Tumor microenvironmental changes induced by the sulfamate carbonic anhydrase IX inhibitor S4 in a laryngeal tumor model

BACKGROUND AND PURPOSE: Carbonic anhydrase IX (CAIX) plays a pivotal role in pH homeostasis, which is essential for tumor cell survival. We examined the effect of the CAIX inhibitor 4-(3'(3",5"-dimethylphenyl)-ureido)phenyl sulfamate (S4) on the tumor microenvironment in a laryngeal tumor model by analyzing proliferation, apoptosis, necrosis, hypoxia, metabolism and CAIX ectodomain shedding. METHODS: SCCNij202 tumor bearing-mice were treated with S4 for 1, 3 or 5 days. CAIX ectodomain shedding was measured in the serum after therapy. Effects on tumor cell proliferation, apoptosis, necrosis, hypoxia (pimonidazole) and CAIX were investigated with quantitative immunohistochemistry. Metabolic transporters and enzymes were quantified with qPCR. RESULTS: CAIX ectodomain shedding decreased after treatment with S4 (p<0.01). S4 therapy did neither influence tumor cell proliferation nor the amount of apoptosis and necrosis. Hypoxia (pimonidazole) and CAIX expression were also not affected by S4. CHOP and MMP9 mRNA as a reference of intracellular pH did not change upon treatment with S4. Compensatory mechanisms of pH homeostasis at the mRNA level were not observed. CONCLUSION: As the clinical and biological meaning of the decrease in CAIX ectodomain shedding after S4 therapy is not clear, studies are required to elucidate whether the CAIX ectodomain has a paracrine or autocrine signaling function in cancer biology. S4 did not influence the amount of proliferation, apoptosis, necrosis and hypoxia. Therefore, it is unlikely that S4 can be used as single agent to influence tumor cell kill and proliferation, and to target primary tumor growth

Characterization of Carbonic Anhydrase IX Interactome Reveals Proteins Assisting Its Nuclear Localization in Hypoxic Cells

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Apoptosis-induced ectodomain shedding of hypoxia-regulated carbonic anhydrase IX from tumor cells: a double-edged response to chemotherapy.

BACKGROUND: Carbonic anhydrase IX (CA IX) is a tumor-associated, highly active, transmembrane carbonic anhydrase isoform regulated by hypoxia and implicated in pH control and adhesion-migration-invasion. CA IX ectodomain (ECD) is shed from the tumor cell surface to serum/plasma of patients, where it can signify cancer prognosis. We previously showed that the CA IX ECD release is mediated by disintegrin and metalloproteinase ADAM17. Here we investigated the CA IX ECD shedding in tumor cells undergoing apoptosis in response to cytotoxic drugs, including cycloheximide and doxorubicin. METHODS: Presence of cell surface CA IX was correlated to the extent of apoptosis by flow cytometry in cell lines with natural or ectopic CA IX expression. CA IX ECD level was assessed by ELISA using CA IX-specific monoclonal antibodies. Effect of recombinant CA IX ECD on the activation of molecular pathways was evaluated using the cell-based dual-luciferase reporter assay. RESULTS: We found a significantly lower occurrence of apoptosis in the CA IX-positive cell subpopulation than in the CA IX-negative one. We also demonstrated that the cell-surface CA IX level dropped during the death progress due to an increased ECD shedding, which required a functional ADAM17. Inhibitors of metalloproteinases reduced CA IX ECD shedding, but not apoptosis. The CA IX ECD release induced by cytotoxic drugs was connected to elevated expression of CA IX in the surviving fraction of cells. Moreover, an externally added recombinant CA IX ECD activated a pathway driven by the Nanog transcription factor implicated in epithelial-mesenchymal transition and stemness. CONCLUSIONS: These findings imply that the increased level of the circulating CA IX ECD might be useful as an indicator of an effective antitumor chemotherapy. Conversely, elevated CA IX ECD might generate unwanted effects through autocrine/paracrine signaling potentially contributing to resistance and tumor progression

Encapsulation of anti-carbonic anhydrase IX antibody in hydrogel microspheres for tumor targeting

<p>Encapsulation is a well-established method of biomaterial protection, controlled release, and efficient delivery. Here we evaluated encapsulation of monoclonal antibody M75 directed to tumor biomarker carbonic anhydrase IX (CA IX) into alginate microbeads (SA-beads) or microcapsules made of sodium alginate, cellulose sulfate, and poly(methylene-co-guanidine) (PMCG). M75 antibody release was quantified using ELISA and its binding properties were assessed by immunodetection methods. SA-beads showed rapid M75 antibody release in the first hour, followed by steady release during the whole experiment of 7 days. In contrast, the M75 release from PMCG capsules was gradual, reaching the maximum concentration on the 7th day. The release was more efficient at pH 6.8 compared to pH 7.4. The released antibody could recognize CA IX, and target the CA IX-positive cells in 3D spheroids. In conclusion, SA-beads and PMCG microcapsules can be considered as promising antibody reservoirs for targeting of cancer cells.</p

Intracellular pH and CAIX inhibition in SCCNij202.

<p>S4 does not change CHOP mRNA (A) and MMP9 mRNA (B). Abbreviations: CHOP, C/EBP homologous protein; MMP9, matrix metallopeptidase 9; NS, not significant; 1× S4, 8 h, one i.p. injection S4, harvest after 8 hours; 1× S4, 24 h, one i.p. injection S4, harvest after 24 hours; 3× S4, one i.p. injection S4 a day for 3 days, harvest 8 hours after the last injection; 5× S4, one i.p. injection S4 a day for 5 days, harvest 8 hours after the last injection.</p

No cytotoxic effects of CAIX inhibition in SCCNij202.

<p>S4 does not affect proliferation within CAIX positive areas (A), apoptosis within CAIX positive areas (B) or the amount of necrosis (C). Abbreviations: BrdUrd, bromodeoxyuridine; CAIX, carbonic anhydrase IX; LI, labeling index; NS, not significant, 1× S4, 8 h, one i.p. injection S4, harvest after 8 hours; 1× S4, 24 h, one i.p. injection S4, harvest after 24 hours; 3× S4, one i.p. injection S4 a day for 3 days, harvest 8 hours after the last injection; 5× S4, one i.p. injection S4 a day for 5 days, harvest 8 hours after the last injection.</p

CAIX ectodomain shedding after treatment with S4.

<p>S4 decreases CAIX ectodomain shedding in the serum, especially 8 hours after the first injection. Abbreviations: CAIX, carbonic anhydrase IX; 1× S4, 8 h, one i.p. injection S4, harvest after 8 hours; 1× S4, 24 h, one i.p. injection S4, harvest after 24 hours; 3× S4, one i.p. injection S4 a day for 3 days, harvest 8 hours after the last injection; 5× S4, one i.p. injection S4 a day for 5 days, harvest 8 hours after the last injection.</p