The Cancer Cell Oxygen Sensor PHD2 Promotes Metastasis via Activation of Cancer-Associated Fibroblasts

Hypoxic Memory Mediates Prolonged Tumor-Intrinsic Type I Interferon Suppression to Promote Breast Cancer Progression

Hypoxia is a common feature of many solid tumors due to aberrant proliferation and angiogenesis that is associated with tumor progression and metastasis. Most of the well-known hypoxia effects are mediated through hypoxia-inducible factors (HIF). Identification of the long-lasting effects of hypoxia beyond the immediate HIF-induced alterations could provide a better understanding of hypoxia-driven metastasis and potential strategies to circumvent it. Here, we uncovered a hypoxia-induced mechanism that exerts a prolonged effect to promote metastasis. In breast cancer patient-derived circulating tumor cell lines and common breast cancer cell lines, hypoxia downregulated tumor-intrinsic type I IFN signaling and its downstream antigen presentation (AP) machinery in luminal breast cancer cells, via both HIF-dependent and HIF-independent mechanisms. Hypoxia induced durable IFN/AP suppression in certain cell types that was sustained after returning to normoxic conditions, presenting a "hypoxic memory" phenotype. Hypoxic memory of IFN/AP downregulation was established by specific hypoxic priming, and cells with hypoxic memory had an enhanced ability for tumorigenesis and metastasis. Overexpression of IRF3 enhanced IFN signaling and reduced tumor growth in normoxic, but not hypoxic, conditions. The histone deacetylase inhibitor entinostat upregulated IFN targets and erased the hypoxic memory. These results point to a mechanism by which hypoxia facilitates tumor progression through a long-lasting memory that provides advantages for circulating tumor cells during the metastatic cascade. Significance: Long-term cellular memory of hypoxia leads to sustained suppression of tumor-intrinsic type I IFN signaling and the antigen presentation pathway that facilitates tumorigenesis and metastasis. See related commentary by Purdy and Ford, p. 3125.

PHD1-3 oxygen sensors in vivo-lessons learned from gene deletions

Oxygen sensors enable cells to adapt to limited oxygen availability (hypoxia), affecting various cellular and tissue responses. Prolyl-4-hydroxylase domain 1-3 (PHD1-3; also called Egln1-3, HIF-P4H 1-3, HIF-PH 1-3) proteins belong to the Fe2+- and 2-oxoglutarate-dependent dioxygenase superfamily and utilise molecular oxygen (O2) alongside 2-oxoglutarate as co-substrate to hydroxylate two proline residues of α subunits of the dimeric hypoxia inducible factor (HIF) transcription factor. PHD1-3-mediated hydroxylation of HIF-α leads to its degradation and inactivation. Recently, various PHD inhibitors (PHI) have entered the clinics for treatment of renal anaemia. Pre-clinical analyses indicate that PHI treatment may also be beneficial in numerous other hypoxia-associated diseases. Nonetheless, the underlying molecular mechanisms of the observed protective effects of PHIs are only partly understood, currently hindering their translation into the clinics. Moreover, the PHI-mediated increase of Epo levels is not beneficial in all hypoxia-associated diseases and PHD-selective inhibition may be advantageous. Here, we summarise the current knowledge about the relevance and function of each of the three PHD isoforms in vivo, based on the deletion or RNA interference-mediated knockdown of each single corresponding gene in rodents. This information is crucial for our understanding of the physiological relevance and function of the PHDs as well as for elucidating their individual impact on hypoxia-associated diseases. Furthermore, this knowledge highlights which diseases may best be targeted by PHD isoform-selective inhibitors in case such pharmacologic substances become available.

Mouse Models to Evaluate the Functional Role of the Tumor Microenvironment in Cancer Progression and Therapy Responses

The tumor microenvironment (TME) is a complex ecosystem of both cellular and noncellular components that functions to impact the evolution of cancer. Various aspects of the TME have been targeted for the control of cancer; however, TME composition is dynamic, with the overall abundance of immune cells, endothelial cells (ECs), fibroblasts, and extracellular matrix (ECM) as well as subsets of TME components changing at different stages of progression and in response to therapy. To effectively treat cancer, an understanding of the functional role of the TME is needed. Genetically engineered mouse models have enabled comprehensive insight into the complex interactions within the TME ecosystem that regulate disease progression. Here, we review recent advances in mouse models that have been employed to understand how the TME regulates cancer initiation, progression, metastasis, and response to therapy.

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.

Quantitative phosphoproteomics reveals molecular pathway network alterations in human early-stage primary hepatic carcinomas: potential for 3P medical approach

Objective

Hepatic carcinoma is one of the most common types of malignant tumors in the digestive system, and its biological characteristics determine its high rate of metastasis and recurrence after radical resection, leading to a poor prognosis for patients. Increasing evidence demonstrates that phosphoproteins and phosphorylation-mediated molecular pathways influence the occurrence and development of hepatic carcinoma. It is urgent need to develop early-stage biomarkers for improving diagnosis, therapy, medical service, and prognostic assessment. We hypothesize that phosphoproteome and phosphorylation-mediated signaling pathway networks significantly differ in human early-stage primary hepatic carcinomas relative to control liver tissues, which will identify the key differentially phosphorylated proteins and phosphorylation-mediated signaling pathway network alterations in human early-stage primary hepatic carcinoma to innovate predictive diagnosis, prognostic assessment, and personalized medical services and progress beyond the state of the art in the framework of predictive, preventive, and personalized medicine (PPPM).

Methods

Tandem mass tag (TMT)-based quantitative proteomics coupled with TiO2 enrichment of phosphopeptides was used to identify phosphorylation profiling, and bioinformatics was used to analyze the pathways and biological functions of phosphorylation profiling between early-stage hepatic carcinoma tissues and tumor-adjacent normal control tissues. Furthermore, the integrative analysis with transcriptomic data from TCGA database obtained differently expressed genes (DEGs) corresponding to differentially phosphorylated proteins (DPPs) and overall survival (OS)-related DPPs.

Results

A total of 1326 phosphopeptides derived from 858 DPPs in human early-stage primary hepatic carcinoma were identified. KEGG pathway network analysis of 858 DPPs revealed 33 statistically significant signaling pathways, including spliceosome, glycolysis/gluconeogenesis, B-cell receptor signaling pathway, HIF-1 signaling pathway, and fatty acid degradation. Gene Ontology (GO) analysis of 858 DPPs revealed that protein phosphorylation was involved in 57 biological processes, 40 cellular components, and 37 molecular functions. Protein-protein interaction (PPI) network constructed multiple high-combined scores and co-expressed DPPs. Integrative analysis of transcriptomic data and DPP data identified 105 overlapped molecules (DPPs; DEGs) between hepatic carcinoma tissues and control tissues and 125 OS-related DPPs. Overlapping Venn plots showed 14 common molecules among datasets of DPPs, DEGs, and OS-related DDPs, including FTCD, NDRG2, CCT2, PECR, SLC23A2, PNPLA7, ANLN, HNRNPM, HJURP, MCM2, STMN1, TCOF1, TOP2A, and SSRP1. The drug sensitivities of OS-related DPPs were identified, including LMOD1, CAV2, UBE2E2, RAPH1, ANXA5, HDLBP, CUEDC1, APBB1IP, VCL, SRSF10, SLC23A2, EPB41L2, ESR1, PLEKHA4, SAFB2, SMARCAD1, VCAN, PSD4, RDH16, NOP56, MEF2C, BAIAP2L2, NAGS, SRSF2, FHOD3, and STMN1.

Conclusions

Identification and annotation of phosphoproteomes and phosphorylation-mediated signaling pathways in human early-stage primary hepatic carcinoma tissues provided new directions for tumor prevention and treatment, which (i) helps to enrich phosphorylation functional research and develop new biomarkers; (ii) enriches phosphorylation-mediated signaling pathways to gain a deeper understanding of the underlying mechanisms of early-stage primary hepatic carcinoma; and (iii) develops anti-tumor drugs that facilitate targeted phosphorylated sites. We recommend quantitative phosphoproteomics in early-stage primary hepatic carcinoma, which offers great promise for in-depth insight into the molecular mechanism of early-stage primary hepatic carcinoma, the discovery of effective therapeutic targets/drugs, and the construction of reliable phosphorylation-related biomarkers for patient stratification, predictive diagnosis, prognostic assessment, and personalized medical services in the framework of PPPM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00335-3.

Hypoxia as a regulator of tumor stroma and metastasis

Metastasis is the leading cause of mortality in most patients with cancer. Despite its clinical importance, mechanistic underpinnings of metastatic progression remain poorly understood. Hypoxia, a condition of insufficient oxygen availability, frequently occurs in solid tumors because of their high oxygen/nutrient demand and abnormal tumor vasculature. In this review, we describe the roles of hypoxia and hypoxia-inducible factor (HIF) signaling in the metastatic cascade, with an emphasis on recent biological insights from in vivo studies.

Molecular basis and clinical implications of HIFs in cardiovascular diseases

Oxygen maintains the homeostasis of an organism in a delicate balance in different tissues and organs. Under hypoxic conditions, hypoxia-inducible factors (HIFs) are specific and dominant factors in the spatiotemporal regulation of oxygen homeostasis. As the most basic functional unit of the heart at the cellular level, the cardiomyocyte relies on oxygen and nutrients delivered by the microvasculature to keep the heart functioning properly. Under hypoxic stress, HIFs are involved in acute and chronic myocardial pathology because of their spatiotemporal specificity, thus granting them therapeutic potential. Most adult animals lack the ability to regenerate their myocardium entirely following injury, and complete regeneration has long been a goal of clinical treatment for heart failure. The precise manipulation of HIFs (considering their dynamic balance and transformation) and the development of HIF-targeted drugs is therefore an extremely attractive cardioprotective therapy for protecting against myocardial ischemic and hypoxic injury, avoiding myocardial remodeling and heart failure, and promoting recovery of cardiac function.

Cancer-Associated Fibroblasts in the Hypoxic Tumor Microenvironment

Simple Summary

Cancers have regions of low oxygen concentration where hypoxia-related signaling pathways are activated. The hypoxic tumor microenvironment has been widely accepted as a hallmark of cancer and shown to be a critical factor in the crosstalk between cancer and stromal cells. Fibroblasts are one of the most abundant cellular components in the tumor stroma and are also significantly affected by oxygen deprivation. In this case, we discuss the molecular and cellular mechanisms that regulate fibroblasts under hypoxic conditions and their effect on cancer development and progression. Unraveling these regulatory mechanisms could be exploited in developing potential fibroblast-specific therapeutics for cancer.

Abstract

Solid cancers are composed of malignant cells and their surrounding matrix components. Hypoxia plays a critical role in shaping the tumor microenvironment that contributes to cancer progression and treatment failure. Cancer-associated fibroblasts (CAFs) are one of the most prominent components of the tumor microenvironment. CAFs are highly sensitive to hypoxia and participates in the crosstalk with cancer cells. Hypoxic CAFs modulate several mechanisms that induce cancer malignancy, such as extracellular matrix (ECM) remodeling, immune evasion, metabolic reprogramming, angiogenesis, metastasis, and drug resistance. Key signaling molecules regulating CAFs in hypoxia include transforming growth factor (TGF-β) and hypoxia-inducible factors (HIFs). In this article, we summarize the mechanisms underlying the hypoxic regulation of CAFs and how hypoxic CAFs affect cancer development and progression. We also discuss the potential therapeutic strategies focused on targeting CAFs in the hypoxic tumor microenvironment.

The multifaceted role of EGLN family prolyl hydroxylases in cancer: going beyond HIF regulation

EGLN1, EGLN2 and EGLN3 are proline hydroxylase whose main function is the regulation of the HIF factors. They work as oxygen sensors and are the main responsible of HIFα subunits degradation in normoxia. Being their activity strictly oxygen-dependent, when oxygen tension lowers, their control on HIFα is released, leading to activation of systemic and cellular response to hypoxia. However, EGLN family members activity is not limited to HIF modulation, but it includes the regulation of essential mechanisms for cell survival, cell cycle metabolism, proliferation and transcription. This is due to their reported hydroxylase activity on a number of non-HIF targets and sometimes to hydroxylase-independent functions. For these reasons, EGLN enzymes appear fundamental for development and progression of different cancer types, playing either a tumor-suppressive or a tumor-promoting role, according to EGLN isoform and to tumor context. Notably, EGLN1, the most studied isoform, has been shown to have also a central role in tumor micro-environment modulation, mediating CAF activation and impairing HIF1α -related angiogenesis, thus covering an important function in cancer metastasis promotion. Considering the recent knowledge acquired on EGLNs, the possibility to target these enzymes for cancer treatment is emerging. However, due to their multifaceted and controversial roles in different cancer types, the use of EGLN inhibitors as anti-cancer drugs should be carefully evaluated in each context.

The risk variant rs11836367 contributes to breast cancer onset and metastasis by attenuating Wnt signaling via regulating NTN4 expression

Most genome-wide association study (GWAS)-identified breast cancer-associated causal variants remain uncharacterized. To provide a framework of understanding GWAS-identified variants to function, we performed a comprehensive study of noncoding regulatory variants at the NTN4 locus (12q22) and NTN4 gene in breast cancer etiology. We find that rs11836367 is the more likely causal variant, disrupting enhancer activity in both enhancer reporter assays and endogenous genome editing experiments. The protective T allele of rs11837367 increases the binding of GATA3 to the distal enhancer and up-regulates NTN4 expression. In addition, we demonstrate that loss of NTN4 gene in mice leads to tumor earlier onset, progression, and metastasis. We discover that NTN4, as a tumor suppressor, can attenuate the Wnt signaling pathway by directly binding to Wnt ligands. Our findings bridge the gaps among breast cancer-associated single-nucleotide polymorphisms, transcriptional regulation of NTN4, and breast cancer biology, which provides previously unidentified insights into breast cancer prediction and prevention.

Hypoxia as a Modulator of Inflammation and Immune Response in Cancer

A clear association between hypoxia and cancer has heretofore been established; however, it has not been completely developed. In this sense, the understanding of the tumoral microenvironment is critical to dissect the complexity of cancer, including the reduction in oxygen distribution inside the tumoral mass, defined as tumoral hypoxia. Moreover, hypoxia not only influences the tumoral cells but also the surrounding cells, including those related to the inflammatory processes. In this review, we analyze the participation of HIF, NF-κB, and STAT signaling pathways as the main components that interconnect hypoxia and immune response and how they modulate tumoral growth. In addition, we closely examine the participation of the immune cells and how they are affected by hypoxia, the effects of the progression of cancer, and some innovative applications that take advantage of this knowledge, to suggest potential therapies. Therefore, we contribute to the understanding of the complexity of cancer to propose innovative therapeutic strategies in the future.

Breast Cancer CAFs: Spectrum of Phenotypes and Promising Targeting Avenues

Activationof the tumor-associated stroma to support tumor growth is a common feature observed in different cancer entities. This principle is exemplified by cancer-associated fibroblasts (CAFs), which are educated by the tumor to shape its development across all stages. CAFs can alter the extracellular matrix (ECM) and secrete a variety of different molecules. In that manner they have the capability to affect activation, survival, proliferation, and migration of other stromal cells and cancer cell themselves. Alteration of the ECM, desmoplasia, is a common feature of breast cancer, indicating a prominent role for CAFs in shaping tumor development in the mammary gland. In this review, we summarize the multiple roles CAFs play in mammary carcinoma. We discuss experimental and clinical strategies to interfere with CAFs function in breast cancer. Moreover, we highlight the issues arising from CAFs heterogeneity and the need for further research to identify CAFs subpopulation(s) that can be targeted to improve breast cancer therapy.

Vascular Normalization: A New Window Opened for Cancer Therapies

Preclinical and clinical antiangiogenic approaches, with multiple side effects such as resistance, have not been proved to be very successful in treating tumor blood vessels which are important targets for tumor therapy. Meanwhile, restoring aberrant tumor blood vessels, known as tumor vascular normalization, has been shown not only capable of reducing tumor invasion and metastasis but also of enhancing the effectiveness of chemotherapy, radiation therapy, and immunotherapy. In addition to the introduction of such methods of promoting tumor vascular normalization such as maintaining the balance between proangiogenic and antiangiogenic factors and targeting endothelial cell metabolism, microRNAs, and the extracellular matrix, the latest molecular mechanisms and the potential connections between them were primarily explored. In particular, the immunotherapy-induced normalization of blood vessels further promotes infiltration of immune effector cells, which in turn improves immunotherapy, thus forming an enhanced loop. Thus, immunotherapy in combination with antiangiogenic agents is recommended. Finally, we introduce the imaging technologies and serum markers, which can be used to determine the window for tumor vascular normalization.

Collagen type 1 alpha 1 chain is a novel predictive biomarker of poor progression-free survival and chemoresistance in metastatic lung cancer

Background: Collagen type 1 alpha 1 chain (COL1A1) is an extracellular matrix protein comprising two alpha 1 chains and one alpha 2 chain. Our previous study identified that COL1A1 is the key gene during the development and progression of lung adenocarcinoma by multi-omics analysis. However, the clinical significance of COL1A1 expression in lung cancer samples remains largely unknown. Here, we aimed to evaluate the level of COL1A1 in lung cancer samples and correlate its level with the clinical outcome.

Methods:COL1A1 gene expression in lung cancer samples was analyzed using the Oncomine database (www.oncomine.org). A total of 308 lung cancer samples (208 formalin-fixed paraffin-embedded tissues and 100 blood samples) were assessed for protein expression of COL1A1. Immunohistochemistry staining and enzyme-linked immunosorbent assay were used to detect COL1A1 expression in tissues and serum, respectively.

Results: We identified an elevation of COL1A1 in mRNA level and gene amplification in lung cancer tissues compared with normal lung tissues. High COL1A1 expression was observed in lung cancer tissues and serum (P < 0.05), it was significantly correlated with the peripheral type tumor, the larger diameter of the tumor, the occurrence of lymph node metastases and distant metastases, a higher TNM stage, and smoking (P < 0.05). High COL1A1 expression was associated with poor progression-free survival (PFS) and chemoresistance in lung cancer patients (P < 0.05). Multivariable Cox-regression analysis showed that COL1A1 expression was an independent prognostic factor (P < 0.05). Furthermore, the area under the receiver operating characteristic (AUC) curve was 0.909 for the combined COL1A1 and carcinoembryonic antigen (CEA) measurement.

Conclusion: Our findings revealed that COL1A1 could be used as a novel diagnostic, prognostic, and chemoresistance biomarker of human lung cancer, and these results provide a potential therapeutic strategy for lung cancer patients.

Regulation of Extracellular Matrix Production in Activated Fibroblasts: Roles of Amino Acid Metabolism in Collagen Synthesis

Cancer associated fibroblasts (CAFs) are a major component of the tumour microenvironment in most tumours, and are key mediators of the response to tissue damage caused by tumour growth and invasion, contributing to the observation that tumours behave as 'wounds that do not heal'. CAFs have been shown to play a supporting role in all stages of tumour progression, and this is dependent on the highly secretory phenotype CAFs develop upon activation, of which extracellular matrix (ECM) production is a key element. A collagen rich, stromal ECM has been shown to influence tumour growth and metastasis, exclude immune cells and impede drug delivery, and is associated with poor prognosis in many cancers. CAFs also extensively remodel their metabolism to support cancer cells, however, it is becoming clear that metabolic rewiring also supports intrinsic functions of activated fibroblasts, such as increased ECM production. In this review, we summarise how fibroblasts metabolically regulate ECM production, focussing on collagen production, at the transcriptional, translational and post-translational level, and discuss how this can provide possible strategies for effectively targeting CAF activation and formation of a tumour-promoting stroma.

Perspectives on Hypoxia Signaling in Tumor Stroma

Hypoxia is a well-known characteristic of solid tumors that contributes to tumor progression and metastasis. Oxygen deprivation due to high demand of proliferating cancer cells and standard of care therapies induce hypoxia. Hypoxia signaling, mainly mediated by the hypoxia-inducible transcription factor (HIF) family, results in tumor cell migration, proliferation, metabolic changes, and resistance to therapy. Additionally, the hypoxic tumor microenvironment impacts multiple cellular and non-cellular compartments in the tumor stroma, including disordered tumor vasculature, homeostasis of ECM. Hypoxia also has a multifaceted and often contradictory influence on immune cell function, which contributes to an immunosuppressive environment. Here, we review the important function of HIF in tumor stromal components and summarize current clinical trials targeting hypoxia. We provide an overview of hypoxia signaling in tumor stroma that might help address some of the challenges associated with hypoxia-targeted therapies.

The non-canonical functions of HIF prolyl hydroxylases and their dual roles in cancer

The hypoxia-inducible factor (HIF) prolyl hydroxylases (PHDs) are dioxygenases using oxygen and 2-oxoglutarate as co-substrates. Under normoxia, PHDs hydroxylate the conserved prolyl residues of HIFα, leading to HIFα degradation. In hypoxia PHDs are inactivated, which results in HIFα accumulation. The accumulated HIFα enters nucleus and initiates gene transcription. Many studies have shown that PHDs have substrates other than HIFα, implying that they have HIF-independent non-canonical functions. Besides modulating protein stability, the PHDs-mediated prolyl hydroxylation affects protein-protein interaction and protein activity for alternative substrates. Increasing evidence indicates that PHDs also have hydroxylase-independent functions. They influence protein stability, enzyme activity, and protein-protein interaction in a hydroxylase-independent manner. These findings highlight the functional diversity and complexity of PHDs. Due to having inhibitory activity on HIFα, PHDs are proposed to act as tumor suppressors. However, research shows that PHDs exert either tumor-promoting or tumor-suppressing features. Here, we try to summarize the current understanding of PHDs hydroxylase-dependent and -independent functions and their roles in cancer.

Reduction of Liver Metastasis Stiffness Improves Response to Bevacizumab in Metastatic Colorectal Cancer

Tumors are influenced by the mechanical properties of their microenvironment. Using patient samples and atomic force microscopy, we found that tissue stiffness is higher in liver metastases than in primary colorectal tumors. Highly activated metastasis-associated fibroblasts increase tissue stiffness, which enhances angiogenesis and anti-angiogenic therapy resistance. Drugs targeting the renin-angiotensin system, normally prescribed to treat hypertension, inhibit fibroblast contraction and extracellular matrix deposition, thereby reducing liver metastases stiffening and increasing the anti-angiogenic effects of bevacizumab. Patients treated with bevacizumab showed prolonged survival when concomitantly treated with renin-angiotensin inhibitors, highlighting the importance of modulating the mechanical microenvironment for therapeutic regimens.

PHD2 acts as an oncogene through activation of Ras/Raf/MEK/ERK and JAK1/STAT3 pathways in human hepatocellular carcinoma cells

Background: Prolyl hydroxylase domain proteins (PHD2) is an oxygen sensor that is able to induce hypoxia-inducible factor-α (HIF-α) degradation under normoxic condition. The present paper designed to reveal the function of PHD2 in hepatocellular carcinoma (HCC) cells proliferation, migration and invasion.Methods: qRT-PCR and Western blot were carried out to see the expression of PHD2 in HCC tissues and cell lines. PHD2 expression in Huh7 and HepG3B cells was overexpressed or suppressed by transfection and then the changes of cell proliferation, migration and invasion were detected by CCK-8 assay, transwell assay and Western blot.Results: PHD2 was highly expressed in HCC tissues and cell lines (Huh7, Hep3B, SK-HEP-1, HCCLM3 and MHCC97) as relative to para-cancerous non-tumour tissues and a normal hepatocyte line MIHA. PHD2 overexpression promoted Huh7 and Hep3B cells viability, migration and invasion. Meanwhile, CyclinD1, c-Myc, MMP-2, MMP-9 and Vimentin were up-regulated, while p53 was down-regulated by PHD2 overexpression. PHD2 silence led to a contrary impact. Further, PHD2 overexpression up-regulated Ras and Raf expression and induced phosphorylation of MEK, ERK, JAK1 and STAT3.Conclusion: PHD2 exhibited pro-tumour functions in HCC cells. PHD2 promoted HCC possibly through Ras/Raf/MEK/ERK and JAK1/STAT3 pathways.HighlightsPHD2 is highly expressed in HCC tissue and cell lines;PHD2 promotes the proliferation of Huh7 and HepG3B cells;PHD2 enhances Huh7 and HepG3B cells migration and invasion;PHD2 activates Ras/Raf/MEK/ERK and JAK1/STAT3 signalling.

Prolyl hydroxylase 2 silencing enhances the paracrine effects of mesenchymal stem cells on necrotizing enterocolitis in an NF-κB-dependent mechanism

Treatment options for necrotizing enterocolitis (NEC) remain inadequate. Here we examined if and how prolyl hydroxylase 2 (PHD2) silencing enhances the paracrine effects of bone-marrow-derived mesenchymal stem cells (BM-MSCs) on NEC. In this study, BM-MSCs were transduced with lentiviruses containing GFP (GFP-MSC) or shPHD2-GFP constructs (PHDMSC), followed by intraperitoneal injection of the PHDMSC-conditioned medium (PHDMSC-CM) or the GFP-MSC-conditioned medium (MSC-CM) into a rat pup model of NEC. Our results showed that systemic infusion of PHDMSC-CM, but not MSC-CM, significantly improved intestinal damage and survival of NEC rats. Such benefits may involve the modulation of epithelial regeneration and inflammation, as indicated by the regeneration of intestinal epithelial/stem cells, the regulation of Treg cells function and pro-/anti-inflammatory cytokine balance. The mechanism for the superior paracrine efficacy of PHDMSC is related to a higher release of pivotal factor IGF-1 and TGF-β2. NF-κB activation was induced by PHD2 silencing to induce IGF-1 and TGF-β2 secretion via binding to IGF-1 and TGF-β2 gene promoter. Our work indicated that PHD2 silencing enhanced the paracrine effect of BM-MSCs on NEC via the NF-κB-dependent mechanism which may be a novel strategy for stem cell therapy on NEC.

Systemic long-term inactivation of hypoxia-inducible factor prolyl 4-hydroxylase 2 ameliorates aging-induced changes in mice without affecting their life span

Hypoxia inactivates hypoxia-inducible factor (HIF) prolyl 4-hydroxylases (HIF-P4Hs), which stabilize HIF and upregulate genes to restore tissue oxygenation. HIF-P4Hs can also be inhibited by small molecules studied in clinical trials for renal anemia. Knowledge of systemic long-term inactivation of HIF-P4Hs is limited but crucial, since HIF overexpression is associated with cancers. We aimed to determine the effects of systemic genetic inhibition of the most abundant isoenzyme HIF prolyl 4-hydroxylase-2 (HIF-P4H-2)/PHD2/EglN1 on life span and tissue homeostasis in aged mice. Our data showed no difference between wild-type and HIF-P4H-2-deficient mice in the average age reached. There were several differences, however, in the primary causes of death and comorbidities, the HIF-P4H-2-deficient mice having less inflammation, liver diseases, including cancer, and myocardial infarctions, and not developing anemia. No increased cancer incidence was observed due to HIF-P4H-2-deficiency. These data suggest that chronic inactivation of HIF-P4H-2 is not harmful but rather improves the quality of life in senescence.

Cellular and Extracellular Components in Tumor Microenvironment and Their Application in Early Diagnosis of Cancers

Tumors are surrounded by complex environmental components, including blood and lymph vessels, fibroblasts, endothelial cells, immune cells, cytokines, extracellular vesicles, and extracellular matrix. All the stromal components together with the tumor cells form the tumor microenvironment (TME). In addition, extracellular physical and chemical factors, including extracellular pH, hypoxia, elevated interstitial fluid pressure, and fibrosis, are closely associated with tumor progression, metastasis, immunosuppression, and drug resistance. Cellular and extracellular components in TME contribute to nearly all procedures of carcinogenesis. By summarizing the recent work in this field, we make a comprehensive review on the role of cellular and extracellular components in the process of carcinogenesis and their potential application in early diagnosis of cancer. We hope that a systematic review of the diverse aspects of TME will help both research scientists and clinicians in this field.

Bone morphogenetic protein 4 provides cancer-supportive phenotypes to liver fibroblasts in patients with hepatocellular carcinoma

BACKGROUND

Cancer-associated fibroblasts (CAFs) are essential constituents of cancer-supportive microenvironments. The high incidence of hepatocellular carcinoma (HCC) in advanced fibrosis patients implies that fibroblasts have a promoting effect on HCC development. We aimed to explore the regulators of phenotypes and function of CAFs in the liver.

METHODS

We established primary cancer-associated fibroblasts (CAFs) and non-cancerous liver fibroblasts (NFs) from 15 patients who underwent HCC resection. We compared phenotypes, capacity of cytokine/chemokine production and gene expression profiles between pairs of CAFs and NFs from the same donors. We examined resected tissue from additional 50 patients with HCC for immunohistochemical analyses.

RESULTS

The CAFs expressed more ACTA2 and COL1A1 than the NFs, suggesting that CAFs are more activated phenotype. The CAFs produced larger amounts of IL-6, IL-8 and CCL2 than the NFs, which led to invasiveness of HuH7 in vitro. We found that Bone Morphogenetic Protein-4 (BMP4) is up-regulated in CAFs compared to NFs. The CAF phenotype and function were gained by BMP4 over-expression or recombinant BMP4 given to fibroblasts, all of which decreased with BMP4 knockdown. In tissues obtained from the patients, BMP4-positive cells are mainly observed in encapsulated fibrous lesions and HCC. Positive expression of BMP4 in HCC in resected tissues, not in fibroblasts, was associated with poorer postoperative overall survival in patients with HCC.

CONCLUSION

Endogenous and exogenous BMP4 activate liver fibroblasts to gain capacity of secreting cytokines and enhancing invasiveness of cancer cells in the liver. BMP4 is one of the regulatory factors of CAFs functioning in the microenvironment of HCC.

Normalization of Tumor Vasculature by Oxygen Microbubbles with Ultrasound

Tumor microenvironment influences the efficacy of anti-cancer therapies. The dysfunctional tumor vasculature limits the efficiency of oxygenation and drug delivery to reduce treatment outcome. A concept of tumor vascular normalization (VN), which inhibits angiogenesis to improve vessel maturity, blood perfusion, and oxygenation, has been demonstrated under the anti-angiogenic therapy. The efficiency of drug delivery and penetration is increased by enhancing perfusion and reducing interstitial fluid pressure during the time window of VN. However, anti-angiogenic agents only induce transient VN and then prune vessels to aggravate tumor hypoxia. To repair tumor vessels without altering vessel density, we proposed to induce tumor VN by local oxygen release via oxygen microbubbles with ultrasound. With tumor perfusion enhancement under ultrasound contrast imaging tracing, the time window of VN was defined as 2-8 days after a single oxygen microbubble treatment. The enhanced tumor oxygenation after oxygen microbubble treatment inhibited hypoxia inducible factor-1 alpha (HIF-1α)/vascular endothelial growth factor (VEGF) pathway to improve the morphology and function of tumor vasculature. The pericyte coverage and Hoechst penetration of tumor vessels increased without any changes to the vessel density. Finally, the intratumoral accumulation of anti-cancer drug doxorubicin could be increased 3-4 folds during tumor VN. These findings demonstrate that regulating tumor oxygenation by oxygen microbubbles could normalize dysfunctional vessels to enhance vascular maturity, blood perfusion, and drug penetration. Furthermore, ultrasound perfusion imaging provides a simple and non-invasive way to detect the VN time window, which increases the feasibility of VN in clinical cancer applications.

Cancer-associated fibroblasts-heroes or villains?

Cancer-associated fibroblasts (CAFs) were originally presumed to represent a homogeneous population uniformly driving tumorigenesis, united by their morphology and peritumoural location. Our understanding of CAFs has since been shaped by sophisticated in vitro and in vivo experiments, pathological association and, more recently, ablation, and it is now widely appreciated that CAFs form a group of highly heterogeneous cells with no single overarching marker. Studies have demonstrated that the CAF population contains different subtypes based on the expression of marker proteins with the capacity to promote or inhibit cancer, with their biological role as accomplices or adversaries dependent on many factors, including the cancer stage. So, while CAFs have been endlessly shown to promote the growth, survival and spread of tumours via improvements in functionality and an altered secretome, they are also capable of retarding tumorigenesis via largely unknown mechanisms. It is important to reconcile these disparate results so that the functions of, or factors produced by, tumour-promoting subtypes can be specifically targeted to improve cancer patient outcomes. This review will dissect out CAF complexity and CAF-directed cancer treatment strategies in order to provide a case for future, rational therapies.

Glycosylation in the Tumor Microenvironment: Implications for Tumor Angiogenesis and Metastasis

Just as oncogene activation and tumor suppressor loss are hallmarks of tumor development, emerging evidence indicates that tumor microenvironment-mediated changes in glycosylation play a crucial functional role in tumor progression and metastasis. Hypoxia and inflammatory events regulate protein glycosylation in tumor cells and associated stromal cells in the tumor microenvironment, which facilitates tumor progression and also modulates a patient's response to anti-cancer therapeutics. In this review, we highlight the impact of altered glycosylation on angiogenic signaling and endothelial cell adhesion, and the critical consequences of these changes in tumor behavior.

PHD-2 activation: a novel strategy to control HIF-1α and mitochondrial stress to modulate mammary gland pathophysiology in ER+ subtype

Estrogen receptor-positive mammary gland carcinoma and its involvement in regulation of overexpressed hypoxia-inducible factor-1α and fatty acid synthase level in hypoxia influenced cancer cells are the present molecular crosstalk of this entire study. To test the hypothesis, we have proceed our study through chemical activation of prolyl hydroxylase 2 which leads to inhibition of hypoxia-inducible factor-1α and fatty acid synthase in ER+MCF-7 cancer cell line and n-methyl-n-nitrosourea induced mammary gland carcinoma rat model. ER+MCF-7 cells were evident with array of nuclear changes when stained through acridine orange/ethidium bromide. Afterward, JC-1 staining of the cells was evident in mitochondrial depolarization. The cells were arrested in G2/M phase when analyzed with flow cytometry. The morphological analysis of rat mammary gland tissue revealed decrease in alveolar buds, restoration of histopathological features along with intra-arterial cushion. The western blotting and fold change expressions of the genes validating the anticancer efficacy of BBAPH-1 is mediated through mitochondria-mediated apoptosis pathway. BBAPH-1 also modulates the expression of prolyl hydroxylase-2 with significant curtailment of hypoxia-inducible factor-1α, fatty acid synthase expression, and their respective downstream markers. These finding suggest that the BBAP-1-mediated activation of prolyl hydroxylase-2 significantly decreased the level of hypoxia-inducible factor-1α and fatty acid synthase. BBAPH-1 also activates the mitochondria-mediated death apoptosis pathway.

Modern ideas about the origin, features of morphology, prognostic and predictive significance of tumor vessels

The review presents modern ideas about the origin of tumor vessels and the features of their morphology. The various approaches to the classification of tumor vessel types and to the assessment of their clinical and prognostic significance are described. Also, the main problems associated with the use of angiogenesis blockers in the treatment of malignancies and their possible solutions are reflected in the review.

Stress responses in stromal cells and tumor homeostasis

In most (if not all) solid tumors, malignant cells are outnumbered by their non-malignant counterparts, including immune, endothelial and stromal cells. However, while the mechanisms whereby cancer cells adapt to microenvironmental perturbations have been studied in great detail, relatively little is known on stress responses in non-malignant compartments of the tumor microenvironment. Here, we discuss the mechanisms whereby cancer-associated fibroblasts and other cellular components of the tumor stroma react to stress in the context of an intimate crosstalk with malignant, endothelial and immune cells, and how such crosstalk influences disease progression and response to treatment.

Activation of prolyl hydroxylase-2 for stabilization of mitochondrial stress along with simultaneous downregulation of HIF-1α/FASN in ER + breast cancer subtype

The present study was undertaken to inquest the chemical activation of prolyl hydroxylase-2 for the curtailment of hypoxia-inducible factor-1α and fatty acid synthase. It was well documented that hypoxia-inducible factor-1α and fatty acid synthase were overexpressed in mammary gland carcinomas. After screening a battery of compounds, BBAP-2 was retrieved as a potential prolyl hydroxylase-2 activator and validates its activity using ER + MCF-7 cell line and n-methyl-n-nitrosourea-induced rat in vivo model, respectively. BBAP-2 was palpable for the morphological characteristics of apoptosis along with changes in the mitochondrial intergrity as visualized by acridine orange/ethidium bromide and JC-1 staining against ER + MCF-7 cells. BBAP-2 also arrest the cell cycle of ER + MCF-7 cells at G2/M phase. Afterward, BBAP-2 has scrutinized against n-methyl-n-nitrosourea-induced mammary gland carcinoma in albino Wistar rats. BBAP-2 restored the morphological architecture when screened through carmine staining, haematoxylin and eosin staining, and scanning electron microscopy. BBAP-2 also delineated the markers of oxidative stress favourably. The immunoblotting and mRNA expression analysis validated that BBAP-2 has a potentialty activate the prolyl hydroxylase-2 with sequential downregulating effect on hypoxia-inducible factor-1α and its downstream checkpoint. BBAP-2 also fostered apoptosis through mitochondrial-mediated death pathway. The present study elaborates the chemical activation of prolyl hydroxylase-2 by which the increased expression of HIF-1α and FASN can be reduced in mammary gland carcinoma.

The roles and signaling pathways of prolyl-4-hydroxylase 2 in the tumor microenvironment

Tumor hypoxia is a well-known microenvironmental factor that causes cancer progression and resistance to cancer treatment. Proline hydroxylases (PHDs), a small protein family, belong to an evolutionarily conserved superfamily of dioxygenases, considered the central regulator of the molecular hypoxia response. Prolyl-4-hydroxylase 2 (PHD2), one member of PHDs family, regulates the stability of the hypoxia-inducible factor-1 alpha (HIF-1α) in response to oxygen availability. During hypoxia, the inhibition of PHD2 permits the accumulation of HIF-1α, allowing the cellular adaptation to oxygen limitation, causing activation of numerous genes, which enhances the angiogenesis, metastasis and invasiveness. Accurate regulation of oxygen homeostasis is essential, and which implies PHD2 may have a regulatory role in the pathogenesis of cancer. Although ample evidence exists for a positive correlation between HIFs and tumor formation, metastasis and poor prognosis, the function of the PHD2 in carcinogenesis is less well understood. Despite their original role as the oxygen sensors of the cell and many of the its functions are clearly conveyed through the HIF system, PHD2 is currently known to display HIF-independent and hydroxylase-independent functions in cancer cells and stroma in the control of different cellular pathways. In this review, we summarize the recent advances in the structure, regulation and functions of PHD2 in cancer microenvironment.

Hypoxia Pathway Proteins in Normal and Malignant Hematopoiesis

The regulation of oxygen (O₂) levels is crucial in embryogenesis and adult life, as O₂ controls a multitude of key cellular functions. Low oxygen levels (hypoxia) are relevant for tissue physiology as they are integral to adequate metabolism regulation and cell fate. Hence, the hypoxia response is of utmost importance for cell, organ and organism function and is dependent on the hypoxia-inducible factor (HIF) pathway. HIF pathway activity is strictly regulated by the family of oxygen-sensitive HIF prolyl hydroxylase domain (PHD) proteins. Physiologic hypoxia is a hallmark of the hematopoietic stem cell (HSC) niche in the bone marrow. This niche facilitates HSC quiescence and survival. The present review focuses on current knowledge and the many open questions regarding the impact of PHDs/HIFs and other proteins of the hypoxia pathway on the HSC niche and on normal and malignant hematopoiesis.

Loss of Phd2 cooperates with BRAFV600E to drive melanomagenesis

Prolyl hydroxylase domain protein 2 (PHD2) is a well-known master oxygen sensor. However, the role of PHD2 in tumor initiation remains controversial. We find that during the transition of human nevi to melanoma, the expression of PHD2 protein is significantly decreased and lower expression PHD2 in melanoma is associated with worse clinical outcome. Knockdown of PHD2 leads to elevated Akt phosphorylation in human melanocytes. Mice with conditional melanocyte-specific expression of Phd2^lox/lox (Tyr::CreER;Phd2^lox/lox) fail to develop pigmented lesions. However, deletion of Phd2 in combination with expression of BRaf^V600E in melanocytes (Tyr::CreER;Phd2^lox/lox;BRaf^CA) leads to the development of melanoma with 100% penetrance and frequent lymph node metastasis. Analysis of tumor tissues using reverse phase protein arrays demonstrates that Phd2 deletion activates the AKT-mTOR-S6 signaling axis in the recovered tumors. These data indicate that PHD2 is capable of suppressing tumor initiation largely mediated through inhibiting of the Akt-mTOR signaling pathway in the melanocyte lineage.

Prolyl hydroxylase domain protein 2 (PHD2) regulates cellular response to hypoxia. Here the authors show that PHD2 is downregulated in melanoma and that PHD2 depletion, in a mouse model, promotes the progression of benign melanocytic lesions into melanoma, via activation of the Akt/mTOR signaling cascade.

Diagnostic role of circulating extracellular matrix-related proteins in non-small cell lung cancer

Background

Interactions between cancer cells and the surrounding microenvironment are crucial determinants of cancer progression. During this process, bi-directional communication among tumor cells and cancer associated fibroblasts (CAF) regulate extracellular matrix (ECM) deposition and remodeling. As a result of this dynamic process, soluble ECM proteins can be released into the bloodstream and may represent novel circulating biomarkers useful for cancer diagnosis. The aim of the present study was to measure the levels of three circulating ECM related proteins (COL11A1, COL10A1 and SPARC) in plasma samples of lung cancer patients and in healthy heavy-smokers controls and test whether such measurements have diagnostic or prognostic value.

Methods

Gene expression profiling of lung fibroblasts isolated from paired normal and cancer tissue of NSCLC patients was performed by gene expression microarrays. The prioritization of the candidates for the study of circulating proteins in plasma was based on the most differentially expressed genes in cancer associated fibroblasts. Soluble ECM proteins were assessed by western blot in the conditioned medium of lung fibroblasts and by ELISA assays in plasma samples.

Results

Plasma samples from lung cancer patients and healthy heavy-smokers controls were tested for levels of COL11A1 and COL10A1 (n = 57 each) and SPARC (n = 90 each). Higher plasma levels of COL10A1 were detected in patients (p ≤ 0.001), a difference that was driven specifically by females (p < 0.001). No difference in COL11A1 levels between patients and controls was found. SPARC levels were also higher in plasma patients than controls (p < 0.001) with good performance in discriminating the two groups (AUC = 0.744). No significant association was observed between plasma proteins levels and clinicopathological features or survival.

Conclusion

Soluble factors related to proficient tumor-stroma cross-talk are detectable in plasma of primary lung cancer patients and may represent a valuable complementary diagnostic tool to discriminate lung cancer patients from healthy heavy-smokers individuals as shown for the SPARC protein.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4772-0) contains supplementary material, which is available to authorized users.

Hypoxic Signalling in Tumour Stroma

Hypoxia is a common feature in solid tumors and is associated with cancer progression. The main regulators of the hypoxic response are hypoxia-inducible transcription factors (HIFs) that guide the cellular adaptation to hypoxia by gene activation. The actual oxygen sensing is performed by HIF prolyl hydroxylases (PHDs) that under normoxic conditions mark the HIF-α subunit for degradation. Cancer progression is not regulated only by the cancer cells themselves but also by the whole tumor microenvironment, which consists of cellular and extracellular components. Hypoxic conditions also affect the stromal compartment, where stromal cells are in close contact with the cancer cells. The important function of HIF in cancer cells has been shown by many animal models and described in hundreds of reviews, but less in known about PHDs and even less PHDs in stromal cells. Here, we review hypoxic signaling in tumors, mainly in the tumor stroma, with a focus on HIFs and PHDs.

Chemical activation of prolyl hydroxylase-2 by BBAP-1 down regulates hypoxia inducible factor-1α and fatty acid synthase for mammary gland chemoprevention

(4-[7-(Acetyloxy)-2-ethyl-2H-chromen-3-yl] phenyl acetate) (BBAP-1) was identified as a potential prolyl hydroxylase-2 activator and tested for this activity using the 2-oxoglutarate dependent in vitro assay. BBAP-1 was evaluated for its cytotoxic potential against ER + MCF-7 cells, and N-methyl-N-nitrosourea induced estrogen positive mammary gland carcinoma model. The effect of BBAP-1 on cellular morphology was evaluated using in vitro acridine orange/ethidium bromide and JC-1 staining. The morphological symptoms of apoptosis were evident after BBAP-1 treatment when studied through cell staining using acridine orange/ethidium bromide and JC-1 dye. Flow cytometric analysis revealed that BBAP-1 treatment arrested the cell cycle in the G2/M phase. In vivo study revealed the morphological changes of mammary gland tissue when scrutinized using carmine staining, hematoxylin and eosin staining and scanning electron microscopy. BBAP-1 treatment produced a marked effect on histopathological and morphological features when scrutinized against N-methyl-N-nitrosourea induced mammary gland carcinoma. Treatment with BBAP-1 also attenuated the deleterious effects of N-methyl-N-nitrosourea as measured on the basis of oxidative stress markers. Immunoblotting and qRT-PCR analysis revealed the participation of BBAP-1 in the mitochondrial mediated death apoptosis pathway and BBAP-1 also downregulated the hypoxic pathway through activation of prolyl hydroxylase-2. It was concluded that BBAP-1 activated the prolyl hydroxylase-2 enzyme and curtailed the over expression of hypoxia inducible factor-1α and fatty acid synthase along with the mitochondrial mediated death apoptosis pathway.

Podoplanin-positive cancer-associated fibroblast recruitment within cancer stroma is associated with a higher number of single nucleotide variants in cancer cells in lung adenocarcinoma

PURPOSE

Podoplanin-positive cancer-associated fibroblasts (CAFs) play an essential role in tumor progression. However, it is still unclear whether specific genomic alterations of cancer cells are required to recruit podoplanin-positive CAFs. The aim of this study was to investigate the relationship between the mutation status of lung adenocarcinoma cells and the presence of podoplanin-positive CAFs.

METHODS

Ninety-seven lung adenocarcinomas for which whole exome sequencing data were available were enrolled. First, we analyzed the clinicopathological features of the cases, and then, evaluated the relationship between genetic features of cancer cells (major driver mutations and the number of single nucleotide variants, SNVs) and the presence of podoplanin-positive CAFs.

RESULTS

The presence of podoplanin-positive CAFs was associated with smoking history, solid predominant subtype, and lymph node metastasis. We could not find any significant correlations between major genetic mutations (EGFR, KRAS, TP53, MET, ERBB2, BRAF, and PIC3CA) in cancer cells and the presence of podoplanin-positive CAFs. However, cases with podoplanin-positive CAFs had a significantly higher number of SNVs in cancer cells than the podoplanin-negative CAFs cases (median 84 vs 37, respectively; p = 0.001). This was also detected in a non-smoker subgroup (p = 0.037). Multivariate analyses revealed that the number of SNVs in cancer cells was the only statistically significant independent predictor for the presence of podoplanin-positive CAFs (p = 0.044).

CONCLUSIONS

In lung adenocarcinoma, the presence of podoplanin-positive CAFs was associated with higher numbers of SNVs in cancer cells, suggesting a relationship between accumulations of SNVs in cancer cells and the generation of a tumor-promoting microenvironment.

Cancer Associated Fibroblasts: The Architects of Stroma Remodeling

Fibroblasts have exceptional phenotypic plasticity and capability to secrete vast amount of soluble factors, extracellular matrix components and extracellular vesicles. While in physiological conditions this makes fibroblasts master regulators of tissue homeostasis and healing of injured tissues, in solid tumors cancer associated fibroblasts (CAFs) co-evolve with the disease, and alter the biochemical and physical structure of the tumor microenvironment, as well as the behavior of the surrounding stromal and cancer cells. Thus CAFs are fundamental regulators of tumor progression and influence response to therapeutic treatments. Increasing efforts are devoted to better understand the biology of CAFs to bring insights to develop complementary strategies to target this cell type in cancer. Here we highlight components of the tumor microenvironment that play key roles in cancer progression and invasion, and provide an extensive overview of past and emerging understanding of CAF biology as well as the contribution that MS-based proteomics has made to this field.

Hypoxia-inducible factor prolyl hydroxylase 2 (PHD2) is a direct regulator of epidermal growth factor receptor (EGFR) signaling in breast cancer

Clinical studies in breast cancer suggest important associations between intratumoral hypoxia, the upregulation of epidermal growth factor receptor (EGFR or HER1), hypoxia-inducible factor 1α (HIF-1α), and reduced patient survival. However, direct molecular links between EGFR and the hypoxia signaling system are not yet established. Since the oxygen sensor hypoxia-inducible factor prolyl hydroxylase 2 (PHD2) is considered to be the main HIF-1α regulator, we hypothesized that PHD2 and EGFR may be interconnected at the molecular level. By analyzing samples from 313 breast cancer patients, we found that EGFR is a first clinicopathological parameter positively correlating with PHD2. Mechanistically, we identified PHD2 as a direct binding partner of EGFR and show that PHD2 regulates EGFR stability as well as its subsequent signaling in breast carcinoma cells. Overall, we introduce for the first time the direct crosstalk between the oxygen sensor PHD2 and EGFR-mediated tumorigenesis in breast cancer.

Hypoxia Pathway Proteins As Central Mediators of Metabolism in the Tumor Cells and Their Microenvironment

Low oxygen tension or hypoxia is a determining factor in the course of many different processes in animals, including when tissue expansion and cellular metabolism result in high oxygen demands that exceed its supply. This is mainly happening when cells actively proliferate and the proliferating mass becomes distant from the blood vessels, such as in growing tumors. Metabolic alterations in response to hypoxia can be triggered in a direct manner, such as the switch from oxidative phosphorylation to glycolysis or inhibition of fatty acid desaturation. However, as the modulated action of hypoxia-inducible factors or the oxygen sensors (prolyl hydroxylase domain-containing enzymes) can also lead to changes in enzyme expression, these metabolic changes can also be indirect. With this review, we want to summarize our current knowledge of the hypoxia-induced changes in metabolism during cancer development, how they are affected in the tumor cells and in the cells of the microenvironment, most prominently in immune cells.

PHD3 Controls Lung Cancer Metastasis and Resistance to EGFR Inhibitors through TGFα

Lung cancer is the leading cause of cancer-related death worldwide, in large part due to its high propensity to metastasize and to develop therapy resistance. Adaptive responses to hypoxia and epithelial-mesenchymal transition (EMT) are linked to tumor metastasis and drug resistance, but little is known about how oxygen sensing and EMT intersect to control these hallmarks of cancer. Here, we show that the oxygen sensor PHD3 links hypoxic signaling and EMT regulation in the lung tumor microenvironment. PHD3 was repressed by signals that induce EMT and acted as a negative regulator of EMT, metastasis, and therapeutic resistance. PHD3 depletion in tumors, which can be caused by the EMT inducer TGFβ or by promoter methylation, enhanced EMT and spontaneous metastasis via HIF-dependent upregulation of the EGFR ligand TGFα. In turn, TGFα stimulated EGFR, which potentiated SMAD signaling, reinforcing EMT and metastasis. In clinical specimens of lung cancer, reduced PHD3 expression was linked to poor prognosis and to therapeutic resistance against EGFR inhibitors such as erlotinib. Reexpression of PHD3 in lung cancer cells suppressed EMT and metastasis and restored sensitivity to erlotinib. Taken together, our results establish a key function for PHD3 in metastasis and drug resistance and suggest opportunities to improve patient treatment by interfering with the feedforward signaling mechanisms activated by PHD3 silencing.Significance: This study links the oxygen sensor PHD3 to metastasis and drug resistance in cancer, with implications for therapeutic improvement by targeting this system. Cancer Res; 78(7); 1805-19. ©2018 AACR.

Emerging tumor spheroids technologies for 3D in vitro cancer modeling

Cancer is a leading cause of mortality and morbidity worldwide. Around 90% of deaths are caused by metastasis and just 10% by primary tumor. The advancement of treatment approaches is not at the same rhythm of the disease; making cancer a focal target of biomedical research. To enhance the understanding and prompts the therapeutic delivery; concepts of tissue engineering are applied in the development of in vitro models that can bridge between 2D cell culture and animal models, mimicking tissue microenvironment. Tumor spheroid represents highly suitable 3D organoid-like framework elucidating the intra and inter cellular signaling of cancer, like that formed in physiological niche. However, spheroids are of limited value in studying critical biological phenomenon such as tumor-stroma interactions involving extra cellular matrix or immune system. Therefore, a compelling need of tailoring spheroid technologies with physiologically relevant biomaterials or in silico models, is ever emerging. The diagnostic and prognostic role of spheroids rearrangements within biomaterials or microfluidic channel is indicative of patient management; particularly for the decision of targeted therapy. Fragmented information on available in vitro spheroid models and lack of critical analysis on transformation aspects of these strategies; pushes the urge to comprehensively overview the recent technological advancements (e.g. bioprinting, micro-fluidic technologies or use of biomaterials to attain the third dimension) in the shed of translationable cancer research. In present article, relationships between current models and their possible exploitation in clinical success is explored with the highlight of existing challenges in defining therapeutic targets and screening of drug efficacy.

Pharmacological HIF-inhibition attenuates postoperative adhesion formation

Peritoneal adhesions represent a common complication of abdominal surgery, and tissue hypoxia is a main determinant in adhesion formation. Reliable therapeutic options to reduce peritoneal adhesions are scarce. We investigated whether the formation of postsurgical adhesions can be affected by pharmacological interference with hypoxia-inducible factors (HIFs). Mice were treated with a small molecule HIF-inhibitor, YC-1 (3-[5′-Hydroxymethyl-2′-furyl]-1-benzyl-indazole), or vehicle three days before and seven days after induction of peritoneal adhesions or, alternatively, once during induction of peritoneal adhesions. Pretreatment or single intraperitoneal lavage with YC-1 significantly reduced postoperative adhesion formation without prompting systemic adverse effects. Expression analyses of cytokines in peritoneal tissue and fluid and in vitro assays applying macrophages and peritoneal fibroblasts indicated that this effect was cooperatively mediated by various putatively HIF-1α-dependent mechanisms, comprising attenuated pro-inflammatory activation of macrophages, impaired recruitment and activation of peritoneal fibroblasts, mitigated epithelial-mesenchymal-transition (EMT), as well as enhanced fibrinolysis and impaired angiogenesis. Thus, this study identifies prevention of postsurgical peritoneal adhesions as a novel and promising field for the application of HIF inhibitors in clinical practice.

Hypoxia inducible factor (HIF) in the tumor microenvironment: friend or foe?

Hypoxia acts as an important regulator of physiological and pathological processes. Hypoxia inducible factors (HIFs) are the central players involved in the cellular adaptation to hypoxia and are regulated by oxygen sensing EGLN prolyl hydroxylases. Hypoxia affects many aspects of cellular growth through both redox effects and through the stabilization of HIFs. The HIF isoforms likely have differential effects on tumor growth via alteration of metabolism, growth, and self-renewal and are likely highly context-dependent. In some tumors such as renal cell carcinoma, the EGLN/HIF axis appears to drive tumorigenesis, while in many others HIF1 and HIF2 may actually have a tumor suppressive role. An emerging role of HIF biology is its effects on the tumor microenvironment. The EGLN/HIF axis plays a key role in regulating the function of the various components of the tumor microenvironment, which include cancer-associated fibroblasts, endothelial cells, immune cells, and the extracellular matrix (ECM). Here, we discuss hypoxia and the diverse roles of HIFs in the setting of tumorigenesis and the maintenance of the tumor microenvironment as well as possible future directions of the field.

Tumor vessel disintegration by maximum tolerable PFKFB3 blockade

Blockade of the glycolytic activator PFKFB3 in cancer cells (using a maximum tolerable dose of 70 mg/kg of the PFKFB3 blocker 3PO) inhibits tumor growth in preclinical models and is currently being tested as a novel anticancer treatment in phase I clinical trials. However, a detailed preclinical analysis of the effects of such maximum tolerable dose of a PFKFB3 blocker on the tumor vasculature is lacking, even though tumor endothelial cells are hyper-glycolytic. We report here that a high dose of 3PO (70 mg/kg), which inhibits cancer cell proliferation and reduces primary tumor growth, causes tumor vessel disintegration, suppresses endothelial cell growth for protracted periods, (model-dependently) aggravates tumor hypoxia, and compromises vascular barrier integrity, thereby rendering tumor vessels more leaky and facilitating cancer cell intravasation and dissemination. These findings contrast to the effects of a low dose of 3PO (25 mg/kg), which induces tumor vessel normalization, characterized by vascular barrier tightening and maturation, but reduces cancer cell intravasation and metastasis. Our findings highlight the importance of adequately dosing a glycolytic inhibitor for anticancer treatment.