Synergistic inhibition of pancreatic cancer with anti-PD-L1 and c-Myc inhibitor JQ1

Olaparib Combined with Anti-PD1 Enhances Immunotherapy of Gastric Cancer Via NF-κB/c-Myc/PD-L1 Signaling

BACKGROUND

PARP inhibitors, effective in BRCA-mutated cancers, show potential in gastric cancer (GC) where homologous recombination defects (e.g., BRCA1/2 mutations) are common. Olaparib, a PARP inhibitor, upregulates PD-L1, suggesting synergy with PD-1 inhibitors for enhanced GC therapy.

METHODS

Using CCK-8 screening of 867 drugs, olaparib demonstrated potent GC cell inhibition. Western blot and qRT-PCR assessed PD-L1, c-MYC, COX-2, and NF-κB pathway proteins (p65/p-p65). Functional assays (Transwell, wound healing, colony formation) evaluated olaparib's effects on GC cell proliferation, migration, and invasion. A GC mouse model tested olaparib combined with anti-PD1. TCGA and Kaplan-Meier analyzed PARP expression-prognosis correlations.

RESULTS

Olaparib suppressed GC cell proliferation, migration, and invasion in vitro. Western blot revealed upregulated c-MYC, COX-2, p65, p-p65, and PD-L1, confirmed by qRT-PCR for PD-L1. Low PARP expression correlated with better GC patient survival. In vivo, olaparib synergized with anti-PD1 to enhance tumor suppression.

CONCLUSION

Olaparib activates the NF-κB/c-MYC pathway to elevate PD-L1, supporting its combination with PD-1 inhibitors as a promising GC therapeutic strategy.

Annexin A1 regulates inflammatory-immune response and reduces pancreatic and extra- pancreatic injury during severe acute pancreatitis

Severe acute pancreatitis (SAP) poses significant challenges due to its complex pathophysiology, which includes inflammatory-immune responses that cause considerable damage to both the pancreas and other tissues. In this study, we explored the role of Annexin A1 (Anxa1), a glucocorticoid-regulated protein recognized for its anti-inflammatory properties, in regulating inflammation during acute pancreatitis. Using flow cytometry, single-cell RNA sequencing, and gene expression analysis, we examined how Anxa1 expression is regulated in myeloid cells throughout acute pancreatitis, employing various animal models to evaluate the consequences of modulating Anxa1 on injuries induced by SAP. Our findings revealed dynamic regulation of Anxa1 expression in myeloid cells, with mice lacking Anxa1 exhibiting worsened pancreatic injury and heightened systemic inflammation, resulting in significant damage to extra-pancreatic organs such as the lungs, liver, and kidneys. In contrast, treatment with Ac2-26, a synthetic peptide derived from Anxa1, effectively mitigated both pancreatic and extra-pancreatic inflammation and tissue damage. Overall, this study highlights the critical role of Anxa1 in modulating inflammatory responses during acute pancreatitis. Targeting Anxa1 presents a promising therapeutic strategy to mitigate pancreatic injury and prevent systemic complications associated with severe acute pancreatitis.

PET Imaging of PD-L1 Occupancy for Preclinical Assessment of the Efficacy of Combined Anti-PD-L1 Immunotherapy and Targeted Therapy

The development of resistance significantly hampers the efficacy of immunotherapies in cancer treatment. The combination of JQ1, a BRD4 protein inhibitor, and anti-programmed death ligand 1 (PD-L1) immunotherapies has a synergic therapeutic potential to treat solid tumors. This study aimed to evaluate the potential of immuno-PET imaging for measuring pharmacodynamic biomarkers in response to this combination therapy targeting PD-L1. Methods: We synthesized different radioligands derived from the anti-PD-L1 C4 antibody and a minibody targeting murine CD8α for immuno-PET imaging. We conducted experiments on human non-small cell lung cancer and mouse colorectal carcinoma animal models to assess the efficacy of JQ1 and avelumab treatment on PD-L1 expression and immune cell infiltration by immuno-PET imaging. Taking advantage of the unique properties of the C4-derived minibody, we measured PD-L1 occupancy in tumors after treatment. Results: JQ1 efficiently reduced PD-L1 extracellular expression across all tested cell lines in vitro and in vivo. Avelumab and JQ1 treatments alone or in combination led to significant tumor growth reduction in the immunocompetent murine colorectal carcinoma model, reducing mean tumor growth from 725% in the control group to 125% in the combination group. Treatments also significantly increased the survival of mice by 4-12 d compared with the control group. Although imaging CD8-positive T-cell infiltration did not predict tumoral response, imaging the unoccupied fraction of PD-L1 after treatment was predictive of tumor growth reduction and survival. Conclusion: Immuno-PET imaging with noncompetitive radioligands throughout the treatment course could improve the efficiency and support rationalization of the dosing regimen of immunotherapies.

Delineating MYC-Mediated Escape Mechanisms from Conventional and T Cell-Redirecting Therapeutic Antibodies

In B-cell malignancies, the overexpression of MYC is associated with poor prognosis, but its mechanism underlying resistance to immunochemotherapy remains less clear. In further investigations of this issue, we show here that the pharmacological inhibition of MYC in various lymphoma and multiple myeloma cell lines, as well as patient-derived primary tumor cells, enhances their susceptibility to NK cell-mediated cytotoxicity induced by conventional antibodies targeting CD20 (rituximab) and CD38 (daratumumab), as well as T cell-mediated cytotoxicity induced by the CD19-targeting bispecific T-cell engager blinatumomab. This was associated with upregulation of the target antigen only for rituximab, suggesting additional escape mechanisms. To investigate these mechanisms, we targeted the MYC gene in OCI-LY18 cells using CRISPR-Cas9 gene-editing technology. CRISPR-Cas9-mediated MYC targeting not only upregulated CD20 but also triggered broader apoptotic pathways, upregulating pro-apoptotic PUMA and downregulating anti-apoptotic proteins BCL-2, XIAP, survivin and MCL-1, thereby rendering tumor cells more prone to apoptosis, a key tumor-lysis mechanism employed by T-cells and NK-cells. Moreover, MYC downregulation boosted T-cell activation and cytokine release in response to blinatumomab, revealing a MYC-mediated T-cell suppression mechanism. In conclusion, MYC overexpressing tumor cells mitigated the efficacy of therapeutic antibodies through several non-overlapping mechanisms. Given the challenges associated with direct MYC inhibition due to toxicity, successful modulation of MYC-mediated immune evasion mechanisms may improve the outcome of immunotherapeutic approaches in B-cell malignancies.

Bromodomain inhibitor treatment leads to overexpression of multiple kinases in cancer cells

The bromodomain and extraterminal (BET) family of proteins show altered expression across various cancers. The members of the bromodomain (BRD) family contain epigenetic reader domains that bind to acetylated lysine residues in both histone and non-histone proteins. Since BRD proteins are involved in cancer initiation and progression, therapeutic targeting of these proteins has recently been an area of interest. In experimental settings, JQ1, a commonly used BRD inhibitor, is the first known inhibitor to target BRD-containing protein 4 (BRD4), a ubiquitously expressed BRD and extraterminal family protein. BRD4 is necessary for a normal cell cycle, and its aberrant expression activates pro-inflammatory cytokines, leading to tumor initiation and progression. Various BRD4 inhibitors have been developed recently and tested in preclinical settings and are now in clinical trials. However, as with many targeted therapies, BRD inhibitor treatment can lead to resistance to treatment. Here, we investigated the kinases up-regulated on JQ1 treatment that may serve as target for combination therapy along with BRD inhibitors. To identify kinase targets, we performed a comparative analysis of gene expression data using RNA from BRD inhibitor-treated cells or BRD-modulated cells and identified overexpression of several kinases, including FYN, NEK9, and ADCK5. We further validated, by immunoblotting, the overexpression of FYN tyrosine kinase; NEK9 serine/threonine kinase and ADCK5, an atypical kinase, to confirm their overexpression after BRD inhibitor treatment. Importantly, our studies show that targeting FYN or NEK9 along with BRD inhibitor effectively reduces proliferation of cancer cells. Therefore, our research emphasizes a potential approach of utilizing inhibitors targeting some of the overexpressed kinases in conjunction with BRD inhibitors to enhance therapeutic effectiveness.

Development of a streamlined NGS-based TCGA classification scheme for gastric cancer and its implications for personalized therapy

BACKGROUND

The Cancer Genome Atlas (TCGA) has identified four distinct molecular subtypes of gastric cancer (GC) with prognostic significance: Epstein-Barr virus (EBV)-positive, microsatellite instability (MSI)-high, genomically stable (GS), and chromosomal instability (CIN). Unfortunately, the complex analysis required for TCGA classification limits its practical use in clinical settings. Our study sought to devise a next-generation sequencing (NGS)-based method to classify GC more efficiently, serving as a promising biomarker for prognosis and immunotherapy efficacy.

METHODS

This study was a retrospective observation study, and we employed 2 independent GC cohorts. The 3DMed cohort (n=765), comprising data on 733 cancer-related genes along with 4 EBV-encoded genes, was utilized to develop the new NGS classification. Additionally, the secondary Korean cohort (n=55), which includes both genomic data and information on immune checkpoint inhibitor (ICI) treatment, was employed to establish a correlation between NGS subtypes and ICI responsiveness.

RESULTS

In the 3DMed cohort, we identified 5.2% EBV, 4.6% MSI, 30.6% GS, and 59.6% CIN subtypes. The MSI subtype exhibited the highest number of mutation events, along with the highest tumor mutational burden (TMB) and strong programmed cell death ligand 1 (PD-L1) expression. CIN tumors showed extensive copy number variations (CNVs) and genomic heterogeneity. The EBV subtype presented recurrent ARID1A and PIK3CA mutations and fewer TP53 mutations. GS tumors exhibited specific mutations in CDH1 and ARID1A. In the Korean cohort, ICIs were most effective in MSI and EBV cases, showing disease control rates of 100%, compared to 62.9% in GS and 12.5% in CIN subtypes.

CONCLUSIONS

The NGS method successfully maps the mutational landscape of GC, providing a practical TCGA classification surrogate to optimize patient-specific treatment strategies.

Suppression of pancreatic cancer proliferation through TXNIP-mediated inhibition of the MAPK signaling pathway

Thioredoxin-interacting protein (TXNIP) is a crucial thioredoxin-binding protein that is recognized as a tumor suppressor in diverse malignancies, such as breast cancer, lung cancer, hepatocellular carcinoma, and thyroid cancer. However, the specific role and molecular mechanisms of TXNIP in the pathogenesis and progression of pancreatic cancer cells have not been determined. In this study, we investigate the relationship between TXNIP expression and overall survival prognosis in pancreatic cancer patients. Mechanistic studies are conducted to reveal the role of TXNIP in pancreatic cancer cell proliferation, migration, and regulation during malignancy. Our findings indicate that patients with high TXNIP expression have a more favorable prognosis. In vitro experiments with pancreatic cell lines show that overexpression of TXNIP suppresses the proliferation and migration of pancreatic cancer cells. Furthermore, we find that TXNIP inhibits the activation of the MAPK signaling pathway, thereby decreasing the malignant potential of pancreatic cancer. In conclusion, our study reveals TXNIP as a promising new predictive marker and therapeutic target for pancreatic cancer.

Opaganib (ABC294640) Induces Immunogenic Tumor Cell Death and Enhances Checkpoint Antibody Therapy

Antibody-based cancer drugs that target the checkpoint proteins CTLA-4, PD-1 and PD-L1 provide marked improvement in some patients with deadly diseases such as lung cancer and melanoma. However, most patients are either unresponsive or relapse following an initial response, underscoring the need for further improvement in immunotherapy. Certain drugs induce immunogenic cell death (ICD) in tumor cells in which the dying cells promote immunologic responses in the host that may enhance the in vivo activity of checkpoint antibodies. Sphingolipid metabolism is a key pathway in cancer biology, in which ceramides and sphingosine 1-phosphate (S1P) regulate tumor cell death, proliferation and drug resistance, as well as host inflammation and immunity. In particular, sphingosine kinases are key sites for manipulation of the ceramide/S1P balance that regulates tumor cell proliferation and sensitivity to radiation and chemotherapy. We and others have demonstrated that inhibition of sphingosine kinase-2 by the small-molecule investigational drug opaganib (formerly ABC294640) kills tumor cells and increases their sensitivities to other drugs and radiation. Because sphingolipids have been shown to regulate ICD, opaganib may induce ICD and improve the efficacy of checkpoint antibodies for cancer therapy. This was demonstrated by showing that in vitro treatment with opaganib increases the surface expression of the ICD marker calreticulin on a variety of tumor cell types. In vivo confirmation was achieved using the gold standard immunization assay in which B16 melanoma, Lewis lung carcinoma (LLC) or Neuro-2a neuroblastoma cells were treated with opaganib in vitro and then injected subcutaneously into syngeneic mice, followed by implantation of untreated tumor cells 7 days later. In all cases, immunization with opaganib-treated cells strongly suppressed the growth of subsequently injected tumor cells. Interestingly, opaganib treatment induced crossover immunity in that opaganib-treated B16 cells suppressed the growth of both untreated B16 and LLC cells and opaganib-treated LLC cells inhibited the growth of both untreated LLC and B16 cells. Next, the effects of opaganib in combination with a checkpoint antibody on tumor growth in vivo were assessed. Opaganib and anti-PD-1 antibody each slowed the growth of B16 tumors and improved mouse survival, while the combination of opaganib plus anti-PD-1 strongly suppressed tumor growth and improved survival (p < 0.0001). Individually, opaganib and anti-CTLA-4 antibody had modest effects on the growth of LLC tumors and mouse survival, whereas the combination of opaganib with anti-CTLA-4 substantially inhibited tumor growth and increased survival (p < 0.001). Finally, the survival of mice bearing B16 tumors was only marginally improved by opaganib or anti-PD-L1 antibody alone but was nearly doubled by the drugs in combination (p < 0.005). Overall, these studies demonstrate the ability of opaganib to induce ICD in tumor cells, which improves the antitumor activity of checkpoint antibodies.

Glutamine addiction and therapeutic strategies in pancreatic cancer

Pancreatic cancer remains one of the most lethal diseases worldwide owing to its late diagnosis, early metastasis, and poor prognosis. Because current therapeutic options are limited, there is an urgent need to investigate novel targeted treatment strategies. Pancreatic cancer faces significant metabolic challenges, principally hypoxia and nutrient deprivation, due to specific microenvironmental constraints, including an extensive desmoplastic stromal reaction. Pancreatic cancer cells have been shown to rewire their metabolism and energy production networks to support rapid survival and proliferation. Increased glucose uptake and glycolytic pathway activity during this process have been extensively described. However, growing evidence suggests that pancreatic cancer cells are glutamine addicted. As a nitrogen source, glutamine directly (or indirectly via glutamate conversion) contributes to many anabolic processes in pancreatic cancer, including amino acids, nucleobases, and hexosamine biosynthesis. It also plays an important role in redox homeostasis, and when converted to α-ketoglutarate, glutamine serves as an energy and anaplerotic carbon source, replenishing the tricarboxylic acid cycle intermediates. The present study aims to provide a comprehensive overview of glutamine metabolic reprogramming in pancreatic cancer, focusing on potential therapeutic approaches targeting glutamine metabolism in pancreatic cancer.

Bromodomain and extraterminal (BET) proteins: biological functions, diseases, and targeted therapy

BET proteins, which influence gene expression and contribute to the development of cancer, are epigenetic interpreters. Thus, BET inhibitors represent a novel form of epigenetic anticancer treatment. Although preliminary clinical trials have shown the anticancer potential of BET inhibitors, it appears that these drugs have limited effectiveness when used alone. Therefore, given the limited monotherapeutic activity of BET inhibitors, their use in combination with other drugs warrants attention, including the meaningful variations in pharmacodynamic activity among chosen drug combinations. In this paper, we review the function of BET proteins, the preclinical justification for BET protein targeting in cancer, recent advances in small-molecule BET inhibitors, and preliminary clinical trial findings. We elucidate BET inhibitor resistance mechanisms, shed light on the associated adverse events, investigate the potential of combining these inhibitors with diverse therapeutic agents, present a comprehensive compilation of synergistic treatments involving BET inhibitors, and provide an outlook on their future prospects as potent antitumor agents. We conclude by suggesting that combining BET inhibitors with other anticancer drugs and innovative next-generation agents holds great potential for advancing the effective targeting of BET proteins as a promising anticancer strategy.

Targeting SIRT1 synergistically improves the antitumor effect of JQ-1 in hepatocellular carcinoma

Bromodomain and extraterminal domain protein inhibitors have shown therapeutic promise in hepatocellular carcinoma. However, resistance to bromodomain and extraterminal domain protein inhibitors has emerged in preclinical trials, presenting an immense clinical challenge, and the mechanisms are unclear. In this study, we found that overexpression of SIRT1 induced by JQ-1, a bromodomain and extraterminal domain protein inhibitor, may confer resistance to JQ-1 in hepatocellular carcinoma. SIRT1 protein expression was higher in hepatocellular carcinoma tissues than in normal tissues, and this phenotype was correlated with a poor prognosis. Cotreatment with JQ-1 and the SIRT1 inhibitor EX527 synergistically suppressed proliferation and blocked cell cycle progression in hepatocellular carcinoma cells. Combined administration of JQ-1 and EX527 successfully reduced the tumor burden in vivo. In addition, JQ-1 mediated AMPK/p-AMPK axis activation to upregulate SIRT1 protein expression and enhanced autophagy to inhibit cell apoptosis. Activation of AMPK could alleviate the antitumor effect of the combination of JQ-1 and EX527 on hepatocellular carcinoma cells. Furthermore, inhibition of SIRT1 further enhanced the antitumor effect of JQ-1 by blocking protective autophagy in hepatocellular carcinoma. Our study proposes a novel and efficacious therapeutic strategy of a BET inhibitor combined with a SIRT1 inhibitor for hepatocellular carcinoma.

Syk Inhibition Reprograms Tumor-Associated Macrophages and Overcomes Gemcitabine-Induced Immunosuppression in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is an insidious disease with a low 5-year survival rate. PDAC is characterized by infiltration of abundant tumor-associated macrophages (TAM), which promote immune tolerance and immunotherapeutic resistance. Here we report that macrophage spleen tyrosine kinase (Syk) promotes PDAC growth and metastasis. In orthotopic PDAC mouse models, genetic deletion of myeloid Syk reprogrammed macrophages into immunostimulatory phenotype, increased the infiltration, proliferation, and cytotoxicity of CD8+ T cells, and repressed PDAC growth and metastasis. Furthermore, gemcitabine (Gem) treatment induced an immunosuppressive microenvironment in PDAC by promoting protumorigenic polarization of macrophages. In contrast, treatment with the FDA-approved Syk inhibitor R788 (fostamatinib) remodeled the tumor immune microenvironment, "re-educated" protumorigenic macrophages towards an immunostimulatory phenotype and boosted CD8+ T-cell responses in Gem-treated PDAC in orthotopic mouse models and an ex vivo human pancreatic slice culture model. These findings illustrate the potential of Syk inhibition for enhancing the antitumor immune responses in PDAC and support the clinical evaluation of R788 either alone or together with Gem as a potential treatment strategy for PDAC.

SIGNIFICANCE

Syk blockade induces macrophage polarization to an immunostimulatory phenotype, which enhances CD8+ T-cell responses and improves gemcitabine efficacy in pancreatic ductal adenocarcinoma, a clinically challenging malignancy.

The impact of PD-L1 as a biomarker of cancer responses to combo anti-PD-1/CTLA-4

Combination therapy of solid tumors with immune checkpoint inhibitors (ICIs) is a promising and rapidly evolving area of clinical research. Combo nivolumab-ipilimumab therapy has demonstrated potent efficacy in recent years, and PD-L1 expression profile has shown to play a key role in determining the most optimal immunotherapeutic regimen in advanced cancer patients. Here, the focus is over the impact of PD-L1 on combo nivolumab-ipilimumab in advanced solid cancer patients. Interpretations of this review indicate that patient responses to combo nivolumab-ipilimumab can be affected from different levels of PD-L1 expression states. A point required attention is the variations in responses among diverse cancer types or between different doses of the immunotherapy drugs. In general, higher rates of responses are seen with higher PD-L1 expression levels in many cancer types. This, however, is not coincided with survival of patients. Taken all into consideration, it could be asserted that considering PD-L1 as a solo biomarker may not be reliable for predicting clinical efficacy of combo nivolumab-ipilimumab. Thus, a search for other biomarkers or combination of PD-L1 with other factors may be considered for predicting patient responses.

Therapeutic Targeting of MYC in Head and Neck Squamous Cell Carcinoma

MYC plays critical roles in tumorigenesis and is considered an attractive cancer therapeutic target. Small molecules that directly target MYC and are well tolerated in vivo represent invaluable anti-cancer therapeutic agents. Here, we aimed to investigate the therapeutic effect of MYC inhibitors in head and neck squamous cell carcinoma (HNSCC). The results showed that pharmacological and genetic inhibition of MYC inhibited HNSCC proliferation and migration. MYC inhibitor 975 (MYCi975), inhibited HNSCC growth in both cell line-derived xenograft and syngeneic murine models. MYC inhibition also induced tumor cell-intrinsic immune responses, and promoted CD8⁺ T cell infiltration. Mechanistically, MYC inhibition increased CD8⁺ T cell-recruiting chemokines by inducing the DNA damage related cGAS-STING pathway. High expression of MYC combined with a low level of infiltrated CD8⁺ T cell in HNSCC correlated with poor prognosis. These results suggested the potential of small-molecule MYC inhibitors as anti-cancer therapeutic agents in HNSCC.

Target c-Myc to treat pancreatic cancer

C-Myc overexpression is a common finding in pancreatic cancer and predicts the aggressive behavior of cancer cells. It binds to the promoter of different genes, thereby regulating their transcription. C-Myc is downstream of KRAS and interacts with several oncogenic and proliferative pathways in pancreatic cancer. C-Myc enhances aerobic glycolysis in cancer cells and regulates glutamate biosynthesis from glutamine. It provides enough energy for cancer cells' metabolism and sufficient substrate for the synthesis of organic molecules. C-Myc overexpression is associated with chemoresistance, intra-tumor angiogenesis, epithelial-mesenchymal transition (EMT), and metastasis in pancreatic cancer. Despite its title, c-Myc is not "undruggable" and recent studies unveiled that it can be targeted, directly or indirectly. Small molecules that accelerate c-Myc ubiquitination and degradation have been effective in preclinical studies. Small molecules that hinder c-Myc-MAX heterodimerization or c-Myc/MAX/DNA complex formation can functionally inhibit c-Myc. In addition, c-Myc can be targeted through transcriptional, post-transcriptional, and translational modifications.

Inhibition of MYC suppresses programmed cell death ligand-1 expression and enhances immunotherapy in triple-negative breast cancer

BACKGROUND

Cancer immunotherapy has emerged as a promising strategy against triple-negative breast cancer (TNBC). One of the immunosuppressive pathways involves programmed cell death-1 (PD-1) and programmed cell death ligand-1 (PD-L1), but many patients derived little benefit from PD-1/PD-L1 checkpoint blockades treatment. Prior research has shown that MYC, a master transcription amplifier highly expressed in TNBC cells, can regulate the tumor immune microenvironment and constrain the efficacy of immunotherapy. This study aims to investigate the regulatory relationship between MYC and PD-L1, and whether a cyclin-dependent kinase (CDK) inhibitor that inhibits MYC expression in combination with anti-PD-L1 antibodies can enhance the response to immunotherapy.

METHODS

Public databases and TNBC tissue microarrays were used to study the correlation between MYC and PD-L1. The expression of MYC and PD-L1 in TNBCs was examined by quantitative real-time polymerase chain reaction and Western blotting. A patient-derived tumor xenograft (PDTX) model was used to evaluate the influence of a CDK7 inhibitor THZ1 on PD-L1 expression. Cell proliferation and migration were detected by 5-ethynyl-2'-deoxyuridine (EdU) cell proliferation and cell migration assays. Tumor xenograft models were established for in vivo verification.

RESULTS

A high MYC expression level was associated with a poor prognosis and could alter the proportion of tumor-infiltrating immune cells (TIICs). The positive correlation between MYC and PD-L1 was confirmed by immunostaining samples from 165 TNBC patients. Suppression of MYC in TNBC caused a reduction in the levels of both PD-L1 messenger RNA and protein. In addition, antitumor immune response was enhanced in the TNBC cancer xenograft mouse model with suppression of MYC by CDK7 inhibitor THZ1.

CONCLUSIONS

The combined therapy of CDK7 inhibitor THZ1 and anti-PD-L1 antibody appeared to have a synergistic effect, which might offer new insight for enhancing immunotherapy in TNBC.

Tumor immune checkpoints and their associated inhibitors

Immunological evasion is one of the defining characteristics of cancers, as the immune modification of an immune checkpoint (IC) confers immune evasion capabilities to tumor cells. Multiple ICs, such as programmed cell death protein-1 (PD-1) and cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4), can bind to their respective receptors and reduce tumor immunity in a variety of ways, including blocking immune cell activation signals. IC blockade (ICB) therapies targeting these checkpoint molecules have demonstrated significant clinical benefits. This is because antibody-based IC inhibitors and a variety of specific small molecule inhibitors can inhibit key oncogenic signaling pathways and induce durable tumor remission in patients with a variety of cancers. Deciphering the roles and regulatory mechanisms of these IC molecules will provide crucial theoretical guidance for clinical treatment. In this review, we summarize the current knowledge on the functional and regulatory mechanisms of these IC molecules at multiple levels, including epigenetic regulation, transcriptional regulation, and post-translational modifications. In addition, we provide a summary of the medications targeting various nodes in the regulatory pathway, and highlight the potential of newly identified IC molecules, focusing on their potential implications for cancer diagnostics and immunotherapy.

The BET Protein Inhibitor JQ1 Decreases Hypoxia and Improves the Therapeutic Benefit of Anti-PD-1 in a High-Risk Neuroblastoma Mouse Model

Anti-programmed death 1 (PD-1) is a revolutionary treatment for many cancers. The response to anti-PD-1 relies on several properties of tumor and immune cells, including the expression of PD-L1 and PD-1. Despite the impressive clinical benefit achieved with anti-PD-1 in several cancers in adults, the use of this therapy for high-risk neuroblastoma remains modest. Here, we evaluated the therapeutic benefit of anti-PD-1 in combination with JQ1 in a highly relevant TH-MYCN neuroblastoma transgenic mouse model. JQ1 is a small molecule inhibitor of the extra-terminal domain (BET) family of bromodomain proteins, competitively binding to bromodomains. Using several neuroblastoma cell lines in vitro, we showed that JQ1 inhibited hypoxia-dependent induction of HIF-1α and decreased the expression of the well-known HIF-1α downstream target gene CA9. Using MRI relaxometry performed on TH-MYCN tumor-bearing mice, we showed that JQ1 decreases R2* in tumors, a parameter associated with intra-tumor hypoxia in pre-clinical settings. Decreasing hypoxia by JQ1 was associated with improved blood vessel quality and integrity, as revealed by CD31 and αSMA staining on tumor sections. By analyzing the immune landscape of TH-MYCN tumors in mice, we found that JQ1 had no major impact on infiltrating immune cells into the tumor microenvironment but significantly increased the percentage of CD8⁺ PD-1⁺, conventional CD4⁺ PD-1⁺, and Treg PD-1⁺ cells. While anti-PD-1 monotherapy did not affect TH-MYCN tumor growth, we showed that combinatorial therapy associating JQ1 significantly decreased the tumor volume and improved the therapeutic benefit of anti-PD-1. This study provided the pre-clinical proof of concept needed to establish a new combination immunotherapy approach that may create tremendous enthusiasm for treating high-risk childhood neuroblastoma.

Pancreatic ductal adenocarcinoma: Emerging therapeutic strategies

The seventh leading cause of cancer-related death globally, pancreatic ductal adenocarcinoma (PDAC) involves the exocrine pancreas and constitutes greater than 90% of all pancreatic cancers. Surgical resection in combination with systemic chemotherapy with or without radiation remains the mainstay of treatment and the only potentially curative treatment option. While there has been improvement in systemic chemotherapy, long-term survival among patients with PDAC remains poor. Improvement in the understanding of tumorigenesis, genetic mutations, the tumor microenvironment (TME), immunotherapies, as well as targeted therapies continued to drive advances in PDAC treatment. We herein review the TME, genetic landscape, as well as various metabolic pathways associated with PDAC tumorigenesis relative to emerging therapies.

MYC inhibition reprograms tumor immune microenvironment by recruiting T lymphocytes and activating the CD40/CD40L system in osteosarcoma

The efficacy of immune checkpoint blockade (ICB) therapy depends on sufficient infiltration and activation of primed tumor-specific cytotoxic T lymphocytes (CTLs) in the tumor microenvironment. However, many tumor types, including osteosarcoma, mainly display immune-desert or immune-excluded phenotypes, which are characterized by a lack of tumor-infiltrating lymphocytes and a poor response to ICB monotherapy. Thus, novel therapeutic strategies are urgently needed to surmount these obstacles. In this study, we found that the expression of the c-Myc oncogene is negatively correlated with the T cell infiltration rate in osteosarcoma. Pharmacological inhibition of c-Myc with JQ-1 significantly reduced tumor burden and improved overall survival in an immunocompetent syngeneic murine model of osteosarcoma (K7M2). A mechanistic study revealed that JQ-1 administration dramatically reprogrammed the tumor immune microenvironment (TIME) within K7M2 tumors. On the one hand, JQ-1 can promote T cell trafficking into tumors by increasing the expression and secretion of T cell-recruiting chemokines. On the other hand, JQ-1 is capable of facilitating crosstalk between antigen-presenting dendritic cells and T cells through the CD40/CD40L costimulatory pathway, leading to activation of tumor-specific CTLs. Combined treatment with anti-PD-1 antibody and JQ-1 resulted in more pronounced tumor regression than either monotherapy, showing an obvious synergistic effect. These findings uncover for the first time that c-Myc inhibition can promote T cell infiltration and activation in osteosarcoma in multiple ways, delivering a one-two punch for modulating TIME. The present work also provides the basis for establishing c-Myc inhibitor and ICB coadministration as a novel therapeutic regimen for patients with osteosarcoma.

Precision Medicine for BRCA/PALB2-Mutated Pancreatic Cancer and Emerging Strategies to Improve Therapeutic Responses to PARP Inhibition

Simple Summary

For the small subset of pancreatic ductal adenocarcinoma (PDAC) patients with loss-of-function mutations to BRCA1/2 or PALB2, both first-line and maintenance therapy differs significantly. These mutations confer a loss of double-strand break DNA homologous recombination (HR), substantially altering drug sensitivities. In this review, we discuss the current treatment guidelines for PDAC tumors deficient in HR, as well as newly emerging strategies to improve drug responses in this population. We also highlight additional patient populations in which these strategies may also be effective, and novel strategies aiming to confer similar drug sensitivity to tumors proficient in HR repair.

Abstract

Pancreatic cancer is projected to become the second leading cause of cancer-related death by 2030. As patients typically present with advanced disease and show poor responses to broad-spectrum chemotherapy, overall survival remains a dismal 10%. This underscores an urgent clinical need to identify new therapeutic approaches for PDAC patients. Precision medicine is now the standard of care for several difficult-to-treat cancer histologies. Such approaches involve the identification of a clinically actionable molecular feature, which is matched to an appropriate targeted therapy. Selective poly (ADP-ribose) polymerase (PARP) inhibitors such as Niraparib, Olaparib, Talazoparib, Rucaparib, and Veliparib are now approved for several cancers with loss of high-fidelity double-strand break homologous recombination (HR), namely those with deleterious mutations to BRCA1/2, PALB2, and other functionally related genes. Recent evidence suggests that the presence of such mutations in pancreatic ductal adenocarcinoma (PDAC), the most common and lethal pancreatic cancer histotype, significantly alters drug responses both with respect to first-line chemotherapy and maintenance therapy. In this review, we discuss the current treatment paradigm for PDAC tumors with confirmed deficits in double-strand break HR, as well as emerging strategies to both improve responses to PARP inhibition in HR-deficient PDAC and confer sensitivity to tumors proficient in HR repair.

Tumor-associated macrophages promote PD-L1 expression in tumor cells by regulating PKM2 nuclear translocation in pancreatic ductal adenocarcinoma

In many types of cancer, tumor cells prefer to use glycolysis as a major energy acquisition method. Here, we found that the 18fluoro-deoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT)-based markers were positively associated with the expression of programmed cell death ligand 1 (PD-L1), pyruvate kinase M2 (PKM2), both of which indicate poor prognosis in patients with pancreatic ductal adenocarcinoma (PDAC). However, the regulatory mechanism of PD-L1 remains elusive. In this study, we confirmed that transforming growth factor-beta1 (TGF-β1) secreted by tumor-associated macrophages (TAMs) was a key factor contributing to the expression of PD-L1 in PDAC cells by inducing the nuclear translocation of PKM2. Using co-immunoprecipitation and chromatin immunoprecipitation assays, we demonstrated that the interaction between PKM2 and signal transducer and activator of transcription 1 (STAT1) was enhanced by TGF-β1 stimulation, which facilitated the transactivation of PD-L1 by the binding of PKM2 and STAT1 to its promoter. In vivo, PKM2 knockdown decreased PD-L1 expression in PDAC cells and inhibited tumor growth partly by promoting natural killer cell activation and function, and the combination of PD-1/PD-L1 blockade with PKM2 knockdown limited tumor growth. In conclusion, PKM2 significantly contributes to TAM-induced PD-L1 overexpression and immunosuppression, providing a novel target for immunotherapies for PDAC.

XP-524 is a dual-BET/EP300 inhibitor that represses oncogenic KRAS and potentiates immune checkpoint inhibition in pancreatic cancer

There are currently no effective treatments for pancreatic ductal adenocarcinoma (PDAC), which displays widespread resistance to chemotherapy, radiation therapy, and immunotherapy. Here, we demonstrate that the multispecificity BET/EP300 inhibitor XP-524 has pronounced single-agent efficacy in vitro, in vivo, and in ex vivo human PDAC slice cultures, functioning in part by attenuating oncogenic KRAS signaling. In vivo XP-524 led to extensive reprogramming of the pancreatic tumor microenvironment, sensitizing murine carcinoma to immune checkpoint inhibition and further extending survival. Given the urgent need for therapeutic approaches in PDAC, the combination of XP-524 and immune checkpoint inhibition warrants additional exploration.

Pancreatic ductal adenocarcinoma (PDAC) is associated with extensive dysregulation of the epigenome and epigenetic regulators, such as bromodomain and extraterminal motif (BET) proteins, have been suggested as potential targets for therapy. However, single-agent BET inhibition has shown poor efficacy in clinical trials, and no epigenetic approaches are currently used in PDAC. To circumvent the limitations of the current generation of BET inhibitors, we developed the compound XP-524 as an inhibitor of the BET protein BRD4 and the histone acetyltransferase EP300/CBP, both of which are ubiquitously expressed in PDAC tissues and cooperate to enhance tumorigenesis. XP-524 showed increased potency and superior tumoricidal activity than the benchmark BET inhibitor JQ-1 in vitro, with comparable efficacy to higher-dose JQ-1 combined with the EP300/CBP inhibitor SGC-CBP30. We determined that this is in part due to the epigenetic silencing of KRAS in vitro, with similar results observed using ex vivo slice cultures of human PDAC tumors. Accordingly, XP-524 prevented KRAS-induced, neoplastic transformation in vivo and extended survival in two transgenic mouse models of aggressive PDAC. In addition to the inhibition of KRAS/MAPK signaling, XP-524 also enhanced the presentation of self-peptide and tumor recruitment of cytotoxic T lymphocytes, though these lymphocytes remained refractory from full activation. We, therefore, combined XP-524 with an anti–PD-1 antibody in vivo, which reactivated the cytotoxic immune program and extended survival well beyond XP-524 in monotherapy. Pending a comprehensive safety evaluation, these results suggest that XP-524 may benefit PDAC patients and warrant further exploration, particularly in combination with immune checkpoint inhibition.

The MYC oncogene - the grand orchestrator of cancer growth and immune evasion

The MYC proto-oncogenes encode a family of transcription factors that are among the most commonly activated oncoproteins in human neoplasias. Indeed, MYC aberrations or upregulation of MYC-related pathways by alternate mechanisms occur in the vast majority of cancers. MYC proteins are master regulators of cellular programmes. Thus, cancers with MYC activation elicit many of the hallmarks of cancer required for autonomous neoplastic growth. In preclinical models, MYC inactivation can result in sustained tumour regression, a phenomenon that has been attributed to oncogene addiction. Many therapeutic agents that directly target MYC are under development; however, to date, their clinical efficacy remains to be demonstrated. In the past few years, studies have demonstrated that MYC signalling can enable tumour cells to dysregulate their microenvironment and evade the host immune response. Herein, we discuss how MYC pathways not only dictate cancer cell pathophysiology but also suppress the host immune response against that cancer. We also propose that therapies targeting the MYC pathway will be key to reversing cancerous growth and restoring antitumour immune responses in patients with MYC-driven cancers.

Large cell morphology, CMYC+ tumour cells, and PD-1+ tumour cell/intense PD-L1+ cell reactions are important prognostic factors in nodal peripheral T-cell lymphomas with T follicular helper markers

BACKGROUND

The clinicopathological characteristics and prognostic factors in nodal peripheral T-cell lymphomas (PTCLs) with two or more T follicular helper markers (TFH+) are not adequately investigated.

METHODS

Immunohistologically, we selected 22 patients with TFH+ lymphoma (PTCL-TFH) in 47 of PTCL-not otherwise specified (NOS), and subclassified into large and small cell groups. We compared the two groups with 39 angioimmunoblastic T-cell lymphoma (AITL) and seven follicular T-cell lymphoma (F-TCL) patients. Prognostic factors were analysed by overall survival in patients with three types of TFH+ PTCLs.

RESULTS

Thirteen large cell and nine small cell PTCL-TFH patients had more than two TFH markers including programmed cell death-1 (PD-1). Large cell PTCL-TFH showed frequent CMYC expression in 10 patients (77%), and four of 11 large cell group (36%) had somatic RHOA G17V gene mutation by Sanger sequencing. Large cell PTCL-TFH patients showed significantly worse prognosis than those of the small cell group, AITL, and F-TCL (p < 0.05). In TFH+ PTCLs, CMYC+ tumour cells, and combined PD-1 ligand 1 (PD-L1) + tumour cells and intense reaction of PD-L1+ non-neoplastic cells (high PD-L1+ cell group) were significantly poor prognostic factors (p < 0.05). Combinations of CMYC+ or PD-1+ tumour cells and high PD-L1+ cell group indicated significantly poor prognosis (p < 0.01).

CONCLUSION

Large cell PTCL-TFH indicated poor prognosis in TFH+ PTCLs. These data suggested that CMYC+ tumour cells and intense PD-L1+ cell reaction influenced tumour cell progression in TFH+ PTCLs, and PD-1+ tumour cell/intense PD-L1+ cell reactions may play a role in immune evasion.

Mechanisms of Cancer Cell Death: Therapeutic Implications for Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a type of cancer that is strongly associated with poor prognosis and short median survival times. In stark contrast to the progress seen in other cancer types in recent decades, discoveries of new treatments in PDAC have been few and far between and there has been little improvement in overall survival (OS). The difficulty in treating this disease is multifactorial, contributed to by late presentation, difficult access to primary tumour sites, an 'immunologically cold' phenotype, and a strong tendency of recurrence likely driven by cancer stem cell (CSC) populations. Furthermore, apparently contrasting roles of tumour components (such as fibrotic stroma) and intracellular pathways (such as autophagy and TGFβ) have made it difficult to distinguish beneficial from detrimental drug targets. Despite this, progress has been made in the field, including the determination of mFOLFIRINOX as the standard-of-care adjuvant therapy and the discovery of KRASG12C mutant inhibitors. Moreover, new research, as outlined in this review, has highlighted promising new approaches including the targeting of the tumour microenvironment, enhancement of immunotherapies, epigenetic modulation, and destruction of CSCs.

Combinational blockade of MET and PD-L1 improves pancreatic cancer immunotherapeutic efficacy

BACKGROUND

Dysregulated expression and activation of receptor tyrosine kinases (RTKs) are associated with a range of human cancers. However, current RTK-targeting strategies exert little effect on pancreatic cancer, a highly malignant tumor with complex immune microenvironment. Given that immunotherapy for pancreatic cancer still remains challenging, this study aimed to elucidate the prognostic role of RTKs in pancreatic tumors with different immunological backgrounds and investigate their targeting potential in pancreatic cancer immunotherapy.

METHODS

Kaplan-Meier plotter was used to analyze the prognostic significance of each of the all-known RTKs to date in immune "hot" and "cold" pancreatic cancers. Gene Expression Profiling Interactive Analysis-2 was applied to assess the differential expression of RTKs between pancreatic tumors and normal pancreatic tissues, as well as its correlation with immune checkpoints (ICPs). One hundred and fifty in-house clinical tissue specimens of pancreatic cancer were collected for expression and correlation validation via immunohistochemical analysis. Two pancreatic cancer cell lines were used to demonstrate the regulatory effects of RTKs on ICPs by biochemistry and flow cytometry. Two in vivo models bearing pancreatic tumors were jointly applied to investigate the combinational regimen of RTK inhibition and immune checkpoint blockade for pancreatic cancer immunotherapy.

RESULTS

MET was identified as a pancreatic cancer-specific RTK, which is significantly associated with prognosis in both immune "hot" and "cold" pancreatic cancers. MET was observed to be highly upregulated in pancreatic cancer tissues, and positively correlated with PD-L1 levels. Elevated MET and PD-L1 expressions were closely associated with lymph node metastasis, tumor TNM stage, and overall survival in pancreatic cancer. Mechanistically, MET could interact with PD-L1, and maintain its expression level in multiple ways. MET deficiency was found to facilitate lymphocyte infiltration into pancreatic tumors. Finally, significant benefits of combining MET inhibition with PD-1/PD-L1 blockage were verified in both orthotopic and subcutaneous mouse models of pancreatic cancer.

CONCLUSIONS

This study systematically investigated the potential effectiveness of a novel pancreatic cancer immunotherapy targeting RTKs, and revealed the function of MET in PD-L1 regulation as well as the combined therapeutic efficacy of MET and PD-L1 in pancreatic cancer.

The Role of Oncogenes and Redox Signaling in the Regulation of PD-L1 in Cancer

Tumor cells can evade the immune system via multiple mechanisms, including the dysregulation of the immune checkpoint signaling. These signaling molecules are important factors that can either stimulate or inhibit tumor immune response. Under normal physiological conditions, the interaction between programmed cell death ligand 1 (PD-L1) and its receptor, programmed cell death 1 (PD-1), negatively regulates T cell function. In cancer cells, high expression of PD-L1 plays a key role in cancer evasion of the immune surveillance and seems to be correlated with clinical response to immunotherapy. As such, it is important to understand various mechanisms by which PD-L1 is regulated. In this review article, we provide an up-to-date review of the different mechanisms that regulate PD-L1 expression in cancer. We will focus on the roles of oncogenic signals (c-Myc, EML4-ALK, K-ras and p53 mutants), growth factor receptors (EGFR and FGFR), and redox signaling in the regulation of PD-L1 expression and discuss their clinical relevance and therapeutic implications. These oncogenic signalings have common and distinct regulatory mechanisms and can also cooperatively control tumor PD-L1 expression. Finally, strategies to target PD-L1 expression in tumor microenvironment including combination therapies will be also discussed.

The BET Inhibitor JQ1 Augments the Antitumor Efficacy of Gemcitabine in Preclinical Models of Pancreatic Cancer

Gemcitabine is used to treat pancreatic cancer (PC), but is not curative. We sought to determine whether gemcitabine + a BET bromodomain inhibitor was superior to gemcitabine, and identify proteins that may contribute to the efficacy of this combination. This study was based on observations that cell cycle dysregulation and DNA damage augment the efficacy of gemcitabine. BET inhibitors arrest cells in G1 and allow increases in DNA damage, likely due to inhibition of expression of DNA repair proteins Ku80 and RAD51. BET inhibitors (JQ1 or I-BET762) + gemcitabine were synergistic in vitro, in Panc1, MiaPaCa2 and Su86 PC cell lines. JQ1 + gemcitabine was more effective in vivo than either drug alone in patient-derived xenograft models (P < 0.01). Increases in the apoptosis marker cleaved caspase 3 and DNA damage marker γH2AX paralleled antitumor efficacy. Notably, RNA-seq data showed that JQ1 + gemcitabine selectively inhibited HMGCS2 and APOC1 ~6-fold, compared to controls. These proteins contribute to cholesterol biosynthesis and lipid metabolism, and their overexpression supports tumor cell proliferation. IPA data indicated that JQ1 + gemcitabine selectively inhibited the LXR/RXR activation pathway, suggesting the hypothesis that this inhibition may contribute to the observed in vivo efficacy of JQ1 + gemcitabine.

Regulatory mechanisms of immune checkpoints PD-L1 and CTLA-4 in cancer

The cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4)/B7 and programmed death 1 (PD-1)/ programmed cell death-ligand 1 (PD-L1) are two most representative immune checkpoint pathways, which negatively regulate T cell immune function during different phases of T-cell activation. Inhibitors targeting CTLA-4/B7 and PD1/PD-L1 pathways have revolutionized immunotherapies for numerous cancer types. Although the combined anti-CTLA-4/B7 and anti-PD1/PD-L1 therapy has demonstrated promising clinical efficacy, only a small percentage of patients receiving anti-CTLA-4/B7 or anti-PD1/PD-L1 therapy experienced prolonged survival. Regulation of the expression of PD-L1 and CTLA-4 significantly impacts the treatment effect. Understanding the in-depth mechanisms and interplays of PD-L1 and CTLA-4 could help identify patients with better immunotherapy responses and promote their clinical care. In this review, regulation of PD-L1 and CTLA-4 is discussed at the levels of DNA, RNA, and proteins, as well as indirect regulation of biomarkers, localization within the cell, and drugs. Specifically, some potential drugs have been developed to regulate PD-L1 and CTLA-4 expressions with high efficiency.

MYC oncogene is associated with suppression of tumor immunity and targeting Myc induces tumor cell immunogenicity for therapeutic whole cell vaccination

Background

MYC oncogene is deregulated in 70% of all human cancers and is associated with multiple oncogenic functions including immunosuppression in the tumor microenvironment. The role of MYC in the immune microenvironment of neuroblastoma and melanoma is investigated and the effect of targeting Myc on immunogenicity of cancer cells is evaluated.

Methods

Immune cell infiltrates and immunogenic pathway signatures in the context of MYCN amplification were analyzed in human neuroblastoma tumors and in metastatic melanoma. Dose response and cell susceptibility to MYC inhibitors (I-BET726 and JQ1) were determined in mouse cell lines. The influence of downregulating Myc in tumor cells was characterized by immunogenic pathway signatures and functional assays. Myc-suppressed tumor cells were used as whole cell vaccines in preclinical neuroblastoma and melanoma models.

Results

Analysis of immune phenotype in human neuroblastoma and melanoma tumors revealed that MYCN or c-MYC amplified tumors respectively are associated with suppressed immune cell infiltrates and functional pathways. Targeting Myc in cancer cells with I-BET726 and JQ1 results in cell cycle arrest and induces cell immunogenicity. Combining vaccination of Myc-inhibited tumor cells with checkpoint inhibition induced robust antitumor immunity and resulted in therapeutic cancer vaccine therapy in mouse neuroblastoma tumors. Despite vigorous antitumor immunity in the mouse melanoma model, upregulation of immunosuppressive pathways enabled tumor escape.

Conclusions

This study demonstrates that the Myc oncogene is an appropriate target for inducing tumor cell immunogenicity and suggests that Myc-suppressed whole tumor cells combined with checkpoint therapy could be used for formulating a personalized therapeutic tumor vaccine.

Pancreatic Cancer Stem-Like Cells With High Calreticulin Expression Associated With Immune Surveillance

OBJECTIVE

Pancreatic cancer stem-like cells (P-CSLCs) are thought to be associated with poor prognosis. Previously, we used proteomic analysis to identify a chaperone pro-phagocytic protein calreticulin (CALR) as a P-CSLC-specific protein. This study aimed to investigate the association between CALR and P-CSLC.

METHODS

PANC-1-Lm cells were obtained as P-CSLCs from a human pancreatic cancer cell line, PANC-1, using a sphere induction medium followed by long-term cultivation on laminin. To examine the cancer stem cell properties, subcutaneous injection of the cells into immune-deficient mice and sphere formation assay were performed. Cell surface expression analysis was performed using flow cytometry.

RESULTS

PANC-1-Lm showed an increased proportion of cell surface CALR-positive and side-population fractions compared with parental cells. PANC-1-Lm cells also had higher frequency of xenograft tumor growth and sphere formation than PANC-1 cells. Moreover, sorted CALRhigh cells from PANC-1-Lm had the highest sphere formation frequency among tested cells. Interestingly, the number of programmed death-ligand 1-positive cells among CALRhigh cells was increased as well, whereas that of human leukocyte antigen class I-positive cells decreased.

CONCLUSION

In addition to the cancer stem cell properties, the P-CSLC, which showed elevated CALR expression on the cell surface, might be associated with evasion of immune surveillance.

Trials and tribulations of pancreatic cancer immunotherapy

Immunotherapy has revolutionized cancer treatment in the last decade, and strategies to re-activate cytotoxic immunity are now standard of care in several malignancies. Despite rapid advances in immunotherapy for most solid cancers, progress in immunotherapy against pancreatic ductal adenocarcinoma (PDAC) has been exceptionally difficult. This is true for several approaches, most notably immune checkpoint inhibitors (ICIs) and GM-CSF cell-based vaccines (GVAX). Though many immunotherapies have been explored in clinical trials, few have shown significant therapeutic efficacy. Further, many have shown high rates of serious adverse effects and dose-limiting toxicities, and to date, immunotherapy regimens have not been successfully implemented in PDAC. Here, we provide a comprehensive summary of the key clinical trials exploring immunotherapy in PDAC, followed by a brief discussion of emerging molecular mechanisms that may explain the relative failure of immunotherapy in pancreas cancer thus far.

Prognostic significance and therapeutic potential of the immune checkpoint VISTA in pancreatic cancer

OBJECTIVE

V-domain Ig suppressor of T cell activation (VISTA) is a novel immune checkpoint protein that belongs to the B7 family. The aim of this study was to investigate the prognostic significance and therapeutic potential of VISTA in patients with pancreatic cancer.

METHODS

Using immunohistochemistry (IHC), we examined the expression of VISTA and demonstrated the associations between the VISTA and overall survival in 223 PDAC patients from 2 different unrelated retrospective cohorts. The multiplex immunofluorescence was performed to illuminate the relationship between VISTA expression and tumor-infiltrating immune cell subclusters of PDAC. We also verified the findings in The Cancer Genome Atlas (TCGA) dataset. The anti-tumor effect of anti-VISTA therapy was studied by the mouse model with liver metastases of PDAC.

RESULTS

The VISTA protein was highly expressed in 25.6% of tumor cells (TCs), 38.1% of immune cells, and 26.0% of endothelial cells in 223 PDAC tumor tissues. VISTA expression in TCs was significantly associated with prolonged overall survival. Multiplex immunofluorescence analysis revealed that VISTA level was positively correlated with CD68+ macrophages, CD3+ T cells, and CD19+ B cells in PDAC. However, a higher expression level of VISTA was detected in tumor-infiltrating CD68+ macrophages than in CD3+ T and CD19+ B cells. Furthermore, anti-VISTA antibody treatment significantly reduced the number of metastatic nodules in livers of mouse models of PDAC with liver metastases.

CONCLUSION

VISTA expressed in TCs is associated with a favorable prognosis in PDAC. Moreover, immunotherapy with anti-VISTA antibodies may potentially be an effective treatment strategy against PDAC.

Regulation of PD-L1 expression in the tumor microenvironment

Programmed death-ligand 1 (PD-L1) on cancer cells engages with programmed cell death-1 (PD-1) on immune cells, contributing to cancer immune escape. For multiple cancer types, the PD-1/PD-L1 axis is the major speed-limiting step of the anti-cancer immune response. In this context, blocking PD-1/PD-L1 could restore T cells from exhausted status and eradicate cancer cells. However, only a subset of PD-L1 positive patients benefits from α-PD-1/PD-L1 therapies. Actually, PD-L1 expression is regulated by various factors, leading to the diverse significances of PD-L1 positivity. Understanding the mechanisms of PD-L1 regulation is helpful to select patients and enhance the treatment effect. In this review, we focused on PD-L1 regulators at the levels of transcription, post-transcription, post-translation. Besides, we discussed the potential applications of these laboratory findings in the clinic.

Tumor immunological phenotype signature-based high-throughput screening for the discovery of combination immunotherapy compounds

Combination immunotherapy is promising to overcome the limited objective response rates of immune checkpoint blockade (ICB) therapy. Here, a tumor immunological phenotype (TIP) gene signature and high-throughput sequencing-based high-throughput screening (HTS2) were combined to identify combination immunotherapy compounds. We firstly defined a TIP gene signature distinguishing "cold" tumors from "hot" tumors. After screening thousands of compounds, we identified that aurora kinase inhibitors (AKIs) could reprogram the expression pattern of TIP genes in triple-negative breast cancer (TNBC) cells. AKIs treatments up-regulate expression of chemokine genes CXCL10 and CXCL11 through inhibiting aurora kinase A (AURKA)-signal transducer and activator of transcription 3 (STAT3) signaling pathway, which promotes effective T cells infiltrating into tumor microenvironment and improves anti-programmed cell death 1 (PD-1) efficacy in preclinical models. Our study established a novel strategy to discover combination immunotherapy compounds and suggested the therapeutic potential of combining AKIs with ICB for the treatment of TNBC.

Impact of MYC on Anti-Tumor Immune Responses in Aggressive B Cell Non-Hodgkin Lymphomas: Consequences for Cancer Immunotherapy

Simple Summary

The human immune system has several mechanisms to attack and eliminate lymphomas. However, the MYC oncogene is thought to facilitate escape from this anti-tumor immune response. Since patients with MYC overexpressing lymphomas face a significant dismal prognosis after treatment with standard immunochemotherapy, understanding the role of MYC in regulating the anti-tumor immune response is highly relevant. In this review, we describe the mechanisms by which MYC attenuates the anti-tumor immune responses in B cell non-Hodgkin lymphomas. We aim to implement this knowledge in the deployment of novel immunotherapeutic approaches. Therefore, we also provide a comprehensive overview of current immunotherapeutic options and we discuss potential future treatment strategies for MYC overexpressing lymphomas.

Abstract

Patients with MYC overexpressing high grade B cell lymphoma (HGBL) face significant dismal prognosis after treatment with standard immunochemotherapy regimens. Recent preclinical studies indicate that MYC not only contributes to tumorigenesis by its effects on cell proliferation and differentiation, but also plays an important role in promoting escape from anti-tumor immune responses. This is of specific interest, since reversing tumor immune inhibition with immunotherapy has shown promising results in the treatment of both solid tumors and hematological malignancies. In this review, we outline the current understanding of impaired immune responses in B cell lymphoid malignancies with MYC overexpression, with a particular emphasis on diffuse large B cell lymphoma. We also discuss clinical consequences of MYC overexpression in the treatment of HGBL with novel immunotherapeutic agents and potential future treatment strategies.

Turning up the heat on non-immunoreactive tumours: opportunities for clinical development

Notable advances have been achieved in the treatment of cancer since the advent of immunotherapy, and immune checkpoint inhibitors have shown clinical benefit across a wide variety of tumour types. Nevertheless, most patients still progress on these treatments, highlighting the importance of unravelling the underlying mechanisms of primary resistance to immunotherapy. A well described biomarker of non-responsiveness to immune checkpoint inhibitors is the absence or low presence of lymphocytes in the tumour microenvironment, so-called cold tumours. There are five mechanisms of action that have the potential to turn cold tumours into so-called hot and inflamed tumours, hence increasing the tumour's responsiveness to immunotherapy-increasing local inflammation, neutralising immunosuppression at the tumour site, modifying the tumour vasculature, targeting the tumour cells themselves, or increasing the frequency of tumour-specific T cells. In this Review, we discuss preclinical data that serves as the basis for ongoing immunotherapy clinical trials for the treatment of non-immunoreactive tumours, as well as reviewing clinical and translational data where available. We explain how improving our understanding of the underlying mechanisms of primary resistance to immunotherapy will help elucidate an increasingly granular view of the tumour microenvironment cellular composition, functional status, and cellular localisation, with the goal of further therapy refinement.

Future of immune checkpoint inhibitors: focus on tumor immune microenvironment

Immunotherapy has become a powerful clinical strategy in cancer treatment. Immune checkpoint inhibitors (ICIs) have opened a new era for cancer immunotherapy. Nowadays, the number of immunotherapy drug approvals has increased, with numerous treatment options in clinical and preclinical development. However, there remain some obstacles to improve the efficacy of ICIs further. The tumor immune microenvironment (TIME) consists of cancer cell, immune cells and cytokines, et cetera. The dynamics of TIME determine the efficacies of ICIs. Although the ICIs showed manageable toxicity, immune-related adverse effects (irAEs) are still unignorable for clinicians. Since some primary resistance mechanisms exist in TIME, ICIs can only show effects in individual cancer patients. Even for the patients who responded, acquired resistance will occur to neutralize the effect of ICIs. Understanding how to increase the response rates and overcome the resistance to various classes of ICIs is the key to improving clinical efficacy. Besides the novel ICIs in development, there are some approaches to establish combination therapies are underway to improve further the efficacies of ICIs in treating cancer patients. Here, we describe the complicated TIME and state quo of ICIs to prospect the future of ICIs in cancer treatment.

High-dimensional single-cell analysis delineates radiofrequency ablation induced immune microenvironmental remodeling in pancreatic cancer

Radiofrequency ablation (RFA) is an effective local therapy approach for treating solitary tumor of many types of malignancy. The impact of RFA on the tumor immune microenvironment on distant tumors after RFA treatment is still unclear. In this study, by using syngeneic tumor models and single-cell RNA and T-cell receptor sequencing, we have investigated the alterations of tumor-infiltrating immune cells in distant non-RFA tumors. Single-cell RNA sequencing identified six distinct lymphoid clusters, five distinct monocyte/macrophage clusters, three dendritic cells clusters, and one cluster of neutrophils. We found that RFA treatment reduced the proportions of immunosuppressive cells including regulatory T cells, tumor-associated macrophages and tumor-associated neutrophils, whereas increased the percentages of functional T cells in distant non-RFA tumors. Moreover, RFA treatment also altered gene expressions in single-cell level in each cell cluster. By using pseudo-time analysis, we have described the biological processes of tumor-infiltrating CD8+ T cells and monocytes/macrophages based on the transcriptional profiles. In addition, the immune checkpoints including PD-1 and LAG3 were upregulated in the T cells in distant non-RFA tumors after RFA treatment. In conclusion, our data indicate that RFA treatment induced remodeling of tumor immune microenvironment in distant non-RFA tumors in pancreatic cancer mouse model and suggest that combining RFA with immune checkpoint inhibitors may be an effective treatment approach.

Targeting BET bromodomain proteins in cancer: The example of lymphomas

The Bromo- and Extra-Terminal domain (BET) family proteins act as "readers" of acetylated histones and they are important transcription regulators. BRD2, BRD3, BRD4 and BRDT, part of the BET family, are important in different tumors, where upregulation or translocation often occurs. The potential of targeting BET proteins as anti-cancer treatment originated with data obtained with a first series of compounds, and there are now several data supporting BET inhibition in both solid tumors and hematological malignancies. Despite very positive preclinical data in different tumor types, the clinical results have been so far moderate. Using lymphoma as an example to review the data produced in the laboratory and in the context of the early clinical trials, we discuss the modalities to make BET targeting more efficient both generating novel generation of compounds and by exploring the combination with small molecules affecting various signaling pathways, BCL2, or DNA damage response signaling, but also with additional epigenetic agents and with immunotherapy. We also discuss the mechanisms of resistance and the toxicity profiles so far reported.

Combining protein arginine methyltransferase inhibitor and anti-programmed death-ligand-1 inhibits pancreatic cancer progression

BACKGROUND

Immunotherapy targeting programmed death-1 (PD-1) or programmed death-ligand-1 (PD-L1) has been shown to be effective in a variety of malignancies but has poor efficacy in pancreatic ductal adenocarcinoma (PDAC). Studies have shown that PD-L1 expression in tumors is an important indicator of the efficacy of immunotherapy. Tumor cells usually evade chemotherapy and host immune surveillance by epigenetic changes. Protein arginine methylation is a common posttranslational modification. Protein arginine methyltransferase (PRMT) 1 is deregulated in a wide variety of cancer types, whose biological role in tumor immunity is undefined.

AIM

To investigate the combined effects and underlying mechanisms of anti-PD-L1 and type I PRMT inhibitor in pancreatic cancer in vivo.

METHODS

PT1001B is a novel type I PRMT inhibitor with strong activity and good selectivity. A mouse model of subcutaneous Panc02-derived tumors was used to evaluate drug efficacy, toxic and side effects, and tumor growth in vivo. By flow cytometry, we determined the expression of key immune checkpoint proteins, detected the apoptosis in tumor tissues, and analyzed the immune cells. Immunohistochemistry staining for cellular proliferation-associated nuclear protein Ki67, TUNEL assay, and PRMT1/PD-L1 immunofluorescence were used to elucidate the underlying molecular mechanism of the antitumor effect.

RESULTS

Cultured Panc02 cells did not express PD-L1 in vitro, but tumor cells derived from Panc02 transplanted tumors expressed PD-L1. The therapeutic efficacy of anti-PD-L1 mAb was significantly enhanced by the addition of PT1001B as measured by tumor volume (1054.00 ± 61.37 mm³vs 555.80 ± 74.42 mm³, P < 0.01) and tumor weight (0.83 ± 0.06 g vs 0.38 ± 0.02 g, P < 0.05). PT1001B improved antitumor immunity by inhibiting PD-L1 expression on tumor cells (32.74% ± 5.89% vs 17.95% ± 1.92%, P < 0.05). The combination therapy upregulated tumor-infiltrating CD8+ T lymphocytes (23.75% ± 3.20% vs 73.34% ± 4.35%, P < 0.01) and decreased PD-1+ leukocytes (35.77% ± 3.30% vs 6.48% ± 1.08%, P < 0.001) in tumor tissue compared to the control. In addition, PT1001B amplified the inhibitory effect of anti-PD-L1 on tumor cell proliferation and enhanced the induction of tumor cell apoptosis. PRMT1 downregulation was correlated with PD-L1 downregulation.

CONCLUSION

PT1001B enhances antitumor immunity and combining it with anti-PD-L1 checkpoint inhibitors provides a potential strategy to overcome anti-PD-L1 resistance in PDAC.

Role of tumor microenvironment in the regulation of PD-L1: A novel role in resistance to cancer immunotherapy

Tumor evasion from the host immune system is a substantial strategy for tumor development and survival. The expression of many immune checkpoint proteins in cancer cells is a mechanism by which tumor cells escape from the immune system. Among the well-known immune checkpoints that can tremendously affect tumor development and cancer therapy are the programmed death-ligand-1/programmed death-1 (PD-L1/PD-1). To tackle this phenomenon and improve the therapeutic strategies in cancer treatment, the blockade of the PD-L1/PD-1 pathway is introduced as a target, but the therapeutic advantage of PD L1/PD-1 blockade has not fulfilled the expectations. This condition may be associated with a different type of resistance in a considerable number of patients. A crucial issue to conquer resistance against immune checkpoint blockade therapy is to understand how PD-L1 level is regulated. However, the mechanisms by which the PD-L1 expression is regulated are complicated, and they can occur at different levels from signaling pathways to posttranscriptional levels. For example, various transcriptional factors, such as hypoxia-inducible factor-1, nuclear factor-κΒ, interferon-γ, STAT3, MYC, and AP-1 can regulate the PD-L1 distribution at the transcriptional level. Herein, we tried to focus on the most important regulatory mechanisms of PD-L1 by inducible agents in the tumor cells, such as signaling pathways, transcriptional factors, and posttranscriptional factors. Finally, these approaches may open up new windows for targeting tumor immune evasion and suggest the novel suppressors of PD-L1 for efficient therapeutics.

C-Myc regulates PD-L1 expression in esophageal squamous cell carcinoma

Immunotherapy using antibodies blocking the programmed cell death 1 (PD-1)/programmed cell death-ligand 1 (PD-L1) pathway has achieved great success in preclinical models and the clinical treatment of esophageal squamous cell carcinoma (ESCC). The c-Myc proto-oncogene helps prevent immune cells from attacking tumor cells by inducing PD-L1 expression. However, the underlying mechanisms of c-Myc and PD-L1 in ESCC remain unclear, and a thorough understanding of this regulation would allow the development of new approaches to enhance antitumor immunity. In the present study, the positive relationship between c-Myc and PD-L1 was explored in the Cancer Genome Atlas dataset using the bioinformatics tool GEPIA, and was confirmed in 105 ESCC tissues by immunostaining (r=0.516, P<0.001). The patients positive for both proteins had a poorer overall survival (P=0.032). Furthermore, in ESCC cell lines, c-Myc overexpression, depletion, and inhibition was able to regulate the expression of PD-L1. Also, the ChIP assays showed that the increase in PD-L1 expression was likely due to the binding of c-Myc to the PD-L1 promoter. Taken together, c-Myc and PD-L1 levels were significantly correlated, and c-Myc expression regulated the expression of PD-L1 in ESCC cells. In addition, a small molecule inhibitor of c-Myc effectively regulated PD-L1 expression. This indicates that synergistic therapy combining a c-Myc inhibitor with PD-L1 immunotherapy might be a promising new treatment strategy for ESCC.

Cancer immunotherapy: Pros, cons and beyond

Cancer immunotherapy is an innovative treatment for tumors today. In various experiments and clinical studies, it has been found that immunotherapy does have incomparable advantages over traditional anti-tumor therapy, which can prolong progression-free survival (PFS) and overall survival (OS). However, immunotherapy has obvious complexity and uncertainty. Immunotherapy may also cause severe adverse reactions due to an overactive immune system. More effective and fewer adverse reactions immunological checkpoints are still under further exploration. This review gives an overview of recent developments in immunotherapy and indicates a new direction of tumor treatment through analyzing the pros and cons of immunotherapy coupled with keeping a close watch on the development trend of the immunotherapy future.

Single-cell RNA sequencing reveals compartmental remodeling of tumor-infiltrating immune cells induced by anti-CD47 targeting in pancreatic cancer

Background

Human pancreatic ductal adenocarcinoma (PDAC) responds poorly to immune checkpoint inhibitor (ICPi). While the mechanism is not completely clear, it has been recognized that tumor microenvironment (TME) plays key roles. We investigated if targeting CD47 with a monoclonal antibody could enhance the response of PDAC to ICPi by altering the TME.

Methods

Using immunohistochemistry, we examined tumor-infiltrating CD68⁺ pan-macrophages (CD68⁺ M) and CD163⁺ M2 macrophages (CD163⁺ M2) and tumor expression of CD47 and PD-L1 proteins in 106 cases of PDAC. The efficacy of CD47 blockade was examined in xenograft models. CD45⁺ immune cells from syngeneic tumor models were subjected to single-cell RNA-sequencing (scRNA-seq) by using the 10x Genomics pipeline.

Results

We found that CD47 expression correlated with the level of CD68⁺ M but not CD163⁺ M2. High levels of tumor-infiltrating CD68⁺ M, CD163⁺ M2, and CD47 expression were significantly associated with worse survival. CD47^high/CD68⁺ M^high and CD47^high/CD163⁺ M2^high correlated significantly with shorter survival, whereas CD47^low/CD68⁺ M^low and CD47^low/CD163⁺ M2^low correlated with longer survival. Intriguingly, CD47 blockade decreased the tumor burden in the Panc02 but not in the MPC-83 syngeneic mouse model. Using scRNA-seq, we showed that anti-CD47 treatment significantly remodeled the intratumoral lymphocyte and macrophage compartments in Panc02 tumor-bearing mice by increasing the pro-inflammatory macrophages that exhibit anti-tumor function, while reducing the anti-inflammatory macrophages. Moreover, CD47 blockade not only increased the number of intratumoral CD8⁺ T cells, but also remodeled the T cell cluster toward a more activated one. Further, combination therapy targeting both CD47 and PD-L1 resulted in synergistic inhibition of PDAC growth in the MPC-83 but not in Panc02 model. MPC-83 but not Panc02 mice treated with both anti-CD47 and anti-PD-L1 showed increased number of PD-1⁺CD8⁺ T cells and enhanced expression of key immune activating genes.

Conclusion

Our data indicate that CD47 targeting induces compartmental remodeling of tumor-infiltrating immune cells of the TME in PDAC. Different PDAC mouse models exhibited differential response to the anti-CD47 and anti-PD-L1 blockade due to the differential effect of this combination treatment on the infiltrating immune cells and key immune activating genes in the TME established by the different PDAC cell lines.