Pharmacological inhibition of carbonic anhydrase XII interferes with cell proliferation and induces cell apoptosis in T-cell lymphomas

Carbonic anhydrases: Moiety appended derivatives, medicinal and pharmacological implications

In the realm of enzymology, Carbonic anhydrase (CA) emerges as a pivotal protagonist orchestrating the rapid conversion of carbon dioxide and water into bicarbonate ions and hydrogen ions, respectively. Carbonic anhydrase inhibitors (CAIs) are the class of drugs that target various isoforms of the enzyme, and these inhibitors play a crucial role in the treatment and management of multiple diseases such as cancer, glaucoma, high altitude sickness, rheumatoid arthritis, obesity, epilepsy, and sleep apnea. Several structural classes of CAIs developed till date possess unique architects of the pharmacophoric requirements around the central core moiety for the selective targeting of various isoforms of the CA. Recent advancements in drug design and development, along with technologies that aid in structure determination, have led to the development of several isoform-selective inhibitors of CA enzymes. However, their clinical development was hampered by the lack of desired therapeutic efficacy, isoform selectivity and safety profile. This review covers the most recent approaches used by different researchers concerned with the development of isoform-selective carbonic anhydrase inhibitors belonging to distinct structural classes like sulphonamides, carbazoles, selenols, coumarin, organotelluride, topiramate, thiophene, triazole, uracil-modified benzylic amines, and thiourea etc. In addition, their structure-activity relationships, biological evaluation, and in silico studies inlcuding the forthcoming avenues of advancements have been discussed. This review serves as a valuable resource for developing potent and efficacious CAIs with remarkable therapeutic implications; offering insights into their potency, specificity, and potential clinical applications.

Carbonic Anhydrase and Biomarker Research: New Insights

Carbonic anhydrase (CA) is a widespread metalloenzyme with eight genetically distinct families catalyzing the reversible hydration of CO₂ to HCO₃^- and H⁺ [...].

Novel Thiopyrano[2,3-d]thiazole-pyrazole Hybrids as Potential Nonsulfonamide Human Carbonic Anhydrase IX and XII Inhibitors: Design, Synthesis, and Biochemical Studies

In recent years, molecular hybridization strategies have developed into a potent strategy for drug discovery. A series of novel thiopyrano[2,3-d]thiazoles linked to the pyrazole moiety was designed and developed as anticancer agents by a molecular hybridization. Target compounds were synthesized and characterized by spectroscopic tools as well as X-ray crystallography analysis as in the case of thiopyrano[2,3-d]thiazole derivative 5a. The MTT assay was used to demonstrate the in vitro efficacy of compounds 5a-g and 7a-j on MCF-7 and HePG-2. The results showed that some cycloadducts such as bromophenyl-4-thioxo-2-thiazolidinone 3e, 4-methylphenyl derivative of thiopyrano[2,3-d]thiazole 5d, and 6-substituted-thiopyrano[2,3-d]thiazoles 7e-j displayed good to excellent IC₅₀ in the range of 10.08 ± 1.5 to 25.95 ± 2.8 μg/mL against the MCF-7 cell line and from 7.83 ±2.1 to 13.37 ± 1.2 μg/mL against the HePG-2 cell line. To explore the enzymatic tests for isozymes hCAIX and hCAXII, the most promising eight compounds 3e, 5d, and 7e-j with IC₅₀ ranging from 7.83 ± 2.1 to 25.95 ± 2.8 μM were chosen. Compound 7e exhibited an IC₅₀ (0.067 ± 0.003 μM) similar to that of the standard drug AZA against CAIX (0.059 ± 0.003 μM)). For CAXII, the compound 7i had an IC₅₀ equal to 0.123 ± 0.007 μM compared to that of AZA (0.083 ± 0.005 μM). In addition, using flow cytometry, cell cycle analysis and apoptosis studies in HePG-2 were performed for the two potent anticancer and selective carbonic anhydrase agents (7e and 7i). An enzymatic assay of these two compounds against caspase-9 was also examined. Interestingly, the molecular docking studies revealed that compounds 7e and 7i successfully embedded themselves in the active pockets of the CAIX and CAXII enzymes through different interactions. Overall, the novel thiopyrano[2,3-d]thiazole-pyrazole hybrids (7e and 7i) were suggested to be potent and selective inhibitors of CAIX and CAXII.

Pharmacological inhibition of Carbonic Anhydrase IX and XII to enhance targeting of acute myeloid leukaemia cells under hypoxic conditions

Acute myeloid leukaemia (AML) is an aggressive form of blood cancer that carries a dismal prognosis. Several studies suggest that the poor outcome is due to a small fraction of leukaemic cells that elude treatment and survive in specialised, oxygen (O₂)‐deprived niches of the bone marrow. Although several AML drug targets such as FLT3, IDH1/2 and CD33 have been established in recent years, survival rates remain unsatisfactory, which indicates that other, yet unrecognized, mechanisms influence the ability of AML cells to escape cell death and to proliferate in hypoxic environments. Our data illustrates that Carbonic Anhydrases IX and XII (CA IX/XII) are critical for leukaemic cell survival in the O₂‐deprived milieu. CA IX and XII function as transmembrane proteins that mediate intracellular pH under low O₂ conditions. Because maintaining a neutral pH represents a key survival mechanism for tumour cells in O₂‐deprived settings, we sought to elucidate the role of dual CA IX/XII inhibition as a novel strategy to eliminate AML cells under hypoxic conditions. Our findings demonstrate that the dual CA IX/XII inhibitor FC531 may prove to be of value as an adjunct to chemotherapy for the treatment of AML.

Uncovering the interplay between pH receptors and immune cells: Potential drug targets (Review)

Extracellular acidosis is associated with various immunopathological states. The microenvironment of numerous solid tumours and inflammatory responses during acute or chronic infection are all related to a pH range of 5.5‑7.0. The relationship between inflammation and immune escape, cancer metabolism, and immunologic suppression drives researchers to focus on the effects of low pH on diverse components of disease immune monitoring. The potential effect of low extracellular pH on the immune function reveals the importance of pH in inflammatory and immunoreactive processes. In this review, the mechanism of how pH receptors, including monocarboxylate transporters (MCTs), Na⁺/H⁺ exchanger 1, carbonic anhydrases (CAs), vacuolar‑ATPase, and proton‑sensing G‑protein coupled receptors (GPCRs), modulate the immune system in disease, especially in cancer, were studied. Their role in immunocyte growth and signal transduction as part of the immune response, as well as cytokine production, have been documented in great detail. Currently, immunotherapy strategies have positive therapeutic effects for patients. However, the acidic microenvironment may block the effect of immunotherapy through compensatory feedback mechanisms, leading to drug resistance. Therefore, we highlight promising therapeutic developments regarding pH manipulation and provide a framework for future research.

Post-translational modifications in tumor-associated carbonic anhydrases

Human carbonic anhydrases IX (hCA IX) and XII (hCA XII) are two proteins associated with tumor formation and development. These enzymes have been largely investigated both from a biochemical and a functional point of view. However, limited data are currently available on the characterization of their post-translational modifications (PTMs) and the functional implication of these structural changes in the tumor environment. In this review, we summarize existing literature data on PTMs of hCA IX and hCA XII, such as disulphide bond formation, phosphorylation, O-/N-linked glycosylation, acetylation and ubiquitination, highlighting, when possible, their specific role in cancer pathological processes.

Synthesis and biological evaluation of some 1-naphthol derivatives as antioxidants, acetylcholinesterase, and carbonic anhydrase inhibitors

A series of some naphthol derivatives 4a-f, 5a,f, 6a, and 7a,b (six novel ones: 4c,d, 5a, 6a, 7a,b) bearing F, Cl, Br, OMe, and dioxole substituents at different positions of the aromatic rings was designed, synthesized, and characterized. The naphthol derivatives were synthesized in three steps, namely the addition reaction of furan via Diels-Alder cycloaddition reaction, copper(II) trifluoromethanesulfonate (Cu(OTf)₂ )-catalyzed aromatization reaction, and the bromination reaction, respectively. The structures of the newly obtained compounds (4c,d, 5a, 6a, 7a,b) were characterized by spectroscopic techniques. In addition, some biological activity studies were investigated under in vitro conditions. Inhibition studies of these compounds were performed on human carbonic anhydrase (hCA) I and II isoenzymes purified from human erythrocytes as a biological evaluation. Moreover, their potential antioxidant and antiradical activities were studied by analytical methods like ABTS^•+ and DPPH• scavenging, and it was determined that some molecules showed good activity. Also, inhibition of acetylcholinesterase (AChE), which is a marker of many degenerative neurological diseases, was tested and the results were discussed. Excellent enzyme inhibition results were recorded for most of the molecules. These 1-naphthol derivatives were found as effective inhibitors for hCA I, hCA II, and AChE with K _i values ranging from 0.034 ± 0.54 to 0.724 ± 0.18 µM for hCA I, 0.172 ± 0.02 to 0.562 ± 0.21 µM for hCA II, and 0.096 ± 0.01 to 0.177 ± 0.02 µM for AChE.

Emerging role of carbonic anhydrase inhibitors

Inhibition of carbonic anhydrase (CA, EC 4.2.1.1) was clinically exploited for decades, as most modern diuretics were obtained considering as lead molecule acetazolamide, the prototypical CA inhibitor (CAI). The discovery and characterization of multiple human CA (hCA) isoforms, 15 of which being known today, led to new applications of their inhibitors. They include widely clinically used antiglaucoma, antiepileptic and antiobesity agents, antitumor drugs in clinical development, as well as drugs for the management of acute mountain sickness and idiopathic intracranial hypertension (IIH). Emerging roles of several CA isoforms in areas not generally connected to these enzymes were recently documented, such as in neuropathic pain, cerebral ischemia, rheumatoid arthritis, oxidative stress and Alzheimer's disease. Proof-of-concept studies thus emerged by using isoform-selective inhibitors, which may lead to new clinical applications in such areas. Relevant preclinical models are available for these pathologies due to the availability of isoform-selective CAIs for all human isoforms, belonging to novel classes of compounds, such as coumarins, sulfocoumarins, dithiocarbamates, benzoxaboroles, apart the classical sulfonamide inhibitors. The inhibition of CAs from pathogenic bacteria, fungi, protozoans or nematodes started recently to be considered for obtaining anti-infectives with a new mechanism of action.

Novel insights on saccharin- and acesulfame-based carbonic anhydrase inhibitors: design, synthesis, modelling investigations and biological activity evaluation

A large library of saccharin and acesulfame derivatives has been synthesised and evaluated against four isoforms of human carbonic anhydrase, the two off-targets hCA I/II and the tumour related isoforms hCA IX/XII. Different strategies of scaffold modification have been attempted on both saccharin as well as acesulfame core leading to the obtainment of 60 compounds. Some of them exhibited inhibitory activity in the nanomolar range, albeit some of the performed changes led to either micromolar activity or to its absence, against hCA IX/XII. Molecular modelling studies focused the attention on the binding mode of these compounds to the enzyme. The proposed inhibition mechanism is the anchoring to zinc-bound water molecule. Docking studies along with molecular dynamics also underlined the importance of the compounds flexibility (e.g. achieved through the insertion of methylene group) which favoured potent and selective hCA inhibition.

Tiliroside as a CAXII inhibitor suppresses liver cancer development and modulates E2Fs/Caspase-3 axis

Liver cancer is the fatal cause of cancer deaths worldwide due to its aggressiveness and lack of effective therapies. Tiliroside (C₃₀H₂₆O₁₃) is an active compound extracted from herb plant Tribulus terrestris L., which has been used as alternative therapy in clinic practice. However, its therapeutic use against liver cancer has not been previously reported. Here, we showed that Tiliroside exerted significantly higher anti-proliferation effect on liver cancer cell lines Hep3B and SNU-449 than on liver normal cell THLE-3 cells or NC group, respectively, by using MTS assay. Results from colony formation, immigration and invasion assays support the anticancer efficacy of Tiliroside and its low-toxic property while treating liver normal cell THLE-3. 3D spheroid formation and CD133 expression level also displays its anti-stemness effect. It has been showed that Tiliroside may function as Carbonic anhydrases XII (CAXII) inhibitor and affects apoptotic E2F1/E2F3/Caspase-3 axis by using CAXII esterase activity assay, Human carbonic anhydrase 12 (CA-12) ELISA Kit, quantitative reverse transcription PCR (RT-qPCR) as well as CaspACE Assay System, respectively. In summary, we demonstrate for the first time that Tiliroside suppresses liver cancer development possibly by acting as a novel CAXII inhibitor, which warrant further investigation on its therapeutic implications.

Experimental Carbonic Anhydrase Inhibitors for the Treatment of Hypoxic Tumors

Carbonic anhydrase (CA, EC 4.2.1.1) isoforms IX and XII are overexpressed in many hypoxic tumors as a consequence of the hypoxia inducible factor (HIF) activation cascade, being present in limited amounts in normal tissues. These enzymes together with many others are involved in the pH regulation and metabolism of hypoxic cancer cells, and were validated as antitumor targets recently. A multitude of targeting strategies against these enzymes have been proposed and are reviewed in this article. The small molecule inhibitors, small molecule drug conjugates (SMDCs), antibody-drug conjugates (ADACs) or cytokine-drug conjugates but not the monoclonal antibodies against CA IX/XII will be discussed. Relevant synthetic chemistry efforts, coupled with a multitude of preclinical studies, demonstrated that CA IX/XII inhibition leads to the inhibition of growth of primary tumors and metastases and depletes cancer stem cell populations, all factors highly relevant in clinical settings. One small molecule inhibitor, sulfonamide SLC-0111, is the most advanced candidate, having completed Phase I and being now in Phase Ib/II clinical trials for the treatment of advanced hypoxic solid tumors.

Inhibitory Monoclonal Antibodies and Their Recombinant Derivatives Targeting Surface-Exposed Carbonic Anhydrase XII on Cancer Cells

Monoclonal and recombinant antibodies are widely used for the diagnostics and therapy of cancer. They are generated to interact with cell surface proteins which are usually involved in the development and progression of cancer. Carbonic anhydrase XII (CA XII) contributes to the survival of tumors under hypoxic conditions thus is considered a candidate target for antibody-based therapy. In this study, we have generated a novel collection of monoclonal antibodies (MAbs) against the recombinant extracellular domain of CA XII produced in HEK-293 cells. Eighteen out of 24 MAbs were reactive with cellular CA XII on the surface of live kidney and lung cancer cells as determined by flow cytometry. One MAb 14D6 also inhibited the enzymatic activity of recombinant CA XII as measured by the stopped-flow assay. MAb 14D6 showed the migrastatic effect on human lung carcinoma A549 and renal carcinoma A498 cell lines in a ‘wound healing’ assay. It did not reduce the growth of multicellular lung and renal cancer spheroids but reduced the cell viability by the ATP Bioluminescence assay. Epitope mapping revealed the surface-exposed amino acid sequence (35-FGPDGENS-42) close to the catalytic center of CA XII recognized by the MAb 14D6. The variable regions of the heavy and light chains of MAb 14D6 were sequenced and their complementarity-determining regions were defined. The obtained variable sequences were used to generate recombinant antibodies in two formats: single-chain fragment variable (scFv) expressed in E. coli and scFv fused to human IgG1 Fc fragment (scFv-Fc) expressed in Chinese Hamster Ovary (CHO) cells. Both recombinant antibodies maintained the same specificity for CA XII as the parental MAb 14D6. The novel antibodies may represent promising tools for CA XII-related cancer research and immunotherapy.

The roles of carbonic anhydrases IX and XII in cancer cell adhesion, migration, invasion and metastasis

The main function of carbonic anhydrases (CAs) in cancer cells is the pH regulation through a conversion of H₂ O and CO₂ to H⁺ and HCO₃ ^- . However, the data of in vitro and in vivo studies have demonstrated that transmembrane isoforms of CA IX and CA XII are involved in various steps of cancer cell migration, invasion and metastasis. According to literature, inhibition of these CAs can affect the expression of multiple proteins. Some scientific groups have reported the possible interactions between CA IX and E-cadherin-catenin system, CA IX and integrins, CA IX, CA XII and ion transporters, which all are highly involved in cell-to-cell adhesion, the formation of membrane protrusions and focal adhesions. Nevertheless, CA IX and CA XII have a high impact on tumour growth and metastases formation. The data discussed in this review are quite recent. It highly support the role of CA IX and CA XII in various cancer metastasis processes through their interactions to other invasion proteins. Nevertheless, all findings show the great potential of these CAs in the context of research and application in clinical use.

5-Arylisothiazol-3(2H)-one-1,(1)-(di)oxides: A new class of selective tumor-associated carbonic anhydrases (hCA IX and XII) inhibitors

Sixteen 5-aryl-substituted isothiazol-3(2H)-one-1,(1)-(di)oxide analogs have been prepared from the corresponding 5-chloroisothiazol-3(2H)-one-1-oxide or -1,1-dioxide by a Suzuki-Miyaura cross-coupling reaction and screened for their inhibition potency against four human carbonic anhydrase isoenzymes: the transmembrane tumor-associated hCA IX and XII and the cytosolic off-target hCA I and II. Most of the synthesized derivatives inhibited hCA IX and XII isoforms in nanomolar range, whereas remained inactive or modestly active against both hCA I and II isoenzymes. In the N-tert-butylisothiazolone series, the 5-phenyl-substituted analog (1a) excelled in the inhibition of tumor-associated hCA IX and XII (K_i = 4.5 and K_i = 4.3 nM, respectively) with excellent selectivity against off target hCA I and II isoenzymes (S > 2222 and S > 2325, respectively). Since the highest inhibition activities were observed with N-tert-butyl derivatives, lacking a zinc-binding group, we suppose to have a new binding mode situated out of the active site. Additionally, three free-NH containing analogs (3a, 4a, 3i) have also been prepared in order to study the impact of free-NH containing N-acyl-sulfinamide- (-SO-NH-CO-) or N-acyl-sulfonamide-type (-SO₂-NH-CO-) derivatives on the inhibitory potency and selectivity. Screening experiments evidenced 5-phenylisothiazol-3(2H)-one-1,1-dioxide (4a), the closest saccharin analog, to be the most active derivative with inhibition constants of K_i = 40.3 nM and K_i = 9.6 nM against hCA IX and hCA XII, respectively. The promising biological results support the high potential of 5-arylisothiazolinone-1,(1)-(di)oxides to be exploited for the design of potent and cancer-selective carbonic anhydrase inhibitors.

An inhibitory antibody targeting carbonic anhydrase XII abrogates chemoresistance and significantly reduces lung metastases in an orthotopic breast cancer model in vivo

Carbonic anhydrase XII (CAXII) is a membrane-tethered ectoenzyme involved in intracellular pH regulation and overexpressed across various types of human cancer. Because CAXII inhibition shows antitumor activity in vitro, it is thought that the enzyme is mandatory for maximum tumor growth, above all under hypoxic conditions. Recently, it has been shown that CAXII is co-expressed along with the P-glycoprotein (P-GP) on many tumor cells and that both proteins physically interact. Of interest, blocking CAXII activity also decreases P-GP activity in cancer cells both in vitro and in vivo. Previously, we have reported on the development of a monoclonal antibody, termed 6A10, which specifically and efficiently blocks human CAXII activity. Here, we demonstrate that 6A10 also indirectly reduces P-GP activity in CAXII/P-GP double-positive chemoresistant cancer cells, resulting in enhanced chemosensitivity as revealed by enhanced accumulation of anthracyclines and increased cell death in vitro. Even more important, we show that mice carrying human triple-negative breast cancer xenografts co-treated with doxorubicin (DOX) and 6A10 show a significantly reduced number of metastases. Collectively, our data provide evidence that the inhibition of CAXII with 6A10 is an attractive way to reduce chemoresistance of cancer cells and to interfere with the metastatic process in a clinical setting.

A novel proteochemometrics model for predicting the inhibition of nine carbonic anhydrase isoforms based on supervised Laplacian score and k-nearest neighbour regression

Carbonic anhydrases (CAs) are essential enzymes in biological processes. Prediction of the activity of compounds towards CA isoforms could be evaluated by computational techniques to discover a novel therapeutic inhibitor. Studies such as quantitative structure-activity relationships (QSARs), molecular docking and pharmacophore modelling have been carried out to design potent inhibitors. Unfortunately, QSAR does not consider the information of target space in the model. We successfully developed an in silico proteochemometrics model that simultaneously uses target and ligand descriptors to predict the activities of CA inhibitors. Herein, a strong predictive model was built for the prediction of protein-ligand binding affinity between nine human CA isoforms and 549 ligands. We applied descriptors obtained from the PROFEAT webserver for the proteins. Ligands were encoded by descriptors from PaDEL-Descriptor software. Supervised Laplacian score (SLS) and particle swarm optimization were used for feature selection. Models were derived using k-nearest neighbour (KNN) regression and a kernel smoother model. The predictive ability of the models was evaluated by an external validation test. Statistical results (Q²_ext = 0.7806, r²_test = 0.7811 and RMSE_test = 0.5549) showed that the model generated using SLS and KNN regression outperformed the other models. Consequently, the selectivity of compounds towards these enzymes will be predicted prior to synthesis.

Carbonic Anhydrases: Role in pH Control and Cancer

The pH of the tumor microenvironment drives the metastatic phenotype and chemotherapeutic resistance of tumors. Understanding the mechanisms underlying this pH-dependent phenomenon will lead to improved drug delivery and allow the identification of new therapeutic targets. This includes an understanding of the role pH plays in primary tumor cells, and the regulatory factors that permit cancer cells to thrive. Over the last decade, carbonic anhydrases (CAs) have been shown to be important mediators of tumor cell pH by modulating the bicarbonate and proton concentrations for cell survival and proliferation. This has prompted an effort to inhibit specific CA isoforms, as an anti-cancer therapeutic strategy. Of the 12 active CA isoforms, two, CA IX and XII, have been considered anti-cancer targets. However, other CA isoforms also show similar activity and tissue distribution in cancers and have not been considered as therapeutic targets for cancer treatment. In this review, we consider all the CA isoforms and their possible role in tumors and their potential as targets for cancer therapy.

Toward a hierarchical virtual screening and toxicity risk analysis for identifying novel CA XII inhibitors

Carbonic anhydrase isoform XII (CA XII) is a potential target for cancer treatment. In this study, pharmacophore modeling, hierarchical virtual screening, and toxicity risk analysis were performed for identifying novel CA XII inhibitors. A pharmacophore model of two classes of CA XII inhibitors was generated. The pharmacophore model indicated the important features of inhibitors for the binding with the CA XII. The model was then utilized to screen the ZINC and CoCoCo databases for retrieving potential hit compounds of CA XII. For accurate conclusions about the selectivity of inhibitors, the retrieved molecules which obey of Lipinski's rule of five (RO5) and have no toxicity risk were docked in a CA XII 3D structure by smina. Finally, on the basis of binding affinity and the binding mode of the molecules, twelve molecules were prioritized as promising hits. It should be noted that two of hits H5 and H6 were previously reported in the CHEMBL database. This hierarchical method is worthy of reducing the time and using almost all information available. The final hits may be used as a lead to discovery novel CA XII inhibitors.

Co-targeting intracellular pH and essential amino acid uptake cooperates to induce cell death of T-ALL/LL cells

Cancer cells reprogram their metabolism to optimize their growth and proliferation in the host microenvironment. For this purpose, they enhance the uptake of extracellular nutrients and deal with the metabolic waste products through the overexpression of numerous membrane proteins including amino-acid transporters (LAT1) and acid-base regulating enzymes, such as carbonic anhydrases (CAs). Here we describe the anti-tumoral effects of a new class of CAXII inhibitors, the glycosyl coumarins on T-ALL/LL cells. These effects appeared to be mediated through inhibition of mTOR/Akt pathway and c-myc downregulation. Interestingly, we show that the combined targeting of amino acid fluxes and pH regulators provides a promising therapeutic strategy in the future of T-ALL/LL management.

Crucial role of carbonic anhydrase IX in tumorigenicity of xenotransplanted adult T-cell leukemia-derived cells

Carbonic anhydrase IX (CA9) is a membrane‐associated carbonic anhydrase that regulates cellular pH, is upregulated in various solid tumors, and is considered to be a therapeutic target. Here, we describe the essential role of CA9 in the tumorigenicity of cells derived from human adult T‐cell leukemia/lymphoma (ATL). We previously established the highly tumorigenic ST1‐N6 subline from the ATL‐derived ST1 cell line by serial xenotransplantation in NOG mice. In the present study, we first show that CA9 expression is strongly enhanced in ST1‐N6 cells. We then sorted ST1 cells by high or low CA9 expression and established ST1‐CA9^high and ST1‐CA9^low sublines. ST1‐CA9^high cells, like ST1‐N6 cells, were more strongly tumorigenic than ST1‐CA9^low or parental ST1 cells when injected into NOG mice. Knockdown of CA9 with shRNAs suppressed the ability of ST1‐CA9^high cells to initiate tumors, and the tumorigenicity of ST1 cells was significantly enhanced by introducing wild‐type CA9 or a CA9 mutant with deletion of an intracytoplasmic domain. However, a CA9 with point mutations in the catalytic site did not increase the tumorigenicity of ST1 cells. Furthermore, we detected a small population of CA9⁺CD25⁺ cells in lymph nodes of ATL patients. These findings suggest that CA9, and particularly its carbonic anhydrase activity, promotes the tumorigenicity of ATL‐derived cells and may be involved in malignant development of lymphoma‐type ATL.

Recent Advances in Targeting Tumor Energy Metabolism with Tumor Acidosis as a Biomarker of Drug Efficacy

Cancer cells employ a deregulated cellular metabolism to leverage survival and growth advantages. The unique tumor energy metabolism presents itself as a promising target for chemotherapy. A pool of tumor energy metabolism targeting agents has been developed after several decades of efforts. This review will cover glucose and fatty acid metabolism, PI3K/AKT/mTOR, HIF-1 and glutamine pathways in tumor energy metabolism, and how they are being exploited for treatments and therapies by promising pre-clinical or clinical drugs being developed or investigated. Additionally, acidification of the tumor extracellular microenvironment is hypothesized to be the result of active tumor metabolism. This implies that tumor extracellular pH (pHe) can be a biomarker for assessing the efficacy of therapies that target tumor metabolism. Several translational molecular imaging methods (PET, MRI) for interrogating tumor acidification and its suppression are discussed as well.

Advances in Anti-Cancer Drug Development Targeting Carbonic Anhydrase IX and XII

The microenvironment within a solid tumor is heterogeneous with regions being both acidic and hypoxic. As a result of this, cancer cells upregulate genes that allow survival in such environments. Some of these genes are pH regulatory factors, including carbonic anhydrase IX (CA IX) and in some cases XII (CA XII). CA IX helps to maintain normal cytoplasmic pH (pHi) while simultaneously contributing to the extracellular pH (pHe). CA XII is also thought to be responsible for stabilizing pHe at physiological conditions. Extracellular acidification of the tumor microenvironment promotes local invasion and metastasis while decreasing the effectiveness of adjuvant therapies, thus contributing to poor cancer clinical outcomes. In this review, we describe the properties of CA IX and CA XII that substantiate their potential use as anticancer targets. We also discuss the current status of CA isoform-selective inhibitor development and patents of CA IX/XII targeted inhibitors that show potential for treating aggressive tumors. Some of the recently published patents discussed include sulfonamide-based small molecule inhibitors including derivatives of boron cluster compounds; metal complexes of poly(carboxyl)amine-containing ligands; nitroi-midazole-, ureidosulfonamide-, and coumarin-based compounds; as well as G250 and A610 monoclonal antibodies for cancer treatment.

Inhibition of human carbonic anhydrase isozymes I, II, IX and XII with a new series of sulfonamides incorporating aroylhydrazone-, [1,2,4]triazolo[3,4-b][1,3,4]thiadiazinyl- or 2-(cyanophenylmethylene)-1,3,4-thiadiazol-3(2H)-yl moieties

A series of benzenesulfonamides incorporating aroylhydrazone, piperidinyl, sulfone, [1,2,4]triazolo[3,4-b][1,3,4]thiadiazinyl- or 2-(cyanophenyl-methylene)-1,3,4-thiadiazol-3(2H)-yl moieties was investigated as inhibitors of four α-carbonic anhydrases (CAs, EC 4.2.1.1), the human (h) isoforms hCA I, II (cytosolic, offtarget enzymes) and hCA IX and XII (transmembrane, tumor-associated isoforms). Low nanomolar activity was observed against hCA II (KIs of 0.56-17.1 nM) with these sulfonamides, whereas the slow cytosolic isoform hCA I was less inhibited by these compounds (KIs of 86.4 nM-32.8 µM). Most of these sulfonamides significantly inhibited CA IX, with KIs in the range of 4.5-47.0 nM, although some of the derivatives incorporating bulkier bicyclic moieties, as well as 2-thienyl fragments, showed a weaker activity against this isoform (KIs in the range 50.1-553 nM). All the investigated compounds also inhibited CA XII with KIs in the range 0.85-376 nM. The best inhibitors were those incorporating bulky [1,2,4]triazolo[3,4-b][1,3,4]thiadiazinyl moieties and 1,3,4-thiadiazol-3(2H)-yl groups.