Carbonic anhydrase inhibitors as emerging agents for the treatment and imaging of hypoxic tumors

Suppression of Tumor Growth and Cell Migration by Indole-Based Benzenesulfonamides and Their Synergistic Effects in Combination with Doxorubicin

Pharmacological inhibition of the enzyme activity targeting carbonic anhydrases (CAs) demonstrated antiglaucoma and anticancer effects through pH control. Recently, we reported a series of indole-based benzenesulfonamides as potent CA inhibitors. The present study aimed to evaluate the antitumor effects of these compounds against various cancer cell lines, including breast cancer (MDA-MB-231, MCF-7, and SK-BR-3), lung cancer (A549), and pancreatic cancer (Panc1) cells. Overall, more potent cytotoxicity was observed on MCF-7 and SK-BR-3 cells than on lung or pancreatic cancer cells. Among the 15 compounds tested, A6 and A15 exhibited potent cytotoxic and antimigratory activities against MCF-7 and SK-BR-3 cells in the CoCl₂-induced hypoxic condition. While A6 and A15 markedly reduced the viability of control siRNA-treated cells, these compounds could not significantly reduce the viability of CA IX-knockdown cells, suggesting the role of CA IX in their anticancer activities. To assess whether these compounds exerted synergism with a conventional anticancer drug doxorubicin (DOX), the cytotoxic effects of A6 or A15 combined with DOX were analyzed using Chou−Talalay and Bliss independence methods. Our data revealed that both A6 and A15 significantly enhanced the anticancer activity of DOX. Among the tested pairs, the combination of DOX with A15 showed the strongest synergism on SK-BR-3 cells. Moreover, this combination further attenuated cell migration compared to the respective drug. Collectively, our results demonstrated that A6 and A15 suppressed tumor growth and cell migration of MCF-7 and SK-BR-3 cells through inhibition of CA IX, and the combination of these compounds with DOX exhibited synergistic cytotoxic effects on these breast cancer cells. Therefore, A6 and A15 may serve as potential anticancer agents alone or in combination with DOX against breast cancer.

Carbonic anhydrase XII as biomarker and therapeutic target in ovarian carcinomas

Targeting the tumor-associated carbonic anhydrase XII (CA XII) is considered a promising strategy to improve cancer treatment. As such progress is highly demanded for ovarian carcinomas, the present study aimed to provide deeper information about their CA XII expression profile. A large collection of tissue specimens was stained immunohistochemically with a specific anti-CA XII antibody to evaluate the expression in neoplastic and non-neoplastic epithelial ovarian cells. In addition, flow cytometry was used to measure CA XII expression on tumor cells from malignant ascites fluid. Binding of the antibody revealed a significant CA XII expression in most ovarian carcinoma tissue samples and ascites-derived ovarian carcinoma cells. Moreover, CA XII was expressed at higher levels in ovarian carcinomas as compared to borderline ovarian tumors and non-neoplastic ovarian epithelia. Within the carcinoma tissues, high expression of CA XII was associated with higher tumor grading and a trend towards shorter overall survival. Our results indicate that CA XII plays a crucial role for the malignancy of ovarian carcinoma cells and emphasize the potential of CA XII as a diagnostic marker and therapeutic target in the management of ovarian carcinomas.

Selection and identification of a specific peptide binding to ovarian cancer cells from a phage-displayed peptide library

OBJECTIVES

Ovarian cancer is one of the most fatal gynecological malignancies. It is emergently needed to select a novel molecular fragment as a targeting element for the future development of molecular imaging diagnosis and targeting chemotherapy to ovarian cancer.

RESULTS

After five rounds of biopanning, a total of 44 positive phage clones were selected from final phage displayed peptide library. Nine consensus sequences were found based on the assay of sequencing results, then one clone of each consensus group was characterized and identified further by immunofluorescence assay. The result showed the phage clone R20 presents best targeting capacity. Then we synthesized peptide (OSP2) clone R20 displayed, it was characterized with high specificity and sensitivity binding to human ovarian cancer by a tissue chip assay. The target of OSP2 was predicted and docked as human carbonic anhydrase XII (CA12), an important protein usually deregulated in cancer.

CONCLUSIONS

Taken together, OSP2 and its target indicate a novel investigation way in future to develop novel agent or drug delivery formulation for molecular imaging diagnosis and targeting chemotherapy of ovarian cancer.

Continued Structural Exploration of Sulfocoumarin as Selective Inhibitor of Tumor-Associated Human Carbonic Anhydrases IX and XII

A series of new 3- and 7-substituted sulfocoumarins was obtained by several cyclization reactions and subsequent derivatization for screening as prodrug inhibitors of the human (h) cancer-associated carbonic anhydrases (CAs) IX and XII. All products were ineffective inhibitors against the off-target hCA I and II, whilst hCAs IX and XII were inhibited with inhibition constants (KIs) spanning from low nanomolar to the high micromolar range, according to the sulfocoumarin derivatization pattern. In particular, sulfocoumarin 15 turned out to be the most potent and selective inhibitor herein reported (hCA I and II: KI > 100 µM; hCA IX: KI = 22.9 nM; hCA XII: KI = 19.2 nM). Considering that hCA IX and XII validated anti-tumor targets, such prodrug, isoform-selective inhibitors as the sulfocoumarins reported here may be useful for identifying suitable drug candidates for clinical trials.

A combination strategy of structure-based virtual screening, MM-GBSA, cross docking, molecular dynamics and metadynamics simulations used to investigate natural compounds as potent and specific inhibitors of tumor linked human carbonic anhydrase IX

Cancer remains a serious health concern representing one of the leading causes of deaths worldwide. The enzyme human carbonic anhydrase IX (hCA IX) is found to be over-expressed in many cancer types and its selective inhibition over its cytosolic off-target isoform, human carbonic anhydrase II (hCA II), represents a potential area of research in the development of novel anticancer compounds. This work is concerned with the use of various in silico tools for the identification of natural product based molecules that can selectively inhibit hCA IX over hCA II. MM-GBSA assisted structure-based virtual screening against hCA IX was performed for nearly 225,000 natural products imported from the ZINC15 database. The obtained hits were checked for their potency by considering acetazolamide, the bound inhibitor of hCA IX, as the reference molecule, and 121 molecules were identified as potent hCA IX inhibitors. After ensuring their potency, cross-docking, followed by MM-GBSA calculations of the hits with hCA II, was performed, and their selectivity was assessed by considering the hCA IX selective compound SLC-0111 as the reference molecule, and 50 natural products were identified as potent as well as selective hCA IX inhibitors. Molecules with the quinoline scaffold showed the highest selectivity, and their selectivity was attributed to the strong electrostatic interactions of the zinc binding group (ZBG) with the active site Zn(II) ion. Furthermore, the stability of the binding modes of the top hCA IX selective hits was ensured by performing molecular dynamics (MD) simulations, which clearly proved that one of the short-listed molecules is truly selective, as it does not interact with the active site Zn(II) ion of hCA II, but interacts strongly with this ion in hCA IX. Bonding pose metadynamics studies revealed that the ligand moves to a more stable binding site from the one predicted by the docking studies and shows stronger interaction with the protein and Zn(II) at this binding site. The ligand is not likely to have issues with bioavailability. As a result, this ligand can be taken for bioassay testing and subsequently used as a feasible therapeutic treatment for a variety of cancer types. Communicated by Ramaswamy H. Sarma.

Cloning, purification, kinetic and anion inhibition studies of a recombinant β-carbonic anhydrase from the Atlantic salmon parasite platyhelminth Gyrodactylus salaris

A β-class carbonic anhydrase (CA, EC 4.2.1.1) was cloned from the genome of the Monogenean platyhelminth Gyrodactylus salaris, a parasite of Atlantic salmon. The new enzyme, GsaCAβ has a significant catalytic activity for the physiological reaction, CO₂ + H₂O ⇋ HCO₃⁻ + H⁺ with a k_cat of 1.1 × 10⁵ s⁻¹ and a k_cat/K_m of 7.58 × 10⁶ M⁻¹ × s⁻¹. This activity was inhibited by acetazolamide (K_I of 0.46 µM), a sulphonamide in clinical use, as well as by selected inorganic anions and small molecules. Most tested anions inhibited GsaCAβ at millimolar concentrations, but sulfamide (K_I of 81 µM), N,N-diethyldithiocarbamate (K_I of 67 µM) and sulphamic acid (K_I of 6.2 µM) showed a rather efficient inhibitory action. There are currently very few non-toxic agents effective in combating this parasite. GsaCAβ is subsequently proposed as a new drug target for which effective inhibitors can be designed.

Carbon Dioxide Sensing by Immune Cells Occurs through Carbonic Anhydrase 2-Dependent Changes in Intracellular pH

CO₂, the primary gaseous product of respiration, is a major physiologic gas, the biology of which is poorly understood. Elevated CO₂ is a feature of the microenvironment in multiple inflammatory diseases that suppresses immune cell activity. However, little is known about the CO₂-sensing mechanisms and downstream pathways involved. We found that elevated CO₂ correlates with reduced monocyte and macrophage migration in patients undergoing gastrointestinal surgery and that elevated CO₂ reduces migration in vitro. Mechanistically, CO₂ reduces autocrine inflammatory gene expression, thereby inhibiting macrophage activation in a manner dependent on decreased intracellular pH. Pharmacologic or genetic inhibition of carbonic anhydrases (CAs) uncouples a CO₂-elicited intracellular pH response and attenuates CO₂ sensitivity in immune cells. Conversely, CRISPR-driven upregulation of the isoenzyme CA2 confers CO₂ sensitivity in nonimmune cells. Of interest, we found that patients with chronic lung diseases associated with elevated systemic CO₂ (hypercapnia) display a greater risk of developing anastomotic leakage following gastrointestinal surgery, indicating impaired wound healing. Furthermore, low intraoperative pH levels in these patients correlate with reduced intestinal macrophage infiltration. In conclusion, CO₂ is an immunomodulatory gas sensed by immune cells through a CA2-coupled change in intracellular pH.

Targeting carbonic anhydrase IX and XII isoforms with small molecule inhibitors and monoclonal antibodies

Carbonic anhydrases IX and CAXII (CAIX/CAXII) are transmembrane zinc metalloproteins that catalyze a very basic but crucial physiological reaction: the conversion of carbon dioxide into bicarbonate with a release of the proton. CA, especially CAIX and CAXII isoforms gained the attention of many researchers interested in anticancer drug design due to pivotal functions of enzymes in the cancer cell metastasis and response to hypoxia, and their expression restricted to malignant cells. This offers an opportunity to develop new targeted therapies with fewer side effects. Continuous efforts led to the discovery of a series of diverse compounds with the most abundant sulphonamide derivatives. Here we review current knowledge considering small molecule and antibody-based targeting of CAIX/CAXII in cancer.

Inhibition of carbonic anhydrases IX/XII by SLC-0111 boosts cisplatin effects in hampering head and neck squamous carcinoma cell growth and invasion

Background

Hypoxic tumor microenvironment (TME) contributes to the onset of many aspects of the cancer biology associated to the resistance to conventional therapies. Hypoxia is a common characteristic and negative prognostic factor in the head and neck squamous carcinomas (HNSCC) and is correlated with aggressive and invasive phenotype as well as with failure to chemo- and radio-therapies. The carbonic anhydrase isoenzymes IX and XII (CA IX/XII), regulators of extra and intracellular pH, are overexpressed in TME and are involved in adaptative changes occurring in cancer cells to survive at low O₂. In this study, we aim to investigate in HNSCC cells and murine models the possibility to target CA IX/XII by the specific inhibitor SLC-0111 to potentiate the effects of cisplatin in hampering cell growth, migration and invasion. Furthermore, we analyzed the signal pathways cooperating in acquisition of a more aggressive phenotype including stemness, epithelial-mesenchymal transition and apoptotic markers.

Methods

The effects of cisplatin, CA IX/XII specific inhibitor SLC-0111, and the combinatorial treatment were tested on proliferation, migration, invasion of HNSCC cells grown in 2D and 3D models. Main signal pathways and the expression of stemness, mesenchymal and apoptotic markers were analyzed by western blotting. Molecular imaging using NIR-Annexin V and NIR-Prosense was performed in HNSCC xenografts to detect tumor growth and metastatic spread.

Results

HNSCC cells grown in 2D and 3D models under hypoxic conditions showed increased levels of CA IX/XII and greater resistance to cisplatin than cells grown under normoxic conditions. The addition of CA IX/XII inhibitor SLC-0111 to cisplatin sensitized HNSCC cells to the chemotherapeutic agent and caused a reduction of proliferation, migration and invasiveness. Furthermore, the combination therapy hampered activation of STAT3, AKT, ERK, and EMT program, whereas it induced apoptosis. In HNSCC xenografts the treatment with cisplatin plus SLC-0111 caused an inhibition of tumor growth and an induction of apoptosis as well as a reduction of metastatic spread at a higher extent than single agents.

Conclusion

Our results highlight the ability of SLC-0111 to sensitize HNSCC to cisplatin by hindering hypoxia-induced signaling network that are shared among mechanisms involved in therapy resistance and metastasis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02345-x.

Contribution of the Mitochondrial Carbonic Anhydrase (MoCA1) to Conidiogenesis and Pathogenesis in Magnaporthe oryzae

The interconversion of CO₂ and HCO₃⁻ catalyzed by carbonic anhydrases (CAs) is a fundamental biochemical process in organisms. During mammalian–pathogen interaction, both host and pathogen CAs play vital roles in resistance and pathogenesis; during planta–pathogen interaction, however, plant CAs function in host resistance but whether pathogen CAs are involved in pathogenesis is unknown. Here, we biologically characterized the Magnaporthe oryzae CA (MoCA1). Through detecting the DsRED-tagged proteins, we observed the fusion MoCA1 in the mitochondria of M. oryzae. Together with the measurement of CA activity, we confirmed that MoCA1 is a mitochondrial zinc-binding CA. MoCA1 expression, upregulated with H₂O₂ or NaHCO₃ treatment, also showed a drastic upregulation during conidiogenesis and pathogenesis. When MoCA1 was deleted, the mutant ΔMoCA1 was defective in conidiophore development and pathogenicity. 3,3′-Diaminobenzidine (DAB) staining indicated that more H₂O₂ accumulated in ΔMoCA1; accordingly, ATPase genes were downregulated and ATP content decreased in ΔMoCA1. Summarily, our data proved the involvement of the mitochondrial MoCA1 in conidiogenesis and pathogenesis in the rice blast fungus. Considering the previously reported HCO₃⁻ transporter MoAE4, we propose that MoCA1 in cooperation with MoAE4 constitutes a HCO₃⁻ homeostasis-mediated disease pathway, in which MoCA1 and MoAE4 can be a drug target for disease control.

Synthesis, molecular modelling and QSAR study of new N-phenylacetamide-2-oxoindole benzensulfonamide conjugates as carbonic anhydrase inhibitors with antiproliferative activity

In continuation of our previous studies to optimise potent carbonic anhydrase inhibitors, two new series of isatin N-phenylacetamide based sulphonamides were synthesised and screened for their human (h) carbonic anhydrase (EC 4.2.1.1) inhibitory activities against four isoforms hCA I, hCA II, hCA IX and hCA XII. The indole-2,3-dione derivative 2h showed the most effective inhibition profile against hCAI and hCA II (K_I = 45.10, 5.87 nM) compared to acetazolamide (AAZ) as standard inhibitor. Moreover, 2h showed appreciable inhibition activity against the tumour-associated hCA XII, similar to AAZ showing K_I of 7.91 and 5.70 nM, respectively. The analogs 3c and 3d showed good cytotoxicity effects, and 3c revealed promising selectivity towards lung cell line A549. Molecular docking was carried out for 2h and 3c to predict their binding conformations and affinities towards the hCA I, II, IX and XII isoforms.

Efficient One-pot Synthesis of 3,3-di(indolyl)indolin-2-ones from Isatin and Indole Catalyzed by VOSO4 as Non-Sulfonamide Carbonic Anhydrase Inhibitors

Background A high yielding green protocol has been developed and delineated for the synthesis of 3,3-di(indolyl)indolin-2-ones, potentially bioactive compounds, involving one pot aqueous medium condensation of isatin with indole in the presence of VOSO4. The synthesized compounds were screened for their carbonic anhydrase inhibitory activity against human (h) isoforms hCA I, hCA II, hCA IX and hCA XII. These non-sulfonamide derivatives selectively inhibited hCA II in the micromolar range. Objective To develop a high yielding green protocol to synthesize 3,3-diindolyl oxindole derivatives using water as solvent media and screening of the synthesized molecules for their carbonic anhydrase inhibitory activity. Methods The target compound is obtained by taking isatin, indole, VOSO4and H2O in one-pot at 70 oC. Results The designed molecules were synthesized by using the new method. The molecules were screened for their CA inhibitory activity which shows selective inhibition toward hCA II.The result shown an excellent yield without any loss or decrease in catalytic activity, hence proved the performance and recyclability of the catalyst. Conclusion An efficient, simple and green protocol was established that provides a facile and straightforward approach for the preparation of 3,3-diindolyl oxindole derivatives (3a-r) from Isatin and Indole by using 10 mol % VOSO4 in high yields in a short period of time by a one-pot coupling reaction. Furthermore, the catalyst can also be recovered and reused for three consecutive catalytic cycle without any loss of its efficiency which was confirmed by performing the experiment with 3a. The newly synthesized molecules (3a-r) were screened for their carbonic anhydrase inhibition potency against four isoforms, hCA I, II, IX and XII and most of the compounds were found potent against hCA II with potency low to submicromolar range.

New Pyridinium Salt Derivatives of 2-(Hydrazinocarbonyl)-3-phenyl-1H-indole-5- sulfonamide as Selective Inhibitors of Tumour-Related Human Carbonic Anhydrase Isoforms IX and XII

BACKGROUND

The positively charged membrane impermeant sulfonamides were evaluated as a remarkable class of carbonic anhydrase inhibitors (CAIs) previously. Without affecting the human carbonic anhydrase (hCA), cytosolic isoforms hCA I and II, inhibition of two membrane-associated isoforms hCA IX and XII especially overexpressed in hypoxic tumour cells, makes the pyridinium salt derivatives potent promising therapeutic agents.

OBJECTIVE

A novel series of tri, tetra, and cyclo-substituted pyridinium salt derivatives of the lead compound 2- (hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide has been prepared by using sixteen different pyrylium salts, for the search of selective inhibitors of transmembrane tumour-associated human carbonic anhydrase hCA IX and XII.

METHODS

Molecular modeling studies were carried out to understand and rationalize the in vitro enzyme inhibition data.

RESULTS

Six of the new compounds showed good inhibitory profiles with low nanomolar range (< 100 nM) against hCA IX/XII, and compound 5 showed excellent potency with Ki values lower than 10 nM. In addition, molecular modelling studies have presented the possible binding modes of the ligands.

CONCLUSION

Most of the compounds displayed potent inhibitory activity against the tumor-associated hCA IX and XII in the low nanomolar range and selectivity over the off-targeted isoforms hCA I and II. Due to their cationic structure and membrane-impermeant behavior, it is also expected to maximize the selectivity over cytosolic isoforms hCA I/II while inhibiting tumor overexpressed isoforms hCA XI/XII of new compounds in in vivo conditions.

Aromatic Sulfonamides including a Sulfonic Acid Tail: New Membrane Impermeant Carbonic Anhydrase Inhibitors for Targeting Selectively the Cancer-Associated Isoforms

We report here a new drug design strategy for producing membrane-impermeant carbonic anhydrase (CA; EC 4.2.1.1) inhibitors selectively targeting the tumor-associated, membrane-bound human CAs IX and XII over off-target cytosolic isoforms. To date, this approach has only been pursued by including permanent positively charged pyridinium type or highly hydrophilic glycosidic moieties into the structure of aromatic sulfonamide CA inhibitors (CAIs). Aliphatic (propyl and butyl) sulfonic acid tails, deprotonated at physiological pH, were thus incorporated onto a benzenesulfonamide scaffold by a common 1,2,3-triazole linker and different types of spacers. Twenty such derivatives were synthesized and tested for their inhibition of target (hCAs IV, IX, and XII) and off-target CAs (hCAs I and II). Most sulfonate CAIs induced a potent inhibition of hCAs II, IX, and XII up to a low nanomolar K_I range (0.9–459.4 nM) with a limited target/off-target CA selectivity of action. According to the drug design schedule, a subset of representative derivatives was assessed for their cell membrane permeability using Caco-2 cells and a developed FIA-MS/MS method. The complete membrane impermeability of the sulfonate tailed CAIs (≥98%) validated these negatively charged moieties as being suitable for achieving, in vivo, the selective targeting of the tumor-associated CAs over off-target ones.

Synthesis, carbonic anhydrase enzyme inhibition evaluations, and anticancer studies of sulfonamide based thiadiazole derivatives

The sulfonamide-based thiadiazole derivatives (STDs) with different hydrophobic/hydrophilic substitutions were synthesized to investigate their potentials in carbonic anhydrase inhibition (CAI). The CAI activity of the STDs (4a-4h) and the mechanism of the inhibition kinetics were determined. STD 4f contained both methoxy and Cl groups at benzene ring in STD 4f showed the lowest IC₅₀ value. The molecular docking study confirmed that STDs bind strongly with the active sites of the target protein PDBID 1V9E. With the help of Lineweaver-Burk plots, inhibition kinetics of PDBIR 1V9E protein with STDs were determined. Cytotoxicity was checked against human keratinocyte cell lines and the anticancer properties were determined against MCF-7 cell lines. The electrochemical method was used to investigate the binding study with DNA and CA enzymes. Anticancer studies showed that STDs have weak bonding ability to DNA and strong binding ability with CA. It is concluded that anticancer activity is through CAI rather than by DNA binding.

Binding site comparison for coumarin inhibitors and amine/amino acid activators of human carbonic anhydrases

The first structural analysis comparing the binding mode to the target carbonic anhydrases (CAs, EC 4.2.1.1) of two opposite classes of modulators is presented here: coumarin derivatives act as prodrug CA inhibitors (CAIs), being hydrolyzed by the enzyme esterase activity to 2-hydroxycinnamic acids that occlude the active site entrance; CA activators (CAAs) belonging of the amine and amino acid types, enhance the CA activity by increasing the efficiency of the rate-determining proton shuttling step in the CA catalytic cycle. Analysis of the crystallographic data available for the human CA isoform II in adduct with two coumarin CAIs and some CAAs showed that both types of CA modulators bind in the same region of the enzyme active site, basically interacting with superimposable amino acid residues, that are Trp5, Asn62, His64, Asn67, Gln92, Thr200. A plethora of water molecules also participate in the adducts formation. This structural analysis showed that presence of certain chemical groups in the compound structure is mandatory to produce an activating rather than inhibitory action, such as multiple nitrogen- and oxygen-based moieties capable of shuttling protons or forming extended H-bond networks nearby the proton shuttle residue. This constitutes the only known example among all enzymes of an identical binding site for inhibitors and activators, which, in addition, possess significant pharmacological applications.

Carbonic Anhydrase IX Inhibitors as Candidates for Combination Therapy of Solid Tumors

Combination therapy is becoming imperative for the treatment of many cancers, as it provides a higher chance of avoiding drug resistance and tumor recurrence. Among the resistance-conferring factors, the tumor microenvironment plays a major role, and therefore, represents a viable target for adjuvant therapeutic agents. Thus, hypoxia and extracellular acidosis are known to select for the most aggressive and resilient phenotypes and build poorly responsive regions of the tumor mass. Carbonic anhydrase (CA, EC 4.2.1.1) IX isoform is a surficial zinc metalloenzyme that is proven to play a central role in regulating intra and extracellular pH, as well as modulating invasion and metastasis processes. With its strong association and distribution in various tumor tissues and well-known druggability, this protein holds great promise as a target to pharmacologically interfere with the tumor microenvironment by using drug combination regimens. In the present review, we summarized recent publications revealing the potential of CA IX inhibitors to intensify cancer chemotherapy and overcome drug resistance in preclinical settings.

Carbonic anhydrase inhibitors: an update on experimental agents for the treatment and imaging of hypoxic tumors

INTRODUCTION

Hypoxic tumors, unlike normal tissues, overexpress proteins involved in oxygen sensing, metabolism, pH regulation, angiogenesis, immunological response, and other survival mechanisms, which are under investigation as antitumor drug targets.

AREAS COVERED

Carbonic anhydrase (CA) isoforms CA IX and XII are among these validated antitumor/antimetastatic drug targets, with several of their inhibitors undergoing preclinical or clinical-stage investigations. Alone or in combination with other chemotherapeutic agents or radiotherapy, CA IX/XII inhibitors, such as SLC-0111, SLC-149, S4, 6A10, etc., were shown to inhibit the growth of the primary tumor, metastases, and invasiveness of many tumor types, being also amenable for the development of imaging agents.

EXPERT OPINION

SLC-0111 is the most investigated agent, being in Phase Ib/II clinical trials. In addition to its interference with extracellular acidifications, it has been shown to promote ferroptosis in cancer cells, another antitumor mechanism of this compound and the entire class. A large number sulfonamide and non-sulfonamide inhibitors have been developed using SLC-0111 as lead in the last three years, together with hybrid agents incorporating CA inhibitors and other anticancer chemotypes, including cytotoxins, telomerase, thioredoxin or P-glycoprotein inhibitors, adenosine A₂A receptor antagonists, pyrophosphatase/phosphodiesterase-3 inhibitors or antimetabolites. All of them showed significant antitumor activity.

Natural inspired piperine-based sulfonamides and carboxylic acids as carbonic anhydrase inhibitors: Design, synthesis and biological evaluation

The natural product piperine, the major bioactive alkaloid present in black pepper fruits, has the ability to modulate the functional activity of several biological targets. In this study, we have utilized the natural piperine as a tail moiety to develop new SLC-0111 analogues (6a-d, 8 and 9) as potential carbonic anhydrase inhibitors. Thereafter, different functionalities, free carboxylic acid (11a-c), acetyl (13a) and ethyl ester (13b-c), were exploited as bioisosteres of the sulfamoyl functionality. All piperine-based derivatives were assessed for their inhibitory actions against four human (h) CA isoforms: hCA I, II, IX and XII. The best hCA inhibitory activity was observed for the synthesized primary piperine-sulfonamides (6a-d and 8). In particular, both para-regioisomers (6c and 8) emerged as the most potent hCA inhibitors in this study with two-digit nanomolar activity against hCA II (K_Is = 93.4 and 88.6 nM, respectively), hCA IX (K_Is = 38.7 and 68.2 nM, respectively), and hCA XII (K_Is = 57.5 and 45.6 nM, respectively). Moreover, piperine-sulfonamide 6c was examined for its anti-cancer and pro-apoptotic actions towards breast MCF-7 cancer cell line. Collectively, piperine-based sulfonamides could be considered as a promising scaffold for development of efficient anticancer candidates with potent CA inhibitory activities.

Activation of carbonic anhydrase isoforms involved in modulation of emotional memory and cognitive disorders with histamine agonists, antagonists and derivatives

Carbonic anhydrases (CAs, EC 4.2.1.1) activators were shown to be involved in memory enhancement and learning in animal models of cognition. Here we investigated the CA activating effects of a large series of histamine based compounds, including histamine receptors (H1R - H4R) agonists, antagonists and other derivatives of this autacoid. CA activators may be thus useful for improving cognition as well as in diverse therapeutic areas (phobias, obsessive-compulsive disorder, generalised anxiety, post-traumatic stress disorders), for which activation of this enzyme was recently shown to be involved.

Isolation and characterization of monoclonal antibodies against human carbonic anhydrase-IX

The architectural complexity and heterogeneity of the tumor microenvironment (TME) remains a substantial obstacle in the successful treatment of cancer. Hypoxia, caused by insufficient oxygen supply, and acidosis, resulting from the expulsion of acidic metabolites, are prominent features of the TME. To mitigate the consequences of the hostile TME, cancer cells metabolically rewire themselves and express a series of specific transporters and enzymes instrumental to this adaptation. One of these proteins is carbonic anhydrase (CA)IX, a zinc-containing extracellular membrane bound enzyme that has been shown to play a critical role in the maintenance of a neutral intracellular pH (pH_i), allowing tumor cells to survive and thrive in these harsh conditions. Although CAIX has been considered a promising cancer target, only two antibody-based therapeutics have been clinically tested so far. To fill this gap, we generated a series of novel monoclonal antibodies (mAbs) that specifically recognize the extracellular domain (ECD) of human CAIX. Here we describe the biophysical and functional properties of a set of antibodies against the CAIX ECD domain and their applicability as: 1) suitable for development as an antibody-drug-conjugate, 2) an inhibitor of CAIX enzyme activity, or 3) an imaging/detection antibody. The results presented here demonstrate the potential of these specific hCAIX mAbs for further development as novel cancer therapeutic and/or diagnostic tools.

Carbonic Anhydrase Inhibition with Sulfonamides Incorporating Pyrazole- and Pyridazinecarboxamide Moieties Provides Examples of Isoform-Selective Inhibitors

A series of benzenesulfonamides incorporating pyrazole- and pyridazinecarboxamides decorated with several bulky moieties has been obtained by original procedures. The new derivatives were investigated for the inhibition of four physiologically crucial human carbonic anhydrase (hCA, EC 4.2.2.1.1) isoforms, hCA I and II (cytosolic enzymes) as well as hCA IX and XII (transmembrane, tumor-associated isoforms). Examples of isoform-selective inhibitors were obtained for all four enzymes investigated here, and a computational approach was employed for explaining the observed selectivity, which may be useful in drug design approaches for obtaining inhibitors with pharmacological applications useful as antiglaucoma, diuretic, antitumor or anti-cerebral ischemia drugs.

Transcriptome profiling reveals differential gene expression in the rumen of Hu lambs at different developmental stages

The development of the rumen is a critical physiological challenge in newborn ruminants. However, the molecular mechanism underlying different stages of rumen development in sheep remains poorly understood. Here, RNA sequencing and bioinformatics analysis were performed to compare the transcription profiles of rumen development at 7, 28 and 56 days of birth (D7, D28 and D56). We identified 1246, 2257 and 627 differentially expressed genes (DEGs) between D7 and D28, between D7 and D56, between D28 and D56, respectively. Also, 70 DGEs were co-expressed at these three time points. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses indicated most DEGs mainly related to transporter activity, channel activity and metabolism pathways. Noteworthy, the expression levels of most genes (CA4, CA9, CA12 and CA14) in nitrogen metabolic pathways were negatively correlated with the papilla length and width, but the papilla length and width were positively correlated with the expression of genes (PLA2G3, SLC26A9, SLC34A3) in ion transport pathway, suggesting that these genes may be involved in nitrogen metabolic and ion transport pathway and thus affect rumen development. These results provide new insight into the changes in RNA expression at different time points of rumen development in Hu sheep.

Synthesis, Crystal Structure, Inhibitory Activity and Molecular Docking of Coumarins/Sulfonamides Containing Triazolyl Pyridine Moiety as Potent Selective Carbonic Anhydrase IX and XII Inhibitors

In this work, two classes of Carbonic Anhydrase (CA) inhibitors, sulfonamide and coumarin derivatives linked to pyta moiety (2a-b) and their corresponding rhenium complexes (3a-b), were designed. These compounds were synthesized and fully characterized by classical analytical methods and X-ray diffraction. All the synthesized compounds were evaluated for their inhibitory activity against the hCA isoforms I, II, IX and XII. They exhibited high inhibitory activities in the range of nanomolar for both hCA IX and hCA XII isoforms. The sulfonamide compound 2a showed the strongest inhibition against the tumour-associated hCA IX isoform with a Ki of 11.7 nM. The tumour-associated isoforms hCA IX and hCA XII were selectively inhibited by all the coumarin derivatives, with inhibition constants ranging from 12.7 nM (2b) to 44.5 nM (3b), while the hCA I and II isoforms were slightly inhibited (in the micromolar range), as expected. In terms of selectivity, compared to previously published rhenium complex-based CA inhibitors, complex 3b showed one of the highest selectivities against hCA IX and hCA XII compared to the off-target isoforms hCA I and hCA II, making it a potential anti-cancer drug candidate. Molecular docking calculations were performed to investigate the inhibition profiles of the investigated compounds at the tumour-associated hCA IX active site and to rationalize our results.

Synthesis, antiproliferative and antitrypanosomal activities, and DNA binding of novel 6-amidino-2-arylbenzothiazoles

A series of 6-amidinobenzothiazoles, linked via phenoxymethylene or directly to the 1,2,3-triazole ring with a p-substituted phenyl or benzyl moiety, were synthesised and evaluated in vitro against four human tumour cell lines and the protozoan parasite Trypanosoma brucei. The influence of the type of amidino substituent and phenoxymethylene linker on antiproliferative and antitrypanosomal activities was observed, showing that the imidazoline moiety had a major impact on both activities. Benzothiazole imidazoline 14a, which was directly connected to N-1-phenyl-1,2,3-triazole, had the most potent growth-inhibitory effect (IC₅₀ = 0.25 µM) on colorectal adenocarcinoma (SW620), while benzothiazole imidazoline 11b, containing a phenoxymethylene linker, exhibited the best antitrypanosomal potency (IC₉₀ = 0.12 µM). DNA binding assays showed a non-covalent interaction of 6-amidinobenzothiazole ligands, indicating both minor groove binding and intercalation modes of DNA interaction. Our findings encourage further development of novel structurally related 6-amidino-2-arylbenzothiazoles to obtain more selective anticancer and anti-HAT agents.

New Sulfanilamide Derivatives Incorporating Heterocyclic Carboxamide Moieties as Carbonic Anhydrase Inhibitors

Carbonic Anhydrases (CAs) are ubiquitous metalloenzymes involved in several disease conditions. There are 15 human CA (hCA) isoforms and their high homology represents a challenge for the discovery of potential drugs devoid of off-target side effects. For this reason, many synthetic and pharmacologic research efforts are underway to achieve the full pharmacological potential of CA modulators of activity. We report here a novel series of sulfanilamide derivatives containing heterocyclic carboxamide moieties which were evaluated as CA inhibitors against the physiological relevant isoforms hCA I, II, IX, and XII. Some of them showed selectivity toward isoform hCA II and hCA XII. Molecular docking was performed for some of these compounds on isoforms hCA II and XII to understand the possible interaction with the active site amino acid residues, which rationalized the reported inhibitory activity.

Anti-breast cancer action of carbonic anhydrase IX inhibitor 4-[4-(4-Benzo[1,3]dioxol-5-ylmethyl-piperazin-1-yl)-benzylidene-hydrazinocarbonyl]-benzenesulfonamide (BSM-0004): in vitro and in vivo studies

Anti-breast cancer action of novel human carbonic anhydrase IX (hCA IX) inhibitor BSM-0004 has been investigated using in vitro and in vivo models of breast cancer. BSM-0004 was found to be a potent and selective hCA IX inhibitor with a Ki value of 96 nM. In vitro anticancer effect of BSM-0004 was analysed against MCF 7 and MDA-MA-231 cells, BSM-0004 exerted an effective cytotoxic effect under normoxic and hypoxic conditions, inducing apoptosis in MCF 7 cells. Additionally, this compound significantly regulates the expression of crucial biomarkers associated with apoptosis. The investigation was extended to confirm the efficacy of this hCA IX inhibitor against in vivo model of breast cancer. The results specified that the treatment of BSM-0004 displayed an effective in vivo anticancer effect, reducing tumour growth in a xenograft cancer model. Hence, our investigation delivers an effective anti-breast cancer agent that engenders the anticancer effect by inhibiting hCA IX.

Multitargeting approaches involving carbonic anhydrase inhibitors: hybrid drugs against a variety of disorders

Carbonic anhydrases (CAs, EC 4.2.1.1) are enzymes involved in a multitude of diseases, and their inhibitors are in clinical use as drugs for the management of glaucoma, epilepsy, obesity, and tumours. In the last decade, multitargeting approaches have been proposed by hybridisation of CA inhibitors (CAIs) of sulphonamide, coumarin, and sulphocoumarin types with NO donors, CO donors, prostaglandin analogs, β-adrenergic blockers, non-steroidal anti-inflammatory drugs, and a variety of anticancer agents (cytotoxic drugs, kinase/telomerase inhibitors, P-gp and thioredoxin inhibitors). Many of the obtained hybrids showed enhanced efficacy compared to the parent drugs, making multitargeting an effective and innovative approach for various pharmacological applications.

Can Targeting Hypoxia-Mediated Acidification of the Bone Marrow Microenvironment Kill Myeloma Tumor Cells?

Multiple myeloma (MM) is an incurable cancer arising from malignant plasma cells that engraft in the bone marrow (BM). The physiology of these cancer cells within the BM microenvironment (TME) plays a critical role in MM development. These processes may be similar to what has been observed in the TME of other (non-hematological) solid tumors. It has been long reported that within the BM, vascular endothelial growth factor (VEGF), increased angiogenesis and microvessel density, and activation of hypoxia-induced transcription factors (HIF) are correlated with MM progression but despite a great deal of effort and some modest preclinical success the overall clinical efficacy of using anti-angiogenic and hypoxia-targeting strategies, has been limited. This review will explore the hypothesis that the TME of MM engrafted in the BM is distinctly different from non-hematological-derived solid tumors calling into question how effective these strategies may be against MM. We further identify other hypoxia-mediated effectors, such as hypoxia-mediated acidification of the TME, oxygen-dependent metabolic changes, and the generation of reactive oxygen species (ROS), that may prove to be more effective targets against MM.

Synthesis and Human Carbonic Anhydrase I, II, IX, and XII Inhibition Studies of Sulphonamides Incorporating Mono-, Bi- and Tricyclic Imide Moieties

New derivatives were synthesised by reaction of amino-containing aromatic sulphonamides with mono-, bi-, and tricyclic anhydrides. These sulphonamides were investigated as human carbonic anhydrases (hCAs, EC 4.2.1.1) I, II, IX, and XII inhibitors. hCA I was inhibited with inhibition constants (Kis) ranging from 49 to >10,000 nM. The physiologically dominant hCA II was significantly inhibited by most of the sulphonamide with the Kis ranging between 2.4 and 4515 nM. hCA IX and hCA XII were inhibited by these sulphonamides in the range of 9.7 to 7766 nM and 14 to 316 nM, respectively. The structure-activity relationships (SAR) are rationalised with the help of molecular docking studies.

Design, synthesis, and evaluation of novel coumarin-dithiocarbamate derivatives (IDs) as anti-colorectal cancer agents

Colorectal cancer (CRC) is a common malignant tumour of human digestive tract. The high mortality rate of CRC is closely related to the limitations of existing treatments. Thus, there is an urgent need to search for new anti-CRC agents. In this work, twenty novel coumarin-dithiocarbamate derivatives (IDs) were designed, synthesized and evaluated in vitro. The results suggest that the most active compound ID-11 effectively inhibited the proliferation of CRC cell lines while shown little impact on normal colon epithelial cells. Mechanism studies revealed that ID-11 displayed bromodomain-containing protein 4 inhibitory activity, and induced G2/M phase arrest, apoptosis as well as decreased the expression levels of the key genes such as c-Myc and Bcl-2 in CRC cell lines. Moreover, the ADMET properties prediction results shown that ID-11 possess well metabolic characteristics without obvious toxicities. Our data demonstrated that compound ID-11 may be a promising anti-CRC agent and deserved for further development.

Investigation of 3-sulfamoyl coumarins against cancer-related IX and XII isoforms of human carbonic anhydrase as well as cancer cells leads to the discovery of 2-oxo-2H-benzo[h]chromene-3-sulfonamide - A new caspase-activating proapoptotic agent

Herein we report the synthesis of a set of seventeen 3-sulfonamide substituted coumarin derivatives. Prepared compounds were tested in vitro for inhibition of four physiologically relevant isoforms of the metalloenzyme human carbonic anhydrase (hCA, EC 4.2.1.1). Several coumarin sulfonamides displayed low nanomolar K_I values against therapeutically relevant hCA II, IX, and XII, whereas they did not potently inhibit hCA I. Some of these compounds exerted a concentration-dependent antiproliferative action toward RT4 human bladder cancer and especially A431 human epidermoid carcinoma cell lines. In the meantime, the viability of non-tumorigenic hTERT immortalized human foreskin fibroblast cell line Bj-5ta was not significantly affected by the obtained derivatives. Interestingly, compound 10q (2-oxo-2H-benzo [h]chromene-3-sulfonamide) showed a profound and selective dose-dependent inhibition of A431 cell growth with low nanomolar IC₅₀ values. We demonstrated that 10q possessed a concentration-dependent apoptosis induction activity associated with caspase 3/7 activation in cancer cells. As carbonic anhydrase isoforms in question were not potently inhibited by this compound, its antiproliferative effects likely involve other mechanisms, such as DNA intercalation. Compound 10q clearly represents a viable lead for further development of new-generation anticancer agents.

The Carbonic Anhydrase Inhibitor E7070 Sensitizes Glioblastoma Cells to Radio- and Chemotherapy and Reduces Tumor Growth

Glioblastomas (GBMs), the most common and lethal primary brain tumor, show inherent infiltrative nature and high molecular heterogeneity that make complete surgical resection unfeasible and unresponsive to conventional adjuvant therapy. Due to their fast growth rate even under hypoxic and acidic conditions, GBM cells can conserve the intracellular pH at physiological range by overexpressing membrane-bound carbonic anhydrases (CAs). The synthetic sulfonamide E7070 is a potent inhibitor of CAs that harbors putative anticancer properties; however, this drug has still not been tested in GBMs. The present study aimed to evaluate the effects of E7070 on CA9 and CA12 enzymes in GBM cells as well as in the tumor cell growth, migration, invasion, and resistance to radiotherapy and chemotherapy. We found that E7070 treatment significantly reduced tumor cell growth and increased radio- and chemotherapy efficacy against GBM cells under hypoxia. Our data suggests that E7070 has therapeutic potential as a radio-chemo-sensitizing in drug-resistant GBMs, representing an attractive strategy to improve the adjuvant therapy. We showed that CA9 and CA12 represent potentially valuable therapeutic targets that should be further investigated as useful diagnostic and prognostic biomarkers for GBM tailored therapy.

Targeting of carbonic anhydrase IX-positive cancer cells by glycine-coated superparamagnetic nanoparticles

Antibody-modified magnetic nanoparticles were prepared to study their cellular uptake in 3D multicellular spheroidal cell cultures. For this purpose, carbonic anhydrase IX specific monoclonal antibody VII/20 was selected to conjugate on the surface of positively charged glycine coated magnetic nanoparticles in a form of a stable magnetic fluid. In this work, glycine-functionalized magnetic nanoparticles were characterized by different methods. X-ray photoelectron analysis confirmed the binding of glycine to the magnetic nanoparticles, and quantification of the glycine coating on the surface of the magnetic nanoparticles was conducted by thermogravimetric analysis. The optimal weight ratio of glycine to magnetic nanoparticles was determined to be 5 showing good colloid stability due to the high surface charge density of protonated glycine coating shown by the great zeta potential (⁓40 mV). The antibody conjugation to the functionalized magnetic nanoparticles was performed at an antibody to magnetic nanoparticles weight ratio equal to 0.5. Applications of antibody-modified magnetic nanoparticles in cancer therapy rely on their ability to specifically target cancer tissues and enter the tumour intracellular space. Here, we show that antibody coupled nanoparticle internalization was triggered by selective binding to tumour cells expressing hypoxic marker carbonic anhydrase IX. Moreover, our results confirmed specific penetration of conjugated nanoparticles into the tumour cell spheroids.

Tellurides bearing benzensulfonamide as carbonic anhydrase inhibitors with potent antitumor activity

We evaluated in vitro a series of telluride containing compounds bearing the benzenesulfonamide group, as effective inhibitors of the physiologically relevant human (h) expressed Carbonic Anhydrase (CA; EC 4.2.1.1) enzymes I, II, IV VII and IX. The potent effects of such compounds against the tumor-associated hCA IX being low nanomolar inhibitors (K_I 2.2 to 2.9 nM) and with good selectivity over the ubiquitous hCA II, gave the possibility to evaluate their lethal effect in vitro against a breast cancer cell line (MDA-MB-231). Among the series, both compounds 3a and 3g induced significant toxic effects against tumor cells after 48 h incubation. Under normoxic condition 3a showed high efficacy killing over 94% of tumor cells at 1 µM, and derivative 3g reached the tumor cell viability under the 5% at 10 µM. In hypoxic condition, these two compounds showed less effective although retained excellent cancer cell killer. These unusual features make them interesting lead compounds acting as antitumor agents also in tumor types not dependent from hCA IX overexpression.

Advances in the discovery of novel agents for the treatment of glaucoma

INTRODUCTION

Glaucoma, a neuropathy characterized by increased intraocular pressure (IOP), is the major cause of blindness worldwide and its treatment aims at reducing IOP.

AREAS COVERED

The authors review the design of the main classes of anti-glaucoma agents. Drugs which interfere with the aqueous humor secretion (adrenergic agonists/antagonists, carbonic anhydrase inhibitors) and with its outflow, by means of both conventional and non-conventional pathways (prostaglandin (PG) analogs, rho kinase inhibitors, nitric oxide (NO) donors) as well as new agents (adenosine receptors modulators, melatonin - fatty acid amide hydrolase hybrids, tyrosine kinase activators, natriuretic peptide analogs) are considered.

EXPERT OPINION

The anti-glaucoma drug field has undergone several developments in recent years with the approval of at least three new drugs belonging to novel pharmacological classes, the rho kinase inhibitors ripasudil and netarsudil, and the PG-NO donor hybrid latanoprostene bunod. Eye drops with combinations of two different drugs are also available, allowing for effective IOP control, with once daily administration for some of them, which assures a better patient compliance and ease of administration. Overall, after more than a decade without new anti-glaucoma drugs, the last year afforded interesting new pharmacological opportunities for the management of this disease.

Deciphering the key heterocyclic scaffolds in targeting microtubules, kinases and carbonic anhydrases for cancer drug development

Heterocyclic scaffolds are widely utilized for drug design by taking into account the molecular structure of therapeutic targets that are related to a broad spectrum of ailments, including tumors. Such compounds display various covalent and non-covalent interactions with the specific residues of the target proteins while causing their inhibition. There is a substantial number of heterocyclic compounds approved for cancer treatment, and these compounds function by interacting with different therapeutic targets involved in tumorogenesis. In this review, we trace and emphasize the privileged heterocyclic pharmacophores that have immense potency against several essential chemotherapeutic tumor targets: microtubules, kinases and carbonic anhydrases. Potent compounds currently undergoing pre-clinical and clinical studies have also been assessed for ascertaining the effective class of chemical scaffolds that have significant therapeutic potential against multiple malignancies. In addition, we also describe briefly the role of heterocyclic compounds in various chemotherapy regimens. The optimized molecular hybridization of delineated motifs may result in the discovery of more active anticancer therapeutics and circumvent the development of resistance by specific targets in the future.

Coumarin carbonic anhydrase inhibitors from natural sources

Coumarins constitute a relatively new class of inhibitors of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), possessing a unique inhibition mechanism, acting as "prodrug inhibitors." They undergo the hydrolysis of the lactone ring mediated by the esterase activity of CA. The formed 2-hydroxy-cinnamic acids thereafter bind within a very particular part of the enzyme active site, at its entrance, where a high variability of amino acid residues among the different mammalian CA isoforms is present, and where other inhibitors classes were not seen bound earlier. This explains why coumarins are among the most isoform-selective CA inhibitors known to date among the many chemotypes endowed with such biological activity. As coumarins are widespread secondary metabolites in some bacteria, plants, fungi, and ascidians, many such compounds from various natural sources have been investigated for their CA inhibitory properties and for possible biomedical applications, mainly as anticancer agents targeting hypoxic tumours.

Insertion of metal carbenes into the anilinic N-H bond of unprotected aminobenzenesulfonamides delivers low nanomolar inhibitors of human carbonic anhydrase IX and XII isoforms

Herein we report the synthesis of a set of thirty-four primary sulfonamides generated via formal N-H-insertion of metal carbenes into anilinic amino group of sulfanilamide and its meta-substituted analog. Obtained compounds were tested in vitro as inhibitors of four physiologically significant isoforms of the metalloenzyme human carbonic anhydrase (hCA, EC 4.2.1.1). Many of the synthesized sulfonamides displayed low nanomolar K_i values against therapeutically relevant hCA II, IX, and XII, whereas they did not potently inhibit hCA I. Provided the promising activity profiles of the substances towards tumor-associated hCA IX and XII isozymes, single-concentration MTT test was performed for the entire set. Disappointingly, most of the discovered hCA inhibitors did not significantly suppress the growth of cancer cells either in normoxia or CoCl₂ induced hypoxic conditions. The only two compounds exerting profound antiproliferative effect turned out to be modest hCA inhibitors. Their out of the range activity in cells is likely attributive to the presence of Michael acceptor substructure which can potentially act either through the inhibition of Thioredoxin reductases (TrxRs, EC 1.8.1.9) or nonspecific covalent binding to cell proteins.

Adaptive Mechanisms of Tumor Therapy Resistance Driven by Tumor Microenvironment

Cancer is a disease which frequently has a poor prognosis. Although multiple therapeutic strategies have been developed for various cancers, including chemotherapy, radiotherapy, and immunotherapy, resistance to these treatments frequently impedes the clinical outcomes. Besides the active resistance driven by genetic and epigenetic alterations in tumor cells, the tumor microenvironment (TME) has also been reported to be a crucial regulator in tumorigenesis, progression, and resistance. Here, we propose that the adaptive mechanisms of tumor resistance are closely connected with the TME rather than depending on non-cell-autonomous changes in response to clinical treatment. Although the comprehensive understanding of adaptive mechanisms driven by the TME need further investigation to fully elucidate the mechanisms of tumor therapeutic resistance, many clinical treatments targeting the TME have been successful. In this review, we report on recent advances concerning the molecular events and important factors involved in the TME, particularly focusing on the contributions of the TME to adaptive resistance, and provide insights into potential therapeutic methods or translational medicine targeting the TME to overcome resistance to therapy in clinical treatment.

Quinoline-sulfamoyl carbamates/sulfamide derivatives: Synthesis, cytotoxicity, carbonic anhydrase activity, and molecular modelling studies

Carbonic anhydrase (CA) IX, and XII isoforms are known to be highly expressed in various human tissues and malignancies. CA IX is a prominent target for some cancers because it is overexpressed in hypoxic tumors and this overexpression leads to poor prognosis. Novel twenty-seven compounds in two series (sulfamoylcarbamate-based quinoline (2a-2o) and sulfamide-based quinoline (3a-3l)) were synthesized and characterized by means of IR, NMR, and mass spectra. Their inhibitory activities were evaluated against CA I, CA II, CA IX, and CA XII isoforms. 2-Phenylpropyl (N-(quinolin-8-yl)sulfamoyl)carbamate (2m) exhibited the highest hCA IX inhibition with the K_i of 0.5 µM. In addition, cytotoxic effects of the synthesized compounds on human colorectal adenocarcinoma (HT-29; HTB-38), human breast adenocarcinoma (MCF7; HTB-22), human prostate adenocarcinoma (PC3; CRL-1435) and human healthy skin fibroblast (CCD-986Sk; CRL-1947) cell lines were examined. The cytotoxicity results showed that 2j, 3a, 3e, 3f are most active compounds in all cell lines (HT-29, MCF7, PC3, and CCD-986Sk).

Development of novel benzofuran-based SLC-0111 analogs as selective cancer-associated carbonic anhydrase isoform IX inhibitors

In the present study, we describe the design of different series of benzofuran-based derivatives as potential carbonic anhydrase inhibitors (CAIs). The adopted design is based on bioisosteric replacement for the p-fluorophenyl SLC-0111 tail with the lipophilic 2-methylbenzofuran or 5-bromobenzofuran tails to furnish the 2-methylbenzofuran (MBF) sulfonamides (MBFS; 9, 11 and 13) and 5-bromobenzofuran (BBF) sulfonamides (BBFS; 27a-b, 28a-b and 29a-c), respectively. Thereafter, the urea spacer was either elongated to furnish MBFS (17 and 19), and BBFS (30) series, or replaced by a carbamate one to afford MBFS (15). All the designed compounds were synthesized and evaluated for their inhibitory activities against four human (h) CA isoforms: hCA I, II, IX and XII. MBFS (11b and 17) and BBFS (28b, 29a and 30) efficiently inhibited the tumor-related CA IX isoform in the single-digit nanomolar range (K_Is = 8.4, 7.6, 5.5, 7.1 and 1.8 nM, respectively). In particular, MBFS 11b and BBFS 28b exhibited good selectivity toward hCA IX isoform over the main off-target hCA II isoform (S.I. = 26.4 and 58.9, respectively). As a consequence, 11b and 28b were examined for their anticancer and pro-apoptotic activities toward MDA-MB-231 and MCF-7 cancer cell lines.

Hypoxia and its therapeutic possibilities in paediatric cancers

In tumours, hypoxia-a condition in which the demand for oxygen is higher than its availability-is well known to be associated with reduced sensitivity to radiotherapy and chemotherapy, and with immunosuppression. The consequences of hypoxia on tumour biology and patient outcomes have therefore led to the investigation of strategies that can alleviate hypoxia in cancer cells, with the aim of sensitising cells to treatments. An alternative therapeutic approach involves the design of prodrugs that are activated by hypoxic cells. Increasing evidence indicates that hypoxia is not just clinically significant in adult cancers but also in paediatric cancers. We evaluate relevant methods to assess the levels and extent of hypoxia in childhood cancers, including novel imaging strategies such as oxygen-enhanced magnetic resonance imaging (MRI). Preclinical and clinical evidence largely supports the use of hypoxia-targeting drugs in children, and we describe the critical need to identify robust predictive biomarkers for the use of such drugs in future paediatric clinical trials. Ultimately, a more personalised approach to treatment that includes targeting hypoxic tumour cells might improve outcomes in subgroups of paediatric cancer patients.

The Carbonic Anhydrase IX inhibitor SLC-0111 as emerging agent against the mesenchymal stem cell-derived pro-survival effects on melanoma cells

Mesenchymal stem cells (MSC) take part to solid tumour-associated stroma and critically influence progression of malignancy. Our study represents a striking example of melanoma progression to a more malignant and resistant phenotype promoted by MSC and the possibility to contrast this diabolic liaison using CAIX inhibitors. In particular, we demonstrated that melanoma cells exposed to a MSC-conditioned medium switch to a more malignant phenotype, characterised by resistance to programmed cell death and endowed with an epithelial-to-mesenchymal transition and stem cell characteristics. These effects were reversed abrogating MSC CAIX activity using SLC-0111, a CAIX inhibitor. Moreover, the acquisition by melanoma cells of a Vemurafenib-resistant phenotype upon MSC-conditioned medium exposure was removed when MSC were treated with SLC-0111. Therefore, MSC may profoundly reprogramme melanoma cells towards a wide resistant phenotype through CAIX involvement, as the use of SLC-0111 is able to contrast the development of this highly risky adaptation for disease progression.

Prognostic value of CAIX expression in oral squamous cell carcinoma: a systematic review and meta-analysis

Carbonic anhydrase IX (CAIX) is a hypoxia-related protein considered as a predictor for oral squamous cell carcinoma (OSCC) biological behaviour. Nevertheless, this prognostic value is still yet to be validated. We aim to quantify prognostic significance of CAIX overexpression in OSCC by meta-analysis. We performed searches in MEDLINE, EMBASE, SCOPUS, WOS, WHO’S databases, CPCI, and OATD from inception to August 2019. Overall survival (OS), disease-free survival (DFS), locoregional control (LC), and disease-specific survival (DSS) were considered as outcomes of interest. Overall 18 studies were included. CAIX overexpression was associated with worse OS (hazard ratio [HR] = 1.45 95% confidence interval [CI] 1.17–1.80) and DFS (HR = 1.98 95% CI 1.18–3.32). To the contrary, it was neither associated with LC (HR = 1.01 95% CI 0.50–2.02) nor with DSS (HR = 1.35 95% CI 0.78–2.33). Heterogeneity was negligible in all analyses except for DSS. Small studies effect was not significant for OS and DFS. This study shows that immunohistochemical CAIX assessment is a useful OSCC prognostic biomarker.

Carbonic anhydrase modulation of emotional memory. Implications for the treatment of cognitive disorders

Carbonic anhydrases (CAs, EC 4.2.1.1) are metalloenzymes which use CO₂ as substrate, catalysing its interconversion to bicarbonate and a proton. In humans 15 CAs are expressed, 12 of which are catalytically active: the cytosolic CA I-III, VII, XIII, the membrane-bound CA IV, the mitochondrial CA VA and VB, the secreted CA VI, and the transmembrane CA IX, XII, XIV. Nine isoforms are present in the mammalian brain. Evidence supporting that CA inhibitors impair memory in humans has come from studies on topiramate and acetazolamide during acute high-altitude exposure. In contrast, administration of CA activators in animal models enhances memory and learning. Here we review the involvement of selective CA inhibition/activation in cognition-related disorders. CAs may represent a crucial family of new targets for improving cognition as well as in therapeutic areas, such as phobias, obsessive-compulsive disorder, generalised anxiety, and post-traumatic stress disorders, for which few efficient therapies are available.

Preparation, carbonic anhydrase enzyme inhibition and antioxidant activity of novel 7-amino-3,4-dihydroquinolin-2(1H)-one derivatives incorporating mono or dipeptide moiety

New dipeptide–dihydroquinolinone derivatives were successfully synthesised by benzotriazole mediated nucleophilic acyl substitution reaction and their structures were elucidated by spectroscopic and analytic techniques. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was determined against four human (h) isoforms, hCA I, hCA II, hCA IX and hCA XII. While all compounds showed moderate to good in vitro CA inhibitory properties against hCA IX and hCA XII with inhibition constants in the micromolar level (37.7–86.8 and 2.0–8.6 µM, respectively), they did not show inhibitory activity against hCA I and hCA II up to 100 µM concentration. The antioxidant capacity of the peptide–dihydroquinolinone conjugates was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. Most of the synthesised compounds showed low antioxidant activities compared to the control antioxidant compounds BHA and α-tocopherol.