Carbonic anhydrase IX (CA9) modulates tumor-associated cell migration and invasion

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.

How protons pave the way to aggressive cancers

Cancers undergo sequential changes to proton (H+) concentration and sensing that are consequences of the disease and facilitate its further progression. The impact of protonation state on protein activity can arise from alterations to amino acids or their titration. Indeed, many cancer-initiating mutations influence pH balance, regulation or sensing in a manner that enables growth and invasion outside normal constraints as part of oncogenic transformation. These cancer-supporting effects become more prominent when tumours develop an acidic microenvironment owing to metabolic reprogramming and disordered perfusion. The ensuing intracellular and extracellular pH disturbances affect multiple aspects of tumour biology, ranging from proliferation to immune surveillance, and can even facilitate further mutagenesis. As a selection pressure, extracellular acidosis accelerates disease progression by favouring acid-resistant cancer cells, which are typically associated with aggressive phenotypes. Although acid-base disturbances in tumours often occur alongside hypoxia and lactate accumulation, there is now ample evidence for a distinct role of H+-operated responses in key events underpinning cancer. The breadth of these actions presents therapeutic opportunities to change the trajectory of disease.

Downregulation of HHLA2 inhibits ovarian cancer progression via the NF-κB signaling pathway and suppresses the expression of CA9

HHLA2 has been recently demonstrated to play multifaceted roles in several types of cancers. However, its underlying mechanism in the progression of human ovarian cancer (OC) remains largely unexplored. In the present study, we aimed to determine whether downregulation of HHLA2 inhibited malignant phenotypes of human OC cells and explore its specific mechanism. Our results revealed that downregulation of HHLA2 by transfection with a lentiviral vector significantly suppressed the viability, invasion, and migration of OC cells. Interaction study showed that downregulation of HHLA2 in OC cells reduced the expression of CA9 and increased the expressions of p-IKKβ and p-RelA. Conversely, the viability, invasion, and migration of HHLA2-depleted OC cells were increased when CA9 was upregulated. In vivo, we found that downregulation of HHLA2 significantly inhibited tumor growth, which was reversed by CA9 overexpression. In addition, downregulation of HHLA2 inhibited the OC progression via activating the NF-κB signaling pathway and decreasing the expression of CA9. Collectively, our data suggested a link between HHLA2 and NF-κB axis in the pathogenesis of OC, and these findings might provide valuable insights into the development of novel potential therapeutic targets for OC.

Effects of Large Extracellular Vesicles from Kidney Cancer Patients on the Growth and Environment of Renal Cell Carcinoma Xenografts in a Mouse Model

Plasma membrane-derived vesicles, also referred to as large extracellular vesicles (lEVs), are implicated in several pathophysiological situations, including cancer. However, to date, no studies have evaluated the effects of lEVs isolated from patients with renal cancer on the development of their tumors. In this study, we investigated the effects of three types of lEVs on the growth and peritumoral environment of xenograft clear cell renal cell carcinoma in a mouse model. Xenograft cancer cells were derived from patients' nephrectomy specimens. Three types of lEVs were obtained from pre-nephrectomy patient blood (cEV), the supernatant of primary cancer cell culture (sEV) and from blood from individuals with no medical history of cancer (iEV). Xenograft volume was measured after nine weeks of growth. Xenografts were then removed, and the expression of CD31 and Ki67 were evaluated. We also measured the expression of MMP2 and Ca9 in the native mouse kidney. lEVs from kidney cancer patients (cEV and sEV) tend to increase the size of xenografts, a factor that is related to an increase in vascularization and tumor cell proliferation. cEV also altered organs that were distant from the xenograft. These results suggest that lEVs in cancer patients are involved in both tumor growth and cancer progression.

Carbonic Anhydrase IX Controls Vulnerability to Ferroptosis in Gefitinib-Resistant Lung Cancer

Acquired resistance to epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKI, such as gefitinib) in lung cancer continues to be a major problem. Recent studies have shown the promise of ferroptosis-inducing therapy in EGFR-TKI resistant cancer, but have not been translated into clinical benefits. Here, we identified carbonic anhydrase IX (CA9) was upregulated in gefitinib-resistant lung cancer. Then we measured the cell viability, intracellular reactive oxygen species (ROS) levels, and labile iron levels after the treatment of ferroptosis inducer erastin. We found that CA9 confers resistance to ferroptosis-inducing drugs. Mechanistically, CA9 is involved in the inhibition of transferrin endocytosis and the stabilization of ferritin, leading to resistance to ferroptosis. Targeting CA9 promotes iron uptake and release, thus triggering gefitinib-resistant cell ferroptosis. Notably, CA9 inhibitor enhances the ferroptosis-inducing effect of cisplatin on gefitinib-resistant cells, thus eliminating resistant cells in heterogeneous tumor tissues. Taken together, CA9-targeting therapy is a promising approach to improve the therapeutic effect of gefitinib-resistant lung cancer by inducing ferroptosis.

Carbonic Anhydrase IX Expression and Treatment Response Measured in Rectal Adenocarcinoma Following Neoadjuvant Chemo-Radiotherapy

The overexpression of the pH regulator carbonic anhydrase IX (CAIX) due to hypoxic/metabolic stress was reported in various tumors as an adverse prognostic feature. Our retrospective study aimed to investigate the general pattern and dynamics of CAIX expression in rectal adenocarcinoma following preoperative neoadjuvant therapy (NAT) in matched initial biopsy and surgical resection samples. A total of 40/55 (72.72%) of the post-treatment samples showed partial CAIX expression, frequently in the proximity of hypoxic tumor areas. CAIX expression showed a significant increase in post-treatment tumors (mean% 21.8 ± 24.9 SD vs. 39.4 ± 29.4 SD, p < 0.0001), that was not obvious in untreated tumors (mean% 15.0 ± 21.3 SD vs. 20 ± 23.02, p = 0.073). CAIXhigh phenotype was associated with mutant KRAS status and lack of pathological regression (WHO Tumor Regression Grade 4 and 5). However, the adverse effect of CAIX on overall or progression-free survival could not be statistically confirmed. In conclusion, the dynamic upregulation of CAIX expression is a general feature of rectal adenocarcinoma following neoadjuvant chemo-radiotherapy indicating therapy-induced metabolic reprogramming and cellular adaptation. A synergism of the CAIX-associated regulatory pathways and the mutant KRAS oncogenic signaling most likely contributes to therapy resistance and survival of residual cancer.

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.

Randomized multicenter phase II trial of prophylactic irradiation of para-aortic lymph nodes in advanced cervical cancer according to tumor hypoxia: Korean Radiation Oncology Group (KROG 07-01) study

We conducted a prospective phase II study on whether extended-field irradiation (EFI) confers survival benefits depending on hypoxic markers in locally advanced uterine cervical cancer (LAUCC). RNA-seq was performed to identify immune and hypoxic gene signatures. A total of 288 patients were randomized to either EFI or pelvic radiotherapy (PRT). All patients completed chemoradiotherapy. Overall, significantly higher 5-year para-aortic recurrence free survival (PARFS) rate occurred in EFI (97.6%) than in PRT group (87.2%), with marginal tendency to improve disease-free survival (DFS; 78% vs 70%, P = .066). Subgroup analyses were performed based on carbonic anhydrase 9 (CA9)-only positive, CA9/hypoxia-inducible factor (HIF) double positive and CA9 negative. In the CA9-only positive, EFI successfully increased 5-year PARFS (100% vs 76.4%, P = .010), resulting in significantly improved long-term DFS (85.7% vs 54.7%, P = .023) compared to the PRT, while there was no such benefit of EFI in the CA9/HIFs double positive. RNA-seq analysis identified distinct immunehigh subgroup with negative correlation with hypoxia gene signatures (R = -.37, P < .01), which showed a higher 5-year DFS than the immunelow (P = .032). Hypoxia-related genes were upregulated in the CA9/HIFs double positive compared to CA9 negative (P < .05). Only 17.4% of patients in CA9-negative group showed immunelow signatures, while 40.0% of patients in the double-positive group exhibited immunelow signatures. In conclusion, EFI improved PARFS significantly in all patients, but therapeutic efficacy of EFI in terms of improved DFS was solely observed in CA9-only positive LAUCC, and not in CA9/HIFs double-positive subgroup. RNA-seq analysis suggested that hypoxia-induced immunosuppression may be related to treatment resistance in LAUCC.

Development of a ferroptosis-based model to predict prognosis, tumor microenvironment, and drug response for lung adenocarcinoma with weighted genes co-expression network analysis

Objective: The goal of this study was to create a risk model based on the ferroptosis gene set that affects lung adenocarcinoma (LUAD) patients' prognosis and to investigate the potential underlying mechanisms. Material and Methods: A cohort of 482 LUAD patients from the TCGA database was used to develop the prognostic model. We picked the module genes from the ferroptosis gene set using weighted genes co-expression network analysis (WGCNA). The least absolute shrinkage and selection operator (LASSO) and univariate cox regression were used to screen the hub genes. Finally, the multivariate Cox analysis constructed a risk prediction score model. Three other cohorts of LUAD patients from the GEO database were included to validate the prediction ability of our model. Furthermore, the differentially expressed genes (DEG), immune infiltration, and drug sensitivity were analyzed. Results: An eight-gene-based prognostic model, including PIR, PEBP1, PPP1R13L, CA9, GLS2, DECR1, OTUB1, and YWHAE, was built. The patients from the TCGA database were classified into the high-RS and low-RS groups. The high-RS group was characterized by poor overall survival (OS) and less immune infiltration. Based on clinical traits, we separated the patients into various subgroups, and RS had remarkable prediction performance in each subgroup. The RS distribution analysis demonstrated that the RS was significantly associated with the stage of the LUAD patients. According to the study of immune cell infiltration in both groups, patients in the high-RS group had a lower abundance of immune cells, and less infiltration was associated with worse survival. Besides, we discovered that the high-RS group might not respond well to immune checkpoint inhibitors when we analyzed the gene expression of immune checkpoints. However, drug sensitivity analysis suggested that high-RS groups were more sensitive to common LUAD agents such as Afatinib, Erlotinib, Gefitinib, and Osimertinib. Conclusion: We constructed a novel and reliable ferroptosis-related model for LUAD patients, which was associated with prognosis, immune cell infiltration, and drug sensitivity, aiming to shed new light on the cancer biology and precision medicine.

Metabolic Symbiosis-Blocking Nano-Combination for Tumor Vascular Normalization Treatment

The clinical anti-vascular endothelial growth factor (anti-VEGF) drugs and metronomic chemotherapy (MET) induced tumor vascular normalization treatment (TVNT) are easily antagonized by tumor microenvironment metabolic cross-talk between tumor cells and endothelial cells (ECs). To overcome this dilemma, nanodrug with the ability of ECs targeted glycolysis inhibition and nanodrug with the ability of tumor cell glycolysis inhibition, anti-VEGF, and MET are combined to prepare Nano-combination the pathways related to angiogenesis, tumor cell proliferation, and immunosuppression and breaking the negative sugar-lipid-protein metabolism balance in tumor microenvironment. Thus, stronger and more lasting normalized tumor vascular network and remarkable antitumor efficacy are obtained after treatment, constructing a positive feedback loop between TVNT and anti-tumor therapy. Above all, this study provides a new insight for solving the bottleneck of clinical TVNT.

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.

Proton export upregulates aerobic glycolysis

INTRODUCTION

Aggressive cancers commonly ferment glucose to lactic acid at high rates, even in the presence of oxygen. This is known as aerobic glycolysis, or the "Warburg Effect." It is widely assumed that this is a consequence of the upregulation of glycolytic enzymes. Oncogenic drivers can increase the expression of most proteins in the glycolytic pathway, including the terminal step of exporting H+ equivalents from the cytoplasm. Proton exporters maintain an alkaline cytoplasmic pH, which can enhance all glycolytic enzyme activities, even in the absence of oncogene-related expression changes. Based on this observation, we hypothesized that increased uptake and fermentative metabolism of glucose could be driven by the expulsion of H+ equivalents from the cell.

RESULTS

To test this hypothesis, we stably transfected lowly glycolytic MCF-7, U2-OS, and glycolytic HEK293 cells to express proton-exporting systems: either PMA1 (plasma membrane ATPase 1, a yeast H+-ATPase) or CA-IX (carbonic anhydrase 9). The expression of either exporter in vitro enhanced aerobic glycolysis as measured by glucose consumption, lactate production, and extracellular acidification rate. This resulted in an increased intracellular pH, and metabolomic analyses indicated that this was associated with an increased flux of all glycolytic enzymes upstream of pyruvate kinase. These cells also demonstrated increased migratory and invasive phenotypes in vitro, and these were recapitulated in vivo by more aggressive behavior, whereby the acid-producing cells formed higher-grade tumors with higher rates of metastases. Neutralizing tumor acidity with oral buffers reduced the metastatic burden.

CONCLUSIONS

Therefore, cancer cells which increase export of H+ equivalents subsequently increase intracellular alkalization, even without oncogenic driver mutations, and this is sufficient to alter cancer metabolism towards an upregulation of aerobic glycolysis, a Warburg phenotype. Overall, we have shown that the traditional understanding of cancer cells favoring glycolysis and the subsequent extracellular acidification is not always linear. Cells which can, independent of metabolism, acidify through proton exporter activity can sufficiently drive their metabolism towards glycolysis providing an important fitness advantage for survival.

Carbonic anhydrase IX proteoglycan-like and intracellular domains mediate pulmonary microvascular endothelial cell repair and angiogenesis

The lungs of patients with acute respiratory distress syndrome (ARDS) have hyperpermeable capillaries that must undergo repair in an acidic microenvironment. Pulmonary microvascular endothelial cells (PMVECs) have an acid-resistant phenotype, in part due to carbonic anhydrase IX (CA IX). CA IX also facilitates PMVEC repair by promoting aerobic glycolysis, migration, and network formation. Molecular mechanisms of how CA IX performs such a wide range of functions are unknown. CA IX is comprised of four domains known as the proteoglycan-like (PG), catalytic (CA), transmembrane (TM), and intracellular (IC) domains. We hypothesized that the PG and CA domains mediate PMVEC pH homeostasis and repair, and the IC domain regulates aerobic glycolysis and PI3k/Akt signaling. The functions of each CA IX domain were investigated using PMVEC cell lines that express either a full-length CA IX protein or a CA IX protein harboring a domain deletion. We found that the PG domain promotes intracellular pH homeostasis, migration, and network formation. The CA and IC domains mediate Akt activation but negatively regulate aerobic glycolysis. The IC domain also supports migration while inhibiting network formation. Finally, we show that exposure to acidosis suppresses aerobic glycolysis and migration, even though intracellular pH is maintained in PMVECs. Thus, we report that 1) The PG and IC domains mediate PMVEC migration and network formation, 2) the CA and IC domains support PI3K/Akt signaling, and 3) acidosis impairs PMVEC metabolism and migration independent of intracellular pH homeostasis.

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.

Epigenetic mechanisms in metal carcinogenesis

Many metals exhibit genotoxic and/or carcinogenic effects. These toxic metals can be found ubiquitously - in drinking water, food, air, general use products, in everyday and occupational settings. Exposure to such carcinogenic metals can result in serious health disorders, including cancer. Arsenic, cadmium, chromium, nickel, and their compounds have already been recognized as carcinogens by the International Agency for Research on Cancer. This review summarizes a wide range of epigenetic mechanisms contributing to carcinogenesis induced by these metals, primarily including, but not limited to, DNA methylation, miRNA regulation, and histone posttranslational modifications. The mechanisms are described and discussed both from a metal-centric and a mechanism-centric standpoint. The review takes a broad perspective, putting the mechanisms in the context of real-life exposure, and aims to assist in guiding future research, particularly with respect to the assessment and control of exposure to carcinogenic metals and novel therapy development.

Together Intra-Tumor Hypoxia and Macrophagic Immunity Are Driven Worst Outcome in Pediatric High-Grade Osteosarcomas

Simple Summary

Radiological and immunohistochemical data were correlated with the outcome in a retrospective monocentric cohort of 30 pediatric osteosarcomas (OTS). A necrotic volume of more than 50 cm³ at diagnosis was significantly linked to a worse overall survival (OS). Regarding immunohistochemical analyses, an overexpression of hypoxic markers, such as HIF-1α and anhydrase carbonic IX (CAIX), was significantly linked to a worse OS, while pS6-RP hyperexpression was correlated with a better survival. We also featured that CD68 positive cells, representative of macrophagic M1 polarization, were mostly associated with HIF-1α and CAIX hyperexpressions and that M2-like polarization, mostly related to CD163 positivity, was correlated to mTor activation. These findings, involving clinical, radiological and biology data, allowed us to hypothesize a dual signature association ready to use routinely in future protocols.

Abstract

Background: Osteosarcomas (OTS) represent the most common primary bone cancer diagnosed in adolescents and young adults. Despite remarkable advances, there are no objective molecular or imaging markers able to predict an OTS outcome at diagnosis. Focusing on biomarkers contributing broadly to treatment resistance, we examine the interplay between the tumor-associated macrophages and intra-tumor hypoxia. Methods: Radiological and immunohistochemical (IHC) data were correlated with the outcome in a retrospective and monocentric cohort of 30 pediatric OTS. We studied hypoxic (pS6, phospho-mTor, HIF-1α and carbonic anhydrase IX (CAIX)) and macrophagic (CD68 and CD163) biomarkers. Results: The imaging analyses were based on MRI manual volumetric measures on axial post-contrast T1 weighted images, where, for each tumor, we determined the necrotic volume and its ratio to the entire tumor volume. When they were above 50 cm³ and 20%, respectively, they correlated with a worse overall survival (p = 0.0072 and p = 0.0136, respectively) and event-free survival (p = 0.0059 and p = 0.0143, respectively). IHC assessments enable a significant statistical link between HIF-1α/CAIX hyper-expressions, CD68+ cells and a worse outcome, whereas activation of mTor pathway was linked to a better survival rate and CD163+ cells. Conclusions: This study evidenced the links between hypoxia and immunity in OTS, as their poor outcome may be related to a larger necrotic volume on diagnostic MRI and, in biopsies, to a specific IHC profile.

[Immunohistochemical analysis of a hypoxia-associated signature in melanomas with positive and negative sentinel lymph nodes : Hypoxia-associated signature of primary cutaneous melanomas]

Metabolic reprogramming mediated by hypoxia-inducible factors and its downstream targets plays a crucial role in many human malignancies. Excessive proliferation of tumor cells under hypoxic conditions leads to metabolic reprogramming and altered gene expression enabling tumors to adapt to their hypoxic environment. Here we analyzed the metabolic signatures of primary cutaneous melanomas with positive and negative sentinel node status in order to evaluate potential differences in their metabolic signature. We found a positive correlation of the expression of glucose transporter 1 (GLUT-1) with tumor thickness and ulceration in all melanomas with subgroup analyses as well as in the subgroup with a negative sentinel node. Furthermore, the expression of vascular endothelial growth factor (VEGF) was positively correlated with the presence of ulceration in melanomas with positive sentinel node.

Dual roles of AMAP1 in the transcriptional regulation and intracellular trafficking of carbonic anhydrase IX

BACKGROUND

The cell-surface enzyme carbonic anhydrase IX (CAIX/CA9) promotes tumor growth, survival, invasion, and metastasis, mainly via its pH-regulating functions. Owing to its tumor-specific expression, CAIX-targeting antibodies/chemicals are utilized for therapeutic and diagnostic purposes. However, mechanisms of CAIX trafficking, which affects such CAIX-targeting modalities remain unclear. In this study, roles of the AMAP1-PRKD2 pathway, which mediates integrin recycling of invasive cancer cells, in CAIX trafficking were investigated.

METHODS

Using highly invasive MDA-MB-231 breast cancer cells, the physical association and colocalization of endogenous proteins were analyzed by immunoprecipitation and immunofluorescence, protein/mRNA levels were quantified by western blotting/qPCR, and cell-surface transport and intracellular/extracellular pH regulation were measured by biotin-labeling and fluorescent dye-based assays, respectively. The correlation between mRNA levels and patients' prognoses was analyzed using a TCGA breast cancer dataset.

RESULTS

AMAP1 associated with the CAIX protein complex, and they colocalized at the plasma membrane and tubulovesicular structures. AMAP1 knockdown reduced total/surface CAIX, induced its lysosomal accumulation and degradation, and affected intracellular/extracellular pH. PRKD2 knockdown excluded AMAP1 from the CAIX complex and reduced total CAIX in a lysosome-dependent manner. Unexpectedly, AMAP1 knockdown also reduced CAIX mRNA. AMAP1 interacted with PIAS3, which stabilizes HIF-1α, a transcriptional regulator of CA9. AMAP1 knockdown inhibited the PIAS3-HIF-1α interaction and destabilized the HIF-1α protein. High-ASAP1 (AMAP1-encoding gene) together with high-PIAS3 correlated with high-CA9 and an unfavorable prognosis in breast cancer.

CONCLUSION

The AMAP1-PRKD2 pathway regulates CAIX trafficking, and modulates its total/surface expression. The AMAP1-PIAS3 interaction augments CA9 transcription by stabilizing HIF-1α, presumably contributing to an unfavorable prognosis.

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.

Expression of Alternative Splice Variants of 6-Phosphofructo-2-kinase/Fructose-2,6-bisphosphatase-4 in Normoxic and Hypoxic Melanoma Cells

Cancer-specific isoenzyme of phosphofructokinase II (PFKFB4), as our previous research has shown, may be one of the most important enzymes contributing to the intensification of glycolysis in hypoxic malignant melanoma cells. Although the PFKFB4 gene seems to play a crucial role in the progression of melanoma, so far there are no complete data on the expression of PFKFB4 at the isoform level and the influence of hypoxia on alternative splicing. Using RT-qPCR and semi-quantitative RT-PCR, we presented the PFKFB4 gene expression profile at the level of six isoforms described in the OMIM NCBI database in normoxic and hypoxic melanoma cells. Additionally, using VMD software, we analyzed the structure of isoforms at the protein level, concluding about the catalytic activity of individual isoforms. Our research has shown that five isoforms of PFKFB4 are expressed in melanoma cells, of which the D and F isoforms are highly constitutive, while the canonical B isoform seems to be the main isoform induced in hypoxia. Our results also indicate that the expression profile at the level of the PFKFB4 gene does not reflect the expression at the level of individual isoforms. Our work clearly indicates that the PFKFB4 gene expression profile should be definitely analyzed at the level of individual isoforms. Moreover, the analysis at the protein level allowed the selection of those isoforms whose functional validation should be performed to fully understand the importance of PFKFB4 expression in the metabolic adaptation of malignant melanoma cells.

The association of transcription factor Prox1 with the proliferation, migration, and invasion of lung cancer

Background

The current study investigates the effect of transcription factor Prox1 on the proliferation, migration, and invasion ability of lung cancer.

Methods

Lung cancer cell lines (A549 and H446 cells) were transfected with Prox1NAD and siRNA, respectively. Thus, the A549 and H446 cells overexpressed Prox1 after transfection of Prox1NAD plasmids, and A549 and H446 cells have low expression of Prox1 after transfection with siRNA. Reverse transcriptase quantitative PCR and western blot analyses were used to detect Prox1 mRNA and protein expression in cells. Plate clone formation experiments and MTT experiments were used to detect cell proliferation. Western blot was used to detect the expression of Rho family-related proteins in cells.

Results

Compared to untransfected wild-type A549 and H446 that served as blank controls, the expression level of Prox1mRNA and protein in A549 and H446 cells overexpressing Prox1 after plasmid transfection was high, while the expression level of Prox1mRNA and protein in A549 and H446 cells with low expression of Prox1 after siRNA transfection was low. With the increase of Prox1 expression, the expression of RhoA and RhoC increased, while the expression of RhoB decreased.

Conclusion

The finding of this study may provide a new approach for the treatment of lung cancer using targeted gene therapy.

Carbonic Anhydrase IX Promotes Human Cervical Cancer Cell Motility by Regulating PFKFB4 Expression

Simple Summary

Carbonic anhydrase IX (CAIX) is a hypoxia-induced protein that is highly expressed in numerous human cancers. However, the molecular mechanisms involved in CAIX and human cervical cancer metastasis remain poorly understood. Our study found that CAIX overexpression increases PFKFB4 expression and EMT, promoting cervical cancer cell migration. CAIX could contribute to cervical cancer cell metastasis and its inhibition could be a cervical cancer treatment strategy.

Abstract

Carbonic anhydrase IX (CAIX) is a hypoxia-induced protein that is highly expressed in numerous human cancers. However, the molecular mechanisms involved in CAIX and human cervical cancer metastasis remain poorly understood. In this study, CAIX overexpression in SiHa cells increased cell migration and epithelial-to-mesenchymal transition (EMT). Silencing CAIX in the Caski cell line decreased the motility of cells and EMT. Furthermore, the RNA-sequencing analysis identified a target gene, bifunctional 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB4), which is influenced by CAIX overexpression and knockdown. A positive correlation was found between CAIX expression and PFKFB4 levels in the cervical cancer of the TCGA database. Mechanistically, CAIX overexpression activated the phosphorylation of extracellular signal-regulated kinases (ERKs) to induce EMT and promote cell migration. In clinical results, human cervical cancer patients with CAIX^high/PFKFB4^high expression in the late stage had higher rates of lymph node metastasis and the shortest survival time. Our study found that CAIX overexpression increases PFKFB4 expression and EMT, promoting cervical cancer cell migration. CAIX could contribute to cervical cancer cell metastasis and its inhibition could be a cervical cancer treatment strategy.

Carbonic anhydrase IX: a regulator of pH and participant in carcinogenesis

Carbonic anhydrase IX (CAIX) is a transmembrane metalloenzyme which is upregulated in tumour cells under hypoxic conditions. CAIX expression is induced by the accumulation of hypoxia-inducible factor-1α and has several downstream effects, including acidification of the extracellular pH, loss of cellular adhesion and increased tumour cell migration. CAIX is upregulated in a variety of solid organ tumours and has prognostic implications. High CAIX protein expression is a marker of poor prognosis in breast, lung, ovarian and bladder carcinomas. Conversely, low expression is an indicator of poor prognosis in clear cell renal cell carcinoma (CCRCC). CAIX immunohistochemistry is useful diagnostically to identify metastatic CCRCC, and the recently recognised clear cell papillary renal cell carcinoma. There is much interest in targeting CAIX with monoclonal antibodies and small molecule inhibitors. There are several small molecule inhibitors under development which have shown promising results in clinical trials. In this paper, we provide an overview of the role of CAIX in tumourigenesis and outline its use as a prognostic, diagnostic and therapeutic biomarker.

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.

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.

Surface engineering for efficient capture of circulating tumor cells in renal cell carcinoma: From nanoscale analysis to clinical application

Sensitive detection of circulating tumor cells (CTCs) from patients' peripheral blood facilitates on-demand monitoring of tumor progression. However, clinically significant capture of renal cell carcinoma CTCs (RCC-CTCs) remains elusive due to their heterogenous surface receptor expression. Herein, a novel capture platform is developed to detect RCC-CTCs through integration of dendrimer-mediated multivalent binding, a mixture of antibodies, and biomimetic cell rolling. The nanoscale binding kinetics measured using atomic force microscopy reveal that dendrimer-coated surfaces exhibit an order of magnitude enhancement in off-rate kinetics compared to surface without dendrimers, which translated into cell capture improvements by ~60%. Selectin-induced cell rolling facilitates surface recruitment of cancer cells, further improving cancer cell capture by up to 1.7-fold. Lastly, an antibody cocktail targeting four RCC-CTC surface receptors, which included epithelial cell adhesion molecule (EpCAM), carbonic anhydrase IX (CA9), epidermal growth factor receptor (EGFR), and hepatocyte growth factor receptor (c-Met), improves the capture of RCC cells by up to 80%. The optimal surface configuration outperforms the conventional assay solely relying on EpCAM, as demonstrated by detecting significantly more CTCs in patients' samples (9.8 ± 5.1 vs. 1.8 ± 2.0 CTCs mL-1). These results demonstrate that the newly engineered capture platform effectively detects RCC-CTCs for their potential use as tumor biomarkers.

How and Why Are Cancers Acidic? Carbonic Anhydrase IX and the Homeostatic Control of Tumour Extracellular pH

The acidic tumour microenvironment is now recognized as a tumour phenotype that drives cancer somatic evolution and disease progression, causing cancer cells to become more invasive and to metastasise. This property of solid tumours reflects a complex interplay between cellular carbon metabolism and acid removal that is mediated by cell membrane carbonic anhydrases and various transport proteins, interstitial fluid buffering, and abnormal tumour-associated vessels. In the past two decades, a convergence of advances in the experimental and mathematical modelling of human cancers, as well as non-invasive pH-imaging techniques, has yielded new insights into the physiological mechanisms that govern tumour extracellular pH (pH_e). In this review, we examine the mechanisms by which solid tumours maintain a low pH_e, with a focus on carbonic anhydrase IX (CAIX), a cancer-associated cell surface enzyme. We also review the accumulating evidence that suggest a role for CAIX as a biological pH-stat by which solid tumours stabilize their pH_e. Finally, we highlight the prospects for the clinical translation of CAIX-targeted therapies in oncology.

Metabolic reprogramming and angiogenesis in primary cutaneous Merkel cell carcinoma: expression of hypoxia-inducible factor-1α and its central downstream factors

BACKGROUND

Metabolic reprogramming and altered gene expression mediated by hypoxia-inducible factors play crucial roles during tumour growth and progression. Nevertheless, studies analysing the expression of hypoxia-inducible factor-1α and its downstream targets in Merkel cell carcinoma (MCC) are lacking but are warranted to shed more light on MCC pathogenesis and to potentially provide new therapeutic options.

OBJECTIVES

To analyse the immunohistochemical expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor-A (referred to as VEGF throughout the manuscript), VEGF receptor-2 (VEGFR-2), VEGF receptor-3 (VEGFR-3), glucose transporter-1 (Glut-1), monocarboxylate transporter 4 (MCT4) and carbonic anhydrase IX (CAIX) in primary cutaneous MCC.

METHODS

The 16 paraffin-embedded primary cutaneous MCCs (Merkel cell polyomavirus (McPyV) positive/negative: 11/5) were analysed by immunohistochemistry, namely HIF-1α, VEGF, VEGFR-2 (KDR), VEGFR-3 (FLT4), Glut-1, MCT4 and CAIX. An established quantification score (QS) was applied to quantitate the protein expression by considering the percentage of positive tumour cells (0: 0%; 1: up to 1%; 2: 2-10%; 3: 11-50%; 4: >50%) in relation to the staining intensity (0: negative; 1: low; 2: medium; 3: strong).

RESULTS

HIF-1α was expressed in all MCCs and predominantly found at the invading edges of tumour margins. The HIF-1α downstream factors Glut-1, MCT4 and CAIX were expressed in 13 of 16 MCC (81%), 14 of 16 MCC (88%) and 16 of 16 MCC (100%), respectively. Interestingly, VEGF and VEGFR-2 were not expressed in tumour cells, whereas VEGFR-3 was expressed in all MCCs. HIF-1α was expressed significantly stronger in McPyV⁺ tumours (QS: 10.36 ± 2.41) than in McPyV^- tumours (QS: 5.40 ± 1.34; P = 0.002). Similarly, VEGFR-3 was also expressed significantly stronger in McPyV⁺ tumours (QS: 10.00 ± 2.52) than in McPyV^- tumours (QS: 5.40 ± 3.43, P = 0.019).

CONCLUSIONS

Our data provide first evidence for a role of HIF-1α in induced metabolic reprogramming contributing to MCC pathogenesis. The metabolic signatures of McPyV⁺ and McPyV^- tumours seem to show relevant differences.

Role of carbonic anhydrases in ferroptosis-resistance

Iron is essential for all the lives on earth but may trigger a switch toward ferroptosis, a novel form of regulated necrosis. Carbonic anhydrases (CAs) are ubiquitous enzymes from microbes to humans. The primary function of CAs is to regulate cellular pH by hydrating carbon dioxide (CO₂) to protons (H⁺) and bicarbonate ions (HCO₃^-). Furthermore, CAs play roles in biosynthetic reactions, such as gluconeogenesis, lipogenesis, ureagenesis and are also associated with tumor metabolism, suggesting that CAs may be a potential target for the treatment of cancers. We have recently revealed a novel function of CA IX in ferroptosis-resistance by using human malignant mesothelioma cells. Herein, we aim to review the potential molecular association between ferroptosis and CAs, from the viewpoint of iron-metabolism, lipogenesis and signaling pathways both under physiological and pathological contexts.

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

Carbonic anhydrase IX (CA-IX) plays a pivotal role in regulation of pH in tumor milieu catalyzing carbonic acid formation by hydrating CO₂. An acidification of tumor microenvironment contributes to tumor progression via multiple processes, including reduced cell-cell adhesion, increased migration and matrix invasion. We aimed to assess whether the pharmacological inhibition of CA-IX could impair tumor cell proliferation and invasion. Tumor epithelial cells from breast (MDA-MB-231) and lung (A549) cancer were used to evaluate the cytotoxic effect of sulfonamide CA-IX inhibitors. Two CA-IX enzyme blockers were tested, SLC-0111 (at present in phase Ib clinical trial) and AA-06-05. In these cells, the drugs inhibited cell proliferation, migration and invasion through shifting of the mesenchymal phenotype toward an epithelial one and by impairing matrix metalloprotease-2 (MMP-2) activity. The antitumor activity was elicited via apoptosis pathway activation. An upregulation of p53 was observed, which in turn regulated the activation of caspase-3. Inhibition of proteolytic activity was accompanied by upregulation of the endogenous tissue inhibitor TIMP-2. Collectively, these data confirm the potential use of CA-IX inhibitors, and in particular SLC-0111 and AA-06-05, as agents to be further developed, alone or in combination with other conventional anticancer drugs.

The impact of tumour pH on cancer progression: strategies for clinical intervention

Dysregulation of cellular pH is frequent in solid tumours and provides potential opportunities for therapeutic intervention. The acidic microenvironment within a tumour can promote migration, invasion and metastasis of cancer cells through a variety of mechanisms. Pathways associated with the control of intracellular pH that are under consideration for intervention include carbonic anhydrase IX, the monocarboxylate transporters (MCT, MCT1 and MCT4), the vacuolar-type H⁺-ATPase proton pump, and the sodium-hydrogen exchanger 1. This review will describe progress in the development of inhibitors to these targets.

MicroRNA-mRNA Interactions at Low Levels of Compressive Solid Stress Implicate mir-548 in Increased Glioblastoma Cell Motility

Glioblastoma (GBM) is an astrocytic brain tumor with median survival times of <15 months, primarily as a result of high infiltrative potential and development of resistance to therapy (i.e., surgical resection, chemoradiotherapy). A prominent feature of the GBM microenvironment is compressive solid stress (CSS) caused by uninhibited tumor growth within the confined skull. Here, we utilized a mechanical compression model to apply CSS (<115 Pa) to well-characterized LN229 and U251 GBM cell lines and measured their motility, morphology, and transcriptomic response. Whereas both cell lines displayed a peak in migration at 23 Pa, cells displayed differential response to CSS with either minimal (i.e., U251) or large changes in motility (i.e., LN229). Increased migration of LN229 cells was also correlated to increased cell elongation. These changes were tied to epigenetic signaling associated with increased migration and decreases in proliferation predicted via Ingenuity® Pathway Analysis (IPA), characteristics associated with tumor aggressiveness. miRNA-mRNA interaction analysis revealed strong influence of the miR548 family (i.e., mir-548aj, mir-548az, mir-548t) on differential signaling induced by CSS, suggesting potential targets for pharmaceutical intervention that may improve patient outcomes.

Synthesis, biological evaluation and in silico modelling studies of 1,3,5-trisubstituted pyrazoles carrying benzenesulfonamide as potential anticancer agents and selective cancer-associated hCA IX isoenzyme inhibitors

Inhibition of carbonic anhydrases (CAs, EC 4.2.1.1) has clinical importance for the treatment of several diseases. They participate in crucial regulatory mechanisms for balancing intracellular and extracellular pH of the cells. Among CA isoforms, selective inhibition of hCA IX has been linked to decreasing of cell growth for both primary tumors and metastases. The discovery of novel CA inhibitors as anticancer drug candidates is a current topic in medicinal chemistry. 1,3,5-Trisubstituted pyrazoles carrying benzenesulfonamide were evaluated against physiologically abundant cytosolic hCA I and hCA II and trans-membrane, tumor-associated hCA IX isoforms by a stopped-flow CO2 hydrase method. Their in vitro cytotoxicities were screened against human oral squamous cell carcinoma (OSCC) cell lines (HSC-2) and human mesenchymal normal oral cells (HGF) via 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) test. Compounds 6, 8, 9, 11, and 12 showed low nanomolar hCA II inhibitory potency with Ki < 10 nM, whereas compounds 9 and 12 displayed Ki < 10 nM against hCA IX isoenzyme when compared with reference Acetazolamide (AZA). Compound 9, 4-(3-(hydrazinecarbonyl)-5-(4-nitrophenyl)-1H-pyrazol-1-yl)benzenesulfonamide, can be considered as the most selective hCA IX inhibitor over off-target cytosolic isoenzymes hCA I and hCA II with the lowest Ki value of 2.3 nM and selectivity ratios of 3217 (hCA I/hCA IX) and 3.9 (hCA II/hCA IX). Isoform selectivity profiles were also discussed using in silico modelling. Cytotoxicity results pointed out that compounds 5 (CC50 = 37.7 μM) and 11 (CC50 = 58.1 μM) can be considered as lead cytotoxic compounds since they were more cytotoxic than 5-Fluorouracil (5-FU) and Methotrexate (MTX).

Carbonic anhydrase 9 confers resistance to ferroptosis/apoptosis in malignant mesothelioma under hypoxia

Hypoxia and acidity provide microenvironment for selection under evolutionary pressure and proliferation in cancer cells. Carbonic anhydrases (CAs) are a superfamily of metalloenzymes present in all life kingdoms, equilibrating the reactions among CO₂, bicarbonate and H⁺. CA9, a membrane-associated α-CA, has been a drug target for various cancers. Whereas iron is essential not only for cancer cells but also for all the lives on earth, little is known on the association among hypoxia, iron metabolism, extracellular acidity and redox regulation. Malignant mesothelioma (MM), an aggressive tumor with poor prognosis, is an intriguing model in that asbestos-associated pathogenesis includes excess iron environment during carcinogenesis. Re-analysis of rat asbestos-induced MM model revealed an inverse association between high CA9 expression and survival. Here we used human MMs to identify the molecular events surrounding CA9 from the viewpoint of iron metabolism. CA9 expression was significantly higher in MM cells than in MeT-5A mesothelial cells, which was further amplified under hypoxia (1%O₂) with increased catalytic Fe(II). CA9 suppression by inhibitors (S4 and U104) decreased viability and migration of MM cells, accompanied by overexpression of TFRC, IREB1/2 and FPN1(SLC40A1) and by downregulation of FTH/FTL. This expressional pattern was similar to that of erastin-induced ferroptosis in the same cells. Furthermore, we observed mitochondrial fission and enhanced autophagy with increased catalytic Fe(II) in both mitochondria and lysosomes after CA9 inhibition, accompanied by increased peroxides, mitochondrial O₂⁻ and lipid peroxidation. The eventual cell death was significantly inhibited by deferoxamine, ferrostatin-1 and Z-VAD-FMK, suggesting a mixed cell death of ferroptosis and apoptosis. Therefore, CA9 plays a role in equilibrating among hypoxia, iron metabolism and redox regulation in MM cells.

New Monoclonal Antibodies for a Selective Detection of Membrane-Associated and Soluble Forms of Carbonic Anhydrase IX in Human Cell Lines and Biological Samples

Monoclonal antibodies (MAbs) selectively targeting tumor-associated antigens such as carbonic anhydrase IX (CA IX) can significantly contribute to research, diagnostics, and treatment of CA IX-related cancers. CA IX is overexpressed in numerous hypoxic cancers where it promotes tumor progression. Therefore, it is considered as a promising tumor biomarker. A novel collection of MAbs against recombinant CA IX was developed and evaluated in different immunoassays for studying CA IX expression. The reactivity of MAbs with native cell surface protein was confirmed by flow cytometry and the presence of hypoxia-inducible CA IX was investigated in several human cancer cell lines. In addition, the applicability of MAbs for visualization of CA IX-positive tumor cells by immunofluorescence microscopy was demonstrated. MAb H7 was identified as the most promising MAb for different immunoassays. It recognized a linear epitope covering CA IX sequence of 12 amino acid residues 55-GEDDPLGEEDLP-66 within the proteoglycan domain. The MAb H7 was the only one of the collection to immunoprecipitate CA IX protein from cell lysates and detect the denatured CA IX with near-infrared fluorescence Western blot. It was also employed in sandwich enzyme-linked immunosorbent assay to detect a soluble form of CA IX in growth medium of tumor cells and blood plasma samples. The diagnostic potential of the MAb H7 was confirmed on formalin-fixed and paraffin-embedded tissue specimen of cervical carcinoma in situ by immunohistochemistry. The generated MAbs, in particularly clone H7, have great potential in diagnostics and research of CA IX-related cancers.

Computational modeling of novel inhibitory peptides targeting proteoglycan like region of carbonic anhydrase IX and in vitro validation in HeLa cells

Carbonic anhydrase IX (CAIX) is a tumour-associated, hypoxia-induced, membrane-bound metallo-enzyme which catalyzes the reversible hydration of carbon dioxide (CO₂) to bicarbonate (HCO₃^-) and proton (H⁺) ions. Over expression of CAIX is observed in cancers of colon, lung, kidney, breast, etc. CAIX plays a vital role in maintaining favourable intracellular pH for tumour cell growth and extracellular acidification which in-turn leads to drug resistance and spread of factors influencing tumour invasion. The N-terminal proteoglycan (PG) - like fragment of CAIX is unique to this isoform and is considered as potential druggable hotspot. Recently, M75 monoclonal antibody targeting the LPGEEDLPG epitope of PG like region has been proposed to reduce cellular adhesion in cancer cells. LPGEEDLPG fragment in complex with M75 has been crystallized and it serves as a strong base for development of peptide inhibitors based on interacting interfaces. Thus, in this study, an in-depth analysis of intermolecular interactions in LPGEEDLPG-M75 complex was carried out by implementing extensive molecular dynamics simulations, binding free energy calculations so as to infer the major determinant fragments of M75 that can be used as peptide inhibitors targeting PG region. Based on these analyses, 3 peptides (Pep1, Pep2 and Pep3) were synthesized and validated by in vitro assays involving cytotoxicity assessment, CAIX inhibition analysis through Direct and Indirect functional assays, and inhibition of Cell adhesion in HeLa cells. The results reveal Pep1 to be a promising inhibitor as it could efficiently modulate CAIX mediated pH homeostasis and cell adhesion in cancer cells.Communicated by Ramaswamy H. Sarma.

Distinct Immune Cell Populations Define Response to Anti-PD-1 Monotherapy and Anti-PD-1/Anti-CTLA-4 Combined Therapy

Cancer immunotherapies provide survival benefits in responding patients, but many patients fail to respond. Identifying the biology of treatment response and resistance are a priority to optimize drug selection and improve patient outcomes. We performed transcriptomic and immune profiling on 158 tumor biopsies from melanoma patients treated with anti-PD-1 monotherapy (n = 63) or combined anti-PD-1 and anti-CTLA-4 (n = 57). These data identified activated T cell signatures and T cell populations in responders to both treatments. Further mass cytometry analysis identified an EOMES⁺CD69⁺CD45RO⁺ effector memory T cell phenotype that was significantly more abundant in responders to combined immunotherapy compared with non-responders (n = 18). The gene expression profile of this population was associated with longer progression-free survival in patients treated with single agent and greater tumor shrinkage in both treatments.

The Warburg Effect Is Associated With Tumor Aggressiveness in Testicular Germ Cell Tumors

Testicular Germ Cell Tumors (TGCTs) are a rare group of neoplasms and the most common solid malignancy arising in young male adults. Despite the good response of these tumors to platinum-based chemotherapy, some patients are refractory to treatment and present poor clinical outcomes. During carcinogenesis and tumor development, cancer cells reprogram energy metabolism toward a hyper-glycolytic phenotype, an emerging hallmark of cancer. This phenomenon, known as the Warburg effect or aerobic glycolysis, involves overexpression of metabolism-related proteins, like glucose and monocarboxylate transporters, pH regulators and intracellular glycolytic enzymes. The metabolic profile of TGCTs is very little explored and, recently, this metabolic rewiring of cancer cells has been associated with aggressive clinicopathological characteristics of these tumors. The overexpression of monocarboxylate transporter 4 (MCT4) in TGCTs has been pointed out as a poor prognostic factor, as well as a promising therapeutic target. As a result, the main aim of the present study was to evaluate the prognostic value of key metabolism-related proteins in TGCTs. The immunohistochemical expressions of CD44 (as a monocarboxylate transporter chaperone), glucose transporter 1 (GLUT1), carbonic anhydrase IX (CAIX), hexokinase II (HKII) and lactate dehydrogenase V (LDHV) were evaluated in a series of 148 adult male patients with TGCTs and associated with clinicopathological parameters. In addition, paired normal tissues were also evaluated. The sample included 75 seminoma and 73 non-seminoma tumors. GLUT1 and CD44 expression was significantly increased in malignant samples when compared to paired normal samples. Conversely, HKII and LDHV expressions were significantly decreased in malignant samples. Concerning the clinicopathological values, CAIX expression was significantly associated with disease recurrence, while HKII expression was significantly associated with aggressive characteristics of TGCTs, including higher staging and non-seminoma histology. In conclusion, this study brings new insights on the metabolic characteristics of TGCTs, showing alterations in the expression of proteins related with the Warburg effect, as well as associations of the hyper-glycolytic and acid-resistant phenotype with aggressive clinicopathological parameters.

Warburg effect, lactate dehydrogenase, and radio/chemo-therapy efficacy

The anaerobic metabolism of glucose by cancer cells, even under well-oxygenated conditions, has been documented by Otto Warburg as early as 1927. Micro-environmental hypoxia and intracellular pathways activating the hypoxia-related gene response, shift cancer cell metabolism to anaerobic pathways. In the current review, we focus on a major enzyme involved in anaerobic transformation of pyruvate to lactate, namely lactate dehydrogenase 5 (LDH5). The value of LDH5 as a marker of prognosis of cancer patients, as a predictor of response to radiotherapy (RT) and chemotherapy and, finally, as a major target for cancer treatment and radio-sensitization is reported and discussed. Clinical, translational and experimental data supporting the uniqueness of the LDHA gene and its product LDH5 isoenzyme are summarized and future directions for a metabolic treatment of cancer are highlighted.

Carbonic anhydrase IX enhances tumor cell proliferation and tumor progression in osteosarcoma

Purpose

We investigated the effect of carbonic anhydrase IX (CA IX) inhibitor under hypoxia and normoxia in SaOS2 human osteosarcoma cell line. We also evaluated the expression of CA IX in 27 patients diagnosed with osteosarcoma.

Materials and methods

CA IX expression in SaOS2 cells cultured under different oxygen tensions was analyzed by Western blotting. To evaluate the effect of CA IX inhibitor, MTS cell viability assay was performed after cells were treated with various concentrations of doxorubicin with or without a CA IX inhibitor. Finally, CA IX expression in patient-derived osteosarcoma samples was evaluated by immunohistochemistry.

Results

Treatment with CA IX inhibitor significantly suppressed cell proliferation and migration under hypoxic conditions. CA IX expression was observed in 81% of 27 patients. The 5-year survival rates in patients with high and low stain scores were 43.8% and 81.8%, respectively.

Conclusion

CA IX inhibitors have the potential to suppress cell proliferation, migration, and chemoresistance.

Overexpression of FZD1 and CAIX are Associated with Invasion, Metastasis, and Poor-Prognosis of the Pancreatic Ductal Adenocarcinoma

Approximately 80% of patients with pancreatic ductal adenocarcinoma (PDAC) have metastatic disease with poor prognosis, but clinically available biomarkers have not yet been identified. This study was to investigate the clinical significance of FZD1 and CAIX in PDACs. FZD1 and CAIX protein expression was measured using EnVision immunohistochemistry. Positive FZD1 or CAIX expression was significantly higher in PDAC than that in precursor lesions (p < 0.01). Positive FZD1 or CAIX expression was significantly lower in cases with well-differentiated adenocarcinoma, no-metastasis of the lymph node, no-invasion of regional tissues, and TNM I/II stage disease than in cases with poorly-differentiated adenocarcinoma, metastasis and invasion, and TNM stage III+ IV stage disease (p < 0.05 or p < 0.01). The expression of FZD1 positively correlated with CAIX in PDAC (P = 0.000). Univariate Kaplan-Meier analysis showed that FZD1 and/or CAIX expression (p < 0.001) was significantly associated with shorter overall survival (p < 0.05). Cox multivariate analysis showed that differentiation, tumor mass, lymph node metastasis, invasion, TNM stage, FZD1 and CAIX levels negatively correlated with overall survival. Positive FZD1 and CAIX expressions are poor prognostic factors in PDAC patients. FZD1 and CAIX might be important biological markers for the carcinogenesis, metastasis, invasion, and prognosis of PDAC.

Biochemical, biophysical and molecular dynamics studies on the proteoglycan-like domain of carbonic anhydrase IX

Human carbonic anhydrase IX (hCA IX) is a tumour-associated enzyme present in a limited number of normal tissues, but overexpressed in several malignant human tumours. It is a transmembrane protein, where the extracellular region consists of a greatly investigated catalytic CA domain and a much less investigated proteoglycan-like (PG) domain. Considering its important role in tumour biology, here, we report for the first time the full characterization of the PG domain, providing insights into its structural and functional features. In particular, this domain has been produced at high yields in bacterial cells and characterized by means of biochemical, biophysical and molecular dynamics studies. Results show that it belongs to the family of intrinsically disordered proteins, being globally unfolded with only some local residual polyproline II secondary structure. The observed conformational flexibility may have several important roles in tumour progression, facilitating interactions of hCA IX with partner proteins assisting tumour spreading and progression.

Frequent CLDN18-ARHGAP fusion in highly metastatic diffuse-type gastric cancer with relatively early onset

CLDN18-ARHGAP26/6 fusions have been identified in gastric cancers, with a predominance in diffuse-type gastric cancers (DGCs). Although in vitro experiments have suggested an oncogenic role for CLDN18-ARHGAP26/6 fusions, the exact frequencies and clinicopathological characteristics of the fusion-positive cases are poorly understood. We analyzed 254 cases of gastric cancer (172 diffuse-type and 82 intestinal-type) using RT-PCR and FISH, and also analyzed TCGA transcriptome datasets to identify genes that are related to the aggressive behaviors of fusion-positive cancers. Our assays identified 26 fusion-positive cases, 22 of which were DGCs (22/172, 12.8%). Unlike fusion-negative DGCs, almost all fusion-positive DGCs retained E-cadherin expression (P = 0.036). Fusion-positive DGCs also showed a higher prevalence of lymphatic and distant organ metastases, and these trends were only significant in the younger age group (< 60 years). In this group, the majority of cases with distant organ metastases (4 of 6 cases) were fusion-positive, and the multivariate regression analysis revealed that fusion status was an independent predictive marker for distant organ metastases (P = 0.002). In the TCGA dataset analysis, carbonic anhydrase 9 was postulated to be a potential modulator of the age-specific effects of the fusion protein, compatible with the immunohistochemical analysis of our cohort. Therefore, CLDN18-ARHGAP26/6 fusion-positive DGCs are considered biologically distinct entities that will require more advanced therapeutic options.

Carbonic anhydrase 9 expression in well-differentiated pancreatic neuroendocrine neoplasms might be associated with aggressive behavior and poor survival

Well-differentiated pancreatic neuroendocrine neoplasms/tumors (PanNETs) are rare neoplasms with diverse clinical behavior. Biomarker discovery is important for predicting clinical course and prognosis of PanNET patients. Carbonic anhydrase 9 (CA9) and vimentin are hypoxia and epithelial-mesenchymal transition-related proteins of which expression in many carcinomas has been associated with poor prognosis, but their significance in PanNET has yet to be determined. We assessed CA9 and vimentin expression in 164 PanNETs and compared this with clinicopathologic characteristics. CA9 expression was observed in normal islets, while neuroendocrine microadenomas and small (< 1 cm) PanNETs showed loss of CA9 expression. CA9 and vimentin expression was observed in 38 (23%) and 36 (22%) of PanNETs, respectively. CA9 expression was associated with larger size (p = 0.001), higher grade (p < 0.001), higher pT category (p < 0.001), lymph node (p = 0.003) and distant (p = 0.047) metastases, higher AJCC stage (p < 0.001), and lymphovascular (p < 0.001) and perineural (p = 0.002) invasion. PanNET patients with CA9 expression had a shorter recurrence-free survival (5-year survival rate 47%) than those without CA9 expression (76%) by univariate (p = 0.001) but not multivariate analysis. Vimentin expression correlated with CA9 expression (p < 0.001) but not with other clinicopathologic factors. In conclusion, CA9 expression was observed in normal islets, while neuroendocrine microadenomas and small (< 1 cm) PanNETs showed CA9 expression loss. CA9 expression gradually reappeared in larger PanNETs, and this was associated with clinical progression and decreased patient survival by univariate but not multivariate analysis.

Inhibition of carbonic anhydrase IX targets primary tumors, metastases, and cancer stem cells: Three for the price of one

Human carbonic anhydrase (CA) IX is a tumor-associated protein, since it is scarcely present in normal tissues, but highly overexpressed in a large number of solid tumors, where it actively contributes to survival and metastatic spread of tumor cells. Due to these features, the characterization of its biochemical, structural, and functional features for drug design purposes has been extensively carried out, with consequent development of several highly selective small molecule inhibitors and monoclonal antibodies to be used for different purposes. Aim of this review is to provide a comprehensive state-of-the-art of studies performed on this enzyme, regarding structural, functional, and biomedical aspects, as well as the development of molecules with diagnostic and therapeutic applications for cancer treatment. A brief description of additional pharmacologic applications for CA IX inhibition in other diseases, such as arthritis and ischemia, is also provided.

Hypoxia-regulated gene expression explains differences between melanoma cell line-derived xenografts and patient-derived xenografts

Cell line-derived xenografts (CDXs) are an integral part of drug efficacy testing during development of new pharmaceuticals against cancer but their accuracy in predicting clinical responses in patients have been debated. Patient-derived xenografts (PDXs) are thought to be more useful for predictive biomarker identification for targeted therapies, including in metastatic melanoma, due to their similarities to human disease. Here, tumor biopsies from fifteen patients and ten widely-used melanoma cell lines were transplanted into immunocompromised mice to generate PDXs and CDXs, respectively. Gene expression profiles generated from the tumors of these PDXs and CDXs clustered into distinct groups, despite similar mutational signatures. Hypoxia-induced gene signatures and overexpression of the hypoxia-regulated miRNA hsa-miR-210 characterized CDXs. Inhibition of hsa-miR-210 with decoys had little phenotypic effect in vitro but reduced sensitivity to MEK1/2 inhibition in vivo, suggesting down-regulation of this miRNA could result in development of resistance to MEK inhibitors.

Carbonic Anhydrase IX (CAIX), Cancer, and Radiation Responsiveness

Carbonic anhydrase IX has been under intensive investigation as a therapeutic target in cancer. Studies demonstrate that this enzyme has a key role in pH regulation in cancer cells, allowing these cells to adapt to the adverse conditions of the tumour microenviroment. Novel CAIX inhibitors have shown efficacy in both in vitro and in vivo pre-clinical cancer models, adversely affecting cell viability, tumour formation, migration, invasion, and metastatic growth when used alone. In co-treatments, CAIX inhibitors may enhance the effects of anti-angiogenic drugs or chemotherapy agents. Research suggests that these inhibitors may also increase the response of tumours to radiotherapy. Although many of the anti-tumour effects of CAIX inhibition may be dependent on its role in pH regulation, recent work has shown that CAIX interacts with several of the signalling pathways involved in the cellular response to radiation, suggesting that pH-independent mechanisms may also be an important basis of its role in tumour progression. Here, we discuss these pH-independent interactions in the context of the ability of CAIX to modulate the responsiveness of cancer to radiation.

"Seriously Sweet": Acesulfame K Exhibits Selective Inhibition Using Alternative Binding Modes in Carbonic Anhydrase Isoforms

Human carbonic anhydrase IX (CA IX) is upregulated in neoplastic tissues; as such, it is studied as a drug target for anticancer chemotherapy. Inhibition of CA IX has been shown to be therapeutically favorable in terms of reducing tumor growth. Previously, saccharin, a commonly used artificial sweetener, has been observed to selectively inhibit CA IX over other CA isoforms. In this study, X-ray crystallography showed acesulfame potassium (Ace K) binding directly to the catalytic zinc in CA IX (mimic) and through a bridging water in CA II. This modulation in binding is reflected in the binding constants, with Ace K inhibiting CA IX but not other CA isoforms. Hence, this study establishes the potential of Ace K (an FDA approved food additive) as a lead compound in the design and development of CA IX specific inhibitors.

Proteus mirabilis inhibits cancer growth and pulmonary metastasis in a mouse breast cancer model

A variety of bacteria have been used as agents and vectors for antineoplastic therapy. A series of mechanisms, including native bacterial toxicity, sensitization of the immune system and competition for nutrients, may contribute to antitumor effects. However, the antitumor effects of Proteus species have been minimally studied, and it is not clear if bacteria can alter tumor hypoxia as a component of their antineoplastic effect. In the present study, Proteus mirabilis bacteria were evaluated for the ability to proliferate and accumulate in murine tumors after intravenous injection. To further investigate the efficacy and safety of bacterial injection, mice bearing 4T1 tumors were treated with an intravenous dose of 5×107 CFU Proteus mirabilis bacteria via the tail vein weekly for three treatments. Histopathology, immunohistochemistry (IHC) and western analysis were then performed on excised tumors. The results suggested Proteus mirabilis localized preferentially to tumor tissues and remarkably suppressed the growth of primary breast cancer and pulmonary metastasis in murine 4T1 models. Results showed that the expression of NKp46 and CD11c was significantly increased after bacteria treatment. Furthermore, tumor expression of carbonic anhydrase IX (CA IX) and hypoxia inducible factor-1a (HIF-1a), surrogates for hypoxia, was significantly lower in the treated group than the control group mice as assessed by IHC and western analysis. These findings demonstrated that Proteus mirabilis may a promising bacterial strain for used against primary tumor growth and pulmonary metastasis, and the immune system and reduction of tumor hypoxia may contribute to the antineoplastic and antimetastatic effects observed.

Carbonic anhydrase IX inhibition affects viability of cancer cells adapted to extracellular acidosis

Among the players of the adaptive response of cancer cells able to promote a resistant and aggressive phenotype, carbonic anhydrase IX (CAIX) recently has emerged as one of the most relevant drug targets. Indeed, CAIX targeting has received a lot of interest, and selective inhibitors are currently under clinical trials. Hypoxia has been identified as the master inductor of CAIX, but, to date, very few is known about the influence that another important characteristic of tumor microenvironment, i.e., extracellular acidosis, exerts on CAIX expression and activity. In the last decades, acidic microenvironment has been associated with aggressive tumor phenotype endowed with epithelial-to-mesenchymal transition (EMT) profile, high invasive and migratory ability, apoptosis, and drug resistance. We demonstrated that melanoma, breast, and colorectal cancer cells transiently and chronically exposed to acidified medium (pH 6.7 ± 0.1) showed a significantly increased CAIX expression compared to those grown in standard conditions (pH 7.4 ± 0.1). Moreover, we observed that the CAIX inhibitor FC16-670A (also named SLC-0111, which just successfully ended phase I clinical trials) not only prevents such increased expression under acidosis but also promotes apoptotic and necrotic programs only in acidified cancer cells. Thus, CAIX could represent a selective target of acidic cancer cells and FC16-670A inhibitor as a useful tool to affect this aggressive subpopulation characterized by conventional therapy escape.

KEY MESSAGES

Cancer cells overexpress CAIX under transient and chronic extracellular acidosis. Acidosis-induced CAIX overexpression is NF-κB mediated and HIF-1α independent. FC16-670A prevents CAIX overexpression and induces acidified cancer cell death.