ABCG2 and neoplasm: Thus, we comprehensively examined the ABCG2 gene expression in a total of 33 different tumors based on the TCGA, CPTAC, and GEO databases and analyzed the molecular features of gene expression, prognosis, tumor microenvironment, tumor stemness, and genetic alteration to further explore the multifunctional role of ABCG2 gene in different cancer types.