Hypoxia-mediated drug resistance: novel insights on the functional interaction of HIFs and cell death pathways

HIF-1 mediated metabolic reprogramming in cancer: Mechanisms and therapeutic implications

Cancer cells undergo metabolic reprogramming to survive in hypoxic conditions and meet the elevated energy demands of the cancer microenvironment. This metabolic alteration is orchestrated by hypoxia-inducible factor 1 (HIF-1), regulating various processes within cancer cells. The intricate metabolic modifications induced by hypoxia underscore the significance of HIF-1-induced metabolic reprogramming in promoting each aspect of cancer progression. The complex interactions between HIF-1 signalling and cellular metabolic processes in response to hypoxia are examined in this study, focusing on the metabolism of carbohydrates, nucleotides, lipids, and amino acids. Comprehending the various regulatory mechanisms controlled by HIF-1 in cellular metabolism sheds light on the intricate biology of cancer growth and offers useful insights for developing targeted treatments.

Role and recent progress of P2Y12 receptor in cancer development

P2Y12 receptor (P2Y12R) is an adenosine-activated G protein-coupled receptor (GPCR) that plays a central role in platelet function, hemostasis, and thrombosis. P2Y12R activation can promote platelet aggregation and adhesion to cancer cells, promote tumor angiogenesis, and affect the tumor immune microenvironment (TIME) and tumor drug resistance, which is conducive to the progression of cancers. Meanwhile, P2Y12R inhibitors can inhibit this effect, suggesting that P2Y12R may be a potential therapeutic target for cancer. P2Y12R is involved in cancer development and metastasis, while P2Y12R inhibitors are effective in inhibiting cancer. However, a new study suggests that long-term use of P2Y12R inhibitors may increase the risk of cancer and the mechanism remains to be explored. In this paper, we reviewed the structural and functional characteristics of P2Y12R and its role in cancer. We explored the role of P2Y12R inhibitors in different tumors and the latest advances by summarizing the basic and clinical studies on the effects of P2Y12R inhibitors on tumors.

New insights into the interaction between m6A modification and lncRNA in cancer drug resistance

Drug resistance is perhaps the greatest obstacle in improving outcomes for cancer patients, leading to recurrence, progression and metastasis of various cancers. Exploring the underlying mechanism worth further study. N6-methyladenosine (m6A) is the most common RNA modification found in eukaryotes, playing a vital role in RNA translation, transportation, stability, degradation, splicing and processing. Long noncoding RNA (lncRNA) refers to a group of transcripts that are longer than 200 nucleotides (nt) and typically lack the ability to code for proteins. LncRNA has been identified to play a significant role in regulating multiple aspects of tumour development and progression, including proliferation, metastasis, metabolism, and resistance to treatment. In recent years, a growing body of evidence has emerged, highlighting the crucial role of the interplay between m6A modification and lncRNA in determining the sensitivity of cancer cells to chemotherapeutic agents. In this review, we focus on the recent advancements in the interaction between m6A modification and lncRNA in the modulation of cancer drug resistance. Additionally, we aim to explore the underlying mechanisms involved in this process. The objective of this review is to provide valuable insights and suggest potential future directions for the reversal of chemoresistance in cancer.

Mitochondrial dysfunction induced by HIF-1α under hypoxia contributes to the development of gastric mucosal lesions

INTRODUCTION

Hypoxia is an important characteristic of gastric mucosal diseases, and hypoxia-inducible factor-1α (HIF-1α) contributes to microenvironment disturbance and metabolic spectrum abnormalities. However, the underlying mechanism of HIF-1α and its association with mitochondrial dysfunction in gastric mucosal lesions under hypoxia have not been fully clarified.

OBJECTIVES

To evaluate the effects of hypoxia-induced HIF-1α on the development of gastric mucosal lesions.

METHODS

Portal hypertensive gastropathy (PHG) and gastric cancer (GC) were selected as representative diseases of benign and malignant gastric lesions, respectively. Gastric tissues from patients diagnosed with the above diseases were collected. Portal hypertension (PHT)-induced mouse models in METTL3 mutant or NLRP3-deficient littermates were established, and nude mouse gastric graft tumour models with relevant inhibitors were generated. The mechanisms underlying hypoxic condition, mitochondrial dysfunction and metabolic alterations in gastric mucosal lesions were further analysed.

RESULTS

HIF-1α, which can mediate mitochondrial dysfunction via upregulation of METTL3/IGF2BP3-dependent dynamin-related protein 1 (Drp1) N6-methyladenosine modification to increase mitochondrial reactive oxygen species (mtROS) production, was elevated under hypoxic conditions in human and mouse portal hypertensive gastric mucosa and GC tissues. While blocking HIF-1α with PX-478, inhibiting Drp1-dependent mitochondrial fission via mitochondrial division inhibitor 1 (Mdivi-1) treatment or METTL3 mutation alleviated this process. Furthermore, HIF-1α influenced energy metabolism by enhancing glycolysis via lactate dehydrogenase A. In addition, HIF-1α-induced Drp1-dependent mitochondrial fission also enhanced glycolysis. Drp1-dependent mitochondrial fission and enhanced glycolysis were associated with alterations in antioxidant enzyme activity and dysfunction of the mitochondrial electron transport chain, resulting in massive mtROS production, which was needed for activation of NLRP3 inflammasome to aggravate the development of the PHG and GC.

CONCLUSIONS

Under hypoxic conditions, HIF-1α enhances mitochondrial dysfunction via Drp1-dependent mitochondrial fission and influences the metabolic profile by altering glycolysis to increase mtROS production, which can trigger NLRP3 inflammasome activation and mucosal microenvironment alterations to contribute to the development of benign and malignant gastric mucosal lesions.

Ferroptosis in cancer: From molecular mechanisms to therapeutic strategies

Ferroptosis is a non-apoptotic form of regulated cell death characterized by the lethal accumulation of iron-dependent membrane-localized lipid peroxides. It acts as an innate tumor suppressor mechanism and participates in the biological processes of tumors. Intriguingly, mesenchymal and dedifferentiated cancer cells, which are usually resistant to apoptosis and traditional therapies, are exquisitely vulnerable to ferroptosis, further underscoring its potential as a treatment approach for cancers, especially for refractory cancers. However, the impact of ferroptosis on cancer extends beyond its direct cytotoxic effect on tumor cells. Ferroptosis induction not only inhibits cancer but also promotes cancer development due to its potential negative impact on anticancer immunity. Thus, a comprehensive understanding of the role of ferroptosis in cancer is crucial for the successful translation of ferroptosis therapy from the laboratory to clinical applications. In this review, we provide an overview of the recent advancements in understanding ferroptosis in cancer, covering molecular mechanisms, biological functions, regulatory pathways, and interactions with the tumor microenvironment. We also summarize the potential applications of ferroptosis induction in immunotherapy, radiotherapy, and systemic therapy, as well as ferroptosis inhibition for cancer treatment in various conditions. We finally discuss ferroptosis markers, the current challenges and future directions of ferroptosis in the treatment of cancer.

Tumour response to hypoxia: understanding the hypoxic tumour microenvironment to improve treatment outcome in solid tumours

Hypoxia is a common feature of solid tumours affecting their biology and response to therapy. One of the main transcription factors activated by hypoxia is hypoxia-inducible factor (HIF), which regulates the expression of genes involved in various aspects of tumourigenesis including proliferative capacity, angiogenesis, immune evasion, metabolic reprogramming, extracellular matrix (ECM) remodelling, and cell migration. This can negatively impact patient outcomes by inducing therapeutic resistance. The importance of hypoxia is clearly demonstrated by continued research into finding clinically relevant hypoxia biomarkers, and hypoxia-targeting therapies. One of the problems is the lack of clinically applicable methods of hypoxia detection, and lack of standardisation. Additionally, a lot of the methods of detecting hypoxia do not take into consideration the complexity of the hypoxic tumour microenvironment (TME). Therefore, this needs further elucidation as approximately 50% of solid tumours are hypoxic. The ECM is important component of the hypoxic TME, and is developed by both cancer associated fibroblasts (CAFs) and tumour cells. However, it is important to distinguish the different roles to develop both biomarkers and novel compounds. Fibronectin (FN), collagen (COL) and hyaluronic acid (HA) are important components of the ECM that create ECM fibres. These fibres are crosslinked by specific enzymes including lysyl oxidase (LOX) which regulates the stiffness of tumours and induces fibrosis. This is partially regulated by HIFs. The review highlights the importance of understanding the role of matrix stiffness in different solid tumours as current data shows contradictory results on the impact on therapeutic resistance. The review also indicates that further research is needed into identifying different CAF subtypes and their exact roles; with some showing pro-tumorigenic capacity and others having anti-tumorigenic roles. This has made it difficult to fully elucidate the role of CAFs within the TME. However, it is clear that this is an important area of research that requires unravelling as current strategies to target CAFs have resulted in worsened prognosis. The role of immune cells within the tumour microenvironment is also discussed as hypoxia has been associated with modulating immune cells to create an anti-tumorigenic environment. Which has led to the development of immunotherapies including PD-L1. These hypoxia-induced changes can confer resistance to conventional therapies, such as chemotherapy, radiotherapy, and immunotherapy. This review summarizes the current knowledge on the impact of hypoxia on the TME and its implications for therapy resistance. It also discusses the potential of hypoxia biomarkers as prognostic and predictive indictors of treatment response, as well as the challenges and opportunities of targeting hypoxia in clinical trials.

Analysis of anemia and iron supplementation among glioblastoma patients reveals sex-biased association between anemia and survival

The association between anemia and outcomes in glioblastoma patients is unclear. We analyzed data from 1346 histologically confirmed adult glioblastoma patients in the TriNetX Research Network. Median hemoglobin and hematocrit levels were quantified for 6 months following diagnosis and used to classify patients as anemic or non-anemic. Associations of anemia and iron supplementation of anemic patients with median overall survival (median-OS) were then studied. Among 1346 glioblastoma patients, 35.9% of male and 40.5% of female patients were classified as anemic using hemoglobin-based WHO guidelines. Among males, anemia was associated with reduced median-OS compared to matched non-anemic males using hemoglobin (HR 1.24; 95% CI 1.00-1.53) or hematocrit-based cutoffs (HR 1.28; 95% CI 1.03-1.59). Among females, anemia was not associated with median-OS using hemoglobin (HR 1.00; 95% CI 0.78-1.27) or hematocrit-based cutoffs (HR: 1.10; 95% CI 0.85-1.41). Iron supplementation of anemic females trended toward increased median-OS (HR 0.61; 95% CI 0.32-1.19) although failing to reach statistical significance whereas no significant association was found in anemic males (HR 0.85; 95% CI 0.41-1.75). Functional transferrin-binding assays confirmed sexually dimorphic binding in resected patient samples indicating underlying differences in iron biology. Anemia among glioblastoma patients exhibits a sex-specific association with survival.

Associations between HIFs and tumor immune checkpoints: mechanism and therapy

Hypoxia, which activates a variety of signaling pathways to enhance tumor cell growth and metabolism, is among the primary features of tumor cells. Hypoxia-inducible factors (HIFs) have a substantial impact on a variety of facets of tumor biology, such as epithelial-mesenchymal transition, metabolic reprogramming, angiogenesis, and improved radiation resistance. HIFs induce hypoxia-adaptive responses in tumor cells. Many academics have presented preclinical and clinical research targeting HIFs in tumor therapy, highlighting the potential applicability of targeted HIFs. In recent years, the discovery of numerous pharmacological drugs targeting the regulatory mechanisms of HIFs has garnered substantial attention. Additionally, HIF inhibitors have attained positive results when used in conjunction with traditional oncology radiation and/or chemotherapy, as well as with the very promising addition of tumor immunotherapy. Immune checkpoint inhibitors (CPIs), which are employed in a range of cancer treatments over the past decades, are essential in tumor immunotherapy. Nevertheless, the use of immunotherapy has been severely hampered by tumor resistance and treatment-related toxicity. According to research, HIF inhibitors paired with CPIs may be game changers for multiple malignancies, decreasing malignant cell plasticity and cancer therapy resistance, among other things, and opening up substantial new pathways for immunotherapy drug development. The structure, activation mechanisms, and pharmacological sites of action of the HIF family are briefly reviewed in this work. This review further explores the interactions between HIF inhibitors and other tumor immunotherapy components and covers the potential clinical use of HIF inhibitors in combination with CPIs.

Nanotechnology-mediated photodynamic therapy: Focus on overcoming tumor hypoxia

The oxygen level in the tumor is a critical marker that determines response to different treatments. Cancerous cells can adapt to hypoxia and low pH conditions within the tumor microenvironment (TME) to regulate tumor metabolism, proliferation, and promote tumor metastasis as well as angiogenesis, consequently leading to treatment failure and recurrence. In recent years, widespread attempts have been made to overcome tumor hypoxia through different methods, such as hyperbaric oxygen therapy (HBOT), hyperthermia, O2 carriers, artificial hemoglobin, oxygen generator hydrogels, and peroxide materials. While oxygen is found to be an essential agent to improve the treatment response of photodynamic therapy (PDT) and other cancer treatment modalities, the development of hypoxia within the tumor is highly associated with PDT failure. Recently, the use of nanoparticles has been a hot topic for researchers and exploited to overcome hypoxia through Oxygen-generating hydrogels, O2 nanocarriers, and O2 -generating nanoparticles. This review aimed to discuss the role of nanotechnology in tumor oxygenation and highlight the challenges, prospective, and recent advances in this area to improve PDT outcomes. This article is categorized under: Nanotechnology Approaches to Biology > Cells at the Nanoscale Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Cellular signaling in the hypoxic cancer microenvironment: Implications for drug resistance and therapeutic targeting

The rewiring of cellular metabolism is a defining characteristic of cancer, as tumor cells adapt to acquire essential nutrients from a nutrient-poor environment to sustain their viability and biomass. While hypoxia has been identified as a major factor depriving cancer cells of nutrients, recent studies have revealed that cancer cells distant from supporting blood vessels also face nutrient limitations. To overcome this challenge, hypoxic cancer cells, which heavily rely on glucose as an energy source, employ alternative pathways such as glycogen metabolism and reductive carboxylation of glutamine to meet their energy requirements for survival. Our preliminary studies, alongside others in the field, have shown that under glucose-deficient conditions, hypoxic cells can utilize mannose and maltose as alternative energy sources. This review aims to comprehensively examine the hypoxic cancer microenvironment, its association with drug resistance, and potential therapeutic strategies for targeting this unique niche. Furthermore, we will critically evaluate the current literature on hypoxic cancer microenvironments and explore state-of-the-art techniques used to analyze alternate carbohydrates, specifically mannose and maltose, in complex biological fluids. We will also propose the most effective analytical methods for quantifying mannose and maltose in such biological samples. By gaining a deeper understanding of the hypoxic cancer cell microenvironment and its role in drug resistance, novel therapeutic approaches can be developed to exploit this knowledge.

USP11 promotes glycolysis by regulating HIF-1α stability in hepatocellular carcinoma

Understanding the mechanisms underlying metastasis in hepatocellular carcinoma (HCC) is crucial for developing new therapies against this fatal disease. Deubiquitinase ubiquitin-specific protease 11 (USP11) belongs to the deubiquitinating family and has previously been reported to play a critical role in cancer pathogenesis. Although it has been established that USP11 can facilitate the metastasis and proliferation ability of HCC, the underlying regulatory mechanisms are poorly understood. The primary objective of this research was to reveal hitherto undocumented functions of USP11 during HCC progression, especially those related to metabolism. Under hypoxic conditions, USP11 was found to significantly impact the glycolysis of HCC cells, as demonstrated through various techniques, including RNA-Seq, migration and colony formation assays, EdU and co-immunoprecipitation. Interestingly, we found that USP11 interacted with the HIF-1α complex and maintained HIF-1α protein stability by removing ubiquitin. Moreover, USP11/HIF-1α could promote glycolysis through the PDK1 and LDHA pathways. In general, our results demonstrate that USP11 promotes HCC proliferation and metastasis through HIF-1α/LDHA-induced glycolysis, providing new insights and the experimental basis for developing new treatments for this patient population.

ADAMTS12 promotes oxaliplatin chemoresistance and angiogenesis in gastric cancer through VEGF upregulation

BACKGROUND

While ADAMTS12 (A disintegrin and metalloproteinase with thrombospondin motifs 12) has been established as an important regulator of gastrointestinal tumor development and angiogenic activity, the precise mechanistic functions of ADAMTS12 have yet to be fully clarified in gastric cancer (GC). Accordingly, this study was developed to explore the molecular functions of ADAMTS12 in GC and to examine its utility as a biomarker associated with chemoresistance and prognostic outcomes in this cancer type.

METHODS

The ability of ADAMTS12 to modulate the proliferative, migratory, invasive, chemoresistant, and tube formation activity of tumor cells was assessed in vivo and in vitro through gain- and loss-of-function approaches. Correlations between ADAMTS12, CD31, and VEGF expression levels in GC patient tumor tissue samples from individuals that did and did not undergo neoadjuvant chemotherapy (NAC) treatment were analyzed via immunohistochemical staining.

RESULTS

These analyses revealed the ability of ADAMTS12 to promote in vivo and in vitro cellular proliferative and angiogenic activity, promoting the activation of ERK and the consequent upregulation of VEGF, thereby inducing angiogenesis and decreasing GC cell oxaliplatin sensitivity. A positive correlation between ADAMTS12 levels and both the expression of VEGF as well as the density of microvessels was observed in GC patient tumor tissues. Moreover, those GC patients exhibiting higher intratumoral ADAMTS12 expression exhibited worse responses to NAC treatment and worse overall survival outcomes.

CONCLUSIONS

These findings suggest that ADAMTS12 can modulate signaling via the MAPK/VEGF axis in GC cells to enhance tumor cell resistance to oxaliplatin treatment under hypoxic and normoxic conditions. Elevated ADAMTS12 levels can additionally predict vascular abnormalities, worse survival outcomes, and chemoresistance in patients with GC.

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.

Technical report: liquid overlay technique allows the generation of homogeneous osteosarcoma, glioblastoma, lung and prostate adenocarcinoma spheroids that can be used for drug cytotoxicity measurements

Introduction: The mechanisms involved in cancer initiation, progression, drug resistance, and disease recurrence are traditionally investigated through in vitro adherent monolayer (2D) cell models. However, solid malignant tumor growth is characterized by progression in three dimensions (3D), and an increasing amount of evidence suggests that 3D culture models, such as spheroids, are suitable for mimicking cancer development. The aim of this report was to reaffirm the relevance of simpler 3D culture methods to produce highly reproducible spheroids, especially in the context of drug cytotoxicity measurements. Methods: Human A549 lung adenocarcinoma, LnCaP prostate adenocarcinoma, MNNG/HOS osteosarcoma and U251 glioblastoma cell lines were grown into spheroids for 20 days using either Liquid Overlay Technique (LOT) or Hanging Drop (HD) in various culture plates. Their morphology was examined by microscopy. Sensitivity to doxorubicin was compared between MNNG/HOS cells grown in 2D and 3D. Results: For all cell lines studied, the morphology of spheroids generated in round-bottom multiwell plates was more repeatable than that of those generated in flat-bottom multiwell plates. HD had no significant advantage over LOT when the spheroids were cultured in round-bottom plates. Finally, the IC50 of doxorubicin on MNNG/HOS cultured in 3D was 18.8 times higher than in 2D cultures (3D IC50 = 15.07 ± 0.3 µM; 2D IC50 = 0.8 ± 0.4 µM; *p < 0.05). Discussion: In conclusion, we propose that the LOT method, despite and because of its simplicity, is a relevant 3D model for drug response measurements that could be scaled up for high throughput screening.

microRNA-382 as a tumor suppressor? Roles in tumorigenesis and clinical significance

MicroRNAs (miRNAs) are small single-stranded RNAs belonging to a class of non-coding RNAs with an average length of 18-22 nucleotides. Although not able to encode any protein, miRNAs are vastly studied and found to play role in various human physiologic as well as pathological conditions. A huge number of miRNAs have been identified in human cells whose expression is straightly regulated with crucial biological functions, while this number is constantly increasing. miRNAs are particularly studied in cancers, where they either can act with oncogenic function (oncomiRs) or tumor-suppressors role (referred as tumor-suppressor/oncorepressor miRNAs). miR-382 is a well-studied miRNA, which is revealed to play regulatory roles in physiological processes like osteogenic differentiation, hematopoietic stem cell differentiation and normal hematopoiesis, and liver progenitor cell differentiation. Notably, miR-382 deregulation is reported in pathologic conditions, such as renal fibrosis, muscular dystrophies, Rett syndrome, epidural fibrosis, atrial fibrillation, amelogenesis imperfecta, oxidative stress, human immunodeficiency virus (HIV) replication, and various types of cancers. The majority of oncogenesis studies have claimed miR-382 downregulation in cancers and suppressor impact on malignant phenotype of cancer cells in vitro and in vivo, while a few studies suggest opposite findings. Given the putative role of this miRNA in regulation of oncogenesis, assessment of miR-382 expression is suggested in a several clinical investigations as a prognostic/diagnostic biomarker for cancer patients. In this review, we have an overview to recent studies evaluated the role of miR-382 in oncogenesis as well as its clinical potential.

Toward a Unifying Hypothesis for Redesigned Lipid Catabolism as a Clinical Target in Advanced, Treatment-Resistant Carcinomas

We review extensive progress from the cancer metabolism community in understanding the specific properties of lipid metabolism as it is redesigned in advanced carcinomas. This redesigned lipid metabolism allows affected carcinomas to make enhanced catabolic use of lipids in ways that are regulated by oxygen availability and is implicated as a primary source of resistance to diverse treatment approaches. This oxygen control permits lipid catabolism to be an effective energy/reducing potential source under the relatively hypoxic conditions of the carcinoma microenvironment and to do so without intolerable redox side effects. The resulting robust access to energy and reduced potential apparently allow carcinoma cells to better survive and recover from therapeutic trauma. We surveyed the essential features of this advanced carcinoma-specific lipid catabolism in the context of treatment resistance and explored a provisional unifying hypothesis. This hypothesis is robustly supported by substantial preclinical and clinical evidence. This approach identifies plausible routes to the clinical targeting of many or most sources of carcinoma treatment resistance, including the application of existing FDA-approved agents.

Physical Dissolution Combined with Photodynamic Depletion: A Two-Pronged Nanoapproach for Deoxygenation-Driven and Hypoxia-Activated Prodrug Therapy

Hypoxia may enhance the chemoresistance of cancer cells and can significantly compromise the effectiveness of chemotherapy. Many efforts have been made to relieve or reverse hypoxia by introducing more oxygen into the tumor microenvironment (TME). Acting in a diametrically opposite way, in the current study, a novel nanocarrier was designed to further exhaust the oxygen level of the hypoxic TME. By creating such an oxygen depleted TME, the hypoxia-selective cytotoxin can work effectively, and oxygen exhaustion triggered chemotherapy can be achieved. Herein, deoxygenation agent, FDA-approved perfluorocarbon (PFC) and photosensitizer indocyanine green (ICG) for oxygen depletion, along with the hypoxia-activating drug tirapazamine (TPZ), were coincorporated within the poly(lactic-co-glycolic acid) (PLGA) nanoemulsion (ICG/TPZ@PPs) for the treatment of hypoxic tumors. Following hypoxia amplifying through physical oxygen dissolution and photodynamic depletion in tumors, hypoxic chemotherapy could be effectively activated to improve multitreatment synergy. After achieving local tumor enrichment, PFC-mediated oxygen dissolution combined with further ICG-mediated photodynamic therapy (PDT) under near-infrared (NIR) laser irradiation could induce enhanced hypoxia, which would activate the antitumor activity of codelivered TPZ to synergize cytotoxicity. Remarkably, in vivo experimental results exhibited that deoxygenated ICG/TPZ@PPs-based photothermal therapy (PTT), PDT, and hypoxia activated chemotherapy have an excellent synergistic ablation of tumors without obvious side effects, and therefore, a broad prospect of application of this nanocarrier could be expected.

Bio-Responsive Macromolecular Drug and Small-Molecular Drug Conjugates: Nanoparticulate Prodrugs for Tumor Microenvironment Heterogeneity Management and Therapeutic Response Enhancement

How to break through the poor response of current drug therapy, which often resulted from tumor microenvironment heterogeneity (TMH), remains an enormous challenge in the treatment of critical diseases. In this work, a practical solution on bio-responsive dual-drug conjugates for overcoming TMH and improving antitumor treatment, which integrates the advantages of macromolecular drugs and small-molecular drugs, is proposed. Nanoparticulate prodrugs based on small-molecular drug and macromolecular drug conjugates are designed as a robust weapon for programmable multidrug delivery at tumor-specific sites: the tumor microenvironment acid condition triggers delivery of macromolecular aptamer drugs (AX102) to manage TMH (including tumor stroma matrix, interstitial fluid pressure, vasculature network, blood perfusion, and oxygen distribution), and intracellular lysosomal acid condition activates rapid release of small-molecular drugs (doxorubicin and dactolisib) to enhance curative effects. As compared with doxorubicin chemotherapy, the tumor growth inhibition rate is enhanced by 47.94% after multiple tumor heterogeneity management. This work verifies that the nanoparticulate prodrugs facilitate TMH management and therapeutic response enhancements, as well as elucidates synergetic mechanisms for drug resistance reversal and metastasis inhibition. It is hoped that the nanoparticulate prodrugs will be an excellent demonstration of the co-delivery of small-molecular drugs and macromolecular drugs.

DPPA3-HIF1α axis controls colorectal cancer chemoresistance by imposing a slow cell-cycle phenotype

Tumor relapse is linked to rapid chemoresistance and represents a bottleneck for cancer therapy success. Engagement of a reduced proliferation state is a non-mutational mechanism exploited by cancer cells to bypass therapy-induced cell death. Through combining functional pulse-chase experiments in engineered cells and transcriptomic analyses, we identify DPPA3 as a master regulator of slow-cycling and chemoresistant phenotype in colorectal cancer (CRC). We find a vicious DPPA3-HIF1α feedback loop that downregulates FOXM1 expression via DNA methylation, thereby delaying cell-cycle progression. Moreover, downregulation of HIF1α partially restores a chemosensitive proliferative phenotype in DPPA3-overexpressing cancer cells. In cohorts of CRC patient samples, DPPA3 overexpression acts as a predictive biomarker of chemotherapeutic resistance that subsequently requires reduction in its expression to allow metastatic outgrowth. Our work demonstrates that slow-cycling cancer cells exploit a DPPA3/HIF1α axis to support tumor persistence under therapeutic stress and provides insights on the molecular regulation of disease progression.

Nanomedicine Strategies for Targeting Tumor Stroma

The tumor stroma, or the microenvironment surrounding solid tumors, can significantly impact the effectiveness of cancer therapies. The tumor microenvironment is characterized by high interstitial pressure, a consequence of leaky vasculature, and dense stroma created by excessive deposition of various macromolecules such as collagen, fibronectin, and hyaluronic acid (HA). In addition, non-cancerous cells such as cancer-associated fibroblasts (CAFs) and the extracellular matrix (ECM) itself can promote tumor growth. In recent years, there has been increased interest in combining standard cancer treatments with stromal-targeting strategies or stromal modulators to improve therapeutic outcomes. Furthermore, the use of nanomedicine, which can improve the delivery and retention of drugs in the tumor, has been proposed to target the stroma. This review focuses on how different stromal components contribute to tumor progression and impede chemotherapeutic delivery. Additionally, this review highlights recent advancements in nanomedicine-based stromal modulation and discusses potential future directions for developing more effective stroma-targeted cancer therapies.

The prognostic role of HIF-1α and NF-κB expression in RAS wild-type metastatic colorectal cancer: A Turkish Oncology Group (TOG) study

BACKGROUND

Not all RAS wild-type metastatic colorectal cancer (mCRC) patients experience the same benefit from anti-epidermal growth factor receptor (EGFR) treatments. Studies have shown that nuclear factor-κB (NF-κB), hypoxia-inducible factor-1α (HIF-1α), interleukin 8 (IL-8) and transforming growth factor β (TGF-β) may be therapeutic targets for mCRC. The aim of this study was to clarify the prognostic value of NF-κB, HIF-1α, IL-8, and TGF-β expression in patients with left-sided mCRC receiving EGFR inhibitors.

METHODS

Patients with RAS wild-type, left-sided mCRC treated with anti-EGFR on the first line between September 2013 and April 2022 were included. Immunohistochemical staining for NF-κB, HIF-1α, IL-8 and TGF-β was performed from tumor tissues of 88 patients. Patients were divided into NF-κB, HIF-1α, IL-8 and TGF-β expression positive and negative group, moreover, expression positive group were also divided into two group as expression intensity low and high group. The median follow-up was 25.2 months.

RESULTS

Median progression-free survival (PFS) was 8.1 (6-10.2) months in the cetuximab group, 11.3 (8.5-14) months in the panitumumab group (p = 0.09). Median overall survival (OS) was 23.9 (4.3-43.4) months in the cetuximab group, 26.9 (15.9-31.9) months in the panitumumab group (p = 0.8). Cytoplasmic NF-κB expression was present in all patients. The mOS was 19.8 (11-28.6) months in NF-κB expression intensity low group and 36.5 (20.1-52.8) months in high group (p = 0.03). The mOS of the HIF-1α expression negative group was significantly longer compared with expression positive group (p = 0.014). There was no significant difference in IL-8 and TGF-β expression status on mOS and mPFS (for all, p > 0.05). Positive expression of HIF-1α was poor prognostic for mOS in the univariate analysis (HR:2.7, 95% CI 1.18-6.52, p = 0.02) and in multivariate analysis (HR 3.69, 95% CI 1.41-9.6, p = 0.008). High cytoplasmic expression intensity of NF-κB was found to have a good prognostic value for mOS (HR 0.47, 95% CI 0.26-0.85, p = 0.01).

CONCLUSION

High cytoplasmic expression intensity of NF-κB and negative expression of HIF-1α could be a good prognostic marker for mOS in RAS wild-type left-sided mCRC.

Genome editing and cancer therapy: handling the hypoxia-responsive pathway as a promising strategy

The precise characterization of oxygen-sensing pathways and the identification of pO2-regulated gene expression are both issues of critical importance. The O2-sensing system plays crucial roles in almost all the pivotal human processes, including the stem cell specification, the growth and development of tissues (such as embryogenesis), the modulation of intermediate metabolism (including the shift of the glucose metabolism from oxidative to anaerobic ATP production and vice versa), and the control of blood pressure. The solid cancer microenvironment is characterized by low oxygen levels and by the consequent activation of the hypoxia response that, in turn, allows a complex adaptive response characterized mainly by neoangiogenesis and metabolic reprogramming. Recently, incredible advances in molecular genetic methodologies allowed the genome editing with high efficiency and, above all, the precise identification of target cells/tissues. These new possibilities and the knowledge of the mechanisms of adaptation to hypoxia suggest the effective development of new therapeutic approaches based on the manipulation, targeting, and exploitation of the oxygen-sensor system molecular mechanisms.

Anti-proliferative activity of nitroquinolone fused acylhydrazones as non-small cell human lung cancer agents

A new series of 8-nitroquinolone-based aromatic heterocyclic acyl hydrazones have been synthesised and characterised through various spectroscopic techniques. They were theoretically examined for molecular docking with various proteins related to the apoptosis of the non-small cell lung cancer cell line A549. The results indicate that the possible modes of interaction of all the synthesised compounds are compatible for use as anti-proliferative drugs. Also, the drug-likeness of the compounds was examined through theoretical ADMET analysis, which indicated good gastrointestinal absorption as well as low toxicity. Selected compounds were evaluated for their in vitro anti-cancer activity using A549, MCF-7 and HeLa cell lines through an MTT assay to determine cytotoxicity. Compounds 3c, 3a and 11c exhibited significant cytotoxicity towards A549 cells in the order of 3c (15.3 ± 0.7) > 3a (15.8 ± 0.1) > 11c (17.1 ± 0.2), whereas all the compounds show insignificant toxicity on normal human embryonic kidney cells up to a concentration of 200 μM. The best compounds among the series (3c and 11c) were chosen for further detection of apoptosis through fluorescence microscopic techniques using AO/EtBr and DAPI. The reduced DNA synthesis during the cell cycle was also investigated through flow cytometric techniques. The results indicate that the compounds possess significant anticancer properties due to the activation of the mitochondrial mediated intrinsic pathway.

Macrophage induces anti-cancer drug resistance in canine mammary gland tumor spheroid

Tumor-associated macrophages (TAMs) play an important role in the tumor microenvironment by producing cytokines and growth factors. Furthermore, TAMs play multifunctional roles in tumor progression, immune regulation, metastasis, angiogenesis, and chemoresistance. Hypoxia in the tumor microenvironment induces tumor-supporting transformation of TAMs, which enhances tumor malignancy through developing anti-cancer resistance, for example. In this study, a hybrid spheroid model of canine mammary gland tumor (MGT) cell lines (CIPp and CIPm) and canine macrophages (DH82) was established. The effects of hypoxia induced by the spheroid culture system on the anti-cancer drug resistance of canine MGT cells were investigated. A hybrid spheroid was created using an ultralow-adhesion plate. The interactions between canine MGT cells and DH82 were investigated using a co-culture method. When co-cultured with DH82, cell viability and expression levels of tumor growth factors and multi-drug resistance genes were increased in canine MGT cells under doxorubicin. Additionally, doxorubicin-induced apoptosis and G2/M cell cycle arrest were attenuated in canine MGT cells co-cultured with DH82. In conclusion, the hybrid spheroid model established in this study reflects the hypoxic TME, allowing DH82 to induce anti-cancer drug resistance in canine MGT cells.

The Corey-Seebach Reagent in the 21st Century: A Review

The Corey-Seebach reagent plays an important role in organic synthesis because of its broad synthetic applications. The Corey-Seebach reagent is formed by the reaction of an aldehyde or a ketone with 1,3-propane-dithiol under acidic conditions, followed by deprotonation with n-butyllithium. A large variety of natural products (alkaloids, terpenoids, and polyketides) can be accessed successfully by utilizing this reagent. This review article focuses on the recent contributions (post-2006) of the Corey-Seebach reagent towards the total synthesis of natural products such as alkaloids (lycoplanine A, diterpenoid alkaloids, etc.), terpenoids (bisnorditerpene, totarol, etc.), polyketide (ambruticin J, biakamides, etc.), and heterocycles such as rodocaine and substituted pyridines, as well and their applications towards important organic synthesis.

Integrated analysis revealed hypoxia signatures and LDHA related to tumor cell dedifferentiation and unfavorable prognosis in pancreatic adenocarcinoma: Hypoxia in PDAC

Pancreatic ductal adenocarcinoma (PDAC) is a highly heterogeneous cancer with limited understanding of its classification and tumor microenvironment. Here, by analyzing single-nucleus RNA sequencing of 43, 817 tumor cells from 15 PDAC tumors and non-tumor, we find that hypoxia signatures were heterogeneous across samples and were potential regulators for tumor progression and more aggressive phenotype. Hypoxia-high PDAC tends to present a basal/squamous-like phenotype and has significantly increased outgoing signaling, which enhances tumor cell stemness and promotes metastasis, angiogenesis, and fibroblast differentiation in PDAC. Hypoxia is related to an extracellular matrix enriched microenvironment, and increased possibility of TP53 mutation in PDAC. TP63 is a specific marker of squamous-like phenotype, and presents elevated transcriptome levels in most hypoxia PDAC tumors. In summary, our research highlights the potential linkage of hypoxia, tumor progression and genome alteration in PDAC, leading to further understand of the formation of inter-tumoral and intra-tumoral heterogenous in PDAC. Our study extends the understanding of the diversity and transition of tumor cells in PDAC, which provides insight into future PDAC management.

Angiogenic signaling pathways and anti-angiogenic therapy for cancer

Angiogenesis, the formation of new blood vessels, is a complex and dynamic process regulated by various pro- and anti-angiogenic molecules, which plays a crucial role in tumor growth, invasion, and metastasis. With the advances in molecular and cellular biology, various biomolecules such as growth factors, chemokines, and adhesion factors involved in tumor angiogenesis has gradually been elucidated. Targeted therapeutic research based on these molecules has driven anti-angiogenic treatment to become a promising strategy in anti-tumor therapy. The most widely used anti-angiogenic agents include monoclonal antibodies and tyrosine kinase inhibitors (TKIs) targeting vascular endothelial growth factor (VEGF) pathway. However, the clinical benefit of this modality has still been limited due to several defects such as adverse events, acquired drug resistance, tumor recurrence, and lack of validated biomarkers, which impel further research on mechanisms of tumor angiogenesis, the development of multiple drugs and the combination therapy to figure out how to improve the therapeutic efficacy. Here, we broadly summarize various signaling pathways in tumor angiogenesis and discuss the development and current challenges of anti-angiogenic therapy. We also propose several new promising approaches to improve anti-angiogenic efficacy and provide a perspective for the development and research of anti-angiogenic therapy.

Mammalian orthoreovirus infection in human epidermal growth factor receptor 2 positive (HER2+) breast cancer cells

Mammalian orthoreovirus (MRV) is a clinically benign oncolytic virus which has been investigated for use in multiple cancer types, including breast cancer (BC). In human clinical trials, MRV has been shown to be safe, and multiple BC patients have shown partial responses to intratumoral and intravenous virus delivery. Combination therapies inclusive of MRV and current FDA approved BC chemotherapies are being investigated to target metastatic, early BC, and triple negative BC. Though MRV is being tested clinically, we still do not fully understand the highly variable patient responses to MRV therapy. One of the most aggressive BC subtypes is HER2+ BC, in which human epidermal growth factor receptor 2 (HER2) is dysregulated, resulting in increased growth, survival, and metastasis of cancer cells. FDA approved therapies, trastuzumab and pertuzumab, target HER2 to prevent signaling of the phosphoinositide 3-kinase (PI3K) pathway. However, recent findings show that accumulation of hypoxia inducible factor-1 alpha (HIF-1α) in HER2+ BC cells contributes to trastuzumab resistance. In this work, we provide evidence that MRV infects, replicates in, and kills HER2 overexpressing cells. MRV infection is also found to have variable effects on signaling pathways that activate or are activated by HER2 expression. Finally, we show that MRV reduces HIF-1α accumulation in all the cell lines tested, including a HER2+ BC cell line. These studies provide further evidence that MRV holds promise for use in conjunction with trastuzumab to treat HER2+ BC patients.

Bacterial Lysate from the Multi-Strain Probiotic SLAB51 Triggers Adaptative Responses to Hypoxia in Human Caco-2 Intestinal Epithelial Cells under Normoxic Conditions and Attenuates LPS-Induced Inflammatory Response

Hypoxia-inducible factor-1α (HIF-1α), a central player in maintaining gut-microbiota homeostasis, plays a pivotal role in inducing adaptive mechanisms to hypoxia and is negatively regulated by prolyl hydroxylase 2 (PHD2). HIF-1α is stabilized through PI3K/AKT signaling regardless of oxygen levels. Considering the crucial role of the HIF pathway in intestinal mucosal physiology and its relationships with gut microbiota, this study aimed to evaluate the ability of the lysate from the multi-strain probiotic formulation SLAB51 to affect the HIF pathway in a model of in vitro human intestinal epithelium (intestinal epithelial cells, IECs) and to protect from lipopolysaccharide (LPS) challenge. The exposure of IECs to SLAB51 lysate under normoxic conditions led to a dose-dependent increase in HIF-1α protein levels, which was associated with higher glycolytic metabolism and L-lactate production. Probiotic lysate significantly reduced PHD2 levels and HIF-1α hydroxylation, thus leading to HIF-1α stabilization. The ability of SLAB51 lysate to increase HIF-1α levels was also associated with the activation of the PI3K/AKT pathway and with the inhibition of NF-κB, nitric oxide synthase 2 (NOS2), and IL-1β increase elicited by LPS treatment. Our results suggest that the probiotic treatment, by stabilizing HIF-1α, can protect from an LPS-induced inflammatory response through a mechanism involving PI3K/AKT signaling.

The Promise of Nanoparticles-Based Radiotherapy in Cancer Treatment

Radiation has been utilized for a long time for the treatment of cancer patients. However, radiotherapy (RT) has many constraints, among which non-selectivity is the primary one. The implementation of nanoparticles (NPs) with RT not only localizes radiation in targeted tissue but also provides significant tumoricidal effect(s) compared to radiation alone. NPs can be functionalized with both biomolecules and therapeutic agents, and their combination significantly reduces the side effects of RT. NP-based RT destroys cancer cells through multiple mechanisms, including ROS generation, which in turn damages DNA and other cellular organelles, inhibiting of the DNA double-strand damage-repair system, obstructing of the cell cycle, regulating of the tumor microenvironment, and killing of cancer stem cells. Furthermore, such combined treatments overcome radioresistance and drug resistance to chemotherapy. Additionally, NP-based RT in combined treatments have shown synergistic therapeutic benefit(s) and enhanced the therapeutic window. Furthermore, a combination of phototherapy, i.e., photodynamic therapy and photothermal therapy with NP-based RT, not only reduces phototoxicity but also offers excellent therapeutic benefits. Moreover, using NPs with RT has shown promise in cancer treatment and shown excellent therapeutic outcomes in clinical trials. Therefore, extensive research in this field will pave the way toward improved RT in cancer treatment.

Oxygen Self-Generating Nanoreactor Mediated Ferroptosis Activation and Immunotherapy in Triple-Negative Breast Cancer

The hypoxia microenvironment of solid tumors poses a technological bottleneck for ferroptosis and immunotherapy in clinical oncology. Nanoreactors based on special physiological signals in tumor cells are able to avoid various tumor tolerance mechanisms by alleviating the intracellular hypoxia environment. Herein we reported a nanoreactor Cu_2-xSe that enabled the conversion of Cu elements between Cu⁺ and Cu²⁺ for the generation of O₂ and the consumption of intracellular GSH content. Furthermore, to enhance the catalytic and ferroptosis-inducing activities of the nanoreactors, the ferroptosis agonist Erastin was loaded on the ZIF-8 coating on the surface of Cu_2-xSe to up-regulate the expression of NOX4 protein, increase the intracellular H₂O₂ content, catalyze the Cu⁺ to produce O₂ and activate ferroptosis. In addition, the nanoreactors were simultaneously surface functionalized with PEG polymer and folic acid molecules, which ensured the in vivo blood circulation and tumor-specific uptake. In vitro and in vivo experiments demonstrated that the functionalized self-supplying nanoreactors can amplify the ability to generate O₂ and consume intracellular GSH via the interconversion of Cu elements Cu⁺ and Cu²⁺, and impair the GPX4/GSH pathway and HIF-1α protein expression. At the same time, by alleviating the intracellular hypoxia environment, the expression of miR301, a gene in the secreted exosomes was decreased, which ultimately affected the phenotype polarization of TAMs and increased the content of IFN γ secreted by CD8⁺ T cells, which further promoted the ferroptosis induced by Erastin-loaded nanoreactors. This combined therapeutic strategy of activating the tumor immune response and ferroptosis via self-supplying nanoreactors provides a potential strategy for clinical application.

Nanocarriers overcoming biological barriers induced by multidrug resistance of chemotherapeutics in 2D and 3D cancer models

Multidrug resistance (MDR) is currently a big challenge in cancer therapy and limits its success in several patients. Tumors use the MDR mechanisms to colonize the host and reduce the efficacy of chemotherapeutics that are injected as single agents or combinations. MDR mechanisms are responsible for inactivation of drugs and formbiological barriers in cancer like the drug efflux pumps, aberrant extracellular matrix, hypoxic areas, altered cell death mechanisms, etc. Nanocarriers have some potential to overcome these barriers and improve the efficacy of chemotherapeutics. In fact, they are versatile and can deliver natural and synthetic biomolecules, as well as RNAi/DNAi, thus providing a controlled release of drugs and a synergistic effect in tumor tissues. Biocompatible and safe multifunctional biopolymers, with or without specific targeting molecules, modify the surface and interface properties of nanocarriers. These modifications affect the interaction of nanocarriers with cellular models as well as the selection of suitable models for in vitro experiments. MDR cancer cells, and particularly their 2D and 3D models, in combination with anatomical and physiological structures of tumor tissues, can boost the design and preparation of nanomedicines for anticancer therapy. 2D and 3D cancer cell cultures are suitable models to study the interaction, internalization, and efficacy of nanocarriers, the mechanisms of MDR in cancer cells and tissues, and they are used to tailor a personalized medicine and improve the efficacy of anticancer treatment in patients. The description of molecular mechanisms and physio-pathological pathways of these models further allow the design of nanomedicine that can efficiently overcome biological barriers involved in MDR and test the activity of nanocarriers in 2D and 3D models of MDR cancer cells.

Acquired non-thermal plasma resistance mediates a shift towards aerobic glycolysis and ferroptotic cell death in melanoma

AIMS

To gain insights into the underlying mechanisms of NTP therapy sensitivity and resistance, using the first-ever NTP-resistant cell line derived from sensitive melanoma cells (A375).

METHODS

Melanoma cells were exposed to NTP and re-cultured for 12 consecutive weeks before evaluation against the parental control cells. Whole transcriptome sequencing analysis was performed to identify differentially expressed genes and enriched molecular pathways. Glucose uptake, extracellular lactate, media acidification, and mitochondrial respiration was analyzed to determine metabolic changes. Cell death inhibitors were used to assess the NTP-induced cell death mechanisms, and apoptosis and ferroptosis was further validated via Annexin V, Caspase 3/7, and lipid peroxidation analysis.

RESULTS

Cells continuously exposed to NTP became 10 times more resistant to NTP compared to the parental cell line of the same passage, based on their half-maximal inhibitory concentration (IC50). Sequencing and metabolic analysis indicated that NTP-resistant cells had a preference towards aerobic glycolysis, while cell death analysis revealed that NTP-resistant cells exhibited less apoptosis but were more vulnerable to lipid peroxidation and ferroptosis.

CONCLUSIONS

A preference towards aerobic glycolysis and ferroptotic cell death are key physiological changes in NTP-resistance cells, which opens new avenues for further, in-depth research into other cancer types.

Hypoxia-ameliorated photothermal manganese dioxide nanoplatform for reversing doxorubicin resistance

Drug resistance is a huge hurdle in tumor therapy. Tumor hypoxia contributes to chemotherapy resistance by inducing the hypoxia-inducible factor-1α (HIF-1α) pathway. To reduce tumor hypoxia, novel approaches have been devised, providing significant importance to reverse therapeutic resistance and improve the effectiveness of antitumor therapies. Herein, the nanosystem of bovine serum albumin (BSA)-templated manganese dioxide (MnO₂) nanoparticles (BSA/MnO₂ NPs) loaded with doxorubicin (DOX) (DOX-BSA/MnO₂ NPs) developed in our previous report was further explored for their physicochemical properties and capacity to reverse DOX resistance because of their excellent photothermal and tumor microenvironment (TME) response effects. The DOX-BSA/MnO₂ NPs showed good biocompatibility and hemocompatibility. Meanwhile, DOX-BSA/MnO₂ NPs could greatly affect DOX pharmacokinetic properties, with prolonged circulation time and reduced cardiotoxicity, besides enhancing accumulation at tumor sites. DOX-BSA/MnO₂ NPs can interact with H₂O₂ and H⁺ in TME to form oxygen and exhibit excellent photothermal effect to further alleviate hypoxia due to MnO₂, reversing DOX resistance by down-regulating HIF-1α expression and significantly improving the antitumor efficiency in DOX-resistant human breast carcinoma cell line (MCF-7/ADR) tumor model. The hypoxia-ameliorated photothermal MnO₂ platform is a promising strategy for revering DOX resistance.

Engineering the Tumor Immune Microenvironment through Minimally Invasive Interventions

The tumor microenvironment (TME) is a unique landscape that poses several physical, biochemical, and immune barriers to anti-cancer therapies. The rapidly evolving field of immuno-engineering provides new opportunities to dismantle the tumor immune microenvironment by efficient tumor destruction. Systemic delivery of such treatments can often have limited local effects, leading to unwanted offsite effects such as systemic toxicity and tumor resistance. Interventional radiologists use contemporary image-guided techniques to locally deliver these therapies to modulate the immunosuppressive TME, further accelerating tumor death and invoking a better anti-tumor response. These involve local therapies such as intratumoral drug delivery, nanorobots, nanoparticles, and implantable microdevices. Physical therapies such as photodynamic therapy, electroporation, hyperthermia, hypothermia, ultrasound therapy, histotripsy, and radiotherapy are also available for local tumor destruction. While the interventional radiologist can only locally manipulate the TME, there are systemic offsite recruitments of the immune response. This is known as the abscopal effect, which leads to more significant anti-tumoral downstream effects. Local delivery of modern immunoengineering methods such as locoregional CAR-T therapy combined with immune checkpoint inhibitors efficaciously modulates the immunosuppressive TME. This review highlights the various advances and technologies available now to change the TME and revolutionize oncology from a minimally invasive viewpoint.

Cell Dome as an Evaluation Platform for Organized HepG2 Cells

Human-hepatoblastoma-derived cell line, HepG2, has been widely used in liver and liver cancer studies. HepG2 spheroids produced in a three-dimensional (3D) culture system provide a better biological model than cells cultured in a two-dimensional (2D) culture system. Since cells at the center of spheroids exhibit specific behaviors attributed to hypoxic conditions, a 3D cell culture system that allows the observation of such cells using conventional optical or fluorescence microscopes would be useful. In this study, HepG2 cells were cultured in "Cell Dome", a micro-dome in which cells are enclosed in a cavity consisting of a hemispherical hydrogel shell. HepG2 cells formed hemispherical cell aggregates which filled the cavity of Cell Domes on 18 days of culture and the cells could continue to be cultured for 29 days. The cells at the center of hemispherical cell aggregates were observed using a fluorescence microscope. The cells grew in Cell Domes for 18 days exhibited higher Pi-class Glutathione S-Transferase enzymatic activity, hypoxia inducible factor-1α gene expression, and higher tolerance to mitomycin C than those cultured in 2D on tissue culture dishes (* p < 0.05). These results indicate that the center of the glass adhesive surface of hemispherical cell aggregates which is expected to have the similar environment as the center of the spheroids can be directly observed through glass plates. In conclusion, Cell Dome would be useful as an evaluation platform for organized HepG2 cells.

Hypoxia-Inducible Factor-1: A Novel Therapeutic Target for the Management of Cancer, Drug Resistance, and Cancer-Related Pain

Hypoxia-inducible factor-1 (HIF-1) is a key transcription factor that regulates the transcription of many genes that are responsible for the adaptation and survival of tumor cells in hypoxic environments. Over the past few decades, tremendous efforts have been made to comprehensively understand the role of HIF-1 in tumor progression. Based on the pivotal roles of HIF-1 in tumor biology, many HIF-1 inhibitors interrupting expression, stabilization, DNA binding properties, or transcriptional activity have been identified as potential therapeutic agents for various cancers, yet none of these inhibitors have yet been successfully translated into clinically available cancer treatments. In this review, we briefly introduce the regulation of the HIF-1 pathway and summarize its roles in tumor cell proliferation, angiogenesis, and metastasis. In addition, we explore the implications of HIF-1 in the development of drug resistance and cancer-related pain: the most commonly encountered obstacles during conventional anticancer therapies. Finally, the current status of HIF-1 inhibitors in clinical trials and their perspectives are highlighted, along with their modes of action. This review provides new insights into novel anticancer drug development targeting HIF-1. HIF-1 inhibitors may be promising combinational therapeutic interventions to improve the efficacy of current cancer treatments and reduce drug resistance and cancer-related pain.

Proton-coupled monocarboxylate transporters in cancer: From metabolic crosstalk, immunosuppression and anti-apoptosis to clinical applications

The Warburg effect is known as the hyperactive glycolysis that provides the energy needed for rapid growth and proliferation in most tumor cells even under the condition of sufficient oxygen. This metabolic pattern can lead to a large accumulation of lactic acid and intracellular acidification, which can affect the growth of tumor cells and lead to cell death. Proton-coupled monocarboxylate transporters (MCTs) belong to the SLC16A gene family, which consists of 14 members. MCT1-4 promotes the passive transport of monocarboxylate (e.g., lactate, pyruvate, and ketone bodies) and proton transport across membranes. MCT1-4-mediated lactate shuttling between glycolytic tumor cells or cancer-associated fibroblasts and oxidative tumor cells plays an important role in the metabolic reprogramming of energy, lipids, and amino acids and maintains the survival of tumor cells. In addition, MCT-mediated lactate signaling can promote tumor angiogenesis, immune suppression and multidrug resistance, migration and metastasis, and ferroptosis resistance and autophagy, which is conducive to the development of tumor cells and avoid death. Although there are certain challenges, the study of targeted drugs against these transporters shows great promise and may form new anticancer treatment options.

Three-Dimensional Microtumor Formation of Infantile Hemangioma-Derived Endothelial Cells for Mechanistic Exploration and Drug Screening

Infantile hemangioma (IH) is the most prevalent type of vascular tumor in infants. The pathophysiology of IH is unknown. The tissue structure and physiology of two-dimensional cell cultures differ greatly from those in vivo, and spontaneous regression often occurs during tumor formation in nude mice and has severely limited research into the pathogenesis and development of IH. By decellularizing porcine aorta, we attempted to obtain vascular-specific extracellular matrix as the bioink for fabricating micropattern arrays of varying diameters via microcontact printing. We then constructed IH-derived CD31+ hemangioma endothelial cell three-dimensional microtumor models. The vascular-specific and decellularized extracellular matrix was suitable for the growth of infantile hemangioma-derived endothelial cells. The KEGG signaling pathway analysis revealed enrichment primarily in stem cell pluripotency, RAS, and PI3KAkt compared to the two-dimensional cell model according to RNA sequencing. Propranolol, the first-line medication for IH, was also used to test the model's applicability. We also found that metformin had some impact on the condition. The three-dimensional microtumor models of CD31+ hemangioma endothelial cells were more robust and efficient experimental models for IH mechanistic exploration and drug screening.

Hypoxia induces chemoresistance to proteasome inhibitors through orchestrating deSUMOylation and ubiquitination of SRC-3 in multiple myeloma

The bone marrow microenvironment in multiple myeloma (MM) is hypoxic and provides multi-advantages for the initiation of chemoresistance, but the underlying mechanisms and key regulators are still indistinct. In the current study, we found that hypoxia stimulus easily induced chemoresistance to proteasome inhibitors (PIs), and the steroid receptor coactivator 3 (SRC-3) expression was remarkably augmented at posttranslational level. Protein interactome analysis identified SENP1 as a key modifier of SRC-3 stability, as SENP1-mediated deSUMOylation attenuated the K11-linked polyubiquitination of SRC-3. SENP1 depletion in the SENP1^fl/flCD19^Cre/+ B cells showed impaired SRC3 stability, and knockdown of SENP1 in MM cells by CRISPR/cas9 sgRNA accelerated the degradation of SRC-3 and remarkably overcame the resistance to PIs. In the Vk*Myc and 5TGM1 mouse models as well as patient-derived xenograft (PDX) of myeloma, SENP1 inhibitor Momordin Ιc (Mc) increased the sensitivity to PIs in MM cells. Importantly, SENP1 level was positively correlated with SRC-3 level in the tissues from refractory/relapsed MM, as well as in xenograft tissues from mice treated with bortezomib and Mc. Taken together, our findings suggest that hypoxia-induced SENP1 is a crucial regulator of chemoresistance to PIs, and shed light on developing therapeutic strategies to overcome chemoresistance by using small molecules targeting SENP1 or SRC-3.

Novel Implications of Nanoparticle-Enhanced Radiotherapy and Brachytherapy: Z-Effect and Tumor Hypoxia

Radiotherapy and internal radioisotope therapy (brachytherapy) induce tumor cell death through different molecular signaling pathways. However, these therapies in cancer patients are constrained by dose-related adverse effects and local discomfort due to the prolonged exposure to the surrounding tissues. Technological advancements in nanotechnology have resulted in synthesis of high atomic elements such as nanomaterials, which can be used as radiosensitizers due to their photoelectric characteristics. The aim of this review is to elucidate the effects of novel nanomaterials in the field of radiation oncology to ameliorate dose-related toxicity through the application of ideal nanoparticle-based radiosensitizers such as Au (gold), Bi (bismuth), and Lu (Lutetium-177) for enhancing cytotoxic effects of radiotherapy via the high-Z effect. In addition, we discuss the role of nanoparticle-enhanced radiotherapy in alleviating tumor hypoxia through the nanodelivery of genes/drugs and other functional anticancer molecules. The implications of engineered nanoparticles in preclinical and clinical studies still need to be studied in order to explore potential mechanisms for radiosensitization by minimizing tumor hypoxia, operational/logistic complications and by overcoming tumor heterogeneity in radiotherapy/brachytherapy.

Salmonella as a Promising Curative Tool against Cancer

Bacteria-mediated cancer therapy has become a topic of interest under the broad umbrella of oncotherapy. Among many bacterial species, Salmonella remains at the forefront due to its ability to localize and proliferate inside tumor microenvironments and often suppress tumor growth. Salmonella Typhimurium is one of the most promising mediators, with engineering plasticity and cancer specificity. It can be used to deliver toxins that induce cell death in cancer cells specifically, and also as a cancer-specific instrument for immunotherapy by delivering tumor antigens and exposing the tumor environment to the host immune system. Salmonella can be used to deliver prodrug converting enzymes unambiguously against cancer. Though positive responses in Salmonella-mediated cancer treatments are still at a preliminary level, they have paved the way for developing combinatorial therapy with conventional chemotherapy, radiotherapy, and surgery, and can be used synergistically to combat multi-drug resistant and higher-stage cancers. With this background, Salmonella-mediated cancer therapy was approved for clinical trials by U.S. Food and Drug Administration, but the results were not satisfactory and more pre-clinical investigation is needed. This review summarizes the recent advancements in Salmonella-mediated oncotherapy in the fight against cancer. The present article emphasizes the demand for Salmonella mutants with high stringency toward cancer and with amenable elements of safety by virulence deletions.

Overview of Nanoparticle-Based Approaches for the Combination of Photodynamic Therapy (PDT) and Chemotherapy at the Preclinical Stage

Simple Summary

The present review represents the outstanding and promising recent literature reports (2017–2022) on nanoparticle-based formulations developed for anticancer therapy with photodynamic therapy (PDT), photosensitizers, and chemotherapeutics. Besides brief descriptions of chemotherapeutics’ classification and of PDT mechanisms and limitations, several examples of nanosystems endowed with different responsiveness (e.g., acidic pH and reactive oxygen species) and peculiarity (e.g., tumor oxygenation capacity, active tumor targeting, and biomimetic features) are described, and for each drug combination, in vitro and in vivo results on preclinical cancer models are reported.

Abstract

The widespread diffusion of photodynamic therapy (PDT) as a clinical treatment for solid tumors is mainly limited by the patient’s adverse reaction (skin photosensivity), insufficient light penetration in deeply seated neoplastic lesions, unfavorable photosensitizers (PSs) biodistribution, and photokilling efficiency due to PS aggregation in biological environments. Despite this, recent preclinical studies reported on successful combinatorial regimes of PSs with chemotherapeutics obtained through the drugs encapsulation in multifunctional nanometric delivery systems. The aim of the present review deals with the punctual description of several nanosystems designed not only with the objective of co-transporting a PS and a chemodrug for combination therapy, but also with the goal of improving the therapeutic efficacy by facing the main critical issues of both therapies (side effects, scarce tumor oxygenation and light penetration, premature drug clearance, unspecific biodistribution, etc.). Therefore, particular attention is paid to the description of bio-responsive drugs and nanoparticles (NPs), targeted nanosystems, biomimetic approaches, and upconverting NPs, including analyzing the therapeutic efficacy of the proposed photo-chemotherapeutic regimens in in vitro and in vivo cancer models.

Research progress on tumor hypoxia-associative nanomedicine

Hypoxia at the solid tumor site is generally related to the unrestricted proliferation and metabolism of cancerous cells, which can cause tumor metastasis and aggravate tumor progression. Besides, hypoxia plays a substantial role in tumor treatment, and it is one of the main reasons that malignant tumors are difficult to cure and have a poor prognosis. On account of the tumor specific hypoxic environment, many hypoxia-associative nanomedicine have been proposed for tumor treatment. Considering the enhanced targeting effect, designing hypoxia-associative nanomedicine can not only minimize the adverse effects of drugs on normal tissues, but also achieve targeted therapy at the lesion site. Mostly, there can be three strategies for the treatment of hypoxic tumor, including improvement of hypoxic environment, hypoxia responsive drug release and hypoxia activated prodrug. The review describes the design principle and applications of tumor hypoxia-associative nanomedicine in recent years, and also explores its development trends in solid tumor treatment. Moreover, this review presents the current limitations of tumor hypoxia-associative nanomedicine in chemotherapy, radiotherapy, photodynamic therapy, sonodynamic therapy and immunotherapy, which may provide a reference for clinic translation of tumor hypoxia-associative nanomedicine.

Three-dimensional in vitro culture models in oncology research

Cancer is a multifactorial disease that is responsible for 10 million deaths per year. The intra- and inter-heterogeneity of malignant tumors make it difficult to develop single targeted approaches. Similarly, their diversity requires various models to investigate the mechanisms involved in cancer initiation, progression, drug resistance and recurrence. Of the in vitro cell-based models, monolayer adherent (also known as 2D culture) cell cultures have been used for the longest time. However, it appears that they are often less appropriate than the three-dimensional (3D) cell culture approach for mimicking the biological behavior of tumor cells, in particular the mechanisms leading to therapeutic escape and drug resistance. Multicellular tumor spheroids are widely used to study cancers in 3D, and can be generated by a multiplicity of techniques, such as liquid-based and scaffold-based 3D cultures, microfluidics and bioprinting. Organoids are more complex 3D models than multicellular tumor spheroids because they are generated from stem cells isolated from patients and are considered as powerful tools to reproduce the disease development in vitro. The present review provides an overview of the various 3D culture models that have been set up to study cancer development and drug response. The advantages of 3D models compared to 2D cell cultures, the limitations, and the fields of application of these models and their techniques of production are also discussed.

The role of hypoxia-inducible factor-1 alpha in multidrug-resistant breast cancer

Breast cancer is the most common cancer in women worldwide with increasing incidence. Significant therapeutics advances in the field of breast cancer have resulted in a growing number of treatment options, whereas de novo or acquired resistance is still a persistent clinical challenge. Drug resistance involves a variety of mechanisms, and hypoxia is one of the many causes. Hypoxia-inducible Factor-1 Alpha (HIF-1α) is a key transcription factor which can regulate the response of cells to hypoxia. HIF-1α can trigger anaerobic glycolysis of tumor cells, induce angiogenesis, promote the proliferation, invasion, and migration of tumor cells, and lead to multidrug resistance. This review mainly discusses the role of HIF-1α in the drug-resistant breast cancer and highlighted the potential of HIF-1α -targeted therapy.

Mitochondrial adaptation in cancer drug resistance: prevalence, mechanisms, and management

Drug resistance represents a major obstacle in cancer management, and the mechanisms underlying stress adaptation of cancer cells in response to therapy-induced hostile environment are largely unknown. As the central organelle for cellular energy supply, mitochondria can rapidly undergo dynamic changes and integrate cellular signaling pathways to provide bioenergetic and biosynthetic flexibility for cancer cells, which contributes to multiple aspects of tumor characteristics, including drug resistance. Therefore, targeting mitochondria for cancer therapy and overcoming drug resistance has attracted increasing attention for various types of cancer. Multiple mitochondrial adaptation processes, including mitochondrial dynamics, mitochondrial metabolism, and mitochondrial apoptotic regulatory machinery, have been demonstrated to be potential targets. However, recent increasing insights into mitochondria have revealed the complexity of mitochondrial structure and functions, the elusive functions of mitochondria in tumor biology, and the targeting inaccessibility of mitochondria, which have posed challenges for the clinical application of mitochondrial-based cancer therapeutic strategies. Therefore, discovery of both novel mitochondria-targeting agents and innovative mitochondria-targeting approaches is urgently required. Here, we review the most recent literature to summarize the molecular mechanisms underlying mitochondrial stress adaptation and their intricate connection with cancer drug resistance. In addition, an overview of the emerging strategies to target mitochondria for effectively overcoming chemoresistance is highlighted, with an emphasis on drug repositioning and mitochondrial drug delivery approaches, which may accelerate the application of mitochondria-targeting compounds for cancer therapy.

The Role of Imaging Biomarkers to Guide Pharmacological Interventions Targeting Tumor Hypoxia

Hypoxia is a common feature of solid tumors that contributes to angiogenesis, invasiveness, metastasis, altered metabolism and genomic instability. As hypoxia is a major actor in tumor progression and resistance to radiotherapy, chemotherapy and immunotherapy, multiple approaches have emerged to target tumor hypoxia. It includes among others pharmacological interventions designed to alleviate tumor hypoxia at the time of radiation therapy, prodrugs that are selectively activated in hypoxic cells or inhibitors of molecular targets involved in hypoxic cell survival (i.e., hypoxia inducible factors HIFs, PI3K/AKT/mTOR pathway, unfolded protein response). While numerous strategies were successful in pre-clinical models, their translation in the clinical practice has been disappointing so far. This therapeutic failure often results from the absence of appropriate stratification of patients that could benefit from targeted interventions. Companion diagnostics may help at different levels of the research and development, and in matching a patient to a specific intervention targeting hypoxia. In this review, we discuss the relative merits of the existing hypoxia biomarkers, their current status and the challenges for their future validation as companion diagnostics adapted to the nature of the intervention.

Spatial specific delivery of combinational chemotherapeutics to combat intratumoral heterogeneity

Hypoxia-induced intratumoral heterogeneity poses a major challenge in tumor therapy due to the varying susceptibility to chemotherapy. Moreover, the spatial distribution patterns of hypoxic and normoxic tissues makes conventional combination therapy less effective. In this study, a tumor-acidity and bioorthogonal chemistry mediated in situ size transformable nanocarrier (NP@DOX_DBCO plus iCPPA_N3) was developed to spatially deliver two combinational chemotherapeutic drugs (doxorubicin (DOX) and PR104A) to combat hypoxia-induced intratumoral heterogeneity. DOX is highly toxic to tumor cells in normoxia state but less toxic in hypoxia state due to the hypoxia-induced chemoresistance. Meanwhile, PR104A is a hypoxia-activated prodrug has less toxic in normoxia state. Two nanocarriers, NP@DOX_DBCO and iCPPA_N3, can cross-link near the blood vessel extravasation sites through tumor acidity responsive bioorthogonal click chemistry to enhance the retention of DOX in tumor normoxia. Moreover, PR104A conjugated to the small-sized dendritic polyamidoamine (PAMAM) released under tumor acidity can penetrate deep tumor tissues for hypoxic tumor cell killing. Our study has demonstrated that this site-specific combination chemotherapy is better than the traditional combination chemotherapy. Therefore, spatial specific delivery of combinational therapeutics via in situ size transformable nanocarrier addresses the challenges of hypoxia induced intratumoral heterogeneity and provides insights into the combination therapy.