“Stealth dissemination” of macrophage-tumor cell fusions cultured from blood of patients with pancreatic ductal adenocarcinoma

Authors: CLAWSON, GARY - Milton S Hershey Medical Center; MATTERS, GAIL - Milton S Hershey Medical Center; XIN, PING - Milton S Hershey Medical Center; MCGOVERN, CHRISTOPHER - Milton S Hershey Medical Center; WAFULA, ERIC - Pennsylvania State University; DEPAMPHILIS, CLAUDE - Pennsylvania State University; MECKLEY, MORGAN - Milton S Hershey Medical Center; WONG, JOYCE - Milton S Hershey Medical Center; ECKERT, KRISTIN - Milton S Hershey Medical Center; STEWART, LUKE - Fluidigm Corporation; D'JAMOOS, CHRISTOPHER - Fluidigm Corporation; ALTMAN, NAOMI - Pennsylvania State University; KAWSAWA, YUKA - Milton S Hershey Medical Center; DU, ZHEN - Milton S Hershey Medical Center; Honaas, Loren; ABRAHAM, THOMAS - Milton S Hershey Medical Center

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2017
Publication Date: 9/28/2017
Citation: Clawson, G., Matters, G., Xin, P., McGovern, C., Wafula, E., dePamphilis, C., Meckley, M., Wong, J., Eckert, K., Stewart, L., D'Jamoos, C., Altman, N., Kawsawa, Y., Du, Z., Honaas, L.A., Abraham, T. 2017. “Stealth dissemination” of macrophage-tumor cell fusions cultured from blood of patients with pancreatic ductal adenocarcinoma. PLoS ONE. 12(9):e0184451. https://doi.org/10.1371/journal.pone.0184451.
DOI: https://doi.org/10.1371/journal.pone.0184451

Interpretive Summary: Because a few, or even single, cells can cause malfunction in living tissues, the isolation and genetic analysis of single cells can be a critical step to understanding disease and disorder etiology. This is especially challenging in multi-cellular eukaryotes (animals, plants, and fungi) because scientifically interesting cell types can be rare, and often located within complex tissues and organs. Even after cells are successfully separated (in this report by a new cell-sorting machine) the genetic analysis of these samples is challenging. Among the reasons are weak signals from very tiny samples that are noisy and hard to handle - yet in this case the power to analyze the activity of all genes in a single cell afforded an unprecedented view into disease etiology. The methods related to gene activity measurements in this report are broadly applicable to the study of any isolated eukaryotic cells (including plants and fungi). As technologies for isolating interesting cells from complex tissues (like laser micro-dissection) are combined with increasingly sensitive gene activity measurements, novel data analysis methods like those reported here must be explored.

Technical Abstract: Circulating tumor cells (CTCs) appear to be involved in early dissemination of many cancers, although which characteristics are important in metastatic spread are not clear. Here we describe isolation and characterization of macrophage-tumor cell fusions (MTFs) from the blood of pancreatic ductal adenocarcinoma (PDAC) patients. The MTFs were generally aneuploid. Immunophenotypic characterizations showed that the MTFs express markers characteristic of PDAC and pancreatic stem cells, as well as markers of M2-polarized macrophages. Single cell RNASeq analyses showed that the MTFs also express many transcripts implicated in cancer progression, LINE1 retrotransposons, and very high levels of several long non-coding transcripts involved in control of metastasis (such as MALAT1). When cultured MTFs were transplanted orthotopically into pancreas of mice, they grew as obvious well-differentiated islands of cells in the pancreas, but in addition they disseminated widely throughout multiple tissues in “stealth” fashion. They were found distributed throughout multiple different organs at 4, 8, or 12 weeks after transplantation (including liver, spleen, lung), occurring as single cells or small groups of cells, without formation of obvious tumors or any apparent progression over the 4-12 week period. We suggest that MTFs may play a critical role in metastatic progression of PDAC: They may disseminate widely from primary tumors early in development of PDACs, and prepare pre-metastatic “niches” for subsequent development of metastatic foci, although they themselves do not appear to form tumors.