Differential expression and function of CAIX and CAXII in breast cancer: A comparison between tumorgraft models and cells

Abstract

Carbonic anhydrase IX (CAIX) and XII (CAXII) are transmembrane proteins that are associated with cancer progression. We have previously described the catalytic properties of CAIX in MDA-MB-231 breast cancer cells, a line of cells that were derived from a patient with triple negative breast cancer. We chose this line because CAIX expression in breast cancer is a marker of hypoxia and a prognosticator for reduced survival. However, CAXII expression is associated with better survival statistics than those patients with low CAXII expression. Yet CAIX and CAXII have similar catalytic activities. Here we compare the potential roles of CAIX and CAXII in the context of TNBC and estrogen receptor (ER)-positive breast cancer. In tumor graft models, we show that CAIX and CAXII exhibit distinct expression patterns and non-overlapping. We find the same pattern across a panel of TNBC and luminal breast cancer cell lines. This affords an opportunity to compare directly CAIX and CAXII function. Our data suggest that CAIX expression is associated with growth potentiation in the tumor graft model and in a TNBC line using knockdown strategies and blocking activity with an impermeant sulfonamide inhibitor, N-3500. CAXII was not associated with growth potentiation. The catalytic activities of both CAIX and CAXII were sensitive to inhibition by N-3500 and activated at low pH. However, pH titration of activity in membrane ghosts revealed significant differences in the catalytic efficiency and pKa values. These features provide evidence that CAIX is a more efficient enzyme than CAXII at low pH and that CAIX shifts the equilibrium between CO2 and bicarbonate in favor of CO2 production by consuming protons. This suggests that in the acidic microenvironment of tumors, CAIX plays a role in stabilizing pH at a value that favors cancer cell survival.

β-caryophyllene enhances the transcriptional upregulation of cholesterol biosynthesis in breast cancer cells

“…We first determined the effect of paclitaxel on cell growth ( Supplementary Figure 1). This panel represents a control line (MCF10A), an ER+ luminal line (T47D), and two triple-negative lines (MDA-MB-231-LM2 and UFH-001 [33]). The characteristics of the new UFH-001 line have been described elsewhere [28].…”

Carbonic Anhydrase XII Expression Is Modulated during Epithelial Mesenchymal Transition and Regulated through Protein Kinase C Signaling

“…Thus, modifications in the expression of CA isoenzymes may have profound effects on cell physiology. This is based on in vitro, ex-vivo, and clinical data [5][6][7][8][9][10]. The CAIX is one of the best-studied members of this family [6].…”

Selective inhibition of CA IX over CA XII in breast cancer cells using benzene sulfonamides: Disconnect between CA activity and growth inhibition

“…That differences in the K i values are based on technique seems unlikely because the rate constants calculated for recombinant CA IX are similar across these techniques (63)(64)(65). Further, rate constants determined in isolated membranes containing either CA IX or CA XII (22,66) show strikingly similar values, suggesting that the membrane environment does not influence catalytic activity. Yet, we must also consider that the cellular environment (intact cells) adds layers of complexity relative to even isolated membranes.…”

“…For hypoxia treatment, cells were exposed to 1% O 2 , 5% CO 2 and balanced N 2 for 16 h using a Billups Rothenberg Metabolic Chamber. Knockdowns of CA IX and CA XII in UFH-001 and T47D cells, respectively, were generated as described and characterized previously (66).…”