Human Pancreatic CTCs Express the ECM Protein SPARC

Circulating Tumor Cells (CTCs) are shed from primary tumors into the bloodstream, mediating the hematogenous spread of cancer to distant organs. To determine the relevance of ECM protein expression to human disease, CTCs were isolated from the blood of metastatic PDAC patients and subjected to single cell RNA-sequencing. Analysis of 7 pancreatic CTCs from 3 patients revealed that the majority expressed keratins defining their epithelial origin. A total of 13 of 60 extracellular protein genes enriched in mouse CTCs (see GEO GSE51372) were expressed at high levels (>100 rpm) in at least one human pancreatic CTC. Human SPARC was the only gene found at high levels in all human pancreatic CTCs. Overall design: To achieve a deep RNA sequencing profile of CTCs at the single cell level, we applied a novel inertial focusing-enhanced device, the CTC-iChip, which allows high efficiency negative depletion of normal blood cells, leaving unattached CTCs in solution where they can be selected and analyzed as single cells (Pubmed ID 23552373). CTCs were then subjected to single cell RNA-sequencing (Pubmed ID 20203668).