Potential role of nuclear PD-L1 expression in cell-surface vimentin positive circulating tumor cells as a prognostic marker in cancer patients

Although circulating tumor cells (CTCs) have potential as diagnostic biomarkers for cancer, determining their prognostic role in cancer patients undergoing treatment is a challenge. We evaluated the prognostic value of programmed death-ligand 1 (PD-L1) expression in CTCs in colorectal and prostate cancer patients undergoing treatment. Peripheral blood samples were collected from 62 metastatic colorectal cancer patients and 30 metastatic prostate cancer patients. CTCs were isolated from the samples using magnetic separation with the cell-surface vimentin(CSV)-specific 84-1 monoclonal antibody that detects epithelial-mesenchymal transitioned (EMT) CTCs. CTCs were enumerated and analyzed for PD-L1 expression using confocal microscopy. PD-L1 expression was detectable in CTCs and was localized in the membrane and/or cytoplasm and nucleus. CTC detection alone was not associated with poor progression-free or overall survival in colorectal cancer or prostate cancer patients, but nuclear PD-L1 (nPD-L1) expression in these patients was significantly associated with short survival durations. These results demonstrated that nPD-L1 has potential as a clinically relevant prognostic biomarker for colorectal and prostate cancer. Our data thus suggested that use of CTC-based models of cancer for risk assessment can improve the standard cancer staging criteria and supported the incorporation of nPD-L1 expression detection in CTCs detection in such models.

Scientific reports. 2016 Jul 01*** epublish ***

Arun Satelli, Izhar Singh Batth, Zachary Brownlee, Christina Rojas, Qing H Meng, Scott Kopetz, Shulin Li

Department of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Department of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Department of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Department of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Department of Laboratory Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Departments of Surgical Oncology and Molecular and Cellular Oncology, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA., Department of Pediatrics, The University of Texas MD Anderson Cancer Center, Houston, Texas, USA.