Microenvironmental Determinants of Pancreatic Cancer

Identification of tumor antigens and immune subtypes of pancreatic adenocarcinoma for mRNA vaccine development

BACKGROUND

Although mRNA vaccines have been effective against multiple cancers, their efficacy against pancreatic adenocarcinoma (PAAD) remains undefined. Accumulating evidence suggests that immunotyping can indicate the comprehensive immune status in tumors and their immune microenvironment, which is closely associated with therapeutic response and vaccination potential. The aim of this study was to identify potent antigens in PAAD for mRNA vaccine development, and further distinguish immune subtypes of PAAD to construct an immune landscape for selecting suitable patients for vaccination.

METHODS

Gene expression profiles and clinical information of 239 PAAD datasets were extracted from ICGC, and RNA-Seq data of 103 samples were retrieved from TCGA. GEPIA was used to calculate differential expression levels and prognostic indices, cBioPortal program was used to compare genetic alterations, and TIMER was used to explore correlation between genes and immune infiltrating cells. Consensus cluster was used for consistency matrix construction and data clustering, DAVID was used for functional annotation, and graph learning-based dimensional reduction was used to depict immune landscape.

RESULTS

Six overexpressed and mutated tumor antigens associated with poor prognosis and infiltration of antigen presenting cells were identified in PAAD, including ADAM9, EFNB2, MET, TMOD3, TPX2, and WNT7A. Furthermore, five immune subtypes (IS1-IS5) and nine immune gene modules of PAAD were identified that were consistent in both patient cohorts. The immune subtypes showed distinct molecular, cellular and clinical characteristics. IS1 and IS2 exhibited immune-activated phenotypes and correlated to better survival compared to the other subtypes. IS4 and IS5 tumors were immunologically cold and associated with higher tumor mutation burden. Immunogenic cell death modulators, immune checkpoints, and CA125 and CA199, were also differentially expressed among the five immune subtypes. Finally, the immune landscape of PAAD showed a high degree of heterogeneity between individual patients.

CONCLUSIONS

ADAM9, EFNB2, MET, TMOD3, TPX2, and WNT7A are potent antigens for developing anti-PAAD mRNA vaccine, and patients with IS4 and IS5 tumors are suitable for vaccination.

CXCL10 is a Tumor Microenvironment and Immune Infiltration Related Prognostic Biomarker in Pancreatic Adenocarcinoma

Pancreatic adenocarcinoma (PAAD) is the 10th most common cancer worldwide and the outcomes for patients with the disease remain extremely poor. Precision biomarkers are urgently needed to increase the efficiency of early diagnosis and to improve the prognosis of patients. The tumor microenvironment (TME) and tumor immune infiltration are thought to impact the occurrence, progression, and prognosis of PAAD. Novel biomarkers excavated originating from the TME and immune infiltration may be effective in predicting the prognosis of PAAD patients. In the current study, the ESTIMATE and CIBERSORT algorithms were applied to estimate the division of immune and stromal components and the proportion of tumor-infiltrating immune cells in 182 PAAD cases downloaded from The Cancer Genome Atlas database. Intersection analyses of the Protein-Protein Interaction networks and Cox regression analysis identified the chemokine (CXC-motif) ligand 10 (CXCL10) as a predictive biomarker. We verified that CXCL10 in the TME negatively correlates with prognosis in PAAD and positively correlates with tumor cell differentiation. GSE62452 from the GEO database and cumulative survival analysis were performed to validate CXCL10 expression as an independent prognostic indicator. We also found that memory B cells, regulatory T cells, and macrophages M0 and M1 were correlated with the expression of CXCL10 indicating that expression of CXCL10 influenced the immune activity of the TME. Our data suggest that CXCL10 is beneficial as a prognostic indicator in PAAD patients and highlights the potential for immune targeted therapy in the treatment of PAAD.

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.

Ion Channels Orchestrate Pancreatic Ductal Adenocarcinoma Progression and Therapy

Pancreatic ductal adenocarcinoma is a devastating disease with a dismal prognosis. Therapeutic interventions are largely ineffective. A better understanding of the pathophysiology is required. Ion channels contribute substantially to the "hallmarks of cancer." Their expression is dysregulated in cancer, and they are "misused" to drive cancer progression, but the underlying mechanisms are unclear. Ion channels are located in the cell membrane at the interface between the intracellular and extracellular space. They sense and modify the tumor microenvironment which in itself is a driver of PDAC aggressiveness. Ion channels detect, for example, locally altered proton and electrolyte concentrations or mechanical stimuli and transduce signals triggered by these microenvironmental cues through association with intracellular signaling cascades. While these concepts have been firmly established for other cancers, evidence has emerged only recently that ion channels are drivers of PDAC aggressiveness. Particularly, they appear to contribute to two of the characteristic PDAC features: the massive fibrosis of the tumor stroma (desmoplasia) and the efficient immune evasion. Our critical review of the literature clearly shows that there is still a remarkable lack of knowledge with respect to the contribution of ion channels to these two typical PDAC properties. Yet, we can draw parallels from ion channel research in other fibrotic and inflammatory diseases. Evidence is accumulating that pancreatic stellate cells express the same "profibrotic" ion channels. Similarly, it is at least in part known which major ion channels are expressed in those innate and adaptive immune cells that populate the PDAC microenvironment. We explore potential therapeutic avenues derived thereof. Since drugs targeting PDAC-relevant ion channels are already in clinical use, we propose to repurpose those in PDAC. The quest for ion channel targets is both motivated and complicated by the fact that some of the relevant channels, for example, KCa3.1, are functionally expressed in the cancer, stroma, and immune cells. Only in vivo studies will reveal which arm of the balance we should put our weights on when developing channel-targeting PDAC therapies. The time is up to explore the efficacy of ion channel targeting in (transgenic) murine PDAC models before launching clinical trials with repurposed drugs.

ICG/l-Arginine Encapsulated PLGA Nanoparticle-Thermosensitive Hydrogel Hybrid Delivery System for Cascade Cancer Photodynamic-NO Therapy with Promoted Collagen Depletion in Tumor Tissues

Photodynamic therapy (PDT) is promising for clinical cancer therapy; however, the efficacy was limited as an individual treatment regimen. Here, an approach synergistically combining PDT and nitric oxide (NO) gas therapy along with destruction of the tumor extracellular matrix (ECM) was presented to eliminate cancer. Specifically, the NO donor l-arginine (l-Arg) and the photosensitizer indocyanine green (ICG) were co-encapsulated in poly(lactic-glycolic acid) (PLGA) nanoparticles and then loaded into the poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL) hydrogel to develop an injectable, thermosensitive dual drug delivery system (PLGA@ICG@l-Arg/Gel). Significantly, reactive oxygen species (ROS) produced by PLGA@ICG@l-Arg/Gel under near-infrared (NIR) light irradiation could not only result in the apoptosis of cancer cells but also oxidize l-Arg to generate NO, which could suppress the proliferation of cancer cells. Moreover, ROS could further oxidize NO to generate peroxynitrite anions (ONOO^-). ONOO^- could activate matrix metalloproteinases (MMPs), which notably degraded collagen in ECM so as to damage the tumor microenvironment. PLGA@ICG@l-Arg/Gel significantly increased the antitumor efficacy against highly malignant 4T1 tumors in mice. Taken together, PLGA@ICG@l-Arg/Gel is a multifunctional platform that provides a novel strategy for cancer treatment with cascade amplification of the ROS oxidation effect, which holds great potential in clinical translation.

Hyaluronic Acid Correlates With Bone Metastasis and Predicts Poor Prognosis in Small-Cell Lung Cancer Patients

BACKGROUND

Hyaluronan (HA) is one of the essential elements of the extracellular matrix (ECM), involved in the onset of metastasis in various tumors. The interaction and binding of the ligand-receptor HA/cluster of differentiation-44 (CD44) regulate the physical and biochemical properties of the ECM, which correlates with an increased propensity toward metastasis and poor survival outcome. Our study aimed to explore HA for predicting metastasis and survival rate in patients with small-cell lung cancer (SCLC).

MATERIALS AND METHODS

This prospective cohort study recruited 72 patients with SCLC. Plasma HA and CD44 levels were assayed by enzyme-linked immunosorbent assay (ELISA) for 72 cases before initial systematic treatment (baseline samples), and plasma HA was detected via after-2-cycle-chemotherapy (A-2-C-CT) in 48 samples. Logistic regression analysis and the Cox proportional risk model were used to determine the independent predictors of distant metastasis and survival rate of patients.

RESULTS

Baseline plasma HA was notably associated with bone metastasis (BM) [OR (95% CI = 1.015 (1.006-1.024), p = 0.001]. Multivariate logistic regression analysis showed that baseline plasma HA was chosen as an independent predictor of BM. Either baseline HA or CD44 or both were associated with BM. Dynamic alteration of HA was notably associated with A-2-C-CT clinical efficacy. Multivariate Cox regression analysis in forward likelihood ratio showed that A-2-C-CT HA was an independent predictor of progression-free survival (PFS) and overall survival (OS).

CONCLUSIONS

HA appears to be used as an independent predictive factor for BM, and the dynamic detection of HA can predict prognosis in SCLC patients. The mechanism of the HA/CD44 axis in BM of SCLC deserves further exploration.

Extracellular Matrix Composition Modulates the Responsiveness of Differentiated and Stem Pancreatic Cancer Cells to Lipophilic Derivate of Gemcitabine

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal disease. Gemcitabine (GEM) is used as the gold standard drug in PDAC treatment. However, due to its poor efficacy, it remains urgent to identify novel strategies to overcome resistance issues. In this context, an intense stroma reaction and the presence of cancer stem cells (CSCs) have been shown to influence PDAC aggressiveness, metastatic potential, and chemoresistance.

METHODS

We used three-dimensional (3D) organotypic cultures grown on an extracellular matrix composed of Matrigel or collagen I to test the effect of the new potential therapeutic prodrug 4-(N)-stearoyl-GEM, called C18GEM. We analyzed C18GEM cytotoxic activity, intracellular uptake, apoptosis, necrosis, and autophagy induction in both Panc1 cell line (P) and their derived CSCs.

RESULTS

PDAC CSCs show higher sensitivity to C18GEM treatment when cultured in both two-dimensional (2D) and 3D conditions, especially on collagen I, in comparison to GEM. The intracellular uptake mechanisms of C18GEM are mainly due to membrane nucleoside transporters' expression and fatty acid translocase CD36 in Panc1 P cells and to clathrin-mediated endocytosis and CD36 in Panc1 CSCs. Furthermore, C18GEM induces an increase in cell death compared to GEM in both cell lines grown on 2D and 3D cultures. Finally, C18GEM stimulated protective autophagy in Panc1 P and CSCs cultured on 3D conditions.

CONCLUSION

We propose C18GEM together with autophagy inhibitors as a valid alternative therapeutic approach in PDAC treatment.

Comprehensive analysis of prognostic immune-related genes associated with the tumor microenvironment of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a malignant tumor with a specific tumor immune microenvironment (TIME). Therefore, investigating prognostic immune-related genes (IRGs) that are closely associated with TIME to predict PDAC clinical outcomes is necessary. In the present study, 459 samples of PDAC from the Genotype-Tissue Expression database, The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC) and Gene Expression Omnibus (GEO) were included and a survival-associated module was identified using weighted gene co-expression network analysis. Based on the Cox regression analysis and least absolute shrinkage and selection operator analysis, four IRGs (2′-5′-oligoadenylate synthetase 1, MET proto-oncogene, receptor tyrosine kinase, interleukin 1 receptor type 2 and interleukin 20 receptor subunit β) were included in the prognostic model to calculate the risk score (RS), and patients with PDAC were divided into high- and low-RS groups. Kaplan-Meier survival and receiver operating characteristic curve analyses demonstrated that the low-RS group had significantly improved survival conditions compared with the high-RS group in TCGA training set. The prognostic function of the model was also validated using ICGC and GEO cohorts. To investigate the mechanism of different overall survival between the high- and low-RS groups, the present study included Estimation of Stromal and Immune Cells in Malignant Tumor Tissues Using Expression Data and Cell Type Identification by Estimating Relative Subset of Known RNA Transcripts algorithms to investigate the state of the tumor microenvironment and immune infiltration inpatients in the cohort from TCGA. In summary, four genes associated with the TIME of PDAC were identified, which may provide a reference for clinical treatment.

Bioinformatics and Molecular Insights to Anti-Metastasis Activity of Triethylene Glycol Derivatives

The anti-metastatic and anti-angiogenic activities of triethylene glycol derivatives have been reported. In this study, we investigated their molecular mechanism(s) using bioinformatics and experimental tools. By molecular dynamics analysis, we found that (i) triethylene glycol dimethacrylate (TD-10) and tetraethylene glycol dimethacrylate (TD-11) can act as inhibitors of the catalytic domain of matrix metalloproteinases (MMP-2, MMP-7 and MMP-9) by binding to the S1’ pocket of MMP-2 and MMP-9 and the catalytic Zn ion binding site of MMP-7, and that (ii) TD-11 can cause local disruption of the secondary structure of vascular endothelial growth factor A (VEGFA) dimer and exhibit stable interaction at the binding interface of VEGFA receptor R1 complex. Cell-culture-based in vitro experiments showed anti-metastatic phenotypes as seen in migration and invasion assays in cancer cells by both TD-10 and TD-11. Underlying biochemical evidence revealed downregulation of VEGF and MMPs at the protein level; MMP-9 was also downregulated at the transcriptional level. By molecular analyses, we demonstrate that TD-10 and TD-11 target stress chaperone mortalin at the transcription and translational level, yielding decreased expression of vimentin, fibronectin and hnRNP-K, and increase in extracellular matrix (ECM) proteins (collagen IV and E-cadherin) endorsing reversal of epithelial–mesenchymal transition (EMT) signaling.

Depletion of Macrophages Improves Therapeutic Response to Gemcitabine in Murine Pancreas Cancer

BACKGROUND

The tumor microenvironment (TME) is composed of fibro-inflammatory cells and extracellular matrix (ECM) components. However, the exact contribution of the various TME compartments towards therapeutic response is unknown. Here, we aim to dissect the specific contribution of tumor-associated macrophages (TAMs) towards drug delivery and response in pancreatic ductal adenocarcinoma (PDAC).

METHODS

The effect of gemcitabine was assessed in human and murine macrophages, human pancreatic stellate cells (hPSCs), and tumor cells (L3.6pl, BxPC3 and KPC) in vitro. The drug metabolism of gemcitabine was analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Preclinical studies were conducted using KrasG12D;p48-Cre and KrasG12D;p53172H;Pdx-Cre mice to investigate gemcitabine delivery at different stages of tumor progression and upon pharmacological TAM depletion.

RESULTS

Gemcitabine accumulation was significantly increased in murine PDAC tissue compared to pancreatic intraepithelial neoplasia (PanIN) lesions and healthy control pancreas tissue. In vitro, macrophages accumulated and rapidly metabolized gemcitabine resulting in a significant drug scavenging effect for gemcitabine. Finally, pharmacological TAM depletion enhanced therapeutic response to gemcitabine in tumor-bearing KPC mice.

CONCLUSION

Macrophages rapidly metabolize gemcitabine in vitro, and pharmacological depletion improves the therapeutic response to gemcitabine in vivo. Our study supports the notion that TAMs might be a promising therapeutic target in PDAC.