Abstract 1450: The persistence of ERCC1-positive circulating tumor cells predicts worse prognosis in patients with primary ovarian cancer.
Authors: Kuhlmann Jan Dominik , Wimberger Pauline , Aktas Bahriye , Kimmig Rainer , Kasimir-Bauer Sabine 
Published: August 2014

Abstract
Background: Resistance to platinum based chemotherapy occurs in about 15% of primary ovarian cancer patients and can only be assessed retrospectively during post-chemotherapy follow-up. We recently demonstrated the prognostic significance of circulating tumor cells (CTC) as a blood-based biomarker in primary ovarian cancer patients before surgery and after chemotherapy. We now analyzed whether negative prognostic impact of CTC arose from a cellular phenotype being associated with platinum resistance and studied the expression of excision repair cross-complementing rodent repair deficiency, complementation group 1 (ERCC1) nuclease in CTC. Data were correlated with progression free survival (PFS) and overall survival (OS).
Methods: 10 ml blood were studied for CTC before surgery (n= 107) and after chemotherapy with carboplatin and paclitaxel (n=60) using the AdnaTest OvarianCancer (AdnaGen AG). Immunomagnetic enrichment targeting the epithelial epitopes EpCAM and MUC-1 was followed by mRNA isolation using oligo-dT magnetic beads and subsequent gene expression analysis by reverse transcription and multiplex RT-PCR for EpCAM, MUC-1 and Ca 12-5 transcripts. A patient was considered CTC-positive (+), if at least one of the above mentioned markers was detectable. ß-actin served as an internal control. All recovered cDNA samples were separately assessed for ERCC1 expression by single-plex RT-PCR. PCR-products were quantified on the Agilent Bioanalyzer 2100.
Results: CTC were detected in 16/106 patients (15%) before surgery and in 10/43 patients (23%) after chemotherapy. Applying an amplicon cut-off value of &gt; 0,2 ng/μl for ERCC1 transcripts, none of the 21 investigated healthy donor samples were positive. The overall ERCC1-positivity rate was 36% before surgery and 35% after chemotherapy, respectively. In the CTC (+) group before surgery, 67% were positive for ERCC1, whereas in the CTC (-) group, 30% expressed ERCC1. After chemotherapy, the percentages were 38% and 29%, respectively. ERCC1-positivity was found in 5/14 platinum-resistant (36%) and 34/93 platinum sensitive patients (37%). CTC-positivity before surgery significantly associated with reduced OS (p = 0,0086) and after chemotherapy with reduced PFS (p = 0,011) and OS (p = 0,0016). No association between clinically defined platinum resistance and ERCC1-positivity was observed. Likewise, ERCC1-positivity before surgery or after chemotherapy alone did not provide prognostic significance. However, ERCC1 persistant CTC significantly correlated with decreased PFS (p = 0,0216) and OS (p = 0,0392).
Conclusion: Implementing ERCC1 expression in CTC analysis of ovarian cancer patients may identify a subgroup of ovarian cancer patients with worse prognosis. Furthermore, ERCC1 might serve as a valuable biomarker for monitoring the disease to possibly change treatment in case of ERCC1 persistant CTC.
Citation Format: Jan Dominik Kuhlmann, Pauline Wimberger, Bahriye Aktas, Rainer Kimmig, Sabine Kasimir-Bauer. The persistence of ERCC1-positive circulating tumor cells predicts worse prognosis in patients with primary ovarian cancer. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1450. doi:10.1158/1538-7445.AM2013-1450