Abstract B222: Anticancer effects of S4, a new carbonic anhydrase inhibitor, on MDA-MB-231 and HCT116 tumors.
Authors: Gieling Roben G. , Babur Muhammad , Telfer Brian A. , Williams Steve , Davies Karen , Scozzafava Andrea , Supuran Claudiu , Williams Kaye J. 
Published: June 2012

Carbonic anhydrase IX (CA IX) is strongly overexpressed in multiple human solid tumours in response to oxygen deprivation (hypoxia). In tumours high CA-IX expression is closely associated with higher incidence of metastasis and poor prognosis. Hypoxic tumours are also less sensitive to classical chemo- and radiotherapy. The potential of CA-IX in cancer therapy has encouraged the search for potent and selective CA-IX inhibitors over recent years. We have evaluated a panel of novel aromatic sulphonamide inhibitors of CA-IX for their anti-metastatic potential and ability to enhance response to standard therapies. From an initial screen of 10 agents, the compound S4 (whose complete chemical structure will be disclosed at the time of the presentation) showed potent inhibition of cell migration and cell spreading under hypoxic conditions in MDA231 breast cancer cells. In MTT assays, the cytotoxicity to MDA231 cells exposure to S4 for 24 or 96 hours revealed an IC50 of 48 μM and 27 μM, subsequently. Under complete hypoxia for 24 hours (anoxia), S4 in the 33–100 μM range inhibited the migration of MDA231 cells and cell spreading on collagen and fibronectin coated coverslips. In vivo S4 was evaluated in mice bearing xenografts of breast or colon carcinoma tumours i.e. MDA-MB-231 or HCT116 tumours, respectively. MDA231 tumours were established within the mammary fat pad and HCT116 within the liver following intrasplenic injection. We investigated the effect of i.p. administration of S4 on primary tumour growth and on metastases formation in the lung. S4 was given at the maintenance dosage of 10 mg/kg on 5 days on 2 days off regiment for two whole cycles for the duration of the experiment. Ex vivo clonogenicity assays or counting of tumours in haematoxylin & eosin stained sections of lung indicated that S4 treatment reduced the number of viable cells that metastasised to the lung in both models. The primary tumour growth of MDA231 and HCT116 were not affected by the S4. T2-weighted MR imaging (Rare) was successfully used to identify and monitor the HCT116 tumour growth within livers. In preliminary in vitro studies using 3D-spheroid cultures, S4 appears also capable of enhancing chemo- and radiotherapy response. Clonogenicity assays showed that S4 was able to enhance the cytotoxic effect of the anticancer drug doxorubicin hydrochloride (10 μM) against FaDu spheroids by reducing the number of recovered colonies. S4 also enhanced cell death induced by a single dose of 10 Gy of radiation to FaDu spheroids. The precise mechanisms by which CA IX inhibition via S4 impacts on chemotherapy, radiation response and migratory phenotype is as yet unclear, but changes in pH environment, effects on proliferation, apoptosis and interplay with migratory machinery have all been associated with CA IX activity. We conclude that CA IX inhibition is an attractive therapeutic approach with multiple applications in the clinical setting. We acknowledge the financial support from the European Commission for the METOXIA program.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B222.