Analysis of intrapatient heterogeneity of circulating tumor cells at the single-cell level in the cerebrospinal fluid of a patient with metastatic gastric cancer.

Background: The aims of this study were to detect circulating tumor cells (CTCs) at the single-cell level in cerebrospinal fluid (CSF) and to identify intrapatient heterogeneity of CTCs in a patient with gastric cancer (GC) with leptomeningeal metastasis (LM) using Di-Electro-Phoretic Array technology.

Materials And Methods: The CSF samples were drawn from a patient who was diagnosed with GC with LM. The CSF samples were centrifuged and stained with antibody cocktail to recognize 4',6-diamidino-2-phenylindole, cytokeratin, and epithelial cell adhesion molecule (EpCAM). Gene sequencing was also conducted to evaluate the status of the gene alteration profile of CSFCTCs as compared with those of the CSF non-CTCs and the primary tumor tissue.

Results: Among total 38 cells from the samples, 25 cells represented CK+ (EpCAM+), which boiled down to 0.53 CTCs in 1 mL of CSF. Each CTC was heterogeneous in terms of morphology and degree of marker expression. Some CTCs have a spindle-like shape, whereas others have a round shape. Based on molecular profiling between the 25 CK+ (EpCAM+) CTCs and 13 CK-/EpCAM- cells (i.e., the non-CTCs), CSFCTCs harbored mutations such as MDM2, TP53, KRAS, STK11, and ALK, whereas mutation of these genes was not observed in the CSF non-CTCs. Four genes of nine mutational genes totally observed in the CSFCTCs were also noted in the primary tumor tissue.

Conclusions: We enriched CTCs through a single-cell sorting process in CSF samples of a GC patient with LM. We also demonstrated the intrapatient heterogeneity of the CTCs at the single-cell level.