PPIC and ovarian cancer: By using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to detect CTCs based on their overexpression of the cyclophilin C gene (PPIC), Obermayr et al. showed a significantly higher presence of CTCs in the platinum-resistant patient group than in the platinum-sensitive group, which was also related to poor prognosis in the follow-up of 93 patients with ovarian cancer [40].