P-glycoprotein-mediated chemoresistance is reversed by carbonic anhydrase XII inhibitors

Abstract

Carbonic anhydrase XII (CAXII) is a membrane enzyme that maintains pH homeostasis and sustains optimum P-glycoprotein (Pgp) efflux activity in cancer cells. Here, we investigated a panel of eight CAXII inhibitors (compounds 1–8), for their potential to reverse Pgp mediated tumor cell chemoresistance. Inhibitors (5 nM) were screened in human and murine cancer cells (colon, lung, breast, bone) with different expression levels of CAXII and Pgp. We identified three CAXII inhibitors (compounds 1, 2 and 4) that significantly (≥ 2 fold) increased the intracellular retention of the Pgp-substrate and chemotherapeutic doxorubicin, and restored its cytotoxic activity. The inhibitors lowered intracellular pH to indirectly impair Pgp activity. Ca12-knockout assays confirmed that the chemosensitizing property of the compounds was dependent on active CAXII. Furthermore, in a preclinical model of drug-resistant breast tumors compound 1 (1900 ng/kg) restored the efficacy of doxorubicin to the same extent as the direct Pgp inhibitor tariquidar. The expression of carbonic anhydrase IX had no effect on the intracellular doxorubicin accumulation. Our work provides strong evidence that CAXII inhibitors are effective chemosensitizer agents in CAXII-positive and Pgp-positive cancer cells. The use of CAXII inhibitors may represent a turning point in combinatorial chemotherapeutic schemes to treat multidrug-resistant tumors.

Optical study of chemotherapy efficiency in cancer treatment via intracellular structural disorder analysis using partial wave spectroscopy

“…Other physiological characteristic features that can affect the texture of the cell structure are dysregulated intracellular pH dynamics . The over expression of P‐glycoprotein and other ion channels in the chemoresistant cells alter the ionic efflux and influx from inside and outside of the cell . The altered ionic balance and variation in cell volume , contribute to the variation of characteristic attributes which affects the matrix stiffness and cell texture in chemoresistant cells in comparison to the control cells .…”

An inhibitory antibody targeting carbonic anhydrase XII abrogates chemoresistance and significantly reduces lung metastases in an orthotopic breast cancer model in vivo

“…All cell lines were cultured in RPMI 1640 medium supplemented with 8% v/v fetal bovine serum, 1% v/v l ‐glutamine and 1% v/v penicillin–streptomycin. Chemoresistant cell lines HT29/DX, A549/DX and U2OS/DX were generated out of the parental cell lines as previously described . Cell line identify was confirmed by STR‐PCR (Eurofins).…”

“…Chemoresistant cell lines HT29/DX, A549/DX and U2OS/DX were generated out of the parental cell lines as previously described. 17 Cell line identify was confirmed by STR-PCR (Eurofins).…”

“…Of note, it has been demonstrated recently that CAXII physically interacts with, and regulates the activity of, P‐GP and in chemoresistant cancer cells . In addition, a genetic CAXII knock‐down in P‐GP‐positive cancer cell lines resulted in enhanced chemosensitivity .…”

“…14,15 Of note, it has been demonstrated recently that CAXII physically interacts with, and regulates the activity of, P-GP and in chemoresistant cancer cells. 16,17 In addition, a genetic CAXII knock-down in P-GP-positive cancer cell lines resulted in enhanced chemosensitivity. 16 We show here that the blocking CAXII-specific monoclonal antibody 6A10 interferes with P-GP activity in chemoresistant cancer cell lines, thus increasing the sensitivity against clinically relevant anthracyclines.…”