Dysregulated KRAS gene-signaling axis and abnormal chromatin remodeling drive therapeutic resistance in heterogeneous-sized circulating tumor cells in gastric cancer patients

The mechanism by which heterogeneous-sized circulating tumor cells (CTCs) in gastric cancer (GC) patients are resistant to the targeted therapy and/or chemotherapy remains unclear. This study investigated prognostic value and genomic variations of size-heterogenous CTCs, in an attempt to unravel the molecular mechanisms underlying the therapeutic resistance, which is relevant to poor prognosis in GC. Aneuploid CTCs, detected in 111 advanced GC patients, were categorized into small (≤white blood cell [WBC], 25.54%) and large (>WBC, 74.46%) cells. Pre-treatment patients possessing ≥3 baseline small CTCs with trisomy 8 (SCTCstri) or ≥6 large multiploid CTCs (LCTCsmulti) showed an inferior median progression-free survival. Moreover, the cut-off value of ≥6 LCTCsmulti was also an effective prognosticator for poor median overall survival. Single cell-based DNA sequencing of 50 targeted CTCs indicated that SCTCstri and LCTCsmulti harbored distinct gene variations respectively. Mutations in the KRAS and Rap1 pathway were remarkably abundant in SCTCstri, whereas several unique mutations in the MET/PI3K/AKT pathway and SMARCB1 gene were identified in LCTCsmulti. Obtained results suggested that SCTCstri and LCTCsmulti exhibited different mechanisms to therapy resistance and correlated with patients' poor outcome.