Anti-PD-L1/TGFβR2 (M7824) fusion protein induces immunogenic modulation of human urothelial carcinoma cell lines, rendering them more susceptible to immune-mediated recognition and lysis

The TGFβ type I receptor kinase inhibitor vactosertib in combination with pomalidomide in relapsed/refractory multiple myeloma: a phase 1b trial

Functional blockade of the transforming growth factor-beta (TGFβ) signalling pathway improves the efficacy of cytotoxic and immunotherapies. Here, we conducted a phase 1b study (ClinicalTrials.gov., NCT03143985) to determine the primary endpoints of safety, tolerability, and maximal tolerated dose (200 mg twice daily) for the orally-available TGFβ type I receptor kinase inhibitor vactosertib in combination with pomalidomide in relapsed and/or refractory multiple myeloma (RRMM) patients who had received ≥2 lines of chemoimmunotherapy. Secondary endpoints demonstrated sustained clinical responses, favorable pharmacokinetic parameters and a 6-month progression-free survival of 82%. Vactosertib combined with pomalidomide was well-tolerated at all dose levels and displayed a manageable adverse event profile. Exploratory analysis indicated that vactosertib co-treatment with pomalidomide also reduced TGFβ levels in patient bone marrow as well as the level of CD8+ T-cells that expressed the immunoinhibitory marker PD-1. In vitro experiments indicated that vactosertib+pomalidomide co-treatment decreased the viability of MM cell lines and patient tumor cells, and increased CD8+ T-cell cytotoxic activity. Vactosertib is a safe therapeutic that demonstrates tumor-intrinsic activity and can overcome immunosuppressive challenges within the tumor microenvironment to reinvigorate T-cell fitness. Vactosertib offers promise to improve immunotherapeutic responses in heavily-pretreated MM patients refractory to conventional agents.

Recent developments in immunotherapy for gastrointestinal tract cancers

The past few decades have witnessed the rise of immunotherapy for Gastrointestinal (GI) tract cancers. The role of immune checkpoint inhibitors (ICIs), particularly programmed death protein 1 (PD-1) and PD ligand-1 antibodies, has become increasingly pivotal in the treatment of advanced and perioperative GI tract cancers. Currently, anti-PD-1 plus chemotherapy is considered as first-line regimen for unselected advanced gastric/gastroesophageal junction adenocarcinoma (G/GEJC), mismatch repair deficient (dMMR)/microsatellite instability-high (MSI-H) colorectal cancer (CRC), and advanced esophageal cancer (EC). In addition, the encouraging performance of claudin18.2-redirected chimeric antigen receptor T-cell (CAR-T) therapy in later-line GI tract cancers brings new hope for cell therapy in solid tumour treatment. Nevertheless, immunotherapy for GI tumour remains yet precise, and researchers are dedicated to further maximising and optimising the efficacy. This review summarises the important research, latest progress, and future directions of immunotherapy for GI tract cancers including EC, G/GEJC, and CRC.

Epithelial-to-mesenchymal transition in cancer progression: unraveling the immunosuppressive module driving therapy resistance

Cancer cells undergo phenotypic switching (cancer cell plasticity) in response to microenvironmental cues, including exposure to therapy/treatment. Phenotypic plasticity enables the cancer cells to acquire more mesenchymal traits promoting cancer cells' growth, survival, therapy resistance, and disease recurrence. A significant program in cancer cell plasticity is epithelial-to-mesenchymal transition (EMT), wherein a comprehensive reprogramming of gene expression occurs to facilitate the translational shift from epithelial-to-mesenchymal phenotypes resulting in increased invasiveness and metastasis. In addition, EMT plays a pivotal role in facilitating cancer cells' escape from the body's immune system using several mechanisms, such as the downregulation of major histocompatibility complex-mediated antigen presentation, upregulation of immune checkpoint molecules, and recruitment of immune-suppressive cells. Cancer cells' ability to undergo phenotypic switching and EMT-driven immune escape presents a formidable obstacle in cancer management, highlighting the need to unravel the intricate mechanisms underlying these processes and develop novel therapeutic strategies. This article discusses the role of EMT in promoting immune evasion and therapy resistance. We also discuss the ongoing research on developing therapeutic approaches targeting intrinsic and induced cell plasticity within the immune suppressive microenvironment. We believe this review article will update the current research status and equip researchers, clinicians, and other healthcare professionals with valuable insights enhancing their existing knowledge and shedding light on promising directions for future cancer research. This will facilitate the development of innovative strategies for managing therapy-resistant cancers and improving patient outcomes.

Dominant negative TGFβ receptor II and truncated TIM3 enhance the antitumor efficacy of CAR-T-cell therapy in prostate cancer

BACKGROUND

The immune checkpoint molecules, Transforming growth factor beta receptor II (TGFβRII) and T cell immunoglobulin and mucin domain 3 (TIM3), have been identified as contributors to T cell immune suppression in prostate cancer. The objective of this investigation was to improve the tumor killing capability of prostate-specific membrane antigen (PSMA)-chimeric antigen receptor T (CAR-T) cells by targeting TIM3 and TGFβRII simultaneously.

METHODS

To generate dnTGFβRII-trTIM3-PSMA-CAR-T (DT-PSMA-CAR-T) cells, the surface of PSMA-CAR-T cells was overexpressed with dominant negative TGFβRII (dnTGFβRII) and truncated extracellular TIM3 (trTIM3). The efficacy of DT-PSMA-CAR-T cells was assessed through in vitro killing experiments and animal experiments.

RESULTS

The DT-PSMA-CAR-T cells demonstrated the ability to eradicate PSMA-positive prostate cancer cells, even in the presence of exogenous TGF-β and/or TIM3 activating antibodies. In addition, the cells demonstrated the ability to eliminate tumor tissue in an immunodeficient mouse model transplanted with GAL9-PSMA-PC3 cells in vitro, prolonging survival without significant toxic side effects.

CONCLUSIONS

This study emphasizes that upregulating dnTGFβRII and trTIM3 on the surface of T cells can potentially diminish the inhibitory effects of TGFβRII and TIM3.

Dual anti-PD-(L)1/TGF-β inhibitors in cancer immunotherapy - Updated

Immune checkpoint inhibitor (ICI) therapy suffers from tumor resistance and relapse in majority of patients due to the suppressive tumor immune microenvironment (TIME). Advances in the field have brought about development of fusion proteins able to target two signaling simultaneously and to exert maximal anti-cancer immunity. Bispecific inhibitors of transforming growth factor (TGF)-β signaling and programmed death-1 (PD-1) or programmed death-ligand 1 (PD-L1) are developed to reduce the rate of relapse and to achieve durable anti-cancer therapy. TGF-β is well-known for its immunosuppressive activity, and it takes critical roles in promotion of all tumor hallmarks. Bispecific anti-PD-(L)1/TGF-β inhibitors reinvigorate effector activity of CD8+ T and natural killer (NK) cells, hamper regulatory T cell (Treg) expansion, and increase the density of anti-tumor type 1 macrophages (M1). Responses to the bispecific approach are higher compared with solo anti-PD-(L)1 or TGF-β targeted therapy, and are seemingly more pronounced in human papillomavirus (HPV)+ patients. High expression of PD-L1 or immune-excluded phenotype in a tumor can also be markers of better response to the bispecific strategy. Besides, anti-PD-(L)1/TGF-β inhibitor therapy can be used safely with other therapeutic modalities including vaccination, radiation and chemotherapy.

Mechanisms of CD8+ T cell exclusion and dysfunction in cancer resistance to anti-PD-(L)1

CD8⁺ T cells are the front-line defensive cells against cancer. Reduced infiltration and effector function of CD8⁺ T cells occurs in cancer and is contributed to defective immunity and immunotherapy resistance. Exclusion and exhaustion of CD8⁺ T cells are the two key factors associated with reduced durability of immune checkpoint inhibitor (ICI) therapy. Initially activated T cells upon exposure to chronic antigen stimulation or immunosuppressive tumor microenvironment (TME) acquire a hyporesponsive state that progressively lose their effector function. Thus, a key strategy in cancer immunotherapy is to look for factors contributed to defective CD8⁺ T cell infiltration and function. Targeting such factors can define a promising supplementary approach in patients receiving anti-programmed death-1 receptor (PD-1)/anti-programmed death-ligand 1 (PD-L1) therapy. Recently, bispecific antibodies are developed against PD-(L)1 and a dominant factor within TME, representing higher safety profile and exerting more desired outcomes. The focus of this review is to discuss about promoters of deficient infiltration and effector function of CD8⁺ T cells and their addressing in cancer ICI therapy.

Cancer-associated Fibroblasts in Bladder Cancer: Origin, Biology, and Therapeutic Opportunities

CONTEXT

Bladder cancer (BLCA) is a highly prevalent tumour and a health problem worldwide, especially among men. Recent work has highlighted the relevance of the tumour microenvironment (TME) in cancer biology with translational implications. Cancer-associated fibroblasts (CAFs) are a prominent, heterogeneous population of cells in the TME. CAFs have been associated with tumour development, progression, and poor prognosis in several neoplasms. However, their role in BLCA has not yet been exploited deeply.

OBJECTIVE

To review the role of CAFs in BLCA biology and provide an understanding of CAF origin, subtypes, markers, and phenotypic and functional characteristics to improve patient management.

EVIDENCE ACQUISITION

A PubMed search was performed to review manuscripts published using the terms "cancer associated fibroblast" and "bladder cancer" or "urothelial cancer". All abstracts were reviewed, and the full content of all relevant manuscripts was analysed. In addition, selected manuscripts on CAFs in other tumours were considered.

EVIDENCE SYNTHESIS

CAFs have been studied less extensively in BLCA than in other tumours. Thanks to new techniques, such as single-cell RNA-seq and spatial transcriptomics, it is now possible to accurately map and molecularly define the phenotype of fibroblasts in normal bladder and BLCA. Bulk transcriptomic analyses have revealed the existence of subtypes among both non-muscle-invasive and muscle-invasive BLCA; these subtypes display distinct features regarding their CAF content. We provide a higher-resolution map of the phenotypic diversity of CAFs in these tumour subtypes. Preclinical studies and recent promising clinical trials leverage on this knowledge through the combined targeting of CAFs or their effectors and the immune microenvironment.

CONCLUSIONS

Current knowledge of BLCA CAFs and the TME is being increasingly applied to improve BLCA therapy. There is a need to acquire a deeper understanding of CAF biology in BLCA.

PATIENT SUMMARY

Tumour cells are surrounded by nontumoural cells that contribute to the determination of the behaviour of cancers. Among them are cancer-associated fibroblasts. The "neighbourhoods" established through these cellular interactions can now be studied with much greater resolution. Understanding these features of tumours will contribute to the designing of more effective therapies, especially in relationship to bladder cancer immunotherapy.

Macrophage activity at the site of tumor ablation can promote murine urothelial cancer via transforming growth factor-β1

Cell death and injury at the site of tumor ablation attracts macrophages. We sought to understand the status and activity of these cells while focusing on transforming growth factor-β1 (TGF-β1), a potent immunosuppressive and tumorigenic cytokine. Patients with urothelial cancer who underwent ablation using electrocautery or laser demonstrated increased infiltration and numbers of CD8+ T cells, along with FoxP3+ regulatory T cells, CD68+ macrophages and elevated levels of TGF-β1 in recurrent tumors. Similar findings were reproduced in a mouse model of urothelial cancer (MB49) by partial tumor ablation with irreversible electroporation (IRE). Stimulation of bone marrow derived macrophages with MB49 cell debris produced using IRE elicited strong M2 polarization, with exuberant secretion of TGF-β1. The motility, phenotypic markers and cytokine secretion by macrophages could be muted by treatment with Pirfenidone (PFD), a clinically approved drug targeting TGF-β1 signaling. MB49 cancer cells exposed to TGF-β1 exhibited increased migration, invasiveness and upregulation of epithelial-mesenchymal transition markers α-Smooth Muscle Actin and Vimentin. Such changes in MB49 cells were reduced by treatment with PFD even during stimulation with TGF-β1. IRE alone yielded better local tumor control when compared with control or PFD alone, while also reducing the overall number of lung metastases. Adjuvant PFD treatment did not provide additional benefit under in vivo conditions.

The roles of TGF-β and VEGF pathways in the suppression of antitumor immunity in melanoma and other solid tumors

Immune checkpoint blockade (ICB) has become well-known in cancer therapy, strengthening the body's antitumor immune response rather than directly targeting cancer cells. Therapies targeting immune inhibitory checkpoints, such as PD-1, PD-L1, and CTLA-4, have resulted in impressive clinical responses across different types of solid tumors. However, as with other types of cancer treatments, ICB-based immunotherapy is hampered by both innate and acquired drug resistance. We previously reported the enrichment of gene signatures associated with wound healing, epithelial-to-mesenchymal, and angiogenesis processes in the tumors of patients with innate resistance to PD-1 checkpoint antibody therapy; we termed these the Innate Anti-PD-1 Resistance Signatures (IPRES). The TGF-β and VEGFA pathways emerge as the dominant drivers of IPRES-associated processes. Here, we review these pathways' functions, their roles in immunosuppression, and the currently available therapies that target them. We also discuss recent developments in the targeting of TGF-β using a specific antibody class termed trap antibody. The application of trap antibodies opens the promise of localized targeting of the TGF-β and VEGFA pathways within the tumor microenvironment. Such specificity may offer an enhanced therapeutic window that enables suppression of the IPRES processes in the tumor microenvironment while sparing the normal homeostatic functions of TGF-β and VEGFA in healthy tissues.

The difficulty in translating the preclinical success of combined TGFβ and immune checkpoint inhibition to clinical trial

Immune checkpoint inhibitors (ICIs) have transformed the treatment paradigm for solid tumors. However, even in cancers generally considered ICI-sensitive, responses can vary significantly. Thus, there is an ever-increasing interest in identifying novel means of improving therapeutic responses, both for cancers in which ICIs are indicated and those for which they have yet to show significant anti-tumor activity. To this end, Transforming Growth Factor β (TGFβ) signaling is emerging as an important barrier to the efficacy of ICIs. Accordingly, several preclinical studies now support the use of combined TGFβ and immune checkpoint blockade, with near-uniform positive results across a wide range of tumor types. However, as these approaches have started to emerge in clinical trials, the addition of TGFβ inhibitors has often failed to show a meaningful benefit beyond the current generation of ICIs alone. Here, we summarize landmark clinical studies exploring combined TGFβ and immune checkpoint blockade. These studies not only reinforce the difficulty in translating results from rodents to clinical trials in immune-oncology but also underscore the need to re-evaluate the design of trials exploring this approach, incorporating both mechanism-driven combination strategies and novel, predictive biomarkers to identify the patients most likely to derive clinical benefit.

ALT-803 in the treatment of non-muscle-invasive bladder cancer: Preclinical and clinical evidence and translational potential

Bladder cancer (BCa) is one of the most common malignant tumors that cause death. Approximately 75%–85% of BCa develop into non-muscle-invasive bladder cancer (NMIBC). Bacillus Calmette-Guérin (BCG) is the gold standard for avoiding cystectomy in the treatment of NMIBC. Unfortunately, up to 30% of patients do not respond to BCG treatment, and up to 70% of BCG responders relapse. The United States Food and Drug Administration (FDA) approved valrubicin (1998) and pembrolizumab (2020) for the treatment of BCG-unresponsive (BCGu) NMBIC. However, the complete remission rate for valrubicin and pembrolizumab was only 16% and 40.6%, respectively. ALT-803 (N-803) is an IL-15 superagonist and reduces tumor burden by promoting the proliferation and activation of NK cells and CD8⁺ T cells. The FDA received (23 May 2022) and accepted to review (28 July 2022) the marketing submission of ALT-803 plus BCG for the treatment of BCGu NMIBC. However, the FDA previously rejected the application for oportuzumab monatox (OM) due to a lack of data comparing it with pembrolizumab on August 20, 2021. Interestingly, the clinical efficacy and safety of ALT-803 were higher than that of pembrolizumab and OM, suggesting that ALT-803 may be approved by FDA. This review aims to further knowledge of the preclinical and clinical evidence of ALT-803 in the treatment of NMIBC and discuss its translational potential.

Next-generation immunotherapy for solid tumors: combination immunotherapy with crosstalk blockade of TGFβ and PD-1/PD-L1

INTRODUCTION

In solid tumor immunotherapy, less than 20% of patients respond to anti-programmed cell death 1 (PD-1)/programmed cell death 1 ligand 1 (PD-L1) agents. The role of transforming growth factor β (TGFβ) in diverse immunity is well-established; however, systemic blockade of TGFβ is associated with toxicity. Accumulating evidence suggests the role of crosstalk between TGFβ and PD-1/PD-L1 pathways.

AREAS COVERED

We focus on TGFβ and PD-1/PD-L1 signaling pathway crosstalk and the determinant role of TGFβ in the resistance of immune checkpoint blockade. We provide the rationale for combination anti-TGFβ and anti-PD-1/PD-L1 therapies for solid tumors and discuss the current status of dual blockade therapy in preclinical and clinical studies.

EXPERT OPINION

The heterogeneity of tumor microenvironment across solid tumors complicates patient selection, treatment regimens, and response and toxicity assessment for investigation of dual blockade agents. However, clinical knowledge from single-agent studies provides infrastructure to translate dual blockade therapies. Dual TGFβ and PD-1/PD-L1 blockade results in enhanced T-cell infiltration into tumors, a primary requisite for successful immunotherapy. A bifunctional fusion protein specifically targets TGFβ in the tumor microenvironment, avoiding systemic toxicity, and prevents interaction of PD-1+ cytotoxic cells with PD-L1+ tumor cells.

Tipping the scales: Immunotherapeutic strategies that disrupt immunosuppression and promote immune activation

Immunotherapy has emerged as an effective therapeutic approach for several cancer types. However, only a subset of patients exhibits a durable response due in part to immunosuppressive mechanisms that allow tumor cells to evade destruction by immune cells. One of the hallmarks of immune suppression is the paucity of tumor-infiltrating lymphocytes (TILs), characterized by low numbers of effector CD4+ and CD8+ T cells in the tumor microenvironment (TME). Additionally, the proper activation and function of lymphocytes that successfully infiltrate the tumor are hampered by the lack of co-stimulatory molecules and the increase in inhibitory factors. These contribute to the imbalance of effector functions by natural killer (NK) and T cells and the immunosuppressive functions by myeloid-derived suppressor cells (MDSCs) and regulatory T cells (Tregs) in the TME, resulting in a dysfunctional anti-tumor immune response. Therefore, therapeutic regimens that elicit immune responses and reverse immune dysfunction are required to counter immune suppression in the TME and allow for the re-establishment of proper immune surveillance. Immuno-oncology (IO) agents, such as immune checkpoint blockade and TGF-β trapping molecules, have been developed to decrease or block suppressive factors to enable the activity of effector cells in the TME. Therapeutic agents that target immunosuppressive cells, either by direct lysis or altering their functions, have also been demonstrated to decrease the barrier to effective immune response. Other therapies, such as tumor antigen-specific vaccines and immunocytokines, have been shown to activate and improve the recruitment of CD4+ and CD8+ T cells to the tumor, resulting in improved T effector to Treg ratio. The preclinical data on these diverse IO agents have led to the development of ongoing phase I and II clinical trials. This review aims to provide an overview of select therapeutic strategies that tip the balance from immunosuppression to immune activity in the TME.

Preclinical and clinical studies of bintrafusp alfa, a novel bifunctional anti-PD-L1/TGFβRII agent: Current status

Bintrafusp alfa (anti-PD-L1/TGFβRII) is a first-in-class bifunctional agent designed to act both as a checkpoint inhibitor and as a "trap" for TGFβ in the tumor microenvironment (TME). This article is designed to review the preclinical studies interrogating the mode of action of bintrafusp alfa and to present a comprehensive overview of recent bintrafusp alfa clinical studies. Preclinical studies have demonstrated that bintrafusp alfa immune-mediating and antitumor activity can be enhanced by combining it with a human papillomavirus (HPV) therapeutic cancer vaccine, a tumor-targeting interleukin 12 (IL-12) immunocytokine and/or an IL-15 superagonist. The importance of TGFβ in HPV-associated malignancies is also reviewed. The clinical studies reviewed span extended phase I cohorts in patients with a spectrum of malignancies, two randomized phase II studies in lung and one in biliary tract cancers in which bintrafusp alfa did not demonstrate superiority over standard-of-care therapies, and provocative results in patients with HPV-associated malignancies, where as a monotherapy, bintrafusp alfa has shown response rates of 35%, compared to overall response rate (ORR) of 12-24% seen with other Food and Drug Administration (FDA)-approved or standard-of-care agents. This article also reviews preliminary phase II study results of patients with HPV+ malignancies employing bintrafusp alfa in combination with an HPV therapeutic vaccine and a tumor-targeting IL-12 immunocytokine in which the combination therapy outperforms standard-of-care therapies in both checkpoint naïve and checkpoint refractory patients. This review thus provides an example of the importance of conducting clinical studies in an appropriate patient population - in this case, exemplified by the role of TGFβ in HPV-associated malignancies. This review also provides preclinical and preliminary clinical study results of the combined use of multiple immune-modulating agents, each designed to engage different immune components and tumor cells in the TME.

Narrative Review of Synergistics Effects of Combining Immunotherapy and Stereotactic Radiation Therapy

Stereotactic radiotherapy (SRT) has become an attractive treatment modality in full bloom in recent years by presenting itself as a safe, noninvasive alternative to surgery to control primary or secondary malignancies. Although the focus has been on local tumor control as the therapeutic goal of stereotactic radiotherapy, rare but intriguing observations of abscopal (or out-of-field) effects have highlighted the exciting possibility of activating antitumor immunity using high-dose radiation. Furthermore, immunotherapy has revolutionized the treatment of several types of cancers in recent years. However, resistance to immunotherapy often develops. These observations have led researchers to combine immunotherapy with SRT in an attempt to improve outcomes. The benefits of this combination would come from the stimulation and suppression of various immune pathways. Thus, in this review, we will first discuss the immunomodulation induced by SRT with the promising results of preclinical studies on the changes in the immune balance observed after SRT. Then, we will discuss the opportunities and risks of the combination of SRT and immunotherapy with the preclinical and clinical data available in the literature. Furthermore, we will see that many perspectives are conceivable to potentiate the synergistic effects of this combination with the need for prospective studies to confirm the encouraging data.

Immune correlates of clinical parameters in patients with HPV-associated malignancies treated with bintrafusp alfa

Purpose

Bintrafusp alfa is a bifunctional agent consisting of an anti-human PD-L1 antibody linked to two TGFβRII. It is designed to act both as a checkpoint inhibitor and to ‘trap’ TGFβ in the tumor microenvironment. Phase I and II clinical studies demonstrated clinical activity in patients with a range of human papillomavirus (HPV)-associated cancers. The purpose of the studies reported here was the interrogation of various aspects of the peripheral immunome in patients with HPV-associated cancers, both prior to and early in the treatment regimen of bintrafusp alfa to better understand the mode of action of the agent and to help define which patients are more likely to benefit from bintrafusp alfa treatment.

Patients and methods

The peripheral immunome of patients (n=65) with HPV⁺ malignancies was analyzed both prior to treatment with bintrafusp alfa and day 14 post-treatment for levels and changes in (1) 158 different immune cell subsets, (2) multiple plasma soluble factors including analytes reflecting immune stimulatory and inhibitory status, (3) complete blood counts, and in a subset of patients (4) TCR diversity and (5) HPV-specific T-cell responses.

Results

Interrogation of the peripheral immunome prior to bintrafusp alfa treatment revealed several factors that associated with clinical response, including (1) higher levels of sCD27:sCD40L ratios, (2) lower levels of TGFβ1 and 12 additional factors associated with tumor mesenchymalization, and (3) higher CD8⁺ T cell:MDSC ratios. Analysis at 2 weeks post bintrafusp alfa revealed that eventual clinical responders had fewer increases in IL-8 levels and the neutrophil to lymphocyte ratio, and higher levels of HPV-16 specific CD8⁺ T cells. This study also provided information concerning differences in the peripheral immunome for patients who were naïve versus refractory to prior checkpoint inhibition therapy. While preliminary, two multivariate models developed predicted clinical benefit with 76%–91% accuracy.

Conclusions

These studies add insight into the mechanism of action of bintrafusp alfa and provide evidence that the interrogation of both cellular and soluble components of the peripheral immunome of patients with HPV-associated malignancies, either prior to or early in the therapeutic regimen, can provide information as to which patients are more likely to benefit with bintrafusp alfa therapy.

Resistance to Immunotherapy: Mechanisms and Means for Overcoming

Immune checkpoint blockade transformed cancer therapy during the last decade. However, durable responses remain uncommon, early and late relapses occur over the course of treatment, and many patients with PD-L1-expressing tumors do not respond to PD-(L)1 blockade. In addition, while some malignancies exhibit inherent resistance to treatment, others develop adaptations that allow them to evade antitumor immunity after a period of response. It is crucial to understand the pathophysiology of the tumor-immune system interplay and the mechanisms of immune escape in order to circumvent primary and acquired resistance. Here we provide an outline of the most well-defined mechanisms of resistance and shed light on ongoing efforts to reinvigorate immunoreactivity.

Dual targeting of TGF-β and PD-L1 via a bifunctional anti-PD-L1/TGF-βRII agent: status of preclinical and clinical advances

Immunosuppressive entities in the tumor microenvironment (TME) remain a major impediment to immunotherapeutic approaches for a majority of patients with cancer. While the immunosuppressive role of transforming growth factor-β (TGF-β) in the TME is well known, clinical studies to date with anti-TGF-β agents have led to limited success. The bifunctional agent bintrafusp alfa (previously designated M7824) has been developed in an attempt to address this issue. Bintrafusp alfa consists of an IgG₁ targeting programmed death ligand 1 (PD-L1) moiety fused via peptide linkers to the extracellular domain of two TGF-β receptor II molecules designed to ‘trap’ TGF-β in the TME. This agent is able to bring the TGF-β trap to the TME via its anti-PD-L1 component, thus simultaneously attacking both the immunosuppressive PD-L1 and TGF-β entities. A number of preclinical studies have shown bintrafusp alfa capable of (1) preventing or reverting TGF-β-induced epithelial-mesenchymal transition in human carcinoma cells; this alteration in tumor cell plasticity was shown to render human tumor cells more susceptible to immune-mediated attack as well as to several chemotherapeutic agents; (2) altering the phenotype of natural killer and T cells, thus enhancing their cytolytic ability against tumor cells; (3) mediating enhanced lysis of human tumor cells via the antibody-dependent cell-mediated cytotoxicity mechanism; (4) reducing the suppressive activity of T_reg cells; (5) mediating antitumor activity in numerous preclinical models and (6) enhancing antitumor activity in combination with radiation, chemotherapy and several other immunotherapeutic agents. A phase I clinical trial demonstrated a safety profile similar to other programmed cell death protein 1 (PD-1)/PD-L1 checkpoint inhibitors, with objective and durable clinical responses. We summarize here preclinical and emerging clinical data in the use of this bispecific and potentially multifunctional agent.

β-

Background

Immunotherapy with chimeric antigen receptor (CAR)-engineered T-cells is effective in some hematologic tumors. In solid tumors, however, sustained antitumor responses after CAR T-cell therapy remain to be demonstrated both in the pre-clinical and clinical setting. A perceived barrier to the efficacy of CAR T-cell therapy in solid tumors is the hostile tumor microenvironment where immunosuppressive soluble factors like transforming growth factor (TGF)-β are thought to inhibit the cellular immune response. Here, we analyzed whether CAR T-cells specific for the receptor tyrosine kinase-like orphan receptor 1 (ROR1) antigen, that is frequently expressed in triple-negative breast cancer (TNBC), are susceptible to inhibition by TGF-β and evaluated TGF-β-receptor signaling blockade as a way of neutralizing the inhibitory effect of this cytokine.

Methods

CD8⁺ and CD4⁺ ROR1-CAR T-cells were prepared from healthy donors and their antitumor function analyzed using the TNBC cell line MDA-MB-231 in vitro and in a microphysiologic 3D tumor model. Analyses were performed in co-culture assays of ROR1-CAR T-cells and MDA-MB-231 cells with addition of exogenous TGF-β.

Results

The data show that exposure to TGF-β engages TGF-β-receptor signaling in CD8⁺ and CD4⁺ ROR1-CAR T-cells as evidenced by phosphorylation of small mothers against decapentaplegic homolog 2. In the presence of TGF-β, the cytolytic activity, cytokine production and proliferation of ROR1-CAR T-cells in co-culture with MDA-MB-231 TNBC cells were markedly impaired, and the viability of ROR1-CAR T-cells reduced. Blockade of TGF-β-receptor signaling with the specific kinase inhibitor SD-208 was able to protect CD8⁺ and CD4⁺ ROR1-CAR T-cells from the inhibitory effect of TGF-β, and sustained their antitumor function in vitro and in the microphysiologic 3D tumor model. Combination treatment with SD-208 also led to increased viability and lower expression of PD-1 on ROR1-CAR T-cells at the end of the antitumor response.

Conclusion

We demonstrate the TGF-β suppresses the antitumor function of ROR1-CAR T-cells against TNBC in preclinical models. Our study supports the continued preclinical development and the clinical evaluation of combination treatments that shield CAR T-cells from TGF-β, as exemplified by the TGF-β-receptor kinase inhibitor SD-208 in this study.

Immunology of Lynch Syndrome

PURPOSE OF REVIEW

Patients with Lynch syndrome have a high probability of developing colorectal and other carcinomas. This review provides a comprehensive assessment of the immunologic aspects of Lynch syndrome pathogenesis and provides an overview of potential immune interventions for patients with Lynch syndrome polyps and Lynch syndrome-associated carcinomas.

RECENT FINDINGS

Immunogenic properties of the majority of Lynch syndrome polyps and associated cancers include microsatellite instability leading to a high mutational burden and the development of novel frameshift peptides, i.e., neoantigens. In addition, patients with Lynch syndrome develop T cell responses in the periphery and in the tumor microenvironment (TME) to tumor-associated antigens, and a proinflammatory cytokine TME has also been identified. However, Lynch syndrome lesions also possess immunosuppressive entities such as alterations in MHC class I antigen presentation, TGFβ receptor mutations, regulatory T cells, and upregulation of PD-L1 on tumor-associated lymphocytes. The rich immune microenvironment of Lynch syndrome polyps and associated carcinomas provides an opportunity to employ the spectrum of immune-mediating agents now available to induce and enhance host immune responses and/or to also reduce immunosuppressive entities. These agents can be employed in the so-called prevention trials for the treatment of patients with Lynch syndrome polyps and for trials in patients with Lynch syndrome-associated cancers.

Analysis of the tumor microenvironment and anti-tumor efficacy of subcutaneous vs systemic delivery of the bifunctional agent bintrafusp alfa

Most monoclonal antibodies (MAbs), including immune checkpoint inhibitor MAbs, are delivered intravenously (i.v.) to patients. Recent clinical studies have demonstrated that some anti-PD1 MAbs may also be delivered subcutaneously (s.c.), with clinical outcomes similar of those obtained with i.v.-delivered agents. Bintrafusp alfa, a first-in-class bifunctional fusion protein composed of the extracellular domain of the human transforming growth factor β receptor II (TGF-βRII or TGF-β “trap”) fused to the heavy chain of an IgG1 antibody blocking programmed death ligand 1 (anti-PDL1), was designed to target two key immunosuppressive pathways in the tumor microenvironment (TME). Bintrafusp alfa is currently being administered i.v. in clinical studies. The studies reported here demonstrate that systemic or s.c. delivery of bintrafusp alfa, each administered at five different doses, induces similar anti-tumor effects in breast and colorectal carcinoma models. An interrogation of the TME for CD8⁺ and CD4⁺ T cells, regulatory T cells (Tregs), monocytic myeloid-derived suppressor cells (M-MDSCs) and granulocytic (G) MDSCs showed similar levels and phenotype of each cell subset when bintrafusp alfa was given systemically or s.c. Subcutaneous administration of bintrafusp alfa also sequestered TGFβ in the periphery at similar levels seen with systemic delivery. To our knowledge, this is the most comprehensive preclinical evaluation of any checkpoint inhibitor MAb given s.c. vs systemically, and the first to demonstrate this phenomenon using a bifunctional agent. These studies provide preclinical rationale to explore s.c. approaches for bintrafusp alfa in the clinic.

T Cell Exhaustion and CAR-T Immunotherapy in Hematological Malignancies

T cell exhaustion has been recognized to play an immunosuppressive role in malignant diseases. Persistent tumor antigen stimulation, the presence of inhibitory immune cells and cytokines in tumor microenvironment (TME), upregulated expression of inhibitory receptors, changes in T cell-related transcription factors, and metabolic factors can all result in T cell exhaustion. Strategies dedicated to preventing or reversing T cell exhaustion are required to reduce the morbidity from cancer and enhance the effectiveness of adoptive cellular immunotherapy. Here, we summarize the current findings of T cell exhaustion in hematological malignancies and chimeric antigen receptor T (CAR-T) immunotherapy, as well as the value of novel technologies, to inverse such dysfunction. Our emerging understanding of T cell exhaustion may be utilized to develop personalized strategies to restore antitumor immunity.

Recent Advances in the Development of TGF-β Signaling Inhibitors for Anticancer Therapy

TGF-β is a multifunctional cytokine that plays an important role in both physiologic and pathologic processes, including cancer. Importantly, TGF-β has a dual role in tumorigenesis, acting as a tumor suppressor or a tumor promoter, depending on the stage of tumor development. The aberrantly upregulated production of TGF-β has been strongly implicated in tumor progression, angiogenesis, and metastasis, as well as immune evasion. Therefore, hyperactivated TGF-β signaling is considered a potential therapeutic target for cancer therapy. Numerous inhibitors of overactivated TGF-β signaling have been developed, and some of them are currently in clinical trials. This review focuses on the TGF-β signaling that contributes to tumor progression and immune evasion in the tumor microenvironment and presents recent achievements on TGF-β signaling inhibition as a single or combined therapeutic approach in cancer therapy.

On-Target Anti-TGF-β Therapies Are Not Succeeding in Clinical Cancer Treatments: What Are Remaining Challenges?

Metastasis is the leading cause of death for cancer patients. During cancer progression, the initial detachment of cells from the primary tumor and the later colonization of a secondary organ are characterized as limiting steps for metastasis. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are opposite dynamic multistep processes that enable these critical events in metastasis by altering the phenotype of cancer cells and improving their ability to migrate, invade and seed at distant organs. Among the molecular pathways that promote tumorigenesis in late-stage cancers, transforming growth factor-β (TGF-β) is described as an EMT master inducer by controlling different genes and proteins related to cytoskeleton assembly, cell-cell attachment and extracellular matrix remodeling. Still, despite the successful outcomes of different TGF-β pharmacological inhibitors in cell culture (in vitro) and animal models (in vivo), results in cancer clinical trials are poor or inconsistent at least, highlighting the existence of crucial components in human cancers that have not been properly explored. Here we review most recent findings to provide perspectives bridging the gap between on-target anti-TGF-β therapies in vitro and in pre-clinical models and the poor clinical outcomes in treating cancer patients. Specifically, we focus on (i) the dual roles of TGF-β signaling in cancer metastasis; (ii) dynamic signaling; (iii) functional differences of TGF-β free in solution vs. in exosomes; (iv) the regulatory effects of tumor microenvironment (TME) – particularly by cancer-associated fibroblasts – on TGF-β signaling pathway. Clearly identifying and establishing those missing links may provide strategies to revitalize and clinically improve the efficacy of TGF-β targeted therapies.

New directions in chimeric antigen receptor T cell [CAR-T] therapy and related flow cytometry

Chimeric antigen receptor (CAR) T cells provide a promising approach to the treatment of hematologic malignancies and solid tumors. Flow cytometry is a powerful analytical modality, which plays an expanding role in all stages of CAR T therapy, from lymphocyte collection, to CAR T cell manufacturing, to in vivo monitoring of the infused cells and evaluation of their function in the tumor environment. Therefore, a thorough understanding of the new directions is important for designing and implementing CAR T-related flow cytometry assays in the clinical and investigational settings. However, the speed of new discoveries and the multitude of clinical and preclinical trials make it challenging to keep up to date in this complex field. In this review, we summarize the current state of CAR T therapy, highlight the areas of emergent research, discuss applications of flow cytometry in modern cell therapy, and touch upon several considerations particular to CAR detection and assessing the effectiveness of CAR T therapy.

The Use of a Humanized NSG-β2m-/- Model for Investigation of Immune and Anti-tumor Effects Mediated by the Bifunctional Immunotherapeutic Bintrafusp Alfa

The lack of serial biopsies in patients with a range of carcinomas has been one obstacle in our understanding of the mechanism of action of immuno-oncology agents as well as the elucidation of mechanisms of resistance to these novel therapeutics. While much information can be obtained from studies conducted with syngeneic mouse models, these models have limitations, including that both tumor and immune cells being targeted are murine and that many of the immuno-oncology agents being evaluated are human proteins, and thus multiple administrations are hampered by host xenogeneic responses. Some of these limitations are being overcome by the use of humanized mouse models where human peripheral blood mononuclear cells (PBMC) are engrafted into immunosuppressed mouse strains. Bintrafusp alfa (M7824) is an innovative first-in-class bifunctional fusion protein composed of the extracellular domain of the TGF-βRII to function as a TGF-β "trap" fused to a human IgG1 antibody blocking PD-L1. A phase I clinical trial of bintrafusp alfa showed promising anti-tumor efficacy in heavily pretreated advanced solid tumors, and multiple clinical studies are currently ongoing. There is still much to learn regarding the mechanism of action of bintrafusp alfa, including its effects on both human immune cells in the periphery and in the tumor microenvironment (TME), and any temporal effects upon multiple administrations. By using the NSG-β2m-/- mouse strain humanized with PBMC, we demonstrate here for the first time: (a) the effects of bintrafusp alfa administration on human immune cells in the periphery vs. the TME using three different human xenograft models; (b) temporal effects upon multiple administrations of bintrafusp alfa; (c) phenotypic changes induced in the TME, and (d) variations observed in the use of multiple different PBMC donors. Also discussed are the similarities and differences in the data thus far obtained employing murine syngeneic models, from clinical trials, and in the use of this humanized mouse model. The results described here may guide the future use of this agent or similar immunotherapy agents as monotherapies or in combination therapy studies.

On-Target Anti-TGF-β Therapies Are Not Succeeding in Clinical Cancer Treatments: What Are Remaining Challenges?

Metastasis is the leading cause of death for cancer patients. During cancer progression, the initial detachment of cells from the primary tumor and the later colonization of a secondary organ are characterized as limiting steps for metastasis. Epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition (MET) are opposite dynamic multistep processes that enable these critical events in metastasis by altering the phenotype of cancer cells and improving their ability to migrate, invade and seed at distant organs. Among the molecular pathways that promote tumorigenesis in late-stage cancers, transforming growth factor-β (TGF-β) is described as an EMT master inducer by controlling different genes and proteins related to cytoskeleton assembly, cell-cell attachment and extracellular matrix remodeling. Still, despite the successful outcomes of different TGF-β pharmacological inhibitors in cell culture (in vitro) and animal models (in vivo), results in cancer clinical trials are poor or inconsistent at least, highlighting the existence of crucial components in human cancers that have not been properly explored. Here we review most recent findings to provide perspectives bridging the gap between on-target anti-TGF-β therapies in vitro and in pre-clinical models and the poor clinical outcomes in treating cancer patients. Specifically, we focus on (i) the dual roles of TGF-β signaling in cancer metastasis; (ii) dynamic signaling; (iii) functional differences of TGF-β free in solution vs. in exosomes; (iv) the regulatory effects of tumor microenvironment (TME) - particularly by cancer-associated fibroblasts - on TGF-β signaling pathway. Clearly identifying and establishing those missing links may provide strategies to revitalize and clinically improve the efficacy of TGF-β targeted therapies.

TGF-β and microRNA Interplay in Genitourinary Cancers

Genitourinary cancers (GCs) include a large group of different types of tumors localizing to the kidney, bladder, prostate, testis, and penis. Despite highly divergent molecular patterns, most GCs share commonly disturbed signaling pathways that involve the activity of TGF-β (transforming growth factor beta). TGF-β is a pleiotropic cytokine that regulates key cancer-related molecular and cellular processes, including proliferation, migration, invasion, apoptosis, and chemoresistance. The understanding of the mechanisms of TGF-β actions in cancer is hindered by the "TGF-β paradox" in which early stages of cancerogenic process are suppressed by TGF-β while advanced stages are stimulated by its activity. A growing body of evidence suggests that these paradoxical TGF-β actions could result from the interplay with microRNAs: Short, non-coding RNAs that regulate gene expression by binding to target transcripts and inducing mRNA degradation or inhibition of translation. Here, we discuss the current knowledge of TGF-β signaling in GCs. Importantly, TGF-β signaling and microRNA-mediated regulation of gene expression often act in complicated feedback circuits that involve other crucial regulators of cancer progression (e.g., androgen receptor). Furthermore, recently published in vitro and in vivo studies clearly indicate that the interplay between microRNAs and the TGF-β signaling pathway offers new potential treatment options for GC patients.

Communication between EMT and PD-L1 signaling: New insights into tumor immune evasion

Immune checkpoint blockage has been considered a breakthrough in cancer treatment, achieving encouraging anti-tumor effects in some advanced solid malignancies. However, low response rate and therapeutic resistance represent significant challenges in this field. In addition to its typical role in embryonic development and tissue fibrosis, epithelial-mesenchymal transition (EMT) plays a pivotal role in tumor immunosuppression and immune evasion. Previous studies revealed that EMT is associated with activation of different immune checkpoint molecules, including PD-L1. EMT-induced immune escape promotes cancer progression and may also provide a platform for discovery of novel therapeutic approaches and predictive biomarkers for checkpoint inhibitor therapeutic response. Here, we summarize recent findings focused on EMT-induced immune suppression and evasion in the tumor microenvironment (TME). EMT transcription factors (EMT-TFs), immune cells, cell plasticity and their regulatory role in the immune response are thoroughly reviewed. Bidirectional regulation between EMT and PD-L1 signaling is discussed in terms of cancer immune escape and possible combined therapies. Additionally, we investigated the value of preclinical or clinical trials using EMT targeted therapy combined with PD-L1 inhibitors. This review may help to further understand the role of EMT and PD-L1 signaling in cancer immune evasion. Meanwhile, additional molecular mechanistic studies and clinical trials are urgently needed.

Loss of Janus Associated Kinase 1 Alters Urothelial Cell Function and Facilitates the Development of Bladder Cancer

Inherited Primary Immunodeficiency (PID) disorders are associated with increased risk of malignancy that may relate to impaired antitumor immune responses or a direct role for PID germline mutations in tumorigenesis. We recently identified germline loss of function mutations in Janus Associated Kinase 1 (JAK1) causing primary immunodeficiency characterized by infections and associated with early onset, fatal high-grade bladder carcinoma. Somatic mutations in JAK1, required for immune cell signaling in response to interferon gamma (IFNγ), have been associated with several non-hematopoietic and hematopoietic cancer cell types but pathogenic mechanisms remain largely unexplored. Here we demonstrate that JAK1 is required for the intrinsic IFNγ response of urothelial cells impacting immunogenicity and cell survival. Specifically, JAK1-deficient urothelial cells showed reduced surface expression of major histocompatibility complex class II (MHC II), intercellular adhesion molecule-1 (ICAM-1) and programmed death-ligand-1 (PD-L1) after IFNγ stimulation and were resistant to IFNγ-induced apoptosis and lymphocyte-mediated killing. In addition, we identify a previously unknown role for IFNγ signaling in modulating urothelial differentiation. Together, our findings support a role for urothelial cell JAK1 in immune surveillance and development of bladder cancer. Our results have implications for patients with rare JAK1 PID and, more broadly, inform development of biomarker and targeted therapies for urothelial carcinoma.

The Yin and Yang of Cytoreductive SBRT in Oligometastases and Beyond

Background: Oligometastatic disease has emerged as a possibly distinct metastatic phenotype in numerous cancer histologies. With the advancement in treatment modalities including stereotactic body radiation therapy (SBRT), certain patients may derive benefits from local ablative therapy. SBRT alone has already shown to have potential benefits in certain oligometastatic disease types. However, more understanding of the immunologic modulation and microenvironment is needed to guide which patients may benefit from SBRT alone or with combination therapy, if at all. Purpose: The purpose of this review is to offer an update on the emerging data testing SBRT combined with immunotherapy, review the pro-inflammatory and immunosuppressive effects of the tumor microenvironment, discuss novel molecular targets used to augment the immune response, and review potential methods used to decrease toxicity in order to improve the therapeutic ratio.

The role of PD-1/PD-L1 axis and macrophage in the progression and treatment of cancer

PURPOSE

During the past decades, PD-1/PD-L1 axis blockade has become a remarkable promising therapy which has exerted durable anti-tumor effect and long-term remissions on part of cancers. However, there are still some patients which do not show good response to the PD-1/PD-L1 targeted monotherapy. Till now, the widely accepted anti-tumor mechanism of PD-1/PD-L1 blockade is rejuvenating T cells, there is lack of studies which focus on other components of the tumor environment in the treatment of cancer with PD-1/PD-L1 blockade, especially the complicated relationship between macrophages and PD-1/PD-L1 pathway during the progression and treatment of cancer.

METHODS

The relevant literatures from PubMed have been reviewed in this article.

RESULTS

Even though the widely accepted anti-tumor mechanism of PD-1/PD-L1 blockade therapy is rejuvenating T cells, latest studies have demonstrated the complicated relationship between macrophages and PD-1/PD-L1 pathway during the progression and treatment of cancer and their engagement has serious implications for the therapeutic effect of PD-1/PD-L1 blockade agents. We focus on the dual regulation mechanisms between PD-1/PD-L1 axis and macrophages, and further clarify the mechanisms of resistance to PD-1/PD-L1 inhibitors related with macrophages.

CONCLUSION

The combination of PD-1/PD-L1 blockade and macrophage-targeted therapy will exert synergetic anti-tumor effect and shape the future of cancer immunology and immunotherapy.

CAR T Cells for Solid Tumors: New Strategies for Finding, Infiltrating, and Surviving in the Tumor Microenvironment

Chimeric antigen receptor (CAR) T cells, T cells that have been genetically engineered to express a receptor that recognizes a specific antigen, have given rise to breakthroughs in treating hematological malignancies. However, their success in treating solid tumors has been limited. The unique challenges posed to CAR T cell therapy by solid tumors can be described in three steps: finding, entering, and surviving in the tumor. The use of dual CAR designs that recognize multiple antigens at once and local administration of CAR T cells are both strategies that have been used to overcome the hurdle of localization to the tumor. Additionally, the immunosuppressive tumor microenvironment has implications for T cell function in terms of differentiation and exhaustion, and combining CARs with checkpoint blockade or depletion of other suppressive factors in the microenvironment has shown very promising results to mitigate the phenomenon of T cell exhaustion. Finally, identifying and overcoming mechanisms associated with dysfunction in CAR T cells is of vital importance to generating CAR T cells that can proliferate and successfully eliminate tumor cells. The structure and costimulatory domains chosen for the CAR may play an important role in the overall function of CAR T cells in the TME, and “armored” CARs that secrete cytokines and third- and fourth-generation CARs with multiple costimulatory domains offer ways to enhance CAR T cell function.

Immune checkpoint inhibitors in urothelial cancer: recent updates and future outlook

Bladder cancer is the sixth most common cancer in the US and most tumors have urothelial (transitional cell) histology. Platinum-based chemotherapy has long been the standard of care in advanced disease, but long-term outcomes have largely remained poor. Since the peak incidence of bladder cancer is in the eighth decade of life and beyond, medical comorbidities may often limit the use of chemotherapy. Immune checkpoint inhibitors with their favorable toxicity profiles and notable antitumor activity have ushered in a new era in the treatment of advanced urothelial cancer (UC) with five agents targeting the PD-1/PD-L1 pathway being recently approved by the US Food and Drug administration. A plethora of clinical trials are ongoing in diverse disease settings, employing agents targeting PD-1/PD-L1 and related immune checkpoint pathways. While reactivating anti-tumor immunity, these agents may lead to a unique constellation of immune-related adverse events, which may warrant discontinuation of therapy and potential use of immunosuppression. Novel combinations with various treatment modalities and optimal sequencing of active therapies are being investigated in prospective clinical trials and retrospective registries. At the era of precision molecular medicine, and since patients do not respond uniformly to these agents, there is a growing need for identification and validation of biomarkers that can accurately predict treatment response and assist in patient selection. This review discusses current updates and future directions of immunotherapy in advanced UC.