Abstract
Simple SummaryCancer metastasis is responsible for most cancer-associated death. During metastasis, cells that escape the primary tumor into the circulatory system are known as circulating tumor cells. Previous attempts at growing circulating tumor cells in the lab have been hindered by low success rates. Using the novel system first reported here, we demonstrate a 100% (12/12 samples) success rate in culturing circulating tumor cells from metastatic breast cancer patients. Once propagated, we characterized the expression profiles of our cultures, verifying their origins as breast cancer cells. Furthermore, exploratory analysis identifies several key pathways and genes previously known to be associated with breast cancer progression and metastasis. Finally, we demonstrate that cultures grown in the presence of CD45+ cells exhibited higher growth potential ex vivo. Based on this system, we suggest that a reconsideration of the parameters for circulating tumor cell isolation should be undertaken.Circulating tumor cells (CTCs) represent a unique population of cells that can be used to investigate the mechanistic underpinnings of metastasis. Unfortunately, current technologies designed for the isolation and capture of CTCs are inefficient. Existing literature for in vitro CTC cultures report low (6−20%) success rates. Here, we describe a new method for the isolation and culture of CTCs. Once optimized, we employed the method on 12 individual metastatic breast cancer patients and successfully established CTC cultures from all 12 samples. We demonstrate that cells propagated were of breast and epithelial origin. RNA-sequencing and pathway analysis demonstrated that CTC cultures were distinct from cells obtained from healthy donors. Finally, we observed that CTC cultures that were associated with CD45+ leukocytes demonstrated higher viability. The presence of CD45+ leukocytes significantly enhanced culture survival and suggests a re-evaluation of the methods for CTC isolation and propagation. Routine access to CTCs is a valuable resource for identifying genetic and molecular markers of metastasis, personalizing the treatment of metastatic cancer patients and developing new therapeutics to selectively target metastatic cells.
Highlights
Cancer metastasis is estimated to cause ~90% of cancer-associated deaths [1]; the mechanistic underpinnings of metastasis remain elusive
Cells from metastatic breast cancer (MBC) patients and healthy donors (HD) were cultured under identical conditions; all 12
Circulating tumor cells (CTCs) represent a unique population of cells that would enable the further study of cancer metastasis
Summary
Cancer metastasis is estimated to cause ~90% of cancer-associated deaths [1]; the mechanistic underpinnings of metastasis remain elusive. Single-cell mutational analyses have identified novel mutations in CTCs compared to primary tumor tissue [3,4]. These studies indicate that CTCs, if properly isolated and characterized, can be used to elucidate the genetic and molecular markers of disease progression and of metastasis. The immense potential of using CTCs in advancing the understanding of metastasis and developing novel clinical interventions has been limited by the rarity of these cells as < 20 CTCs are obtainable from 10 mL of blood. To obtain sufficient numbers of CTCs for meaningful basic science and translational studies, it is necessary to isolate this ultra-rare cellular subpopulation and to expand the CTCs in culture. Technologies to identify and propagate CTCs in culture remain inefficient [5,6,7,8]
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