ABCG2 and neoplasm: Finally, knockdown of AhR resulted in significantly reduced tumor growth and malignant characteristics of A549-IR cells in nude mice (Fig. 4g and Supplementary Figure S5F); the expression of stemness signature genes including ABCG2, c-Myc, KLF4, Lgr6, ALDH1A1, and CXCR4 were readily decreased in biopsies of xenograft tumors after knockdown of AhR in A549-IR cells (Fig. 4h).