Through the transfer of transport proteins (such as P-gp, BCRP), immunosuppressive ligands (e.g., PD-L1, TGF-β, PGE2) and non-coding RNA molecules (miRNA, circRNA), exosomes promote the transfer of the resistant phenotype between cancer cells and between cancer cells and the surrounding microenvironment. The gene discussed is ABCG2; the disease is cancer.