Role of LLT1 and PCNA as Natural Killer Cell Immune Evasion Strategies of HCT 116 Cells

Background/Aim: Cancer stem cells (CSCs) are a subpopulation of cells that retain self-renewal and pluripotency capabilities, are resistant to chemotherapy, and are thought to facilitate metastasis. Target cell expression of proliferating cell nuclear antigen (PCNA) or lectin-like transcript 1 (LLT1) inhibits natural killer (NK) cell functions. The purpose of this study was to characterize the expression of LLT1 or PCNA as NK cell evasion strategies of HCT 116, a colorectal cancer cell line. Materials and Methods: Protein expression was determined by flow cytometry and/or confocal microscopy. Stem-like cells were sorted and characterized, and NK cell effector functions measured by interferon-γ secretion and cytotoxicity assay. Results: PCNA expressing cells are potential CSCs, blocking PCNA alters interferon-γ secretion, and blocking PCNA or LLT1 increases cytotoxicity. Conclusion: PCNA is a potential biomarker of stem-like colon cancer cells. Based on the results of this study, PCNA and LLT1 should be further explored as in vivo immunotherapeutic targets for NK cell-mediated killing.