Adhesion molecules and cell surface proteases are integrally involved in cell migration and matrix invasion that occurs in the early phase of wound healing and all stages of tumor progression and metastasis. Among these transmembrane glycoproteins, type II transmembrane serine proteases (TTSPs) [seprase and dipeptidyl peptidase IV (DPP4)], type I transmembrane matrix metalloproteinase (MT1-MMP) and integrins are likely down-regulated in late phases of wound closure but such regulation is lost in tumors. To advance knowledge of the role of integrins and transmembrane proteases in tumor progression and metastasis, three specific aims are sought: (i) to define the integrin function in tumor growth and survival, (ii) to provide evidence for the catalytic activation of seprase and its novel truncated forms and to demonstrate their roles in malignant progression, and (iii) to examine the possibility that increased expression of cell surface proteases is required for successful metastatic colonization. Both spontaneous and experimental metastasis models will be used, that is, immuno-deficient mice will be inoculated with stable cell lines either supporting or suppressing [using RNA interference (RNAi) knockdown] the expression of specific genes. Gene expression profiling and proteomic analysis of membrane proteins of FACS-sorted tumor and host stromal cells in primary tumors and metastases generated from the two models will reveal a set of molecules that are crucial for pathways of cell growth, survival and organ-specific seeding, as well as proteolytic enzyme-dependent tumor growth, invasion and metastatic colonization. Engineered protein expression, RNAi knockdown, and peptide / antibody inhibitors will be used to assess the molecular requirements for pathways related with the metastatic process. Peptide inhibitors and single chain fragment variable (scFv) antibody phage-display libraries derived from cancer patients will be used to identify blockers for tumor progression and metastasis. The long-term goal of this project is to determine the molecular mechanisms underlying extracellular matrix degradation and cell adhesion of both tumor and stromal cells in major steps of the metastatic process.
