HDAC4 Promotes Cancer Stemness in Nonsmall Cell Lung Cancer by Upregulating SLC38A2 Expression via HIF-1α to Enhance Glutamine Metabolism.

BACKGROUND AND PURPOSE: The malignant progression of nonsmall cell lung cancer (NSCLC) is closely related to cancer stemness. Histone deacetylase 4 (HDAC4) plays a regulatory role in lung cancer, but its effect on NSCLC stemness remains unclear. This study aimed to investigate the role and mechanism of HDAC4 in NSCLC stemness. METHODS: In this study, a tumor-bearing model was established by subcutaneously injecting A549 cells into the right dorsal side of nude mice. Reverse transcription quantitative polymerase chain reaction (RT-qPCR), Western blotting, and immunohistochemistry were used to measure gene and protein expression levels. Flow cytometry, sphere formation assays, and Transwell experiments were employed to assess cancer cell stemness, migration, and invasion. Additionally, a kit was used to measure changes in glutamine metabolism-related indicators. RESULTS: In this study, we found that knocking down HDAC4 expression inhibited the expression of SRY-box transcription factor 2 (SOX2), octamer-binding transcription factor 4 (OCT4), and nanog homeobox (NANOG) in A549 cells; it also reduced the proportions of CD133- and CD44-positive cells and suppressed their sphere formation, cell migration, and invasion abilities. Furthermore, HDAC4 knockdown inhibited glutamine uptake, glutamate production, α-ketoglutarate levels, and glutaminase (GLS) activity. Notably, treatment with the additional glutamine metabolism inhibitor CB-839 attenuated the promoting effects of HDAC4 overexpression on the stemness, migration, and invasion of A549 cells. In addition, HDAC4 promoted the expression of hypoxia-inducible factor-1 alpha (HIF-1α) and solute carrier family 38 member 2 (SLC38A2); after overexpressing HIF-1α, the inhibitory effect of HDAC4 knockdown on SLC38A2 expression in A549 cells was weakened. CONCLUSION: Our study reveals a critical mechanism by which HDAC4 enhances glutamine metabolism through upregulation of HIF-1α expression to promote SLC38A2 expression, thereby driving NSCLC stemness and progression.