CD38 triggers inflammasome-mediated pyroptotic cell death in head and neck squamous cell carcinoma

Pyroptosis is a form of inflammatory cell death. Although it is recognized that NLRP3 (nucleotide-binding domain, leucine-rich repeat-containing family, pyrin domain-containing 3) inflammasome is involved in pyroptosis activation, the mechanism by which head and neck squamous cell carcinoma (HNSCC) inhibits pyroptotic cell death remains undefined. This study aims to delineate the role of calcium regulator CD38 in NLRP3 inflammasome-dependent pyroptosis in HNSCC.

CD38 overexpressing HNSCC cell lines (SAS, CAL27, SNU899) were generated using lentiviral vectors. NLRP3 and gasdermin D (GSDMD) quantity were detected using Western blot. Caspase-1 activity changes were measured using the Caspase-Glo^® 1 inflammasome assay. Cell death proportion was determined by flow cytometry analysis. Proliferation assay was performed using xCELLigence RTCA system. Mouse xenotransplantation was performed to evaluate the potential oncogenic or tumor-suppressive function of CD38. ChIP assay was conducted to verify whether transcription factor NFAT1-mediated NLRP3 expression.

Exogenous calcium treatment can lead to a significant increase in caspase-1 activity in HNSCC. This feature was also observed in HNSCC cells with stable CD38 overexpression. CD38-overexpressing cell lines showed a significant reduction in proliferation. Further, expression of NLRP3 protein level was significantly increased in CD38-overexpressing cell lines. The N-terminal effector domain of GSDMD was remarkably increased in the CD38-overexpressing HNSCC. ChIP assay indicated that calcium-sensitive transcription factor NFAT1 was possibly involved in the transcriptional upregulation of NLRP3 observed in CD38-overexpressing HNSCC. The pre-clinical xenograft model revealed that CD38 expression had an inhibiting function on HNSCC progression.

In conclusion, our results suggested that activation of pyroptosis in HNSCC is a calcium-dependent process. Reduced expression of calcium ion regulator CD38 functions could prevent inflammasome-induced pyroptosis in HNSCC. CD38 may function as a tumor suppressor in HNSCC progression.