ABCG2 and cancer: To further investigate the mechanisms underlying the chemoresistance of DP-HCC1806:BMMSCs, we evaluated the changes in the expression pattern of tetraspanin proteins (CD9 and CD81), drug resistance proteins (BCRP and MDR1), and common targets of cancer pathways (p-ERK, pMAPK, mTOR, PI3K, pAKT, and p53) (Figure 5A–5D).