Inhibition of CD73 expression or A2AR blockade reduces MRP1 expression and increases the sensitivity of cervical cancer cells to cisplatin.

Recently, a link between the biological activity of CD73 in solid tumors and multidrug resistance protein (MRP) has been proposed. Cisplatin (CP) is the most widely used anticancer agent to treat advanced and recurrent cervical cancer (CC). However, multidrug resistance protein-1 (MRP1) is overexpressed in approximately 85% of these tumors and has been strongly associated with cisplatin resistance (CPR). In this study, we examine the involvement of CD73 and the interaction of adenosine (ADO) with its receptors (ARs) in MRP1 expression in CC cells. We found that ADO positively modulates MRP1 expression in CC cells in a dose-dependent manner. The inhibition of CD73 expression with a CD73-targeted siRNA and A2AR blockade with the selective antagonist ZM241385 significantly decreased MRP1 expression and the extrusive capacity of CC cells, making them significantly more sensitive to CP treatment than cancer cells treated with MK-751, a specific MRP1 inhibitor. These results suggest CD73 inhibition or blocking ADO signaling through A2AR could be strategies to reverse CPR in patients with advanced or recurrent CC, which is characterized by very low response rates to CP (10%-20%).

Evidence that cervical cancer cells cultured as tumorspheres maintain high CD73 expression and increase their protumor characteristics through TGF-ß production.

Recently, a link between the biological activity of CD73 and tumorigenicity in solid tumors has been proposed. We previously reported that the generation of adenosine (Ado) by the activity of CD73 in cervical cancer (CC) cells induces transforming growth factor-beta 1 (TGF-ß1) production to maintain CD73 expression. In the present study, we analyzed the participation of TGF-ß1 in CD73 expression and the development of protumoral characteristics in CaSki CC cells cultured as tumorspheres (CaSki-T) and in monolayers (CaSki-M). Compared with those in CaSki-M cells, CD73 expression and Ado generation ability were significantly increased in CaSki-T cells. CaSki-T cells exhibited enrichment in the CSC-like phenotype due to increases in the expression levels of stem cell markers (CD49f, CK17, and P63; OCT4 and SOX2), greater sphere formation efficiency (SFE), and an increase in the percentage of side population (SP) cells. Interestingly, compared with CaSki-M cells, CaSki-T cells produced a greater amount of TGF-ß1 and presented a marked protumor phenotype characterized by a significant decrease in the expression of major histocompatibility complex class-I (MHC-I) molecules, an increase in the expression of multidrug resistance protein-I (MRP-I) and vimentin, and an increase in the protein expression levels of Snail-1 and Twist, which was strongly reversed with TGF-ß1 inhibition. These results suggest that the presence of TGF-ß1-CD73-Ado feedback loop can promote protumoral characteristics in the CC tumor microenvironment.