Membrane-bound carbonic anhydrases are key pH regulators controlling tumor growth and cell migration

The present study involves the synthesis of a series of new imidazole-2-ones derivatives and their 2-thione analogs using conventional heating and the environmentally friendly benign technique, the microwave technique. Structure of the compounds was well elucidated by considering the data of both elemental and spectral analyses. The obtained data and theoretical values of the synthesized molecules correlated with the proposed molecular structure. Moreover, all the synthesized compounds were evaluated in vitro for antitumor activity against HCT-116 and HeP2 human cancer cell panels and assessed as selective carbonic anhydrase IX isozyme (CA9/CAIX) inhibitors, thereby providing useful preliminary evidence for drug development. In addition, computational techniques were used to investigate the molecular and electronic characteristics of the investigated organic compounds. The 4b compound exhibited the best quantum chemistry features, as the highest occupied molecular orbital, softness, energy gap, and dipole moment, indicating the highest biological activity. This was supported by the experimental findings. Moreover, the in silico evaluation of drug candidates was also investigated. Thereafter, the anticancer activity of the most reactive candidate was studied via molecular docking to determine the types of interactions between this molecule and CAIX. According to the docking experiments, the 4b molecule generates five hydrogen bond interactions with active amino acid residues, Gln 92, Gln 67, and Thr 200.

Most cancer cells rely on glycolytic metabolism to sustain their high proliferation demands. In this metabolic phenotype, a considerable part of the consumed glucose is converted into lactic acid, and this is associated with important aspects of cancer’s aggressiveness: increased angiogenesis, invasion, metastasis, immune escape and resistance to treatment. To allow the glycolytic flux and prevent intracellular acidosis, cancer cells up-regulate a number of membrane-associated proteins that efficiently mediate the efflux of lactic acid and protons, assuring pH regulation. These proteins include monocarboxylate transporters (MCTs), carbonic anhydrases (CAs), Na⁺/H⁺ exchangers (NHEs), vacuolar-type H⁺-ATPases (V-ATPases) and the anion exchangers (AEs). Here we will look at the role these proteins play as biomarkers of diagnosis and prognosis, as well as their role as potential targets for cancer therapy, in pre-clinical models and in clinical settings.

This work focused on design, synthesis and application of an AIE and FRET-based BODIPY pH sensor bearing large Stoke shift. The cyano-diphenylethylene- conjugated BODIPY derivative 4 was prepared by condensating 4-hydroxybenzene acetonitrile with 4-(diethoxymethyl)benzaldehyde and then following the typical procedure of synthesizing BODIPY derivative. Compound 4 exhibited strong fluorescence in all kinds of THF/H₂O solutions due to the AIE and FRET effect. The Stoke shift of compound 4 was as large as 138 nm based on the excitation of cyano-diphenylethylene moiety and the emission of BODIPY moiety. Compound 4 showed good fluorescent response to the change of pH with the pKa value at 9.79. The mechanism of compound 4 as pH probe was confirmed by ¹H NMR spectra and theoretical calculation. Compound 4 was successfully used to CO₃²⁻ detection among 13 kinds of common anions both in solution and by tested strips. The experiments of living cell imaging suggested that compound 4 possessed superior bioimaging performance and presented sensitive change to pH values between 9 and 10 in living cells.

Altered metabolism, associated with acidification of the extracellular milieu, is one of the major features of cancer. As pH regulation is crucial for the maintenance of all biological functions, cancer cells rely on the activity of lactate exporters and proton transporters to regulate their intracellular pH. The major players in cancer pH regulation are proton pump ATPases, sodium-proton exchangers (NHEs), monocarboxylate transporters (MCTs), carbonic anhydrases (CAs) and anion exchangers (AEs), which have been shown to be upregulated in several human malignancies. Thanks to the activity of the proton pumps and transporters, tumours acidify their microenvironment, becoming more aggressive and resistant to therapy. Thus, targeting tumour pH may contribute to more effective anticancer strategies for controlling tumour progression and therapeutic resistance. In the present study, we review the role of the main pH regulators expressed in human cancer cells, including their diagnostic and prognostic value, as well as their usefulness as therapeutic targets.

Dual-tail approach was employed to design novel Carbonic Anhydrase (CA) IX inhibitors by simultaneously matching the hydrophobic and hydrophilic halves of the active site, which also contains a zinc ion as part of the catalytic center. The classic sulfanilamide moiety was used as the zinc binding group. An amino glucosamine fragment was chosen as the hydrophilic part and a cinnamamide fragment as the hydrophobic part in order to draw favorable interactions with the corresponding halves of the active site. In comparison with sulfanilamide which is largely devoid of the hydrophilic and hydrophobic interactions with the two halves of the active site, the compounds so designed and synthesized in this study showed 1000-fold improvement in binding affinity. Most of the compounds inhibited the CA effectively with IC₅₀ values in the range of 7–152 nM. Compound 14e (IC₅₀: 7 nM) was more effective than the reference drug acetazolamide (IC₅₀: 30 nM). The results proved that the dual-tail approach to simultaneously matching the hydrophobic and hydrophilic halves of the active site by linking hydrophobic and hydrophilic fragments was useful for designing novel CA inhibitors. The effectiveness of those compounds was elucidated by both the experimental data and molecular docking simulations. This work laid a solid foundation for further development of novel CA IX inhibitors for cancer treatment.

In their quest for survival and successful growth, cancer cells optimise their cellular processes to enable them to outcompete normal cells in their microenvironment. In essence cancer cells: (i) enhance uptake of nutrients/metabolites, (ii) utilise nutrients more efficiently via metabolic alterations and (iii) deal with the metabolic waste products in a way that furthers their progression while hampering the survival of normal tissue. Hypoxia Inducible Factors (HIFs) act as essential drivers of these adaptations via the promotion of numerous membrane proteins including glucose transporters (GLUTs), monocarboxylate transporters (MCTs), amino-acid transporters (LAT1, xCT), and acid-base regulating carbonic anhydrases (CAs). In addition to a competitive growth advantage for tumour cells, these HIF-regulated proteins are implicated in metastasis, cancer ‘stemness’ and the immune response. Current research indicates that combined targeting of these HIF-regulated membrane proteins in tumour cells will provide promising therapeutic strategies in the future.