Overcoming immune evasion in pancreatic cancer: the combination matters

Association between AHR Expression and Immune Dysregulation in Pancreatic Ductal Adenocarcinoma: Insights from Comprehensive Immune Profiling of Peripheral Blood Mononuclear Cells

Pancreatic cancer, particularly pancreatic ductal adenocarcinoma (PDAC), has an immune suppressive environment that allows tumour cells to evade the immune system. The aryl-hydrocarbon receptor (AHR) is a transcription factor that can be activated by certain exo/endo ligands, including kynurenine (KYN) and other tryptophan metabolites. Once activated, AHR regulates the expression of various genes involved in immune responses and inflammation. Previous studies have shown that AHR activation in PDAC can have both pro-tumorigenic and anti-tumorigenic effects, depending on the context. It can promote tumour growth and immune evasion by suppressing anti-tumour immune responses or induce anti-tumour effects by enhancing immune cell function. In this study involving 30 PDAC patients and 30 healthy individuals, peripheral blood samples were analysed. PDAC patients were categorized into Low (12 patients) and High/Medium (18 patients) AHR groups based on gene expression in peripheral blood mononuclear cells (PBMCs). The Low AHR group showed distinct immune characteristics, including increased levels of immune-suppressive proteins such as PDL1, as well as alterations in lymphocyte and monocyte subtypes. Functional assays demonstrated changes in phagocytosis, nitric oxide production, and the expression of cytokines IL-1, IL-6, and IL-10. These findings indicate that AHR's expression level has a crucial role in immune dysregulation in PDAC and could be a potential target for early diagnostics and personalised therapeutics.

Interventional hydrogel microsphere vaccine as an immune amplifier for activated antitumour immunity after ablation therapy

The response rate of pancreatic cancer to chemotherapy or immunotherapy pancreatic cancer is low. Although minimally invasive irreversible electroporation (IRE) ablation is a promising option for irresectable pancreatic cancers, the immunosuppressive tumour microenvironment that characterizes this tumour type enables tumour recurrence. Thus, strengthening endogenous adaptive antitumour immunity is critical for improving the outcome of ablation therapy and post-ablation immune therapy. Here we present a hydrogel microsphere vaccine that amplifies post-ablation anti-cancer immune response via releasing its cargo of FLT3L and CD40L at the relatively lower pH of the tumour bed. The vaccine facilitates migration of the tumour-resident type 1 conventional dendritic cells (cDC1) to the tumour-draining lymph nodes (TdLN), thus initiating the cDC1-mediated antigen cross-presentation cascade, resulting in enhanced endogenous CD8+ T cell response. We show in an orthotopic pancreatic cancer model in male mice that the hydrogel microsphere vaccine transforms the immunologically cold tumour microenvironment into hot in a safe and efficient manner, thus significantly increasing survival and inhibiting the growth of distant metastases.

Mechanisms and Molecular Targets of Artemisinin in Cancer Treatment

The major problems with cancer therapy are drug-induced side effects. There is an urgent need for safe anti-tumor drugs. Artemisinin is a Chinese herbal remedy for malaria with efficacy and safety. However, several studies reported that artemisinin causes neurotoxicity and cardiotoxicity in animal models. Recently, nanostructured drug delivery systems have been designed to improve therapeutic efficacy and reduce toxicity. Artemisinin has been reported to show anticancer properties. The anticancer effects of artemisinin appear to be mediated by inducing cell cycle arrest, promoting ferroptosis and autophagy, inhibiting cell metastasis. Therefore, the review is to concentrate on mechanisms and molecular targets of artemisinin as anti-tumor agents. We believe these will be important topics in realizing the potential of artemisinin and its derivatives as potent anticancer agents.

Downregulated F-Box/LRR-Repeat Protein 7 Facilitates Pancreatic Cancer Metastasis by Regulating Snail1 for Proteasomal Degradation

Pancreatic cancer (PCa) is one of the most aggressive lethal malignancies, and cancer metastasis is the major cause of PCa-associated death. F-box/LRR-repeat protein 7 (FBXL7) regulates cancer metastasis and the chemosensitivity of human pancreatic cancer. However, the clinical significance and biological role of FBXL7 in PCa have been rarely studied. In this study, we found that the expression of FBXL7 was down-regulated in PCa tissues compared with tumor-adjacent tissues, and the low expression of FBXL7 was positively associated with cancer metastasis. Functionally, overexpression of FBXL7 attenuated PANC1 cell invasion, whereas FBXL7 silencing promoted BxPC-3 cell invasion. Forced expression of FBXL7 upregulated the expression of epithelial markers (e.g., E-cadherin) and repressed the expression of mesenchymal markers (e.g., N-cadherin and Vimentin), indicating that FBXL7 negatively regulated the epithelial-mesenchymal transition (EMT) of PCa cells. Furthermore, we identified that FBXL7 repressed the expression of Snail1, a crucial transcription factor of EMT. Mechanistically, FBXL7 bound to Snail1 and promoted its ubiquitination and proteasomal degradation. In vivo studies demonstrated that FBXL7 inhibition promotes PCa metastasis. Taken together, our findings demonstrate that FBXL7 knockdown could efficiently enhance PCa metastasis by regulating Snail1-dependent EMT.

Shikonin-mediated PD-L1 degradation suppresses immune evasion in pancreatic cancer by inhibiting NF-κB/STAT3 and NF-κB/CSN5 signaling pathways

BACKGROUND

Pancreatic cancer (PC) is a highly fatal malignancy with few effective therapies currently available. Recent studies have shown that PD-L1 inhibitors could be potential therapeutic targets for the treatment of PC. The present study aims to investigate the effect of Shikonin on immune evasion in PC with the involvement of the PD-L1 degradation.

METHODS

Initially, the expression patterns of PD-L1 and NF-κB in PC were predicted in-silico using the GEPIA database, and were subsequently validated using PC tissues. Thereafter, the correlation of NF-κB with STAT3, CSN5 and PD-L1 was examined. PC cells were treated with Shikonin, NF-κB inhibitor, STAT3 activator, and CSN5 overexpression plasmid to investigate effects on PD-L1 glycosylation and immune evasion in PC. Finally, in vivo tumor formation was induced in C57BL/6J mice, in order to verify the in vitro results.

RESULTS

PD-L1, NF-κB, NF-κB p65, STAT3, and CSN5 were highly expressed in PC samples, and NF-κB was positively correlated with STAT3/CSN5/PD-L1. Inhibition of NF-κB decreased PD-L1 glycosylation and increased PD-L1 degradation, whereas activated STAT3 and overexpressed CSN5 reversed these trends. Shikonin blocked immune evasion in PC, and lowered the expression of PD-L1, NF-κB, NF-κB p65, STAT3 and CSN5 in vivo and in vitro.

CONCLUSION

The findings indicated Shikonin inhibited immune evasion in PC by inhibiting PD-L1 glycosylation and activating the NF-κB/STAT3 and NF-κB/CSN5 signaling pathways. These effects of Shikonin on PC cells may bear important potential therapeutic implications for the treatment of PC.

Targeting tumor-intrinsic hexosamine biosynthesis sensitizes pancreatic cancer to anti-PD1 therapy

Pancreatic ductal adenocarcinoma (PDAC) is considered to be a highly immunosuppressive and heterogenous neoplasm. Despite improved knowledge regarding the genetic background of the tumor and better understanding of the tumor microenvironment, immune checkpoint inhibitor therapy (targeting CTLA4, PD1, PDL1) has not been very successful against PDAC. The robust desmoplastic stroma, along with an extensive extracellular matrix (ECM) that is rich in hyaluronan, plays an integral role in this immune evasion. Hexosamine biosynthesis pathway (HBP), a shunt pathway of glycolysis, is a metabolic node in cancer cells that can promote survival pathways on the one hand and influence the hyaluronan synthesis in the ECM on the other. The rate-limiting enzyme of the pathway, glutamine-fructose amidotransferase 1 (GFAT1), uses glutamine and fructose 6-phosphate to eventually synthesize uridine diphosphate N-acetylglucosamine (UDP-GlcNAc). In the current manuscript, we targeted this glutamine-utilizing enzyme by a small molecule glutamine analog (6-diazo-5-oxo-l-norleucine [DON]). Our results showed that DON decreased the self-renewal potential and metastatic ability of tumor cells. Further, treatment with DON decreased hyaluronan and collagen in the tumor microenvironment, leading to an extensive remodeling of the ECM and an increased infiltration of CD8+ T cells. Additionally, treatment with DON sensitized pancreatic tumors to anti-PD1 therapy, resulting in tumor regression and prolonged survival.

GFAT1/HBP/O-GlcNAcylation Axis Regulates β-Catenin Activity to Promote Pancreatic Cancer Aggressiveness

Reprogrammed glucose and glutamine metabolism are essential for tumor initiation and development. As a branch of glucose and metabolism, the hexosamine biosynthesis pathway (HBP) generates uridine diphosphate N-acetylglucosamine (UDP-GlcNAc) and contributes to the O-GlcNAcylation process. However, the spectrum of HBP-dependent tumors and the mechanisms by which the HBP promotes tumor aggressiveness remain areas of active investigation. In this study, we analyzed the activity of the HBP and its prognostic value across 33 types of human cancers. Increased HBP activity was observed in pancreatic ductal adenocarcinoma (PDAC), and higher HBP activity predicted a poor prognosis in PDAC patients. Genetic silencing or pharmacological inhibition of the first and rate-limiting enzyme of the HBP, glutamine:fructose-6-phosphate amidotransferase 1 (GFAT1), inhibited PDAC cell proliferation, invasive capacity, and triggered cell apoptosis. Notably, these effects can be restored by addition of UDP-GlcNAc. Moreover, similar antitumor effects were noticed by pharmacological inhibition of GFAT1 with 6-diazo-5-oxo-l-norleucine (DON) or Azaserine. PDAC is maintained by oncogenic Wnt/β-catenin transcriptional activity. Our data showed that GFAT1 can regulate β-catenin expression via modulation of the O-GlcNAcylation process. TOP/FOP-Flash and real-time qPCR analysis showed that GFAT1 knockdown inhibited β-catenin activity and the transcription of its downstream target genes CCND1 and MYC. Ectopic expression of a stabilized form of β-catenin restored the suppressive roles of GFAT1 knockdown on PDAC cell proliferation and invasion. Collectively, our findings indicate that higher GFAT1/HBP/O-GlcNAcylation exhibits tumor-promoting roles by maintaining β-catenin activity in PDAC.

TWIST1 transcriptionally regulates glycolytic genes to promote the Warburg metabolism in pancreatic cancer

Reprogrammed glucose metabolism is essential for tumor initiation and development, especially for pancreatic ductal adenocarcinoma (PDAC). Most cancer cells rely on aerobic glycolysis, a phenomenon termed "the Warburg effect", to support uncontrolled proliferation and evade apoptosis. However, the direct regulators of the Warburg effect remain areas of active investigation. In this study, we found that the highly conserved transcription factor, TWIST1, is a crucial regulator of aerobic glycolysis in PDAC. Genetic silencing of TWIST1 significantly inhibited the glycolytic phenotypes of PDAC cells as revealed by reduced glucose uptake, lactate production, and extracellular acidification rate, which can be restored by re-expression of siRNA-resistant TWIST1. Moreover, tamoxifen-inducible expression of TWIST1 promoted the Warburg metabolism of PDAC cells. Mechanistically, by luciferase reporter assay and chromatin immunoprecipitation experiment, we showed that TWIST1 can directly increase the expression of several glycolytic genes, including SLC2A1, HK2, ENO1, and PKM2. Of note, the transcriptional regulation by TWIST1 was not dependent on HIF1α or c-Myc. In The Cancer Genome Atlas and Gene Expression Omnibus accession GSE15471, we confirmed that TWIST1 was closely associated with the glycolysis pathway. Collectively, our findings indicate that TWIST1 is likely to act as important regulator of the Warburg effect in PDAC.

Tumoral EHF predicts the efficacy of anti-PD1 therapy in pancreatic ductal adenocarcinoma

EHF transcriptionally inhibits the expressions of TGFβ1 and GM-CSF to decrease T reg cell and MDSC accumulation, making it a promising biomarker to evaluate the immune microenvironment in PDAC. EHF overexpression may improve the efficacy of checkpoint immunotherapy in PDAC.

Pancreatic ductal adenocarcinoma (PDAC) is a highly immune-suppressive tumor with a low response rate to single checkpoint blockade therapy. ETS homologous factor (EHF) is a tumor suppressor in PDAC. Here, we report a novel function of EHF in pancreatic cancer immune microenvironment editing and efficacy prediction for anti-PD1 therapy. Our findings support that the deficiency of tumoral EHF induced the accumulation of regulatory T (T reg) cells and myeloid-derived suppressor cells (MDSCs) and a decrease in the number of tumor-infiltrating CD8⁺ T cells. Mechanistically, EHF deficiency induced the conversion and expansion of T reg cells and MDSCs through inhibiting tumor TGFβ1 and GM-CSF secretion. EHF suppressed the transcription of TGFB1 and CSF2 by directly binding to their promoters. Mice bearing EHF overexpression tumors exhibited significantly better response to anti-PD1 therapy than those with control tumors. Our findings delineate the immunosuppressive mechanism of EHF deficiency in PDAC and highlight that EHF overexpression may improve PDAC checkpoint immunotherapy.

B7-H5/CD28H is a co-stimulatory pathway and correlates with improved prognosis in pancreatic ductal adenocarcinoma

B7-H5 and its cognate receptor CD28H are T lymphocyte second signaling transduction molecules. Here we aimed to explore the function of this pathway in pancreatic cancer in vitro and in vivo, and evaluated the clinical significance in 136 patients with pancreatic ductal adenocarcinoma enrolled from January 2012 to February 2017 in our hospital. Surgical tumor specimens were collected for immunohistochemical staining to evaluate B7-H5 expression. Patients' baseline characteristics, including gender, age, tumor size, tumor location, tumor grading, clinical TNM staging, tumor infiltrating lymphocytes, CA19-9 and chemotherapy treatment, along with the subsequent follow-up data, were documented and analyzed. When co-cultured with T cells, pancreatic cancer PC cells with high B7-H5 expression induced a more potent immune reaction, indicated by elevated cytokine release and increased proliferation of T lymphocytes compared with cells exhibiting low B7-H5 expression. Xenograft pancreatic tumors derived from high B7-H5 expression PC cells exhibited attenuated growth compared to tumors from low B7-H5 expression cells after transfusion with T lymphocytes in immune-deficient mice. Of the 136 PDAC tumor tissues, 93 (68.38%) were strong and 43 (31.62%) were weak B7-H5 expression. Patients with strong B7-H5 expression had significantly longer overall survival than those with weak expression (median: 16.5 vs 11.5 months, P = .017). TNM staging, tumor location and subsequent chemotherapy were also prognostic factors in these patients. Collectively, B7-H5/CD28H is a co-stimulatory signal pathway, and expression of B7-H5 is associated with improved disease prognosis in patients with pancreatic cancer.

High Glucose-Induced ROS Production Stimulates Proliferation of Pancreatic Cancer via Inactivating the JNK Pathway

Aberrant glucose metabolism of diabetes mellitus or hyperglycemia stimulates pancreatic tumorigenesis and progression. Hyperglycemic environment can increase the ROS level of tumors, but the role of upregulation of ROS levels in pancreatic cancer (PC) still remains controversial. Here, the same as other reports, we demonstrate that high glucose promoted pancreatic cancer cell growth and resulted in an increase in the level of ROS. However, it is interesting that the phosphorylation of JNK was reduced. When treating PC cells with N-acetyl-L-cysteine (NAC), the intracellular ROS generation is repressed, but the expression of phosphorylation of JNK and c-Jun increased. Moreover, the JNK inhibitor SP600125 significantly promoted cell proliferation and suppressed cell apoptosis of pancreatic cancer cells under high glucose conditions. Collectively, high levels of ROS induced by high glucose conditions stimulated the proliferation of pancreatic cancer cells, and it may be achieved by inactivating the JNK pathway.