DEVELOPING AMYLOID PRECURSOR PROTEIN INHIBITOR DOMAIN (APPI) WITH HIGH AFFINITY AND SPECIFICITY TO THE KALLIKREIN-6 RELATED SERINE PROTEASE FOR CANCER THERAPY

Human tissue kallikreins (hKs) are secreted serine proteases with highly conserved protein sequence and structure, having diverse expression patterns and physiological roles. Numerous Studies have showed that hKs are involved in many cancer-related processes, including cancer cell-growth regulation, angiogenesis, invasion and metastasis.

hK6 has recently been shown as a good marker for certain types of ovarian and uterine cancers. Patients with ovarian carcinoma and uterine serous papillary cancer had significantly higher levels of serum hK6, while above-average expression of hK6 was correlated with poor prognosis. In addition, hK6 was suggested to have a role in cancer migration, invasion and angiogenesis via mechanisms involving degradation of the extracellular matrix proteins. Therefore, inhibitors that can regulate hK6 enzymatic function are of significant pharmaceutical interest.

Several studies have shown that small molecules and peptidic hK6 inhibitors are lacking either specificity or bioavailability, or both. Our laboratory uses protein engineering techniques to develop protein scaffolds as alternatives to small molecules and peptides that will exploit the advantages and address the shortcomings of the two latter groups of therapy. Specifically, our research group is in the midst of establishing the Kunitz domain – namely, Alzheimer`s amyloid β-protein precursor (APPI) – as a new class of protein for tumor-targeting applications. In our unique approach, we generated a yeast displayed library of APPI variants, screened this library against hK6, and selected the APPI variants that have the highest affinity to hK6 using FACS. We will test the ability of these variants to bind soluble hK6 and inhibit this protease in cell culture and murine tumor models. This work will identify novel proteins that target hK6 for clinical application as therapeutic agents.