Mouse anti-Human KLK10 monoclonal antibody, clone 2H9

Human tissue kallikrein 9 (KLK9) is a member of the kallikrein-related family of proteases. Despite its known expression profile, much less is known about the functional roles of this protease and its implications in normal physiology and disease. We present here the first data on the biochemical characterization of KLK9, investigate parameters that affect its enzymatic activity (such as inhibitors) and provide preliminary insights into its putative substrates. We show that mature KLK9 is a glycosylated chymotrypsin-like enzyme with strong preference for tyrosine over phenylalanine at the P1 cleavage position. The enzyme activity is enhanced by Mg2+ and Ca2+, but is reversibly attenuated by Zn2+. KLK9 is inhibited in vitro by many naturally occurring or synthetic protease inhibitors. Using a combination of degradomic and substrate specificity assays, we identified candidate KLK9 substrates in two different epithelial cell lines [the non-tumorigenic human keratinocyte cells (HaCaT) and the tumorigenic tongue squamous carcinoma cells (SCC9)]. Two potential KLK9 substrates [KLK10 and midkine (MDK)] were subjected to further validation. Taken together, our data delineate some functional and biochemical properties of KLK9 for future elucidation of the role of this enzyme in health and disease.

NES1 gene is thought to be a tumor-suppressor gene. Our previous study found that overexpression of NES1 gene in PC3 cell line could slow down the tumor proliferation rate, associated with a mild decrease in BCL-2 expression. The BCL-2 decrease could increase the sensitivity of radiotherapy to tumors. Thus, we supposed to have an "enhanced firepower" effect by combining overexpressed NES1 gene therapy and I-131 radiation therapy uptake by overexpressed hNIS protein. We found a weak endogenous expression of hNIS protein in PC3 cells and demonstrated that the low expression of hNIS protein in PC3 cells might be the reason for the low iodine uptake. By overexpressing hNIS in PC3, the radioactive iodine uptake ability was significantly increased. Results of in vitro and in vivo tumor proliferation experiments and F-18-fluorothymidine (F-18-FLT) micro-positron emission tomography/computed tomography (micro-PET/CT) imaging showed that the combined NES1 gene therapy and I-131 radiation therapy mediated by overexpressed hNIS protein had the best tumor proliferative inhibition effect. Immunohistochemistry showed an obvious decrease of Ki-67 expression and the lowest BCL-2 expression. These data suggest that via inhibition of BCL-2 expression, overexpressed NES1 might enhance the effect of radiation therapy of I-131 uptake in hNIS overexpressed PC3 cells.