Pharmacological Inhibition of CA-IX Impairs Tumor Cell Proliferation, Migration and Invasiveness

Carbonic anhydrase IX: An atypical target for innovative therapies in cancer

Carbonic anhydrases (CAs), are metallo-enzymes implicated in several pathophysiological processes where tissue pH regulation is required. CA IX is a tumor-associated CA isoform induced by hypoxia and involved in the adaptation of tumor cells to acidosis. Indeed, several tumor-driving pathways can induce CA IX expression, and this in turn has been associated to cancer cells invasion and metastatic features as well as to induction of stem-like features, drug resistance and recurrence. After its functional and structural characterization CA IX targeting approaches have been developed to inhibit its activity in neoplastic tissues, and to date this field has seen an incredible acceleration in terms of therapeutic options and biological readouts. Small molecules inhibitors, hybrid/dual targeting drugs, targeting antibodies and adoptive (CAR-T based) cell therapy have been developed at preclinical level, whereas a sulfonamide CA IX inhibitor and an antibody entered Phase Ib/II clinical trials for the treatment and imaging of different solid tumors. Here recent advances on CA IX biology and pharmacology in cancer, and its therapeutic targeting will be discussed.

Benzenesulfonamide decorated dihydropyrimidin(thi)ones: carbonic anhydrase profiling and antiproliferative activity

In the last decades, carbonic anhydrases (CAs) have become the top investigated innovative pharmacological targets and, in particular, isoforms IX and XII have been widely studied due to the evidence of their overexpression in hypoxic tumors. The frantic race to find new anticancer agents places the quick preparation of large libraries of putative bioactive compounds as the basis of a successful drug discovery and development programme. In this context, multi-component and, in general, one-step reactions are becoming very popular and, among them, Biginelli's reaction gave clean and easy-to-isolate products. Thus, we synthesized a series of Biginelli's products (10-17a-b) and similar derivatives (20-21) bearing the benzenesulfonamide moiety, which is known to inhibit CA enzymes. Through the stopped-flow technique, we were able to assess their ability to inhibit the targeted CAs IX and XII in the nanomolar range with promising selectivity over the physiologically relevant isoforms I and II. Crystallography studies and docking simulations helped us to gain insight into the interaction patterns established in the enzyme-inhibitor complex. From a chemical similarity-based screening of in-house libraries of compounds, a diphenylpyrimidine (23) emerged. The surprisingly potent inhibitory activity of 23 for CAs IX and XII along with its strong antiproliferative effect on two (triple-negative breast cancer MDA-MB-231 and glioblastoma U87MG) cell lines laid the foundation for further investigation, again confirming the key role of CAs in cancer.

Effective Anticancer Potential of a New Sulfonamide as a Carbonic Anhydrase IX Inhibitor Against Aggressive Tumors

This study examines efficiency of a newly synthesized sulfonamide derivative 2-bromo-N-(4-sulfamoylphenyl)propanamide (MMH-1) on the inhibition of Carbonic Anhydrase IX (CA IX), which is overexpressed in many solid tumors including breast cancer. The inhibitory potential of MMH-1 compound against its four major isoforms, including cytosolic isoforms hCA I and II, as well as tumor-associated membrane-bound isoforms hCA IX and XII, was evaluated. To this context, the cytotoxic effect of MMH-1 on cancer and normal cells was tested and found to selectively affect MDA-MB-231 cells. MMH-1 reduced cell proliferation by holding cells in the G0/G1 phase (72 %) and slowed the cells' wound healing capacity. MMH-1 inhibited CA IX under both hypoxic and normoxic conditions and altered the morphology of triple negative breast cancer cells. In MDA-MB-231 cells, inhibition of CA IX was accompanied by a decrease in extracellular pH acidity (7.2), disruption of mitochondrial membrane integrity (80 %), an increase in reactive oxygen levels (25 %), and the triggering of apoptosis (40 %). In addition, the caspase cascade (CASP-3, -8, -9) was activated in MDA-MB-231 cells, triggering both the extrinsic and intrinsic apoptotic pathways. The expression of pro-apoptotic regulatory proteins (Bad, Bax, Bid, Bim, Cyt-c, Fas, FasL, TNF-a, TNF-R1, HTRA, SMAC, Casp-3, -8, P21, P27, and P53) was increased, while the expression of anti-apoptotic proteins, apoptosis inhibitor proteins (IAPs), and heat shock proteins (HSPs) (Bcl-2, Bcl-w, cIAP-2, HSP27, HSP60, HSP70, Survivin, Livin, and XIAP) was decreased. These results propose that the MMH-1 compound could triggers apoptosis in MDA-MB-231 cells via the pH/MMP/ROS pathway through the inhibition of CA IX. This compound is thought to have high potential and promising anticancer properties in the treatment of aggressive tumors.

Novel 2-(hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide based thiosemicarbazides as potent and selective inhibitors of tumor-associated human carbonic anhydrase IX and XII: Synthesis, cytotoxicity, and molecular modelling studies

In the pursuit of discovering new selective carbonic anhydrase (CA, EC 4.2.1.1) inhibitors, a small collection of novel thiosemicarbazides (5a-5t) were designed and synthesized starting from 2-(hydrazinocarbonyl)-3-phenyl-1H-indole-5-sulfonamide which was evaluated as a potent inhibitor of different CA isoforms in a previous study. The newly synthesized compounds were examined against four human carbonic anhydrases (hCA), namely transmembrane tumor-related hCA IX/XII and cytosolic widespread off-targets hCA I/II. In enzyme inhibition assays, all nineteen compounds display up to ∼340-fold selectivity for hCA IX/XII over off-target isoforms hCA I/II. Four compounds have enzyme inhibition values (Ki) lower than 10 nM against tumor-associated isoforms hCA IX/XII including two compounds in the subnanomolar range (5r and 5s; hCA XII; Ki: 0.69 and 0.87 nM). The potential binding interactions of the most potent compounds against hCA IX and XII, compounds 5s and 5r, respectively, were investigated using ensemble docking and molecular dynamics studies. Cell viability assays using human colorectal adenocarcinoma cell line HT-29 and healthy skin fibroblasts CCD-86Sk show that compound 5e selectively inhibits HT-29 cancer cell proliferation (IC50: 53.32 ± 7.74 µM for HT-29; IC50: 74.64 ± 14.15 µM for CCD-986Sk). Finally, Western blot assays show that compounds 5e and 5r significantly reduce the expression of hCA XII in HT-29 cells. Moreover, 5e shows better cytotoxic activity in hypoxia compared to normoxic conditions. Altogether, the newly designed compounds show stronger inhibition of the tumor-associated hCA IX and XII isoforms and several tested compounds show selective cytotoxicity as well as downregulation of hCA XII expression.

Piperidine Derivatives: Recent Advances in Synthesis and Pharmacological Applications

Piperidines are among the most important synthetic fragments for designing drugs and play a significant role in the pharmaceutical industry. Their derivatives are present in more than twenty classes of pharmaceuticals, as well as alkaloids. The current review summarizes recent scientific literature on intra- and intermolecular reactions leading to the formation of various piperidine derivatives: substituted piperidines, spiropiperidines, condensed piperidines, and piperidinones. Moreover, the pharmaceutical applications of synthetic and natural piperidines were covered, as well as the latest scientific advances in the discovery and biological evaluation of potential drugs containing piperidine moiety. This review is designed to help both novice researchers taking their first steps in this field and experienced scientists looking for suitable substrates for the synthesis of biologically active piperidines.

SLC-0111, an inhibitor of carbonic anhydrase IX, attenuates hepatoblastoma cell viability and migration

Background

In response to hypoxia, tumor cells undergo transcriptional reprogramming including upregulation of carbonic anhydrase (CA) IX, a metalloenzyme that maintains acid-base balance. CAIX overexpression has been shown to correlate with poor prognosis in various cancers, but the role of this CA isoform in hepatoblastoma (HB) has not been examined.

Methods

We surveyed the expression of CAIX in HB specimens and assessed the impact of SLC-0111, a CAIX inhibitor, on cultured HB cells in normoxic and hypoxic conditions.

Results

CAIX immunoreactivity was detected in 15 out of 21 archival pathology HB specimens. The CAIX-positive cells clustered in the middle of viable tumor tissue or next to necrotic areas. Tissue expression of CAIX mRNA was associated with metastasis and poor clinical outcome of HB. Hypoxia induced a striking upregulation of CAIX mRNA and protein in three HB cell models: the immortalized human HB cell line HUH6 and patient xenograft-derived lines HB-295 and HB-303. Administration of SLC-0111 abrogated the hypoxia-induced upregulation of CAIX and decreased HB cell viability, both in monolayer and spheroid cultures. In addition, SLC-0111 reduced HB cell motility in a wound healing assay. Transcriptomic changes triggered by SLC-0111 administration differed under normoxic vs. hypoxic conditions, although SLC-0111 elicited upregulation of several tumor suppressor genes under both conditions.

Conclusion

Hypoxia induces CAIX expression in HB cells, and the CAIX inhibitor SLC-0111 has in vitro activity against these malignant cells.

Efficient Synthesis with Green Chemistry Approach of Novel Pharmacophores of Imidazole-Based Hybrids for Tumor Treatment: Mechanistic Insights from In Situ to In Silico

Simple Summary

Here, we report the eco-friendly synthesis and antitumor potential of the imidazole hybrids of pyrimidine. The results showed that all the compounds possess excellent inhibition of tumors, promoting enzymes hCA-IX and hCA-II. Furthermore, the selectivity index showed that compounds 7, 10, and 11 are selective inhibitors of hCA-IX, while compound 2 is a selective inhibitor of hCA-IX. More importantly, all the active inhibitors are toxic to the breast cancer cell line and non-cytotoxic for the normal breast cell line. These compounds would be a suitable choice to investigate in the in vivo models to check their efficacy against these particular targets. These newly identified human carbonic anhydrase inhibitors have potential to be considered as therapeutic leads for the treatment of CA-related diseases, especially for breast and lung tumors and glaucoma. Furthermore, lead optimization and preclinical and clinical investigations of these compounds are necessary to develop potential drug entities for the treatment of cancer.

Abstract

Imidazole-based pyrimidine hybrids are considered a remarkable class of compounds in pharmaceutical chemistry. Here, we report the anticancer bioactivities of eleven imidazole-based pyrimidine hybrids (1–11) that specifically target cytosolic carbonic anhydrase (CAs) isoenzymes, including human CA-II and human CA-IX (hCA-II, and hCA-IX). A highly eco-friendly aqueous approach was used for the formation of a carbon–carbon bond by reacting aromatic nitro group substitution of nitroimidazoles with carbon nucleophiles. The in vitro results indicate that this new class of compounds (1–11) includes significant inhibitors of hCA IX with IC₅₀ values in the range of 9.6 ± 0.2–32.2 ± 1.0 µM, while hCA II showed IC₅₀ values in range of 11.6 ± 0.2–31.1 ± 1.3 µM. Compound 2 (IC₅₀ = 12.3 ± 0.1 µM) showed selective inhibition for hCA-II while 7, 8, and 10 (IC₅₀ = 9.6–32.2 µM) were selective for hCA-IX. The mechanism of action was investigated through in vitro kinetics studies that revealed that compounds 7, 3, 11, 10, 4, and 9 for CA-IX and 1, 2, and 11 for CA-II are competitive inhibitors with dissociation constant (Ki) in the range of 7.32–17.02 µM. Furthermore, the in situ cytotoxicity of these compounds was investigated in the human breast cancer cell line MDA-MB-231 and compared with the normal human breast cell line, MCF-10A. Compound 5 showed excellent anticancer/cytotoxic activity in MDA-MB-231 with no toxicity to the normal breast cells. In addition, in silico molecular docking was employed to predict the binding mechanism of active compounds with their targets. This in silico observation aligned with our experimental results. Our findings signify that imidazole-based hybrids could be a useful choice to design anticancer agents for breast and lung tumors, or antiglaucoma compounds, by specific inhibition of carbonic anhydrases.

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.

The Nitric Oxide Donor [Zn(PipNONO)Cl] Exhibits Antitumor Activity through Inhibition of Epithelial and Endothelial Mesenchymal Transitions

Simple Summary

Nitric oxide (NO) plays a critical pathophysiological role in cancer by modulating several processes, such as angiogenesis, tumor growth, and metastatic potential. The aim of this study was to characterize the antitumor effects of a novel NO donor, [Zn(PipNONO)Cl], on the processes of epithelial– and endothelial–mesenchymal transitions (EMT and EndMT), known to actively participate in cancer progression. Two tumor cells lines were used in this study: human lung cancer cells (A549) and melanoma cells (A375), alone and co-cultured with human endothelial cells. Our results demonstrate that both tumor and endothelial cells were targets of NO action, which impaired EMT and EndMT functional and molecular features. Further studies are needed to finalize the therapeutic use of the novel NO donor.

Abstract

Exogenous nitric oxide appears a promising therapeutic approach to control cancer progression. Previously, a nickel-based nonoate, [Ni(SalPipNONO)], inhibited lung cancer cells, along with impairment of angiogenesis. The Zn(II) containing derivatives [Zn(PipNONO)Cl] exhibited a protective effect on vascular endothelium. Here, we have evaluated the antitumor properties of [Zn(PipNONO)Cl] in human lung cancer (A549) and melanoma (A375) cells. Metastasis initiates with the epithelial–mesenchymal transition (EMT) process, consisting of the acquisition of invasive and migratory properties by tumor cells. At not cytotoxic levels, the nonoate significantly impaired A549 and A375 EMT induced by transforming growth factor-β1 (TGF-β1). Reduction of the mesenchymal marker vimentin, upregulated by TGF-β1, and restoration of the epithelial marker E-cadherin, reduced by TGF-β1, were detected in both tumor cell lines in the presence of Zn-nonoate. Further, the endothelial–mesenchymal transition achieved in a tumor-endothelial cell co-culture was assessed. Endothelial cells co-cultured with A549 or A375 acquired a mesenchymal phenotype with increased vimentin, alpha smooth muscle actin and Smad2/3, and reduced VE-cadherin. The presence of [Zn(PipNONO)Cl] maintained a typical endothelial phenotype. In conclusion, [Zn(PipNONO)Cl] appears a promising therapeutic tool to control tumor growth and metastasis, by acting on both tumor and endothelial cells, reprogramming the cells toward their physiologic phenotypes.

Early growth response 1 transcription factor is essential for the pathogenic properties of human endometriotic epithelial cells

Although a non-malignant gynecological disorder, endometriosis displays some pathogenic features of malignancy, such as cell proliferation, migration, invasion and adaptation to hypoxia. Current treatments of endometriosis include pharmacotherapy and/or surgery, which are of limited efficacy and often associated with adverse side effects. Therefore, to develop more effective therapies to treat this disease, a broader understanding of the underlying molecular mechanisms that underpin endometriosis needs to be attained. Using immortalized human endometriotic epithelial and stromal cell lines, we demonstrate that the early growth response 1 (EGR1) transcription factor is essential for cell proliferation, migration and invasion, which represent some of the pathogenic properties of endometriotic cells. Genome-wide transcriptomics identified an EGR1-dependent transcriptome in human endometriotic epithelial cells that potentially encodes a diverse spectrum of proteins that are known to be involved in tissue pathologies. To underscore the utility of this transcriptomic data set, we demonstrate that carbonic anhydrase 9 (CA9), a homeostatic regulator of intracellular pH, is not only a molecular target of EGR1 but is also important for maintaining many of the cellular properties of human endometriotic epithelial cells that are also ascribed to EGR1. Considering therapeutic intervention strategies are actively being developed for EGR1 and CAIX in the treatment of other pathologies, we believe EGR1 and its transcriptome (which includes CA9) will offer not only a new conceptual framework to advance our understanding of endometriosis but will also furnish new molecular vulnerabilities to be leveraged as potential therapeutic options in the future treatment of endometriosis.

Cancer Therapeutic Targeting of Hypoxia Induced Carbonic Anhydrase IX: From Bench to Bedside

Simple Summary

Tumor hypoxia remains a significant problem in the effective treatment of most cancers. Tumor cells within hypoxic niches tend to be largely resistant to most therapeutic modalities, and adaptation of the cells within the hypoxic microenvironment imparts the cells with aggressive, invasive behavior. Thus, a major goal of successful cancer therapy should be the eradication of hypoxic tumor cells. Carbonic Anhydrase IX (CAIX) is an exquisitely hypoxia induced protein, selectively expressed on hypoxic tumor cells, and thus has garnered significant attention as a therapeutic target. In this Commentary, we discuss the current status of targeting CAIX, and future strategies for effective, durable cancer treatment.

Abstract

Carbonic Anhydrase IX (CAIX) is a major metabolic effector of tumor hypoxia and regulates intra- and extracellular pH and acidosis. Significant advances have been made recently in the development of therapeutic targeting of CAIX. These approaches include antibody-based immunotherapy, as well as use of antibodies to deliver toxic and radioactive payloads. In addition, a large number of small molecule inhibitors which inhibit the enzymatic activity of CAIX have been described. In this commentary, we highlight the current status of strategies targeting CAIX in both the pre-clinical and clinical space, and discuss future perspectives that leverage inhibition of CAIX in combination with additional targeted therapies to enable effective, durable approaches for cancer therapy.

Intracellular pH-mediated induction of apoptosis in HeLa cells by a sulfonamide carbonic anhydrase inhibitor

Carbonic anhydrase IX (CAIX) is a hypoxia-associated transmembrane protein that is critical in the survival of cells. Because CAIX has a key role in pH regulation, its therapeutic effects have been heavily studied by different research laboratories. This study aims to investigate how a synthetic CAIX inhibitor triggers apoptosis in a cancer cell line, HeLa. In this regard, we investigated the effects of the compound I, synthesized as a CAIX inhibitor, on the survival of cancer cells. The compound I inhibited the proliferation of the CAIX+ HeLa cells, kept the cells in G0/G1 phase (74.7%) and altered the cells morphologies (AO/EtBr staining) and the nuclear structure (γ-H2AX staining). CAIX inhibition triggered apoptosis in HeLa cells with a rate of 47.4%. According to the expression of mediator genes (CASP-3, -8, -9, BAX, BCL-2, BECLIN, LC3), the both death pathways were activated in HeLa cells with the inhibition of CAIX with the compound I. The compound I was also determined to affect the genes and proteins that have a critical role in the regulation of apoptotic pathways (pro casp-3, cleaved casp-3, -8, -9, cleaved PARP and CAIX). Furthermore, CAIX inhibition caused changes in pH balance, disruption in organelle integrity of mitochondria, and increase intracellular reactive oxygen level of HeLa cells. Taken together, our findings suggest that CAIX inhibition has a potential in cancer treatment, and the compound I, a CAIX inhibitor, could be a promising therapeutic strategy in the treatment of aggressive tumours.

Perfusion-Based Bioreactor Culture and Isothermal Microcalorimetry for Preclinical Drug Testing with the Carbonic Anhydrase Inhibitor SLC-0111 in Patient-Derived Neuroblastoma

Neuroblastoma is a rare disease. Rare are also the possibilities to test new therapeutic options for neuroblastoma in clinical trials. Despite the constant need to improve therapy and outcomes for patients with advanced neuroblastoma, clinical trials currently only allow for testing few substances in even fewer patients. This increases the need to improve and advance preclinical models for neuroblastoma to preselect favorable candidates for novel therapeutics. Here we propose the use of a new patient-derived 3D slice-culture perfusion-based 3D model in combination with rapid treatment evaluation using isothermal microcalorimetry exemplified with treatment with the novel carbonic anhydrase IX and XII (CAIX/CAXII) inhibitor SLC-0111. Patient samples showed a CAIX expression of 18% and a CAXII expression of 30%. Corresponding with their respective CAIX expression patterns, the viability of SH-EP cells was significantly reduced upon treatment with SLC-0111, while LAN1 cells were not affected. The inhibitory effect on SH-SY5Y cells was dependent on the induction of CAIX expression under hypoxia. These findings corresponded to thermogenesis of the cells. Patient-derived organotypic slice cultures were treated with SLC-0111, which was highly effective despite heterogeneity of CAIX/CAXII expression. Thermogenesis, in congruence with the findings of the histological observations, was significantly reduced in SLC-0111-treated samples. In order to extend the evaluation time, we established a perfusion-based approach for neuroblastoma tissue in a 3D perfusion-based bioreactor system. Using this system, excellent tissue quality with intact tumor cells and stromal structure in neuroblastoma tumors can be maintained for 7 days. The system was successfully used for consecutive drug response monitoring with isothermal microcalorimetry. The described approach for drug testing, relying on an advanced 3D culture system combined with a rapid and highly sensitive metabolic assessment, can facilitate development of personalized treatment strategies for neuroblastoma.

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.

Characterization of the Safety Profile of Sweet Chestnut Wood Distillate Employed in Agriculture

In organic agriculture, synthetic pesticides and treatments are substituted by natural remedies with interesting success for product yield and environmental outcomes, but the safety of these bio-based products needs to be assessed in vertebrate and human models. Therefore, in this paper we assessed the safety profile of sweet chestnut (Castanea sativa) wood distillate (WD) on the different cellular components of tissues implied in transcutaneous absorption. We investigated the viability of different cell lines mimicking the skin (HaCaT keratinocytes), mucosa (A431), connective (normal human dermal fibroblasts, NHDF) and vascular (human umbilical vein endothelial cells, HUVEC) tissues after exposure to increasing concentrations (0.04–0.5%, v/v, corresponding to 1:2800–1:200 dilutions) of WD. A short exposure to increasing doses of WD was well tolerated up to the highest concentration. Instead, following a prolonged treatment, a concentration dependent cytotoxic effect was observed. Notably, a different behavior was found with the various cell lines, with higher sensitivity to cytotoxicity by the cells with higher proliferation rate and reduced doubling time (human keratinocytes). Moreover, to exclude an inflammatory effect at the not cytotoxic WD concentrations, the expression of the main inducible markers of inflammation, cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1), were assessed, and no improvement was found both after brief and prolonged exposure. In conclusion, our data exclude any inflammatory and cytotoxic effect at the lowest WD concentrations, namely 0.07% and 0.04%, mimicking some recommended dilutions of the product and the potential exposure doses for the operators in agriculture. Nevertheless, higher concentrations showed a safe profile for short time usage, but caution should be used by farmers following persistent product exposure.

Inhibition of Carbonic Anhydrase IX Suppresses Breast Cancer Cell Motility at the Single-Cell Level

Protein Carbonic Anhydrase IX (CA IX), which is expressed in various hypoxic solid tumors in order to maintain proper pH, is also related to cancer cell adhesion, invasion, and metastasis processes. Here, we investigated whether CA IX inhibition by a highly CA IX selective agent benzenesulfonamide VD11-4-2 triggers changes in individual cell motility. We seeded breast cancer cells on an extracellular matrix-coated glass-bottomed dish and in a microfluidic device with a gradient flow of epidermal growth factor (EGF), tracked individual cell movement, calculated their migration speeds, and/or followed movement direction. Our results showed that the inhibitor VD11-4-2 decreased the speed of CA IX positive breast cancer cells by 20-26% while not affecting non-cancerous cell migration. The inhibitor suppressed the cell migration velocity increment and hindered cells from reaching their maximum speed. VD11-4-2 also reduced CA IX, expressing cell movement towards the growth factor as a chemoattractant. Such a single cell-based migration assay enabled the comprehensive investigation of the cell motility and revealed that VD11-4-2 shows the ability to suppress breast cancer cell migration at a lower concentration than previously tested CA IX inhibitors.

Reconsidering anion inhibitors in the general context of drug design studies of modulators of activity of the classical enzyme carbonic anhydrase

Inorganic anions inhibit the metalloenzyme carbonic anhydrase (CA, EC 4.2.1.1) generally by coordinating to the active site metal ion. Cyanate was reported as a non-coordinating CA inhibitor but those erroneous results were subsequently corrected by another group. We review the anion CA inhibitors (CAIs) in the more general context of drug design studies and the discovery of a large number of inhibitor classes and inhibition mechanisms, including zinc binders (sulphonamides and isosteres, dithiocabamates and isosteres, thiols, selenols, benzoxaboroles, ninhydrins, etc.); inhibitors anchoring to the zinc-coordinated water molecule (phenols, polyamines, sulfocoumarins, thioxocoumarins, catechols); CAIs occluding the entrance to the active site (coumarins and derivatives, lacosamide), as well as compounds that bind outside the active site. All these new chemotypes integrated with a general procedure for obtaining isoform-selective compounds (the tail approach) has resulted, through the guidance of rigorous X-ray crystallography experiments, in the development of highly selective CAIs for all human CA isoforms with many pharmacological applications.

Inhibition of Carbonic Anhydrase IX Promotes Apoptosis through Intracellular pH Level Alterations in Cervical Cancer Cells

Carbonic anhydrase IX (CAIX) is a hypoxia-related protein that plays a role in proliferation in solid tumours. However, how CAIX increases proliferation and metastasis in solid tumours is unclear. The objective of this study was to investigate how a synthetic CAIX inhibitor triggers apoptosis in the HeLa cell line. The intracellular effects of CAIX inhibition were determined with AO/EB, AnnexinV-PI, and γ-H2AX staining; measurements of intracellular pH (pHi), reactive oxygen species (ROS), and mitochondrial membrane potential (MMP); and analyses of cell cycle, apoptotic, and autophagic modulator gene expression (Bax, Bcl-2, caspase-3, caspase-8, caspase-9, caspase-12, Beclin, and LC3), caspase protein level (pro-caspase 3 and cleaved caspase-3, -8, -9), cleaved PARP activation, and CAIX protein level. Sulphonamide CAIX inhibitor E showed the lowest IC50 and the highest selectivity index in CAIX-positive HeLa cells. CAIX inhibition changed the morphology of HeLa cells and increased the ratio of apoptotic cells, dramatically disturbing the homeostasis of intracellular pHi, MMP and ROS levels. All these phenomena consequent to CA IX inhibition triggered apoptosis and autophagy in HeLa cells. Taken together, these results further endorse the previous findings that CAIX inhibitors represent an important therapeutic strategy, which is worth pursuing in different cancer types, considering that presently only one sulphonamide inhibitor, SLC-0111, has arrived in Phase Ib/II clinical trials as an antitumour/antimetastatic drug.

Phenotypic Heterogeneity of Triple-Negative Breast Cancer Mediated by Epithelial-Mesenchymal Plasticity

Triple-negative breast cancer (TNBC) is a subtype of breast carcinoma known for its unusually aggressive behavior and poor clinical outcome. Besides the lack of molecular targets for therapy and profound intratumoral heterogeneity, the relatively quick overt metastatic spread remains a major obstacle in effective clinical management. The metastatic colonization of distant sites by primary tumor cells is affected by the microenvironment, epigenetic state of particular subclones, and numerous other factors. One of the most prominent processes contributing to the intratumoral heterogeneity is an epithelial-mesenchymal transition (EMT), an evolutionarily conserved developmental program frequently hijacked by tumor cells, strengthening their motile and invasive features. In response to various intrinsic and extrinsic stimuli, malignant cells can revert the EMT state through the mesenchymal-epithelial transition (MET), a process that is believed to be critical for the establishment of macrometastasis at secondary sites. Notably, cancer cells rarely undergo complete EMT and rather exist in a continuum of E/M intermediate states, preserving high levels of plasticity, as demonstrated in primary tumors and, ultimately, in circulating tumor cells, representing a simplified element of the metastatic cascade. In this review, we focus on cellular drivers underlying EMT/MET phenotypic plasticity and its detrimental consequences in the context of TNBC cancer.

Tissue Expression of Carbonic Anhydrase IX Correlates to More Aggressive Phenotype of Basal Cell Carcinoma

Basal cell carcinoma (BCC) is the most common cancer in the white-skinned population accounting for about 15% of all neoplasms. Its incidence is increasing worldwide, at a rate of about 10% per year. BCC, although infrequently metastasizing, very often causes extensive tissue losses, due to the high propensity toward stromal infiltration, particularly in its dedifferentiated forms, with disfiguring and debilitating results. To date, there still is limited availability of therapeutic treatments alternative to surgery. We evaluated the immunohistochemical expression of the carbonic anhydrase IX (CAIX), one of the main markers of tissue hypoxia, in a set of 85 archived FFPE BCC tissues, including the main subtypes, with different clinical outcomes, to demonstrate a possible relationship between hypoxic phenotype and biological aggressiveness of these neoplasms. Our results showed that the expression level of the CAIX protein contributes to the stratification of BCC in the different risk classes for recurrence. We hypothesize for CAIX a potential therapeutic role as a target therapy in the treatment of more aggressive BCCs, thus providing an alternative to surgical and pharmacological therapy with Hedgehog inhibitors, a promising example of target therapy in BCCs.

A Novel Inhibitor of Carbonic Anhydrases Prevents Hypoxia-Induced TNBC Cell Plasticity

Cell plasticity is the ability that cells have to modify their phenotype, adapting to the environment. Cancer progression is under the strict control of the the tumor microenvironment that strongly determines its success by regulating the behavioral changes of tumor cells. The cross-talk between cancer and stromal cells and the interactions with the extracellular matrix, hypoxia and acidosis contribute to trigger a new tumor cell identity and to enhance tumor heterogeneity and metastatic spread. In highly aggressive triple-negative breast cancer, tumor cells show a significant capability to change their phenotype under the pressure of the hypoxic microenvironment. In this study, we investigated whether targeting the hypoxia-induced protein carbonic anhydrase IX (CA IX) could reduce triple-negative breast cancer (TNBC) cell phenotypic switching involved in processes associated with poor prognosis such as vascular mimicry (VM) and cancer stem cells (CSCs). The treatment of two TNBC cell lines (BT-549 and MDA-MB-231) with a specific CA IX siRNA or with a novel inhibitor of carbonic anhydrases (RC44) severely impaired their ability to form a vascular-like network and mammospheres and reduced their metastatic potential. In addition, the RC44 inhibitor was able to hamper the signal pathways involved in triggering VM and CSC formation. These results demonstrate that targeting hypoxia-induced cell plasticity through CA IX inhibition could be a new opportunity to selectively reduce VM and CSCs, thus improving the efficiency of existing therapies in TNBC.

Carbonic Anhydrase Inhibitors Targeting Metabolism and Tumor Microenvironment

The tumor microenvironment is crucial for the growth of cancer cells, triggering particular biochemical and physiological changes, which frequently influence the outcome of anticancer therapies. The biochemical rationale behind many of these phenomena resides in the activation of transcription factors such as hypoxia-inducible factor 1 and 2 (HIF-1/2). In turn, the HIF pathway activates a number of genes including those involved in glucose metabolism, angiogenesis, and pH regulation. Several carbonic anhydrase (CA, EC 4.2.1.1) isoforms, such as CA IX and XII, actively participate in these processes and were validated as antitumor/antimetastatic drug targets. Here, we review the field of CA inhibitors (CAIs), which selectively inhibit the cancer-associated CA isoforms. Particular focus was on the identification of lead compounds and various inhibitor classes, and the measurement of CA inhibitory on-/off-target effects. In addition, the preclinical data that resulted in the identification of SLC-0111, a sulfonamide in Phase Ib/II clinical trials for the treatment of hypoxic, advanced solid tumors, are detailed.