VISTA is an inhibitory immune checkpoint that is increased after ipilimumab therapy in patients with prostate cancer

Different clinical significance of novel B7 family checkpoints VISTA and HHLA2 in human lung adenocarcinoma

Background: VISTA and HHLA2 are two recently identified members of the B7 homologue family of immune-regulatory molecules. But the expression patterns and clinical significance of VISTA and HHLA2 in lung adenocarcinoma (LUAD) remain largely unknown. Methods: Immunohistochemistry was performed to examine the expression of VISTA, HHLA2, PD-L1 and CD8⁺ tumor-infiltrating lymphocytes in 74 cases of LUAD. The expression of VISTA, HHLA2, PD-L1, CD68 and CD8 proteins was detected by multiplex immunofluorescence staining in the LUAD tissues. Results: High expression of VISTA and HHLA2 was observed in LUAD compared with noncancerous tissues. High VISTA expression in immune cells predicted a high mortality rate and worse survival. Conclusion: VISTA and HHLA2 are potential immunotherapeutic targets that possess different prognostic significance in LUAD.

VISTA in Soft Tissue Sarcomas: A Perspective for Immunotherapy?

(1) Background: V domain immunoglobulin suppressor of T cell activation (VISTA) plays a critical role in antitumor immunity and may be a valuable target in cancer immunotherapy. To date, it has never been studied in a large and well-characterised cohort of soft tissue sarcomas (STS). (2) Methods: Using immunohistochemistry, we examined VISTA expression in tumour tissues of 213 high-risk STS. We then analysed whether VISTA was associated with other clinicopathological parameters, including tumour-infiltrating lymphocyte (TIL) counts, programmed death receptor-1 (PD1), programmed death ligand-1 (PDL1), CD3, grading, and long-term survival. (3) Results: We observed VISTA expression in 96 (45%) of 213 specimens with distinct patterns ranging from 26 to 63% for histological subtypes. VISTA was associated with higher grade (G3 vs. G2, p = 0.019), higher TIL counts (p = 0.033), expression of PD1 (p = 0.046), PDL1 (p = 0.031), and CD3+ (p = 0.023). In patients without CD3+ TILs, 10-year survival was higher when VISTA was expressed compared to when there was no VISTA expression (p = 0.013). In a multivariate analysis, VISTA expression was independently associated with prolonged survival (p = 0.043). (4) Conclusions: VISTA is expressed in different STS subtypes and is associated with increased TILs, PD-1, PD-L1, and CD3 expression. Patients with VISTA+ tumours show improved survival. These results may help define future immunotherapeutic approaches in STS.

Towards an integrative understanding of cancer mechanobiology: calcium, YAP, and microRNA under biophysical forces

An increasing number of studies have demonstrated the significant roles of the interplay between microenvironmental mechanics in tissues and biochemical-genetic activities in resident tumor cells at different stages of tumor progression. Mediated by molecular mechano-sensors or -transducers, biomechanical cues in tissue microenvironments are transmitted into the tumor cells and regulate biochemical responses and gene expression through mechanotransduction processes. However, the molecular interplay between the mechanotransduction processes and intracellular biochemical signaling pathways remains elusive. This paper reviews the recent advances in understanding the crosstalk between biomechanical cues and three critical biochemical effectors during tumor progression: calcium ions (Ca²⁺), yes-associated protein (YAP), and microRNAs (miRNAs). We address the molecular mechanisms underpinning the interplay between the mechanotransduction pathways and each of the three effectors. Furthermore, we discuss the functional interactions among the three effectors in the context of soft matter and mechanobiology. We conclude by proposing future directions on studying the tumor mechanobiology that can employ Ca²⁺, YAP, and miRNAs as novel strategies for cancer mechanotheraputics. This framework has the potential to bring insights into the development of novel next-generation cancer therapies to suppress and treat tumors.

Analysis of the immune checkpoint V-domain Ig-containing suppressor of T-cell activation (VISTA) in endometrial cancer

V-domain Ig-containing suppressor of T-cell activation (VISTA) is a novel immune checkpoint protein and a potential immunotherapeutic target. However, its expression in endometrial cancer has not been clearly defined. This study aimed to investigate VISTA expression and determine its associations with clinicopathological features, molecular subtypes, programmed cell death-ligand 1 (PD-L1) expression, CD8+ T-cell count, and survival in a cohort of 839 patients with endometrial cancer. Using direct sequencing of the polymerase epsilon (POLE) exonuclease domain and immunohistochemistry for mismatch repair (MMR) proteins and p53, we stratified endometrial cancers into four molecular subtypes: POLE ultramutated, MMR-deficient, p53-mutant, and nonspecific molecular profile (NSMP). PD-L1, CD8, and VISTA were detected via immunohistochemistry. VISTA was expressed in the immune cells of 76.6% (643/839) of the samples and in the tumor cells of 6.8% (57/839). VISTA positivity in the immune cells was frequent in tumors staged I-III, those with positive PD-L1 or high CD8+ T-cell density, and those representing POLE ultramutated and MMR-deficient subtypes. Furthermore, VISTA positivity in tumor cells was more frequent in clear cell carcinoma samples. VISTA in immune cells was associated with improved survival in the entire cohort as well as in the endometrioid histology, stage I, PD-L1-negative, MMR-deficient, MMR-proficient, and high and low number of CD8+ T-cell-infiltrated tumor subgroups. VISTA in immune cells was a prognostic factor overall, as well as in patients with endometrioid histology, independent of molecular subtype or CD8+ T-cell density. The data produced by this study, which was the largest to focus on VISTA expression in patients with endometrial cancer to date, suggest that VISTA is a predictor of improved survival.

Rationally targeted anti-VISTA antibody that blockades the C-C' loop region can reverse VISTA immune suppression and remodel the immune microenvironment to potently inhibit tumor growth in an Fc independent manner

BACKGROUND

Despite significant progress in cancer immunotherapy in recent years, resistance to existing immune checkpoint therapies (ICT) is common. V-domain Ig suppressor of T cell activation (VISTA), a predominantly myeloid immune checkpoint regulator, represents a promising therapeutic target due to its role in suppressing proinflammatory antitumor responses in myeloid-enriched tumor microenvironments. However, uncertainty around the cognate VISTA ligand has made the development of effective anti-VISTA antibodies challenging. The expression of VISTA on normal immune cell subtypes argues for a neutralizing non-depleting antibody, however, previous reported anti-VISTA antibodies use IgG1 Fc isotypes that deplete VISTA+ cells by antibody dependent cellular cytotoxicity/complement dependent cytotoxicity and these antibodies have shown fast serum clearance and immune toxicities.

METHOD

Here we used a rational antibody discovery approach to develop the first Fc-independent anti-VISTA antibody, HMBD-002, that binds a computationally predicted functional epitope within the C-C-loop, distinct from other known anti-VISTA antibodies. This epitope is species-conserved allowing robust in vitro and in vivo testing of HMBD-002 in human and murine models of immune activation and cancer including humanized mouse models.

RESULTS

We demonstrate here that blockade by HMBD-002 inhibits VISTA binding to potential partners, including V-Set and Immunoglobulin domain containing 3, to reduce myeloid-derived suppression of T cell activity and prevent neutrophil migration. Analysis of immune cell milieu suggests that HMBD-002 treatment stimulates a proinflammatory phenotype characterized by a Th1/Th17 response, recapitulating a phenotype previously noted in VISTA knockout models. This mechanism of action is further supported by immune-competent syngenic and humanized mouse models of colorectal, breast and lung cancer where neutralizing VISTA, without depleting VISTA expressing cells, significantly inhibited tumor growth while decreasing infiltration of suppressive myeloid cells and increasing T cell activity. Finally, we did not observe either the fast serum clearance or immune toxicities that have been reported for IgG1 antibodies.

CONCLUSION

In conclusion, we have shown that VISTA-induced immune suppression can be reversed by blockade of the functional C-C' loop region of VISTA with a first-in-class rationally targeted and non-depleting IgG4 isotype anti-VISTA antibody, HMBD-002. This antibody represents a highly promising novel therapy in the VISTA-suppressed ICT non-responder population.

The evolving role of immune cells in prostate cancer

Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer-related death among men in western countries. Androgen deprivation therapy (ADT) is considered the standard therapy for recurrent prostate cancer; however, this therapy may lead to ADT resistance and tumor progression, which seems to be regulated by epithelial-mesenchymal transition (EMT) and/or neuroendocrine differentiation (NED). In addition, recent data suggested the involvement of either adaptive or innate infiltrated immune cells in the initiation, progression, metastasis, and treatment of prostate cancer. In this review, we outlined the characteristics and roles of these immune cells in the initiation, progression, metastasis, and treatments of prostate cancer. We also summarized the current therapeutic strategies in targeting immune cells of the prostate tumor microenvironment.

Profiling of immune features to predict immunotherapy efficacy

Immune checkpoint blockade (ICB) therapies exhibit substantial clinical benefit in different cancers, but relatively low response rates in the majority of patients highlight the need to understand mutual relationships among immune features. Here, we reveal overall positive correlations among immune checkpoints and immune cell populations. Clinically, patients benefiting from ICB exhibited increases for both immune stimulatory and inhibitory features after initiation of therapy, suggesting that the activation of the immune microenvironment might serve as the biomarker to predict immune response. As proof-of-concept, we demonstrated that the immune activation score (IS_Δ) based on dynamic alteration of interleukins in patient plasma as early as two cycles (4–6 weeks) after starting immunotherapy can accurately predict immunotherapy efficacy. Our results reveal a systematic landscape of associations among immune features and provide a noninvasive, cost-effective, and time-efficient approach based on dynamic profiling of pre- and on-treatment plasma to predict immunotherapy efficacy.

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Reveal a systematic landscape of associations among immune features in primary, metastatic, and ICB-treated tumors

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The activation of the immune microenvironment might serve as the biomarker of immunotherapy

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Dynamic alteration of interleukins in patient plasma can accurately predict immunotherapy efficacy

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Provide a noninvasive, cost-effective, and time-efficient approach to predict immunotherapy efficacy

Expression Profiles and Prognostic Value of Multiple Inhibitory Checkpoints in Head and Neck Lymphoepithelioma-Like Carcinoma

Background

Inhibitory checkpoints are promising antitumor targets and predictive biomarkers in a variety of cancers. We aimed to identify the expression levels and prognostic value of multiple inhibitory checkpoints supported by preclinical and clinical evidence in head and neck lymphoepithelioma-like carcinoma (HNLELC).

Methods

The expression of seven inhibitory checkpoints were evaluated in the tumor nest (TN) and tumor stroma (TS) of 102 HNLELC specimens using immunohistochemistry and digital pathology, and an inhibitory checkpoint-based signature (ICS) was subsequently constructed using the LASSO Cox regression model.

Results

PD-L1, B7H3, and IDO-1 were mostly expressed in the TN, with median H-score of TN vs TS: 63.6 vs 14.6; 8.1 vs 1.0; 61.5 vs 34.7 (all P < 0.001), whereas PD-1, TIM-3, LAG-3, and VISTA were mainly observed in the TS, with median H-score of TN vs TS: 0.2 vs 12.4, 3.4 vs 7.1, 6.2 vs 11.9, 16.4 vs 47.2 (all P < 0.001), respectively. The most common simultaneously expressed combinations consisted of PD-L1 + B7H3 + IDO-1 + TIM-3 + LAG-3 + VISTA and B7H3 + IDO-1 + TIM-3 + LAG-3 in the TN (both occurring in 8.8% of patients) and PD-L1 + B7H3 + IDO-1 in the TS (4.9%). In addition, high-ICS patients had shorter 5-year disease-free (40.6% vs 81.7%; P < 0.001), regional recurrence-free (63.5% vs 88.2%; P = 0.003), and overall survival (73.5% vs 92.9%; P = 0.006) than low-ICS patients. Multivariate analysis revealed that ICS represented an independent predictor, which could significantly complement the predictive performance of TNM stage for 3-year (AUC 0.724 vs 0.619, P = 0.014), 5-year (AUC 0.727 vs 0.640, P = 0.056), and 10-year disease-free survival (AUC 0.815 vs 0.709, P = 0.023).

Conclusions

The expression of inhibitory checkpoints and ICS classifier may increase the prognostic value of the TNM staging system and guide the rational design of personalized inhibitory checkpoint blockade therapy in HNLELC.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review (Part 6): Correlation of PD-L1 Expression with the Status of Mismatch Repair System, BRCA, PTEN, and Other Genes

Pembrolizumab (anti-PD-1) is allowed in selected metastatic castration-resistant prostate cancer (PC) patients showing microsatellite instability/mismatch repair system deficiency (MSI-H/dMMR). BRCA1/2 loss-of-function is linked to hereditary PCs and homologous recombination DNA-repair system deficiency: poly-ADP-ribose-polymerase inhibitors can be administered to BRCA-mutated PC patients. Recently, docetaxel-refractory metastatic castration-resistant PC patients with BRCA1/2 or ATM somatic mutations had higher response rates to pembrolizumab. PTEN regulates cell cycle/proliferation/apoptosis through pathways including the AKT/mTOR, which upregulates PD-L1 expression in PC. Our systematic literature review (PRISMA guidelines) investigated the potential correlations between PD-L1 and MMR/MSI/BRCA/PTEN statuses in PC, discussing few other relevant genes. Excluding selection biases, 74/677 (11%) PCs showed dMMR/MSI; 8/67 (12%) of dMMR/MSI cases were PD-L1+. dMMR-PCs included ductal (3%) and acinar (14%) PCs (all cases tested for MSI were acinar-PCs). In total, 15/39 (39%) PCs harbored BRCA1/2 aberrations: limited data are available for PD-L1 expression in these patients. 13/137 (10%) PTEN- PCs were PD-L1+; 10/29 (35%) PD-L1+ PCs showed PTEN negativity. SPOP mutations may increase PD-L1 levels, while the potential correlation between PD-L1 and ERG expression in PC should be clarified. Further research should verify how the efficacy of PD-1 inhibitors in metastatic castration-resistant PCs is related to dMMR/MSI, DNA-damage repair genes defects, or PD-L1 expression.

hDirect-MAP: projection-free single-cell modeling of response to checkpoint immunotherapy

There is a lack of robust generalizable predictive biomarkers of response to immune checkpoint blockade in multiple types of cancer. We develop hDirect-MAP, an algorithm that maps T cells into a shared high-dimensional (HD) expression space of diverse T cell functional signatures in which cells group by the common T cell phenotypes rather than dimensional reduced features or a distorted view of these features. Using projection-free single-cell modeling, hDirect-MAP first removed a large group of cells that did not contribute to response and then clearly distinguished T cells into response-specific subpopulations that were defined by critical T cell functional markers of strong differential expression patterns. We found that these grouped cells cannot be distinguished by dimensional-reduction algorithms but are blended by diluted expression patterns. Moreover, these identified response-specific T cell subpopulations enabled a generalizable prediction by their HD metrics. Tested using five single-cell RNA-seq or mass cytometry datasets from basal cell carcinoma, squamous cell carcinoma and melanoma, hDirect-MAP demonstrated common response-specific T cell phenotypes that defined a generalizable and accurate predictive biomarker.

The allergy mediator histamine confers resistance to immunotherapy in cancer patients via activation of the macrophage histamine receptor H1

Reinvigoration of antitumor immunity remains an unmet challenge. Our retrospective analyses revealed that cancer patients who took antihistamines during immunotherapy treatment had significantly improved survival. We uncovered that histamine and histamine receptor H1 (HRH1) are frequently increased in the tumor microenvironment and induce T cell dysfunction. Mechanistically, HRH1-activated macrophages polarize toward an M2-like immunosuppressive phenotype with increased expression of the immune checkpoint VISTA, rendering T cells dysfunctional. HRH1 knockout or antihistamine treatment reverted macrophage immunosuppression, revitalized T cell cytotoxic function, and restored immunotherapy response. Allergy, via the histamine-HRH1 axis, facilitated tumor growth and induced immunotherapy resistance in mice and humans. Importantly, cancer patients with low plasma histamine levels had a more than tripled objective response rate to anti-PD-1 treatment compared with patients with high plasma histamine. Altogether, pre-existing allergy or high histamine levels in cancer patients can dampen immunotherapy responses and warrant prospectively exploring antihistamines as adjuvant agents for combinatorial immunotherapy.

Immunosuppressive environment in response to androgen deprivation treatment in prostate cancer

RATIONALE

To invest the role of androgen deprivation therapy (ADT) on the tumor immune microenvironment of prostate cancer.

METHODS

Here we have profiled the transcriptomes of 19,227 single cells from 4 prostate tumors, including two cases who received ADT. To validated the single-cell analysis we use another group of patients receiving neoadjuvant ADT.

RESULTS

After receiving ADT treatment, the killing effect of prostate cancer immune cells on tumors is weakened, the interaction between immune cells and tumor cells is weakened, and the proportion of immunosuppressive cells Myeloid-derived suppressor cell (MDSC) and Regulatory T cells (Treg) cells increases.

CONCLUSIONS

Our results highlight that ADT induces immunosuppressive in the prostate tumor microenvironment. These data have important implications for combining ADT with immunotherapy.

Monoclonal Antibodies to CTLA-4 with Focus on Ipilimumab

The immune checkpoint cytotoxic T lymphocyte-associated antigen 4 (CTLA-4 or CD152) is a negative regulator of T-cell-mediated immune responses which plays a critical role in suppressing autoimmunity and maintaining immune homeostasis. Because of its inhibitory activity on T cells, CTLA-4 has been investigated as a drug target to induce immunostimulation, blocking the interaction with its ligands. The antitumor effects mediated by CTLA-4 blockade have been attributed to a sustained active immune response against cancer cells, due to the release of a brake on T cell activation. Ipilimumab (Yervoy, Bristol-Myers Squibb) is a fully human anti-CTLA-4 IgG1κ monoclonal antibody (mAb) that represents the first immune checkpoint inhibitor approved as monotherapy by FDA and EMA in 2011 for the treatment of unresectable/metastatic melanoma. In 2015, FDA also granted approval to ipilimumab monotherapy as adjuvant treatment of stage III melanoma to reduce the risk of tumour recurrence. The subsequent approved indications of ipilimumab for metastatic melanoma, regardless of BRAF mutational status, and other advanced/metastatic solid tumours always involve its use in association with the anti-programmed cell death protein 1 (PD-1) mAb nivolumab. Currently, ipilimumab is evaluated in ongoing clinical trials for refractory/advanced solid tumours mainly in combination with additional immunostimulating agents.

PD-1H Expression Associated With CD68 Macrophage Marker Confers an Immune-Activated Microenvironment and Favorable Overall Survival in Human Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is the most common type of esophageal carcinoma (EC) in China. Although the PD-1 inhibitor pembrolizumab has been approved to treat patients with EC, its therapeutic efficacy is limited. Thus, additional immunotherapeutic targets for EC treatment are needed. Programmed Death-1 Homolog (PD-1H) is a negative checkpoint regulator that inhibits antitumor immune responses. Here, PD-1H expression in 114 patients with ESCC was evaluated by immunohistochemistry. Next, 12 randomly selected tumor tissue sections were used to assess the colocalization of PD-1H protein and multiple immune markers by multiplex immunohistochemistry. Our results demonstrated that PD-1H was expressed at high frequency in ESCC tumor tissues (85.1%). PD-1H protein was predominantly expressed in CD68⁺ tumor-associated macrophages and expressed at low levels in CD4⁺ T cells and CD8⁺ T cells in ESCC tumor tissues. Furthermore, based on ESCC data in The Cancer Genome Atlas (TCGA), the gene expression levels of PD-1H were positively associated with the infiltration levels of immune-activated cells especially CD8⁺ cytotoxic T cells. In contrast, the gene expression levels of PD-1H were negatively correlated with myeloid-derived suppressor cells (MDSCs). Importantly, PD-1H expression in tumor sites was significantly correlated with favorable overall survival in patients with ESCC. Collectively, our findings first provided direct information on the PD-1H expression pattern and distribution in ESCC, and positive correlation of PD-1H expression with overall survival suggested PD-1H expression levels could be a significant prognostic indicator for patients with ESCC. Future studies need to explore the immunoregulatory of PD-1H in the tumor microenvironment of ESCC.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 7: PD-L1 Expression in Liquid Biopsy

Liquid biopsy is an accessible, non-invasive diagnostic tool for advanced prostate cancer (PC) patients, potentially representing a real-time monitoring test for tumor evolution and response to treatment through the analysis of circulating tumor cells (CTCs) and exosomes. We performed a systematic literature review (PRISMA guidelines) to describe the current knowledge about PD-L1 expression in liquid biopsies of PC patients: 101/159 (64%) cases revealed a variable number of PD-L1+ CTCs. Outcome correlations should be investigated in larger series. Nuclear PD-L1 expression by CTCs was occasionally associated with worse prognosis. Treatment (abiraterone, enzalutamide, radiotherapy, checkpoint-inhibitors) influenced PD-L1+ CTC levels. Discordance in PD-L1 status was detected between primary vs. metastatic PC tissue biopsies and CTCs vs. corresponding tumor tissues. PD-L1 is also released by PC cells through soluble exosomes, which could inhibit the T cell function, causing immune evasion. PD-L1+ PC-CTC monitoring and genomic profiling may better characterize the ongoing aggressive PC forms compared to PD-L1 evaluation on primary tumor biopsies/prostatectomy specimens (sometimes sampled a long time before recurrence/progression). Myeloid-derived suppressor cells and dendritic cells (DCs), which may have immune-suppressive effects in tumor microenvironment, have been found in PC patients circulation, sometimes expressing PD-L1. Occasionally, their levels correlated to clinical outcome. Enzalutamide-progressing castration-resistant PC patients revealed increased PD-1+ T cells and circulating PD-L1/2+ DCs.

Immunotherapy for Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is characterized by extensive tumor heterogeneity at both the pathologic and molecular levels, particularly accelerated aggressiveness, and terrible metastasis. It is responsible for the increased mortality of breast cancer patients. Due to the negative expression of estrogen receptors, progesterone receptors, and human epidermal growth factor receptor 2, the progress of targeted therapy has been hindered. Higher immune response in TNBCs than for other breast cancer types makes immunotherapy suitable for TNBC therapy. At present, promising treatments in immunotherapy of TNBC include immune checkpoints (ICs) blockade therapy, adoptive T-cell immunotherapy, and tumor vaccine immunotherapy. In addition, nanomedicines exhibit great potential in cancer therapy through the enhanced permeability and retention (EPR) effect. Immunotherapy-involved combination therapy may exert synergistic effects by combining with other treatments, such as traditional chemotherapy and new treatments, including photodynamic therapy (PTT), photodynamic therapy (PDT), and sonodynamic therapy (SDT). This review focuses on introducing the principles and latest development as well as progress in using nanocarriers as drug-delivery systems for the immunotherapy of TNBC.

Agonistic nanobodies and antibodies to human VISTA

The V-domain Ig Suppressor of T-cell Activation (VISTA) is an immune checkpoint regulator that suppresses immune responses and is readily expressed on human and murine myeloid cells and T cells. This immunosuppressive pathway can be activated using VISTA agonists. Here, we report the development of murine anti-human VISTA (anti-hVISTA) monoclonal antibodies (mAbs), anti-hVISTA nanobodies (Nbs), and cross-reactive rat anti-murine/human VISTA (anti-hmVISTA) mAbs. All mAbs and Nbs generated bound to VISTA (human and/or murine) with dissociation constants in the sub-nanomolar or low nanomolar range. Competition analysis revealed that the selected Nbs bound the same or a nearby epitope(s) as the human VISTA-specific mAbs. However, the cross-reactive mAbs only partially competed with Nbs for binding to hVISTA. All mAbs and one Nb (hVISTANb7) were able to strongly detect VISTA expression on primary human monocytes. Importantly, the murine anti-hVISTA mAbs 7E12 and 7G5 displayed strong agonistic activity in human peripheral blood mononuclear cell cultures, while Nb7 and rat anti-hmVISTA mAbs 3C3, 7C6, 7C7, and 7G1 also behaved as hVISTA agonists, albeit to a lesser extent. Cross-reactive mAbs 7C7 and 7G1 further displayed agonistic potential in murine splenocyte assays. Importantly, mAb 7G1 significantly reduced inflammation associated with the murine model of imiquimod-induced psoriasis. These agonistic VISTA mAbs may represent therapeutic leads to treat inflammatory disorders.

Clinical experience with CTLA-4 blockade for cancer immunotherapy: From the monospecific monoclonal antibody ipilimumab to probodies and bispecific molecules targeting the tumor microenvironment

The immune checkpoint cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is an inhibitory regulator of T-cell mediated responses that has been investigated as target of monoclonal antibodies (mAbs) for cancer immunotherapy. The anti-CTLA-4 mAb ipilimumab represents the first immune checkpoint inhibitor that significantly improved overall survival in patients with unresectable/metastatic melanoma. The subsequent approved indications (often in the first-line setting) for melanoma and other advanced/metastatic solid tumors always require ipilimumab combination with nivolumab, an anti-programmed cell death protein 1 (PD-1) mAb. However, the improved clinical efficacy of the mAb combination is associated with increased immune-related adverse events, which might require treatment discontinuation even in responding patients. This drawback is expected to be overcome by the recent development of anti-CTLA-4 probodies proteolitycally activated in the tumor microenvironment and bispecific molecules targeting both CTLA-4 and PD-1, whose co-expression is characteristic of tumor-infiltrating T cells. These molecules would preferentially stimulate immune responses against the tumor, reducing toxicity toward normal tissues.

Multi-scale Pan-cancer Integrative Analyses Identify the STAT3-VSIR Axis as a key Immunosuppressive Mechanism in Head and Neck Cancer

PURPOSE

VSIR is a novel immune checkpoint protein whose expression on tumor cells across cancers remains largely uncharacterized. Here we purposed to decode the pan-cancer biologic and clinical significance of VSIR over-expression in the tumor compartment.

EXPERIMENTAL DESIGN

We performed multi-omics integrative analyses of 9735 tumor samples to identify cancers with non-leukocytic expression of VSIR (VSIR-High), followed by association with overall survival and immune cell infiltration levels. Orthogonal assessments of VSIR protein expression and lymphocytic infiltration were performed using Quantitative immunofluorescence.

RESULTS

Integrative modeling identified a subset of cancer types as being enriched for VSIR-High tumors. VSIR-High tumors were associated with significantly poorer overall survival in immunogenic Ovarian Serous Adenocarcinoma (SA) and Oral Cavity Squamous Cell Carcinoma (SCC). QIF assessments in an independent validation cohort confirmed over-expression of VSIR as being associated with poorer overall survival within immunogenic Oral Cavity SCC. VSIR over-expression was associated with lower CD4 Helper T-cell infiltration in both Ovarian SA and Oral Cavity SCC, but did not impact CD8 T-cell infiltration. VSIR over-expressing tumors in both cancer types exhibited significantly higher STAT3 signaling activity. Pharmacologic inhibition of STAT3 signaling resulted in dose-dependent reduction of VSIR expression in Ovarian SA & Oral Cavity SCC cells.

CONCLUSIONS

The STAT3-VSIR axis is a potentially significant immuno-modulatory mechanism in oral cavity and ovarian cancers, whose activation is associated with poorer survival and an immune microenvironment marked by decreased CD4 helper T-cell activity. The role of VSIR as a tumor-intrinsic modulator of resistance to immunotherapy warrants further exploration.

Biomarkers for Treatment Response in Advanced Prostate Cancer

Simple Summary

Prostate cancer is a leading cause of cancer-related death among males. Many treatments are available to manage the disease, but despite this, ultimately advanced prostate cancer is incurable and fatal. In order to improve survival and minimize side effects from these various treatments, the treatments need to be given in an optimal sequence or combination. This optimal use of therapies must be individualized, and biomarkers can be used for these decisions. Biomarkers can be useful in predicting whether a patient will respond to a treatment option and may help avoid use of therapies that are not expected to be effective. Many biomarkers are already in clinical use while many others are currently being investigated and may become part of clinical practice in future. In this review, we discuss both established and novel biomarkers with a role in management of advanced prostate cancer.

Abstract

Multiple treatment options with different mechanisms of action are currently available for the management of metastatic prostate cancer. However, the optimal use of these therapies—specifically, the sequencing of therapies—is not well defined. In order to obtain the best clinical outcomes, patients need to be treated with the therapies that are most likely to provide benefit and avoid toxic therapies that are unlikely to be effective. Ideally, predictive biomarkers that allow for the selection of the therapies most likely to be of benefit would be employed for each treatment decision. In practice, biomarkers including tumor molecular sequencing, circulating tumor DNA, circulating tumor cell enumeration and androgen receptor characteristics, and tumor cell surface expression (PSMA), all may have a role in therapy selection. In this review, we define the established prognostic and predictive biomarkers for therapy in advanced prostate cancer and explore emerging biomarkers.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 5: Epigenetic Regulation of PD-L1

Epigenetic alterations (including DNA methylation or miRNAs) influence oncogene/oncosuppressor gene expression without changing the DNA sequence. Prostate cancer (PC) displays a complex genetic and epigenetic regulation of cell-growth pathways and tumor progression. We performed a systematic literature review (following PRISMA guidelines) focused on the epigenetic regulation of PD-L1 expression in PC. In PC cell lines, CpG island methylation of the CD274 promoter negatively regulated PD-L1 expression. Histone modifiers also influence the PD-L1 transcription rate: the deletion or silencing of the histone modifiers MLL3/MML1 can positively regulate PD-L1 expression. Epigenetic drugs (EDs) may be promising in reprogramming tumor cells, reversing epigenetic modifications, and cancer immune evasion. EDs promoting a chromatin-inactive transcriptional state (such as bromodomain or p300/CBP inhibitors) downregulated PD-L1, while EDs favoring a chromatin-active state (i.e., histone deacetylase inhibitors) increased PD-L1 expression. miRNAs can regulate PD-L1 at a post-transcriptional level. miR-195/miR-16 were negatively associated with PD-L1 expression and positively correlated to longer biochemical recurrence-free survival; they also enhanced the radiotherapy efficacy in PC cell lines. miR-197 and miR-200a-c positively correlated to PD-L1 mRNA levels and inversely correlated to the methylation of PD-L1 promoter in a large series. miR-570, miR-34a and miR-513 may also be involved in epigenetic regulation.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 3: PD-L1, Intracellular Signaling Pathways and Tumor Microenvironment

The tumor microenvironment (TME) includes immune (T, B, NK, dendritic), stromal, mesenchymal, endothelial, adipocytic cells, extracellular matrix, and cytokines/chemokines/soluble factors regulating various intracellular signaling pathways (ISP) in tumor cells. TME influences the survival/progression of prostate cancer (PC), enabling tumor cell immune-evasion also through the activation of the PD-1/PD-L1 axis. We have performed a systematic literature review according to the PRISMA guidelines, to investigate how the PD-1/PD-L1 pathway is influenced by TME and ISPs. Tumor immune-escape mechanisms include suppression/exhaustion of tumor infiltrating cytotoxic T lymphocytes, inhibition of tumor suppressive NK cells, increase in immune-suppressive immune cells (regulatory T, M2 macrophagic, myeloid-derived suppressor, dendritic, stromal, and adipocytic cells). IFN-γ (the most investigated factor), TGF-β, TNF-α, IL-6, IL-17, IL-15, IL-27, complement factor C5a, and other soluble molecules secreted by TME components (and sometimes increased in patients' serum), as well as and hypoxia, influenced the regulation of PD-L1. Experimental studies using human and mouse PC cell lines (derived from either androgen-sensitive or androgen-resistant tumors) revealed that the intracellular ERK/MEK, Akt-mTOR, NF-kB, WNT and JAK/STAT pathways were involved in PD-L1 upregulation in PC. Blocking the PD-1/PD-L1 signaling by using immunotherapy drugs can prevent tumor immune-escape, increasing the anti-tumor activity of immune cells.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 1: Focus on Immunohistochemical Results with Discussion of Pre-Analytical and Interpretation Variables

Immunotherapy targeting the PD-1-PD-L1 axis yielded good results in treating different immunologically ''hot'' tumors. A phase II study revealed good therapeutic activity of pembrolizumab in selected prostatic carcinoma (PC)-patients. We performed a systematic literature review (PRISMA guidelines), which analyzes the immunohistochemical expression of PD-L1 in human PC samples and highlights the pre-analytical and interpretation variables. Interestingly, 29% acinar PCs, 7% ductal PCs, and 46% neuroendocrine carcinomas/tumors were PD-L1+ on immunohistochemistry. Different scoring methods or cut-off criteria were applied on variable specimen-types, evaluating tumors showing different clinic-pathologic features. The positivity rate of different PD-L1 antibody clones in tumor cells ranged from 3% (SP142) to 50% (ABM4E54), excluding the single case tested for RM-320. The most tested clone was E1L3N, followed by 22C3 (most used for pembrolizumab eligibility), SP263, SP142, and 28-8, which gave the positivity rates of 35%, 11-41% (depending on different scoring systems), 6%, 3%, and 15%, respectively. Other clones were tested in <200 cases. The PD-L1 positivity rate was usually higher in tumors than benign tissues. It was higher in non-tissue microarray specimens (41-50% vs. 15%), as PC cells frequently showed heterogenous or focal PD-L1-staining. PD-L1 was expressed by immune or stromal cells in 12% and 69% cases, respectively. Tumor heterogeneity, inter-institutional preanalytics, and inter-observer interpretation variability may account for result biases.

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 4: Experimental Treatments in Pre-Clinical Studies (Cell Lines and Mouse Models)

In prostate cancer (PC), the PD-1/PD-L1 axis regulates various signaling pathways and it is influenced by extracellular factors. Pre-clinical experimental studies investigating the effects of various treatments (alone or combined) may discover how to overcome the immunotherapy-resistance in PC-patients. We performed a systematic literature review (PRISMA guidelines) to delineate the landscape of pre-clinical studies (including cell lines and mouse models) that tested treatments with effects on PD-L1 signaling in PC. NF-kB, MEK, JAK, or STAT inhibitors on human/mouse, primary/metastatic PC-cell lines variably down-modulated PD-L1-expression, reducing chemoresistance and tumor cell migration. If PC-cells were co-cultured with NK, CD8+ T-cells or CAR-T cells, the immune cell cytotoxicity increased when PD-L1 was downregulated (opposite effects for PD-L1 upregulation). In mouse models, radiotherapy, CDK4/6-inhibitors, and RB deletion induced PD-L1-upregulation, causing PC-immune-evasion. Epigenetic drugs may reduce PD-L1 expression. In some PC experimental models, blocking only the PD-1/PD-L1 pathway had limited efficacy in reducing the tumor growth. Anti-tumor effects could be increased by combining the PD-1/PD-L1 blockade with other approaches (inhibitors of tyrosine kinase, PI3K/mTOR or JAK/STAT3 pathways, p300/CBP; anti-RANKL and/or anti-CTLA-4 antibodies; cytokines; nitroxoline; DNA/cell vaccines; radiotherapy/Radium-223).

What Do We Have to Know about PD-L1 Expression in Prostate Cancer? A Systematic Literature Review. Part 2: Clinic-Pathologic Correlations

Many studies have investigated the potential prognostic and predictive role of PD-L1 in prostatic carcinoma (PC). We performed a systematic literature review (PRISMA guidelines) to critically evaluate human tissue-based studies (immunohistochemistry, molecular analysis, etc.), experimental research (cell lines, mouse models), and clinical trials. Despite some controversial results and study limitations, PD-L1 expression by tumor cells may be related to clinic-pathologic features of adverse outcome, including advanced tumor stage (high pT, presence of lymph node, and distant metastases), positivity of surgical margins, high Grade Group, and castration resistance. Different PD-L1 positivity rates may be observed in matched primary PCs and various metastatic sites of the same patients. Over-fixation, type/duration of decalcification, and PD-L1 antibody clone may influence the immunohistochemical analysis of PD-L1 on bone metastases. PD-L1 seemed expressed more frequently by castration-resistant PCs (49%) as compared to hormone-sensitive PCs (17%). Some series found that PD-L1 positivity was associated with decreased time to castration resistance. Treatment with ipilimumab, cyclophosphamide/GVAX/degarelix, or degarelix alone may increase PD-L1 expression. Correlation of PD-L1 positivity with overall survival and outcomes related to tumor recurrence were rarely investigated; the few analyzed series produced conflicting results and sometimes showed limitations. Further studies are required. The testing and scoring of PD-L1 should be standardized.

Discovery of Novel Inhibitors From Medicinal Plants for V-Domain Ig Suppressor of T-Cell Activation

V-domain Ig suppressor of T cell activation (VISTA) is an immune checkpoint and is a type I transmembrane protein. VISTA is linked to immunotherapy resistance, and it is a potential immune therapeutic target, especially for triple-negative breast cancer. It expresses at a high concentration in regulatory T cells and myeloid-derived suppressor cells, and its functional blockade is found to delay tumor growth. A useful medicinal plant database for drug designing (MPD3), which is a collection of phytochemicals from diverse plant families, was employed in virtual screening against VISTA to prioritize natural inhibitors against VISTA. Three compounds, Paratocarpin K (PubChem ID: 14187087), 3-(1H-Indol-3-yl)-2-(trimethylazaniumyl)propanoate (PubChem ID: 3861164), and 2-[(5-Benzyl-4-ethyl-1,2,4-triazol-3-yl)sulfanylmethyl]-5-methyl-1,3,4-oxadiazole (PubChem ID: 6494266), having binding energies stronger than -6 kcal/mol were found to have two common hydrogen bond interactions with VISTA active site residues: Arg54 and Arg127. The dynamics of the compound-VISTA complexes were further explored to infer binding stability of the systems. Results revealed that the compound 14187087 and 6494266 systems are highly stable with an average RMSD of 1.31 Å. Further affirmation on the results was achieved by running MM-GBSA on the MD simulation trajectories, which re-ranked 14187087 as the top-binder with a net binding energy value of -33.33 kcal/mol. In conclusion, the present study successfully predicted natural compounds that have the potential to block the function of VISTA and therefore can be utilized further in experimental studies to validate their real anti-VISTA activity.

Potential biomarkers and resistance mechanisms of atezolizumab in a patient with lung squamous cell carcinoma

Background: At present, only a small fraction of patients with cancer benefit from treatment with immune checkpoint inhibitors, the reasons for which are not fully understood. Monitoring molecular and immunologic changes during treatment with immune checkpoint inhibitors would help to identify potential biomarkers and mechanisms associated with resistance and guide subsequent treatment. Methods: The authors report on a patient previously treated for lung squamous cell carcinoma who received atezolizumab-based therapy for 24 months. Results & Conclusion: Analysis of samples before and after atezolizumab treatment suggested that genetic mutations in EGFR exon 20 insertion, phosphatase and PTEN and NOTCH1 as well as changes in tumor immune microenvironment may be associated with acquired resistance to immune checkpoint inhibitor therapy.

Kidney VISTA prevents IFNγ-IL-9 axis-mediated tubulointerstitial fibrosis after acute glomerular injury

Severe glomerular injury ultimately leads to tubulointerstitial fibrosis that determines patient outcome, but the immunological molecules connecting these processes remain undetermined. The present study addressed whether V-domain Ig suppressor of T cell activation (VISTA), constitutively expressed in kidney macrophages, plays a protective role in tubulointerstitial fibrotic transformation after acute antibody-mediated glomerulonephritis. After acute glomerular injury using nephrotoxic serum, tubules in the VISTA-deficient (Vsir–/–) kidney suffered more damage than those in WT kidneys. When interstitial immune cells were examined, the contact frequency of macrophages with infiltrated T cells increased and the immunometabolic features of T cells changed to showing high oxidative phosphorylation and fatty acid metabolism and overproduction of IFN-γ. The Vsir–/– parenchymal tissue cells responded to this altered milieu of interstitial immune cells as more IL-9 was produced, which augmented tubulointerstitial fibrosis. Blocking antibodies against IFN-γ and IL-9 protected the above pathological process in VISTA-depleted conditions. In human samples with acute glomerular injury (e.g., antineutrophil cytoplasmic autoantibody vasculitis), high VISTA expression in tubulointerstitial immune cells was associated with low tubulointerstitial fibrosis and good prognosis. Therefore, VISTA is a sentinel protein expressed in kidney macrophages that prevents tubulointerstitial fibrosis via the IFN-γ/IL-9 axis after acute antibody-mediated glomerular injury.

VISTA Is a Diagnostic Biomarker and Immunotherapy Target of Aggressive Feline Mammary Carcinoma Subtypes

Simple Summary

Mammary tumors are common in cats, showing aggressive behavior and few therapeutic options. Recently, feline mammary carcinomas have become a reliable cancer model for human breast cancer studies, due to the similarities between the two species. Thus, the identification of new tumor biomarkers and therapeutic targets to improve cat’s prognosis is needed. VISTA is an important immune checkpoint protein that has gained importance over the past few years in women’s cancers. In this study, the serum VISTA levels and tumor expression were analyzed in cats with mammary tumors, being correlated with other immune checkpoints. In the diseased animals, VISTA is overexpressed in more aggressive tumor subtypes (HER2-positive and triple-negative), showing a positive correlation with the expression of VISTA in tumor-infiltrating lymphocytes, and is associated with an immunosuppressive status, suggesting that VISTA could be a promising non-invasive prognostic biomarker and therapeutic target in cats with mammary carcinomas, as reported in humans.

Abstract

Feline mammary carcinoma (FMC) is a common neoplasia, showing aggressive clinicopathological features, without viable therapeutic options. The study of tumor microenvironment has gained importance, due to the ability to control tumor progression by regulating the immune response. Considering the lack of knowledge, feline serum VISTA levels from cats with mammary carcinoma were compared with healthy controls, and with serum levels of PD-1/PD-L1, CTLA-4, LAG-3, IL-6, and TNF-α. In parallel, VISTA tumor expression was evaluated in FMC samples. The obtained data revealed that serum VISTA levels were significantly higher in cats presenting HER2-positive (p = 0.0025) or triple-negative subtypes (p = 0.0019), with higher serum levels in luminal A (p = 0.0025) correlated to the presence of metastasis (p = 0.0471). Furthermore, in HER2-positive or triple-negative tumors, correlations were obtained between serum VISTA levels and the serum levels of the above-mentioned molecules. In tumors, VISTA expression revealed a stronger intensity in cancer cells, when compared to TILs (p < 0.0001). Stratifying the samples by subtypes, a higher number of VISTA-positive TILs was observed in the HER2-positive subtype, compared with triple-negative tumors (p = 0.0138). In conclusion, results support the development of therapeutic strategies for HER2-positive and triple-negative FMC subtypes, reinforcing the use of cats as a human oncology model.

VISTA inhibitors in cancer immunotherapy: a short perspective on recent progresses

V-domain immunoglobulin (Ig) suppressor of T cell activation (VISTA) is a novel negative checkpoint regulator that mediates T cell proliferation and cytokine production. The VISTA signaling pathway blockade has been proved as a promising strategy for cancer immunotherapy. Recent VISTA sequence analysis and crystal structure investigations have revealed its independent and unique function as compared with B7 family members, such as PD-1. This review will discuss VISTA binding partners and compare the structural differences between VISTA and other B7 family members, focusing on VISTA functions in immune activation and maintaining T cell quiescence. Recent progress and the therapeutic potential of biomacromolecules, such as monoclonal antibodies (mAbs) and small molecules targeting VISTA, are also discussed. Among these, a first-in-class small-molecule antagonist, CA-170, is highlighted.

Hallmarks of response, resistance, and toxicity to immune checkpoint blockade

Unprecedented advances have been made in cancer treatment with the use of immune checkpoint blockade (ICB). However, responses are limited to a subset of patients, and immune-related adverse events (irAEs) can be problematic, requiring treatment discontinuation. Iterative insights into factors intrinsic and extrinsic to the host that impact ICB response and toxicity are critically needed. Our understanding of the impact of host-intrinsic factors (such as the host genome, epigenome, and immunity) has evolved substantially over the past decade, with greater insights on these factors and on tumor and immune co-evolution. Additionally, we are beginning to understand the impact of acute and cumulative exposures-both internal and external to the host (i.e., the exposome)-on host physiology and response to treatment. Together these represent the current day hallmarks of response, resistance, and toxicity to ICB. Opportunities built on these hallmarks are duly warranted.

Interaction Between Modern Radiotherapy and Immunotherapy for Metastatic Prostate Cancer

Prostate cancer is the most frequently diagnosed cancer in men and a leading cause of cancer-related death. In recent decades, the development of immunotherapies has resulted in great promise to cure metastatic disease. However, prostate cancer has failed to show any significant response, presumably due to its immunosuppressive microenvironment. There is therefore growing interest in combining immunotherapy with other therapies able to relieve the immunosuppressive microenvironment. Radiation therapy remains the mainstay treatment for prostate cancer patients, is known to exhibit immunomodulatory effects, depending on the dose, and is a potent inducer of immunogenic tumor cell death. Optimal doses of radiotherapy are thus expected to unleash the full potential of immunotherapy, improving primary target destruction with further hope of inducing immune-cell-mediated elimination of metastases at distance from the irradiated site. In this review, we summarize the current knowledge on both the tumor immune microenvironment in prostate cancer and the effects of radiotherapy on it, as well as on the use of immunotherapy. In addition, we discuss the utility to combine immunotherapy and radiotherapy to treat oligometastatic metastatic prostate cancer.

Combined CTLA-4 and PD-L1 blockade in patients with chemotherapy-naïve metastatic castration-resistant prostate cancer is associated with increased myeloid and neutrophil immune subsets in the bone microenvironment

BACKGROUND

Immune checkpoint therapy (ICT) has low response rates in patients with metastatic castration-resistant prostate cancer (mCRPC), in part due to few T cells in the tumor microenvironment (TME). Anti-cytotoxic T lymphocyte-associated protein 4 (CTLA-4) promotes intratumoral T cell infiltration but induces upregulation of PD-1 and programmed death ligand-1 (PD-L1) within the prostate TME. Combined anti-CTLA-4 plus anti-PD-1 can partly overcome this adaptive resistance and was recently shown to augment responses in patients with mCRPC with measurable disease. Although bone is the most common site of metastasis in prostate cancer, patients with bone-predominant disease are frequently excluded from trials because they lack measurable disease, which limits assessment of disease progression and tissue sampling. We therefore designed this study to investigate combined ICT in mCRPC to bone.

HYPOTHESIS

Combined anti-CTLA-4 (tremelimumab) plus anti-PD-L1 (durvalumab) is safe and well tolerated in patients with chemotherapy-naïve mCRPC to bone.

PATIENTS AND METHODS

In this single-arm pilot study, men with chemotherapy-naïve mCRPC to bone received tremelimumab (75 mg intravenous) plus durvalumab (1500 mg intravenous) every 4 weeks (up to four doses), followed by durvalumab (1500 mg intravenous) maintenance every 4 weeks (up to nine doses). The primary endpoint was incidence of adverse events. Secondary endpoints included serum prostate-specific antigen (PSA), progression-free survival (PFS), radiographic PFS (rPFS), and maximal PSA decline.

RESULTS

Twenty-six patients were treated between August 8, 2017 and March 28, 2019. Grade ≥3 treatment-related adverse events (TRAEs) occurred in 11 patients (42%), with no grade 4 or 5 events. TRAEs leading to discontinuation occurred in three patients (12%). PSA decline ≥50% occurred in three patients (12%). Six patients (24%) achieved stable disease for >6 months. At a median follow-up of 43.6 months, median rPFS was 3.7 months (95% CI: 1.9 to 5.7), and median overall survival was 28.1 months (95% CI: 14.5 to 37.3). Post-treatment evaluation of the bone microenvironment revealed transcriptional upregulation in myeloid and neutrophil immune subset signatures and increased expression of inhibitory immune checkpoints.

CONCLUSIONS

Tremelimumab plus durvalumab was safe and well tolerated in patients with chemotherapy-naïve mCRPC to bone, with potential activity in a small number of patients as measured by rPFS. Combination of CTLA-4 and PD-L1 blockade with therapies targeting the myeloid compartment or other inhibitory immune receptors may be necessary to overcome mechanisms of resistance within prostate bone microenvironment.

TRIAL REGISTRATION NUMBER

NCT03204812.

Targeting the spectrum of immune checkpoints in prostate cancer

Introduction: The proven efficacy of the cellular vaccine sipuleucel-T in 2010 led to optimism about immunotherapeutic approaches for the treatment of prostate cancer. Some surmised that prostate cancer might be an ideal target for immune-mediated killing given that the prostate is not an essential organ and expresses unique proteins including prostate-specific antigen, prostate-specific membrane antigen, and prostatic acid phosphatase that could be targeted without side effects. Subsequently, antibodies that inhibit the T cell checkpoints PD1 and CTLA4 were shown to stimulate antitumor immune responses, leading to tumor regression in several cancer types. These therapies have since been tested in several studies as treatments for prostate cancer, but appear to have limited efficacy in molecularly unselected patients.Areas covered: In this review, we discuss these studies and evaluate features of prostate cancer and its host environment that may render it generally resistant to CTLA4 and PD1 blockade. We provide an overview of alternate immune checkpoints that may hold greater significance in this disease.Expert opinion: Combination therapies to target multiple layers of alternate immune checkpoints may be required for an effective immune response to prostate cancer. We discuss combination therapies currently being investigated.

Remodeling the Tumor Myeloid Landscape to Enhance Antitumor Antibody Immunotherapies

Among the diverse tumor resident immune cell types, tumor-associated macrophages (TAMs) are often the most abundant, possess an anti-inflammatory phenotype, orchestrate tumor immune evasion and are frequently associated with poor prognosis. However, TAMs can also be harnessed to destroy antibody-opsonized tumor cells through the process of antibody-dependent cellular phagocytosis (ADCP). Clinically important tumor-targeting monoclonal antibodies (mAb) such as Rituximab, Herceptin and Cetuximab, function, at least in part, by inducing macrophages to eliminate tumor cells via ADCP. For IgG mAb, this is mediated by antibody-binding activating Fc gamma receptors (FcγR), with resultant phagocytic activity impacted by the level of co-engagement with the single inhibitory FcγRIIb. Approaches to enhance ADCP in the tumor microenvironment include the repolarization of TAMs to proinflammatory phenotypes or the direct augmentation of ADCP by targeting so-called 'phagocytosis checkpoints'. Here we review the most promising new strategies targeting the cell surface molecules present on TAMs, which include the inhibition of 'don't eat me signals' or targeting immunostimulatory pathways with agonistic mAb and small molecules to augment tumor-targeting mAb immunotherapies and overcome therapeutic resistance.

Cancer immunotherapy: it's time to better predict patients' response

In less than a decade, half a dozen immune checkpoint inhibitors have been approved and are currently revolutionising the treatment of many cancer (sub)types. With the clinical evaluation of novel delivery approaches (e.g. oncolytic viruses, cancer vaccines, natural killer cell-mediated cytotoxicity) and combination therapies (e.g. chemo/radio-immunotherapy) as well as the emergence of novel promising targets (e.g. TIGIT, LAG-3, TIM-3), the 'immunotherapy tsunami' is not about to end anytime soon. However, this enthusiasm in the field is somewhat tempered by both the relatively low percentage (<15%) of patients who display an effective anti-cancer immune response and the inability to accurately identify them. Recently, several existing or acquired features/parameters have been shown to impact the efficacy of immune checkpoint inhibitors. In the present review, we critically discuss current knowledge regarding predictive biomarkers for checkpoint inhibitor-based immunotherapy, highlight the missing/unclear links and emphasise the importance of characterising each neoplasm and its microenvironment in order to better guide the course of treatment.

Combination strategies to maximize the benefits of cancer immunotherapy

Immunotherapies such as immune checkpoint blockade (ICB) and adoptive cell therapy (ACT) have revolutionized cancer treatment, especially in patients whose disease was otherwise considered incurable. However, primary and secondary resistance to single agent immunotherapy often results in treatment failure, and only a minority of patients experience long-term benefits. This review article will discuss the relationship between cancer immune response and mechanisms of resistance to immunotherapy. It will also provide a comprehensive review on the latest clinical status of combination therapies (e.g., immunotherapy with chemotherapy, radiation therapy and targeted therapy), and discuss combination therapies approved by the US Food and Drug Administration. It will provide an overview of therapies targeting cytokines and other soluble immunoregulatory factors, ACT, virotherapy, innate immune modifiers and cancer vaccines, as well as combination therapies that exploit alternative immune targets and other therapeutic modalities. Finally, this review will include the stimulating insights from the 2020 China Immuno-Oncology Workshop co-organized by the Chinese American Hematologist and Oncologist Network (CAHON), the China National Medical Product Administration (NMPA) and Tsinghua University School of Medicine.

B7-H5 blockade enhances CD8+ T-cell-mediated antitumor immunity in colorectal cancer

Negative immune checkpoint blockade immunotherapy has shown potential for multiple malignancies including colorectal cancer (CRC). B7-H5, a novel negative immune checkpoint regulator, is highly expressed in tumor tissues and promotes tumor immune escape. However, the clinical significance of B7-H5 expression in CRC and the role of B7-H5 in the tumor microenvironment (TME) has not been fully clarified. In this study, we observed that high B7-H5 expression in CRC tissues was significantly correlated with the lymph node involvement, AJCC stage, and survival of CRC patients. A significant inverse correlation was also observed between B7-H5 expression and CD8⁺ T-cell infiltration in CRC tissues. Kaplan-Meier analysis showed that patients with high B7-H5 expression and low CD8⁺ T-cell infiltration had the worst prognosis in our cohort of CRC patients. Remarkably, both high B7-H5 expression and low CD8⁺ T infiltration were risk factors for overall survival. Additionally, B7-H5 blockade using a B7-H5 monoclonal antibody (B7-H5 mAb) effectively suppressed the growth of MC38 colon cancer tumors by enhancing the infiltration and Granzyme B production of CD8⁺ T cells. Importantly, the depletion of CD8⁺ T cells obviously abolished the antitumor effect of B7-H5 blockade in the MC38 tumors. In sum, our findings suggest that B7-H5 may be a valuably prognostic marker for CRC and a potential target for CRC immunotherapy.

How to turn up the heat on the cold immune microenvironment of metastatic prostate cancer

BACKGROUND

Advanced prostate cancer remains one of the most common and deadly cancers, despite advances in treatment options. Immunotherapy has provided little benefit to a majority of patients, largely due to the immunosuppressive tumor microenvironment that gives rise to inherently "cold tumors". In this review, we discuss the immunopathology of the prostate tumor microenvironment, strategies for treating prostate cancer with immunotherapies, and a perspective on potential approaches to enhancing the efficacy of immunotherapies.

METHODS

Databases, including PubMed, Google Scholar, and Cochrane, were searched for articles relevant to the immunology of prostate cancer. We discuss the impact of different types of treatments on the immune system, and potential mechanisms through which prostate cancer evades the immune system.

RESULTS

The tumor microenvironment associated with prostate cancer is highly immunosuppressive due to (1) the function of regulatory T cells, tumor-associated macrophages, and myeloid-derived suppressor cells (MDSCs), (2) the cytokine milieu secreted by tumor stromal cells and fibroblasts, and (3) the production of adenosine via prostatic acid phosphatase. Both adenosine and tumor growth factor beta (TGF-beta) serve as potent immunosuppressive molecules that could also represent potential therapeutic targets. While there have been many immunotherapy trials in prostate cancer, the majority of these trials have targeted a single immunosuppressive mechanism resulting in limited clinical efficacy. Future approaches will require the integration of improved patient selection as well as use of combination therapies to address multiple mechanisms of resistance.

CONCLUSION

Prostate cancer inherently gives rise to multiple immunosuppressive mechanisms that have been difficult to overcome with any one immunotherapeutic approach. Enhancing the clinical activity of immunotherapies will require strategic combinations of multiple therapies to address the emerging mechanisms of tumor immune resistance.

Comprehensive analysis of alternative splicing profiling reveals novel events associated with prognosis and the infiltration of immune cells in prostate cancer

Background

Alternative splicing (AS) is believed to play a vital role in tumor development. Therefore, comprehensive investigation of AS and its biological function in prostate cancer (PCa) is crucial.

Methods

The AS profiling of 489 patients with PCa was obtained from The Cancer Genome Atlas (TCGA) SpliceSeq database. Bioinformatics tools were used to describe splicing associations and build prognostic models. Unsupervised clustering of the determined prognostic AS events and the relationship with immune characteristics were also explored.

Results

In total, 20,723 AS events were detected and 2,805 were identified in PCa. In the regulatory networks, the data suggested a significant correlation between splicing factor (SF) expression and AS events. To stratify the progression risk of PCa patients, prognostic models were constructed using splicing patterns. Six AS events were screened out as independent prognostic factors for progression-free survival. Based on the gene features, we constructed the combined prognostic predictors model, and the receiver operating characteristic (ROC) curve for this model reached a high area under the ROC curve (AUC) of 0.729793, indicating a favorable ability to predict patient outcomes. Through unsupervised clustering analysis, the correlations between AS-based clusters and prognosis as well as immune characteristics were revealed. The correlation analysis on TIMER revealed the relationship between gene expression and immune cell infiltration.

Conclusions

This in-depth genome-wide analysis of the AS profiling in PCa revealed unique AS events associated with cancer progression and the infiltration of immune cells, with potential for predicting outcomes and therapeutic responses.

Understanding the tumor-immune microenvironment in prostate cancer

PURPOSE OF REVIEW

This review aims to highlight recent advances in prostate cancer tumor-immune microenvironment research and summarize the state-of-the-art knowledge of immune checkpoint inhibitors in prostate cancer.

RECENT FINDINGS

Immune checkpoint inhibitors are the cornerstone of modern immunotherapy which have shown encouraging results across a spectrum of cancers. However, only limited survival benefit has been seen in patients with prostate cancer. Prostate cancer progression and its response to immunotherapies are strongly influenced by the tumor-immune microenvironment, whose feature can be summarized as low amounts of tumor-specific antigens, low frequency of tumor-infiltrating lymphocytes and high frequency of tumor-associated macrophages. To improve the therapeutic effect of immunotherapies, in recent years, many strategies have been applied, of which the most promising ones include the combination of multiple immunotherapeutic agents, the combination of an immunotherapeutic agent with other modalities in parallel or in sequential, and the development of biomarkers to find a subgroup of patients who may benefit the most from immunotherapeutic agents.

SUMMARY

The impact of immune content and specific immune cell types on prostate cancer biology is highly complex. Recent clinical trials have shed light on the optimal use of immunotherapies for prostate cancer.

Immune functions as a ligand or a receptor, cancer prognosis potential, clinical implication of VISTA in cancer immunotherapy

Since cancer immunotherapy with immune checkpoint inhibitors of PD/PDL-1 and CTLA-4 limited efficacy to the patients due to resistance during the current decade, novel target is required for customized treatment due to tumor heterogeneity. V-domain Ig-containing suppressor of T cell activation (VISTA), a programmed death protein-1(PD-1) homolog expressed on T cells and on antigen presenting cells(APC), has emerged as a new target in several cancers. Though VISTA inhibitors including CA-170 are considered attractive in cancer immunotherapy to date, the information on VISTA as a potent biomarker of cancer prognosis and its combination therapy is still lacking to date. Thus, in this review, we discussed extracellular domain, ligands, expression, immune functions and clinical implications of VISTA and finally suggested conclusion and perspectives.

VISTA facilitates phagocytic clearance of HIV infected CEM-SS T cells

Phagocytosis is a critical component of the innate immune response to viral infection, resulting in the clearance of infected cells while minimizing the exposure of uninfected cells. On the other hand, phagocytosis of HIV-infected T cells may cause phagocytes, such as macrophages and dendritic cells, to be infected, thus leading to HIV cell-to-cell transmission. V domain immunoglobulin suppressor of T cell activation (VISTA, gene Vsir, aliases Gi24, Dies-1, PD-1H, and DD1α) has been identified as an immune checkpoint molecule that possesses dual activities when expressed on APCs and T cells. Our study found that VISTA might play a significant role during the immune response to HIV infection via apoptosis upregulation and subsequent phagocytosis of infected CEM-SS T cells. HIV-induced apoptosis and monocytic cell engulfment were tested utilizing CEM-SS T cells as target cells and the monocytic cell line THP-1 as phagocytic cells. Cells were infected with a GFP-labeled HIV strain, NL4-3. HIV-infected CEM-SS T cells displayed greater apoptotic activity (approximately 18.0%) than mock-infected controls. Additionally, phagocytosis of HIV-infected CEM-SS T cells was increased approximately 4-fold. Expression of VISTA on infected CEM-SS T cells was detected in 16.7% of cells, which correlated with the increased phagocytosis observed. When an antagonistic antibody against VISTA was used, the number of phagocytosed cells was reduced by a factor of 2, which was replicated utilizing human stem cell-derived dendritic cells. Phagocytosis was also confirmed by the upregulation of IL-1β expression, which was 5-fold higher in infected cells than in control cells. We also found that VISTA overexpression on both phagocytes and HIV-infected CEM-SS T cells facilitated phagocytosis. Our study suggests that VISTA may act as a direct ligand in the phagocytosis of HIV-infected T cells.

Pilot Phase II Trial of Neoadjuvant Immunotherapy in Locoregionally Advanced, Resectable Cutaneous Squamous Cell Carcinoma of the Head and Neck

PURPOSE

In locoregionally advanced, resectable cutaneous squamous cell carcinoma of the head and neck (CSCC-HN), surgery followed by radiotherapy is standard but can be cosmetically and functionally devastating, and many patients will have recurrence.

PATIENTS AND METHODS

Newly diagnosed or recurrent stage III-IVA CSCC-HN patients amenable to curative-intent surgery received two cycles of neoadjuvant PD-1 inhibition. The primary endpoint was ORR per RECIST 1.1. Secondary endpoints included pathologic response [pathologic complete response (pCR) or major pathologic response (MPR; ≤10% viable tumor)], safety, DSS, DFS, and OS. Exploratory endpoints included immune biomarkers of response.

RESULTS

Of 20 patients enrolled, 7 had recurrent disease. While only 6 patients [30%; 95% confidence interval (CI), 11.9-54.3] had partial responses by RECIST, 14 patients (70%; 95% CI, 45.7-88.1) had a pCR (n = 11) or MPR (n = 3). No SAEs ocurred during or after the neoadjuvant treatment. At a median follow-up of 22.6 months (95% CI, 21.7-26.1), one patient progressed and died, one died without disease, and two developed recurrence. The 12-month DSS, DFS, and OS rates were 95% (95% CI, 85.9-100), 89.5% (95% CI, 76.7-100), and 95% (95% CI, 85.9-100), respectively. Gene expression studies revealed an inflamed tumor microenvironment in patients with pCR or MPR, and CyTOF analyses demonstrated a memory CD8+ T-cell cluster enriched in patients with pCR.

CONCLUSIONS

Neoadjuvant immunotherapy in locoregionally advanced, resectable CSCC-HN is safe and induces a high pathologic response rate. Pathologic responses were associated with an inflamed tumor microenvironment.

Identification of active small-molecule modulators targeting the novel immune checkpoint VISTA

Background

Cancer immunotherapy has gained increasing popularity as a novel approach to treat cancer. A member of the B7 family, V-domain immunoglobulin suppressor of T-cell activation (VISTA) is a novel immune checkpoint that regulates a broad spectrum of immune responses. VISTA is an acidic pH-selective ligand for P-selectin glycoprotein ligand-1(PSGL-1). CA-170, a first-in-class small-molecule dual antagonist of VISTA/PD-L1, was collaboratively developed by Aurigene Discovery Technologies Limited and Curis, Inc. It is currently in Phase I clinical trial.

Results

In this study, we develop homology modeling for the VISTA 3D structure and subsequent virtual screening for VISTA small-molecule hit ligands. Visualization of the binding postures of docked ligands with the VISTA protein indicates that some small molecular compounds target VISTA. The ability of antagonist to disrupt immune checkpoint VISTA pathways was investigated though functional studies in vitro.

Conclusions

Affinity active molecule for VISTA was obtained through virtual screening, and the antagonist compound activity to VISTA was assayed in cellular level. We reported a small molecule with high VISTA affinity as antagonist, providing ideas for development VISTA-targeted small molecule compound in cancer immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-021-00446-4.

Castration-mediated IL-8 promotes myeloid infiltration and prostate cancer progression

Unlike several other tumor types, prostate cancer rarely responds to immune checkpoint blockade (ICB). To define tumor cell intrinsic factors that contribute to prostate cancer progression and resistance to ICB, we analyzed prostate cancer epithelial cells from castration-sensitive and -resistant samples using implanted tumors, cell lines, transgenic models and human tissue. We found that castration resulted in increased expression of interleukin-8 (IL-8) and its probable murine homolog Cxcl15 in prostate epithelial cells. We showed that these chemokines drove subsequent intratumoral infiltration of tumor-promoting polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs), which was largely abrogated when IL-8 signaling was blocked genetically or pharmacologically. Targeting IL-8 signaling in combination with ICB delayed the onset of castration resistance and increased the density of polyfunctional CD8 T cells in tumors. Our findings establish a novel mechanism by which castration mediates IL-8 secretion and subsequent PMN-MDSC infiltration, and highlight blockade of the IL-8/CXCR2 axis as a potential therapeutic intervention.

DCision-making in tumors governs T cell anti-tumor immunity

The exploitation of T cell-based immunotherapies and immune checkpoint blockade for cancer treatment has dramatically shifted oncological treatment paradigms and broadened the horizons of cancer immunology. Dendritic cells have emerged as the critical tailors of T cell immune responses, which initiate and coordinate anti-tumor immunity. Importantly, genetic alterations in cancer cells, cytokines and chemokines produced by cancer and stromal cells, and the process of tumor microenvironmental regulation can compromise dendritic cell-T cell cross-talk, thereby disrupting anti-tumor T cell responses. This review summarizes how T cell activation is controlled by dendritic cells and how the tumor microenvironment alters dendritic cell properties in the context of the anti-tumor immune cycle. Furthermore, we will highlight therapeutic options for tailoring dendritic cell-mediated decision-making in T cells for cancer treatment.

Clinical Research on the Mechanisms Underlying Immune Checkpoints and Tumor Metastasis

This study highlights aspects of the latest clinical research conducted on the relationship between immune checkpoints and tumor metastasis. The overview of each immune checkpoint is divided into the following three sections: 1) structure and expression; 2) immune mechanism related to tumor metastasis; and 3) clinical research related to tumor metastasis. This review expands on the immunological mechanisms of 17 immune checkpoints, including TIM-3, CD47, and OX-40L, that mediate tumor metastasis; evidence shows that most of these immune checkpoints are expressed on the surface of T cells, which mainly exert immunomodulatory effects. Additionally, we have summarized the roles of these immune checkpoints in the diagnosis and treatment of metastatic tumors, as these checkpoints are considered common predictors of metastasis in various cancers such as prostate cancer, non-Hodgkin lymphoma, and melanoma. Moreover, certain immune checkpoints can be used in synergy with PD-1 and CTLA-4, along with the implementation of combination therapies such as LIGHT-VTR and anti-PD-1 antibodies. Presently, most monoclonal antibodies generated against immune checkpoints are under investigation as part of ongoing preclinical or clinical trials conducted to evaluate their efficacy and safety to establish a better combination treatment strategy; however, no significant progress has been made regarding monoclonal antibody targeting of CD28, VISTA, or VTCN1. The application of immune checkpoint inhibitors in early stage tumors to prevent tumor metastasis warrants further evidence; the immune-related adverse events should be considered before combination therapy. This review aims to elucidate the mechanisms of immune checkpoint and the clinical progress on their use in metastatic tumors reported over the last 5 years, which may provide insights into the development of novel therapeutic strategies that will assist with the utilization of various immune checkpoint inhibitors.

New emerging targets in cancer immunotherapy: the role of VISTA

The immune surveillance system is complex and regulated by different actors. Programmed death protein-ligand 1 (PD-L1), the only approved biomarker in clinical practice, has proven to be imperfect in selecting patients to immune checkpoint inhibitors treatment. Therefore, new biomarkers, and new therapeutic targets, are needed to maximise the efficacy of immunotherapy. V-domain Ig Suppressor of T-cell Activation (VISTA) is a programmed death protein-1 (PD-1) homolog expressed on T cells and on antigen-presenting cells, which regulates processes of activation and repression of the immune system with not yet completely clarified mechanisms. Its blockage has demonstrated in vitro and in vivo antitumour activity. The clinical research of VISTA antagonists is ongoing. Particularly, CA-170, an orally delivered dual inhibitor of VISTA and PD-L1, has shown to have clinical efficacy in phase I and II clinical trials in different advanced solid tumour types. Further data are needed to define whether this drug class can become a new therapeutic option for patients with VISTA expressing cancers.

The Role of Mathematical Models in Immuno-Oncology: Challenges and Future Perspectives

Immuno-oncology (IO) focuses on the ability of the immune system to detect and eliminate cancer cells. Since the approval of the first immune checkpoint inhibitor, immunotherapies have become a major player in oncology treatment and, in 2021, represented the highest number of approved drugs in the field. In spite of this, there is still a fraction of patients that do not respond to these therapies and develop resistance mechanisms. In this sense, mathematical models offer an opportunity to identify predictive biomarkers, optimal dosing schedules and rational combinations to maximize clinical response. This work aims to outline the main therapeutic targets in IO and to provide a description of the different mathematical approaches (top-down, middle-out, and bottom-up) integrating the cancer immunity cycle with immunotherapeutic agents in clinical scenarios. Among the different strategies, middle-out models, which combine both theoretical and evidence-based description of tumor growth and immunological cell-type dynamics, represent an optimal framework to evaluate new IO strategies.