6-Substituted Sulfocoumarins Are Selective Carbonic Anhdydrase IX and XII Inhibitors with Significant Cytotoxicity against Colorectal Cancer Cells

Abstract

6-Substituted sulfocoumarins bearing the carboxamido, trimethylammonium as well as the cyano and methoxy moieties with interesting inhibitory activity/selectivity against the tumor associated carbonic anhydrase (CA, EC 4.2.1.1) isoforms hCA IX and XII are reported. Moieties leading to the best inhibition were tert-butylcarboxamido, phenylcarboxamido, and 4-pyridylcarboxamido, with K(I) values of 2.1-8.1 nM. No inhibition of the off-target hCA II and I was observed. A number of these compounds were evaluated against HT-29 colon cancer cell lines ex vivo. Compounds 9c and 9e revealed effective cytotoxic effects after 72 h of incubation in both normoxic and hypoxic conditions, unlike sulfonamide CA inhibitors that show such effects only in hypoxia. These results may be of particular importance for the choice of future drug candidates targeting hypoxic tumors and metastases, considering the fact that a sulfonamide CA IX inhibitor (SLC-0111) is presently in phase I clinical trials.

7-Aryl-triazolyl-substituted sulfocoumarins are potent, selective inhibitors of the tumor-associated carbonic anhydrase IX and XII

“…(i) According to our previous reports [40][41][42][43][44] , isoform hCA I was not or was poorly inhibited by sulfocoumarins 7-14. Compounds 8 and 11 are high micromolar inhibitors, whereas the remaining ones did not significantly inhibit the enzyme below 10 mm inhibitor concentration.…”

“…Many synthetic efforts have been made for the development of specific CAIs: in the last 15 years, in addition to the classical ''tail approach'' [10][11][12][13][14][15][16][17][25][26][27][28] which is mainly applied to classical sulfonamide inhibitors and their isosters, novel CAIs scaffolds have been also identified such as the polyamines 29 , phenols [30][31][32] , dithiocarbamates [33][34][35][36] , xanthates 37 , coumarins, thiocoumarins, 2-thioxocoumarins, coumarine oximes 4,38,39 . Sulfocoumarins are the latest CAI class identified and similarly to the coumarins showed the most selective inhibition profiles against the pathologically valuable CA isoforms 1,9,[40][41][42][43][44] . In analogy to coumarins, the substitution pattern at the sulfocoumarin scaffolds strongly influences the potency and selectivity profile against different hCA isoforms 1, [40][41][42][43][44] .…”

“…Sulfocoumarins are the latest CAI class identified and similarly to the coumarins showed the most selective inhibition profiles against the pathologically valuable CA isoforms 1,9,[40][41][42][43][44] . In analogy to coumarins, the substitution pattern at the sulfocoumarin scaffolds strongly influences the potency and selectivity profile against different hCA isoforms 1, [40][41][42][43][44] . Indeed, in our previous reports [40][41][42][43] , we investigated large series of sulfocoumarins bearing the tetrazolyl, triazolyl or aryl/alkyl moieties at 6 position, which showed low nanomolar hCAIX/ XII inhibitory potencies, without particular effects on the cytosolic hCAI/II.…”

“…In analogy to coumarins, the substitution pattern at the sulfocoumarin scaffolds strongly influences the potency and selectivity profile against different hCA isoforms 1, [40][41][42][43][44] . Indeed, in our previous reports [40][41][42][43] , we investigated large series of sulfocoumarins bearing the tetrazolyl, triazolyl or aryl/alkyl moieties at 6 position, which showed low nanomolar hCAIX/ XII inhibitory potencies, without particular effects on the cytosolic hCAI/II. On the contrary, derivatives bearing small substituents as well as benzyl esters at the 7 position act as low nanomolar hCAII inhibitors 40 .…”

Tumor metabolism, cancer cell transporters, and microenvironmental resistance

“…Carbonic anhydrase inhibitors are divided into four groups: inorganic anions, sulfonamidebased compounds (sulphonamides, sulfanilamides, sulphamates, and their derivatives), phenols, and coumarins 105 . A sulfonamide CA9 inhibitor (SLC-0111) is presently in Phase I clinical trials 107 . It has been shown that simultaneous inhibition of both CA9 and CA12 has a greater impact than inhibition of each individually or even inhibition of HIF-a 105 .…”