Hypoxia: a barricade to conquer the pancreatic cancer

Role of the m6A demethylase ALKBH5 in gastrointestinal tract cancer (Review)

N6‑methyladenosine (m6A) is one of the most universal, abundant and conserved types of internal post‑transcriptional modifications in eukaryotic RNA, and is involved in nuclear RNA export, RNA splicing, mRNA stability, gene expression, microRNA biogenesis and long non‑coding RNA metabolism. AlkB homologue 5 (ALKBH5) acts as a m6A demethylase to regulate a wide variety of biological processes closely associated with tumour progression, tumour metastasis, tumour immunity and tumour drug resistance. ALKBH5 serves a crucial role in human digestive system tumours, mainly through post‑transcriptional regulation of m6A modification. The present review discusses progress in the study of the m6A demethylase ALKBH5 in gastrointestinal tract cancer, summarizes the potential molecular mechanisms of ALKBH5 dysregulation in gastrointestinal tract cancer, and discusses the significance of ALKBH5‑targeted therapy, which may provide novel ideas for future clinical prognosis prediction, biomarker identification and precise treatment.

The Mechanism and Latest Progress of m6A Methylation in the Progression of Pancreatic Cancer

Pancreatic cancer (PC), known as the "king of cancers," is characterized by an exceptionally low five-year survival rate, posing a formidable challenge to global public health. N6-methyladenosine (m6A) methylation is prevalent across various stages of eukaryotic RNA expression, including splicing, maturation, stability, translation, and localization, and represents a pivotal mechanism of epigenetic regulation. m6A methylation influences tumor initiation and progression by modulating post-transcriptional processes, playing a critical role in sustaining cancer cell stemness, promoting cell proliferation, and mediating drug resistance. Extensive research underscores the substantial contribution of m6A modifications to PC development. However, the multiplicity of m6A regulators and their intricate mechanisms of action complicate the landscape. This review aims to deepen the understanding of m6A's role in PC by delineating its involvement in four key areas of tumorigenesis: the hypoxic tumor microenvironment, metabolic reprogramming, immune microenvironment, and resistance mechanisms. Additionally, the review addresses the emerging frontier of m6A interactions with non-coding RNAs (ncRNAs), offering insights into the potential therapeutic and prognostic applications of m6A in the treatment and prognosis prediction of PC.

Investigating the effects of stereotactic body radiation therapy on pancreatic tumor hypoxia and microvasculature in an orthotopic mouse model using intravital fluorescence microscopy

Despite decades of improvements in cytotoxic therapy, the current standard of care for locally advanced pancreatic cancer (LAPC) provides, on average, only a few months of survival benefit. Stereotactic Body Radiation Therapy (SBRT), a technique that accurately delivers high doses of radiation to tumors in fewer fractions, has emerged as a promising therapy to improve local control of LAPC; however, its effects on the tumor microenvironment and hypoxia remain poorly understood. To explore how SBRT affects pancreatic tumors, we combined an orthotopic mouse model of pancreatic cancer with an intravital microscopy platform to visualize changes to the in vivo tumor microenvironment in real-time. Mice received SBRT (5 × 8 Gy) or were left untreated, and were imaged before and 1, 4, 7, and 14 days after treatment (n = 7/group). A fluorescent human pancreatic cancer cell line (BxPC3-DsRed) engineered to express GFP under hypoxic conditions (driven by hypoxia-inducible factor, HIF) was used to monitor tumor hypoxia. Immunohistochemical staining was also performed on tissues to validate in vivo data. Our findings demonstrate a persistent decrease in pancreatic tumor hypoxia as early as one day after SBRT. This coincided with a decrease in both tumor cell proliferation and cell density in the SBRT group. Reduced demand for oxygen after SBRT (due to cell death and growth arrest from treatment) significantly contributed to reoxygenation of the pancreatic TME. Understanding how this reoxygenation phenomenon occurs in a dose-dependent manner will help improve dosing and fractionation schemes for clinical SBRT.

A review on dendrimer-based nanoconjugates and their intracellular trafficking in cancer photodynamic therapy

Nanotechnology-based cancer treatment has received considerable attention, and these treatments generally use drug-loaded nanoparticles (NPs) to target and destroy cancer cells. Nanotechnology combined with photodynamic therapy (PDT) has demonstrated positive outcomes in cancer therapy. Combining nanotechnology and PDT is effective in targeting metastatic cancer cells. Nanotechnology can also increase the effectiveness of PDT by targeting cells at a molecular level. Dendrimer-based nanoconjugates (DBNs) are highly stable and biocompatible, making them suitable for drug delivery applications. Moreover, the hyperbranched structures in DBNs have the capacity to load hydrophobic compounds, such as photosensitizers (PSs) and chemotherapy drugs, and deliver them efficiently to tumour cells. This review primarily focuses on DBNs and their potential applications in cancer treatment. We discuss the chemical design, mechanism of action, and targeting efficiency of DBNs in tumour metastasis, intracellular trafficking in cancer treatment, and DBNs' biocompatibility, biodegradability and clearance properties. Overall, this study will provide the most recent insights into the application of DBNs and PDT in cancer therapy.

Hypoxia-related bioinformatic signatures associated with prognosis and tumor microenvironment of pancreatic cancer: Current status, concerns, and future perspectives

Pancreatic cancer (PC), a highly lethal tumor with nearly identical incidence and mortality rates, has become the sixth leading cause of cancer-related deaths. Hypoxia is an important malignant factor in PC, as it regulates angiogenesis, metabolic reprogramming, tumor progression, and metastasis. Disrupting the hypoxic microenvironment can enhance the efficacy of antitumor therapy and improve the prognosis of patients with PC. With the advent of bioinformatics, hypoxia-related PC models have emerged in recent years. They provide a reference for estimating the prognosis and immune microenvironment of patients with PC and identify potential biomarkers for targeting hypoxic microenvironment. However, these findings based on bioinformatic analysis may not be completely reliable without further experimental evidence and clinical cohort validation. The application of these models and biomarkers in clinical practice to predict survival time and develop anti hypoxic therapeutic strategies for patients with PC remains in its infancy. In this editorial, we review the current status of hypoxia-related prognostic models in PC, analyze their similarities and differences, discuss several existing challenges, and provide potential solutions and directions for further studies. This editorial will facilitate the optimization, validation, and determination of the molecular mechanisms of related models.

Correlation of dynamic contrast-enhanced ultrasonography and the Ki-67 labelling index in pancreatic ductal adenocarcinoma

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly malignant and aggressive tumor, and high Ki-67 expression indicates poor histological differentiation and prognosis. Therefore, one of the challenges in diagnosing preoperatively patients with PDAC is predicting the degree of malignancy. Dynamic contrast-enhanced ultrasonography (DCE-US) plays a crucial role in abdominal tumor diagnosis, and can adequately show the microvascular composition within the tumors. However, the relationship between DCE-US and the Ki-67 labelling index remains unclear at the present time.

AIM

To predict the correlation between Ki-67 expression and the parameters of DCE-US.

METHODS

Patients with PDAC who underwent DCE-US were retrospectively analyzed. Patients who had received any treatment (radiotherapy or chemotherapy) prior to DCE-US; had incomplete clinical, imaging, or pathologic information; and had poor-quality image analysis were excluded. Correlations between Ki-67 expression and the parameters of DCE-US in patients with PDAC were assessed using Spearman's rank correlation analysis. The diagnostic performances of these parameters in high Ki-67 expression group were evaluated according to receiver operating characteristic curve.

RESULTS

Based on the Ki-67 labelling index, 30 patients were divided into two groups, i.e., the high expression group and the low expression group. Among the relative quantitative parameters between the two groups, relative half-decrease time (rHDT), relative peak enhancement, relative wash-in perfusion index and relative wash-in rate were significantly different between two groups (P = 0.018, P = 0.025, P = 0.028, P = 0.035, respectively). The DCE-US parameter rHDT was moderately correlated with Ki-67 expression, and rHDT ≥ 1.07 was more helpful in accurately diagnosing high Ki-67 expression, exhibiting a sensitivity and specificity of 53.8% and 94.1%, respectively.

CONCLUSION

One parameter of DCE-US, rHDT, correlates with high Ki-67 expression. It demonstrates that parameters obtained noninvasively by DCE-US could better predict Ki-67 expression in PDAC preoperatively.

Pin1: Advances in pancreatic cancer therapeutic potential and inhibitors research

The peptidyl-prolyl cis/trans isomerase NIMA-interaction 1 (Pin1) catalyzes the transition of the proline ring from the cis to trans conformation, resulting in conformational and functional changes in proteins that are regulated by proline-guided serine/threonine phosphorylation. In recent years, Pin1 has emerged as a novel molecular target for the diagnosis and treatment of various malignant tumors. Notably, it has been found that Pin1 is highly expressed in pancreatic cancer. This article focuses on the mechanisms by which Pin1 orchestrates multiple oncogenic functions in the development of pancreatic cancer. By exploring the intricate interactions between Pin1 and the pancreatic tumor microenvironment, we provide an overview of Pin1's role in modifying glycolytic metabolism, redox balance, and the hypoxic microenvironment of pancreatic cancer. Furthermore, we summarize the potential anticancer effects of Pin1 inhibitors, aiming to elucidate Pin1's promise as a potential anticancer agent, particularly in the context of pancreatic cancer.

Nano-sensitizer with self-amplified drug release and hypoxia normalization properties potentiates efficient chemoradiotherapy of pancreatic cancer

The hypoxic nature of pancreatic cancer, one of the most lethal malignancies worldwide, significantly impedes the effectiveness of chemoradiotherapy. Although the development of oxygen carriers and hypoxic sensitizers has shown promise in overcoming tumor hypoxia. The heterogeneity of hypoxia-primarily caused by limited oxygen penetration-has posed challenges. In this study, we designed a hypoxia-responsive nano-sensitizer by co-loading tirapazamine (TPZ), KP372-1, and MK-2206 in a metronidazole-modified polymeric vesicle. This nano-sensitizer relies on efficient endogenous NAD(P)H quinone oxidoreductase 1-mediated redox cycling induced by KP372-1, continuously consuming periphery oxygen and achieving evenly distributed hypoxia. Consequently, the normalized tumor microenvironment facilitates the self-amplified release and activation of TPZ without requiring deep penetration. The activated TPZ and metronidazole further sensitize radiotherapy, significantly reducing the radiation dose needed for extensive cell damage. Additionally, the coloaded MK-2206 complements inhibition of therapeutic resistance caused by Akt activation, synergistically enhancing the hypoxic chemoradiotherapy. This successful hypoxia normalization strategy not only overcomes hypoxia resistance in pancreatic cancer but also provides a potential universal approach to sensitize hypoxic tumor chemoradiotherapy by reshaping the hypoxic distribution.

Construction and validation of a pancreatic cancer prognostic model based on genes related to the hypoxic tumor microenvironment

BACKGROUND

Pancreatic cancer is one of the most lethal malignancies, characterized by poor prognosis and low survival rates. Traditional prognostic factors for pancreatic cancer offer inadequate predictive accuracy, often failing to capture the complexity of the disease. The hypoxic tumor microenvironment has been recognized as a significant factor influencing cancer progression and resistance to treatment. This study aims to develop a prognostic model based on key hypoxia-related molecules to enhance prediction accuracy for patient outcomes and to guide more effective treatment strategies in pancreatic cancer.

AIM

To develop and validate a prognostic model for predicting outcomes in patients with pancreatic cancer using key hypoxia-related molecules.

METHODS

This pancreatic cancer prognostic model was developed based on the expression levels of the hypoxia-associated genes CAPN2, PLAU, and CCNA2. The results were validated in an independent dataset. This study also examined the correlations between the model risk score and various clinical features, components of the immune microenvironment, chemotherapeutic drug sensitivity, and metabolism-related pathways. Real-time quantitative PCR verification was conducted to confirm the differential expression of the target genes in hypoxic and normal pancreatic cancer cell lines.

RESULTS

The prognostic model demonstrated significant predictive value, with the risk score showing a strong correlation with clinical features: It was significantly associated with tumor grade (G) (b P < 0.01), moderately associated with tumor stage (T) (a P < 0.05), and significantly correlated with residual tumor (R) status (b P < 0.01). There was also a significant negative correlation between the risk score and the half-maximal inhibitory concentration of some chemotherapeutic drugs. Furthermore, the risk score was linked to the enrichment of metabolism-related pathways in pancreatic cancer.

CONCLUSION

The prognostic model based on hypoxia-related genes effectively predicts pancreatic cancer outcomes with improved accuracy over traditional factors and can guide treatment selection based on risk assessment.

SIRT7 knockdown promotes gemcitabine sensitivity of pancreatic cancer cell via upregulation of GLUT3 expression

Gemcitabine serves as a first-line chemotherapeutic treatment for pancreatic cancer (PC), but it is prone to rapid drug resistance. Increasing the sensitivity of PC to gemcitabine has long been a focus of research. Fasting interventions may augment the effects of chemotherapy and present new options. SIRT7 is known to link metabolism with various cellular processes through post-translational modifications. We found upregulation of SIRT7 in PC cells is associated with poor prognosis and gemcitabine resistance. Cross-analysis of RNA-seq and ATAC-seq data suggested that GLUT3 might be a downstream target gene of SIRT7. Subsequent investigations demonstrated that SIRT7 directly interacts with the enhancer region of GLUT3 to desuccinylate H3K122. Our group's another study revealed that GLUT3 can transport gemcitabine in breast cancer cells. Here, we found GLUT3 KD reduces the sensitivity of PC cells to gemcitabine, and SIRT7 KD-associated gemcitabine-sensitizing could be reversed by GLUT3 KD. While fasting mimicking induced upregulation of SIRT7 expression in PC cells, knocking down SIRT7 enhanced sensitivity to gemcitabine through upregulating GLUT3 expression. We further confirmed the effect of SIRT7 deficiency on the sensitivity of gemcitabine under fasting conditions using a mouse xenograft model. In summary, our study demonstrates that SIRT7 can regulate GLUT3 expression by binding to its enhancer and altering H3K122 succinylation levels, thus affecting gemcitabine sensitivity in PC cells. Additionally, combining SIRT7 knockdown with fasting may improve the efficacy of gemcitabine. This unveils a novel mechanism by which SIRT7 influences gemcitabine sensitivity in PC and offer innovative strategies for clinical combination therapy with gemcitabine.

BAG6 restricts pancreatic cancer progression by suppressing the release of IL33-presenting extracellular vesicles and the activation of mast cells

Recent studies reveal a critical role of tumor cell-released extracellular vesicles (EVs) in pancreatic cancer (PC) progression. However, driver genes that direct EV function, the EV-recipient cells, and their cellular response to EV uptake remain to be identified. Therefore, we studied the role of Bcl-2-associated-anthanogene 6 (BAG6), a regulator of EV biogenesis for cancer progression. We used a Cre recombinase/LoxP-based reporter system in combination with single-cell RNA sequencing to monitor in vivo EV uptake and tumor microenvironment (TME) changes in mouse models for pancreatic ductal adenocarcinoma (PDAC) in a Bag6 pro- or deficient background. In vivo data were validated using mouse and human organoids and patient samples. Our data demonstrated that Bag6-deficient subcutaneous and orthotopic PDAC tumors accelerated tumor growth dependent on EV release. Mechanistically, this was attributed to mast cell (MC) activation via EV-associated IL33. Activated MCs promoted tumor cell proliferation and altered the composition of the TME affecting fibroblast polarization and immune cell infiltration. Tumor cell proliferation and fibroblast polarization were mediated via the MC secretome containing high levels of PDGF and CD73. Patients with high BAG6 gene expression and high protein plasma level have a longer overall survival indicating clinical relevance. The current study revealed a so far unknown tumor-suppressing activity of BAG6 in PDAC. Bag6-deficiency allowed the release of EV-associated IL33 which modulate the TME via MC activation promoting aggressive tumor growth. MC depletion using imatinib diminished tumor growth providing a scientific rationale to consider imatinib for patients stratified with low BAG6 expression and high MC infiltration. EVs derived from BAG6-deficient pancreatic cancer cells induce MC activation via IL33/Il1rl1. The secretome of activated MCs induces tumor proliferation and changes in the TME, particularly shifting fibroblasts into an inflammatory cancer-associated fibroblast (iCAF) phenotype. Blocking EVs or depleting MCs restricts tumor growth.

Intratumoral Microbiota: Metabolic Influences and Biomarker Potential in Gastrointestinal Cancer

Gastrointestinal (GI) cancers impose a substantial global health burden, highlighting the necessity for deeper understanding of their intricate pathogenesis and treatment strategies. This review explores the interplay between intratumoral microbiota, tumor metabolism, and major types of GI cancers (including esophageal, gastric, liver, pancreatic, and colorectal cancers), summarizing recent studies and elucidating their clinical implications and future directions. Recent research revealed altered microbial signatures within GI tumors, impacting tumor progression, immune responses, and treatment outcomes. Dysbiosis-induced alterations in tumor metabolism, including glycolysis, fatty acid metabolism, and amino acid metabolism, play critical roles in cancer progression and therapeutic resistance. The integration of molecular mechanisms and potential biomarkers into this understanding further enhances the prognostic significance of intratumoral microbiota composition and therapeutic opportunities targeting microbiota-mediated tumor metabolism. Despite advancements, challenges remain in understanding the dynamic interactions within the tumor microenvironment (TME). Future research directions, including advanced omics technologies and prospective clinical studies, offer promising avenues for precision oncology and personalized treatment interventions in GI cancer. Overall, integrating microbiota-based approaches and molecular biomarkers into GI cancer management holds promise for improving patient outcomes and survival.

A Novel Pancreatic Cancer Hypoxia Status Related Gene Signature for Prognosis and Therapeutic Responses

Pancreatic cancer (PAC) is a highly fatal and aggressive type of cancer. Hypoxia is a common feature of PAC. The aim of this study was to develop a hypoxia status-related prognostic model for predicting the survival outcomes in PAC. The data sets of PAC from The Cancer Genome Atlas and the International Cancer Genome Consortium were used to construct and validate the signature. A 6 hypoxia status-related differential expression genes prognostic model for predicting the survival outcomes was established. The Kaplan-Meier analysis and Received operating characteristic curve indicated the good performance of the signature at predicting overall survival. Univariate and Multivariate Cox regression revealed that the signature was an independent prognostic factor in PAC. Weighted Gene Co-expression Network Analysis and immune infiltration analysis indicated that Immune-related pathways and immune cell infiltration was mostly enriched in the low-risk group, which presented a better prognosis. We also evaluated the predictive of the signature for immunotherapy and chemoradiotherapy. Risk gene LY6D may be a potential prognostic predictor of PAC. This model can be used as an independent prognostic factor for predicting clinical outcomes and a possible classifier for response to chemotherapy.

CCK Receptor Inhibition Reduces Pancreatic Tumor Fibrosis and Promotes Nanoparticle Delivery

The poor prognosis for pancreatic ductal adenocarcinoma (PDAC) patients is due in part to the highly fibrotic nature of the tumors that impedes delivery of therapeutics, including nanoparticles (NPs). Our prior studies demonstrated that proglumide, a cholecystokinin receptor (CCKR) antagonist, reduced fibrosis pervading PanIN lesions in mice. Here, we further detail how the reduced fibrosis elicited by proglumide achieves the normalization of the desmoplastic tumor microenvironment (TME) and improves nanoparticle uptake. One week following the orthotopic injection of PDAC cells, mice were randomized to normal or proglumide-treated water for 3-6 weeks. Tumors were analyzed ex vivo for fibrosis, vascularity, stellate cell activation, vascular patency, and nanoparticle distribution. The histological staining and three-dimensional imaging of tumors each indicated a reduction in stromal collagen in proglumide-treated mice. Proglumide treatment increased tumor vascularity and decreased the activation of cancer-associated fibroblasts (CAFs). Additionally, PANC-1 cells with the shRNA-mediated knockdown of the CCK2 receptor showed an even greater reduction in collagen, indicating the CCK2 receptors on tumor cells contribute to the desmoplastic TME. Proglumide-mediated reduction in fibrosis also led to functional changes in the TME as evidenced by the enhanced intra-tumoral distribution of small (<12 nm) Rhodamine-loaded nanoparticles. The documented in vivo, tumor cell-intrinsic anti-fibrotic effects of CCK2R blockade in both an immunocompetent syngeneic murine PDAC model as well as a human PDAC xenograft model demonstrates that CCK2R antagonists, such as proglumide, can improve the delivery of nano-encapsulated therapeutics or imaging agents to pancreatic tumors.

Impact of intratumoral microbiome on tumor immunity and prognosis in human pancreatic ductal adenocarcinoma

BACKGROUND

Recent evidence suggests that the presence of microbiome within human pancreatic ductal adenocarcinoma (PDAC) tissue potentially influences cancer progression and prognosis. However, the significance of tumor-resident microbiome remains unclear. We aimed to elucidate the impact of intratumoral bacteria on the pathophysiology and prognosis of human PDAC.

METHODS

The presence of intratumoral bacteria was assessed in 162 surgically resected PDACs using quantitative polymerase chain reaction (qPCR) and in situ hybridization (ISH) targeting 16S rRNA. The intratumoral microbiome was explored by 16S metagenome sequencing using DNA extracted from formalin-fixed paraffin-embedded tissues. The profile of intratumoral bacteria was compared with clinical information, pathological findings including tumor-infiltrating T cells, tumor-associated macrophage, fibrosis, and alterations in four main driver genes (KRAS, TP53, CDKN2A/p16, SMAD4) in tumor genomes.

RESULTS

The presence of intratumoral bacteria was confirmed in 52 tumors (32%) using both qPCR and ISH. The 16S metagenome sequencing revealed characteristic bacterial profiles within these tumors, including phyla such as Proteobacteria and Firmicutes. Comparison of bacterial profiles between cases with good and poor prognosis revealed a significant positive correlation between a shorter survival time and the presence of anaerobic bacteria such as Bacteroides, Lactobacillus, and Peptoniphilus. The abundance of these bacteria was correlated with a decrease in the number of tumor-infiltrating T cells positive for CD4, CD8, and CD45RO.

CONCLUSIONS

Intratumoral infection of anaerobic bacteria such as Bacteroides, Lactobacillus, and Peptoniphilus is correlated with the suppressed anti-PDAC immunity and poor prognosis.

Cancer-associated fibroblasts promote stemness maintenance and gemcitabine resistance via HIF-1α/miR-21 axis under hypoxic conditions in pancreatic cancer

Gemcitabine (GEM) resistance affects chemotherapy efficacy of pancreatic cancer (PC). Cancer-associated fibroblasts (CAFs) possess the ability of regulating chemoresistance. This study probed the mechanism of hypoxia-treated CAFs regulating cell stemness and GEM resistance in PC. Miapaca-2/SW1990 were co-cultured with PC-derived CAFs under normoxic/hypoxic conditions. Cell viability/self-renewal ability was determined by MTT/sphere formation assays, respectively. Protein levels of CD44, CD133, Oct4, and Sox2 were determined by western blot. GEM tumoricidal assay was performed. PC cell GEM resistance was evaluated by MTT assay. CAFs were cultured at normoxia/hypoxia. HIF-1α and miR-21 expression levels were assessed by RT-qPCR and western blot, with their binding sites and binding relationship predicted and verified. CAF-extracellular vesicles (EVs) were incubated with Miapaca-2 cells. The RAS/AKT/ERK pathway activation was detected by western blot. PC xenograft models were established and treated with hypoxic CAF-EVs and GEM. CAFs and PC cell co-culture increased cell stemness maintenance, GEM resistance, cell viability, stem cell sphere number, and protein levels of CD44, CD133, Oct4, and Sox2, and weakened GEM tumoricidal ability to PC cells, with the effects further enhanced by hypoxia. Hypoxia induced HIF-1α and miR-21 overexpression in CAFs. Hypoxia promoted CAFs to secrete high-level miR-21 EVs via the HIF-1α/miR-21 axis, and activated the miR-21/RAS/AKT/ERK pathway. CAF-EVs promoted GEM resistance in PC via the miR-21/RAS/ATK/ERK pathway in vivo. Hypoxia promoted CAFs to secrete high-level miR-21 EVs through the HIF-1α/miR-21 axis, and activated the miR-21/RAS/AKT/ERK pathway via EVs to trigger stemness maintenance and GEM resistance in PC.

Metabolomic Investigations into Hypoxia-Mediated Metabolic Reprogramming of Pancreatic Cancer Cells

Hypoxia is a crucial microenvironmental factor that defines tumor cell growth and aggressiveness. Cancer cells adapt to hypoxia by altering their metabolism. These alterations impact various cellular and physiological functions, including energy metabolism, vascularization, invasion and metastasis, genetic instability, cell immortalization, stem cell maintenance, and resistance to chemotherapy (Li et al. Technol Cancer Res Treat 20:15330338211036304, 2021). Hypoxia-inducible factor-1α (HIF-1α) is known to be a critical regulator of glycolysis that directly regulates the transcription of multiple key enzymes of the glycolysis pathway. Moreover, HIF-1α stabilization can be directly modulated by TCA-derived metabolites, including 2-ketoglutarate and succinate (Infantino et al, Int J Mol Sci 22(22), https://doi.org/10.3390/ijms22115703 , 2021). Overall, the molecular mechanisms underlying the adaptation of cellular metabolism to hypoxia impact the metabolic phenotype of cancer cells. Such adaptations include increased glucose uptake, increased lactate production, and increased levels of other metabolites that stabilize HIF-1α, leading to a vicious circle of hypoxia-induced tumor growth.

Establishment of a Prognostic Model for Pancreatic Cancer Based on Hypoxia-Related Genes

OBJECTIVES

Pancreatic cancer presents a formidable challenge with its aggressive nature and dismal prognosis, often hampered by elusive early symptoms. The tumor microenvironment (TME) emerges as a pivotal player in pancreatic cancer progression and treatment responses, characterized notably by hypoxia and immunosuppression. In this study, we aimed to identify hypoxia-related genes and develop a prognostic model for pancreatic cancer leveraging these genes.

METHODS

Through analysis of gene expression data from The Cancer Genome Atlas (TCGA) and subsequent GO/KEGG enrichment analysis, hypoxia-related pathways were identified. We constructed a prognostic model using lasso regression and validated it using an independent dataset.

RESULTS

Our results showed that expression levels of PLAU, SLC2A1, and CA9 exhibited significant associations with prognosis in pancreatic cancer. The prognostic model, built upon these genes, displayed robust predictive accuracy and was validated in an independent dataset. Furthermore, we found a correlation between the risk score of the prognostic model and clinical parameters of pancreatic cancer patients. At the same time, we also explored the relationship between the established hypoxia-related prognostic model and the immune microenvironment at the single-cell level. RT-qPCR results showed notable differences in the expression of hypoxia pathway-related genes between normal PANC-1 and hypoxic-treated PANC-1 cells.

CONCLUSION

Our study provides insights into the role of the hypoxic microenvironment in pancreatic cancer and offers a promising prognostic tool for clinical application.

GATA6-AS1 suppresses epithelial-mesenchymal transition of pancreatic cancer under hypoxia through regulating SNAI1 mRNA stability

Pancreatic ductal adenocarcinoma (PDAC) is characterized by a hypoxic microenvironment, a high rate of heterogeneity as well as a high likelihood of recurrence. Mounting evidence has affirmed that long non-coding RNAs (lncRNAs) participate in the carcinogenesis of PDAC cells. In this study, we revealed significantly decreased expression of GATA6-AS1 in PDAC based on the GEO dataset and our cohorts, and showed that low GATA6-AS1 expression was linked to unfavorable clinicopathologic characteristics as well as a poor prognosis. Gain- and loss-of-function studies demonstrated that GATA6-AS1 suppressed the proliferation, invasion, migration, and epithelial-mesenchymal transition (EMT) process of PDAC cells under hypoxia. In vivo data confirm the suppressive roles of GATA6-AS1/SNAI1 in tumor growth and lung metastasis of PDAC. Mechanistically, hypoxia-driven E26 transformation-specific sequence-1 (ETS1), as an upstream modulatory mechanism, was essential for the downregulation of GATA6-AS1 in PDAC cells. GATA6-AS1 inhibited the expression of fat mass and obesity-associated protein (FTO), an N6-methyladenosine (m6A) eraser, and repressed SNAI1 mRNA stability in an m6A-dependent manner. Our data suggested that GATA6-AS1 can inhibit PDAC cell proliferation, invasion, migration, EMT process and metastasis under hypoxia, and disrupting the GATA6-AS1/FTO/SNAI1 axis might be a viable therapeutic approach for refractory hypoxic pancreatic cancers.

CA9 and PRELID2; hypoxia-responsive potential therapeutic targets for pancreatic ductal adenocarcinoma as per bioinformatics analyses

A strong hypoxic environment has been observed in pancreatic ductal adenocarcinoma (PDAC) cells, which contributes to drug resistance, tumor progression, and metastasis. Therefore, we performed bioinformatics analyses to investigate potential targets for the treatment of PDAC. To identify potential genes as effective PDAC treatment targets, we selected all genes whose expression level was related to worse overall survival (OS) in The Cancer Genome Atlas (TCGA) database and selected only the genes that matched with the genes upregulated due to hypoxia in pancreatic cancer cells in the dataset obtained from the Gene Expression Omnibus (GEO) database. Although the extracted 107 hypoxia-responsive genes included the genes that were slightly enriched in angiogenic factors, TCGA data analysis revealed that the expression level of endothelial cell (EC) markers did not affect OS. Finally, we selected CA9 and PRELID2 as potential targets for PDAC treatment and elucidated that a CA9 inhibitor, U-104, suppressed pancreatic cancer cell growth more effectively than 5-fluorouracil (5-FU) and PRELID2 siRNA treatment suppressed the cell growth stronger than CA9 siRNA treatment. Thus, we elucidated that specific inhibition of PRELID2 as well as CA9, extracted via exhaustive bioinformatic analyses of clinical datasets, could be a more effective strategy for PDAC treatment.

Oncolytic adenovirus as pancreatic cancer-targeted therapy: Where do we go from here?

Pancreatic cancer remains one of the deadliest cancers with extremely high mortality rate, and the number of cases is expected to steadily increase with time. Pancreatic cancer is refractory to conventional cancer treatment options, like chemotherapy and radiotherapy, and commercialized immunotherapeutics, owing to its immunosuppressive and desmoplastic phenotype. Due to these reasons, development of an innovative treatment option that can overcome these challenges posed by the pancreatic tumor microenvironment (TME) is in an urgent need. The present review aims to summarize the evolution of oncolytic adenovirus (oAd) engineering and usage as therapeutics (either monotherapy or combination therapy) over the last decade to overcome these hurdles to instigate a potent antitumor effect against desmoplastic and immunosuppressive pancreatic cancer.

Pancreatic Ductal Adenocarcinoma: The Characteristics of Contrast-Enhanced Ultrasound Are Correlated with the Hypoxic Microenvironment

A hypoxic microenvironment is associated with an increased risk of metastasis, treatment resistance and poor prognosis of pancreatic ductal adenocarcinoma (PDAC). This study aimed to identify contrast-enhanced ultrasound (CEUS) characteristics that could predict the hypoxic microenvironment of PDAC. A total of 102 patients with surgically resected PDAC who underwent CEUS were included. CEUS qualitative and quantitative characteristics were analyzed. The expression of hypoxia-inducible factor-1α (HIF-1) and glucose transporter-1 (GLUT1) were demonstrated by immunohistochemistry. The associations between CEUS characteristics and the HIF-1α and GLUT1 expression of PDACs were evaluated. We found that HIF-1α-high PDACs and GLUT1-high PDACs had a larger tumor size and were more prone to lymph node metastasis. There was a significant positive linear correlation between the expression of HIF-1α and GLUT1. CEUS qualitative characteristics including completeness of enhancement and peak enhancement degree (PED) were related to the expression of HIF-1α and GLUT1. A logistic regression analysis showed that tumor size, lymph node metastasis, incomplete enhancement and iso-enhancement of PED were independent predictors for HIF-1α-high PDACs and GLUT1-high PDACs. As for quantitative characteristics, HIF-1α-high PDACs and GLUT1-high PDACs showed higher peak enhancement (PE) and wash-in rate (WIR). CEUS can effectively reflect the hypoxia microenvironment of PDAC, which may become a noninvasive imaging biomarker for prognosis prediction and individualized treatment.

DUSP2 recruits CSNK2A1 to suppress AKT1-mediated apoptosis resistance under hypoxic microenvironment in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is characterized by hypoxic tumor microenvironment (TME), which aids tumor progression, drug resistance, and immune evasion. Dual-specificity phosphatase 2 (DUSP2), a member of the mitogen-activated protein kinase phosphatase family, regulates pancreatic cancer metastasis. However, its role in the hypoxic TME in PDAC remains unknown. We explored the role of DUSP2 by simulating the hypoxic TME. DUSP2 significantly promoted apoptosis in PDAC both in vitro and in vivo, mainly through AKT1 rather than ERK1/2. Mechanistically, DUSP2 competed with AKT1 to bind to casein kinase 2 alpha 1 (CSNK2A1) and inhibited the phosphorylation of AKT1, which plays a crucial role in apoptosis resistance. Interestingly, aberrant activation of AKT1 resulted in an increase in the ubiquitin E3 ligase tripartite motif-containing 21 (TRIM21), which binds to and mediates the ubiquitination-dependent proteasomal degradation of DUSP2. Overall, we identified CSNK2A1 as a novel binding partner of DUSP2 that promotes PDAC apoptosis through CSN2KA1/AKT1 in an ERK1/2-independent manner. Activation of AKT1 also mediated proteasomal degradation of DUSP2 via the AKT1/TRIM21 positive feedback loop. We propose increasing the level of DUSP2 as a potential therapeutic strategy for PDAC.

Re-Shaping the Pancreatic Cancer Tumor Microenvironment: A New Role for the Metastasis Suppressor NDRG1

Pancreatic cancer (PaC) is a highly aggressive disease, with poor response to current treatments and 5-year survival rates of 10-15%. PaC progression is facilitated by its interaction with the complex and multifaceted tumor microenvironment (TME). In the TME, cancer cells and surrounding stromal cells constantly communicate with each other via the secretion and uptake of factors including cytokines, chemokines, growth factors, metabolites, and extracellular vesicles (EVs), reshaping the landscape of PaC. Recent studies demonstrated that the metastasis suppressor N-myc downstream regulated 1 (NDRG1) not only inhibits oncogenic signaling pathways in PaC cells but also alters the communication between PaC cells and the surrounding stroma. In fact, NDRG1 was found to influence the secretome of PaC cells, alter cancer cell metabolism, and interfere with intracellular trafficking and intercellular communication between PaC cells and surrounding fibroblasts. This review will present recent advancements in understanding the role of NDRG1 in PaC progression, with a focus on how this molecule influences PaC-stroma communication and its potential for re-shaping the PaC TME.

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

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

m6A methylation regulates hypoxia-induced pancreatic cancer glycolytic metabolism through ALKBH5-HDAC4-HIF1α positive feedback loop

Pancreatic cancer (PC) is the most hypoxic cancer type among solid tumors. The dynamic changes of RNA N6-methyl-adenosine (m6A) contribute to tumor cells adaption to hypoxic microenvironmental. However, the regulatory mechanisms of hypoxia response in PC remains elusive. Here, we reported that the m6A demethylase ALKBH5 mediated a decrease of total mRNA m6A modification during hypoxia. Subsequently, methylated RNA immunoprecipitation sequencing (MeRIP-seq) combined with RNA sequencing (RNA-seq) revealed transcriptome-wide gene expression alteration and identified histone deacetylase type 4 (HDAC4) as a key target gene of m6A modification under hypoxic conditionds. Mechanistically, m6A methylation recognized by m6A reader-YTHDF2 enhanced the stability of HDAC4, and then promoted glycolytic metabolism and migration of PC cells. Our assays also demonstrated that hypoxia-induced HDAC4 enhanced HIF1a protein stability, and overexpressed HIF1a promoted transcription of ALKBH5 in hypoxic pancreatic cancer cells. Together, these results found a ALKBH5/HDAC4/HIF1α positive feedback loop for cellular response to hypoxia in pancreatic cancer. Our studies uncover the crosstalk between histone acetylation and RNA methylation modification on layer of epigenetic regulation.

Correlation between hypoxia and HGF/c-MET expression in the management of pancreatic cancer

Pancreatic cancer (PC) is very deadly and difficult to treat. The presence of hypoxia has been shown to increase the probability of cancer developing and spreading. Pancreatic ductal adenocarcinoma (PDAC/PC) has traditionally viewed a highly lethal form of cancer due to its high occurrence of early metastases. Desmoplasia/stroma is often thick and collagenous, with pancreatic stellate cells as the primary source (PSCs). Cancer cells and other stromal cells interact with PSCs, promoting disease development. The hepatocyte growth factor (HGF)/c-MET pathway have been proposed as a growth factor mechanism mediating this interaction. Human growth factor (HGF) is secreted by pancreatic stellate cells (PSCs), and its receptor, c-MET, is generated by pancreatic cancer cells and endothelial cells. Hypoxia is frequent in malignant tumors, particularly pancreatic (PC). Hypoxia results from limitless tumor development and promotes survival, progression, and invasion. Hypoxic is becoming a critical driver and therapeutic target of pancreatic cancer as its hypoxia microenvironment is defined. Recent breakthroughs in cancer biology show that hypoxia promotes tumor proliferation, aggressiveness, and therapeutic resistance. Hypoxia-inducible factors (HIFs) stabilize hypoxia signaling. Hypoxia cMet is a key component of pancreatic tumor microenvironments, which also have a fibrotic response, that hypoxia, promotes and modulates. c-Met is a tyrosine-protein kinase. As describe it simply, the MET gene in humans' codes for a protein called hepatocyte growth factor receptor (HGFR). Most cancerous tumors and pancreatic cancer in particular, suffer from a lack of oxygen (PC). Due to unrestrained tumor development, hypoxia develops, actively contributing to tumor survival, progression, and invasion. As the processes by which hypoxia signaling promotes invasion and metastasis become clear, c-MET has emerged as an important determinant of pancreatic cancer malignancy and a potential pharmacological target. This manuscript provides the most current findings on the role of hypoxia and HGF/c-MET expression in the treatment of pancreatic cancer.

Prediction of Survival and Tumor Microenvironment Infiltration Based on Pyroptosis-Related lncRNAs in Pancreatic Cancer

Pancreatic cancer (PC) is a fatal tumor with high mortality. Pyroptosis plays a tumor suppressor role as a novel cell death. However, the influences of the pyroptosis-related lncRNAs (PRlncRNAs) on the prognosis and tumor microenvironment (TME) infiltration have not been fully studied in PC. Using coexpression analysis and univariate Cox regression analysis, we identified seventeen prognostic PRlncRNAs from The Cancer Genome Atlas (TCGA) dataset, which were all expressed differently in normal and tumor samples. A seven-PRlncRNA risk signature was constructed and validated using the least absolute shrinkage and selection operator (LASSO) regression. Furthermore, we verified its independence and created a nomogram to validate the clinical viability of the risk signature. We then identified its relationship with clinical factors and evaluated its values in TME infiltration, functional enrichment, tumor mutation, and therapeutic responses in PC. Lower ImmuneScore, ESTIMATEScore, and advanced tumor stage were connected with high-risk score. The low-risk group was characterized by better OS, elevated immune activation, and higher susceptibility of pazopanib and sunitinib. The high-risk group possessed a worse immune infiltration and poor survival, with higher tumor mutations and lapatinib and paclitaxel that may be better choices in this group. In conclusion, we developed an original seven-PRlncRNA risk signature to predict prognosis, TME infiltration, tumor mutation, and therapeutic options for PC patients.

Hypoxia-Induced miR-210 Promotes Endothelial Cell Permeability and Angiogenesis via Exosomes in Pancreatic Ductal Adenocarcinoma

BACKGROUND

Exosomes have been proven to play important diagnostic, regulatory, or communication roles in tumorigenesis, tumor progression, or metastasis; in recent studies, lots of molecules, including miRNAs, were found to be aberrantly expressed in tumor exosomes and were correlated with tumor development. However, studies about the expression, relationship, or control mechanisms of miRNAs in exosomes in pancreatic ductal adenocarcinoma (PDAC) are scarce and urgently needed. The aim of this article was to identify and investigate abnormally expressed miRNAs in PDAC exosomes in vivo and in vitro.

METHODS

Microarray studies were used to detect aberrantly expressed miRNAs in PDAC exosomes, and miR-210 expression in cells or exosomes was further analyzed by qRT-PCR. Bioinformatics analyses, dual-luciferase assays, WB, and other assays were utilized to explore the miRNA molecular mechanisms. The living cell coculture model and immunofluorescence analysis were employed to image the communication between PDAC cells and endothelial cells. Other biological experiments in the study include a real-time intravital imaging system, EdU, transwell, xenograft models, and so on.

RESULTS

miR-210 is significantly expressed in PDAC exosomes and malignant cells. High miR-210 significantly facilitated tumor angiogenesis, cell invasion, and proliferation in PDAC cells. Further mechanistic detection revealed that miR-210 negatively regulated EFNA3 expression and participated in the PI3K/AKT/VEGFA or Wnt/Β-catenin/RHOA pathways, thus promoting tumor angiogenesis and cellular permeability. PDAC cells promote endothelial angiogenesis or permeability via miR-210 transmission by tumor exosomes. Exosomal miR-210 promotes PDAC progression in vivo. Further detection of PDAC plasma exosomal miR-210 suggests that exosomal miR-210 expression was high and significantly associated with vascular invasion and TNM stage and was an independent risk factor for PDAC overall survival.

CONCLUSIONS

PDAC cell-secreted exosomes could promote angiogenesis and cellular permeability of neighboring endothelial angiogenesis or permeability via miR-210 transmission. Exosomal miR-210 may play important roles in tumor biology and may be a useful prognostic marker in PDAC.

ITGA2 overexpression inhibits DNA repair and confers sensitivity to radiotherapies in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a dismal disease with a 5-year survival rate of less than 10%, despite the recent advances in chemoradiotherapy. The sensitivity of the PDAC patients to chemoradiotherapy varies widely, especially to radiotherapy, suggesting the need for more elucidation of the underlying mechanisms. In this study, a novel function of the nuclear ITGA2, the alpha subunit of transmembrane collagen receptor integrin alpha-2/beta-1, regulating the DNA damage response (DDR), was identified. First, analyzing The Cancer Genome Atlas (TCGA) PDAC data set indicated that the expression status of ITGA2 was negatively correlated with the genome stability parameters. The study further demonstrated that ITGA2 specially inhibited the activity of the non-homologous end joining (NHEJ) pathway and conferred the sensitivity to radiotherapy in PDAC by restraining the recruitment of DNA-dependent protein kinase catalytic subunit (DNA-PKcs) to Ku70/80 heterodimer during DDR. Considering the overexpression of ITGA2 and its associated with the poor prognosis of PDAC patients, this study suggested that the ITGA2 expression status could be used as an indicator for radiotherapy and DNA damage reagents, and the radiotherapy in combination with the overexpression of ITGA2 might be a viable treatment strategy for the PDAC patients.

Harnessing redox signaling to overcome therapeutic-resistant cancer dormancy

Dormancy occurs when cells preserve viability but stop proliferating, which is considered an important cause of tumor relapse, which may occur many years after clinical remission. Since the life cycle of dormant cancer cells is affected by both intracellular and extracellular factors, gene mutation or epigenetic regulation of tumor cells may not fully explain the mechanisms involved. Recent studies have indicated that redox signaling regulates the formation, maintenance, and reactivation of dormant cancer cells by modulating intracellular signaling pathways and the extracellular environment, which provides a molecular explanation for the life cycle of dormant tumor cells. Indeed, redox signaling regulates the onset of dormancy by balancing the intrinsic pathways, the extrinsic environment, and the response to therapy. In addition, redox signaling sustains dormancy by managing stress homeostasis, maintaining stemness and immunogenic equilibrium. However, studies on dormancy reactivation are still limited, partly explained by redox-mediated activation of lipid metabolism and the transition from the tumor microenvironment to inflammation. Encouragingly, several drug combination strategies based on redox biology are currently under clinical evaluation. Continuing to gain an in-depth understanding of redox regulation and develop specific methods targeting redox modification holds the promise to accelerate the development of strategies to treat dormant tumors and benefit cancer patients.

Resistance to Gemcitabine in Pancreatic Ductal Adenocarcinoma: A Physiopathologic and Pharmacologic Review

Pancreatic ductal adenocarcinoma (PDAC) is a very aggressive tumor with a poor prognosis and inadequate response to treatment. Many factors contribute to this therapeutic failure: lack of symptoms until the tumor reaches an advanced stage, leading to late diagnosis; early lymphatic and hematic spread; advanced age of patients; important development of a pro-tumoral and hyperfibrotic stroma; high genetic and metabolic heterogeneity; poor vascular supply; a highly acidic matrix; extreme hypoxia; and early development of resistance to the available therapeutic options. In most cases, the disease is silent for a long time, andwhen it does become symptomatic, it is too late for ablative surgery; this is one of the major reasons explaining the short survival associated with the disease. Even when surgery is possible, relapsesare frequent, andthe causes of this devastating picture are the low efficacy ofand early resistance to all known chemotherapeutic treatments. Thus, it is imperative to analyze the roots of this resistance in order to improve the benefits of therapy. PDAC chemoresistance is the final product of different, but to some extent, interconnected factors. Surgery, being the most adequate treatment for pancreatic cancer and the only one that in a few selected cases can achieve longer survival, is only possible in less than 20% of patients. Thus, the treatment burden relies on chemotherapy in mostcases. While the FOLFIRINOX scheme has a slightly longer overall survival, it also produces many more adverse eventsso that gemcitabine is still considered the first choice for treatment, especially in combination with other compounds/agents. This review discusses the multiple causes of gemcitabine resistance in PDAC.

Emerging Role for 7T MRI and Metabolic Imaging for Pancreatic and Liver Cancer

Advances in magnet technologies have led to next generation 7T magnetic resonance scanners which can fit in the footprint and price point of conventional hospital scanners (1.5−3T). It is therefore worth asking if there is a role for 7T magnetic resonance imaging and spectroscopy for the treatment of solid tumor cancers. Herein, we survey the medical literature to evaluate the unmet clinical needs for patients with pancreatic and hepatic cancer, and the potential of ultra-high field proton imaging and phosphorus spectroscopy to fulfil those needs. We draw on clinical literature, preclinical data, nuclear magnetic resonance spectroscopic data of human derived samples, and the efforts to date with 7T imaging and phosphorus spectroscopy. At 7T, the imaging capabilities approach histological resolution. The spectral and spatial resolution enhancements at high field for phospholipid spectroscopy have the potential to reduce the number of exploratory surgeries due to tumor boundaries undefined at conventional field strengths. Phosphorus metabolic imaging at 7T magnetic field strength, is already a mainstay in preclinical models for molecular phenotyping, energetic status evaluation, dosimetry, and assessing treatment response for both pancreatic and liver cancers. Metabolic imaging of primary tumors and lymph nodes may provide powerful metrics to aid staging and treatment response. As tumor tissues contain extreme levels of phospholipid metabolites compared to the background signal, even spectroscopic volumes containing less than 50% tumor can be detected and/or monitored. Phosphorus spectroscopy allows non-invasive pH measurements, indicating hypoxia, as a predictor of patients likely to recur. We conclude that 7T multiparametric approaches that include metabolic imaging with phosphorus spectroscopy have the potential to meet the unmet needs of non-invasive location-specific treatment monitoring, lymph node staging, and the reduction in unnecessary surgeries for patients undergoing resections for pancreatic cancer. There is also potential for the use of 7T phosphorous spectra for the phenotyping of tumor subtypes and even early diagnosis (<2 mL). Whether or not 7T can be used for all patients within the next decade, the technology is likely to speed up the translation of new therapeutics.

A review on the design, synthesis, and structure-activity relationships of benzothiazole derivatives against hypoxic tumors

There has been a growing body of studies on benzothiazoles and benzothiazole derivatives as strong and effective antitumor agents against lung, liver, pancreas, breast, and brain tumors. Due to highly proliferative nature of the tumor cells, the oxygen levels get lower than that of a normal tissue in the tumor microenvironment. This situation is called as hypoxia and has been associated with increased ability for carcinogenesis. For the drug design and development strategies, hypoxic nature of the tumor tissues has been exploited more aggressively. Hypoxia itself acts as a signal initiating system to activate the pathways that eventually lead to the spread of the tumor cells into the different tissues, increases the rate of DNA damage and eventually ends up with more mutation levels that may increase the drug resistance. As one of the major mediators of hypoxic response, hypoxia inducible factors (HIFs) has been shown to activate to angiogenesis, metastasis, apoptosis resistance, and many other protumorigenic responses in cancer development. In the current review, we will be discussing the design, synthesis and structure-activity relationships of benzothiazole derivatives against hypoxic tumors such lung, liver, pancreas, breast and brain as potential anticancer drug candidates. The focus points of the study will be the biology behind carcinogenesis and how hypoxia contributes to the process, recent studies on benzothiazole and its derivatives as anti-cancer agents against hypoxic cancers, conclusions and future perspectives. We believe that this review will be useful for the researchers in the field of drug design during their studies to generate novel benzothiazole-containing hybrids against hypoxic tumors with higher efficacies.

Recent advances in targeted drug delivery for the treatment of pancreatic ductal adenocarcinoma

INTRODUCTION

Pancreatic ductal adenocarcinoma (PDAC) has become a serious health problem with high impact worldwide. The heterogeneity of PDAC makes it difficult to apply drug delivery systems (DDS) used in other cancer models, for example, the poorly developed vascular system makes anti-angiogenic therapy ineffective. Due to its various malignant pathological changes, drug delivery against PDAC is a matter of urgent concern. Based on this situation, various drug delivery strategies specially designed for PDAC have been generated.

AREAS COVERED

This review will briefly describe how delivery systems can be designed through nanotechnology and formulation science. Most research focused on penetrating the stromal barrier, exploiting and alleviating the hypoxic microenvironment, targeting immune cells, or designing vaccines, and combination therapies. This review will summarize the ways to reverse the malignant pathological features of PDAC and hopefully provide ideas for subsequent studies.

EXPERT OPINION

Drug delivery systems designed to achieve penetrating functions or to alleviate hypoxia and activate immunity have achieved good therapeutic results in animal models in several studies. In future studies, there is a need to deliver PDAC therapeutics in a more precise manner, or the use of drug carriers for multiple functions simultaneously, are potential therapeutic strategy.

Neoadjuvant Treatment for Resectable and Borderline Resectable Pancreatic Cancer: Chemotherapy or Chemoradiotherapy?

Worldwide, there is a shifting paradigm from immediate surgery with adjuvant treatment to a neoadjuvant approach for patients with resectable or borderline resectable pancreatic cancer (RPC or BRPC). Comparison of neoadjuvant and adjuvant studies is extremely difficult because of a great difference in patient selection. The evidence from randomized studies shows that overall survival by intention-to-treat improves after neoadjuvant gemcitabine-based chemoradiotherapy or chemotherapy (various regimens), as compared to immediate surgery followed by adjuvant chemotherapy. Radiotherapy appears to play an important role in mediating locoregional effects. Yet, since more effective chemotherapy regimens are currently available, in particular FOLFIRINOX and Gemcitabine/Nab-paclitaxel, these chemotherapy regimens should be investigated in future randomized trials combined with (stereotactic) radiotherapy to further improve outcomes of RPC and BRPC.

Immunofluorescence-Based Method to Assess Cancer Biomarker in the Hypoxic Region of the Tumor

The development of novel imaging technologies allows the analysis of the expression and spatial distribution of multiple markers simultaneously, providing necessary information about a cellular identity and the surrounding microenvironment. This chapter describes the utilization of immunofluorescence to identify such biomarkers in fixed tissue from prostate cancer (PCa) xenografts. One such marker detectable by immunofluorescence is pimonidazole, which has been utilized to locate areas of low oxygen (hypoxia). Pimonidazole, in combination with other biomarkers, could be utilized to identify "niches" in the microenvironment harboring more aggressive cells both within and outside hypoxic areas. Specifically, we describe the method to use pimonidazole for the identification of hypoxic regions in PCa xenograft tumors along with CPT1A (carnitine palmitoyltransferase 1A) expression, an indicator of β-oxidation. This approach could be useful to characterize various biomarkers in the complex hypoxic tumor microenvironment.

Tumor Microenvironment Features and Chemoresistance in Pancreatic Ductal Adenocarcinoma: Insights into Targeting Physicochemical Barriers and Metabolism as Therapeutic Approaches

Currently, the median overall survival of PDAC patients rarely exceeds 1 year and has an overall 5-year survival rate of about 9%. These numbers are anticipated to worsen in the future due to the lack of understanding of the factors involved in its strong chemoresistance. Chemotherapy remains the only treatment option for most PDAC patients; however, the available therapeutic strategies are insufficient. The factors involved in chemoresistance include the development of a desmoplastic stroma which reprograms cellular metabolism, and both contribute to an impaired response to therapy. PDAC stroma is composed of immune cells, endothelial cells, and cancer-associated fibroblasts embedded in a prominent, dense extracellular matrix associated with areas of hypoxia and acidic extracellular pH. While multiple gene mutations are involved in PDAC initiation, this desmoplastic stroma plays an important role in driving progression, metastasis, and chemoresistance. Elucidating the mechanisms underlying PDAC resistance are a prerequisite for designing novel approaches to increase patient survival. In this review, we provide an overview of the stromal features and how they contribute to the chemoresistance in PDAC treatment. By highlighting new paradigms in the role of the stromal compartment in PDAC therapy, we hope to stimulate new concepts aimed at improving patient outcomes.

Development and Verification of the Hypoxia- and Immune-Associated Prognostic Signature for Pancreatic Ductal Adenocarcinoma

We aim to construct a hypoxia- and immune-associated risk score model to predict the prognosis of patients with pancreatic ductal adenocarcinoma (PDAC). By unsupervised consensus clustering algorithms, we generate two different hypoxia clusters. Then, we screened out 682 hypoxia-associated and 528 immune-associated PDAC differentially expressed genes (DEGs) of PDAC using Pearson correlation analysis based on the Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression project (GTEx) dataset. Seven hypoxia and immune-associated signature genes (S100A16, PPP3CA, SEMA3C, PLAU, IL18, GDF11, and NR0B1) were identified to construct a risk score model using the Univariate Cox regression and the Least Absolute Shrinkage and Selection Operator (LASSO) Cox regression, which stratified patients into high- and low-risk groups and were further validated in the GEO and ICGC cohort. Patients in the low-risk group showed superior overall survival (OS) to their high-risk counterparts (p < 0.05). Moreover, it was suggested by multivariate Cox regression that our constructed hypoxia-associated and immune-associated prognosis signature might be used as the independent factor for prognosis prediction (p < 0.001). By CIBERSORT and ESTIMATE algorithms, we discovered that patients in high-risk groups had lower immune score, stromal score, and immune checkpoint expression such as PD-L1, and different immunocyte infiltration states compared with those low-risk patients. The mutation spectrum also differs between high- and low-risk groups. To sum up, our hypoxia- and immune-associated prognostic signature can be used as an approach to stratify the risk of PDAC.

Advances of Tumorigenesis, Diagnosis at Early Stage, and Cellular Immunotherapy in Gastrointestinal Malignancies

Globally, in 2018, 4.8 million new patients have a diagnosis of gastrointestinal (GI) cancers, while 3.4 million people died of such disorders. GI malignancies are tightly relevant to 26% of the world-wide cancer incidence and occupies 35% of all cancer-associated deaths. In this article, we principally investigated molecular and cellular mechanisms of tumorigenesis in five major GI cancers occurring at esophagus, stomach, liver, pancreas, and colorectal region that illustrate high morbidity in Eastern and Western countries. Moreover, through this investigation, we not only emphasize importance of the tumor microenvironment in development and treatment of malignant tumors but also identify significance of M2PK, miRNAs, ctDNAs, circRNAs, and CTCs in early detection of GI cancers, as well as systematically evaluate contribution of personalized precision medicine including cellular immunotherapy, new antigen and vaccine therapy, and oncolytic virotherapy in treatment of GI cancers.

Nitric oxide-releasing micelles with intelligent targeting for enhanced anti-tumor effect of cisplatin in hypoxia

Background

Hypoxic tumor microenvironment (TME) promotes tumor metastasis and drug resistance, leading to low efficiency of cancer chemotherapy. The development of targeted agents or multi-target therapies regulating hypoxic microenvironment is an important approach to overcome drug resistance and metastasis.

Methods

In this study, chitosan oligosaccharide (COS)-coated and sialic acid (SA) receptor-targeted nano-micelles were prepared using film dispersion method to co-deliver cisplatin (CDDP) and nitric oxide (NO) (denoted as CTP/CDDP). In addition, we explored the mechanisms by which NO reversed CDDP resistance as well as enhanced anti-metastatic efficacy in hypoxic cancer cells.

Results

Because of the different affinities of COS and SA to phenylboronic acid (PBA) under different pH regimes, CTP/CDDP micelles with intelligent targeting property increased cellular uptake of CDDP and enhanced cytotoxicity to tumors, but reduced systemic toxicity to normal organs or tissues. In addition, CTP/CDDP showed stimulus-responsive release in TME. In terms of anti-tumor mechanism, CTP/CDDP reduced CDDP efflux and inhibited epithelial-mesenchymal transition (EMT) process of tumor by down-regulating hypoxia-inducible factor-1α (HIF-1α), glutathione (GSH), multidrug resistance-associated protein 2 (MRP2) and matrix metalloproteinase 9 (MMP9) expression, thus reversing drug resistance and metastasis of hypoxic tumor cells.

Conclusions

The designed micelles significantly enhanced anti-tumor effects both in vitro and in vivo. These results suggested that CTP/CDDP represented a promising strategy to treat resistance and metastatic tumors.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-00989-z.

Hypoxia boosts aerobic glycolysis of carcinoma：a complex process for tumor development

Hypoxia, a common feature in malignant tumors, is mainly caused by insufficient oxygen supply. Hypoxia is closely related to cancer development, affecting cancer invasion and metastasis, energy metabolism and other pathological processes, and is not conducive to cancer treatment and prognosis. Tumor cells exacerbate metabolic abnormalities to adapt to the hypoxic microenvironment, especially to enhance aerobic glycolysis. Glycolysis leads to an acidic microenvironment in cancer tissues, enhancing cancer metastasis, deterioration and drug resistance. Therefore, hypoxia is a therapeutic target that cannot be ignored in cancer treatment. The adaptation of tumor cells to hypoxia is mainly regulated by hypoxia inducible factors (HIFs), and the stability of HIFs is improved under hypoxic conditions. HIFs can promote the glycolysis of tumors by regulating glycolytic enzymes, transporters, and participates in regulating the TCA (tricarboxylic acid) cycle. In addition, HIFs indirectly affect glycolysis through its interaction with non-coding RNAs. Therefore, targeting hypoxia and HIFs are important tumor therapies.

Nanoprobe-Based Magnetic Resonance Imaging of Hypoxia Predicts Responses to Radiotherapy, Immunotherapy, and Sensitizing Treatments in Pancreatic Tumors

Accurate diagnosis of tumors and predicting the therapeutic responses are highly demanded in the clinic to improve the treatment efficacy and survival rates. Since hypoxia develops in the progression of tumors and inversely correlates with prognosis and promotes resistance to radiotherapies and immunotherapies, it is a potential marker for therapeutic prediction. Therefore, effective discrimination of tumor hypoxia for predicting therapeutic outcomes is critical. Here, a magnetic resonance imaging (MRI)-based diagnosis strategy using contrast-amplifying nanoprobes that sense tumor acidosis and real-time observation of hypoxic conditions in tumors has been developed, aiming at accurate detection of pancreatic tumors and prediction of therapeutic effects. Our approach selectively probed xenograft, allograft, and transgenic spontaneous models of intractable pancreatic cancer, which lacks standardized predictive markers to identify patients who benefit most from treatments, and effectively discriminated the intratumoral hypoxia levels. By stratification of pancreatic tumors based on quantitative MR imaging of hypoxia, it enabled prediction of the responses to radiotherapy and immune checkpoint inhibitors. Moreover, the nanoprobe-based MRI could monitor hypoxia reduction by tumor normalization treatments, which permits visualizing pancreatic tumors that will respond to immune checkpoint blockade therapy, enhancing the response rate. The results demonstrate the potential of our strategy for accurate tumor diagnosis, patient stratification, and effective therapy.

Metabolic reprogramming due to hypoxia in pancreatic cancer: Implications for tumor formation, immunity, and more

Hypoxia is a common phenomenon in most malignant tumors, especially in pancreatic cancer (PC). Hypoxia is the result of unlimited tumor growth and plays an active role in promoting tumor survival, progression, and invasion. As the part of the hypoxia microenvironment in PC is gradually clarified, hypoxia is becoming a key determinant and an important therapeutic target of pancreatic cancer. To adapt to the severe hypoxia environment, cells have changed their metabolic phenotypes to maintain their survival and proliferation. Enhanced glycolysis is the most prominent feature of cancer cells' metabolic reprogramming in response to hypoxia. It provides the energy source for hypoxic cancer cells (although it provides less than oxidative phosphorylation) and produces metabolites that can be absorbed and utilized by normoxic cancer cells. In addition, the uptake of glutamine and fatty acids by hypoxic cancer cells is also increased, which is also conducive to tumor progression. Their metabolites are pooled in the hexosamine biosynthesis pathway (HBP). As a nutrition sensor, HBP, in turn, can coordinate glucose and glutamine metabolism. Its end product, UDP-GlcNAc, is the substrate of protein post-translational modification (PTM) involved in various signaling pathways supporting tumor progression. Adaptive metabolic changes of cancer cells promote their survival and affect tumor immune cells in the tumor microenvironment (TME), which contributes to tumor immunosuppressive microenvironment and induces tumor immunotherapy resistance. Here, we summarize the hypoxic microenvironment, its effect on metabolic reprogramming, and its contribution to immunotherapy resistance in pancreatic cancer.

Diagnostic, Predictive and Prognostic Molecular Biomarkers in Pancreatic Cancer: An Overview for Clinicians

Simple Summary

Pancreatic cancer is the fourth most common cancer-related cause of death in the United States and is usually asymptomatic in early stages. There is a scarcity of tests that facilitate early diagnosis or accurately predict the disease progression. To this end, biomarkers have been identified as important tools in the diagnosis and management of pancreatic cancer. Despite the increasing number of biomarkers described in the literature, most of them have demonstrated moderate sensitivity and/or specificity and are far from being considered as screening tests. More efficient non-invasive biomarkers are needed to facilitate early-stage diagnosis and interventions. Multi-disciplinary collaboration might be required to facilitate the identification of such markers.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the most common pancreatic malignancy and is associated with aggressive tumor behavior and poor prognosis. Most patients with PDAC present with an advanced disease stage and treatment-resistant tumors. The lack of noninvasive tests for PDAC diagnosis and survival prediction mandates the identification of novel biomarkers. The early identification of high-risk patients and patients with PDAC is of utmost importance. In addition, the identification of molecules that are associated with tumor biology, aggressiveness, and metastatic potential is crucial to predict survival and to provide patients with personalized treatment regimens. In this review, we summarize the current literature and focus on newer biomarkers, which are continuously added to the armamentarium of PDAC screening, predictive tools, and prognostic tools.

Hypoxic pancreatic stellate cell-derived exosomal mirnas promote proliferation and invasion of pancreatic cancer through the PTEN/AKT pathway

Pancreatic stellate cells (PSCs) are important components of the tumor microenvironment in pancreatic cancer (PC) and contribute to its development and metastasis through mechanisms that remain incompletely characterized. Tumor hypoxia affects the function and behavior of PC and stromal cells, and can alter exosomal content to modify cell-cell communication. The present study explored the effects of exosomal miRNAs produced by hypoxia-preconditioned PSCs on the growth and metastatic potential of PC cells. Subcutaneous xenografts and liver metastasis mouse models revealed increased tumorigenic potential upon co-implantation of PC cells and PSCs as compared to PC cells alone. Screening miRNA profiles of mouse plasma exosomes and cultured PSCs, followed by miRNA overexpression and inhibition assays, enabled us to identify miR-4465 and miR-616-3p as prominent hypoxia-induced, PSC-derived, exosomal miRNAs promoting PC cell proliferation, migration, and invasion. Proteomics analysis of PC cells incubated with exosomes derived from hypoxic PSCs showed significant downregulation of PTEN. Dual-luciferase reporter assays and western blotting showed that both miR-4465 and miR-616-3p target PTEN and activate AKT signaling in PC cells. We conclude that hypoxia upregulates miR-4465 and miR-616-3p expression in PSC-derived exosomes. Following exosome uptake, these miRNAs promote PC progression and metastasis by suppressing the PTEN/AKT pathway.

Effect of Glucose Variability on Pancreatic Cancer Through Regulation of COL6A1

Background

Pancreatic cancer (PC), a devastating cancer worldwide, remains dismal prognosis due to its clinical elusiveness, especially in relation to diabetes mellitus (DM). The study aims to investigate the effect of glucose variability on COL6A1 in PC cancer cells and the prognostic potential of COL6A1 for PC patient associated with DM.

Methods

After PC cancer cell lines of AsPC-1 and BxPC-3 were treated with hyperglycemia and hypoglycemia, Giemsa staining and Transwell chamber were performed to assay plate clone formation, migration and invasion. Expressions of COL6A1 of PC cancer cell lines under different extracellular glucose levels were detected by qRT-PCR and Western blotting. The level of COL6A1 expression in PC patients with/without DM was further observed with immunohistochemistry. The prognostic impact of COL6A1 on PC patients with DM was assessed by Kaplan–Meier survival curve analysis.

Results

Hyperglycemia promoted proliferation, migration and invasion of PC cancer cells compared with hypoglycemia. Glucose variability could regulate expression of COL6A1 in PC cancer cells, both Col6a1 mRNA and COL6A1 protein upregulated in cancer cells cultured with hyperglycemic than that with hypoglycemic. The level of COL6A1 expression was higher in PC patients with DM than that without DM. Besides, COL6A1 was significantly associated with the clinical prognosis of PC patients with DM, higher COL6A1 leading to lower overall survival (OS).

Conclusion

Glucose variability had effect on PC cancer cells through regulation of COL6A1. Accordingly, COL6A1 was associated with poorer prognosis in PC patients with DM.