can be investigated with the purpose to explore the potential application of CNN3 as a biomarker to predict metastasis and response to therapy.