Ovarian cancer is the leading cause of cancer death among gynecological malignancies, and it ranks as the fifth most frequent cause of cancer death in women. Elevated expression of Rab25 has been associated with ovarian cancer pathogenesis. Rab proteins are Ras-like small GTPases that are activated and deactivated dependent on their GTP- and GDP-bound form. The conversion between the two forms is orchestrated by various factors, including GDF (GDI displacement factor). Identification of the Rab25 associated GDF could provide a target for inhibition of growth of human epithelial ovarian cancer cells.
So I propose an experiment to examine all protein-protein interactions that involves Rab25 in order to identify the Rab25 associated GDF. Other Rab associated GDF have already been identified, and their sequence will be used in order to look for sequence homolgy in our protein-protein interaction hits (yeast two-hybrid screen). Candidate Rab25 associated GDF will be tested for function in a nucleotide exchange assay, to confirm that they actually function as a GDF and enable the release of GDP-bound Rab25 so that it is in its free form where it is able to convert to active GTP-bound Rab25.
The next step will then be to target this Rab25 associated GDF through RNAi in order to knock it down. One can study the effect this will have on inhibiting tumor growth in human epithelial ovarian cancer cells by applying it on ovarian cancer cell lines.
Hopefully this will lead to an inhibition of tumor growth, and one will have managed to identify a novel form of approach to ovarian cancer therapy that might improve patient management.
Stenmark, H. (2009) Rab GTPases as coordinators of vesicle traffic. Nature Reviews, Molecular Cell Biology, 10; 513-523.
Cheng, K.W., Lahad, J.P., Kuo, W., Lapuk, A., Yamada, K., Auersperg, N., Liu, J., Smith-McCune, K., Lu, K.H., Fishman, D., Gray, J.W., and Mills, G.B. (2004) The RAB25 small GTPase determines aggressiveness of ovarian and breast cancers, Nature Medicine, 10,11; 1251-1256.
Dirac-Svejstrup, A.B., Sumizawa, T., and Pfeffer, S.R. (1997) Identification of a GDI displacement factor that releases endosomal Rab GTPases from Rab-GDI. The EMBO Journal, 16, 3; 465-472.
