Abstract 2009: Role of kallikrein 6 secretion in metastatic colon cancer
Authors: Skovan Bethany A. , Pandey Ritu , Nagle Raymond B. , Cui Haiyan , Buckmeier Julie A. , Krouse Robert S. , Thompson Patricia A. , Ignatenko Natalia A. 
Published: May 2015

Growing evidence indicates that serine proteases kallikreins are associated with malignancy and may have potential diagnostic/prognostic applications in cancer. Kallikrein 6 (KLK6) is a member of the family of 15 highly conserved secreted trypsin- or chemotrypsin-like serine proteases. Overexpression of KLK6 has been observed in different pathophysiological states such as neurodegenerative diseases, inflammation and cancer.

Activating K-RAS mutations are common in colon cancer progression and contribute to many cancerous phenotypes including increased proliferation, evasion of apoptosis, and increased migration and invasion. We have shown that acquisition of K-RAS mutations in colon cancer cells leads to overexpression of membrane protein caveolin 1 and results in increase of KLK6 expression and secretion. The aim of this study was to elucidate the role of KLK6 expression in metastatic CRC in relation to the status of K-RAS oncogene. Analysis of KLK6 expression in CRC patients by immunohistochemistry shows the statistically significant increase in the staining score for KLK6 protein in the microscopically normal tissue 10 cm away from tumors, which carry mutant K-RAS (G12A mutation) (p=0.05 for crypts staining and p=0.0445 for the surface area). These data suggest a specific role of KLK6 in the invasive phenotype associated with the presence of K-RAS mutation.

To investigate the significance of KLK6 expression in metastatic CRC, we developed HCT116 human colon cancer isogenic cell lines (K-RAS G13D mutation) with the genetic knock down of KLK6 expression (shKLK6 clones). The shKLK6 clones had decreased expression and secretion of KLK6 protein with the minimal effect on the cell growth and viability in cell culture. SCID mice injected with shKLK6 cells exhibited a statistically significant increase in the survival rates (p=0.005), decrease in the incidence of distant metastases and the shift in the location of the metastatic foci closer to the cells injection site. Levels of KLK6 protein secreted into the bloodstream were significantly lower in animals injected with shKLK6 clone compared to HCT116 control clone (p&lt;0.04). A comprehensive array-based profiling and paired analysis of mRNA and miRNA expression in HCT116 control and KLK6 knockout cells revealed a group of specific miRNAs- mRNA target interactions involved in KLK6-mediated metastasis formation during CRC.

The data reported here underscore the significance of KLK6 overexpression for distant metastasis formation in CRC and present the opportunity for therapeutic interventions.

Citation Format: Bethany A. Skovan, Ritu Pandey, Raymond B. Nagle, Haiyan Cui, Julie A. Buckmeier, Robert S. Krouse, Patricia A. Thompson, Natalia A. Ignatenko. Role of kallikrein 6 secretion in metastatic colon cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2009. doi:10.1158/1538-7445.AM2014-2009