ABCG2 and lip and oral cavity carcinoma: As gefitinib, EGCG, and curcumin inhibited ABCG2 expression, although to varying degrees, reducing intracellular PpIX accumulation and increasing oral cancer cell viability, these results suggest that there might be a possible benefit of treating early-stage oral cancer patients with PDT in combination with EGCG or curcumin to enhance treatment effectiveness in a future medication plan.