HIF1A and neoplasm: Additionally, glutamine is competitively uptaken by tumor cells from the TME, depriving CD8+ T cells of metabolic substrates and impairing their proliferation and cytokine secretion, concurrently, glutamine depletion activates HIF-1α signaling, prompting macrophages to secrete IL-23, which stimulates regulatory T-cell proliferation and suppresses antitumor immunity (9).