Combination Approaches to Target PD-1 Signaling in Cancer

Exploring immune checkpoint inhibitors: Focus on PD-1/PD-L1 axis and beyond

Immunotherapy emerges as a promising approach, marked by recent substantial progress in elucidating how the host immune response impacts tumor development and its sensitivity to various treatments. Immune checkpoint inhibitors have revolutionized cancer therapy by unleashing the power of the immune system to recognize and eradicate tumor cells. Among these, inhibitors targeting the programmed cell death protein 1 (PD-1) and its ligand (PD-L1) have garnered significant attention due to their remarkable clinical efficacy across various malignancies. This review delves into the mechanisms of action, clinical applications, and emerging therapeutic strategies surrounding PD-1/PD-L1 blockade. We explore the intricate interactions between PD-1/PD-L1 and other immune checkpoints, shedding light on combinatorial approaches to enhance treatment outcomes and overcome resistance mechanisms. Furthermore, we discuss the expanding landscape of immune checkpoint inhibitors beyond PD-1/PD-L1, including novel targets such as CTLA-4, LAG-3, TIM-3, and TIGIT. Through a comprehensive analysis of preclinical and clinical studies, we highlight the promise and challenges of immune checkpoint blockade in cancer immunotherapy, paving the way for future advancements in the field.

VRK2 kinase pathogenic pathways in cancer and neurological diseases

The VRK2 ser-thr kinase, belonging to the dark kinome, is implicated in the pathogenesis of cancer progression, neurological and psychiatric diseases. The VRK2 gene codes for two isoforms. The main isoform (VRK2A) is mainly located in the cytoplasm, and anchored to different types of membranes, such as the endoplasmic reticulum, mitochondria and nuclear envelope. The VRK2A isoform interacts with signaling modules assembled on scaffold proteins such as JIP1 or KSR1, forming stable complexes and blocking the activation of regulatory signaling pathways by altering their intracellular localization and the balance among them. VRK2 regulates apoptosis, nuclear membrane organization, immune responses, and Cajal bodies. Wild-type VRK2 is overexpressed in tumors and contributes to cancer development. In cells and tumors with low levels of nuclear VRK1, VRK2 generates by alternative splicing a shorter isoform (VRK2B) that lacks the C-terminal hydrophobic tail and permits its relocation to nuclei. Furthermore, rare VRK2 gene variants are associated with different neurological or psychiatric diseases such as schizophrenia, epilepsy, bipolar disorder, depression, autism, circadian clock alterations and insomnia, but their pathogenic mechanism is unknown. These diseases are a likely consequence of an altered balance among different signaling pathways that are regulated by VRK2.

HERV Modulation in Colorectal Carcinoma Patients: A Snapshot of Endogenous Retroviral Transcriptome

Human endogenous retroviruses (HERVs) are proviral relics of infections that affected primates' germ line. Many HERV elements retain a residual capacity to encode transcripts and proteins that have been occasionally domesticated for the host physiology. In addition, HERV transcriptional modulation is of great interest to clarify the etiology of complex disorders such as cancer, even if a few studies assessed the specific HERV loci modulated in tumor tissues. In the present work, we used a transcriptomic approach to investigate the specific expression of ~3300 HERV loci in paired tumor and normal tissues of 7 colorectal cancer (CRC) patients. A total of 102 HERVs were significantly modulated in CRC, with a general tendency towards downregulation. Of note, among the 42 upregulated HERVs 23 belonged to the HERV-H group, that is the most investigated in CRC. De novo transcriptome reconstruction and qPCR validation allowed to identify a transcript from a HERV-H locus on chromosome Xp22.3 with high specific expression in CRC samples, potentially encoding for a partial Pol protein. These results provide a detailed description of HERV transcriptional variations in CRC and its interindividual variability, identifying a HERV-H transcript that deserves further investigation for its possible impact on tumor progression.

CITRINO: phase 1 dose escalation study of anti-LAG-3 antibody encelimab alone or in combination with anti-PD-1 dostarlimab in patients with advanced/metastatic solid tumours

BACKGROUND

Dual programmed cell death protein (ligand)-1 (PD-[L]1) and lymphocyte-activation gene-3 (LAG-3) blockade has demonstrated improved anti-tumour response in some advanced solid tumours. CITRINO, a two-part, Phase 1 dose-escalation study, evaluated encelimab (TSR-033; novel anti-LAG-3) monotherapy and in combination in patients with advanced/metastatic solid tumours.

METHODS

Part 1 (P1) involved dose escalation (20-720 mg Q2W) of encelimab as monotherapy (P1A/B) and with dostarlimab (500 mg Q3W) in patients with previously treated advanced/metastatic solid tumours (P1C). P2 involved cohort expansion in patients with anti-PD-(L)1-naïve microsatellite stable advanced/metastatic colorectal cancer with recommended phase 2 dose (RP2D) of encelimab with dostarlimab as third/fourth-line therapy (P2A), or with dostarlimab, bevacizumab and mFOLFOX6/FOLFIRI as second-line therapy (P2B). Objectives included RP2D, safety/tolerability, efficacy, pharmacokinetics/pharmacodynamics, and exploratory biomarkers.

RESULTS

Maximum tolerated encelimab dose was not reached; 720 mg Q2W was used for P2 plus dostarlimab 1000 mg Q6W. One dose-limiting toxicity occurred (Grade 2 myasthenia gravis; P1A). No clinical responses were observed in P1; 1 (3%) and 4 (17%) patients achieved partial response in P2A and 2B, respectively.

CONCLUSIONS

Encelimab has a manageable safety profile as a monotherapy and in tested combinations; however, anti-tumour activity was limited.

CLINICAL TRIAL REGISTRATION

NCT03250832.

PAG orchestrates T cell immune synapse function by binding to actin

Many immunotherapies impact T cell function by impacting the immune synapse. While immunotherapy is extremely successful in some patients, in many others, it fails to help or causes complications, including immune-related adverse events. Phosphoprotein Associated with Glycosphingolipid Rich Microdomains 1 (PAG) is a transmembrane scaffold protein with importance in T cell signaling. PAG has 10 tyrosine phosphorylation sites where many kinases and phosphatases bind. PAG is palmitoylated, so it localizes in lipid rafts of the membrane, and contains a C-terminal PDZ domain to link to the actin cytoskeleton. As a link between signaling-protein-rich membrane regions and the actin cytoskeleton, PAG is an exciting and novel target for manipulating immune function. Here, we sought to determine if PAG works with actin to control T cell synapse organization and function. We found that PAG and actin dynamics are tightly coordinated during synapse maturation. A PDZ domain mutation disrupts the PAG-actin interaction, significantly impairing synapse formation, stability, and function. To assess the impact of the PDZ mutation functionally in vivo, we employed a mouse model of type IV hypersensitivity and an OVA-tumor mouse model. In both systems, mice with T cells expressing PDZ-mutant PAG had diminished immune responses, including impaired cytotoxic function. These findings highlight the importance of the PAG-actin link for effective T cell immune synapse formation and function. The results of our study suggest that targeting PAG is a promising approach for modulating immune responses and treating immune-related diseases.

One Sentence Summary

Adaptor protein PAG links to the actin cytoskeleton, and this link is essential for T cell synapse formation and cytotoxic function.

Radiation drives tertiary lymphoid structures to reshape TME for synergized antitumour immunity

Radiotherapy (RT) plays a key role in the tumour microenvironment (TME), impacting the immune response via cellular and humoral immunity. RT can induce local immunity to modify the TME. It can stimulate dendritic cell maturation and T-cell infiltration. Moreover, B cells, macrophages and other immune cells may also be affected. Tertiary lymphoid structure (TLS) is a unique structure within the TME and a class of aggregates containing T cells, B cells and other immune cells. The maturation of TLS is determined by the presence of mature dendritic cells, the density of TLS is determined by the number of immune cells. TLS maturation and density both affect the antitumour immune response in the TME. This review summarized the recent research on the impact and the role of RT on TLS, including the changes of TLS components and formation conditions and the mechanism of how RT affects TLS and transforms the TME. RT may promote TLS maturation and density to modify the TME regarding enhanced antitumour immunity.

Changing the location of proteins on the cell surface is a promising strategy for modulating T cell functions

Targeting immune receptors on T cells is a common strategy to treat cancer and autoimmunity. Frequently, this is accomplished through monoclonal antibodies targeting the ligand binding sites of stimulatory or inhibitory co-receptors. Blocking ligand binding prevents downstream signalling and modulates specific T cell functions. Since 1985, the FDA has approved over 100 monoclonal antibodies against immune receptors. This therapeutic approach significantly improved the care of patients with numerous immune-related conditions; however, many patients are unresponsive, and some develop immune-related adverse events. One reason for that is the lack of consideration for the localization of these receptors on the cell surface of the immune cells in the context of the immune synapse. In addition to blocking ligand binding, changing the location of these receptors on the cell surface within the different compartments of the immunological synapse could serve as an alternative, efficient, and safer approach to treating these patients. This review discusses the potential therapeutic advantages of altering proteins' localization within the immune synapse and summarizes published work in this field. It also discusses the novel use of bispecific antibodies to induce the clustering of receptors on the cell surface. It presents the rationale for developing novel antibodies, targeting the organization of signalling receptor complexes on the cell surface. This approach offers an innovative and emerging technology to treat cancer patients resistant to current immunotherapies.

Exclusion of PD-1 from the immune synapse: A novel strategy to modulate T cell function

Targeting immune checkpoint receptors on T cells is a common cancer treatment strategy. Frequently, this is accomplished through antibodies targeting the ligand of inhibitory co-receptors. Blocking the immune checkpoint PD-1 binding to its ligands PD-L1 and PD-L2 prevents downstream signaling and enhances anti-tumor T cell responses. This approach improves cancer patients' outcomes. However, only one-third of the patients respond to these treatments. To better understand the mechanism of anti-PD-1 antibodies, we explored the location of PD-1 within the immune synapse. Surprisingly, we discovered that anti-PD-1 antibodies, besides blocking the interaction between PD-1 and its ligands, also removed PD-1 from the synapse. We demonstrated a correlation between removing PD-1 from the synapse by anti-PD-1 antibodies and the extent of T cell activation. Interestingly, a short version of the anti-PD-1 antibody, F(ab')2, failed to remove PD-1 from the synapse and activate T cells. Using the syngeneic tumor model, we showed a superior anti-tumor effect of the anti-PD-1 antibody over the shorter version of the same antibody. Our data indicate that anti-PD-1 antibodies activate T cells by removing PD-1 from the synapse, and changing the location of PD-1 or other immune receptors within the immune synapse could serve as an alternative, efficient approach to treat cancer.

Lck Function and Modulation: Immune Cytotoxic Response and Tumor Treatment More Than a Simple Event

Lck, a member of the Src kinase family, is a non-receptor tyrosine kinase involved in immune cell activation, antigen recognition, tumor growth, and cytotoxic response. The enzyme has usually been linked to T lymphocyte activation upon antigen recognition. Lck activation is central to CD4, CD8, and NK activation. However, recently, it has become clearer that activating the enzyme in CD8 cells can be independent of antigen presentation and enhance the cytotoxic response. The role of Lck in NK cytotoxic function has been controversial in a similar fashion as the role of the enzyme in CAR T cells. Inhibiting tyrosine kinases has been a highly successful approach to treating hematologic malignancies. The inhibitors may be useful in treating other tumor types, and they may be useful to prevent cell exhaustion. New, more selective inhibitors have been documented, and they have shown interesting activities not only in tumor growth but in the treatment of autoimmune diseases, asthma, and graft vs. host disease. Drug repurposing and bioinformatics can aid in solving several unsolved issues about the role of Lck in cancer. In summary, the role of Lck in immune response and tumor growth is not a simple event and requires more research.

Cancer therapy by cyclin-dependent kinase inhibitors (CDKIs): bench to bedside

A major characteristic of cancer is dysregulated cell division, which results in aberrant growth of cells. Consequently, medicinal targets that prevent cell division would be useful in the fight against cancer. The primary regulator of proliferation is a complex consisting of cyclin and cyclin-dependent kinases (CDKs). The FDA has granted approval for CDK inhibitors (CDKIs) to treat metastatic hormone receptor-positive breast cancer. Specifically, CDK4/6 CDKIs block the enzyme activity of CDK4 and CDK6. Unfortunately, the majority of first-generation CDK inhibitors, also known as pan-CDK inhibitors because they target multiple CDKs, have not been authorized for clinical use owing to their serious side effects and lack of selection. In contrast to this, significant advancements have been created to permit the use of pan-CDK inhibitors in therapeutic settings. Notably, the toxicity and negative consequences of pan-CDK inhibitors have been lessened in recent years thanks to the emergence of combination therapy tactics. Therefore, pan-CDK inhibitors have renewed promise for clinical use when used in a combination regimen. The members of the CDK family have been reviewed and their primary roles in cell cycle regulation were covered in this review. Next, we provided an overview of the state of studies on CDK inhibitors.

De Novo Purine Metabolism is a Metabolic Vulnerability of Cancers with Low p16 Expression

p16 is a tumor suppressor encoded by the CDKN2A gene whose expression is lost in approximately 50% of all human cancers. In its canonical role, p16 inhibits the G1-S-phase cell cycle progression through suppression of cyclin-dependent kinases. Interestingly, p16 also has roles in metabolic reprogramming, and we previously published that loss of p16 promotes nucleotide synthesis via the pentose phosphate pathway. However, the broader impact of p16/CDKN2A loss on other nucleotide metabolic pathways and potential therapeutic targets remains unexplored. Using CRISPR knockout libraries in isogenic human and mouse melanoma cell lines, we determined several nucleotide metabolism genes essential for the survival of cells with loss of p16/CDKN2A. Consistently, many of these genes are upregulated in melanoma cells with p16 knockdown or endogenously low CDKN2A expression. We determined that cells with low p16/CDKN2A expression are sensitive to multiple inhibitors of de novo purine synthesis, including antifolates. Finally, tumors with p16 knockdown were more sensitive to the antifolate methotrexate in vivo than control tumors. Together, our data provide evidence to reevaluate the utility of these drugs in patients with p16/CDKN2Alow tumors as loss of p16/CDKN2A may provide a therapeutic window for these agents.

SIGNIFICANCE

Antimetabolites were the first chemotherapies, yet many have failed in the clinic due to toxicity and poor patient selection. Our data suggest that p16 loss provides a therapeutic window to kill cancer cells with widely-used antifolates with relatively little toxicity.

Synthesis and structure-activity optimization of azepane-containing derivatives as PTPN2/PTPN1 inhibitors

Protein tyrosine phosphatases PTPN2 and PTPN1 (also known as PTP1B) have been implicated in a number of intracellular signaling pathways of immune cells. The inhibition of PTPN2 and PTPN1 has emerged as an attractive approach to sensitize T cell anti-tumor immunity. Two small molecule inhibitors have been entered the clinic. Here we report the design and development of compound 4, a novel small molecule PTPN2/N1 inhibitor demonstrating nanomolar inhibitory potency, good in vivo oral bioavailability, and robust in vivo antitumor efficacy.

The enhanced antitumor activity of bispecific antibody targeting PD-1/PD-L1 signaling

The programmed cell death 1 (PD-1) signaling pathway, a key player in immune checkpoint regulation, has become a focal point in cancer immunotherapy. In the context of cancer, upregulated PD-L1 on tumor cells can result in T cell exhaustion and immune evasion, fostering tumor progression. The advent of PD-1/PD-L1 inhibitor has demonstrated clinical success by unleashing T cells from exhaustion. Nevertheless, challenges such as resistance and adverse effects have spurred the exploration of innovative strategies, with bispecific antibodies (BsAbs) emerging as a promising frontier. BsAbs offer a multifaceted approach to cancer immunotherapy by simultaneously targeting PD-L1 and other immune regulatory molecules. We focus on recent advancements in PD-1/PD-L1 therapy with a particular emphasis on the development and potential of BsAbs, especially in the context of solid tumors. Various BsAb products targeting PD-1 signaling are discussed, highlighting their unique mechanisms of action and therapeutic potential. Noteworthy examples include anti-TGFβ × PD-L1, anti-CD47 × PD-L1, anti-VEGF × PD-L1, anti-4-1BB × PD-L1, anti-LAG-3 × PD-L1, and anti-PD-1 × CTLA-4 BsAbs. Besides, we summarize ongoing clinical studies evaluating the efficacy and safety of these innovative BsAb agents. By unraveling the intricacies of the tumor microenvironment and harnessing the synergistic effects of anti-PD-1/PD-L1 BsAbs, there exists the potential to elevate the precision and efficacy of cancer immunotherapy, ultimately enabling the development of personalized treatment strategies tailored to individual patient profiles.

Druggable targets of protein tyrosine phosphatase Family, viz. PTP1B, SHP2, Cdc25, and LMW-PTP: Current scenario on medicinal Attributes, and SAR insights

Protein tyrosine phosphatases (PTPs) are the class of dephosphorylation enzymes that catalyze the removal of phosphate groups from tyrosine residues on proteins responsible for various cellular processes. Any disbalance in signal pathways mediated by PTPs leads to various disease conditions like diabetes, obesity, cancers, and autoimmune disorders. Amongst the PTP superfamily, PTP1B, SHP2, Cdc25, and LMW-PTP have been prioritized as druggable targets for developing medicinal agents. PTP1B is an intracellular PTP enzyme that downregulates insulin and leptin signaling pathways and is involved in insulin resistance and glucose homeostasis. SHP2 is involved in the RAS-MAPK pathway and T cell immunity. Cdk-cyclin complex activation occurs by Cdc25-PTPs involved in cell cycle regulation. LMW-PTPs are involved in PDGF/PDGFR, Eph/ephrin, and insulin signaling pathways, resulting in certain diseases like diabetes mellitus, obesity, and cancer. The signaling cascades of PTP1B, SHP2, Cdc25, and LMW-PTPs have been described to rationalize their medicinal importance in the pathophysiology of diabetes, obesity, and cancer. Their binding sites have been explored to overcome the hurdles in discovering target selective molecules with optimum potency. Recent developments in the synthetic molecules bearing heterocyclic moieties against these targets have been explored to gain insight into structural features. The elaborated SAR investigation revealed the effect of substituents on the potency and target selectivity, which can be implicated in the further discovery of newer medicinal agents targeting the druggable members of the PTP superfamily.

Leukemia-intrinsic determinants of CAR-T response revealed by iterative in vivo genome-wide CRISPR screening

CAR-T therapy is a promising, novel treatment modality for B-cell malignancies and yet many patients relapse through a variety of means, including loss of CAR-T cells and antigen escape. To investigate leukemia-intrinsic CAR-T resistance mechanisms, we performed genome-wide CRISPR-Cas9 loss-of-function screens in an immunocompetent murine model of B-cell acute lymphoblastic leukemia (B-ALL) utilizing a modular guide RNA library. We identified IFNγR/JAK/STAT signaling and components of antigen processing and presentation pathway as key mediators of resistance to CAR-T therapy in vivo; intriguingly, loss of this pathway yielded the opposite effect in vitro (sensitized leukemia to CAR-T cells). Transcriptional characterization of this model demonstrated upregulation of these pathways in tumors relapsed after CAR-T treatment, and functional studies showed a surprising role for natural killer (NK) cells in engaging this resistance program. Finally, examination of data from B-ALL patients treated with CAR-T revealed an association between poor outcomes and increased expression of JAK/STAT and MHC-I in leukemia cells. Overall, our data identify an unexpected mechanism of resistance to CAR-T therapy in which tumor cell interaction with the in vivo tumor microenvironment, including NK cells, induces expression of an adaptive, therapy-induced, T-cell resistance program in tumor cells.

PD-1 inhibits T cell actin remodeling at the immunological synapse independently of its signaling motifs

Engagement of the receptor programmed cell death molecule 1 (PD-1) by its ligands PD-L1 and PD-L2 inhibits T cell-mediated immune responses. Blocking such signaling provides the clinical effects of PD-1-targeted immunotherapy. Here, we investigated the mechanisms underlying PD-1-mediated inhibition. Because dynamic actin remodeling is crucial for T cell functions, we characterized the effects of PD-1 engagement on actin remodeling at the immunological synapse, the interface between a T cell and an antigen-presenting cell (APC) or target cell. We used microscopy to analyze the formation of immunological synapses between PD-1+ Jurkat cells or primary human CD8+ cytotoxic T cells and APCs that presented T cell-activating antibodies and were either positive or negative for PD-L1. PD-1 binding to PD-L1 inhibited T cell spreading induced by antibody-mediated activation, which was characterized by the absence of the F-actin-dense distal lamellipodial network at the immunological synapse and the Arp2/3 complex, which mediates branched actin formation. PD-1-induced inhibition of actin remodeling also prevented the characteristic deformation of T cells that contact APCs and the release of cytotoxic granules. We showed that the effects of PD-1 on actin remodeling did not require its tyrosine-based signaling motifs, which are thought to mediate the co-inhibitory effects of PD-1. Our study highlights a previously unappreciated mechanism of PD-1-mediated suppression of T cell activity, which depends on the regulation of actin cytoskeleton dynamics in a signaling motif-independent manner.

PD-1 signaling uncovers a pathogenic subset of T cells in inflammatory arthritis

Background

PD-1 is an immune checkpoint on T cells and interventions to block this receptor result in T cell activation and enhanced immune response to tumors. Paired to that, and despite a decade of research, approaches to treat autoimmunity with PD-1 agonists still need to be more successful. To resolve this, new methods must be developed to augment PD-1 function beyond engaging the receptor.

Methods

We conducted a flow cytometry analysis of T cells isolated from the peripheral blood and synovial fluid of patients with rheumatoid arthritis. In addition, we performed a genome-wide CRISPR/Cas9 screen to identify genes associated with PD-1 signaling. We further analyzed genes involved in PD-1 signaling using publicly available bulk and single-cell RNA sequencing datasets.

Results

Our screen confirmed known regulators in proximal PD-1 signaling and, importantly, found an additional 1,112 unique genes related to PD-1 ability to inhibit T cell functions. These genes were strongly associated with the response of cancer patients to PD-1 blockades and with high tumor immune dysfunction and exclusion scores, confirming their role downstream of PD-1. Functional annotation revealed that more significant genes uncovered were those associated with known immune regulation processes. Remarkably, these genes were considerably downregulated in T cells isolated from patients with inflammatory arthritis, supporting their overall inhibitory functions. A study of rheumatoid arthritis single-cell RNA sequencing data demonstrated that five genes, KLRG1, CRTAM, SLAMF7, PTPN2, and KLRD1, were downregulated in activated and effector T cells isolated from synovial fluids. Back-gating these genes to canonical cytotoxic T cell signatures revealed PD-1 + HLA-DR HIGH KLRG LOW T cells as a novel inflammatory subset of T cells.

Conclusion

We concluded that PD-1 + HLA-DR HIGH KLRG LOW T cells are a potential target for future PD-1 agonists to treat inflammatory diseases. Our study uncovers new genes associated with PD-1 downstream functions and, therefore, provides a comprehensive resource for additional studies that are much needed to characterize the role of PD-1 in the synovial subset of T cells.

Exclusion of PD-1 from the immune synapse: a novel strategy to modulate T cell function

Targeting immune checkpoint receptors on T cells is a common cancer treatment strategy. Frequently, this is accomplished through antibodies targeting the ligand of inhibitory co-receptors. Blocking the immune checkpoint PD-1 binding to its ligands PD-L1 and PD-L2 prevents downstream signaling and enhances anti-tumor T cell responses. This approach improved cancer patients' outcome. However, only one-third of the patients respond to these treatments. To better understand the mechanism of anti-PD-1 antibodies, we explored the location of PD-1 within the immune synapse. Surprisingly, we discovered that anti-PD-1 antibodies, besides blocking the interaction between PD-1 and its ligands, also removed PD-1 from the synapse. We demonstrated a correlation between removing PD-1 from the synapse by anti-PD-1 antibodies and the extent of T cell activation. Interestingly, a short version of the anti-PD-1 antibody, F(ab') 2 , failed to remove PD-1 from the synapse and activate T cells. Using syngeneic tumor model, we showed a superior anti-tumor effect to anti-PD-1 antibody over the shorter version of the antibody. Our data indicates that anti-PD-1 antibodies activate T cells by removing PD-1 away from the synapse and changing the location of PD-1 or other immune receptors within immune synapse could serve as an alternative, efficient approach to treat cancer.

Manipulating TGF-β signaling to optimize immunotherapy for cervical cancer

Cervical cancer is a serious threat to women's health globally. Therefore, identifying key molecules associated with cervical cancer progression is essential for drug development, disease monitoring, and precision therapy. Recently, TGF-β (transforming growth factor-beta) has been identified as a promising target for cervical cancer treatment. For advanced cervical cancer, TGF-β participates in tumor development by improving metastasis, stemness, drug resistance, and immune evasion. Accumulating evidence demonstrates that TGF-β blockade effectively improves the therapeutic effects, especially immunotherapy. Currently, agents targeting TGF-β and immune checkpoints such as PD-L1 have been developed and tested in clinical studies. These bispecific antibodies might have the potential as therapeutic agents for cervical cancer treatment in the future.

De novo purine metabolism is a metabolic vulnerability of cancers with low p16 expression

p16 is a tumor suppressor encoded by the CDKN2A gene whose expression is lost in ~50% of all human cancers. In its canonical role, p16 inhibits the G1-S phase cell cycle progression through suppression of cyclin dependent kinases. Interestingly, p16 also has roles in metabolic reprogramming, and we previously published that loss of p16 promotes nucleotide synthesis via the pentose phosphate pathway. Whether other nucleotide metabolic genes and pathways are affected by p16/CDKN2A loss and if these can be specifically targeted in p16/CDKN2A-low tumors has not been previously explored. Using CRISPR KO libraries in multiple isogenic human and mouse melanoma cell lines, we determined that many nucleotide metabolism genes are negatively enriched in p16/CDKN2A knockdown cells compared to controls. Indeed, many of the genes that are required for survival in the context of low p16/CDKN2A expression based on our CRISPR screens are upregulated in p16 knockdown melanoma cells and those with endogenously low CDKN2A expression. We determined that cells with low p16/Cdkn2a expression are sensitive to multiple inhibitors of de novo purine synthesis, including anti-folates. Tumors with p16 knockdown were more sensitive to the anti-folate methotrexate in vivo than control tumors. Together, our data provide evidence to reevaluate the utility of these drugs in patients with p16/CDKN2A-low tumors as loss of p16/CDKN2A may provide a therapeutic window for these agents.

Mitochondrial DNA-targeted therapy: A novel approach to combat cancer

Mitochondrial DNA (mtDNA) encodes proteins and RNAs that are essential for mitochondrial function and cellular homeostasis, and participates in important processes of cellular bioenergetics and metabolism. Alterations in mtDNA are associated with various diseases, especially cancers, and are considered as biomarkers for some types of tumors. Moreover, mtDNA alterations have been found to affect the proliferation, progression and metastasis of cancer cells, as well as their interactions with the immune system and the tumor microenvironment (TME). The important role of mtDNA in cancer development makes it a significant target for cancer treatment. In recent years, many novel therapeutic methods targeting mtDNA have emerged. In this study, we first discussed how cancerogenesis is triggered by mtDNA mutations, including alterations in gene copy number, aberrant gene expression and epigenetic modifications. Then, we described in detail the mechanisms underlying the interactions between mtDNA and the extramitochondrial environment, which are crucial for understanding the efficacy and safety of mtDNA-targeted therapy. Next, we provided a comprehensive overview of the recent progress in cancer therapy strategies that target mtDNA. We classified them into two categories based on their mechanisms of action: indirect and direct targeting strategies. Indirect targeting strategies aimed to induce mtDNA damage and dysfunction by modulating pathways that are involved in mtDNA stability and integrity, while direct targeting strategies utilized molecules that can selectively bind to or cleave mtDNA to achieve the therapeutic efficacy. This study highlights the importance of mtDNA-targeted therapy in cancer treatment, and will provide insights for future research and development of targeted drugs and therapeutic strategies.

Extracellular Vesicles as Delivery Shippers for Noncoding RNA-Based Modulation of Angiogenesis: Insights from Ischemic Stroke and Cancer

Ischemic stroke and systemic cancer are two of the leading causes of mortality. Hypoxia is a central pathophysiological component in ischemic stroke and cancer, representing a joint medical function. This function includes angiogenesis regulation. Vascular remodeling coupled with axonal outgrowth following cerebral ischemia is critical in improving poststroke neurological functional recovery. Antiangiogenic strategies can inhibit cancer vascularization and play a vital role in impeding cancer growth, invasion, and metastasis. Although there are significant differences in the cause of angiogenesis across both pathophysiological conditions, emerging evidence states that common signaling structures, such as extracellular vesicles (EVs) and noncoding RNAs (ncRNAs), are involved in this context. EVs, heterogeneous membrane vesicles encapsulating proteomic genetic information from parental cells, act as multifunctional regulators of intercellular communication. Among the multifaceted roles in modulating biological responses, exhaustive evidence shows that ncRNAs are selectively sorted into EVs, modulating common specific aspects of cancer development and stroke prognosis, namely, angiogenesis. This review will discuss recent advancements in the EV-facilitated/inhibited progression of specific elements of angiogenesis with a particular concern about ncRNAs within these vesicles. The review is concluded by underlining the clinical opportunities of EV-derived ncRNAs as diagnostic, prognostic, and therapeutic agents.

Comprehensive evaluation of surrogate endpoints to predict overall survival in trials with PD1/PD-L1 immune checkpoint inhibitors plus chemotherapy

BACKGROUND

PD1/PD-L1 immune checkpoint inhibitors (ICI) have revolutionized cancer treatment. Although there is controversy about the accuracy of surrogate endpoints in the ICI setting to predict overall survival (OS), these endpoints are commonly used in confirmatory trials. Here we aimed to explore the validity of classical and novel surrogate endpoints in randomised controlled trials (RCT) that combine ICI plus chemotherapy (CT) in the first-line setting.

MATERIAL AND METHODS

A systematic review was conducted to identify RCT investigating anti-PD1/PD-L1 drugs plus CT versus CT alone. We performed (i) arm-level analysis to evaluate predictors of median OS (mOS) and (ii) comparison-level analysis for OS hazard ratio (HR) estimations. Linear regression models weighted by trial size were fitted and adjusted R² values were reported.

RESULTS

Thirty-nine RCTs involving 22,341 patients met the inclusion criteria (17 non-small cell lung, 9 gastroesophageal and 13 in other cancers) with ten different ICI under study. Overall, ICI plus CT improved OS (HR = 0.76; 95%CI: 0.73-0.80). In the arm-level analysis, the best mOS prediction was obtained with a new endpoint that combines median duration of response and ORR (mDoR-ORR) and with median PFS (R² = 0.5 both). In the comparison-level analysis, PFS HR showed a moderate association with OS HR (R² = 0.52). Early OS read-outs were highly associated with final OS outcomes (R² = 0.80).

CONCLUSIONS

The association between surrogate endpoints and OS in first-line RCT combining anti-PD1/PD-L1 and CT is moderate-low. Early OS read-outs showed a good association with final OS HR while the mDOR-ORR endpoint could help to better design confirmatory trials after single-arm phase II trials.

Research progress of abnormal lactate metabolism and lactate modification in immunotherapy of hepatocellular carcinoma

Tumors meet their energy, biosynthesis, and redox demands through metabolic reprogramming. This metabolic abnormality results in elevated levels of metabolites, particularly lactate, in the tumor microenvironment. Immune cell reprogramming and cellular plasticity mediated by lactate and lactylation increase immunosuppression in the tumor microenvironment and are emerging as key factors in regulating tumor development, metastasis, and the effectiveness of immunotherapies such as immune checkpoint inhibitors. Reprogramming of glucose metabolism and the "Warburg effect" in hepatocellular carcinoma (HCC) lead to the massive production and accumulation of lactate, so lactate modification in tumor tissue is likely to be abnormal as well. This article reviews the immune regulation of abnormal lactate metabolism and lactate modification in hepatocellular carcinoma and the therapeutic strategy of targeting lactate-immunotherapy, which will help to better guide the medication and treatment of patients with hepatocellular carcinoma.

Research progress of therapeutic effects and drug resistance of immunotherapy based on PD-1/PD-L1 blockade

The binding of programmed death-1 (PD-1) on the surface of T cells and PD-1 ligand 1 (PD-L1) on tumor cells can prevent the immune-killing effect of T cells on tumor cells and promote the immune escape of tumor cells. Therefore, immune checkpoint blockade targeting PD-1/PD-L1 is a reliable tumor therapy with remarkable efficacy. However, the main challenges of this therapy are low response rate and acquired resistance, so that the outcomes of this therapy are usually unsatisfactory. This review begins with the description of biological structure of the PD-1/PD-L1 immune checkpoint and its role in a variety of cells. Subsequently, the therapeutic effects of immune checkpoint blockers (PD-1 / PD-L1 inhibitors) in various tumors were introduced and analyzed, and the reasons affecting the function of PD-1/PD-L1 were systematically analyzed. Then, we focused on analyzing, sorting out and introducing the possible underlying mechanisms of primary and acquired resistance to PD-1/PD-L1 blockade including abnormal expression of PD-1/PD-L1 and some factors, immune-related pathways, tumor immune microenvironment, and T cell dysfunction and others. Finally, promising therapeutic strategies to sensitize the resistant patients with PD-1/PD-L1 blockade treatment were described. This review is aimed at providing guidance for the treatment of various tumors, and highlighting the drug resistance mechanisms to offer directions for future tumor treatment and improvement of patient prognosis.