Dissecting the Nuclear Function of SCUBE3 Protein in the Presence of Duxorubicin
Signal Peptide CUB-EGF like domain-containing protein 3 (SCUBE3) is a member of a newly identified secreted and membrane-associated SCUBE family. There is considerable evidence demonstrating that SCUBE3 promotes growth, metastasis, and angiogenesis in cancer. The elevation of SCUBE3 protein is associated with poor treatment outcome in cancer patients. We identified SCUBE3 gene as a gene that sensitizes breast cancer cells to doxorubicin treatment using unbiased high throughput loss of functional genomic screen. Silencing of SCUBE3 expression acts as a potent suppressor of cell viability, tumor cells growth, metastasis, invasion, and improves doxorubicin outcome in a pre-clinical mouse model compared to control, in breast cancer cells. Interestingly, we observed a dose-dependent nuclear translocation of SCUBE3 protein in doxorubicin treated-cells compared to control. This result suggests that the nuclear translocation of SCUBE3 is a key event important for mediating cellular response in the presence of doxorubicin treatment. Furthermore, our results demonstrated that SCUBE3 regulates the MAP-Kinase pathway and as well DNA damage repair pathway including RAD51 and FOXM1. Using interaction studies, we demonstrated that SCUBE3 is a ligand of EGFR. These findings highlight the importance of SCUBE3 as a potent therapeutic target for treating and predicting treatment outcomes in breast cancer patients. The goal of this proposal is to define the role of nuclear SCUBE3 in the presence of doxorubicin treatment and identify key genes mediating SCUBE3 function in breast cancer. Determining the role of SCUBE3 in the nucleus will advance our understanding of cellular survival control points and inform the development of novel therapeutic strategies that focuses on SCUBE3. We propose two specific aims to test our hypothesis: In specific aim 1, we will test the hypothesis that nuclear translocation of SCUBE3 promotes survival of breast cancer cells when treated with doxorubicin; and in specific aim 2, we will test the hypothesis that genes underlying the SCUBE3 and FOXM1 pathway regulate DNA damage and metastasis progression. This project will elucidate fundamental aspects of how SCUBE3 mediate cellular response against doxorubicin treatment, promotes tumor cell growth and progression, and how novel inhibition of SCUBE3 translocation to the nucleus, in combination with doxorubicin, can effectively inhibit cancer growth.