Identification of potential tumour-associated carbonic anhydrase isozyme IX inhibitors: atom-based 3D-QSAR modelling, pharmacophore-based virtual screening and molecular docking studies.

Tumour hypoxia results in dramatic changes in the gene expression, proliferation and survival of tumour cells. The tumour cells shift towards anaerobic glycolysis which results in change of pH in their microenvironment. In response to this stress, over expression of carbonic anhydrase IX (CA IX) genes is observed in many solid tumours. So, selective inhibition of CA IX can be a promising target for anti-cancer drugs. In this work in silico tools like atom-based 3D-QSAR modelling, pharmacophore-based virtual screening and molecular docking were used to identify potential CA IX inhibitors. Based on the training set used in the QSAR model, twenty pharmacophore models were generated. Out of these, HHHR_1, AHHR_1, DHHHR_1, AHHHR_1 model was used to screen a database of 1,50,000 compounds retrieved from ZINC 15 database. R2 and Q2 was 0.9864 and 0.8799, respectively, for the developed QSAR model. 163 compounds showed a phase screen score above 2.4 in which ZINC02260669 was the highest ranked (screen score, 2.852058) compound in all the four models. Built QSAR model was used to predict the activity of all these 163 compounds and ZINC72370966 showed the highest predicted activity with pKi value of 7.649. These compounds were docked against CA IX (human) protein (PDB ID 5FL6) and molecular docking results showed favourable binding interactions for the best ten identified hits. This work gives design insights and some potential scaffolds which can be developed as CA IX inhibitors.Communicated by Ramaswamy H. Sarma.

Immunohistochemical Localizaion of Carbonic Anhydrase Isozymes IV and IX in Rat Salivary Gland / 대한해부학회지

This study presents distribution of carbonic anhydrase (CA) isozymes IV and IX, membrane associated forms, and CA I and II, cytoplasmic forms, in rat parotid and submandibular glands using Western blot analysis and immunohistochemical staining. Western blot analysis demonstrated that CAs I, II and IX were found to be abundantly expressed, but CA IV was weakly expressed in parotid gland. Submandibular gland expressed abundant CAs I and II, weak CA IX, and undetectable level of CA IV. In hematoxylin-eosin staining, parotid gland was entirely composed of serous acini and their ducts while submandibular gland was mixed population of serous and mucous lobules. Most of lobules (submandibular gland proper type) contained mostly serous acini and their ducts with granular convoluted duct. Some lobules (sublingual gland type) contained mostly mucous acini with serous demilune and their ducts without granular convoluted duct. In parotid gland, CAs IV and IX were immunolocalized in duct cells and not in serous acinar cells. Immunoreactivity for CAs I and II was also detectable in duct cells. Serous acinar cells were positive for CA II, and negative for CA I. In submandibular gland, CAs IV and IX were immunolocalized in duct cells but not in acinar cells of both types of lobules. Immunoreactivity for CAs I and II was also detectable in duct cells of both types of lobules. Cells of serous acini and serous demilune were positive for CA II, and negative for CA I. Mucous cells were negative for both CAs I and II. These results demonstrate the distribution of CA isoenzymes in parotid and submandibular glands of the rat, and suggest CAs IV and IX as well as CAs I and II are related to electrolytes metabolism of saliva in duct cells.