Circulating Tumour Cells (CTCs) derived from solid tumours are requisite to metastatic tumour spread. Isolating CTCs and understanding their biology is essential for developing clinical applications for CTCs, such as diagnostic tests and therapeutic targeting. Currently, CellSearch is the only method of CTC enrichment approved by the U.S. Food and Drug Administration, which isolates only epithelial CTCs (CTCs expressing EpCAM) and is resource intensive.This has led to an interest in developing simpler size-based methods for CTC enrichment. MetaCell is a size-based method which has been previously used for enriching and culturing CTCs from various cancer types.
We benchmarked the MetaCell method by spiking healthy blood with different cell numbers (10, 100, 500 and 10,000 cells) of HCT116 and DLD1 colorectal cancer (CRC) cell lines and determined recovery and white blood cell (WBC) depletion rates using CTC (EpCAM and cytokeratins) and WBC (CD45 and CD16) markers via gene expression analysis and immunostaining techniques. Recovery rates were not affected by cell numbers and found be >85% for both CRC cell lines. The MetaCell method also yielded a CTC fraction of high purity with >95% depletion in WBC population.
We then applied the MetaCell method to analyse blood samples from 22 CRC patients. We detected CTCs in 45.5% of patients across all stages of CRC (AJCC Stage I-IV). We plan on generating methylomes and transcriptomes to better our understanding of the metastatic process which could further facilitate exploring the role of these markers in determining prognosis, risk of relapse and response to therapy in patients in the future.