Coffee is considered to exert preventive effects on malignant tumors; however, the underlying molecular mechanisms are not yet fully elucidated. The immune checkpoint functions as a mechanism of carcinogenesis and its inhibition by an antibody is a promising strategy for the treatment of malignant tumors. In the present study, the association between coffee and the immune checkpoint was analyzed. The present study examined whether extracts of coffee affect the transcriptional regulation of the immune checkpoint factors, programmed death‑1 (PD‑1) and programmed death‑ligand 1 (PD‑L1) and found that the coffee extracts increased the transcriptional activities of these factors in chronic myelogenous leukemia K562 cells. In addition, caffeine, a component of coffee, enhanced the transcriptional activities of PD‑1 and PD‑L1. Reverse transcription‑quantitative qPCR revealed that caffeine induced an increase in the mRNA levels of these factors. Cell cycle analysis revealed that the coffee extracts and caffeine induced the death of K562 cells. On the whole, the findings of the present study provide novel insight into the effects of coffee and caffeine, and provide a novel regulatory mechanisms of the immune checkpoint in malignant tumors.

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