Microtubule-regulatory phosphoproteins and NER system are involved in platinum and paclitaxel-based chemotherapy resistance in ovarian cancer
5567 Background: The treatment of ovarian cancer is hindered by intrinsic resistance to platinum and paclitaxel-based chemotherapy (CT). Nucleotide excision repair system plays a central role in DNA repair and is related with resistance to platinum compounds. Excision repair cross-complementation 1 (ERCC1) and 3 (ERCC3) genes confer a differential sensitivity to CT. OP18/stathmin and mDIA are involved in regulation of microtubules dynamics and may represent a mechanism of resistance to paclitaxel. Both mechanisms have been recently investigated in ovarian cancer (OC). Methods: Formalin and paraffin-embedded tissues obtained from 33 patients with advanced OC were retrospectively collected to investigate ERCC1, ERCC3, OP18, and mDIA mRNA levels by quantitative RT- PCR. All patients received a median of 6 cycles platinum based CT in combination with taxanes. Median age was 62 years. Tumors were classified: 52% serous, 9% endometrioid, 27% clear cell, and 12% poorly differentiated carcinomas. FIGO stage: 4 (12%) stage II, 19 (58%) stage III, and 10 (30%) stage IV. 12 chemoresistant tumors (time to recurrence (TTR) < 6 months) and 21 chemosensitive tumors (TTR = 6 months) were analyzed. Median follow-up was 31 months. Results: An increase in mRNA levels was consistently observed in the chemoresistent group: 1.9-fold increased in ERCC1 and 1.6-fold increased in ERCC3. Both genes exhibited comparable expression levels. Statistically significant differences on ERCC1 and ERCC3 mRNA levels were encountered when chemoresistant and chemosensitive tumors were compared (p=0.01 and p= 0.03, respectively). Statistically differences on OP18 mRNA levels were found when chemoresistant and chemosensitive tumors were compared (p=0.05). No differences in mDIA mRNA levels were encountered. Conclusions: Our results suggest that determination of ERCC1-ERCC3 before chemotherapy is potentially useful to predict the effectiveness of platinum-based therapy. Microtubule drug resistance in OC may be associated with altered OP18/stathmin expression. Novel treatment approaches based on molecular markers could be useful predictors of response and could identify targets for therapeutic strategies. Further studies are required. No significant financial relationships to disclose.