Targeting Hypoxia-Induced Carbonic Anhydrase IX Enhances Immune-Checkpoint Blockade Locally and Systemically

The Diagnostic Value of Plasma Small Extracellular Vesicle-Derived CAIX Protein in Prostate Cancer and Clinically Significant Prostate Cancer: A Study on Predictive Models

BACKGROUND

Current diagnostic tools are inaccurate and not specific to prostate cancer (PCa) diagnosis. Cancer-derived small extracellular vehicles (sEVs) play a key role in intercellular communication. In this study, we examined the diagnostic value of plasma sEV-derived carbonic anhydrase IX (CAIX) protein for PCa and clinically significant prostate cancer (csPCa) diagnosis and avoiding unnecessary biopsies.

METHODS

Plasma samples (n = 230) were collected from the patients who underwent prostate biopsy with elevated prostate-specific antigen (PSA) levels. sEVs were isolated and characterized, and sEV protein CAIX was measured using an enzyme-linked immunosorbent assay. Independent predictors of csPCa (Gleason score ≥ 7) were identified, and a predictive model was established. A Nomogram for predicting csPCa was developed using data from the training cohort.

RESULTS

The expression of sEV protein CAIX was significantly higher in both PCa and csPCa compared to benign patients and nonsignificant PCa (nsPCa) (Gleason score < 7, p < 0.001). sEV protein CAIX performed well in distinguishing PCa from benign patients. The predictive model defined by sEV protein CAIX and PSA density (PSAD) demonstrated the highest discriminative ability for csPCa (AUC = 0.895), with diagnostic sensitivity and specificity of 82.5% and 85.8%, respectively. Furthermore, sEV protein CAIX is an effective predictor of 2-year biochemical recurrence (BCR) in PCa patients (p = 0.013), and its high expression is significantly associated with poorer BCR-free survival (p < 0.05).

CONCLUSIONS

Our findings demonstrate the excellent performance of sEV protein CAIX in PCa and csPCa diagnosis. The Nomogram-based csPCa predictive model incorporating sEV protein CAIX and PSAD exhibits strong predictive value. Additionally, assessing plasma sEV protein CAIX expression levels can further aid in evaluating patient prognosis and provide a basis for making effective treatment decisions.

Development of 4T1 breast cancer mouse model system for preclinical carbonic anhydrase IX studies

Triple-negative breast cancer (TNBC) is the most aggressive type of breast cancer, for which targeted treatment is currently lacking. Carbonic anhydrase IX (CAIX) is a known cancer target due to its selective overexpression in hypoxia, a hallmark of many solid cancers including TNBC. This study aimed to develop a robust murine TNBC cell line 4T1-based model system that could be used in the comprehensive preclinical evaluation of targeting CAIX. The model is based on the original 4T1 breast cancer cell line and two genetically edited versions of it-one with biallelic CRISPR/Cas9-mediated Car9 inactivation and another with constitutively expressed Car9, thus ensuring negative and positive controls for CAIX production in the model system, respectively. The generated cell lines were validated for CAIX production and characterised functionally in vitro and in vivo after orthotopic implantation in syngeneic BALB/c mice. Results demonstrated significantly reduced primary tumour growth and metastatic progression rates in animals with CAIX-deficient tumours, while the CAIX-expressing tumours had vascularised phenotypes with prominent central areas of coagulative necrosis. The differential CAIX expression levels in the model were preserved during tumour growth in syngeneic mice, as verified by in vivo imaging using a novel high-affinity CAIX-specific near-infrared (NIR) fluorescent imaging probe, GZ22-4. Constitutive overexpression of autologous CAIX did not elicit specific autoantibody responses in vivo, demonstrating the suitability of this model for evaluating the efficacy of anti-CAIX vaccination as a therapeutic strategy. The in vivo study was repeated as an independent experiment and demonstrated good robustness of the developed model.

Cooperative Role of Carbonic Anhydrase IX/XII in Driving Tumor Invasion and Metastasis: A Novel Targeted Therapeutic Strategy

Cancer invasion and metastasis are critical factors that influence patient prognosis. Carbonic anhydrase IX (CA IX) and carbonic anhydrase XII (CA XII) are key regulators of hypoxia and pH homeostasis in the tumor microenvironment (TME). It has been verified that both CA IX and CA XII play significant roles in promoting tumor metastasis in recent years, but most of the literature tends to treat them as separate entities rather than exploring their synergistic effects. This review provides a comprehensive overview of the roles of CA IX and CA XII in tumor invasion and metastasis, along with their clinical applications, including their spatial distribution characteristics, molecular mechanisms that facilitate tumor metastasis, and their potential for clinical translation. Moreover, this review incorporates the classical tumor core-invasive front model to propose a metabolic coupling model of CA IX and CA XII, offering a fresh perspective on precision therapies that target tumor metabolism. By emphasizing the metabolic coupling between these two molecules, this review offers new insights distinct from previous studies and highlights the clinical therapeutic potential of simultaneously targeting both during treatment. It sheds new light on future research and clinical applications, aiming to enhance the prognosis of cancer patients through innovative therapeutic strategies.

Role of the tumor microenvironment in cancer therapy: unveiling new targets to overcome drug resistance

Cancer is a leading cause of death globally, with resistance to therapy representing a major obstacle to effective treatment. The tumor microenvironment (TME), comprising a complex network to cellular and non-cellular components including cancer-associated fibroblasts, immune cells, the extracellular matrix and region of hypoxia, is integral to cancer progression and therapeutic resistance. This review delves into the multifaceted interactions within the TME that contribute to tumor growth, survival and immune evasion. Key elements such as the role of cancer- associated fibroblasts in remodeling the extracellular matrix and promoting angiogenesis, the influence of immune cells such as tumor-associated macrophages in creating an immunosuppressive milieu and the impact of hypoxia conditions on metabolic adaptation and therapy resistance are thoroughly examined. This review evaluates current and emerging TME-targeted therapeutic strategies, including inhibitors of extracellular matrix components, modulators of immune cell activity and approached to alleviate hypoxia. Combination therapies that integrate TME-targeted agents with conventional treatments such as chemotherapy and immunotherapy are also discussed for their potential to enhance treatment efficacy and circumvent resistance mechanisms. By synthesising recent advances in TME research and therapeutic innovation, this paper aims to underscore the importance of TME in cancer therapy and highlight promising avenues for improving patient outcomes through targeted intervention.

Carbonic anhydrase IX inhibition as a path to treat neuroblastoma

BACKGROUND AND PURPOSE

Tumour hypoxia frequently presents a major challenge in the treatment of neuroblastoma (NBL). The neuroblastoma cells produce carbonic anhydrase IX (CA IX), an enzyme crucial for the survival of cancer cells in low-oxygen environments.

EXPERIMENTAL APPROACH

We designed and synthesised a novel high-affinity inhibitor of CA IX. The highest to-date. The affinities were determined for all human catalytically active CA isozymes showing significant selectivity for CA IX over other isozymes. The inhibitor effect on neuroblastoma cancer cell growth was determined in vitro and in vivo via a mice xenograft model.

KEY RESULTS

The novel designed inhibitor effectively mitigated the acidification induced by CA IX and reduced spheroid growth under hypoxic conditions in the SK-N-AS cell line. It also diminished the secretion of pro-tumour chemokines IL-8 (CXCL2) and CCL2. When we combined this novel CA IX inhibitor with a compound that inhibits the chemokine receptor CCR2 protein activity, we observed a reduction in mouse tumour growth. The combined treatment also prompted tumours to exhibit adaptive resistance by producing higher levels of vascular endothelial growth factor receptors (VEGFR) and other compensatory signals.

CONCLUSIONS AND IMPLICATIONS

This research underscores the pivotal role of CA IX in cancer and the potential of a novel CA IX inhibitor-based combination intervention therapy for neuroblastoma treatment.

Investigating the Anti-Inflammatory Potential of SLC-0111: A Carbonic Anhydrase Inhibitor Targeting Cyclooxygenase-Mediated Inflammatory Pathways in a Carrageenan-Induced Rat Model

Inflammation is a fundamental physiological reaction that leads to the development of many diseases, including tissue damage, asthma, diabetes, atherosclerosis, inflammatory bowel disease, and cancer. The enzyme COX is a vital mediator in inflammatory processes. Interestingly, the COX enzyme possesses multiple structural similarities to the carbonic anhydrase enzyme. SLC-0111, a molecule known for its potent and selective inhibition of carbonic anhydrase, has not yet been studied for its potential effects on acute inflammation, proinflammatory cytokine levels, or oxidative stress parameters. Our study seeks to assess the binding affinity of SLC-0111 to the COX enzyme, as well as its possible anti-inflammatory properties. We treated rats SLC-0111 at dosages of 50, 100, and 200 mg/kg for 3 days before generating inflammation with carrageenan (CAR). Following CAR delivery, paw thickness was evaluated at 4-h intervals to assess inflammatory levels. Additionally, protein extravasation in paw tissue has been examined using Evans Blue (EB) dye. MDA and glutathione (GSH) levels in paw tissue were measured to assess oxidative stress. Carrageenan enhanced edema, protein extravasation, and proinflammatory cytokines TNF-α, IL-1β, IL-6, IL-4, and IL-13. SLC-0111 decreased all of these, except for IL-4. Similarly, the histological findings of our research indicated that SLC-0111 had an anti-inflammatory effect at a dose of 200 mg/kg. However, SLC-0111 had no significant effect on MDA or GSH levels. These data represent that SLC-0111 may have anti-inflammatory properties and could be used as a treatment for inflammation-related disorders.

Effects of metabolism upon immunity: Targeting myeloid-derived suppressor cells for the treatment of breast cancer is a promising area of study

Breast cancer (BC) ranks among the most prevalent malignancies affecting women, with advanced-stage patients facing an increased mortality risk. Myeloid-derived suppressor cells (MDSCs) contribute significantly to poor prognostic outcomes. Research has concentrated predominantly on the immunological mechanisms underlying MDSC functions, but a comprehensive investigation into the metabolic interactions between BC cells and MDSCs is lacking. In a hypoxic tumor microenvironment (TME), BC cells can enhance aerobic-glycolysis rates, upregulate expression of key lipid metabolism enzymes such as cluster of differentiation (CD) 36 and 5-lipoxygenase (5-LOX), accelerate glutamine (Gln) uptake, and elevate extracellular adenosine (eADO) levels, thereby fostering MDSC proliferation and amplifying immune suppression. Concurrently, alterations in the metabolic state of MDSCs also influence BC progression. To ensure adequate proliferative resources, MDSCs upregulate the pentose phosphate pathway and expedite glycolysis for energy supply while increasing the expression of fatty acid transport proteins (FATPs) such as CD36 and fatty acid transporter 2 (FATP2) to maintain intracellular lipid availability, thereby enhancing their adaptability within the TME. Furthermore, MDSCs undermine T-cell anti-tumor efficacy by depleting essential amino acids (AAs), such as arginine (Arg), tryptophan (Trp), and cysteine (Cys), required for T-cell function. This review elucidates how pharmacological agents such as metformin, liver X receptor (LXR) agonists, and 6-diazo-5-oxo-L-norleucine (DON) can augment anti-cancer treatment efficacy by targeting metabolic pathways in MDSCs. We systematically delineate the mechanisms governing interactions between BC cells and MDSCs from a metabolic standpoint while summarizing therapeutic strategies to modulate metabolism within MDSCs. Our review provides a framework for optimizing MDSC applications in BC immunotherapy.

[A commentary: New carbonic anhydrase IX-targeted probes for imaging hypoxic tumors]

In 2023, the journals "Bioconjugate Chemistry" and "Sensors and Actuators B: Chemical" published two papers describing new biosensors for imaging hypoxic regions in tumors. Cao et al. combined acetazolamide (AZA) to target carbonic anhydrase IX (CA IX) with two tyrosine-derived Mn(II)-ethylenediaminetetraacetic acid chelates (TyEDTA) on a rigid triazine (TA) scaffold. The aim of this synthesis was to create a Mn(II)-based magnetic resonance imaging probe named AZA-TA-Mn. In a murine hypoxia model of esophageal squamous cell carcinoma, AZA-TA-Mn, at a low dose of 0.05mmol/kg, produced selective contrast enhancement over non-specific Gd-diethylenetriaminepentaacetic acid (0.1mmol/kg). A competition study involving the co-injection of free AZA and a Mn(II)-based magnetic resonance imaging probe confirmed the in vivo tumor selectivity of AZA-TA-Mn. Immunofluorescence staining of tissue sections confirmed the positive correlation between tumor accumulation of AZA-TA-Mn and overexpression of AC IX. Using CA IX as a biomarker of hypoxia, Cao et al. have thus illustrated a practical strategy for the development of novel imaging probes for specific regions of hypoxia in a tumor of interest.

Recent advances of anti-tumor nano-strategies via overturning pH gradient: alkalization and acidification

The acidic tumor microenvironment, a hallmark of many solid tumors, is primarily induced by the high glycolytic rate of tumor cells. To avoid acidosis, tumor cells ingeniously maintain an acidic extracellular pH while keeping a relatively alkaline intracellular pH. Overturning the unique pH gradient of tumor cells has exhibited to be a viable approach for cancer therapy. In this review, the formation and regulatory mechanisms of the acidic microenvironment in solid tumors will be firstly outlined. Subsequently, we will comprehensively summarize the latest advancements in anti-tumor therapy via using nanomedicines to manipulate the tumor pH gradient, including acidifying intracellular environment and alkalizing extracellular environment. Following this, we will discuss the future potential of strategies employing nanomedicines to reverse tumor pH gradient. This review aims to foster research on therapeutic approaches targeting the pH regulation of solid tumors and holds an optimistic outlook for the future development of this field.

Design, Synthesis, Anticancer Screening, and Mechanistic Study of Spiro-N-(4-sulfamoyl-phenyl)-1,3,4-thiadiazole-2-carboxamide Derivatives

The present study aims to create spiro-N-(4-sulfamoyl-phenyl)-1,3,4-thiadiazole-2-carboxamide derivatives with anticancer activities. The in vitro anticancer evaluation showed that only the novel spiro-acenaphthylene tethered-[1,3,4]-thiadiazole (compound 1) exhibited significant anticancer efficacy as a selective inhibitor of tumor-associated isoforms of carbonic anhydrase. Compound 1 demonstrated considerable efficacy against the renal RXF393, colon HT29, and melanoma LOX IMVI cancer cell lines, with IC50 values of 7.01 ± 0.39, 24.3 ± 1.29, and 9.55 ± 0.51 µM, respectively. In comparison, doxorubicin exhibited IC50 values of 13.54 ± 0.82, 13.50 ± 0.71, and 6.08 ± 0.32 µM for the corresponding cell lines. Importantly, compound 1 exhibited lower toxicity to the normal WI 38 cell line than doxorubicin, with IC50 values of 46.20 ± 2.59 and 18.13 ± 0.93 µM, respectively, indicating greater selectivity of the target compound compared to the standard anticancer agent doxorubicin. Also, mechanistic experiments demonstrated that compound 1 exhibits inhibitory activity against human carbonic anhydrase hCA IX and XII, with IC50 values of 0.477 ± 0.03 and 1.933 ± 0.11 μM, respectively, indicating enhanced selectivity for cancer-associated isoforms over cytosolic isoforms hCA I and II, with IC50 values of 7.353 ± 0.36 and 12.560 ± 0.74 μM, respectively. Cell cycle studies revealed that compound 1 caused G1 phase arrest in RXF393 cells, and apoptosis experiments verified a substantial induction of apoptosis with significant levels of early and late apoptosis, as well as necrosis (11.69%, 19.78%, and 3.66%, respectively), comparable to those induced by the conventional cytotoxic agent doxorubicin, at 9.91%, 23.37%, and 6.16%, respectively. Molecular docking experiments confirmed the strong binding affinity of compound 1 to the active sites of hCA IX and XII, highlighting significant interactions with zinc-binding groups and hydrophobic residues. These findings underscore the target compound's potential as a viable anticancer agent via targeting CA.

Design and Synthesis of 3-(Phenylsulfonamido)benzamide Derivatives as Potent Carbonic Anhydrase IX Inhibitors: Biological Evaluations and Molecular Modeling Studies

INTRODUCTION

Carbonic anhydrase IX (CAIX) is known to be overexpressed in various tumors and plays a significant role in tumor development and progression.

METHODS

A series of 3-(benzylsulfonamido)benzamides derivatives was synthesized and tested for their CAIX inhibitory activities. The two most active compounds were subjected to cytotoxicity testing against a panel of 60 cancer cell lines.

RESULTS

Many of the synthesized compounds successfully inhibited CAIX activities, exhibiting IC50 values in the low nanomolar range. The most potent CAIX inhibitor was compound 14, with an IC50 of 140 nM. Structure-activity relationship analysis of the synthesized compounds supported with molecular docking revealed strong coordination of sulfonamide moiety with the catalytic Zn2+ metal, hydrophobic interactions of the benzylsulfonamido ring with a hydrophobic pocket, and π- stacking interactions of the aryl ring with an aromatic surface. The two most active analogues (10 and 14) were further tested for their antiproliferative activities in the NCI-60 human tumor cell lines. Notably, compound 14 demonstrated potent growth inhibitory effects against several cancer cell lines.

CONCLUSION

The synthesized analogues represent a novel scaffold for the treatment of different types of cancer by targeting CAIX.

Stemness in solid malignancies: coping with immune attack

Immunotherapy has become a key new pillar of cancer treatment, and this has sparked interest in understanding mechanisms of cancer immune evasion. It has long been appreciated that cancers are constituted by heterogeneous populations of tumour cells. This feature is often fuelled by specialized cells that have molecular programs resembling tissue stem cells. Although these cancer stem cells (CSCs) have capacity for unlimited self-renewal and differentiation, it is increasingly evident that some CSCs are capable of achieving remarkable immune resistance. Given that most immunotherapy regiments have overlooked CSC-specific immune-evasive mechanisms, many current treatment strategies often lead to cancer relapse. This Review focuses on advancements in understanding how CSCs in solid tumours achieve their unique immune-evasive properties, enabling them to drive tumour regrowth. Moreover, as cancers often arise from tissue stem cells that acquired oncogenic mutations, we discuss how tissue stem cells undergoing malignant transformation activate intrinsic immune-evasive mechanisms and establish close interactions with suppressive immune cells to escape immune surveillance. In addition, we summarize how in advanced disease stages, CSCs often hijack features of normal stem cells to resist antitumour immunity. Finally, we provide insights in how to design a new generation of cancer immunotherapies to ensure elimination of CSCs.

4-(Pyrazolyl)benzenesulfonamide Ureas as Carbonic Anhydrases Inhibitors and Hypoxia-Mediated Chemo-Sensitizing Agents in Colorectal Cancer Cells

Hypoxia in tumors contributes to chemotherapy resistance, worsened by acidosis driven by carbonic anhydrases (hCA IX and XII). Targeting these enzymes can mitigate acidosis, thus enhancing tumor sensitivity to cytotoxic drugs. Herein, novel 4-(pyrazolyl)benzenesulfonamide ureas (SH7a-t) were developed and evaluated for their inhibitory activity against hCA IX and XII. They showed promising results (hCA IX: KI = 15.9-67.6 nM, hCA XII: KI = 16.7-65.7 nM). Particularly, SH7s demonstrated outstanding activity (KIs = 15.9 nM for hCA IX and 55.2 nM for hCA XII) and minimal off-target kinase inhibition over a panel of 258 kinases. In NCI anticancer screening, SH7s exhibited broad-spectrum activity with an effective growth inhibition full panel GI50 (MG-MID) value of 3.5 μM and a subpanel GI50 (MG-MID) range of 2.4-6.3 μM. Furthermore, SH7s enhanced the efficacy of Taxol and 5-fluorouracil in cotreatment regimens under hypoxic conditions in HCT-116 colorectal cancer cells, indicating its potential as a promising anticancer agent.

Emerging Role of Extracellular pH in Tumor Microenvironment as a Therapeutic Target for Cancer Immunotherapy

Identifying definitive biomarkers that predict clinical response and resistance to immunotherapy remains a critical challenge. One emerging factor is extracellular acidosis in the tumor microenvironment (TME), which significantly impairs immune cell function and contributes to immunotherapy failure. However, acidic conditions in the TME disrupt the interaction between cancer and immune cells, driving tumor-infiltrating T cells and NK cells into an inactivated, anergic state. Simultaneously, acidosis promotes the recruitment and activation of immunosuppressive cells, such as myeloid-derived suppressor cells and regulatory T cells (Tregs). Notably, tumor acidity enhances exosome release from Tregs, further amplifying immunosuppression. Tumor acidity thus acts as a "protective shield," neutralizing anti-tumor immune responses and transforming immune cells into pro-tumor allies. Therefore, targeting lactate metabolism has emerged as a promising strategy to overcome this barrier, with approaches including buffer agents to neutralize acidic pH and inhibitors to block lactate production or transport, thereby restoring immune cell efficacy in the TME. Recent discoveries have identified genes involved in extracellular pH (pHe) regulation, presenting new therapeutic targets. Moreover, ongoing research aims to elucidate the molecular mechanisms driving extracellular acidification and to develop treatments that modulate pH levels to enhance immunotherapy outcomes. Additionally, future clinical studies are crucial to validate the safety and efficacy of pHe-targeted therapies in cancer patients. Thus, this review explores the regulation of pHe in the TME and its potential role in improving cancer immunotherapy.

Exploring the Polypharmacological Potential of PCI-27483: A Selective Inhibitor of Carbonic Anhydrases IX and XII

PCI-27483, originally developed as a potent and selective inhibitor of the serine protease Factor VIIa (FVIIa) in complex with tissue factor (TF), has demonstrated significant promise in cancer therapy. In addition to its primary mechanism of action, the presence of a sulfonamide moiety in the PCI-27483 structure suggests further activities through the inhibition of carbonic anhydrases (CAs), particularly the tumor-associated human (h)CA isoforms hCA IX and XII. This study investigates the inhibitory activity of PCI-27483 against the complete panel of active hCAs, highlighting its polypharmacological potential in cancer treatment. X-ray crystallography and molecular docking studies elucidated the structural features underlying its selective inhibitory activity toward hCA IX and XII, offering insights into its dual-targeting pathway.

pH-sensing GPR68 inhibits vascular smooth muscle cell proliferation through Rap1A

Phenotypic transformation of vascular smooth muscle (VSM) from a contractile state to a synthetic, proliferative state is a hallmark of cardiovascular disease (CVD). In CVD, diseased tissue often becomes acidic from altered cellular metabolism secondary to compromised blood flow, yet the contribution of local acid/base imbalance to the disease process has been historically overlooked. In this study, we examined the regulatory impact of the pH-sensing G protein-coupled receptor GPR68 on vascular smooth muscle (VSM) proliferation in vivo and in vitro in wild-type (WT) and GPR68 knockout (KO) male and female mice. Arterial injury reduced GPR68 expression in WT vessels and exaggerated medial wall remodeling in GPR68 KO vessels. In vitro, KO VSM cells showed increased cell-cycle progression and proliferation compared with WT VSM cells, and GPR68-inducing acidic exposure reduced proliferation in WT cells. mRNA and protein expression analyses revealed increased Rap1A in KO cells compared with WT cells, and RNA silencing of Rap1A reduced KO VSM cell proliferation. In sum, these findings support a growth-inhibitory capacity of pH-sensing GPR68 and suggest a mechanistic role for the small GTPase Rap1A in GPR68-mediated VSM growth control. These results shed light on GPR68 and its effector Rap1A as potential targets to combat pathological phenotypic switching and proliferation in VSM.NEW & NOTEWORTHY Extracellular acidosis remains an understudied feature of many pathologies. We examined a potential regulatory role for pH-sensing GPR68 in vascular smooth muscle (VSM) growth in the context of CVD. With in vivo and in vitro growth models with GPR68-deficient mice and GPR68 induction strategies, novel findings revealed capacity of GPR68 to attenuate growth through the small GTPase Rap1A. These observations highlight GPR68 and its effector Rap1A as possible therapeutic targets to combat pathological VSM growth.

Combination of polymeric micelle formulation of TGFβ receptor inhibitors and paclitaxel produces consistent response across different mouse models of Triple-negative breast cancer

Triple-negative breast cancer (TNBC) is notoriously difficult to treat due to the lack of targetable receptors and sometimes poor response to chemotherapy. The transforming growth factor beta (TGFβ) family of proteins and their receptors (TGFRs) are highly expressed in TNBC and implicated in chemotherapy-induced cancer stemness. Here, we evaluated combination treatments using experimental TGFR inhibitors (TGFβi), SB525334 (SB), and LY2109761 (LY) with paclitaxel (PTX) chemotherapy. These TGFβi target TGFR-I (SB) or both TGFR-I and TGFR-II (LY). Due to the poor water solubility of these drugs, we incorporated each of them in poly(2-oxazoline) (POx) high-capacity polymeric micelles (SB-POx and LY-POx). We assessed their anticancer effect as single agents and in combination with micellar PTX (PTX-POx) using multiple immunocompetent TNBC mouse models that mimic human subtypes (4T1, T11-Apobec and T11-UV). While either TGFβi or PTX showed a differential effect in each model as single agents, the combinations were consistently effective against all three models. Genetic profiling of the tumors revealed differences in the expression levels of genes associated with TGFβ, epithelial to mesenchymal transition (EMT), TLR-4, and Bcl2 signaling, alluding to the susceptibility to specific gene signatures to the treatment. Taken together, our study suggests that TGFβi and PTX combination therapy using high-capacity POx micelle delivery provides a robust antitumor response in multiple TNBC subtype mouse models.

Enhancing Colorectal Cancer Immunotherapy: The Pivotal Role of Ferroptosis in Modulating the Tumor Microenvironment

Colorectal cancer (CRC) represents a significant challenge in oncology, with increasing incidence and mortality rates worldwide, particularly among younger adults. Despite advancements in treatment modalities, the urgent need for more effective therapies persists. Immunotherapy has emerged as a beacon of hope, offering the potential for improved outcomes and quality of life. This review delves into the critical interplay between ferroptosis, an iron-dependent form of regulated cell death, and immunotherapy within the CRC context. Ferroptosis's influence extends beyond tumor cell fate, reshaping the tumor microenvironment (TME) to enhance immunotherapy's efficacy. Investigations into Ferroptosis-related Genes (OFRGs) reveal their pivotal role in modulating immune cell infiltration and TME composition, closely correlating with tumor responsiveness to immunotherapy. The integration of ferroptosis inducers with immunotherapeutic strategies, particularly through novel approaches like ferrotherapy and targeted co-delivery systems, showcases promising avenues for augmenting treatment efficacy. Furthermore, the expression patterns of OFRGs offer novel prognostic tools, potentially guiding personalized and precision therapy in CRC. This review underscores the emerging paradigm of leveraging ferroptosis to bolster immunotherapy's impact, highlighting the need for further research to translate these insights into clinical advancements. Through a deeper understanding of the ferroptosis-immunotherapy nexus, new therapeutic strategies can be developed, promising enhanced efficacy and broader applicability in CRC treatment, ultimately improving patient outcomes and quality of life in the face of this formidable disease.

IL-22 regulates MASTL expression in intestinal epithelial cells

Microtubule-associated serine-threonine kinase-like (MASTL) has recently been identified as an oncogenic kinase given its overexpression in numerous cancers. Our group has shown that MASTL expression is upregulated in mouse models of sporadic colorectal cancer and colitis-associated cancer (CAC). CAC is one of the most severe complications of chronic inflammatory bowel disease (IBD), but a limited understanding of the mechanisms governing the switch from normal healing to neoplasia in IBD underscores the need for increased research in this area. However, MASTL levels in patients with IBD and its molecular regulation in IBD and CAC have not been studied. This study reveals that MASTL is upregulated by the cytokine interleukin (IL)-22, which promotes proliferation and has important functions in colitis recovery; however, IL-22 can also promote tumorigenesis when chronically elevated. Upon reviewing the publicly available data, we found significantly elevated MASTL and IL-22 levels in the biopsies from patients with late-stage ulcerative colitis compared with controls, and that MASTL upregulation was associated with high IL-22 expression. Our subsequent in vitro studies found that IL-22 increases MASTL expression in intestinal epithelial cell lines, which facilitates IL-22-mediated cell proliferation and downstream survival signaling. Inhibition of AKT activation abrogated IL-22-induced MASTL upregulation. We further found an increased association of carbonic anhydrase IX (CAIX) with MASTL in IL-22-treated cells, which stabilized MASTL expression. Inhibition of CAIX prevented IL-22-induced MASTL expression and cell survival. Overall, we show that IL-22/AKT signaling increases MASTL expression to promote cell survival and proliferation. Furthermore, CAIX associates with and stabilizes MASTL in response to IL-22 stimulation.NEW & NOTEWORTHY MASTL is upregulated in colorectal cancer; however, its role in colitis and colitis-associated cancer is poorly understood. This study is the first to draw a link between MASTL and IL-22, a proinflammatory/intestinal epithelial recovery-promoting cytokine that is also implicated in colon tumorigenesis. We propose that IL-22 increases MASTL protein stability by promoting its association with CAIX potentially via AKT signaling to promote cell survival and proliferation.

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.

Thetumor microenvironment'sinpancreatic cancer:Effects onimmunotherapy successandnovel strategiestoovercomethehostile environment

Cancer is a significant global health issue that poses a considerable burden on both patients and healthcare systems. Many different types of cancers exist that often require unique treatment approaches and therapies. A hallmark of tumor progression is the creation of an immunosuppressive environment, which poses complex challenges for current treatments. Amongst the most explored characteristics is a hypoxic environment, high interstitial pressure, and immunosuppressive cells and cytokines. Traditional cancer treatments involve radiotherapy, chemotherapy, and surgical procedures. The advent of immunotherapies was regarded as a promising approach with hopes of greatly increasing patients' survival and outcome. Although some success is seen with various immunotherapies, the vast majority of monotherapies are unsuccessful. This review examines how various aspects of the tumor microenvironment (TME) present challenges that impede the success of immunotherapies. Subsequently, we review strategies to manipulate the TME to facilitate the success of immunotherapies.

Hypoxia within the glioblastoma tumor microenvironment: a master saboteur of novel treatments

Glioblastoma (GBM) tumors are the most aggressive primary brain tumors in adults that, despite maximum treatment, carry a dismal prognosis. GBM tumors exhibit tissue hypoxia, which promotes tumor aggressiveness and maintenance of glioma stem cells and creates an overall immunosuppressive landscape. This article reviews how hypoxic conditions overlap with inflammatory responses, favoring the proliferation of immunosuppressive cells and inhibiting cytotoxic T cell development. Immunotherapies, including vaccines, immune checkpoint inhibitors, and CAR-T cell therapy, represent promising avenues for GBM treatment. However, challenges such as tumor heterogeneity, immunosuppressive TME, and BBB restrictiveness hinder their effectiveness. Strategies to address these challenges, including combination therapies and targeting hypoxia, are actively being explored to improve outcomes for GBM patients. Targeting hypoxia in combination with immunotherapy represents a potential strategy to enhance treatment efficacy.

Modulation of the tumor microenvironment and mechanism of immunotherapy-based drug resistance in breast cancer

Breast cancer, the most frequent female malignancy, is often curable when detected at an early stage. The treatment of metastatic breast cancer is more challenging and may be unresponsive to conventional therapy. Immunotherapy is crucial for treating metastatic breast cancer, but its resistance is a major limitation. The tumor microenvironment (TME) is vital in modulating the immunotherapy response. Various tumor microenvironmental components, such as cancer-associated fibroblasts (CAFs), tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs), are involved in TME modulation to cause immunotherapy resistance. This review highlights the role of stromal cells in modulating the breast tumor microenvironment, including the involvement of CAF-TAM interaction, alteration of tumor metabolism leading to immunotherapy failure, and other latest strategies, including high throughput genomic screening, single-cell and spatial omics techniques for identifying tumor immune genes regulating immunotherapy response. This review emphasizes the therapeutic approach to overcome breast cancer immune resistance through CAF reprogramming, modulation of TAM polarization, tumor metabolism, and genomic alterations.

Preclinical Evaluation of virus-like particle Vaccine Against Carbonic Anhydrase IX Efficacy in a Mouse Breast Cancer Model System

Carbonic anhydrase IX (CAIX) is a cancer-associated membrane protein frequently overexpressed in hypoxic solid tumours leading to enhanced tumour cell survival and invasion, and it has been proposed to be an attractive tumour-specific molecule for antibody-mediated targeting. This study aimed to generate a virus-like particle (VLP)-based CAIX vaccine candidate and evaluate its efficacy in a mouse model of breast cancer. The prototype murine vaccine was developed based on the ssRNA bacteriophage Qbeta VLPs with chemically coupled murine CAIX protein catalytic domains on their surfaces. The vaccine was shown to efficiently break the natural B cell tolerance against autologous murine CAIX and to induce high-titre Th1-oriented IgG responses in the BALB/c mice. This vaccine was tested in a therapeutic setting by using a triple-negative breast cancer mouse model system comprising 4T1, 4T1-Car9KI and 4T1-Car9KO cells, the latter representing positive and negative controls for murine CAIX production, respectively. The humoural immune responses induced in tumour-bearing animals were predominantly of Th1-type and higher anti-mCAIXc titres correlated with slower growth and lung metastasis development of 4T1 tumours constitutively expressing mCAIX in vivo in the syngeneic host.

Targeting hypoxia signaling pathways in angiogenesis

Oxygen (O2) supply is constantly maintained by the vascular network for a proper tissue oxygenation. Hypoxia is the result of an increased O2 demand and/or decreased supply and is common in both physiological conditions and human diseases. Angiogenesis is one of the adaptive responses to hypoxia and is mainly regulated by the hypoxia-inducible factors, HIFs. These heterodimeric transcription factors are composed of one of three O2-dependent α subunits (HIF-1, HIF-2, and HIF-3) and a constitutively expressed O2-insensitive subunit (HIF-1β). Among them HIF-1α is the most characterized and its activity is tightly controlled. Under hypoxia, its intracellular accumulation triggers the transcription of several genes, involved in cell survival/proliferation, autophagy, apoptosis, cell metabolism, and angiogenesis. HIF pathway is also modulated by specific microRNAs (miRNAs), thus resulting in the variation of several cellular responses, including alteration of the angiogenic process. The pro-angiogenic activity of HIF-1α is not restricted to endothelial cells, as it also affects the behavior of other cell types, including tumor and inflammatory/immune cells. In this context, exosomes play a crucial role in cell-cell communication by transferring bio-active cargos such as mRNAs, miRNAs, and proteins (e.g., VEGFA mRNA, miR210, HIF-1α). This minireview will provide a synopsis of the multiple factors able to modulate hypoxia-induced angiogenesis especially in the tumor microenvironment context. Targeting hypoxia signaling pathways by up-to-date approaches may be relevant in the design of therapeutic strategies in those pathologies where angiogenesis is dysregulated.

High hypoxia status in pancreatic cancer is associated with multiple hallmarks of an immunosuppressive tumor microenvironment

Introduction

Pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, is a particularly lethal disease that is often diagnosed late and is refractory to most forms of treatment. Tumour hypoxia is a key hallmark of PDAC and is purported to contribute to multiple facets of disease progression such as treatment resistance, increased invasiveness, metabolic reprogramming, and immunosuppression.

Methods

We used the Buffa gene signature as a hypoxia score to profile transcriptomics datasets from PDAC cases. We performed cell-type deconvolution and gene expression profiling approaches to compare the immunological phenotypes of cases with low and high hypoxia scores. We further supported our findings by qPCR analyses in PDAC cell lines cultured in hypoxic conditions.

Results

First, we demonstrated that this hypoxia score is associated with increased tumour grade and reduced survival suggesting that this score is correlated to disease progression. Subsequently, we compared the immune phenotypes of cases with high versus low hypoxia score expression (HypoxiaHI vs. HypoxiaLOW) to show that high hypoxia is associated with reduced levels of T cells, NK cells and dendritic cells (DC), including the crucial cDC1 subset. Concomitantly, immune-related gene expression profiling revealed that compared to HypoxiaLOW tumours, mRNA levels for multiple immunosuppressive molecules were notably elevated in HypoxiaHI cases. Using a Random Forest machine learning approach for variable selection, we identified LGALS3 (Galectin-3) as the top gene associated with high hypoxia status and confirmed its expression in hypoxic PDAC cell lines.

Discussion

In summary, we demonstrated novel associations between hypoxia and multiple immunosuppressive mediators in PDAC, highlighting avenues for improving PDAC immunotherapy by targeting these immune molecules in combination with hypoxia-targeted drugs.

Co-vulnerabilities of inhibiting carbonic anhydrase IX in ferroptosis-mediated tumor cell death

The tumour-associated carbonic anhydrases (CA) IX and XII are upregulated by cancer cells to combat cellular and metabolic stress imparted by hypoxia and acidosis in solid tumours. Owing to its tumour-specific expression and function, CAIX is an attractive therapeutic target and this has driven intense efforts to develop pharmacologic agents to target its activity, including small molecule inhibitors. Many studies in multiple solid tumour models have demonstrated that targeting CAIX activity with the selective CAIX/XII inhibitor, SLC-0111, results in anti-tumour efficacy, particularly when used in combination with chemotherapy or immune checkpoint blockade, and has now advanced to the clinic. However, it has been observed that sustainability and durability of CAIX inhibition, even in combination with chemotherapy agents, is limited by the occurrence of adaptive resistance, resulting in tumour recurrence. Importantly, the data from these models demonstrates that CAIX inhibition may sensitize tumour cells to cytotoxic drugs and evidence now points to ferroptosis, an iron-dependent form of regulated cell death (RCD) that results from accumulation of toxic levels of phospholipid peroxidation as a major mechanism involved in CAIX-mediated sensitization to cancer therapy. In this mini-review, we discuss recent advances demonstrating the mechanistic role CAIX plays in sensitizing cancer cells to ferroptosis.

Para-toluenesulfonamide, a novel potent carbonic anhydrase inhibitor, improves hypoxia-induced metastatic breast cancer cell viability and prevents resistance to αPD-1 therapy in triple-negative breast cancer

Overexpression of the hypoxia-induced transmembrane enzyme carbonic anhydrase IX (CA9) has been associated with poor prognosis and chemoresistance in aggressive breast cancer. This study aimed to investigate the involvement of CA9 in the anti-tumor activity of para-toluenesulfonamide (PTS) and elucidate its mechanism of action against breast cancer both in vitro and in vivo. MCF-7 and MDA-MB-231 breast cancer cells were treated with PTS or subjected to hypoxic conditions using cobalt chloride (CoCl2), with acetazolamide serving as a positive control. Additionally, 4T1 breast cancer cell allograft mice were co-treated with PTS and α-programmed cell death 1 (αPD-1) monoclonal antibody for one month. The results demonstrated that PTS effectively reduced cell viability and reversed migration ability in MCF-7 and MDA-MB-231 cells under CoCl2-induced hypoxia. Furthermore, PTS upregulated the expression of apoptosis-related proteins and downregulated CA9, hypoxia-inducible factor-1α (HIF-1α), and vascular endothelial growth factor (VEGF) proteins, possibly through modulation of p38 MAPK and ERK1/2 phosphorylated proteins. In the animal model, PTS100 inhibited tumor growth and lung metastasis in mammary tumor allograft mice, exhibiting synergistic effects when combined with αPD-1 therapy. Collectively, our findings suggest that PTS inhibits breast cancer growth and metastasis through the p38 MAPK/ERK1/2 pathway. Moreover, PTS may have the potential to prevent the development of resistance to αPD-1 therapy in breast cancer.

Leveraging hypoxia in triple-negative breast cancer as a promising treatment strategy

Current treatment strategies for triple-negative breast cancer (TNBC) are based upon conventional chemotherapy, immunotherapy, or a combination of both. The treatment regimen for chemotherapy is often a combination of two or more drugs, either dose dense or low dose for synergy. Anthracyclines, alkylating agents, antimicrotubule agents, and antimetabolites for early-stage TNBC; and antimetabolites, non-taxane microtubule inhibitors, and cross-linker platinums for late-stage TNBC are usually administered in the clinical setting. Newer options for patients with advanced TNBC, such as poly (ADP-ribose) polymerase (PARP) inhibitors and immune checkpoint inhibitors, have recently emerged for cases where surgery is not a viable option and the disease has metastasized. This review outlines the current trends in hypoxia-inspired treatment strategies for TNBC with a focus on clinical trials.

Innate lymphoid cells and tumor-derived lactic acid: novel contenders in an enduring game

Aerobic glycolysis, also known as the Warburg effect, has for a prolonged period of time been perceived as a defining feature of tumor metabolism. The redirection of glucose utilization towards increased production of lactate by cancer cells enables their rapid proliferation, unceasing growth, and longevity. At the same time, it serves as a significant contributor to acidification of the tumor microenvironment, which, in turn, imposes substantial constraints on infiltrating immune cells. Here, we delve into the influence of tumor-derived lactic acid on innate lymphoid cells (ILCs) and discuss potential therapeutic approaches. Given the abundance of ILCs in barrier tissues such as the skin, we provide insights aimed at translating this knowledge into therapies that may specifically target skin cancer.

Recent research and clinical progress of CTLA-4-based immunotherapy for breast cancer

Breast cancer is characterized by a high incidence rate and its treatment challenges, particularly in certain subtypes. Consequently, there is an urgent need for the development of novel therapeutic approaches. Immunotherapy utilizing immune checkpoint inhibitors (ICIs) is currently gaining momentum for the treatment of breast cancer. Substantial progress has been made in clinical studies employing cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) inhibitors for breast cancer, but the cure rates are relatively low. To improve the efficacy of CTLA-4-based therapy for breast cancer, further research is imperative to explore more effective immune-based treatment strategies. In addition to monotherapy, CTLA-4 inhibitors are also being investigated in combination with other ICIs or alternative medications. However, it should be noted that immune-based treatments may cause adverse events. This review focuses on the mechanisms of CTLA-4 inhibitor monotherapy or combination therapy in breast cancer. We systematically summarize the latest research and clinical advances in CTLA-4-based immunotherapy for breast cancer, providing new perspectives on the treatment of breast cancer. In addition, this review highlights the immune-related adverse events (irAEs) associated with CTLA-4 inhibitors, providing insights into the development of appropriate clinical tumor immunotherapy regimens and intervention strategies.

A Carbonic Anhydrase IX/SLC1A5 Axis Regulates Glutamine Metabolism Dependent Ferroptosis in Hypoxic Tumor Cells

The ability of tumor cells to alter their metabolism to support survival and growth presents a challenge to effectively treat cancers. Carbonic anhydrase IX (CAIX) is a hypoxia-induced, metabolic enzyme that plays a crucial role in pH regulation in tumor cells. Recently, through a synthetic lethal screen, we identified CAIX to play an important role in redox homeostasis. In this study, we show that CAIX interacts with the glutamine (Gln) transporter, solute carrier family 1 member 5 (SLC1A5), and coordinately functions to maintain redox homeostasis through the glutathione/glutathione peroxidase 4 (GSH/GPX4) axis. Inhibition of CAIX increases Gln uptake by SLC1A5 and concomitantly increases GSH levels. The combined inhibition of CAIX activity and Gln metabolism or the GSH/GPX4 axis results in an increase in lipid peroxidation and induces ferroptosis, both in vitro and in vivo. Thus, this study demonstrates cotargeting of CAIX and Gln metabolism as a potential strategy to induce ferroptosis in tumor cells.

Association between pH regulation of the tumor microenvironment and immunological state

The tumor microenvironment (TME) is characterized by interactions among various cells, including tumor cells, immune cells, stromal cells, and blood vessels mediated by factors such as cytokines and metabolites. The development of cancer immunotherapy in recent years has facilitated a more comprehensive understanding of the TME. The TME changes with cancer type and host immune status, as well as with therapeutic intervention. However, studies on pH regulation of the TME have been mostly based on lactate, a metabolite of tumor cells. Notably, the Warburg effect results in the increased production of secreted lactate, thereby acidifying the extracellular microenvironment and affecting the surrounding cells. Lactate inhibits the activation and proliferation of CD8+ T cells, M1 macrophages, natural killer (NK) cells, and dendritic cells, contributing to tumor cell immune escape. It is also involved in angiogenesis and tissue remodeling, as well as promotes tumor growth and invasion. In this review, we have discussed the lactate-based pH regulation in tumor cells in the TME and its effects on the other constituent cells.

Targeting Transcription Factor YY1 for Cancer Treatment: Current Strategies and Future Directions

Cancer represents a significant and persistent global health burden, with its impact underscored by its prevalence and devastating consequences. Whereas numerous oncogenes could contribute to cancer development, a group of transcription factors (TFs) are overactive in the majority of tumors. Targeting these TFs may also combat the downstream oncogenes activated by the TFs, making them attractive potential targets for effective antitumor therapeutic strategy. One such TF is yin yang 1 (YY1), which plays crucial roles in the development and progression of various tumors. In preclinical studies, YY1 inhibition has shown efficacy in inhibiting tumor growth, promoting apoptosis, and sensitizing tumor cells to chemotherapy. Recent studies have also revealed the potential of combining YY1 inhibition with immunotherapy for enhanced antitumor effects. However, clinical translation of YY1-targeted therapy still faces challenges in drug specificity and delivery. This review provides an overview of YY1 biology, its role in tumor development and progression, as well as the strategies explored for YY1-targeted therapy, with a focus on their clinical implications, including those using small molecule inhibitors, RNA interference, and gene editing techniques. Finally, we discuss the challenges and current limitations of targeting YY1 and the need for further research in this area.

Combination of Polymeric Micelle Formulation of TGFβ Receptor Inhibitors and Paclitaxel Produce Consistent Response Across Different Mouse Models of TNBC

Triple-negative breast cancer (TNBC) is notoriously difficult to treat due to the lack of targetable receptors and sometimes poor response to chemotherapy. The transforming growth factor-beta (TGFβ) family of proteins and their receptors (TGFR) are highly expressed in TNBC and implicated in chemotherapy-induced cancer stemness. Here we evaluated combination treatments using experimental TGFR inhibitors (TGFβi), SB525334 (SB), and LY2109761 (LY) with Paclitaxel (PTX) chemotherapy. These TGFβi target TGFR-I (SB) or both TGFR-I&II (LY). Due to the poor water solubility of these drugs, we incorporated each of them in poly(2-oxazoline) (POx) high-capacity polymeric micelles (SB-POx and LY-POx). We assessed their anti-cancer effect as single agents and in combination with micellar Paclitaxel (PTX-POx) using multiple immunocompetent TNBC mouse models that mimic human subtypes (4T1, T11-Apobec and T11-UV). While either TGFβi or PTX showed a differential effect in each model as single agents, the combinations were consistently effective against all three models. Genetic profiling of the tumors revealed differences in the expression levels of genes associated with TGFβ, EMT, TLR-4, and Bcl2 signaling, alluding to the susceptibility to specific gene signatures to the treatment. Taken together, our study suggests that TGFβi and PTX combination therapy using high-capacity POx micelle delivery provides a robust anti-tumor response in multiple TNBC subtype mouse models.

Carbonic Anhydrase IX Suppression Shifts Partial Response to Checkpoint Inhibitors into Complete Tumor Eradication: Model-Based Investigation

Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of solid malignancies, including non-small-cell lung cancer. However, immunotherapy resistance constitutes a significant challenge. To investigate carbonic anhydrase IX (CAIX) as a driver of resistance, we built a differential equation model of tumor-immune interactions. The model considers treatment with the small molecule CAIX inhibitor SLC-0111 in combination with ICIs. Numerical simulations showed that, given an efficient immune response, CAIX KO tumors tended toward tumor elimination in contrast to their CAIX-expressing counterparts, which stabilized close to the positive equilibrium. Importantly, we demonstrated that short-term combination therapy with a CAIX inhibitor and immunotherapy could shift the asymptotic behavior of the original model from stable disease to tumor eradication. Finally, we calibrated the model with data from murine experiments on CAIX suppression and combination therapy with anti-PD-1 and anti-CTLA-4. Concluding, we have developed a model that reproduces experimental findings and enables the investigation of combination therapies. Our model suggests that transient CAIX inhibition may induce tumor regression, given a sufficient immune infiltrate in the tumor, which can be boosted with ICIs.

Glutamine metabolism in breast cancer and possible therapeutic targets

Cancer is characterized by metabolic reprogramming, which is a hot topic in tumor treatment research. Cancer cells alter metabolic pathways to promote their growth, and the common purpose of these altered metabolic pathways is to adapt the metabolic state to the uncontrolled proliferation of cancer cells. Most cancer cells in a state of nonhypoxia will increase the uptake of glucose and produce lactate, called the Warburg effect. Increased glucose consumption is used as a carbon source to support cell proliferation, including nucleotide, lipid and protein synthesis. In the Warburg effect, pyruvate dehydrogenase activity decreases, thereby disrupting the TCA cycle. In addition to glucose, glutamine is also an important nutrient for the growth and proliferation of cancer cells, an important carbon bank and nitrogen bank for the growth and proliferation of cancer cells, providing ribose, nonessential amino acids, citrate, and glycerin necessary for cancer cell growth and proliferation and compensating for the reduction in oxidative phosphorylation pathways in cancer cells caused by the Warburg effect. In human plasma, glutamine is the most abundant amino acid. Normal cells produce glutamine via glutamine synthase (GLS), but the glutamine synthesized by tumor cells is insufficient to meet their high growth needs, resulting in a "glutamine-dependent phenomenon." Most cancers have an increased glutamine demand, including breast cancer. Metabolic reprogramming not only enables tumor cells to maintain the reduction-oxidation (redox) balance and commit resources to biosynthesis but also establishes heterogeneous metabolic phenotypes of tumor cells that are distinct from those of nontumor cells. Thus, targeting the metabolic differences between tumor and nontumor cells may be a promising and novel anticancer strategy. Glutamine metabolic compartments have emerged as promising candidates, especially in TNBC and drug-resistant breast cancer. In this review, the latest discoveries of breast cancer and glutamine metabolism are discussed, novel treatment methods based on amino acid transporters and glutaminase are discussed, and the relationship between glutamine metabolism and breast cancer metastasis, drug resistance, tumor immunity and ferroptosis are explained, which provides new ideas for the clinical treatment of breast cancer.

CA-IX-Expressing Small Extracellular Vesicles (sEVs) Are Released by Melanoma Cells under Hypoxia and in the Blood of Advanced Melanoma Patients

Cutaneous melanoma is a highly aggressive skin cancer, with poor prognosis. The tumor microenvironment is characterized by areas of hypoxia. Carbonic anhydrase IX (CA-IX) is a marker of tumor hypoxia and its expression is regulated by hypoxia-inducible factor-1 (HIF-1). CA-IX has been found to be highly expressed in invasive melanomas. In this study, we investigated the effects of hypoxia on the release of small extracellular vesicles (sEVs) in two melanoma in vitro models. We demonstrated that melanoma cells release sEVs under both normoxic and hypoxic conditions, but only hypoxia-induced sEVs express CA-IX mRNA and protein. Moreover, we optimized an ELISA assay to provide evidence for CA-IX protein expression on the membranes of the sEVs. These CA-IX-positive sEVs may be exploited as potential biomarkers for liquid biopsy.

Exploring the Role of Hypoxia-Inducible Carbonic Anhydrase IX (CAIX) in Circulating Tumor Cells (CTCs) of Breast Cancer

Circulating tumor cells (CTCs) in the peripheral blood are believed to be the source of metastasis and can be used as a liquid biopsy to monitor cancer progression and therapeutic response. However, it has been challenging to accurately detect CTCs because of their low frequency and the heterogeneity of the population. In this study, we have developed an in vitro model of CTCs by using non-adherent suspension culture. We used this model to study a group of breast cancer cell lines with distinct molecular subtypes (TNBC, HER2⁺, and ER⁺/PR⁺). We found that, when these breast cancer cell lines lost their attachment to the extracellular matrix, they accumulated a subtype of cancer stem cells (CSC) that expressed the surface markers of stem cells (e.g., CD44⁺CD24^-). These stem-like CTCs also showed high expressions of hypoxia-inducible gene products, particularly the hypoxia-inducible carbonic anhydrase IX (CAIX). Inhibition of CAIX activity was found to reduce CAIX expression and stem cell phenotypes in the targeted CTCs. Further studies are needed, using CTC samples from breast cancer patients, to determine the role of CAIX in CTC survival, CSC transition, and metastasis. CAIX may be a useful surface marker for the detection of CSCs in the blood, and a potential target for treating metastatic breast cancers.

CAXII inhibitors: Potential sensitizers for immune checkpoint inhibitors in HCC treatment

Hepatocellular carcinoma (HCC) is a lethal malignancy with a lack of effective treatments particularly for the disease at an advanced stage. Even though immune checkpoint inhibitors (ICIs) have made great progress in the treatment of HCC, durable and ideal clinical benefits still cannot be achieved in plenty of patients with HCC. Therefore, novel and refined ICI-based combination therapies are still needed to enhance the therapeutic effect. The latest study has reported that the carbonic anhydrase XII inhibitor (CAXIIi), a novel type of anticancer drug, can modify the tumor immunosuppression microenvironment by affecting hypoxic/acidic metabolism and alter the functions of monocytes and macrophages by regulating the expression of C-C motif chemokine ligand 8 (CCL8). These observations shine a light on improving programmed cell death protein 1 (PD-1)/programmed cell death ligand-1 (PD-L1) immunotherapy in combination with CAXIIis. This mini-review aims to ignite enthusiasm to explore the potential application of CAXIIis in combination with immunotherapy for HCC.

Hypoxia, a Targetable Culprit to Counter Pancreatic Cancer Resistance to Therapy

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer, and it is a disease of dismal prognosis. While immunotherapy has revolutionized the treatment of various solid tumors, it has achieved little success in PDAC. Hypoxia within the stroma-rich tumor microenvironment is associated with resistance to therapies and promotes angiogenesis, giving rise to a chaotic and leaky vasculature that is inefficient at shuttling oxygen and nutrients. Hypoxia and its downstream effectors have been implicated in immune resistance and could be contributing to the lack of response to immunotherapy experienced by patients with PDAC. Paradoxically, increasing evidence has shown hypoxia to augment genomic instability and mutagenesis in cancer, suggesting that hypoxic tumor cells could have increased production of neoantigens that can potentially enable their clearance by cytotoxic immune cells. Strategies aimed at relieving this condition have been on the rise, and one such approach opts for normalizing the tumor vasculature to reverse hypoxia and its downstream support of tumor pathogenesis. An important consideration for the successful implementation of such strategies in the clinic is that not all PDACs are equally hypoxic, therefore hypoxia-detection approaches should be integrated to enable optimal patient selection for achieving improved patient outcomes.

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.

Facts and Perspectives: Implications of tumor glycolysis on immunotherapy response in triple negative breast cancer

Triple negative breast cancer (TNBC) is an aggressive disease that is difficult to treat and portends a poor prognosis in many patients. Recent efforts to implement immune checkpoint inhibitors into the treatment landscape of TNBC have led to improved outcomes in a subset of patients both in the early stage and metastatic settings. However, a large portion of patients with TNBC remain resistant to immune checkpoint inhibitors and have limited treatment options beyond cytotoxic chemotherapy. The interplay between the anti-tumor immune response and tumor metabolism contributes to immunotherapy response in the preclinical setting, and likely in the clinical setting as well. Specifically, tumor glycolysis and lactate production influence the tumor immune microenvironment through creation of metabolic competition with infiltrating immune cells, which impacts response to immune checkpoint blockade. In this review, we will focus on how glucose metabolism within TNBC tumors influences the response to immune checkpoint blockade and potential ways of harnessing this information to improve clinical outcomes.

The Tumor Microenvironment in Tumorigenesis and Therapy Resistance Revisited

Tumorigenesis is a complex and dynamic process involving cell-cell and cell-extracellular matrix (ECM) interactions that allow tumor cell growth, drug resistance and metastasis. This review provides an updated summary of the role played by the tumor microenvironment (TME) components and hypoxia in tumorigenesis, and highlight various ways through which tumor cells reprogram normal cells into phenotypes that are pro-tumorigenic, including cancer associated- fibroblasts, -macrophages and -endothelial cells. Tumor cells secrete numerous factors leading to the transformation of a previously anti-tumorigenic environment into a pro-tumorigenic environment. Once formed, solid tumors continue to interact with various stromal cells, including local and infiltrating fibroblasts, macrophages, mesenchymal stem cells, endothelial cells, pericytes, and secreted factors and the ECM within the tumor microenvironment (TME). The TME is key to tumorigenesis, drug response and treatment outcome. Importantly, stromal cells and secreted factors can initially be anti-tumorigenic, but over time promote tumorigenesis and induce therapy resistance. To counter hypoxia, increased angiogenesis leads to the formation of new vascular networks in order to actively promote and sustain tumor growth via the supply of oxygen and nutrients, whilst removing metabolic waste. Angiogenic vascular network formation aid in tumor cell metastatic dissemination. Successful tumor treatment and novel drug development require the identification and therapeutic targeting of pro-tumorigenic components of the TME including cancer-associated- fibroblasts (CAFs) and -macrophages (CAMs), hypoxia, blocking ECM-receptor interactions, in addition to the targeting of tumor cells. The reprogramming of stromal cells and the immune response to be anti-tumorigenic is key to therapeutic success. Lastly, this review highlights potential TME- and hypoxia-centered therapies under investigation.

An in silico model to study the impact of carbonic anhydrase IX expression on tumour growth and anti-PD-1 therapy

Immune checkpoint inhibitors (ICIs) are revolutionary cancer treatments. However, the mechanisms behind their effectiveness are not yet fully understood. Here, we aimed to investigate the role of the pH-regulatory enzyme carbonic anhydrase IX (CAIX) in ICI success. Consequently, we developed an in silico model of the tumour microenvironment. The hybrid model consists of an agent-based model of tumour-immune cell interactions, coupled with a set of diffusion-reaction equations describing substances in the environment. It is calibrated with data from the literature, enabling the study of its qualitative behaviour. In our model, CAIX-expressing tumours acidified their neighbourhood, thereby reducing immune infiltration by 90% (p < 0.001) and resulting in a 25% increase in tumour burden (p < 0.001). Moreover, suppression of CAIX improved the response to anti-PD-1 (23% tumour reduction in CAIX knockouts and 6% in CAIX-expressing tumours, p < 0.001), independently of initial PD-L1 expression. Our simulations suggest that patients with CAIX-expressing tumours could respond favourably to combining ICIs with CAIX suppression, even in the absence of pre-treatment PD-L1 expression. Furthermore, when calibrated with tumour-type-specific data, our model could serve as a high-throughput tool for testing the effectiveness of such a combinatorial approach.

Targeting lactate metabolism for cancer immunotherapy - a matter of precision

Immune checkpoint inhibitors and adoptive T cell therapies have been valuable additions to the toolbox in the fight against cancer. These treatments have profoundly increased the number of patients with a realistic perspective toward a return to a cancer-free life. Yet, in a number of patients and tumor entities, cancer immunotherapies have been ineffective so far. In solid tumors, immune exclusion and the immunosuppressive tumor microenvironment represent substantial roadblocks to successful therapeutic outcomes. A major contributing factor to the depressed anti-tumor activity of immune cells in tumors is the harsh metabolic environment. Hypoxia, nutrient competition with tumor and stromal cells, and accumulating noxious waste products, including lactic acid, pose massive constraints to anti-tumor immune cells. Numerous strategies are being developed to exploit the metabolic vulnerabilities of tumor cells in the hope that these would also alleviate metabolism-inflicted immune suppression. While promising in principle, especially in combination with immunotherapies, these strategies need to be scrutinized for their effect on tumor-fighting immune cells, which share some of their key metabolic properties with tumor cells. Here, we provide an overview of strategies that seek to tackle lactate metabolism in tumor or immune cells to unleash anti-tumor immune responses, thereby opening therapeutic options for patients whose tumors are currently not treatable.

Metabolic modulation of immune checkpoints and novel therapeutic strategies in cancer

Cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) or programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1)-based immune checkpoint inhibitors (ICIs) have led to significant improvements in the overall survival of patients with certain cancers and are expected to benefit patients by achieving complete, long-lasting remissions and cure. However, some patients who receive ICIs either fail treatment or eventually develop immunotherapy resistance. The existence of such patients necessitates a deeper understanding of cancer progression, specifically nutrient regulation in the tumor microenvironment (TME), which includes both metabolic cross-talk between metabolites and tumor cells, and intracellular metabolism in immune and cancer cells. Here we review the features and behaviors of the TME and discuss the recently identified major immune checkpoints. We comprehensively and systematically summarize the metabolic modulation of tumor immunity and immune checkpoints in the TME, including glycolysis, amino acid metabolism, lipid metabolism, and other metabolic pathways, and further discuss the potential metabolism-based therapeutic strategies tested in preclinical and clinical settings. These findings will help to determine the existence of a link or crosstalk between tumor metabolism and immunotherapy, which will provide an important insight into cancer treatment and cancer research.

Unraveling tumor microenvironment of small-cell lung cancer: Implications for immunotherapy

Small-cell lung cancer (SCLC) is an aggressive lung cancer subtype and its first-line treatment has remained unchanged for decades. In recent years, immunotherapy has emerged as a therapeutic strategy for tumor treatment, whereas, patients with SCLC exhibit poor overall responses to immunotherapy alone, which highlights the necessity for combinatorial approaches. The tumor microenvironment (TME), an integral component in cancer, is widely implicated in tumorigenesis and tumor metastasis. The interactions of various cells within TME shape the adverse conditions of the tumor microenvironment (characterized by hypoxia, nutrient restriction, and acidity) and are considered responsible for the modest therapeutic responses to immunotherapy. Several studies have suggested that adverse TME can regulate immune cell activation and function. However, the specific regulatory mechanisms and their implications on immunotherapy remain unclear. Thus, it is worth unraveling the characteristics of TME and its impact on antitumor immunity, in the hope of devising novel strategies to reinforce immunotherapeutic effects on SCLC. In this review, we firstly elaborate on the immune landscape of SCLC and the formation of three remarkable characteristics in TME, as well as the interaction among them. Next, we summarize the latest findings regarding the impacts of adverse TME on immune cells and its targeted therapy in SCLC. Finally, we discuss the ongoing trials in combination therapy and potential directions of SCLC therapy. Collectively, the findings combined here are expected to aid the design of trials for combining immunotherapy with therapy targeting the TME of SCLC.

Carbonic anhydrase IX: A tumor acidification switch in heterogeneity and chemokine regulation

The primary physiological process of respiration produces carbon dioxide (CO₂) that reacts with water molecules which subsequently liberates bicarbonate (HCO-₃) and protons. Carbonic anhydrases (CAs) are the primary catalyst involved in this conversion. More than 16 isoforms of human CAs show organ or subcellular specific activity. Dysregulation of each CA is associated with multiple pathologies. Out of these members, the overexpression of membrane-bound carbonic anhydrase IX (CAIX) is associated explicitly with hypoxic tumors or various solid cancers. CAIX helps tumors deal with higher CO₂ by sequestering it with bicarbonate ions and helping cancer cells to grow in a comparatively hypoxic or acidic environment, thus acting as a pH adaptation switch. CAIX-mediated adaptations in cancer cells include angiogenesis, metabolic alterations, tumor heterogeneity, drug resistance, and regulation of cancer-specific chemokines. This review comprehensively collects and describe the cancer-specific expression mechanism and role of CAIX in cancer growth, progression, heterogeneity, and its structural insight to develop future combinatorial targeted cancer therapies.

Biodegradable Ferrous Sulfide-Based Nanocomposites for Tumor Theranostics through Specific Intratumoral Acidosis-Induced Metabolic Symbiosis Disruption

Abnormal metabolic symbiosis is a typical characteristic that differentiates the tumor regions from healthy tissues and meanwhile maintains tumor survival. It is of great potential to disrupt intratumoral metabolic symbiosis in tumor therapy. Herein, we report a specific tumor therapy strategy through inducing acidosis to disrupt intratumoral metabolic symbiosis for tumor elimination, which is based on carbonic anhydrase inhibitor (CAI)-modified ferrous sulfide nanoparticles (FeS-PEG-CAI NPs). The FeS-PEG-CAI NPs show the acid-responsive degradation capacity to release functional components, including CAI, Fe²⁺, and H₂S, while remaining quite stable under normal physiological conditions. The generated CAI and H₂S gas can not only disrupt the intracellular metabolic symbiosis to induce acidosis but also provide suitable circumstances for Fe²⁺-mediated Fenton reaction, producing abundant toxic hydroxyl radicals. Meanwhile, these NPs also show the dual-mode imaging capacity with photoacoustic and magnetic resonance imaging, which can dynamically monitor tumor location in the process of synergistic chemodynamic/photothermal/gas therapy. Overall, the developed FeS-PEG-CAI NPs exert their role of disrupting intratumoral metabolic symbiosis and other synergistic effects, which further enrich tumor treatment strategies.