HIF1A and neoplasm: Lactate accumulation is a hallmark of solid cancers but has been considered a metabolic waste product of glycolytic tumors.[40] However, it is becoming increasingly recognized as an important TME signal that is responsible for regulating the effector functions of a variety of tumor‐infiltrating immune cells.[41] Tumor‐derived lactate was shown to be sufficient to drive macrophage M2 polarization in a HIF‐1α‐dependent manner,[16] although the metabolic mechanism involved has not yet been elucidated.