Studies have shown that the combination of an HSP90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) with PDT can improve the antitumor effect of PDT, because PDT can induce the expression of various pro-survival and angiogenic signaling pathway proteins, such as Akt, hypoxia-inducible factor 1α (HIF-1α) and vascular endothelial growth factor (VEGF) in tumor tissues, which are HSP90-dependent client protein [101–103]. The gene discussed is HIF1A; the disease is neoplasm.