Relevance of Circulating Hybrid Cells as a Non-Invasive Biomarker for Myriad Solid Tumors

Abstract

Metastatic progression defines the final stages of tumor evolution and underlies the majority of cancer-related deaths. The heterogeneity in disseminated tumor cell populations capable of seeding and growing in distant organ sites contributes to the development of treatment resistant disease. We recently reported the identification of a novel tumor-derived cell population, circulating hybrid cells (CHCs), harboring attributes from both macrophages and neoplastic cells, including functional characteristics important to metastatic spread. These disseminated hybrids outnumber conventionally defined circulating tumor cells (CTCs) in cancer patients. It is unknown if CHCs represent a generalized cancer mechanism for cell dissemination, or if this population is relevant to the metastatic cascade. Herein, we detect CHCs in the peripheral blood of patients with cancer in myriad disease sites encompassing epithelial and non-epithelial malignancies. Further, we demonstrate that in vivo-derived hybrid cells harbor tumor-initiating capacity in murine cancer models and that CHCs from human breast cancer patients express stem cell antigens, features consistent with the ability to seed and grow at metastatic sites. Finally, we reveal heterogeneity of CHC phenotypes reflect key tumor features, including oncogenic mutations and functional protein expression. Importantly, this novel population of disseminated neoplastic cells opens a new area in cancer biology and renewed opportunity for battling metastatic disease.

Label-free enrichment of rare unconventional circulating neoplastic cells using a microfluidic dielectrophoretic sorting device

“…According to current literature there are approximately 30 CHCs per 500,000 PBMCs in PDAC patients representing only 0.006% of total cells in blood [14]. This overall rarity highlights a clear need for CHC enrichment for downstream analyses such as mutational pro ling using ddPCR or genomic surveying using single cell sequencing, both of which have a limit of detection (LOD) of 0.1% [45]- [48].…”

“…The majority of PDAC tumors harbor KRAS mutations and its presence in circulation, from circulating cells or cell free DNA, is clinically relevant for cancer detection [49]. Moreover, our group has previously found that a subpopulation of FACS isolated CHCs have KRAS mutation as detected by ddPCR [14]. To con rm the presence of CHCs in peripheral blood specimen prior to subjection to DEP, PBMCs were isolated from whole blood and analyzed as we have previously reported [13], [14].…”

“…Moreover, our group has previously found that a subpopulation of FACS isolated CHCs have KRAS mutation as detected by ddPCR [14]. To con rm the presence of CHCs in peripheral blood specimen prior to subjection to DEP, PBMCs were isolated from whole blood and analyzed as we have previously reported [13], [14]. Brie y, PBMCs were adhered to glass slides then stained with antibodies against CD45 and CK, and visualized by uorescence microscopy (Fig.…”

“…In the past 5 years, other promising types of unconventional circulating neoplastic cells have been described such as tumor hybrid cells (THC) and circulating hybrid cells (CHCs) [12], [13]. CHCs are described as having hybrid phenotypes of a neoplastic cell and a leukocyte with dual expression of CD45 and tumor markers such as EpCAM or CK [10], [13], [14]. In PDAC patients, CHCs have shown better prognostic value than CTCs as their enumeration correlated with stage and survival [15].…”