ANGLE plc announced that the Edith Cowan University, Perth, Australia, has published results from a study in ovarian cancer patients using the Parsortix® system. The primary aim of this study was to demonstrate the ability to evaluate the expression of both epithelial and mesenchymal markers, as well as PD-L1 status, of circulating tumour cells (CTCs) isolated using the Parsortix system, which may help to predict whether patients will respond to immunotherapy drugs. The Parsortix system was selected by researchers for the study due to its ability for unbiased CTC enrichment, enabling the isolation of both epithelial and mesenchymal cancer cells and those in transition (EMTing-CTCs).

This is clinically relevant because, although the transition to a mesenchymal phenotype is associated with increased metastatic potential and worse prognosis, many CTC isolation methods, including the leading antibody-based system, only capture epithelial cells and miss mesenchymal and EMTing cells. Blood from 16 ovarian cancer patients was collected and processed using the Parsortix system. Isolated CTCs were stained with multiple markers to determine their phenotype (epithelial, EMTing or mesenchymal) and their PD-L1 status.

CTCs were identified in 63% of patients and, of these CTCs, 61% were exclusively epithelial, 26% exclusively mesenchymal and 11% were positive for both epithelial and mesenchymal markers (EMTing-CTCs). The remaining 2% expressed the ovarian-specific marker only. Half of the patients with detectable CTCs were PD-L1 positive.

PD-L1 positive CTCs were more common amongst EMTing-CTCs, accounting for 76% of the EMTing-CTCs observed, with a significant association between the two when compared to epithelial and mesenchymal CTCs. This study highlights the potential for this multi-marker staining procedure to be useful in PD-L1 status investigation, evaluating its utility as a biomarker to select patients for inclusion in clinical trials that are likely to respond better to immunotherapy treatments. Currently the proportion of patients that respond to PD-L1 or PD-1 inhibitors is low, at around 13% to 50%, indicating a clear need for improved patient selection as non-responders do not benefit from treatment but risk developing hyper-progressive disease and drug toxicity with immune-related adverse events.