Vector-mediated Sirna In Vivo Inhibition Of The Klk6 Gene Expression And Function Of Mouse Breast Cancer Cells

The tissue kallikreins(KLK), a subgroup of serine proteases, contains 15 members.Prostate specific antigen (PSA),human kallikrein 3 (hK3), has long been an effectivebiomarker for prostate cancer. Now, other members of the tissue kallikrein (KLK) gene familyare fast becoming of clinical interest due to their potential as prognostic biomarkers,particularly for hormone dependent cancers. KLK6 encodes a secreted serine protease (hK6)with predicted trypsin-like enzymatic activity. It had been shown KLK6 expression levelchanged in breast cancer, and KLK6 may be involved in carcinogenesis. But the role of KLK6remains unknown. This study aims to find out the function of KLK6 in breast cancer usingsiRNA technique.Objectives: To study the functions of KLK6 gene in breast cancer using siRNA technique.Methods: To observe the silencing effect of KLK6 gene on tumor growth followingintra-tumoral injection of siRNA or siRNA expression plasmid in nude mice with breastcancer.Results: After multiple direction intratumoral injection of siRNA or plasmid, KLK6expression in cancer tissue of nude mice decreased, and growth speed of tumor increased.Ratio of S stage tumor cells increased, and the ratio of apoptosis cells showed adown-tendency.Conclusions: Expression of KLK6 gene was suceessfuly inhibited in breast cancer ofnude mice using RNAi technique. Using real-time quantitative RT-PCR method and immuno-histochemistry, we found the expression of KLK6 mRNA and hK6 protein decreased. Flowcytometry results show that the ratio of S stage cells increased obviously, and breast cancergrew faster, while ratio of apoptosis cells showed no significant change. All these resultssuggest that KLK6 may play a role of suppressor in breast tumorigenesis, which povided a newway of thinking for the cancerous prevention and cure in mammary glands.