Induction of circulating ABCB1 transcripts under platinum-based chemotherapy indicates poor prognosis and a bone micrometastatic phenotype in ovarian cancer patients

The drug efflux transporter P-glycoprotein, encoded by the ABCB1 gene, promotes acquired chemoresistance. We explored the presence and clinical relevance of circulating cell-free ABCB1 transcripts (cfABCB1^(tx)) in ovarian cancer patients (173 longitudinal serum samples from 79 cancer patients) using digital droplet PCR. cfABCB1^(tx) were readily detectable at primary diagnosis (median 354 mRNA copies/20 µl serum), paralleled FIGO-stage and predicted surgical outcome (p = 0.023, …