Reprogramming of the Tumor in the Hypoxic Niche: The Emerging Concept and Associated Therapeutic Strategies

NAC1 promotes stemness and regulates myeloid-derived cell status in triple-negative breast cancer

Triple negative breast cancer (TNBC) is a particularly lethal breast cancer (BC) subtype driven by cancer stem cells (CSCs) and an immunosuppressive microenvironment. Our study reveals that nucleus accumbens associated protein 1 (NAC1), a member of the BTB/POZ gene family, plays a crucial role in TNBC by maintaining tumor stemness and influencing myeloid-derived suppressor cells (MDSCs). High NAC1 expression correlates with worse TNBC prognosis. NAC1 knockdown reduced CSC markers and tumor cell proliferation, migration, and invasion. Additionally, NAC1 affects oncogenic pathways such as the CD44-JAK1-STAT3 axis and immunosuppressive signals (TGFβ, IL-6). Intriguingly, the impact of NAC1 on tumor growth varies with the host immune status, showing diminished tumorigenicity in natural killer (NK) cell-competent mice but increased tumorigenicity in NK cell-deficient ones. This highlights the important role of the host immune system in TNBC progression. In addition, high NAC1 level in MDSCs also supports TNBC stemness. Together, this study implies NAC1 as a promising therapeutic target able to simultaneously eradicate CSCs and mitigate immune evasion.

Investigating the role of senescence biomarkers in colorectal cancer heterogeneity by bulk and single-cell RNA sequencing

Colorectal cancer (CRC) is one of most common tumors worldwide, causing a prominent global health burden. Cell senescence is a complex physiological state, characterized by proliferation arrest. Here, we investigated the role of cellular senescence in the heterogeneity of CRC. Based on senescence-associated genes, CRC samples were classified into different senescence patterns with different survival, cancer-related biological processes and immune cell infiltrations. A senescence-related model was then developed to calculate the senescence-related score to comprehensively explore the heterogeneity of each CRC sample such as stromal activities, immunoreactivities and drug sensitivity. Single-cell analysis revealed there were different immune cell infiltrations between low and high senescence-related model genes enrichment groups, which was confirmed by multiplex immunofluorescence staining. Pseudotime analysis indicated model genes play a pivotal role in the evolution of B cells. Besides, intercellular communication modeled by NicheNet showed tumor cells with higher enrichment of senescence-related model genes highly expressed CXCL2/3 and CCL3/4, which attracted immunosuppressive cell infiltration and promoted tumor metastasis. Finally, top 6 hub genes were identified from senescence-related model genes by PPI analysis. And RT-qPCR revealed the expression differences of hub genes between normal and CRC cell lines, indicating to some extent the clinical practicability of senescence-related model. To sum up, our study explores the impact of cellular senescence on the prognosis, TME and treatment of CRC based on senescence patterns. This provides a new perspective for CRC treatment.

Intratumoral Microbiome: Foe or Friend in Reshaping the Tumor Microenvironment Landscape?

The role of the microbiome in cancer and its crosstalk with the tumor microenvironment (TME) has been extensively studied and characterized. An emerging field in the cancer microbiome research is the concept of the intratumoral microbiome, which refers to the microbiome residing within the tumor. This microbiome primarily originates from the local microbiome of the tumor-bearing tissue or from translocating microbiome from distant sites, such as the gut. Despite the increasing number of studies on intratumoral microbiome, it remains unclear whether it is a driver or a bystander of oncogenesis and tumor progression. This review aims to elucidate the intricate role of the intratumoral microbiome in tumor development by exploring its effects on reshaping the multileveled ecosystem in which tumors thrive, the TME. To dissect the complexity and the multitude of layers within the TME, we distinguish six specialized tumor microenvironments, namely, the immune, metabolic, hypoxic, acidic, mechanical and innervated microenvironments. Accordingly, we attempt to decipher the effects of the intratumoral microbiome on each specialized microenvironment and ultimately decode its tumor-promoting or tumor-suppressive impact. Additionally, we portray the intratumoral microbiome as an orchestrator in the tumor milieu, fine-tuning the responses in distinct, specialized microenvironments and remodeling the TME in a multileveled and multifaceted manner.

Autotaxin-Lysophosphatidate Axis: Promoter of Cancer Development and Possible Therapeutic Implications

Autotaxin (ATX) is a member of the ectonucleotide pyrophosphate/phosphodiesterase (ENPP) family; it is encoded by the ENPP2 gene. ATX is a secreted glycoprotein and catalyzes the hydrolysis of lysophosphatidylcholine to lysophosphatidic acid (LPA). LPA is responsible for the transduction of various signal pathways through the interaction with at least six G protein-coupled receptors, LPA Receptors 1 to 6 (LPAR1-6). The ATX-LPA axis is involved in various physiological and pathological processes, such as angiogenesis, embryonic development, inflammation, fibrosis, and obesity. However, significant research also reported its connection to carcinogenesis, immune escape, metastasis, tumor microenvironment, cancer stem cells, and therapeutic resistance. Moreover, several studies suggested ATX and LPA as relevant biomarkers and/or therapeutic targets. In this review of the literature, we aimed to deepen knowledge about the role of the ATX-LPA axis as a promoter of cancer development, progression and invasion, and therapeutic resistance. Finally, we explored its potential application as a prognostic/predictive biomarker and therapeutic target for tumor treatment.

U-Shape Pillar Strip for 3D Cell-Lumped Organoid Model (3D-COM) Mimicking Lung Cancer Hypoxia Conditions in High-Throughput Screening (HTS)

Hypoxia is a representative tumor characteristic associated with malignant progression in clinical patients. Engineered in vitro models have led to significant advances in cancer research, allowing for the investigation of cells in physiological environments and the study of disease mechanisms and processes with enhanced relevance. In this study, we propose a U-shape pillar strip for a 3D cell-lumped organoid model (3D-COM) to study the effects of hypoxia on lung cancer in a high-throughput manner. We developed a U-pillar strip that facilitates the aggregation of PDCs mixed with an extracellular matrix to make the 3D-COM in 384-plate array form. The response to three hypoxia-activated prodrugs was higher in the 3D-COM than in the 2D culture model. The protein expression of hypoxia-inducible factor 1 alpha (HIF-1α) and HIF-2α, which are markers of hypoxia, was also higher in the 3D-COM than in the 2D culture. The results show that 3D-COM better recapitulated the hypoxic conditions of lung cancer tumors than the 2D culture. Therefore, the U-shape pillar strip for 3D-COM is a good tool to study the effects of hypoxia on lung cancer in a high-throughput manner, which can efficiently develop new drugs targeting hypoxic tumors.

The cellular-centered view of hypoxia tumor microenvironment: Molecular mechanisms and therapeutic interventions

Cancer is a profoundly dynamic, heterogeneous and aggressive systemic ailment, with a coordinated evolution of various types of tumor niches. Hypoxia plays an indispensable role in the tumor micro-ecosystem, drastically enhancing the plasticity of cancer cells, fibroblasts and immune cells and orchestrating intercellular communication. Hypoxia-induced signals, particularly hypoxia-inducible factor-1α (HIF-1α), drive the reprogramming of genetic, transcriptional, and proteomic profiles. This leads to a spectrum of interconnected processes, including augmented survival of cancer cells, evasion of immune surveillance, metabolic reprogramming, remodeling of the extracellular matrix, and the development of resistance to conventional therapeutic modalities like radiotherapy and chemotherapy. Here, we summarize the latest research on the multifaceted effects of hypoxia, where a multitude of cellular and non-cellular elements crosstalk with each other and co-evolve in a synergistic manner. Additionally, we investigate therapeutic approaches targeting hypoxic niche, encompassing hypoxia-activated prodrugs, HIF inhibitors, nanomedicines, and combination therapies. Finally, we discuss some of the issues to be addressed and highlight the potential of emerging technologies in the treatment of cancer.

Hypoxia-mediated repression of pyruvate carboxylase drives immunosuppression

BACKGROUND

Metabolic plasticity mediates breast cancer survival, growth, and immune evasion during metastasis. However, how tumor cell metabolism is influenced by and feeds back to regulate breast cancer progression are not fully understood. We identify hypoxia-mediated suppression of pyruvate carboxylase (PC), and subsequent induction of lactate production, as a metabolic regulator of immunosuppression.

METHODS

We used qPCR, immunoblot, and reporter assays to characterize repression of PC in hypoxic primary tumors. Steady state metabolomics were used to identify changes in metabolite pools upon PC depletion. In vivo tumor growth and metastasis assays were used to evaluate the impact of PC manipulation and pharmacologic inhibition of lactate transporters. Immunohistochemistry, flow cytometry, and global gene expression analyzes of tumor tissue were employed to characterize the impact of PC depletion on tumor immunity.

RESULTS

PC is essential for metastatic colonization of the lungs. In contrast, depletion of PC in tumor cells promotes primary tumor growth. This effect was only observed in immune competent animals, supporting the hypothesis that repression of PC can suppress anti-tumor immunity. Exploring key differences between the pulmonary and mammary environments, we demonstrate that hypoxia potently downregulated PC. In the absence of PC, tumor cells produce more lactate and undergo less oxidative phosphorylation. Inhibition of lactate metabolism was sufficient to restore T cell populations to PC-depleted mammary tumors.

CONCLUSIONS

We present a dimorphic role for PC in primary mammary tumors vs. pulmonary metastases. These findings highlight a key contextual role for PC-directed lactate production as a metabolic nexus connecting hypoxia and antitumor immunity.

Identification of hypoxic macrophages in glioblastoma with therapeutic potential for vasculature normalization

Monocyte-derived tumor-associated macrophages (Mo-TAMs) intensively infiltrate diffuse gliomas with remarkable heterogeneity. Using single-cell transcriptomics, we chart a spatially resolved transcriptional landscape of Mo-TAMs across 51 patients with isocitrate dehydrogenase (IDH)-wild-type glioblastomas or IDH-mutant gliomas. We characterize a Mo-TAM subset that is localized to the peri-necrotic niche and skewed by hypoxic niche cues to acquire a hypoxia response signature. Hypoxia-TAM destabilizes endothelial adherens junctions by activating adrenomedullin paracrine signaling, thereby stimulating a hyperpermeable neovasculature that hampers drug delivery in glioblastoma xenografts. Accordingly, genetic ablation or pharmacological blockade of adrenomedullin produced by Hypoxia-TAM restores vascular integrity, improves intratumoral concentration of the anti-tumor agent dabrafenib, and achieves combinatorial therapeutic benefits. Increased proportion of Hypoxia-TAM or adrenomedullin expression is predictive of tumor vessel hyperpermeability and a worse prognosis of glioblastoma. Our findings highlight Mo-TAM diversity and spatial niche-steered Mo-TAM reprogramming in diffuse gliomas and indicate potential therapeutics targeting Hypoxia-TAM to normalize tumor vasculature.

Lactate in breast cancer cells is associated with evasion of hypoxia-induced cell cycle arrest and adverse patient outcome

Tumor hypoxia is a common microenvironmental factor in breast cancers, resulting in stabilization of Hypoxia-Inducible Factor 1 (HIF-1), the master regulator of hypoxic response in cells. Metabolic adaptation by HIF-1 results in inhibition of citric acid cycle, causing accumulation of lactate in large concentrations in hypoxic cancers. Lactate can therefore serve as a secondary microenvironmental factor influencing cellular response to hypoxia. Presence of lactate can alter the hypoxic response of breast cancers in many ways, sometimes in opposite manners. Lactate stabilizes HIF-1 in oxidative condition, as well as destabilizes HIF-1 in hypoxia, increases cellular acidification, and mitigates HIF-1-driven inhibition of cellular respiration. We therefore tested the effect of lactate in MDA-MB-231 under hypoxia, finding that lactate can activate pathways associated with DNA replication, and cell cycling, as well as tissue morphogenesis associated with invasive processes. Using a bioengineered nano-patterned stromal invasion assay, we also confirmed that high lactate and induced HIF-1α gene overexpression can synergistically promote MDA-MB-231 dissemination and stromal trespass. Furthermore, using The Cancer Genome Atlas, we also surprisingly found that lactate in hypoxia promotes gene expression signatures prognosticating low survival in breast cancer patients. Our work documents that lactate accumulation contributes to increased heterogeneity in breast cancer gene expression promoting cancer growth and reducing patient survival.

Hypoxia-inducible PRMT2 addiction in glioblastomas

Hypoxia-inducible transcription factors (HIFs) are key transcription factors for cellular response to low oxygen levels. However, the specific mediators responsible for activating downstream transcription are not well characterized. We previously identified Protein Arginine methyltransferase 2 (PRMT2), a highly expressed methyltransferase in glioblastoma multiforme, as a transcription co-activator. And we established a connection between PRMT2-mediated histone H3R8 asymmetric methylation (H3R8me2a) and transcription activation. Here we find that PRMT2 is activated by HIF1α under hypoxic conditions. And we demonstrate that PRMT2 and its H3R8me2a activity are required for the transcription activation of a significant subset of hypoxia-induced genes. Consequently, the inactivation of PRMT2 suppresses hypoxia-induced glioblastoma cell migration, attenuates tumor progression, and enhances chemotherapeutic sensitivity in mouse xenograft models. In addition, our analysis of clinical glioma specimens reveals a correlation between PRMT2 protein levels, HIF1α abundance, and an unfavorable prognosis. Our study establishes HIF1α-induced PRMT2 as a critical modulator in the activation of hypoxia-related transcriptional programs, ultimately driving malignant progression.

Unveiling cancer dormancy: Intrinsic mechanisms and extrinsic forces

Tumor cells disseminate in various distant organs at early stages of cancer progression. These disseminated tumor cells (DTCs) can stay dormant/quiescent without causing patient symptoms for years or decades. These dormant tumor cells survive despite curative treatments by entering growth arrest, escaping immune surveillance, and/or developing drug resistance. However, these dormant cells can reactivate to proliferate, causing metastatic progression and/or relapse, posing a threat to patients' survival. It's unclear how cancer cells maintain dormancy and what triggers their reactivation. What are better approaches to prevent metastatic progression and relapse through harnessing cancer dormancy? To answer these remaining questions, we reviewed the studies of tumor dormancy and reactivation in various types of cancer using different model systems, including the brief history of dormancy studies, the intrinsic characteristics of dormant cells, and the external cues at the cellular and molecular levels. Furthermore, we discussed future directions in the field and the strategies for manipulating dormancy to prevent metastatic progression and recurrence.

Bacteria-driven nanosonosensitizer delivery system for enhanced breast cancer treatment through sonodynamic therapy-induced immunogenic cell death

BACKGROUND

Sonodynamic therapy (SDT) has shown promise as a non-invasive cancer treatment due to its local effects and excellent tissue penetration. However, the limited accumulation of sonosensitizers at the tumor site hinders its therapeutic efficacy. Although nanosonosensitizers have improved local tumor accumulation through passive targeting via the enhanced permeability and retention effect (EPR), achieving sufficient accumulation and penetration into tumors remains challenging due to tumor heterogeneity and inaccurate targeting. Bacteria have become a promising biological carrier due to their unique characteristic of active targeting and deeper penetration into the tumor.

METHODS

In this study, we developed nanosonosensitizers consisting of sonosensitizer, hematoporphyrin monomethyl ether (HMME), and perfluoro-n-pentane (PFP) loaded poly (lactic-co-glycolic) acid (PLGA) nanodroplets (HPNDs). These HPNDs were covalently conjugated onto the surface of Escherichia coli Nissle 1917 (EcN) using carbodiimine chemistry. EcN acted as an active targeting micromotor for efficient transportation of the nanosonosensitizers to the tumor site in triple-negative breast cancer (TNBC) treatment. Under ultrasound cavitation, the HPNDs were disrupted, releasing HMME and facilitating its uptakes by cancer cells. This process induced reactive oxygen species (ROS)-mediated cell apoptosis and immunogenic cell death (ICD) in vitro and in vivo.

RESULTS

Our bacteria-driven nanosonosensitizer delivery system (HPNDs@EcN) achieved superior tumor localization of HMME in vivo compared to the group treated with only nanosonosensitizers. This enhanced local accumulation further improved the therapeutic effect of SDT induced-ICD therapeutic effect and inhibited tumor metastasis under ultrasound stimulation.

CONCLUSIONS

Our research demonstrates the potential of this ultrasound-responsive bacteria-driven nanosonosensitizer delivery system for SDT in TNBC. The combination of targeted delivery using bacteria and nanosonosensitizer-based therapy holds promise for achieving improved treatment outcomes by enhancing local tumor accumulation and stimulating ICD.

Metabolic challengers selecting tumor-persistent cells

Resistance to anticancer therapy still represents one of the main obstacles to cancer treatment. Numerous components of the tumor microenvironment (TME) contribute significantly to the acquisition of drug resistance. Microenvironmental pressures arising during cancer evolution foster tumor heterogeneity (TH) and facilitate the emergence of drug-resistant clones. In particular, metabolic pressures arising in the TME may favor epigenetic adaptations supporting the acquisition of persistence features in tumor cells. Tumor-persistent cells (TPCs) are characterized by high phenotypic and metabolic plasticity, representing a noticeable advantage in chemo- and radio-resistance. Understanding the crosslink between the evolution of metabolic pressures in the TME, epigenetics, and TPC evolution is significant for developing novel therapeutic strategies specifically targeting TPC vulnerabilities to overcome drug resistance.

Hypoxia-induced immortalization of primary cells depends on Tfcp2L1 expression

Cellular senescence is a stress response mechanism that induces proliferative arrest. Hypoxia can bypass senescence and extend the lifespan of primary cells, mainly by decreasing oxidative damage. However, how hypoxia promotes these effects prior to malignant transformation is unknown. Here we observed that the lifespan of mouse embryonic fibroblasts (MEFs) is increased when they are cultured in hypoxia by reducing the expression of p16INK4a, p15INK4b and p21Cip1. We found that proliferating MEFs in hypoxia overexpress Tfcp2l1, which is a main regulator of pluripotency and self-renewal in embryonic stem cells, as well as stemness genes including Oct3/4, Sox2 and Nanog. Tfcp2l1 expression is lost during culture in normoxia, and its expression in hypoxia is regulated by Hif1α. Consistently, its overexpression in hypoxic levels increases the lifespan of MEFs and promotes the overexpression of stemness genes. ATAC-seq and Chip-seq experiments showed that Tfcp2l1 regulates genes that control proliferation and stemness such as Sox2, Sox9, Jarid2 and Ezh2. Additionally, Tfcp2l1 can replicate the hypoxic effect of increasing cellular reprogramming. Altogether, our data suggest that the activation of Tfcp2l1 by hypoxia contributes to immortalization prior to malignant transformation, facilitating tumorigenesis and dedifferentiation by regulating Sox2, Sox9, and Jarid2.

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.

Cleanroom-Free Microfluidic Device for Natural Induction of Hypoxia in 2D and 3D Tumor Models

Hypoxia is a common and critical feature of solid tumors that contributes to the plasticity and heterogeneity of the cancer cells. Cancer cell populations take on a region-specific adaptation induced by hypoxia, and each cancer cell population will show different levels of sensitivity and resistance to cancer therapeutics. Therefore, a faithful recapitulation of tumor hypoxia that allows for accurate assessments of hypoxia-induced adaptations, heterogeneity, and response to therapy is needed to develop new therapeutic approaches. The existing hypoxic tumor models rely on complex fabrication methods and external gas sources that make them unfavorable for the early-stage screening of new therapeutics. Here, we demonstrate how to establish a cleanroom-free microfluidic device that supports both 2D and 3D hypoxic tumor modeling through natural cancer cell metabolism and confirm the induction of the hypoxic gradient.

Targeting the survival kinase DYRK1B: A novel approach to overcome radiotherapy-related treatment resistance

BACKGROUND

Cancer cell survival under stress conditions is a prerequisite for the development of treatment resistance. The survival kinase DYRK1B is a key regulator of stress survival pathways and might thereby also contribute to radiation resistance. Here we investigate the strategy of targeting DYRK1B in combination with ionizing radiation (IR) to enhance tumor cell killing under stress conditions.

METHODS

DYRK1B expression, ROS formation and DNA damage were investigated under serum-starvation (0.1% FBS), hypoxia (0.2%, 1% O2) and IR. The combined treatment modality of IR and DYRK1B inhibition was investigated in 2D and in spheroids derived from the colorectal cancer cell line SW620, and in primary patient-derived colorectal carcinoma (CRC) organoids.

RESULTS

Expression of DYRK1B was upregulated under starvation and hypoxia, but not in response to IR. The small molecule DYRK1B inhibitor AZ191 and shRNA-mediated DYRK1B knockdown significantly reduced proliferative activity and clonogenicity of SW620 tumor cells alone and in combination with IR under serum-starved conditions, which correlated with increased ROS levels and DNA damage. Furthermore, AZ191 successfully targeted the hypoxic core of tumor spheroids while IR preferentially targeted normoxic cells in the rim of the spheroids. A combined treatment effect was also observed in CRC-organoids but not in healthy tissue-derived organoids.

CONCLUSION

Combined treatment with the DYRK1B inhibitor AZ191 and IR resulted in (supra-) additive tumor cell killing in colorectal tumor cell systems and in primary CRC organoids. Mechanistic investigations support the rational to target the stress-enhanced survival kinase DYRK1B in combination with irradiation to overcome hypoxia- and starvation-induced treatment resistances.

Tumor hypoxia and radiotherapy: A major driver of resistance even for novel radiotherapy modalities

Hypoxia in solid tumors is an important predictor of poor clinical outcome to radiotherapy. Both physicochemical and biological processes contribute to a reduced sensitivity of hypoxic tumor cells to ionizing radiation and hypoxia-related treatment resistances. A conventional low-dose fractionated radiotherapy regimen exploits iterative reoxygenation in between the individual fractions, nevertheless tumor hypoxia still remains a major hurdle for successful treatment outcome. The technological advances achieved in image guidance and highly conformal dose delivery make it nowadays possible to prescribe larger doses to the tumor as part of single high-dose or hypofractionated radiotherapy, while keeping an acceptable level of normal tissue complication in the co-irradiated organs at risk. However, we insufficiently understand the impact of tumor hypoxia to single high-doses of RT and hypofractionated RT. So-called FLASH radiotherapy, which delivers ionizing radiation at ultrahigh dose rates (> 40 Gy/sec), has recently emerged as an important breakthrough in the radiotherapy field to reduce normal tissue toxicity compared to irradiation at conventional dose rates (few Gy/min). Not surprisingly, oxygen consumption and tumor hypoxia also seem to play an intriguing role for FLASH radiotherapy. Here we will discuss the role of tumor hypoxia for radiotherapy in general and in the context of novel radiotherapy treatment approaches.

EZH2-regulated PARP-1 Expression is a Likely Mechanism for the Chemoresistance of Gliomas to Temozolomide

BACKGROUND

Chemoresistance in gliomas accounts for the major cause of tumor progress and recurrence during comprehensive treatment with alkylating agents including temozolomide (TMZ). The oncogenic role of Enhancer of zeste homolog 2 (EZH2) has been identified in many solid malignancies including gliomas, though the accurate effect of EZH2 on chemotherapy resistance of gliomas has been elusive.

OBJECTIVE

To elucidate the role of EHZ2 on TMZ resistance of gliomas and the molecular mechanisms.

METHODS

Immunohistochemistry (IHC) and Reverse transcription-quantitative (RT-q) PCR, and western blot assay were performed for expressional analysis. Cell Counting Kit-8 (CCK-8) assay was applied to determine the TMZ sensitivity. EZH2-silencing lentivirus was generated for mechanic study.

RESULTS

EZH2 was overexpressed in gliomas both at the transcriptional and protein levels. EZH2 level in glioma cell lines was positively correlated with resistance to TMZ, represented by the 50% inhibition rate (IC50). Moreover, there was increased TMZ sensitivity in EZH2-inhibited glioma cells than in the control cells. Furthermore, we determined that PARP1 was a common molecule among the downregulated DNA repair proteins in both U251 and U87 glioma cell lines after EZH2 inhibition. Specifically, we observed a spontaneous increase of PARP1 expression with TMZ treatment and interestingly, the increase of PARP1 could be also reduced by EZH2 inhibition in the glioma cells. Finally, combined treatment with lentivirus-induced EZH2 inhibition and a PARP1 inhibitor dramatically enhanced TMZ cytotoxicity compared with either one alone.

CONCLUSION

EZH2-PARP-1 signaling axis is possibly responsible for the chemoresistance of gliomas to TMZ. Simultaneously inhibiting these two genes may improve the outcome of TMZ chemotherapy.

Collagen code in tumor microenvironment: Functions, molecular mechanisms, and therapeutic implications

The tumor microenvironment (TME) is crucial in cancer progression, and the extracellular matrix (ECM) is an important TME component. Collagen is a major ECM component that contributes to tumor cell infiltration, expansion, and distant metastasis during cancer progression. Recent studies reported that collagen is deposited in the TME to form a collagen wall along which tumor cells can infiltrate and prevent drugs from working on the tumor cells. Collagen-tumor cell interaction is complex and requires the activation of multiple signaling pathways for biochemical and mechanical signaling interventions. In this review, we examine the effect of collagen deposition in the TME on tumor progression and discuss the interaction between collagen and tumor cells. This review aims to illustrate the functions and mechanisms of collagen in tumor progression in the TME and its role in tumor therapy. The findings indicated collagen in the TME appears to be a better target for cancer therapy.

Mechanisms of HIF-driven immunosuppression in tumour microenvironment

Hypoxia arises due to insufficient oxygen delivery to rapidly proliferating tumour cells that outpace the available blood supply. It is a characteristic feature of most solid tumour microenvironments and plays a critical role in regulating anti-tumour immunity, enhancing tumoral heterogeneity, and promoting therapeutic resistance and poor clinical outcomes. Hypoxia-inducible factors (HIFs) are the major hypoxia-responsive transcription factors that are activated under low oxygenation conditions and have been identified to drive multifunctional roles in tumour immune evasion. The HIF signalling network serves as an attractive target for targeted therapeutic approaches. This review aims to provide a comprehensive overview of the most crucial mechanisms by which HIF controls the expression of immunosuppressive molecules and immune checkpoints, disrupts cancer immunogenicity, and induces immunotherapeutic resistance.

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.

A T Cell-Engaging Tumor Organoid Platform for Pancreatic Cancer Immunotherapy

Pancreatic ductal adenocarcinoma (PDA) is a clinically challenging disease with limited treatment options. Despite a small percentage of cases with defective mismatch DNA repair (dMMR), PDA is included in the most immune-resistant cancer types that are poorly responsive to immune checkpoint blockade (ICB) therapy. To facilitate drug discovery combating this immunosuppressive tumor type, a high-throughput drug screen platform is established with the newly developed T cell-incorporated pancreatic tumor organoid model. Tumor-specific T cells are included in the pancreatic tumor organoids by two-step cell packaging, fully recapitulating immune infiltration in the immunosuppressive tumor microenvironment (TME). The organoids are generated with key components in the original tumor, including epithelial, vascular endothelial, fibroblast and macrophage cells, and then packaged with T cells into their outside layer mimicking a physical barrier and enabling T cell infiltration and cytotoxicity studies. In the PDA organoid-based screen, epigenetic inhibitors ITF2357 and I-BET151 are identified, which in combination with anti-PD-1 based therapy show considerably greater anti-tumor effect. The combinatorial treatment turns the TME from immunosuppressive to immunoactive, up-regulates the MHC-I antigen processing and presentation, and enhances the effector T cell activity. The standardized PDA organoid model has shown great promise to accelerate drug discovery for the immunosuppressive cancer.

Dysregulated Signalling Pathways Driving Anticancer Drug Resistance

One of the leading causes of death worldwide, in both men and women, is cancer. Despite the significant development in therapeutic strategies, the inevitable emergence of drug resistance limits the success and impedes the curative outcome. Intrinsic and acquired resistance are common mechanisms responsible for cancer relapse. Several factors crucially regulate tumourigenesis and resistance, including physical barriers, tumour microenvironment (TME), heterogeneity, genetic and epigenetic alterations, the immune system, tumour burden, growth kinetics and undruggable targets. Moreover, transforming growth factor-beta (TGF-β), Notch, epidermal growth factor receptor (EGFR), integrin-extracellular matrix (ECM), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphoinositol-3-kinase/protein kinase B/mammalian target of rapamycin (PI3K/Akt/mTOR), wingless-related integration site (Wnt/β-catenin), Janus kinase/signal transducers and activators of transcription (JAK/STAT) and RAS/RAF/mitogen-activated protein kinase (MAPK) signalling pathways are some of the key players that have a pivotal role in drug resistance mechanisms. To guide future cancer treatments and improve results, a deeper comprehension of drug resistance pathways is necessary. This review covers both intrinsic and acquired resistance and gives a comprehensive overview of recent research on mechanisms that enable cancer cells to bypass barriers put up by treatments, and, like "satellite navigation", find alternative routes by which to carry on their "journey" to cancer progression.

Spatial cellular architecture predicts prognosis in glioblastoma

Intra-tumoral heterogeneity and cell-state plasticity are key drivers for the therapeutic resistance of glioblastoma. Here, we investigate the association between spatial cellular organization and glioblastoma prognosis. Leveraging single-cell RNA-seq and spatial transcriptomics data, we develop a deep learning model to predict transcriptional subtypes of glioblastoma cells from histology images. Employing this model, we phenotypically analyze 40 million tissue spots from 410 patients and identify consistent associations between tumor architecture and prognosis across two independent cohorts. Patients with poor prognosis exhibit higher proportions of tumor cells expressing a hypoxia-induced transcriptional program. Furthermore, a clustering pattern of astrocyte-like tumor cells is associated with worse prognosis, while dispersion and connection of the astrocytes with other transcriptional subtypes correlate with decreased risk. To validate these results, we develop a separate deep learning model that utilizes histology images to predict prognosis. Applying this model to spatial transcriptomics data reveal survival-associated regional gene expression programs. Overall, our study presents a scalable approach to unravel the transcriptional heterogeneity of glioblastoma and establishes a critical connection between spatial cellular architecture and clinical outcomes.

Hypoxia: syndicating triple negative breast cancer against various therapeutic regimens

Triple-negative breast cancer (TNBC) is one of the deadliest subtypes of breast cancer (BC) for its high aggressiveness, heterogeneity, and hypoxic nature. Based on biological and clinical observations the TNBC related mortality is very high worldwide. Emerging studies have clearly demonstrated that hypoxia regulates the critical metabolic, developmental, and survival pathways in TNBC, which include glycolysis and angiogenesis. Alterations to these pathways accelerate the cancer stem cells (CSCs) enrichment and immune escape, which further lead to tumor invasion, migration, and metastasis. Beside this, hypoxia also manipulates the epigenetic plasticity and DNA damage response (DDR) to syndicate TNBC survival and its progression. Hypoxia fundamentally creates the low oxygen condition responsible for the alteration in Hypoxia-Inducible Factor-1alpha (HIF-1α) signaling within the tumor microenvironment, allowing tumors to survive and making them resistant to various therapies. Therefore, there is an urgent need for society to establish target-based therapies that overcome the resistance and limitations of the current treatment plan for TNBC. In this review article, we have thoroughly discussed the plausible significance of HIF-1α as a target in various therapeutic regimens such as chemotherapy, radiotherapy, immunotherapy, anti-angiogenic therapy, adjuvant therapy photodynamic therapy, adoptive cell therapy, combination therapies, antibody drug conjugates and cancer vaccines. Further, we also reviewed here the intrinsic mechanism and existing issues in targeting HIF-1α while improvising the current therapeutic strategies. This review highlights and discusses the future perspectives and the major alternatives to overcome TNBC resistance by targeting hypoxia-induced signaling.

Natural epidithiodiketopiperazine alkaloids as potential anticancer agents: Recent mechanisms of action, structural modification, and synthetic strategies

Cancer has become a grave health crisis that threatens the lives of millions of people worldwide. Because of the drawbacks of the available anticancer drugs, the development of novel and efficient anticancer agents should be encouraged. Epidithiodiketopiperazine (ETP) alkaloids with a 2,5-diketopiperazine (DKP) ring equipped with transannular disulfide or polysulfide bridges or S-methyl moieties constitute a special subclass of fungal natural products. Owing to their privileged sulfur units and intriguing architectural structures, ETP alkaloids exhibit excellent anticancer activities by regulating multiple cancer proteins/signaling pathways, including HIF-1, NF-κB, NOTCH, Wnt, and PI3K/AKT/mTOR, or by inducing cell-cycle arrest, apoptosis, and autophagy. Furthermore, a series of ETP alkaloid derivatives obtained via structural modification showed more potent anticancer activity than natural ETP alkaloids. To solve supply difficulties from natural resources, the total synthetic routes for several ETP alkaloids have been designed. In this review, we summarized several ETP alkaloids with anticancer properties with particular emphasis on their underlying mechanisms of action, structural modifications, and synthetic strategies, which will offer guidance to design and innovate potential anticancer drugs.

Neutrophil extracellular traps induced by the hypoxic microenvironment in gastric cancer augment tumour growth

BACKGROUND

Inflammation-related predisposition to cancer plays an essential role in cancer progression and is associated with poor prognosis. A hypoxic microenvironment and neutrophil infiltration are commonly present in solid tumours, including gastric cancer (GC). Neutrophil extracellular traps (NETs) have also been demonstrated in the tumour immune microenvironment (TIME), but how NETs affect GC progression remains unknown. Here, we investigated the role of NET formation in the TIME and further explored the underlying mechanism of NETs in GC tumour growth.

METHODS

Hypoxia-induced factor-1α (HIF-1α), citrulline histone 3 (citH3) and CD66b expression in tumour and adjacent nontumor tissue samples was evaluated by western blotting, immunofluorescence and immunohistochemical staining. The expression of neutrophil-attracting chemokines in GC cells and their hypoxic-CM was measured by qRT‒PCR and ELISA. Neutrophil migration under hypoxic conditions was evaluated by a Transwell assay. Pathway activation in neutrophils in a hypoxic microenvironment were analysed by western blotting. NET formation was measured in vitro by immunofluorescence staining. The protumour effect of NETs on GC cells was identified by Transwell, wound healing and cell proliferation assays. In vivo, an lipopolysaccharide (LPS)-induced NET model and subcutaneous tumour model were established in BALB/c nude mice to explore the mechanism of NETs in tumour growth.

RESULTS

GC generates a hypoxic microenvironment that recruits neutrophils and induces NET formation. High mobility group box 1 (HMGB1) was translocated to the cytoplasm from the nucleus of GC cells in the hypoxic microenvironment and mediated the formation of NETs via the toll-like receptor 4 (TLR4)/p38 MAPK signalling pathway in neutrophils. HMGB1/TLR4/p38 MAPK pathway inhibition abrogated hypoxia-induced neutrophil activation and NET formation. NETs directly induced GC cell invasion and migration but not proliferation and accelerated the augmentation of GC growth by increasing angiogenesis. This rapid tumour growth was abolished by treatment with the NET inhibitor deoxyribonuclease I (DNase I) or a p38 MAPK signalling pathway inhibitor.

CONCLUSIONS

Hypoxia triggers an inflammatory response and NET formation in the GC TIME to augment tumour growth. Targeting NETs with DNase I or HMGB1/TLR4/p38 MAPK pathway inhibitors is a potential therapeutic strategy to inhibit GC progression. Video Abstract.

Chronic hypoxia favours adoption to a castration-resistant cell state in prostate cancer

Predicting and treating recurrence in intermediate-risk prostate cancer patients remains a challenge despite having identified genomic instability [1] and hypoxia [2, 3] as risk factors. This underlies challenges in assigning the functional impact of these risk factors to mechanisms promoting prostate cancer progression. Here we show chronic hypoxia (CH), as observed in prostate tumours [4], leads to the adoption of an androgen-independent state in prostate cancer cells. Specifically, CH results in prostate cancer cells adopting transcriptional and metabolic alterations typical of castration-resistant prostate cancer cells. These changes include the increased expression of transmembrane transporters for the methionine cycle and related pathways leading to increased abundance of metabolites and expression of enzymes related to glycolysis. Targeting of the Glucose Transporter 1 (GLUT1) identified a dependency on glycolysis in androgen-independent cells. Overall, we identified a therapeutically targetable weakness in chronic hypoxia and androgen-independent prostate cancer. These findings may offer additional strategies for treatment development against hypoxic prostate cancer.

Hypoxia switches TET1 from being tumor-suppressive to oncogenic

The classical oxidizing enzymatic activity of Ten Eleven Translocation 1 (TET1) and its tumor suppressor role are well known. Here, we find that high TET1 expression is associated with poor patient survival in solid cancers often having hypoxia, which is inconsistent with its tumor suppressor role. Through a series of in vitro and in vivo studies, using thyroid cancer as a model, we demonstrate that TET1 plays a tumor suppressor function in normoxia and, surprisingly, an oncogenic function in hypoxia. Mechanistically, TET1 mediates HIF1α-p300 interaction by acting as a co-activator of HIF1α to promote CK2B transcription under hypoxia, which is independent of its enzymatic activity; CK2 activates the AKT/GSK3β signaling pathway to promote oncogenesis. Activated AKT/GSK3β signaling in turn maintains HIF1α at elevated levels by preventing its K48-linked ubiquitination and degradation, creating a feedback loop to enhance the oncogenicity of TET1 in hypoxia. Thus, this study uncovers a novel oncogenic mechanism in which TET1 promotes oncogenesis and cancer progression through a non-enzymatic interaction between TET1 and HIF1α in hypoxia, providing novel therapeutic targeting implications for cancer.

Quercetin Nanoparticle-Based Hypoxia-Responsive Probe for Cancer Detection

In this study, we developed functional nanomaterials via a phenolic-enabled nanotechnology strategy for hypoxia detection employing quercetin (QCT), an abundant flavonoid, as a polyphenolic system. The nano form of QCT was stabilized by coating it with polyethylene glycol (PEG) before loading it with a flavylium dye (Flav) as a pH indicator. The nanosystem, Flav@QCT-PEG, collapsed when it was in an acidic environment, i.e., pH 5, leading to the release of Flav, which activated the fluorescent signal. Therefore, Flav@QCT-PEG was applied to detect hypoxic tumors, known to be acidic, and responded to hypoxic environments in a dose- and time-dependent manner.

Constructing 3D In Vitro Models of Heterocellular Solid Tumors and Stromal Tissues Using Extrusion-Based Bioprinting

Malignant tumor tissues exhibit inter- and intratumoral heterogeneities, aberrant development, dynamic stromal composition, diverse tissue phenotypes, and cell populations growing within localized mechanical stresses in hypoxic conditions. Experimental tumor models employing engineered systems that isolate and study these complex variables using in vitro techniques are under development as complementary methods to preclinical in vivo models. Here, advances in extrusion bioprinting as an enabling technology to recreate the three-dimensional tumor milieu and its complex heterogeneous characteristics are reviewed. Extrusion bioprinting allows for the deposition of multiple materials, or selected cell types and concentrations, into models based upon physiological features of the tumor. This affords the creation of complex samples with representative extracellular or stromal compositions that replicate the biology of patient tissue. Biomaterial engineering of printable materials that replicate specific features of the tumor microenvironment offer experimental reproducibility, throughput, and physiological relevance compared to animal models. In this review, we describe the potential of extrusion-based bioprinting to recreate the tumor microenvironment within in vitro models.

Notch signaling, hypoxia, and cancer

Notch signaling is involved in cell fate determination and deregulated in human solid tumors. Hypoxia is an important feature in many solid tumors, which activates hypoxia-induced factors (HIFs) and their downstream targets to promote tumorigenesis and cancer development. Recently, HIFs have been shown to trigger the Notch signaling pathway in a variety of organisms and tissues. In this review, we focus on the pro- and anti-tumorigenic functions of Notch signaling and discuss the crosstalk between Notch signaling and cellular hypoxic response in cancer pathogenesis, including epithelia-mesenchymal transition, angiogenesis, and the maintenance of cancer stem cells. The pharmacological strategies targeting Notch signaling and hypoxia in cancer are also discussed in this review.

Role of voltage-gated proton channel (Hv1) in cancer biology

The acid-base characteristics of tumor cells and the other elements that compose the tumor microenvironment have been topics of scientific interest in oncological research. There is much evidence confirming that pH conditions are maintained by changes in the patterns of expression of certain proton transporters. In the past decade, the voltage-gated proton channel (Hv1) has been added to this list and is increasingly being recognized as a target with onco-therapeutic potential. The Hv1 channel is key to proton extrusion for maintaining a balanced cytosolic pH. This protein-channel is expressed in a myriad of tissues and cell lineages whose functions vary from producing bioluminescence in dinoflagellates to alkalizing spermatozoa cytoplasm for reproduction, and regulating the respiratory burst for immune system response. It is no wonder that in acidic environments such as the tumor microenvironment, an exacerbated expression and function of this channel has been reported. Indeed, multiple studies have revealed a strong relationship between pH balance, cancer development, and the overexpression of the Hv1 channel, being proposed as a marker for malignancy in cancer. In this review, we present data that supports the idea that the Hv1 channel plays a significant role in cancer by maintaining pH conditions that favor the development of malignancy features in solid tumor models. With the antecedents presented in this bibliographic report, we want to strengthen the idea that the Hv1 proton channel is an excellent therapeutic strategy to counter the development of solid tumors.

Cancer plasticity: Investigating the causes for this agility

Cancer is not a hard-wired phenomenon but an evolutionary disease. From the onset of carcinogenesis, cancer cells continuously adapt and evolve to satiate their ever-growing proliferation demands. This results in the formation of multiple subtypes of cancer cells with different phenotypes, cellular compositions, and consequently displaying varying degrees of tumorigenic identity and function. This phenomenon is referred to as cancer plasticity, during which the cancer cells exist in a plethora of cellular states having distinct phenotypes. With the advent of modern technologies equipped with enhanced resolution and depth, for example, single-cell RNA-sequencing and advanced computational tools, unbiased cancer profiling at a single-cell resolution are leading the way in understanding cancer cell rewiring both spatially and temporally. In this review, the processes and mechanisms that give rise to cancer plasticity include both intrinsic genetic factors such as epigenetic changes, differential expression due to changes in DNA, RNA, or protein content within the cancer cell, as well as extrinsic environmental factors such as tissue perfusion, extracellular milieu are detailed and their influence on key cancer plasticity hallmarks such as epithelial-mesenchymal transition (EMT) and cancer cell stemness (CSCs) are discussed. Due to therapy evasion and drug resistance, tumor heterogeneity caused by cancer plasticity has major therapeutic ramifications. Hence, it is crucial to comprehend all the cellular and molecular mechanisms that control cellular plasticity. How this process evades therapy, and the therapeutic avenue of targeting cancer plasticity must be diligently investigated.

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.

Development and validation of a novel hypoxia-related signature for prognostic and immunogenic evaluation in head and neck squamous cell carcinoma

Hypoxia plays a critical role in head and neck squamous cell carcinoma (HNSCC) prognosis. However, till now, robust and reliable hypoxia-related prognostic signatures have not been established for an accurate prognostic evaluation in HNSCC patients. This article focused on establishing a risk score model to evaluate the prognosis and guide treatment for HNSCC patients. RNA-seq data and clinical information of 502 HNSCC patients and 44 normal samples were downloaded from The Cancer Genome Atlas (TCGA) database. 433 samples from three Gene Expression Omnibus (GEO) datasets were incorporated as an external validation cohort. In the training cohort, prognostic-related genes were screened and LASSO regression analyses were performed for signature establishment. A scoring system based on SRPX, PGK1, STG1, HS3ST1, CDKN1B, and HK1 showed an excellent prediction capacity for an overall prognosis for HNSCC patients. Patients were divided into high- and low-risk groups, and the survival status of the two groups exhibited a statistically significant difference. Subsequently, gene set enrichment analysis (GSEA) was carried out to explore the underlying mechanisms for the prognosis differences between the high- and low-risk groups. The tumor immune microenvironment was evaluated by CIBERSORT, ESTIMATE, TIDE, and xCell algorithm, etc. Then, we explored the relationships between this prognostic model and the levels of immune checkpoint-related genes. Cox regression analysis and nomogram plot indicated the scoring system was an independent predictor for HNSCC. Moreover, a comparison of predictive capability has been made between the present signature and existing prognostic signatures for HNSCC patients. Finally, we detected the expression levels of proteins encoded by six-HRGs via immunohistochemical analysis in tissue microarray. Collectively, a novel integrated signature considering both HRGs and clinicopathological parameters will serve as a prospective candidate for the prognostic evaluation of HNSCC patients.

Tumor microenvironment: barrier or opportunity towards effective cancer therapy

Tumor microenvironment (TME) is a specialized ecosystem of host components, designed by tumor cells for successful development and metastasis of tumor. With the advent of 3D culture and advanced bioinformatic methodologies, it is now possible to study TME’s individual components and their interplay at higher resolution. Deeper understanding of the immune cell’s diversity, stromal constituents, repertoire profiling, neoantigen prediction of TMEs has provided the opportunity to explore the spatial and temporal regulation of immune therapeutic interventions. The variation of TME composition among patients plays an important role in determining responders and non-responders towards cancer immunotherapy. Therefore, there could be a possibility of reprogramming of TME components to overcome the widely prevailing issue of immunotherapeutic resistance. The focus of the present review is to understand the complexity of TME and comprehending future perspective of its components as potential therapeutic targets. The later part of the review describes the sophisticated 3D models emerging as valuable means to study TME components and an extensive account of advanced bioinformatic tools to profile TME components and predict neoantigens. Overall, this review provides a comprehensive account of the current knowledge available to target TME.

Vascular normalization and immunotherapy: Spawning a virtuous cycle

Anti-angiogenics, radiotherapy (especially stereotactic body radiotherapy, SBRT)/chemotherapy, and immunotherapy form a critical trimodal approach in modern cancer therapy. The normalization window, however short, is the beachhead for the strategic initiation of a decipherable disruption of cancer cells. This opening can be the opportunity for designing controlled stepwise cancer cell death (CCD) and immunological augmentation. The next step is to induce immunogenic cell death (ICD) through chemotherapy/radiotherapy concurrently with the facilitation of professional phagocytosis. Immunotherapy at this stage, when interstitial pressure decreases considerably, leads to the improved perfusion of oxygen with solutes and improved immune-friendly pH and is additionally expected to open up the tumor microenvironment (TME) for a “flood” of tumor-infiltrating lymphocytes. Furthermore, there would be enhanced interaction in “hot” nodules and the incorporation of immune reaction in “cold” nodules. Simultaneously, the added adjuvant-assisted neoantigen–immune cell interaction will likely set in a virtuous cycle of CCD induction followed by tumor cell-specific antigenic reaction boosting CCD, in turn promoting the normalization of the vasculature, completing the loop. There should be a conscious concern to protect the extracellular matrix (ECM), which will nurture the long-term immunological cross-talk to discourage dormancy, which is as essential as obtaining a complete response in imaging. The caveat is that the available therapies should be appropriately ranked during the start of the treatment since the initial administration is the most opportune period. A fast-paced development in the nanomedicine field is likely to assist in all the steps enumerated.

The Role of the Hypoxia-Related Unfolded Protein Response (UPR) in the Tumor Microenvironment

Despite our understanding of the unfolded protein response (UPR) pathways, the crosstalk between the UPR and the complex signaling networks that different cancers utilize for cell survival remains to be, in most cases, a difficult research barrier. A major problem is the constant variability of different cancer types and the different stages of cancer as well as the complexity of the tumor microenvironments (TME). This complexity often leads to apparently contradictory results. Furthermore, the majority of the studies that have been conducted have utilized two-dimensional in vitro cultures of cancer cells that were exposed to continuous hypoxia, and this approach may not mimic the dynamic and cyclic conditions that are found in solid tumors. Here, we discuss the role of intermittent hypoxia, one of inducers of the UPR in the cellular component of TME, and the way in which intermittent hypoxia induces high levels of reactive oxygen species, the activation of the UPR, and the way in which cancer cells modulate the UPR to aid in their survival. Although the past decade has resulted in defining the complex, novel non-coding RNA-based regulatory networks that modulate the means by which hypoxia influences the UPR, we are now just to beginning to understand some of the connections between hypoxia, the UPR, and the TME.

Targeting hypoxia-induced tumor stemness by activating pathogen-induced stem cell niche defense

Tumor hypoxia and oxidative stress reprograms cancer stem cells (CSCs) to a highly aggressive and inflammatory phenotypic state of tumor stemness. Previously, we characterized tumor stemness phenotype in the ATP Binding Cassette Subfamily G Member 2 (ABCG2)–positive migratory side population (SPm) fraction of CSCs exposed to extreme hypoxia followed by reoxygenation. Here, we report that post-hypoxia/reoxygenation SPm+/ABCG2+ CSCs exerts defense against pathogen invasion that involves bystander apoptosis of non-infected CSCs. In an in vitro assay of cancer cell infection by Bacillus Calmette Guerin (BCG) or mutant Mycobacterium tuberculosis (Mtb) strain 18b (Mtb-m18b), the pathogens preferentially replicated intracellular to SPm+/ABCG2+ CSCs of seven cell lines of diverse cancer types including SCC-25 oral squamous cancer cell line. The conditioned media (CM) of infected CSCs exhibited direct anti-microbial activity against Mtb and BCG, suggesting niche defense against pathogen. Importantly, the CM of infected CSCs exhibited marked in vitro bystander apoptosis toward non-infected CSCs. Moreover, the CM-treated xenograft bearing mice showed 10- to 15-fold reduction (p < 0.001; n = 7) in the number of CSCs residing in the hypoxic niches. Our in vitro studies indicated that BCG-infected SPm+/ABCG2+ equivalent EPCAM+/ABCG2+ CSCs of SCC-25 cells underwent pyroptosis and released a high mobility group box protein 1 (HMGB1)/p53 death signal into the tumor microenvironment (TME). The death signal can induce a Toll-like receptor 2/4–mediated bystander apoptosis in non-infected CSCs by activating p53/MDM2 oscillation and subsequent activation of capase-3–dependent intrinsic apoptosis. Notably, SPm+/ABCG2+ but not SP cells undergoing bystander apoptosis amplified the death signal by further release of HMGB1/p53 complex into the TME. These results suggest that post-hypoxia SPm+/ABCG2+ CSCs serve a functional role as a tumor stemness defense (TSD) phenotype to protect TME against bacterial invasion. Importantly, the CM of TSD phenotype undergoing bystander apoptosis may have therapeutic uses against CSCs residing in the hypoxic niche.

Role of hypoxia in the tumor microenvironment and targeted therapy

Tumor microenvironment (TME), which is characterized by hypoxia, widely exists in solid tumors. As a current research hotspot in the TME, hypoxia is expected to become a key element to break through the bottleneck of tumor treatment. More and more research results show that a variety of biological behaviors of tumor cells are affected by many factors in TME which are closely related to hypoxia. In order to inhibiting the immune response in TME, hypoxia plays an important role in tumor cell metabolism and anti-apoptosis. Therefore, exploring the molecular mechanism of hypoxia mediated malignant tumor behavior and therapeutic targets is expected to provide new ideas for anti-tumor therapy. In this review, we discussed the effects of hypoxia on tumor behavior and its interaction with TME from the perspectives of immune cells, cell metabolism, oxidative stress and hypoxia inducible factor (HIF), and listed the therapeutic targets or signal pathways found so far. Finally, we summarize the current therapies targeting hypoxia, such as glycolysis inhibitors, anti-angiogenesis drugs, HIF inhibitors, hypoxia-activated prodrugs, and hyperbaric medicine.

Hypoxia Triggers TAZ Phosphorylation in Basal A Triple Negative Breast Cancer Cells

Hypoxia and HIF signaling drive cancer progression and therapy resistance and have been demonstrated in breast cancer. To what extent breast cancer subtypes differ in their response to hypoxia has not been resolved. Here, we show that hypoxia similarly triggers HIF1 stabilization in luminal and basal A triple negative breast cancer cells and we use high throughput targeted RNA sequencing to analyze its effects on gene expression in these subtypes. We focus on regulation of YAP/TAZ/TEAD targets and find overlapping as well as distinct target genes being modulated in luminal and basal A cells under hypoxia. We reveal a HIF1 mediated, basal A specific response to hypoxia by which TAZ, but not YAP, is phosphorylated at Ser89. While total YAP/TAZ localization is not affected by hypoxia, hypoxia drives a shift of [p-TAZ(Ser89)/p-YAP(Ser127)] from the nucleus to the cytoplasm in basal A but not luminal breast cancer cells. Cell fractionation and YAP knock-out experiments confirm cytoplasmic sequestration of TAZ(Ser89) in hypoxic basal A cells. Pharmacological and genetic interference experiments identify c-Src and CDK3 as kinases involved in such phosphorylation of TAZ at Ser89 in hypoxic basal A cells. Hypoxia attenuates growth of basal A cells and the effect of verteporfin, a disruptor of YAP/TAZ-TEAD–mediated transcription, is diminished under those conditions, while expression of a TAZ-S89A mutant does not confer basal A cells with a growth advantage under hypoxic conditions, indicating that other hypoxia regulated pathways suppressing cell growth are dominant.

Repositioning of Old Drugs for Novel Cancer Therapies: Continuous Therapeutic Perfusion of Aspirin and Oseltamivir Phosphate with Gemcitabine Treatment Disables Tumor Progression, Chemoresistance, and Metastases

Simple Summary

Repositioning old drugs in combination with clinical standard chemotherapeutics opens a promising clinical treatment approach for patients with pancreatic cancer. This report presents a therapeutic repositioning of continuous perfusion of aspirin and oseltamivir phosphate in combination with gemcitabine treatment as an effective treatment option for pancreatic cancer. The data suggest that repositioning these drugs with continuous perfusion with gemcitabine disables chemoresistance, tumor progression, EMT program, cancer stem cells, and metastases in a preclinical mouse model of human pancreatic cancer. These promising results warrant additional investigation to assess the potential of translating into the clinical setting to improve the cancer patient prognosis for an otherwise fatal disease.

Abstract

Metastatic pancreatic cancer has an invariably fatal outcome, with an estimated median progression-free survival of approximately six months employing our best combination chemotherapeutic regimens. Once drug resistance develops, manifested by increased primary tumor size and new and growing metastases, patients often die rapidly from their disease. Emerging evidence indicates that chemotherapy may contribute to the development of drug resistance through the upregulation of epithelial–mesenchymal transition (EMT) pathways and subsequent cancer stem cell (CSC) enrichment. Neuraminidase-1 (Neu-1) regulates the activation of several receptor tyrosine kinases implicated in EMT induction, angiogenesis, and cellular proliferation. Here, continuous therapeutic targeting of Neu-1 using parenteral perfusion of oseltamivir phosphate (OP) and aspirin (ASA) with gemcitabine (GEM) treatment significantly disrupts tumor progression, critical compensatory signaling mechanisms, EMT program, CSC, and metastases in a preclinical mouse model of human pancreatic cancer. ASA- and OP-treated xenotumors significantly inhibited the metastatic potential when transferred into animals.

Patient-derived Tumour Organoids: A Bridge between Cancer Biology and Personalised Therapy

Patient-derived tumour organoids (PDOs) have revolutionised our understanding of cancer biology and the applications of personalised therapies. These advancements are principally ascribed to the ability of PDOs to consistently recapitulate and maintain the genomic, proteomic and morphological characteristics of parental tumours. Given these characteristics, PDOs (and their extended biobanks) are a representative preclinical model eminently suited to translate relevant scientific findings into personalized therapies rapidly. Here, we summarise recent advancements in PDOs from the perspective of cancer biology and clinical applications, focusing on the current challenges and opportunities of reconstructing and standardising more sophisticated PDO models. STATEMENT OF SIGNIFICANCE: Patient-derived tumour organoids (PDOs), three-dimensional (3D) self-assembled organotypic structures, have revolutionised our understanding of cancer biology and the applications of personalised therapies. These advancements are principally ascribed to the ability of PDOs to consistently recapitulate and maintain the genomic, proteomic and morphological characteristics of parental tumours. Given these characteristics, PDOs (and their extended biobanks) are a representative preclinical model eminently suited to translate relevant scientific findings into personalized therapies rapidly.

Galectin-1 activates carbonic anhydrase IX and modulates glioma metabolism

Galectins are a family of β-galactose-specific binding proteins residing within the cytosol or nucleus, with a highly conserved carbohydrate recognition domain across many species. Accumulating evidence shows that Galectin 1 (Gal-1) plays an essential role in cancer, and its expression correlates with tumor aggressiveness and progression. Our preliminary data showed Gal-1 promotes glioma stem cell (GSC) growth via increased Warburg effect. mRNA expression and clinical data were obtained from The Cancer Genome Atlas database. The immunoblot analysis conducted using our cohort of human glioblastoma patient specimens (hGBM), confirmed Gal-1 upregulation in GBM. GC/MS analysis to evaluate the effects of Gal-1 depletion showed elevated levels of α-ketoglutaric acid, and citric acid with a concomitant reduction in lactic acid levels. Using Biolog microplate-1 mitochondrial functional assay, we confirmed that the depletion of Gal-1 increases the expression levels of the enzymes from the TCA cycle, suggesting a reversal of the Warburg phenotype. Manipulation of Gal-1 using RNA interference showed reduced ATP, lactate levels, cell viability, colony-forming abilities, and increased expression levels of genes implicated in the induction of apoptosis. Gal-1 exerts its metabolic role via regulating the expression of carbonic anhydrase IX (CA-IX), a surrogate marker for hypoxia. CA-IX functions downstream to Gal-1, and co-immunoprecipitation experiments along with proximity ligation assays confirm that Gal-1 physically associates with CA-IX to regulate its expression. Further, silencing of Gal-1 in mice models showed reduced tumor burden and increased survival compared to the mice implanted with GSC controls. Further investigation of Gal-1 in GSC progression and metabolic reprogramming is warranted.

A novel epithelial-mesenchymal transition gene signature for the immune status and prognosis of hepatocellular carcinoma

Background

This study clarified whether EMT-related genes can predict immunotherapy efficacy and overall survival in patients with HCC.

Methods

The RNA-sequencing profiles and patient information of 370 samples were derived from the Cancer Genome Atlas (TCGA) dataset, and EMT-related genes were obtained from the Molecular Signatures database. The signature model was constructed using the least absolute shrinkage and selection operator Cox regression analysis in TCGA cohort. Validation data were obtained from the International Cancer Genome Consortium (ICGC) dataset of patients with HCC. Kaplan–Meier analysis and multivariate Cox analyses were employed to estimate the prognostic value. Immune status and tumor microenvironment were estimated using a single-sample gene set enrichment analysis (ssGSEA). The expression of prognostic genes was verified using qRT-PCR analysis of HCC cell lines.

Results

A signature model was constructed using EMT-related genes to determine HCC prognosis, based on which patients were divided into high-risk and low-risk groups. The risk score, as an independent factor, was related to tumor stage, grade, and immune cells infiltration. The results indicated that the most prognostic genes were highly expressed in the HCC cell lines, but GADD45B was down-regulated. Enrichment analysis suggested that immunoglobulin receptor binding and material metabolism were essential in the prognostic signature.

Conclusion

Our novel prognostic signature model has a vital impact on immune status and prognosis, significantly helping the decision-making related to the diagnosis and treatment of patients with HCC.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12072-022-10354-3.

Recapitulating Tumor Hypoxia in a Cleanroom-Free, Liquid-Pinning-Based Microfluidic Tumor Model

In tumors, the metabolic demand of cancer cells often outpaces oxygen supply, resulting in a gradient of tumor hypoxia accompanied with heterogeneous resistance to cancer therapeutics. Models recapitulating tumor hypoxia are therefore essential for developing more effective cancer therapeutics. Existing in vitro models often fail to capture the spatial heterogeneity of tumor hypoxia or involve high-cost, complex fabrication/handling techniques. Here, we designed a highly tunable microfluidic device that induces hypoxia through natural cell metabolism and oxygen diffusion barriers. We adopted a cleanroom-free, micromilling-replica-molding strategy and a microfluidic liquid-pinning approach to streamline the fabrication and tumor model establishment. We also implemented a thin-film oxygen diffusion barrier design, which was optimized through COMSOL simulation, to support both two-dimensional (2-D) and three-dimensional (3-D) hypoxic models. We demonstrated that liquid-pinning enables an easy, injection-based micropatterning of cancer cells of a wide range of parameters, showing the high tunability of our design. Human breast cancer and prostate cancer cells were seeded and stained after 24 h of 2-D and 3-D culture to validate the natural induction of hypoxia. We further demonstrated the feasibility of the parallel microfluidic channel design to evaluate dual therapeutic conditions in the same device. Overall, our new microfluidic tumor model serves as a user-friendly, cost-effective, and highly scalable platform that provides spatiotemporal analysis of the hypoxic tumor microenvironments suitable for high-content biological studies and therapeutic discoveries.