The overexpression and activity of carbonic anhydrase (CA, EC 4.2.1.1) isoforms CA IX and CA XII promote the accumulation of exceeding protons and acidosis in the extracellular tumor environment. Sulfonamides are effective inhibitors of most families of CAs. In this study, using scaffold-hopping, indoline-5-sulfonamide analogs 4a–u of the CA IX-selective inhibitor 3 were designed and synthesized to evaluate their biological properties. 1-Acylated indoline-5-sulfonamides demonstrated inhibitory activity against tumor-associated CA IX and XII with K_I values up to 132.8 nM and 41.3 nM. Compound 4f, as one of the most potent inhibitors of CA IX and XII, exhibits hypoxic selectivity, suppressing the growth of MCF7 cells at 12.9 µM, and causes partial inhibition of hypoxia-induced CA IX expression in A431 skin cancer cells. 4e and 4f reverse chemoresistance to doxorubicin of K562/4 with overexpression of P-gp.

An effective approach to 5-triazolyl-substituted 6,7-dihydrobenzo[d]isoxazol-4(5H)-ones and 4,5,6,7-tetrahydrobenzo[d]isoxazoles was developed. The approach included α-keto bromination of 6,7-dihydrobenzo[d]isoxazol-4(5H)-one followed by nucleophilic substitution of bromine with the azide group. For the preparation of 5-azido-6,7-dihydrobenzo[d]isoxazol-4(5H)-one, the carbonyl group at position 4 was reduced to a methylene group under ionic hydrogenation conditions using triethylsilane as a reducing agent. Cu(I)-catalyzed [2+3] cycloaddition of terminal alkynes to both obtained azides was used for the synthesis of two series of triazolyl derivatives. Compounds, which contain in their structures common for some Hsp90 inhibitors 2,4-dihydroxy-5-isopropylphenyl fragment, were evaluated as antiproliferative agents against two breast cancer cell lines: hormone-dependent MCF7 and HER2-positive HCC1954. The lead compound showed half-maximal inhibitory concentration (IC 50 ) values below 5 μM and induced significant changes in the Hsp90 signaling pathways in HER2-positive HCC1954 cells. It increased the expression of Hsp70 (used as a pharmacodynamic marker of Hsp90 inhibition) and inhibited the expression of HER2, p-c-Met, c-Met, and p-AKT. The combination of the selected isoxazole-triazole hybrid molecule and the earlier described apoptosis inducer LCTA-3344 demonstrated a significant antiproliferative effect against HCC1954 cells. The lead compound was revealed to be a promising candidate for future anticancer drug design, particularly against aggressive breast cancer positive for HER2.

A series of sulfonamide-derived quinoxaline 1,4-dioxides were synthesized and evaluated as inhibitors of carbonic anhydrases (CA) with antiproliferative potency. Overall, the synthesized compounds demonstrated good inhibitory activity against four CA isoforms. Compound 7g exhibited favorable potency in inhibiting a CA IX isozyme with a K_i value of 42.2 nM compared to the reference AAZ (K_i = 25.7 nM). Nevertheless, most of the synthesized compounds have their highest activity against CA I and CA II isoforms over CA IX and CA XII. A molecular modeling study was used for an estimation of the binding mode of the selected ligand 7g in the active site of CA IX. The most active compounds (7b, 7f, 7h, and 18) exhibited significant antiproliferative activity against MCF-7, Capan-1, DND-41, HL60, and Z138 cell lines, with IC₅₀ values in low micromolar concentrations. Moreover, derivatives 7a, 7e, and 8g showed similar hypoxic cytotoxic activity and selectivity compared to tirapazamine (TPZ) against adenocarcinoma cells MCF-7. The structure–activity relationships analysis revealed that the presence of a halogen atom or a sulfonamide group as substituents in the phenyl ring of quinoxaline-2-carbonitrile 1,4-dioxides was favorable for overall cytotoxicity against most of the tested cancer cell lines. Additionally, the presence of a carbonitrile fragment in position 2 of the heterocycle also had a positive effect on the antitumor properties of such derivatives against the majority of cell lines. The most potent derivative, 3-trifluoromethylquinoxaline 1,4-dioxide 7h, demonstrated higher or close antiproliferative activity compared to the reference agents, such as doxorubicin, and etoposide, with an IC₅₀ range of 1.3–2.1 μM. Analysis of the obtained results revealed important patterns in the structure–activity relationship. Moreover, these findings highlight the potential of selected lead sulfonamides on the quinoxaline 1,4-dioxide scaffold for further in-depth evaluation and development of chemotherapeutic agents targeting carbonic anhydrases.

Breast and other estrogen receptor α-positive cancers tend to develop resistance to existing drugs. Chalcone derivatives possess anticancer activity based on their ability to form covalent bonds with targets acting as Michael acceptors. This study aimed to evaluate the anticancer properties of a series of chalcones (7a–l) with a sulfonamide group attached to the vinyl ketone moiety. Chalconesulfonamides showed a potent antiproliferative effect at low micromolar concentrations against several cancer cell lines, including ERα-positive 4-hydroxytamoxifen-resistant MCF7/HT2. Immunoblotting of samples treated with the lead compound 7e revealed its potent antiestrogenic activity (ERα/GREB1 axis) and induction of PARP cleavage (an apoptosis marker) in breast cancer cells. The obtained compounds represent a promising basis for further development of targeted drugs blocking hormone pathways in cancer cells.

Cancer is one of the leading causes of death worldwide, accounting for about 10 million deaths a year, or nearly one in six deaths. The most common types of cancer are breast, colorectal, lung, and prostate cancers. Prolonged application of hormone drugs leads to the development of resistance. The development of agents with high activity against resistant cells is a challenge. It is important to create novel targeted compounds and search for active molecules among those previously developed. The study aimed to evaluate the sensitivity of 4-hydroxytamoxifen-resistant cells to 5-fluorouracil (5-FU) and analyse the signalling pathways that are regulated by 5-FU in breast cancer cells. Antiproliferative activity of compounds was assessed by the MTT assay, and immunoblotting was used to evaluate the expression of proteins in breast cancer cells. Activity of 5-FU was evaluated on parental MCF7 cells and a cell subline with resistance to 4-hydroxytamoxifen (HT), named MCF7/HT. The MCF7/HT cells showed high sensitivity to 5-FU. Expression of oestrogen receptor α (ERα, a key driver of breast cancer growth) in MCF7 and MCF7/HT cells was not sensitive to 5-FU treatment. In both parental and resistant cells, 5-FU induced changes in the activity of several signalling proteins. 5-FU activated AKT, extracellular signal-regulated kinase 1/2 (ERK 1/2) and upregulated cyclin D1 expression. The data suggest that 5-FU should be further investigated as a chemotherapeutic for hormone-resistant cancers; the combination of 5-FU with novel apoptosis inducer LCTA-3344 is considered effective to inhibit the growth of breast cancer cells, including those that are hormone-resistant.