Gravity-based microfiltration reveals unexpected prevalence of circulating tumor cell clusters in ovarian and colorectal cancer

Abstract

Circulating tumor cells (CTCs) are rare (few cells per milliliter of blood) and mostly isolated as single cell CTCs (scCTCs). CTC clusters (cCTCs), even rarer, are of growing interest, notably because of their higher metastatic potential, but very difficult to isolate. Here, we introduce gravity-based microfiltration (G{micro}F) for facile isolation of cCTCs while minimizing unwanted cluster disaggregation, with [~]85% capture efficiency. G{micro}F from orthotopic ovarian cancer mouse models, from 17 epithelial ovarian cancer (EOC) with either localized or metastatic disease, and from 13 metastatic colorectal cancer liver metastasis (CRCLM) patients uncovered cCTCs in every case, with between 2-100+ cells. cCTCs represented between 5-30% of all CTC capture events, and 10-80% of CTCs were clustered; remarkably, in 10 patients, most CTCs were circulating not as scCTCs, but as cCTCs. G{micro}F uncovered the unexpected prevalence and frequency of cCTCs including sometimes very large ones in EOC patients, and motivates additional studies to uncover their properties and role in disease progression.