BET Bromodomain Inhibition Promotes Anti-tumor Immunity by Suppressing PD-L1 Expression

Reprogramming of radiation-deteriorated TME by liposomal nanomedicine to potentiate radio-immunotherapy

Radiotherapy, although widely used for cancer therapy, always triggers changes in tumor microenvironment (TME) that lead to radioresistance and immunosuppression. In particular, during X-ray irradiation, hypoxia exacerbation would reduce radiosensitivity of tumor cells, while programmed cell death ligand 1 (PD-L1) upregulation impairs antitumor immune responses and exacerbates DNA damage repair, collectively resulting in severe T cell exhaustion and unsatisfactory therapeutic effect. Herein, we developed a liposomal nanodrug, C/J-LipoRGD, to simultaneously encapsulate a biological enzyme and a bromodomain containing 4 (BRD4) inhibitor for tumor-targeting delivery and TME modulation. Among C/J-LipoRGD, catalase could catalyze the decomposition of the excess H2O2 in tumors and improve TME oxygenation. Meanwhile, JQ1 as a BRD4 inhibitor after being taken by cancer cells could downregulate PD-L1 expression in both cellular membrane and cytosol, inhibiting PD-1/PD-L1 interaction and DNA damage repair. By alleviating hypoxia and downregulating PD-L1 expression, C/J-LipoRGD reverses T cell exhaustion in TME. Altogether, C/J-LipoRGD-based radiotherapy significantly inhibited tumor growth and meanwhile triggered immunogenic cell death (ICD) of cancer cells to activate T cell-mediated anti-tumor immunity. After the combination with αPD-1, C/J-LipoRGD-based radio-immunotherapy achieved complete tumor eradication and metastases elimination in 80 % mice with survival over 80 days. This multifunctional nanodrug represents a promising strategy to overcome therapy resistance and optimize radio-immunotherapy outcomes.

Acetylation and deacetylation dynamics in stress response to cancer and infections

In response to stress stimuli, cells have evolved various mechanisms to integrate internal and external signals to achieve dynamic homeostasis. Lysine acetyltransferase (KATs) and deacetyltransferase (KDACs) are the key modulators of epigenetic modifications, enabling cells to modulate cellular responses through the acetylation and deacetylation of both histone and nonhistone proteins. Understanding the signaling pathways involved in cellular stress response, along with the roles of KATs and KDACs may pave the way for the development of novel therapeutic strategies. This review discusses the molecular mechanisms of acetylation and deacetylation in stress responses related to tumorigenesis, viral and bacterial infections. In tumorigenesis section, we focused on the tumor cells' intrinsic and external molecules and signaling pathways regulated by acetylation and deacetylation modification. In viral and bacterial infections, we summarized the update research on acetylation and deacetylation modification in viral and bacterial infections, which systematical introduction on this topic is not too much. Additionally, we provide an overview of current therapeutic interventions and clinical trials involving KAT and KDAC inhibitors in the treatment of cancer, as well as viral and bacterial infection-related diseases.

The covalent modification of STAT1 cysteines by sulforaphane promotes antitumor immunity via blocking IFN-γ-induced PD-L1 expression

Sulforaphane (SFN), a natural compound found in cruciferous vegetables, possesses well-documented antitumor properties. However, the precise functions and mechanisms of SFN in cancer suppression remain poorly understood. Here we provide evidence to demonstrate that SFN exerts more pronounced antitumor effects in immunocompetent mice compared to immunodeficient mice, suggesting the involvement of the host immune system in SFN-mediated tumor suppression. Furthermore, we reveal that SFN primarily acts through CD8+ cytotoxic T lymphocytes (CTLs) to enhance antitumor immunity by blocking the IFN-γ-mediated induction of PD-L1, a critical immune checkpoint receptor expressed in cancer cells. Importantly, our findings indicate that the suppression of PD-L1 expression by SFN is independent of the NRF2 protein stabilization pathway. Instead, SFN inhibits IFN-γ-mediated activation of STAT1, a key transcription factor involved in PD-L1 induction. Mechanistically, SFN covalently modifies specific cysteine residues (C155 and C174) on STAT1, resulting in the inhibition of its transcriptional activity. Notably, SFN-mediated downregulation of PD-L1 contributes to its antitumor immune effects, as demonstrated by enhanced anti-CTLA-4-mediated cytotoxicity. These findings indicate that SFN's antitumor effect extends beyond its direct cytotoxic properties, as it also actively engages the host immune system. This underscores SFN's immense potential as an immune-modulating agent in cancer therapy.

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.

Epigenetic regulators combined with tumour immunotherapy: current status and perspectives

Immunotherapy, particularly immune checkpoint inhibitor therapy, has demonstrated clinical benefits in solid tumours. Despite its satisfactory clinical efficacy, it still faces several issues, such as limited eligibility, low response rates and cytotoxicity. Cancer epigenetics implies that tumour cells exhibit unique phenotypes because of their unique characteristics, thus reprogramming of the epigenome holds promise for cancer therapy. Epigenetic regulation plays an important role in regulating gene expression during tumour development and maintenance. Epigenetic regulators induce cancer cell cycle arrest, apoptosis and differentiation of cancer cells, thereby exerting anti-tumour effects. Recent studies have revealed a significant correlation between epigenetic regulatory factors and immune checkpoint therapy. Epigenetics can modulate various aspects of the tumour immune microenvironment and immune response to enhance the sensitivity of immunotherapy, such as lowering the concentration required and mitigating cytotoxicity. This review primarily discusses DNA methyltransferase inhibitors, histone deacetylase inhibitors, enhancer of zeste homolog 2 inhibitors and lysine-specific demethylase 1 inhibitors, which are associated with transcriptional repression. This repression alters the expression of genes involved in the immune checkpoint, thereby enhancing the effectiveness of immunotherapy. We also discuss the potential and challenges of tumour immunotherapy and highlight its advantages, application challenges and clinical research on integrating epigenetic regulatory factors with tumour immunotherapy.

Immune modulation in solid tumors: a phase 1b study of RO6870810 (BET inhibitor) and atezolizumab (PD-L1 inhibitor)

PURPOSE

Bromodomain and extra-terminal domain (BET) inhibitors (BETi) have demonstrated epigenetic modulation capabilities, specifically in transcriptional repression of oncogenic pathways. Preclinical assays suggest that BETi potentially attenuates the PD1/PD-L1 immune checkpoint axis, supporting its combination with immunomodulatory agents.

PATIENTS AND METHODS

A Phase 1b clinical trial was conducted to elucidate the pharmacokinetic and pharmacodynamic profiles of the BET inhibitor RO6870810 as monotherapy and in combination with the PD-L1 antagonist atezolizumab in patients with advanced ovarian carcinomas and triple-negative breast cancer (TNBC). Endpoints included maximum tolerated dosages, adverse event profiling, pharmacokinetic evaluations, and antitumor activity. Pharmacodynamic and immunomodulatory effects were assessed in tumor tissue (by immunohistochemistry and RNA-seq) and in peripheral blood (by flow cytometry and cytokine analysis).

RESULTS

The study was terminated prematurely due to a pronounced incidence of immune-related adverse effects in patients receiving combination of RO6870810 and atezolizumab. Antitumor activity was limited to 2 patients (5.6%) showing partial response. Although target engagement was confirmed by established BETi pharmacodynamic markers in both blood and tumor samples, BETi failed to markedly decrease tumor PD-L1 expression and had a suppressive effect on antitumor immunity. Immune effector activation in tumor tissue was solely observed with the atezolizumab combination, aligning with this checkpoint inhibitor's recognized biological effects.

CONCLUSIONS

The combination of BET inhibitor RO6870810 with the checkpoint inhibitor atezolizumab presents an unfavorable risk-benefit profile for ovarian cancer and TNBC (triple-negative breast cancer) patients due to the increased risk of augmented or exaggerated immune reactions, without evidence for synergistic antitumor effects.

TRIAL REGISTRATION

ClinicalTrials.gov ID NCT03292172; Registration Date: 2017-09-25.

The epigenetic hallmarks of immune cells in cancer

Targeting the dysregulation of epigenetic mechanisms in cancer has emerged as a promising therapeutic strategy. Although the significant rationale progress of epigenetic therapies in blocking cancer cells, how epigenetic regulation shapes tumor microenvironment (TME) and establishes antitumor immunity remains less understood. Recent study focus has been put on the epigenetic-mediated changes in the fate of immune cells, including the differentiation, expansion, recruitment, functionalization, and exhaustion of T cells, natural killer (NK) cells, tumor-associated macrophages (TAMs), dendritic cells (DCs), myeloid-derived suppressor cells (MDSCs), and B cells within the TME. Here, we review the latest molecular and clinical insights into how DNA modifications, histone modification, and epitranscriptome-related regulations shape immune cells of various cancers. We also discuss opportunities for leveraging epigenetic therapies to improve cancer immunotherapies. This review provides the epigenetic foundations of cancer immunity and proposes the future direction of combination therapies.

Discovery of Novel Hydrazide-Based HDAC3 Inhibitors as Epigenetic Immunomodulators for Cancer Immunotherapy

Based on our previous work, a series of imidazole-based small molecules were designed and synthesized as HDAC3 inhibitors. Among them, compound SC26 showed selective HDAC3 inhibition activity with an IC50 of 53 nM (SI = 75 for HDAC3 over HDAC1). Further studies revealed that SC26 could dose-dependently induce the expression of PD-L1 in MC38 cells by activating the PD-L1 transcription. SC26 also showed high in vivo antitumor efficacy in a colorectal cancer model (50 mg/kg po, TGI = 63%). Importantly, the combination of SC26 with the PD-L1 inhibitor NP19 activated the immune system in tumor-bearing mice, enhancing the antitumor immune response (TGI = 80%, 50 + 50 mg/kg, p.o.). Collectively, we report for the first time that an HDAC3 inhibitor could upregulate PD-L1 expression in vitro and in vivo, specifically in MC38 cells and MC38-bearing tumors, and SC26 represents a novel epigenetic immunomodulator with potential applications in tumor immunotherapy.

Enzyme-Activated Orthogonal Proteolysis Chimeras for Tumor Microenvironment-Responsive Immunomodulation

Precise modulation of dynamic and complex tumor microenvironment (TME) to disrupt tumorigenesis and reshape intratumoral immune infiltration has emerged as promising approaches for enhanced cancer therapy. Among recent innovations, proteolysis-targeting chimeras (PROTACs) represent a burgeoning chemical knockdown technology capable of degrading oncogenic protein homeostasis and inducing dynamic alternations within carcinoma settings, offering potential for antitumor manipulation. However, achieving selectivity in PROTACs that respond to disease environmental stimulation and precisely perturb on-target proteins remains challenging. The multi-step synthesis and limited permeability, attributed to high-molecular-weight and heterobifunctional structures, further hinder their in vivo efficacy. Herein, we present a unique TME-responsive enzyme-activated clickable PROTACs, which features a short peptide-tagged pomalidomide derivative to undergo tumor-specific cleavage by cathepsin protease to induce orthogonal crosslinking of the exposed cysteine with 2-cyanobenzothiazole-labeled epigenetic protein-ligand JQ1, facilitating in situ degrader formation within tumor regions only. Systematic protein profiling and proteomic analysis revealed that such TME-specific clickable-PROTACs not only selectively eliminate epigenetic proteins without tedious pre-synthesis to bridge disparate small-molecule bi-warhead fragments, but also demonstrated superior tumor penetration compared to conventional high-molecular-weight PROTACs. Importantly, these clickable-PROTACs efficiently downregulated immune checkpoint programmed death-ligand 1 (PD-L1) both in vitro and in vivo, remodeling TME for enhanced therapeutics, especially in anti-tumoral immunomodulation.

NUAK1 acts as a novel regulator of PD-L1 via activating GSK-3β/β-catenin pathway in hepatocellular carcinoma

BACKGROUND

NUAK1 is associated with metastasis and drug resistance in hepatocellular carcinoma (HCC). However, little is known about the immune functions of NUAK1 in HCC. Therefore, the aim of this study was to elucidate the novel role of NUAK1 in facilitating immune evasion in HCC and to investigate the mechanisms underpinning this process.

METHOD

The levels of NUAK1 expression and the infiltration of CD8+ T cells were assessed in tumor tissues from HCC patients and mice xenograft model. HCC cell lines were used to validate the role of NUAK1 in regulating the transcription of PD-L1, the diethylnitrosamine-induced HCC model was established and the expression levels of NUAK1 and PD-L1 proteins in the rat livers were detected. Western blotting, immunofluorescence, real time PCR, and immunohistochemical staining were used to investigate the underlying mechanisms by which NUAK1 regulates PD-L1 expression in hepatocellular carcinoma.

RESULTS

NUAK1 expression was negatively correlated with CD8+ T cell infiltration in tumor tissues from HCC patients and mice xenograft model. Both gain and loss of functions have identified NUAK1 promoted PD-L1 expression at transcriptional level in HCC cells. The increased expression of NUAK1 and PD-L1 proteins were observed in the rat livers of diethylnitrosamine-induced HCC model. Moreover, overexpression of NUAK1 promotes GSK3β Ser9 phosphorylation, β-catenin expression and nuclear accumulation in HCC cells. By contrast, knockdown of NUAK1 has opposite effects. Inhibition of GSK3β activity significantly promoted β-catenin expression and PD-L1 expression in HCC cells. IHC analyses of tumor tissues from HCC patients suggested that the levels of p-GSK3β and β-catenin were positively correlated with NUAK1 expression. Knockdown of β-catenin also reversed NUAK1-mediated PD-L1 expression in HCC cells.

CONCLUSIONS

This study revealed a novel role for NUAK1, which promotes the transcriptional expression of PD-L1 by activating GSK3β/β-catenin signaling pathway, leading to immune escape of hepatocellular carcinoma. Registry and the registration no. of the study/trial: Not applicable.

Adding checkpoint inhibitors to first-line chemotherapy for NUT carcinoma patients

Rare cancers present significant challenges in diagnosis, treatment, and research, accounting for up to 25% of global cancer cases. Due to their rarity and atypical presentations, they are often misdiagnosed, resulting in late-stage detection and poor outcomes. Here, we describe a patient case with advanced metastatic nasopharynx NUT carcinoma, one of the rarest and most aggressive cancers. We conducted a comprehensive analysis of this patient's tumor, including Tumor Mutation Burden, Microsatellite Instability, and genetic profiling to explore further putative druggable targets. The tumor exhibited high PD-L1 expression and showed a notable response to immune checkpoint inhibitors when combined with platinum-based radio-chemotherapy. Our findings indicate that checkpoint inhibitors could play a critical role in treating NUT carcinoma, offering new therapeutic avenues and hope for patients with this challenging diagnosis. Whether PD-L1 expression may be a useful predictor of immune checkpoint inhibitor efficacy warrants further research.

Nanomaterial-enabled metabolic reprogramming strategies for boosting antitumor immunity

Immunotherapy has become a crucial strategy in cancer treatment, but its effectiveness is often constrained. Most cancer immunotherapies focus on stimulating T-cell-mediated immunity by driving the cancer-immunity cycle, which includes tumor antigen release, antigen presentation, T cell activation, infiltration, and tumor cell killing. However, metabolism reprogramming in the tumor microenvironment (TME) supports the viability of cancer cells and inhibits the function of immune cells within this cycle, presenting clinical challenges. The distinct metabolic needs of tumor cells and immune cells require precise and selective metabolic interventions to maximize therapeutic outcomes while minimizing adverse effects. Recent advances in nanotherapeutics offer a promising approach to target tumor metabolism reprogramming and enhance the cancer-immunity cycle through tailored metabolic modulation. In this review, we explore cutting-edge nanomaterial strategies for modulating tumor metabolism to improve therapeutic outcomes. We review the design principles of nanoplatforms for immunometabolic modulation, key metabolic pathways and their regulation, recent advances in targeting these pathways for the cancer-immunity cycle enhancement, and future prospects for next-generation metabolic nanomodulators in cancer immunotherapy. We expect that emerging immunometabolic modulatory nanotechnology will establish a new frontier in cancer immunotherapy in the near future.

A novel ROR1-targeting antibody-PROTAC conjugate promotes BRD4 degradation for solid tumor treatment

Rationale: Proteolysis Targeting Chimeras (PROTACs) are bifunctional compounds that have been extensively studied for their role in targeted protein degradation (TPD). The capacity to degrade validated or undruggable targets provides PROTACs with significant potency in cancer therapy. However, the clinical application of PROTACs is limited by their poor in vivo potency and unfavorable pharmacokinetic properties. Methods: In this study, a novel degrader-antibody conjugate (DAC) was developed by conjugating the BRD4-degrading PROTAC with the ROR1 (receptor tyrosine kinase-like orphan receptor 1) antibody. The in vitro affinity, internalization efficacy, degradation, and cytotoxic activity of the ROR1 DAC were assessed. The pharmacokinetics, antitumor activity, and acute toxicity of ROR1 DAC were evaluated in mouse models. RNA sequencing (RNA-seq) and immunohistochemistry were performed to analyze the therapeutic efficacy mediated by the combination of ROR1 DAC and anti-mouse programmed cell death protein 1 (αmPD1) mAb. Results: The ROR1 DAC exhibited strong degradation activity and cytotoxicity following antigen binding and internalization. Compared to unconjugated PROTAC, the ROR1 DAC demonstrated improved pharmacokinetics and potent antitumor efficacy in PC3 and MDA-MB-231 xenograft mouse models. Furthermore, enhanced antitumor activity and immune cell infiltration within solid tumors were observed when combined with αmPD-1 mAb in C57BL/6J mice. RNA sequencing revealed that the enhanced immune response associated with the combination treatment is related to tumor microenvironment modulation, including the upregulation of Th1-biased cytokines. Moreover, the ROR1 DAC exhibited a favorable safety profile in an acute toxicity study. Conclusions: These results indicate that the degrader-antibody conjugate is a promising candidate for tumor-specific degradation and effective cancer therapy.

Optimizing CAR-T cell function in solid tumor microenvironment: insights from culture media additives

Cancer remains one of the most pressing health challenges worldwide. Recently, chimeric antigen receptor (CAR)-T cell therapy has emerged as a promising approach for treating hematological cancers. However, the translation of CAR-T cell therapy to solid tumors faces formidable obstacles, notably the immunosuppressive tumor microenvironment. Within solid tumors, CAR-T cells encounter a hostile milieu that promotes exhaustion and diminishes their long-term effectiveness against cancer cells. Optimizing the manufacturing process is paramount to ensuring the efficacy of CAR-T cell therapy in solid tumors. A critical aspect of this optimization lies in refining the composition of cell culture media. By supplementing basic culture media with specific additives, researchers aim to improve the behavior and functionality of CAR-T cells, thereby enhancing their therapeutic potential. This review delves into the culture media additives that have been investigated or show promise in modulating CAR-T cell phenotypes and enhancing their anti-tumor efficacy. We explore various types of additives and their mechanisms of action to mitigate exhaustion and augment persistence within the challenging solid tumor microenvironment. By shedding light on the latest advancements in culture media optimization for CAR-T cell therapy, this review aims to provide insights into novel strategies for overcoming the hurdles posed by solid tumors. Ultimately, these insights hold the potential to enhance the effectiveness of CAR-T cell therapy and improve outcomes for cancer patients.

Nucleo-cytosolic acetyl-CoA drives tumor immune evasion by regulating PD-L1 in melanoma

Acetyl coenzyme A (acetyl-CoA), a versatile central metabolite, plays a critical role in various metabolic processes and protein acetylation. While its impact on tumor cell properties is well established, the connection between acetyl-CoA metabolism and immune evasion in tumors remains unclear. Here, we uncover a mechanism by which nucleo-cytosolic acetyl-CoA contributes to immune evasion through regulation of programmed death ligand 1 (PD-L1). Specifically, bioinformatics analysis reveals a negative correlation between acetyl-CoA metabolism and anti-tumor immunity across multiple cancers. Inhibition of the acetyl-CoA-producing enzyme ATP-citrate lyase (ACLY) leads to a re-invigoration of cytotoxic T cells and enhances the efficacy of immunotherapy. Mechanistically, nucleo-cytosolic acetyl-CoA promotes PD-L1 transcription via P300-dependent histone H3K27 acetylation at the promoter region of CD274. The ACLY-H3K27ac-PD-L1 axis is verified in clinical specimens and predicts poor immunotherapy response. Our findings suggest that targeting acetyl-CoA metabolism may act as a promising strategy to overcome immune evasion and improve the outcomes of cancer immunotherapy.

RNA kinetics influence the response to transcriptional perturbation in leukaemia cell lines

Therapeutic targeting of dysregulated transcription has emerged as a promising strategy for the treatment of cancers, such as leukaemias. The therapeutic response to small molecule inhibitors of Bromodomain-Containing Proteins (BRD), such as BRD2 and BRD4, P300/cAMP-response element binding protein (CBP) and Cyclin Dependent Kinases (CDKs), is generally attributed to the selective disruption of oncogenic gene expression driven by enhancers, super-enhancers (SEs) and lineage-specific transcription factors (TFs), including the c-MYC oncogene. The selectivity of compounds targeting the transcriptional machinery may be further shaped by post-transcriptional processes. To quantitatively assess the contribution of post-transcriptional regulation in responses to transcription inhibition, we performed multi-omics analyses to accurately measure mRNA production and decay kinetics. We demonstrate that it is not only the selective disruption of mRNA production, but rather mRNA decay rates that largely influence the selectivity associated with transcriptional inhibition. Accordingly, genes down-regulated with transcriptional inhibitors are largely characterized by extremely rapid mRNA production and turnover. In line with this notion, stabilization of the c-MYC transcript through swapping of its 3' untranslated region (UTR) rendered c-MYC insensitive to transcriptional targeting. This failed to negate the impact on c-MYC downstream targets and did not abrogate therapeutic responses. Finally, we provide evidence that modulating post-transcriptional pathways, such as through ELAVL1 targeting, can sensitize long-lived mRNAs to transcriptional inhibition and be considered as a combination therapy approach in leukaemia. Taken together, these data demonstrate that mRNA kinetics influence the therapeutic response to transcriptional perturbation and can be modulated for novel therapeutic outcomes using transcriptional agents in leukaemia.

Platycodin D reduces PD-L1 levels by inhibiting LXR-β activity and combines with nintedanib to enhance the tumor-killing effect of T cells

Most tumors are resistant to programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) checkpoint inhibitors, which may be due to impaired antigen presentation resulting from the downregulation of major histocompatibility complex class I (MHC-I) expression on tumor cells. We observed that platycodin D (PD), polygalacin D, and platycodin D2, which are plant-derived triterpenoid saponins, significantly reduced PD-L1 levels. RNA sequencing and the PharmMapper database analysis identified liver X receptor β (LXR-β) as a potential PD target. Further studies showed that PD reduces PD-L1 levels by binding to LXR-β and inhibiting LXR-β activity. Coadministration of PD and nintedanib, known to upregulate MHC-I expression, enhanced tumor recognition and killing by T cells. This study provides new insights into PD applications and mechanisms.

Sirtinol, a SIRT1 inhibitor, inhibits the EMT and metastasis of 4T1 breast cancer cells and impacts the tumor microenvironment

INTRODUCTION

The impact of epigenetic drugs on metastasis and the immunological microenvironment is poorly understood. In this study, we looked at how sirtinol, a SIRT1 inhibitor, affected epithelial-mesenchymal transition (EMT), metastasis, and the immune cells.

MATERIALS AND METHODS

In vitro experiments were carried out using tumor conditioned medium (TCM). For in vivo experiments, sirtinol was administered i.p. in tumor bearing BALB/c mice at a dose of 2 mg/kg body weight either alone or in combination with cisplatin. Estimation of cytokines was carried out using ELISA or ELIspot. Estimation of different markers was done using flow cytometry or western blot.

RESULTS

Sirtinol, a SIRT1 inhibitor, was found to be cytotoxic to 4T1 breast cancer cells with no synergistic effects with cisplatin, both under in vitro and in vivo conditions (p < 0.05). Sirtinol significantly reduced cancer cell metastasis to the spleen which was supported by in vitro findings such as decreased vimentin expression and cell mobility in migration and wound healing assays (p < 0.01). Studies on the effects of 4T1 tumor-conditioned medium on spleen cells indicated changes in T cell proliferation as well as differentiation (p < 0.01). In tumor bearing mice, spleen cells showed elevated IFN-γ secretion, increased CD11b+ cells, and decreased T cells (p < 0.01). This was reversed by sirtinol as well as the combination treatment, which may also have contributed to metastasis inhibition (p < 0.01).

CONCLUSION

Sirtinol, a SIRT1 inhibitor inhibits EMT and metastasis of 4T1 breast cancer cells and also has an impact on the immune microenvironment.

MMP-2-triggered, mitochondria-targeted PROTAC-PDT therapy of breast cancer and brain metastases inhibition

Proteolytic targeting chimera (PROTAC) technology is a protein-blocking technique and induces antitumor effects, with potential advantages. However, its effect is limited by insufficient distribution and accumulation in tumors. Herein, a transformable nanomedicine (dBET6@CFMPD) with mitochondrial targeting capacity is designed and constructed to combine PROTAC with photodynamic therapy (PDT). In this work, we demonstrate that dBET6@CFMPD exhibits great biodistribution and retention, and can induce potent antitumor response to suppress primary and metastatic tumors, becoming a nanomedicine with potential in cancer combination therapy.

Immune Checkpoint-Modulating Photosensitizer That Targets BRD4 for Cancer Photoimmunotherapy

Photodynamic therapy is an efficient approach to promote cytotoxic T lymphocyte tumor infiltration to convert immunologically cold tumors into hot tumors through the induction of immunogenic cell death . However, tumors usually overexpress immune checkpoints such as PD-L1 to suppress T lymphocyte antitumor activity and evade immune surveillance. Therefore, the design of efficient photosensitizers to overcome checkpoint-mediated immune evasion is highly necessary. In this work, we report the design of BRD-PS, a BRD4-targeting photosensitizer, as a new class of immunomodulatory photosensitizer termed an immune checkpoint-modulating photosensitizer, to solve this issue. On one hand, BRD-PS induces immunogenic pyroptosis and ferroptosis to promote the activation and tumor infiltration of cytotoxic T cells. On the other hand, BRD-PS suppresses the expression of PD-L1 to avoid immune evasion. This work demonstrated the feasibility of utilizing a single photosensitizer to simultaneously induce immunogenic cell death and PD-L1 downregulation for synergistic cancer photoimmunotherapy.

Zosuquidar Promotes Antitumor Immunity by Inducing Autophagic Degradation of PD-L1

The intracellular distribution and transportation process are essential for maintaining PD-L1 (programmed death-ligand 1) expression, and intervening in this cellular process may provide promising therapeutic strategies. Here, through a cell-based high content screening, it is found that the ABCB1 (ATP binding cassette subfamily B member 1) modulator zosuquidar dramatically suppresses PD-L1 expression by triggering its autophagic degradation. Mechanistically, ABCB1 interacts with PD-L1 and impairs COP II-mediated PD-L1 transport from ER (endoplasmic reticulum) to Golgi apparatus. The treatment of zosuquidar enhances ABCB1-PD-L1 interaction and leads the ER retention of PD-L1, which is subsequently degraded in the SQSTM1-dependent selective autophagy pathway. In CT26 mouse model and a humanized xenograft mouse model, zosuquidar significantly suppresses tumor growth and accompanies by increased infiltration of cytotoxic T cells. In summary, this study indicates that ABCB1 serves as a negative regulator of PD-L1, and zosuquidar may act as a potential immunotherapy agent by triggering PD-L1 degradation in the early secretory pathway.

Research progress of BRD4 in head and neck squamous cell carcinoma: Therapeutic application of novel strategies and mechanisms

Bromodomain-containing protein 4 (BRD4) belongs to the bromodomain and extra-terminal domain (BET) protein family, which plays a crucial role in recognizing acetylated lysine residues in chromatin. The abnormal expression of BRD4 contributes to the development of various human malignant tumors, including head and neck squamous cell carcinoma (HNSCC). Recent studies have shown that BRD4 inhibition can effectively prevent the proliferation and growth of HNSCC. However, the specific role and mechanism of BRD4 in HNSCC are not yet fully clarified. This article will briefly summarize the critical role of BRD4 in the pathogenesis of HNSCC and discuss the potential clinical applications of targeting BRD4 in HNSCC therapy. We further inquiry the challenges and opportunities for HNSCC therapies based on BRD4 inhibition, including BRD4 inhibitor combination with conventional chemotherapy, radiotherapy, and immunotherapy, as well as new strategies of BRD4-targeting drugs and BRD4 proteolysis-targeting chimeras (PROTACs). Moreover, we will also offer outlook on the associated challenges and future directions of targeting BRD4 for the treatment of patients with HNSCC.

BET inhibition sensitizes innate checkpoint inhibitor resistant melanoma to anti-CTLA-4 treatment

Approximately 50% of melanoma patients fail to respond to immune checkpoint blockade (ICB), and acquired resistance hampers long-term survival in about half of initially responding patients. Whether targeting BET reader proteins, implicated in epigenetic dysregulation, can enhance ICB response rates and durability, remains to be determined. Here we show elevated BET proteins correlate with poor survival and ICB responses in melanoma patients. The BET inhibitor IBET151, combined with anti-CTLA-4, overcame innate ICB resistance however, sequential BET inhibition failed against acquired resistance in mouse models. Combination treatment response in the innate resistance model induced changes in tumor-infiltrating immune cells, reducing myeloid-derived suppressor cells (MDSCs). CD4+ and CD8+ T cells showed decreased expression of inhibitory receptors, with reduced TIM3, LAG3, and BTLA checkpoint expression. In human PBMCs in vitro, BET inhibition reduced expression of immune checkpoints in CD4+ and CD8+ T cells, restoring effector cytokines and downregulating the transcriptional driver TOX. BET proteins in melanoma may play an oncogenic role by inducing immune suppression and driving T cell dysfunction. The study demonstrates an effective combination for innately unresponsive melanoma patients to checkpoint inhibitor immunotherapy, yet highlights BET inhibitors' limitations in an acquired resistance context.

Tumour-intrinsic PDL1 signals regulate the Chk2 DNA damage response in cancer cells and mediate resistance to Chk1 inhibitors

BACKGROUND

Aside from the canonical role of PDL1 as a tumour surface-expressed immune checkpoint molecule, tumour-intrinsic PDL1 signals regulate non-canonical immunopathological pathways mediating treatment resistance whose significance, mechanisms, and therapeutic targeting remain incompletely understood. Recent reports implicate tumour-intrinsic PDL1 signals in the DNA damage response (DDR), including promoting homologous recombination DNA damage repair and mRNA stability of DDR proteins, but many mechanistic details remain undefined.

METHODS

We genetically depleted PDL1 from transplantable mouse and human cancer cell lines to understand consequences of tumour-intrinsic PDL1 signals in the DNA damage response. We complemented this work with studies of primary human tumours and inducible mouse tumours. We developed novel approaches to show tumour-intrinsic PDL1 signals in specific subcellular locations. We pharmacologically depleted tumour PDL1 in vivo in mouse models with repurposed FDA-approved drugs for proof-of-concept clinical translation studies.

RESULTS

We show that tumour-intrinsic PDL1 promotes the checkpoint kinase-2 (Chk2)-mediated DNA damage response. Intracellular but not surface-expressed PDL1 controlled Chk2 protein content post-translationally and independently of PD1 by antagonising PIRH2 E3 ligase-mediated Chk2 polyubiquitination and protein degradation. Genetic tumour PDL1 depletion specifically reduced tumour Chk2 content but not ATM, ATR, or Chk1 DDR proteins, enhanced Chk1 inhibitor (Chk1i) synthetic lethality in vitro in diverse human and murine tumour models, and improved Chk1i efficacy in vivo. Pharmacologic tumour PDL1 depletion with cefepime or ceftazidime replicated genetic tumour PDL1 depletion by reducing tumour Chk2, inducing Chk1i synthetic lethality in a tumour PDL1-dependent manner, and reducing in vivo tumour growth when combined with Chk1i.

CONCLUSIONS

Our data challenge the prevailing surface PDL1 paradigm, elucidate important and previously unappreciated roles for tumour-intrinsic PDL1 in regulating the ATM/Chk2 DNA damage response axis and E3 ligase-mediated protein degradation, suggest tumour PDL1 as a biomarker for Chk1i efficacy, and support the rapid clinical potential of pharmacologic tumour PDL1 depletion to treat selected cancers.

Ring Transformation of Cyclopropenes to Benzo-Fused Five-Membered Oxa- and Aza-Heterocycles via a Formal [4+1] Cyclization

In the context of the growing importance of heterocyclic compounds across various disciplines, numerous strategies for their construction have emerged. Exploiting the distinctive properties of cyclopropenes, this study introduces an innovative approach for the synthesis of benzo-fused five-membered oxa- and aza-heterocycles through a formal [4+1] cyclization and subsequent acid-catalyzed intramolecular O- to N- rearrangement. These transformations exhibit mild reaction conditions and a wide substrate scope. The applications in the late-stage modification of complex molecules and in the synthesis of a potential PD-L1 gene down-regulator, make this method highly appealing in related fields. Combined experimental mechanistic studies and DFT calculations demonstrate Rh(III)-mediated sequential C─H coupling/π-allylation/dynamically favorable O-attack route.

Immunological hide-and-seek: epigenetically reprogrammed cancer cells and the dynamics of CD8+ T cells

Cancer remains a global health burden, shaped by both genetic mutations and epigenetic dysregulation. Epigenetic alteration plays a pivotal role in tumorigenesis, immune response modulation, and the emergence of treatment resistance. This review emphasizes the intricate interplay between epigenetically reprogrammed cancer cells and the tumor microenvironment (TME), a relationship central to the immunoediting concept, which encompasses elimination, equilibrium, and escape phases. This review highlights the significance of CD8+ T cells as potent anticancer agents and discusses the mechanisms by which tumor cells evade immune surveillance and evolve resistance to immunotherapy. Such evasion entails the regulation of inhibitory molecules, antigen presentation machinery, and cytokine milieu. Furthermore, this review explores the complex dynamics culminating in CD8+ T cell dysfunction within the TME. In summary, this work offers insights into the indispensable role of epigenetic mechanisms in bolstering cancer cell survival amidst immunological challenges within the TME.

Decoding functional impact of epigenetic regulator mutations on ligand-receptor interaction perturbations for evaluation of cancer immunotherapy

Cellular crosstalk mediated by ligand-receptor interactions largely complicates the tumour ecosystem, resulting in heterogeneous tumour microenvironments that affect immune response and clinical benefits from immunotherapy. Epigenetic mechanisms are pivotal to expression changes of immune-related genes and can modulate the anti-tumour immune response. However, the functional consequences of disrupted epigenetic regulators (ERs) on ligand-receptor interactions in the tumour microenvironment remain largely unexplored. Here, we proposed mutations of ERs in perturbed interactions (MERIN), a molecular network-based approach that incorporates multi-omics data, to infer the potential consequences of ER mutations on ligand-receptor interaction perturbations. Leveraging cancer genomic profiles and molecular interaction data, we comprehensively decoded the functional consequences of ER mutations on dysregulated ligand-receptor interactions across 33 cancers. The dysregulated ligand-receptor genes were indeed enriched in cancer and immune-related function. We demonstrated the potential significance of PD1-PDL1 interaction-related ER mutations in stratifying cancer patients from multiple independent data cohorts. The ER mutation group showed distinct immunological characterizations and prognoses. Furthermore, we highlighted that the ER mutations could potentially predict clinical outcomes of immunotherapy. Our computational and clinical assessment underscore the utility of MERIN for elucidating the functional relevance of ER mutations in cancer immune response, potentially aiding patients' stratification for immunotherapy.

Mitochondria-Targeted Multifunctional Nanoparticles Combine Cuproptosis and Programmed Cell Death-1 Downregulation for Cancer Immunotherapy

The combination of cuproptosis and immune checkpoint inhibition has shown promise in treating malignant tumors. However, it remains a challenge to deliver copper ions and immune checkpoint inhibitors efficiently and simultaneously to tumors. Herein, a mitochondria-targeted nanoscale coordination polymer particle, Cu/TI, comprising Cu(II), and a triphenylphosphonium conjugate of 5-carboxy-8-hydroxyquinoline (TI), for effective cuproptosis induction and programmed cell death-1 (PD-L1) downregulation is reported. Upon systemic administration, Cu/TI efficiently accumulates in tumor tissues to induce immunogenic cancer cell death and reduce PD-L1 expression. Consequently, Cu/TI promotes the intratumoral infiltration and activation of cytotoxic T lymphocytes to greatly inhibit tumor progression of colorectal carcinoma and triple-negative breast cancer in mouse models without causing obvious side effects.

Autophagy-related biomarkers in hepatocellular carcinoma and their relationship with immune infiltration

BACKGROUND

Autophagy regulation plays vital roles in many cancers. We aimed to investigate the expression, prognostic value, and immune infiltration of autophagy-related genes in hepatocellular carcinoma (HCC) by bioinformatics analysis.

METHOD

Human autophagy-related differentially expressed genes (DEGs) between adjacent and HCC tissues were identified. We performed Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. We also evaluated immune infiltration and the response to tumor-sensitive drugs. Finally, we verified the expression of these proteins in clinical samples by immunohistochemistry (IHC), RNA isolation and real-time reverse transcription polymerase chain reaction (RT‒PCR).

RESULTS

A total of 57 autophagy-related DEGs were identified. The HUB genes (BIRC5, CDKN2A, SPP1, and IGF1) were related to the diagnosis and prognosis of HCC. The HUB genes were significantly enriched in immune-related pathways. Furthermore, correlation analysis revealed that HUB gene expression was associated with immune infiltration. We identified 35 tumor-sensitive drugs targeting the HUB genes. Finally, by IHC, we discovered that the protein of CDKN2A, BIRC5, and SPP1 were upregulated in HCC tissues, while IGF1 was downregulated in HCC tissues compared with the levels in paracarcinoma tissues; by RT‒PCR, we discovered that the mRNA of CDKN2A, BIRC5, and SPP1 were upregulated in HCC tissues, while the mRNA of IGF1 was downregulated in HCC tissues compared with the levels in paracarcinoma tissues.

CONCLUSION

We screened and validated four autophagy-related genes associated with immune infiltration and prognosis in patients with HCC.

Ultrasound-Activated PROTAC Prodrugs Overcome Immunosuppression to Actuate Efficient Deep-Tissue Sono-Immunotherapy in Orthotopic Pancreatic Tumor Mouse Models

The degradation of oncoproteins mediated by proteolysis-targeting chimera (PROTAC) has emerged as a potent strategy in cancer therapy. However, the clinical application of PROTACs is hampered by challenges such as poor water solubility and off-target adverse effects. Herein, we present an ultrasound (US)-activatable PROTAC prodrug termed NPCe6+PRO for actuating efficient sono-immunotherapy in a spatiotemporally controllable manner. Specifically, US irradiation, which exhibits deep-tissue penetration capability, results in Ce6-mediated generation of ROS, facilitating sonodynamic therapy (SDT) and inducing immunogenic cell death (ICD). Simultaneously, the generated ROS cleaves the thioketal (TK) linker through a ROS-responsive mechanism, realizing the on-demand activation of the PROTAC prodrug in deep tissues. This prodrug activation results in the degradation of the target protein BRD4, while simultaneously reversing the upregulation of PD-L1 expression associated with the SDT process. In the orthotopic mouse model of pancreatic tumors, NPCe6+PRO effectively suppressed tumor growth in conjunction with US stimulation.

PPARα phosphorylation regulates colorectal tumor immune escape

A high level of PD-L1 in cancer cells promotes tumor immune escape and inhibits tumor immunotherapy. Although PD-L1 gene expression is upregulated by multiple pathways, its gene transcriptional repression is still unclear. Here we found that loss of PPARα, one of the peroxisome-proliferator-activated receptors (PPARs) family members, promoted colorectal tumor immune escape. Mechanistically, PPARα directly bound to the PD-L1 promoter resulting in its gene transcriptional repression, which in turn increased T cell activity, and PPARα agonist enhanced this event. However, ERK induced PPARα-S12 phosphorylation leading to blockade of PPARα-mediated PD-L1 transcriptional repression, and the combination of ERK inhibitor with PPARα agonist significantly inhibited tumor immune escape. These findings suggest that the ERK-PPARα pathway inhibited PD-L1 gene transcriptional repression and promoted colorectal tumor immune escape.

CAR-T therapy and targeted treatments: Emerging combination strategies in solid tumors

CAR-T cell therapies hold great potential in achieving long-term remission in patients suffering from malignancies. However, their efficacy in treating solid tumors is impeded by challenges such as limited infiltration, compromised cancer recognition, decreased cytotoxicity, heightened exhaustion, absence of memory phenotypes, and inevitable toxicity. To surmount these obstacles, researchers are exploring innovative strategies, including the integration of CAR-T cells with targeted inhibitors. The combination of CAR-T therapies with specific targeted drugs has shown promise in enhancing CAR-T cell infiltration into tumor sites, boosting their tumor recognition capabilities, strengthening their cytotoxicity, alleviating exhaustion, promoting the development of a memory phenotype, and reducing toxicity. By harnessing the synergistic potential, a wider range of patients with solid tumors may potentially experience favorable outcomes. To summarize the current combined strategies of CAR-T therapies and targeted therapies, outline the potential mechanisms, and provide insights for future studies, we conducted this review by collecting existing experimental and clinical evidence.

GSK0660 enhances antitumor immunotherapy by reducing PD-L1 expression

Blockade of PD-1/PD-L1 immune checkpoint is wildly used for multiple types of cancer treatment, while the low response rate for patients is still completely unknown. As nuclear hormone receptor, PPARδ (peroxisome-proliferator-activated receptor) regulates cell proliferation, inflammation, and tumor progression, while the effect of PPARδ on tumor immune escape is still unclear. Here we found that PPARδ antagonist GSK0660 significantly reduced colon cancer cell PD-L1 protein and gene expression. Luciferase analysis showed that GSK0660 decreased PD-L1 gene transcription activity. Moreover, reduced PD-L1 expression in colon cancer cells led to increased T cell activity. Further analysis showed that GSK0660 decreased PD-L1 expression in a PPARδ dependent manner. Implanted tumor model analysis showed that GSK0660 inhibited tumor immune escape and the combined PD-1 antibody with GSK0660 effectively enhanced colorectal cancer immunotherapy. These findings suggest that GSK0660 treatment could be an effective strategy for cancer immunotherapy.

Biochemical hallmarks-targeting antineoplastic nanotherapeutics

Tumor microenvironments (TMEs) have received increasing attention in recent years as they play pivotal roles in tumorigenesis, progression, metastases, and resistance to the traditional modalities of cancer therapy like chemotherapy. With the rapid development of nanotechnology, effective antineoplastic nanotherapeutics targeting the aberrant hallmarks of TMEs have been proposed. The appropriate design and fabrication endow nanomedicines with the abilities for active targeting, TMEs-responsiveness, and optimization of physicochemical properties of tumors, thereby overcoming transport barriers and significantly improving antineoplastic therapeutic benefits. This review begins with the origins and characteristics of TMEs and discusses the latest strategies for modulating the TMEs by focusing on the regulation of biochemical microenvironments, such as tumor acidosis, hypoxia, and dysregulated metabolism. Finally, this review summarizes the challenges in the development of smart anti-cancer nanotherapeutics for TME modulation and examines the promising strategies for combination therapies with traditional treatments for further clinical translation.

Epigenetic modulations in triple-negative breast cancer: Therapeutic implications for tumor microenvironment

Triple-negative breast cancer (TNBC) is an aggressive subtype lacking estrogen receptors, progesterone receptors and lacks HER2 overexpression. This absence of critical molecular targets poses significant challenges for conventional therapies. Immunotherapy, remarkably immune checkpoint blockade, offers promise for TNBC treatment, but its efficacy remains limited. Epigenetic dysregulation, including altered DNA methylation, histone modifications, and imbalances in regulators such as BET proteins, plays a crucial role in TNBC development and resistance to treatment. Hypermethylation of tumor suppressor gene promoters and the imbalance of histone methyltransferases such as EZH2 and histone deacetylases (HDACs) profoundly influence tumor cell proliferation, survival, and metastasis. In addition, epigenetic alterations critically shape the tumor microenvironment (TME), including immune cell composition, cytokine signaling, and immune checkpoint expression, ultimately contributing to immune evasion. Targeting these epigenetic mechanisms with specific inhibitors such as EZH2 and HDAC inhibitors in combination with immunotherapy represents a compelling strategy to remodel the TME, potentially overcoming immune evasion and enhancing therapeutic outcomes in TNBC. This review aims to comprehensively elucidate the current understanding of epigenetic modulation in TNBC, its influence on the TME, and the potential of combining epigenetic therapies with immunotherapy to overcome the challenges posed by this aggressive breast cancer subtype.

TRAF6 enhances PD-L1 expression through YAP1-TFCP2 signaling in melanoma

Immunotherapy represented by programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) monoclonal antibodies has led tumor treatment into a new era. However, the low overall response rate and high incidence of drug resistance largely damage the clinical benefits of existing immune checkpoint therapies. Recent studies correlate the response to PD-1/PD-L1 blockade with PD-L1 expression levels in tumor cells. Hence, identifying molecular targets and pathways controlling PD-L1 protein expression and stability in tumor cells is a major priority. In this study, we performed a Stress and Proteostasis CRISPR interference screening to identify PD-L1 positive modulators. Here, we identified TRAF6 as a critical regulator of PD-L1 in melanoma cells. As a non-conventional E3 ubiquitin ligase, TRAF6 is inclined to catalyze the synthesis and linkage of lysine-63 (K63) ubiquitin which is related to the stabilization of substrate proteins. Our results showed that suppression of TRAF6 expression down-regulates PD-L1 expression on the membrane surface of melanoma cells. We then used in vitro and in vivo assays to investigate the biological function and mechanism of TRAF6 and its downstream YAP1/TFCP2 signaling in melanoma. TRAF6 stabilizes YAP1 by K63 poly-ubiquitination modification, subsequently promoting the formation of YAP1/TFCP2 transcriptional complex and PD-L1 transcription. Inhibition of TRAF6 by Bortezomib enhanced cytolytic activity of CD8+ T cells by reduction of endogenous PD-L1. Notably, Bortezomib enhances anti-tumor immunity to an extent comparable to anti-PD-1 therapies with no obvious toxicity. Our findings reveal the potential of inhibiting TRAF6 to stimulate internal anti-tumor immunological effect for TRAF6-PD-L1 overexpressing cancers.

Development of pharmacological immunoregulatory anti-cancer therapeutics: current mechanistic studies and clinical opportunities

Immunotherapy represented by anti-PD-(L)1 and anti-CTLA-4 inhibitors has revolutionized cancer treatment, but challenges related to resistance and toxicity still remain. Due to the advancement of immuno-oncology, an increasing number of novel immunoregulatory targets and mechanisms are being revealed, with relevant therapies promising to improve clinical immunotherapy in the foreseeable future. Therefore, comprehending the larger picture is important. In this review, we analyze and summarize the current landscape of preclinical and translational mechanistic research, drug development, and clinical trials that brought about next-generation pharmacological immunoregulatory anti-cancer agents and drug candidates beyond classical immune checkpoint inhibitors. Along with further clarification of cancer immunobiology and advances in antibody engineering, agents targeting additional inhibitory immune checkpoints, including LAG-3, TIM-3, TIGIT, CD47, and B7 family members are becoming an important part of cancer immunotherapy research and discovery, as are structurally and functionally optimized novel anti-PD-(L)1 and anti-CTLA-4 agents and agonists of co-stimulatory molecules of T cells. Exemplified by bispecific T cell engagers, newly emerging bi-specific and multi-specific antibodies targeting immunoregulatory molecules can provide considerable clinical benefits. Next-generation agents also include immune epigenetic drugs and cytokine-based therapeutics. Cell therapies, cancer vaccines, and oncolytic viruses are not covered in this review. This comprehensive review might aid in further development and the fastest possible clinical adoption of effective immuno-oncology modalities for the benefit of patients.

Cancer Cell-Selective PD-L1 Inhibition via a DNA Safety Catch to Enhance Immunotherapy Specificity

Immune checkpoint protein blockade (ICB) has emerged as a powerful immunotherapy approach, but suppressing immune-related adverse events (irAEs) for noncancerous cells and normal tissues remains challenging. Activatable ICB has been developed with tumor microenvironment highly-expressed molecules as stimuli, but they still lack precision and efficiency considering the diffusion of stimuli molecules in whole tumor tissue. Here we assemble PD-L1 with a duplex DNA strand, termed as "safety catch", to regulate its accessibility for ICB. The safety catch remains at "on" status for noncancerous cells to prevent ICB binding to PD-L1. Cancer cell membrane protein c-Met acts as a trigger protein to react with safety catch, which selectively exposes its hybridization region for ICB reagent. The ICB reagent is a retractable DNA nanostring with repeating hairpin-structural units, whose contraction drives PD-L1 clustering with endocytosis-guided degradation. The safety catch, even remained at "safety on" status, is removed from the cell membrane via a DNA strand displacement reaction to minimize its influence on noncancerous cells. This strategy demonstrates selective and potent immunotherapeutic capabilities only against cancer cells both in vitro and in vivo, and shows effective suppression of irAEs in normal tissues, therefore would become a promising approach for precise immunotherapy in mice.

Reducing PD-L1 Expression by Degraders and Downregulators as a Novel Strategy to Target the PD-1/PD-L1 Pathway

Targeting the programmed cell death protein-1 (PD-1)/programmed cell death-ligand 1 (PD-L1) pathway has evolved into one of the most promising strategies for tumor immunotherapy. Thus far, multiple monoclonal antibody drugs have been approved for treating a variety of tumors, while the development of small-molecule PD-1/PD-L1 inhibitors has lagged far behind, with only a few small-molecule inhibitors entering clinical trials. In addition to antibody drugs and small-molecule inhibitors, reducing the expression levels of PD-L1 has attracted extensive research interest as another promising strategy to target the PD-1/PD-L1 pathway. Herein, we analyze the structures and mechanisms of molecules that reduce PD-L1 expression and classify them as degraders and downregulators according to whether they directly bind to PD-L1. Moreover, we discuss the potential prospects for developing PD-L1-targeting drugs based on these molecules. It is hoped that this perspective will provide profound insights into the discovery of potent antitumor immunity drugs.

Emerging therapeutic frontiers in cancer: insights into posttranslational modifications of PD-1/PD-L1 and regulatory pathways

The interaction between programmed cell death ligand 1 (PD-L1), which is expressed on the surface of tumor cells, and programmed cell death 1 (PD-1), which is expressed on T cells, impedes the effective activation of tumor antigen-specific T cells, resulting in the evasion of tumor cells from immune-mediated killing. Blocking the PD-1/PD-L1 signaling pathway has been shown to be effective in preventing tumor immune evasion. PD-1/PD-L1 blocking antibodies have garnered significant attention in recent years within the field of tumor treatments, given the aforementioned mechanism. Furthermore, clinical research has substantiated the efficacy and safety of this immunotherapy across various tumors, offering renewed optimism for patients. However, challenges persist in anti-PD-1/PD-L1 therapies, marked by limited indications and the emergence of drug resistance. Consequently, identifying additional regulatory pathways and molecules associated with PD-1/PD-L1 and implementing judicious combined treatments are imperative for addressing the intricacies of tumor immune mechanisms. This review briefly outlines the structure of the PD-1/PD-L1 molecule, emphasizing the posttranslational modification regulatory mechanisms and related targets. Additionally, a comprehensive overview on the clinical research landscape concerning PD-1/PD-L1 post-translational modifications combined with PD-1/PD-L1 blocking antibodies to enhance outcomes for a broader spectrum of patients is presented based on foundational research.

Targeted therapy, immunotherapy, and small molecules and peptidomimetics as emerging immunoregulatory agents for melanoma

Primary cutaneous melanoma is the most lethal of all skin neoplasms and its incidence is increasing. Clinical management of advanced melanoma in the last decade has been revolutionised by the availability of immunotherapies and targeted therapies, used alone and in combination. This article summarizes advances in the treatment of late-stage melanoma including use of protein kinase inhibitors, antibody-based immune checkpoint inhibitors, adoptive immunotherapy, vaccines and more recently, small molecules and peptidomimetics as emerging immunoregulatory agents.

Enhanced Electrochemical Characterization of the Immune Checkpoint Protein PD-L1 using Aptamer-Functionalized Magnetic Metal-Organic Frameworks

Programmed death ligand 1 (PD-L1) is highly expressed in cancer cells and participates in the immune escape process of tumor cells. However, as one of the most promising biomarkers for cancer immunotherapy monitoring, the key problem ahead of practical usage is how to effectively improve the detection sensitivity of PD-L1. Herein, an electrochemical aptasensor for the evaluation of tumor immunotherapy is developed based on the immune checkpoint protein PD-L1. The fundamental principle of this method involves the utilization of DNA nanotetrahedron (NTH)-based capture probes and aptamer-modified magnetic metal-organic framework nanocomposites as signaling probes. A synergistic enhancement is observed in the electrocatalytic effect between Fe3O4 and UiO-66 porous shells in Fe3O4@UiO-66 nanocomposites. Therefore, the integration of aptamer-modified Fe3O4@UiO-66@Au with NTH-assisted target immobilization as an electrochemical sensing platform can significantly enhance sensitivity and specificity for target detection. This method enables the detection of targets at concentrations as low as 7.76 pg mL-1 over a wide linear range (0.01 to 1000 ng mL-1). The authors have successfully employed this sensor for in situ characterization of PD-L1 on the cell surface and for monitoring changes in PD-L1 expression during drug therapy, providing a cost-effective yet robust alternative to highly expensive and expertise-dependent flow cytometry.

BET inhibitors drive Natural Killer activation in non-small cell lung cancer via BRD4 and SMAD3

Non-small-cell lung carcinoma (NSCLC) is the most common lung cancer and one of the pioneer tumors in which immunotherapy has radically changed patients' outcomes. However, several issues are emerging and their implementation is required to optimize immunotherapy-based protocols. In this work, we investigate the ability of the Bromodomain and Extra-Terminal protein inhibitors (BETi) to stimulate a proficient anti-tumor immune response toward NSCLC. By using in vitro, ex-vivo, and in vivo models, we demonstrate that these epigenetic drugs specifically enhance Natural Killer (NK) cell cytotoxicity. BETi down-regulate a large set of NK inhibitory receptors, including several immune checkpoints (ICs), that are direct targets of the transcriptional cooperation between the BET protein BRD4 and the transcription factor SMAD3. Overall, BETi orchestrate an epigenetic reprogramming that leads to increased recognition of tumor cells and the killing ability of NK cells. Our results unveil the opportunity to exploit and repurpose these drugs in combination with immunotherapy.

Recent advances and mechanisms of action of PD-L1 degraders as potential therapeutic agents

PD-L1 is an important immune checkpoint protein that can bind to T cells' PD-1 receptor, thereby promoting immune escape from tumors. In recent years, many researchers have developed strategies to degrade PD-L1 to improve the effect of immunotherapy. The study of degrading PD-L1 provides new opportunities for immunotherapy. Here, we mainly summarize and review the current active molecules and mechanisms that mediate the degradation of immature and mature PD-L1 during the post-translational modification stages, involving PD-L1 phosphorylation, glycosylation, palmitoylation, ubiquitination, and the autophagy-lysosomal process. This review expects that by degrading PD-L1 protein, we will not only gain a better understanding of oncogenic mechanisms involving tumor PD-L1 protein but also provide a new way to improve immunotherapy.

EPRIM: An approach of identifying cancer immune-related epigenetic regulators

Epigenetic regulation contributes to the dysregulation of gene expression involved in cancer biology. Nevertheless, the roles of epigenetic regulators (ERs) in tumor immunity and immune response remain basically unclear. Here, we developed the epigenetic regulator in immunology (EPRIM) approach to identify immune-related ERs and comprehensively dissected the ER regulation in tumor immune response across 33 cancers. The identified immune-related ERs were related to immune infiltration and could stratify cancer patients into two risk groups in multiple independent datasets. These patient groups were characterized by distinct immune functions, immune infiltrates, driver gene mutations, and prognoses. Furthermore, we constructed an immune ER-based signature and highlighted its potential utility in predicting clinical benefit from immunotherapy and selecting therapeutic agents. Taken together, our identification and evaluation of immune-related ERs highlight the usefulness of EPRIM for the understanding of ERs in immune regulation and the clinical relevance in evaluation of cancer patient prognosis and response to immune checkpoint blockade therapy.

Metabolic remodeling by the PD-L1 inhibitor BMS-202 significantly inhibits cell malignancy in human glioblastoma

Recently, crystallographic studies have demonstrated that BMS-202, a small-molecule compound characterized by a methoxy-1-pyridine chemical structure, exhibits a high affinity to PD-L1 dimerization. However, its roles and mechanisms in glioblastoma (GBM) remain unclear. The objective of this study is to investigate the antitumor activity of BMS-202 and its underlying mechanisms in GBM using multi-omics and bioinformatics techniques, along with a majority of in vitro and in vivo experiments, including CCK-8 assays, flow cytometry, co-immunoprecipitation, siRNA transfection, PCR, western blotting, cell migration/invasion assays and xenografts therapeutic assays. Our findings indicate that BMS-202 apparently inhibits the proliferation of GBM cells both in vitro and in vivo. Besides, it functionally blocks cell migration and invasion in vitro. Mechanistically, it reduces the expression of PD-L1 on the surface of GBM cells and interrupts the PD-L1-AKT-BCAT1 axis independent of mTOR signaling. Taken together, we conclude that BMS-202 is a promising therapeutic candidate for patients with GBM by remodeling their cell metabolism regimen, thus leading to better survival.

BET protein-dependent E2F pathway activity confers bell-shaped type resistance to tankyrase inhibitors in APC-mutated colorectal cancer

WNT/β-catenin signaling is aberrantly activated in colorectal cancer (CRC) mainly by loss-of-function mutations in adenomatous polyposis coli (APC) and is involved in tumor progression. Tankyrase inhibitors, which suppress WNT/β-catenin signaling, are currently in pre-clinical and clinical trials. However, the mechanisms of resistance to tankyrase inhibitors remain unclear. In this study, we established tankyrase inhibitor-resistant CRC cells, JC73-RK100, from APC-mutated patient-derived CRC cells. JC73-RK100 cells and several CRC cell lines were sensitive to tankyrase inhibitors at low concentrations but were resistant at high concentrations, showing an intrinsic/acquired bell-shaped dose response. Mechanistically, tankyrase inhibitors at high concentrations promoted BRD3/4-dependent E2F target gene transcription and over-activated cell cycle progression in these cells. BET inhibitors canceled the bell-shaped dose response to tankyrase inhibitors. Combination of tankyrase and BET inhibitors significantly suppressed tumor growth in a mouse xenograft model. These observations suggest that the combination of tankyrase and BET inhibitors may be a useful therapeutic approach to overcome the resistance of a subset of CRCs to tankyrase inhibitors.

Nano-Regulator Inhibits Tumor Immune Escape via the "Two-Way Regulation" Epigenetic Therapy Strategy

Tumor immune escape caused by low levels of tumor immunogenicity and immune checkpoint-dependent suppression limits the immunotherapeutic effect. Herein, a "two-way regulation" epigenetic therapeutic strategy is proposed using a novel nano-regulator that inhibits tumor immune escape by upregulating expression of tumor-associated antigens (TAAs) to improve immunogenicity and downregulating programmed cell death 1 ligand 1 (PD-L1) expression to block programmed death-1 (PD-1)/PD-L1. To engineer the nano-regulator, the DNA methyltransferase (DNMT) inhibitor zebularine (Zeb) and the bromodomain-containing protein 4 (BRD4) inhibitor JQ1 are co-loaded into the cationic liposomes with condensing the toll-like receptor 9 (TLR9) agonist cytosine-phosphate-guanine (CpG) via electrostatic interactions to obtain G-J/ZL. Then, asparagine-glycine-arginine (NGR) modified material carboxymethyl-chitosan (CMCS) is coated on the surface of G-J/ZL to construct CG-J/ZL. CG-J/ZL is shown to target tumor tissue and disassemble under the acidic tumor microenvironment (TME). Zeb upregulated TAAs expression to improve the immunogenicity; JQ1 inhibited PD-L1 expression to block immune checkpoint; CpG promote dendritic cell (DC) maturation and reactivated the ability of tumour-associated macrophages (TAM) to kill tumor cells. Taken together, these results demonstrate that the nano-regulator CG-J/ZL can upregulate TAAs expression to enhance T-cell infiltration and downregulate PD-L1 expression to improve the recognition of tumor cells by T-cells, representing a promising strategy to improve antitumor immune response.

From immune checkpoints to therapies: understanding immune checkpoint regulation and the influence of natural products and traditional medicine on immune checkpoint and immunotherapy in lung cancer

Lung cancer is a disease of global concern, and immunotherapy has brought lung cancer therapy to a new era. Besides promising effects in the clinical use of immune checkpoint inhibitors, immune-related adverse events (irAEs) and low response rates are problems unsolved. Natural products and traditional medicine with an immune-modulating nature have the property to influence immune checkpoint expression and can improve immunotherapy's effect with relatively low toxicity. This review summarizes currently approved immunotherapy and the current mechanisms known to regulate immune checkpoint expression in lung cancer. It lists natural products and traditional medicine capable of influencing immune checkpoints or synergizing with immunotherapy in lung cancer, exploring both their effects and underlying mechanisms. Future research on immune checkpoint modulation and immunotherapy combination applying natural products and traditional medicine will be based on a deeper understanding of their mechanisms regulating immune checkpoints. Continued exploration of natural products and traditional medicine holds the potential to enhance the efficacy and reduce the adverse reactions of immunotherapy.

NSD3 in Cancer: Unraveling Methyltransferase-Dependent and Isoform-Specific Functions

NSD3 (nuclear receptor-binding SET domain protein 3) is a member of the NSD histone methyltransferase family of proteins. In recent years, it has been identified as a potential oncogene in certain types of cancer. The NSD3 gene encodes three isoforms, the long version (NSD3L), a short version (NSD3S) and the WHISTLE isoforms. Importantly, the NSD3S isoform corresponds to the N-terminal region of the full-length protein, lacking the methyltransferase domain. The chromosomal location of NSD3 is frequently amplified across cancer types, such as breast, lung, and colon, among others. Recently, this amplification has been correlated to a chromothripsis event, that could explain the different NSD3 alterations found in cancer. The fusion proteins containing NSD3 have also been reported in leukemia (NSD3-NUP98), and in NUT (nuclear protein of the testis) midline carcinoma (NSD3-NUT). Its role as an oncogene has been described by modulating different cancer pathways through its methyltransferase activity, or the short isoform of the protein, through protein interactions. Specifically, in this review we will focus on the functions that have been characterized as methyltransferase dependent, and those that have been correlated with the expression of the NSD3S isoform. There is evidence that both the NSD3L and NSD3S isoforms are relevant for cancer progression, establishing NSD3 as a therapeutic target. However, further functional studies are needed to differentiate NSD3 oncogenic activity as dependent or independent of the catalytic domain of the protein, as well as the contribution of each isoform and its clinical significance in cancer progression.