CHFR and Paclitaxel Sensitivity of Ovarian Cancer

SIMPLE SUMMARY: Studies in tissue culture cell lines have indicated that silencing of the mitotic regulator CHFR is associated with increased paclitaxel sensitivity. More recently, it has been suggested that a UBC13-DNMT1-CHFR pathway also modulates sensitivity of ovarian cancer to paclitaxel in the clinic. Here we have credentialed an anti-CHFR monoclonal antibody for immunohistochemistry and directly examined the association of CHFR expression with outcome of paclitaxel-containing ovarian cancer therapy. While CHFR levels were higher in high grade, high stage ovarian cancer, after correction for stage and debulking status there was no association between CHFR levels and progression-free survival in high grade serous ovarian cancer treated with surgery followed by platinum/taxane therapy. Moreover, there was no association between CHFR expression and response of patient-derived ovarian cancer xenografts treated with paclitaxel monotherapy. These studies indicate that CHFR varies among ovarian cancers but is unlikely to be an independent biomarker for poor response to taxanes. ABSTRACT: The poly(ADP-ribose) binding protein CHFR regulates cellular responses to mitotic stress. The deubiquitinase UBC13, which regulates CHFR levels, has been associated with better overall survival in paclitaxel-treated ovarian cancer. Despite the extensive use of taxanes in the treatment of ovarian cancer, little is known about expression of CHFR itself in this disease. In the present study, tissue microarrays containing ovarian carcinoma samples from 417 women who underwent initial surgical debulking were stained with anti-CHFR antibody and scored in a blinded fashion. CHFR levels, expressed as a modified H-score, were examined for association with histology, grade, time to progression (TTP) and overall survival (OS). In addition, patient-derived xenografts from 69 ovarian carcinoma patients were examined for CHFR expression and sensitivity to paclitaxel monotherapy. In clinical ovarian cancer specimens, CHFR expression was positively associated with serous histology (p = 0.0048), higher grade (p = 0.000014) and higher stage (p = 0.016). After correction for stage and debulking, there was no significant association between CHFR staining and overall survival (p = 0.62) or time to progression (p = 0.91) in patients with high grade serous cancers treated with platinum/taxane chemotherapy (N = 249). Likewise, no association between CHFR expression and paclitaxel sensitivity was observed in ovarian cancer PDXs treated with paclitaxel monotherapy. Accordingly, differences in CHFR expression are unlikely to play a major role in paclitaxel sensitivity of high grade serous ovarian cancer.