Inhibition of pH regulation as a therapeutic strategy in hypoxic human breast cancer cells

Abstract

Hypoxic cancer cells exhibit resistance to many therapies. This study compared the therapeutic effect of targeting the pH regulatory proteins (CAIX, NHE1 and V-ATPase) that permit cancer cells to adapt to hypoxic conditions, using both 2D and 3D culture models. Drugs targeting CAIX, NHE1 and V-ATPase exhibited anti-proliferative effects in MCF-7, MDA-MB-231 and HBL-100 breast cancer cell lines in 2D. Protein and gene expression analysis in 2D showed that CAIX was the most hypoxia-inducible protein of the 3 targets. However, the expression of CAIX differed between the 3 cell lines. This difference in CAIX expression in hypoxia was consistent with a varying activity of FIH-1 between the cell lines. 3D expression analysis demonstrated that both CAIX and NHE1 were up-regulated in the hypoxic areas of multicellular tumor spheroids. However, the induction of CAIX expression in hypoxia was again cell line dependent. 3D invasion assays conducted with spheroids showed that CAIX inhibition significantly reduced the invasion of cells. Finally, the capability of both NHE1 and CAIX inhibitors to combine effectively with irradiation was exhibited in clonogenic assays. Proteomic-mass-spectrometric analysis indicated that CAIX inhibition might be combining with irradiation through stimulating apoptotic cell death. Of the three proteins, CAIX represents the target with the most promise for the treatment of breast cancer.

Cellular and radiobiological effects of carbonic anhydrase IX in human breast cancer cells

“…2 and 3). These effects are in line with previous reports that also demonstrated reductions in CA9 mRNA and CAIX protein level in tumor cells in response to treatment with RNA interference or CAI U104 (10,21,22,(34)(35)(36). CAI-induced changes were attributed to the possible degradation or internalization of CAIX (21,36).…”

“…Our previous study indicated that betulin 3,28-disulfamate, which is described as a CAI by Winum et al (20), radiosensitized MDA-MB-231 breast cancer cells (21). Recently, CAI FC9403A but not CAI S4 showed synergistic effects with irradiation in MDA-MB-231 breast cancer spheroids (22). However, to the best of our knowledge, there are no studies regarding the cellular and radiobiological effects of a selective CA9 knockdown with RNA interference or a CAIX/CAXII specific inhibition in human breast cancer cells.…”

Inhibition of carbonic anhydrase IX targets primary tumors, metastases, and cancer stem cells: Three for the price of one

“…Similar effects, on diverse animal models and cancer types were reported by Williams’, Lambin's, and Langdon's groups, using sulfamate or sulfonamide CA IX inhibitors. Furthermore, recently Andreucci et al .…”

“…Similar effects, on diverse animal models and cancer types were reported by Williams' , 150 Lambin's, 268,269 and Langdon's groups, 270,271 using sulfamate or sulfonamide CA IX inhibitors. Furthermore, recently Andreucci et al 272 showed that CA IX inhibition with ureido sulfonamides of types 9-13 leads to a drastic diminution of the viability of the cancer cells adapted to acidosis (which overexpress CA IX).…”

The impact of tumour pH on cancer progression: strategies for clinical intervention

“…The invasive potential of human ductal breast cancer spheroids, along with renal and ovarian cancer cells, was decreased when CAIX expression was reduced or activity was inhibited using novel sulfamate inhibitors of CAIX [191][192][193]. These inhibitors reduced proliferation, enhanced the rates of apoptosis and inhibited metastasis in breast cancer xenografts models, while also exhibiting the potential to reverse the invasion of human breast tumour biopsy tissue [185,192,194,195]. Basal like breast cancers frequently express CAIX and have been associated with high levels of brain, lung and bone metastases [194], leading to suggestions that targeting of CAIX may be a possible approach to combat metastatic disease [194,195].…”