The role of cancer cell-derived TWEAK in promoting a cancer stem-like phenotype in ovarian cancer cells

Ovarian cancer is the most lethal gynecological cancer in the United States, with over 80% of patients relapsing after chemotherapy. Recurrent ovarian cancer may be due to cancer stem-like cells (CSCs) that are drug resistant and capable of long-term self-renewal and reestablishment of tumors. Previous studies in our lab suggest that TWEAK, a cytokine enriched in ovarian tumors, enhances CSC development and survival. Additionally, inhibiting TWEAK in combination with chemotherapy was shown to significantly prolong survival and remission in mouse models. The source of TWEAK in ovarian cancer remains unidentified, but in normal tissues it is primarily produced by myeloid cells. A recent pancreatic cancer study identified cancer cells as a novel source of TWEAK and preliminary data from our lab suggests that TWEAK protein expression in ovarian cancer cells is significantly increased (2-fold) following chemotherapy treatment. Therefore, we hypothesize that cancer cell-derived TWEAK is a unique driver of CSC phenotypes in ovarian cancer cells. To explore this hypothesis, we generated and validated shRNA knockdown of TWEAK in OVCAR8 and CAOV4 ovarian cancer cell lines at the gene and protein level. To assess TWEAK-mediated tumor formation, we sorted for CSCs and non-CSCs in shNeg and shTWEAK cells and intraperitoneally injected cells into a xenograft mouse model. We found significantly decreased tumor formation in non-CSC shTWEAK tumors compared to non-CSC shNeg tumors (p<0.05). Moreover, the calculated stem cell frequency was significantly reduced in the shTWEAK non-CSCs compared to the shNeg non-CSCs and shTWEAK CSCs (p=0.0144 and p=0.0086, respectively). This data suggests that stem cell frequency is dependent on TWEAK expression. Experiments are underway to assess spheroid formation ability, chemoresistance, and expression of stemness genes in the CSC and non-CSC shNeg and shTWEAK cells. By targeting factors like TWEAK that promote a CSC phenotype, we hope to identify alternative therapeutic strategies to inhibit CSC development and prevent relapse in ovarian cancer.