Selective Inhibition of Carbonic Anhydrase IX Decreases Cell Proliferation and Induces Ceramide-Mediated Apoptosis in Human Cancer Cells

Abstract

Recently, carbonic anhydrase (CA) inhibitors have been proposed as a potential new class of antitumor agents. The aim of this study was to evaluate the antitumor activity of three CA inhibitors, namely acetazolamide (AZ) and two newly synthesized aromatic sulfonamides with high affinity for CA IX, 2-(4-sulfamoylphenyl-amino)-4,6-dichloro-1,3,5-triazine (TR1) and 4-[3-(N,N-dimethylaminopropyl)thioreidophenylsulfonylaminoethyl]benzenesulfonamide (GA15), against human tumor cells. The effects of AZ, TR1, and GA15 on cell proliferation and apoptosis were evaluated in CA IX-positive HeLa and 786-O cells and CA IX-negative 786-O/von Hippel-Lindau (VHL) cells. We also investigated whether the potential antitumor activity of these molecules might be mediated by an increase in ceramide production. AZ, TR1, and GA15 could significantly reduce cell proliferation and induce apoptosis in HeLa and 786-O cells. Moreover, all three inhibitors could decrease intracellular pH (pH i ) and increase ceramide production in the same cells. Treatment with the ceramide synthase inhibitor fumonisin B1 prevented the apoptotic effects of the three CA inhibitors. In all experiments, the effects of aromatic sulfonamides were more pronounced than those of AZ. The three inhibitors did not show any antitumor activity in CA IX-negative 786-O/VHL cells and failed to lower pH i or increase intracellular ceramide levels in the same cells. In conclusion, CA inhibition can decrease cell proliferation and induce apoptosis in human tumor cells. The ability of CA inhibitors to decrease pH i might trigger cell apoptosis through mediation of ceramide synthesis. Activation of this apoptotic cascade probably is mediated by inhibition of the CA IX isoform.

Identification of Metal Dithiocarbamates as a Novel Class of Antileishmanial Agents

“…Several studies suggested that cell death induced by intracellular acidosis can also be exploited for therapeutic purposes. For example, lowering of pH i by pharmacological inhibition of CAIX has been shown to activate ceramidemediated apoptosis in human cancer cells (43). This finding was corroborated by in vivo experiments where CAIX gene silencing led to a 40% reduction in xenograft tumor volume in mice (44).…”

Sulfamate inhibitor S4 influences carbonic anhydrase IX ectodomain shedding in colorectal carcinoma cells

“…Thus, it seems that the method and the timing used for measuring survival and proliferation is critical for the end results. The mechanisms for inhibiting cell survival by CAIX inhibitors are not well understood, but have previously been related to CAIX's role in maintaining a stable pHi in acidic environments [32][33][34] . To investigate if the reduced clonogenicity observed in HT29 cells was a result of such interference, pHi was measured.…”

Dorzolamide synergizes the antitumor activity of mitomycin C against Ehrlich’s carcinoma grown in mice: role of thioredoxin-interacting protein

“…Recently, CA was demonstrated to support the pH homeostasis through controlling the intracellular proton level (Hulikova et al 2011), and its inhibition with CA inhibitors induces a state of intracellular acidification (Cianchi et al 2010).…”

“…Indeed, many authors showed that CA inhibitors produced a drop in the intracellular pH of several cell lines (Cianchi et al 2010;Hulikova et al 2011). Interestingly, the tumor suppressor thioredoxin-interacting protein (TXNIP) is transcriptionally induced by stresses and stimuli, and some of them may act through modulating the intracellular pH (Chen et al 2010).…”