CD155 expression in human breast cancer: Clinical significance and relevance to natural killer cell infiltration

The Nectin family ligands, PVRL2 and PVR, in cancer immunology and immunotherapy

In recent years, immunotherapy has emerged as a crucial component of cancer treatment. However, its efficacy remains limited across various cancer types, highlighting unmet needs. Poliovirus receptor-related 2 (PVRL2) and Poliovirus receptor (PVR) are members of the Nectin and Nectin-like Molecules family, known for their role as cell-cell adhesion molecules. With the development of immunotherapy, their involvement in tumor immune mechanisms as immune checkpoint factors has garnered significant attention. PVRL2 and PVR are predominantly expressed on tumor cells and antigen-presenting cells, binding to PVRIG and TIGIT, respectively, which are primarily found on T and NK cells, thereby suppressing antitumor immunity. Notably, gynecological cancers such as ovarian and endometrial cancers exhibit high expression levels of PVRL2 and PVR, with similar trends observed in various other solid and hematologic tumors. Targeting these immune checkpoint pathways offers a promising therapeutic avenue, potentially in combination with existing treatments. However, the immunomodulatory mechanism involving these bindings, known as the DNAM-1 axis, is complex, underscoring the importance of understanding it for developing novel therapies. This article comprehensively reviews the immunomodulatory mechanisms centered on PVRL2 and PVR, elucidating their implications for various cancer types.

sCD155 as a potential marker for diagnosing the vascular invasion in hepatic alveolar echinococcosis

BACKGROUND

Alveolar Echinococcosis (AE) is a malignant zoonotic disease caused by Echinococcus multilocularis infection. Considering whether the lesion is accompanied by vascular invasion (VI) is crucial for treatment strategies. A cost-effective and convenient clinical diagnostic method is urgently needed to supplement current techniques. Consequently, we detected soluble CD155 (sCD155) as a potential biomarker for diagnosing VI in hepatic alveolar echinococcosis (HAE).

METHODS

Blood samples were from 42 AE patients and 49 healthy controls (HCs). Based on the computed tomography (CT) and contrast-enhanced CT, AE patients were further categorized into HAE with VI (VIAE; 27 cases) and HAE without VI (NVAE; 15 cases). The sCD155 concentration was measured by an enzyme-linked immunosorbent assay (ELISA). Correlations between sCD155 expression levels and clinicopathological features of AE patients were analyzed using SPSS and GraphPad Prism software.

RESULTS

The sCD155 concentrations in AE patients were significantly higher than in HCs. The serum sCD155 level significantly differed between the VIAE and NVAE groups. The univariate analysis showed that VI of AE was significantly correlated with the sCD155 level when the sCD155 was greater than 11 ng/mL. After adjusting for potential confounding factors, the multivariable analysis showed that sCD155 had an independent effect on VI of HAE. The receiver operating characteristic (ROC) curve showed that sCD155 could differentially diagnose VI of HAE at the cut-off value of 11.08 ng/mL with an area under the curve (AUC) value of 0.75. The sensitivity and specificity were 74.07 % and 66.67 %, respectively; the positive and negative predictive values were 74.07 % and 60.00 %, respectively.

CONCLUSION

The sCD155 could be a VI biomarker for HAE. Elevated sCD155 levels are indicative of an increased likelihood of concomitant VI in HAE patients, necessitating a thorough evaluation of vascular impairment and the formulation of individualized management strategies.

Breast Cancer Immune Landscape: Interplay Between Systemic and Local Immunity

Breast cancer (BC) is one of the most common malignancies in women worldwide. Numerous studies in immuno-oncology and successful trials of immunotherapy have demonstrated the causal role of the immune system in cancer pathogenesis. The interaction between the tumor and the immune system is known to have a dual nature. Despite cytotoxic lymphocyte activity against transformed cells, a tumor can escape immune surveillance and leverage chronic inflammation to maintain its own development. Research on antitumor immunity primarily focuses on the role of the tumor microenvironment, whereas the systemic immune response beyond the tumor site is described less thoroughly. Here, a comprehensive review of the formation of the immune profile in breast cancer patients is offered. The interplay between systemic and local immune reactions as self-sustaining mechanism of tumor progression is described and the functional activity of the main cell populations related to innate and adaptive immunity is discussed. Additionally, the interaction between different functional levels of the immune system and their contribution to the development of the pro- or anti-tumor immune response in BC is highlighted. The presented data can potentially inform the development of new immunotherapy strategies in the treatment of patients with BC.

CD155 as an emerging target in tumor immunotherapy

CD155 is an immunoglobulin-like protein overexpressed in almost all the tumor cells, which not only promotes proliferation, adhesion, invasion, and migration of tumor cells, but also regulates immune responses by interacting with TIGIT, CD226 or CD96 receptors expressed on several immune cells, thereby modulating the functionality of these cellular subsets. As a novel immune checkpoint, the inhibition of CD155/TIGIT, either as a standalone treatment or in conjunction with other immune checkpoint inhibitors, has demonstrated efficacy in managing advanced solid malignancies. In this review, we summarize the intricate relationship between on tumor surface CD155 and its receptors, with further discussion on how they regulate the occurrence of tumor immune escape. In addition, novel therapeutic strategies and clinical trials targeting CD155 and its receptors are summarized, providing a strong rationale and way forward for the development of next-generation immunotherapies.

Pan-inhibition of the three H2S synthesizing enzymes restrains tumor progression and immunosuppression in breast cancer

BACKGROUND

Hydrogen sulfide (H2S) is a significant endogenous mediator that has been implicated in the progression of various forms of cancer including breast cancer (BC). Cystathionine-β-synthase (CBS), cystathionine-γ-lyase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST) are the three principal mammalian enzymes responsible for H2S production. Overexpression of CBS, CSE and 3MST was found to be associated with poor prognosis of BC patients. Moreover, H2S was linked to an immune-suppressive tumor microenvironment in BC. Recently it was observed that BC cells, in response to single or dual inhibition of H2S synthesizing enzymes, develop an escape mechanism by overexpressing alternative sources of H2S generation. Thus, the aim of this work is to escape the H2S compensatory mechanism by pan repressing the three enzymes using microRNAs (miRNAs) and to investigate their impact on the oncogenic and immunogenic profile of BC cells.

METHODS

BC female patients (n = 25) were recruited. In-silico analysis was used to identify miRNAs targeting CBS, CSE, and 3MST. MDA-MB-231 cells were cultured and transfected using oligonucleotides. Total RNA was extracted using Biazol, reverse transcribed and quantified using qRT-PCR. H2S levels were measured using AzMc assay. BC hallmarks were assessed using trans-well migration, wound healing, MTT, and colony forming assays.

RESULTS

miR-193a and miR-548c were validated by eight different bioinformatics software to simultaneously target CBS, CSE and 3MST. MiR-193a and miR-548c were significantly downregulated in BC tissues compared to their non-cancerous counterparts. Ectopic expression of miR-193a and miR-548c in MDA-MB-231 TNBC cells resulted in a marked repression of CBS, CSE, and 3MST transcript and protein levels, a significant decrease in H2S levels, reduction in cellular viability, inhibition of migration and colony forming ability, repression of immune-suppressor proteins GAL3 GAL9, and CD155 and upregulation of the immunostimulatory MICA and MICB proteins.

CONCLUSION

This study sheds the light onto miR-193a and miR-548c as potential pan-repressors of the H2S synthesizing enzymes. and identifies them as novel tumor suppressor and immunomodulatory miRNAs in TNBC.

Poliovirus receptor-based chimeric antigen receptor T cells combined with NK-92 cells exert potent activity against glioblastoma

BACKGROUND

Poliovirus receptor interacts with 3 receptors: T-cell immunoglobulin immunoreceptor tyrosine-based inhibitory motif, CD96, and DNAX accessory molecule 1, which are predominantly expressed on T cells and natural killer (NK) cells. Many solid tumors, including IDH wild-type glioblastoma, have been reported to overexpress poliovirus receptor, and this overexpression is associated with poor prognosis. However, there are no preclinical or clinical trials investigating the use of cell-based immunotherapies targeting poliovirus receptor in IDH wild-type glioblastoma.

METHODS

We analyzed poliovirus receptor expression in transcriptome sequencing databases and specimens from IDH wild-type glioblastoma patients. We developed poliovirus receptor targeting chimeric antigen receptor T cells using lentivirus. The antitumor activity of chimeric antigen receptor T cells was demonstrated in patient-derived glioma stem cells, intracranial and subcutaneous mouse xenograft models.

RESULTS

We verified poliovirus receptor expression in primary glioma stem cells, surgical specimens from IDH wild-type glioblastoma patients, and organoids. Accordingly, we developed poliovirus receptor-based second-generation chimeric antigen receptor T cells. The antitumor activity of chimeric antigen receptor T cells was demonstrated in glioma stem cells and xenograft models. Tumor recurrence occurred in intracranial xenograft models because of antigen loss. The combinational therapy of tyrosine-based inhibitory motif extracellular domain-based chimeric antigen receptor T cells and NK-92 cells markedly suppressed tumor recurrence and prolonged survival.

CONCLUSIONS

Poliovirus receptor-based chimeric antigen receptor T cells were capable of killing glioma stem cells and suppressing tumor recurrence when combined with NK-92 cells.

The breast cancer tumor microenvironment and precision medicine: immunogenicity and conditions favoring response to immunotherapy

Some main recent researches that have dissected tumor microenvironment (TME) by imaging mass cytometry (IMC) in different subtypes of primary breast cancer samples were considered. The many phenotypic variants, clusters of epithelial tumor and immune cells, their structural features as well as the main genetic aberrations, sub-clonal heterogeneity and their systematic classification also have been examined. Mutational evolution has been assessed in primary and metastatic breast cancer samples. Overall, based on these findings the current concept of precision medicine is questioned and challenged by alternative therapeutic strategies. In the last two decades, immunotherapy as a powerful and harmless tool to fight cancer has received huge attention. Thus, the tumor immune microenvironment (TIME) composition, its prognostic role for clinical course as well as a novel definition of immunogenicity in breast cancer are proposed. Investigational clinical trials carried out by us and other findings suggest that G0-G1 state induced in endocrine-dependent metastatic breast cancer is more suitable for successful immune manipulation. Residual micro-metastatic disease seems to be another specific condition that can significantly favor the immune response in breast and other solid tumors.

Unveiling the Immune Microenvironment's Role in Breast Cancer: A Glimpse into Promising Frontiers

Breast cancer (BC), one of the most widespread and devastating diseases affecting women worldwide, presents a significant public health challenge. This review explores the emerging frontiers of research focused on deciphering the intricate interplay between BC cells and the immune microenvironment. Understanding the role of the immune system in BC is critical as it holds promise for novel therapeutic approaches and precision medicine strategies. This review delves into the current literature regarding the immune microenvironment's contribution to BC initiation, progression, and metastasis. It examines the complex mechanisms by which BC cells interact with various immune cell populations, including tumor-infiltrating lymphocytes (TILs) and tumor-associated macrophages (TAMs). Furthermore, this review highlights the impact of immune-related factors, such as cytokines and immune checkpoint molecules. Additionally, this comprehensive analysis sheds light on the potential biomarkers associated with the immune response in BC, enabling early diagnosis and prognostic assessment. The therapeutic implications of targeting the immune microenvironment are also explored, encompassing immunotherapeutic strategies and combination therapies to enhance treatment efficacy. The significance of this review lies in its potential to pave the way for novel therapeutic interventions, providing clinicians and researchers with essential knowledge to design targeted and personalized treatment regimens for BC patients.

Remodeled tumor immune microenvironment (TIME) parade via natural killer cells reprogramming in breast cancer

Breast cancer (BC) is the main cause of cancer-related mortality among women globally. Despite substantial advances in the identification and management of primary tumors, traditional therapies including surgery, chemotherapy, and radiation cannot completely eliminate the danger of relapse and metastatic illness. Metastasis is controlled by microenvironmental and systemic mechanisms, including immunosurveillance. This led to the evolvement of immunotherapies that has gained much attention in the recent years for cancer treatment directed to the innate immune system. The long forgotten innate immune cells known as natural killer (NK) cells have emerged as novel targets for more effective therapeutics for BC. Normally, NK cells has the capacity to identify and eradicate tumor cells either directly or by releasing cytotoxic granules, chemokines and proinflammatory cytokines. Yet, NK cells are exposed to inhibitory signals by cancer cells, which causes them to become dysfunctional in the immunosuppressive tumor microenvironment (TME) in BC, supporting tumor escape and spread. Potential mechanisms of NK cell dysfunction in BC metastasis have been recently identified. Understanding these immunologic pathways driving BC metastasis will lead to improvements in the current immunotherapeutic strategies. In the current review, we highlight how BC evades immunosurveillance by rendering NK cells dysfunctional and we shed the light on novel NK cell- directed therapies.

CD155 and its receptors in cancer immune escape and immunotherapy

In recent years, there have been multiple breakthroughs in cancer immunotherapy, with immune checkpoint inhibitors becoming the most promising treatment strategy. However, available drugs are not always effective. As an emerging immune checkpoint molecule, CD155 has become an important target for immunotherapy. This review describes the structure and function of CD155, its receptors TIGIT, CD96, and CD226, and summarizes that CD155 expressed by tumor cells can upregulate its expression through the DNA damage response pathway and Ras-Raf-MEK-ERK signaling pathway. This review also elaborates the mechanism of immune escape after binding CD155 to its receptors TIGIT, CD96, and CD226, and summarizes the current progress of immunotherapy research regarding CD155 and its receptors. Besides, it also discusses the future direction of checkpoint immunotherapy.

Diverging prognostic effects of CD155 and CD73 expressions in locally advanced triple-negative breast cancer

Background

Immune checkpoint inhibition, combined with novel biomarkers, may provide alternative pathways for treating chemotherapy-resistant triple-negative breast cancer (TNBC). This study investigates the expression of new immune checkpoint receptors, including CD155 and CD73, which play a role in T and natural killer (NK) cell activities, in patients with residual TNBC after neoadjuvant chemotherapy (NAC).

Methods

The expression of biomarkers was immunohistochemically examined by staining archival tissue from surgical specimens (n = 53) using specific monoclonal antibodies for PD-L1, CD155, and CD73.

Results

Of those, 59.2% (29/49) were found to be positive (>1%) for PD-L1 on the tumour and tumour-infiltrating lymphocytes (TILs), while CD155 (30/53, 56.6%) and CD73 (24/53, 45.3%) were detected on tumours. Tumour expressions of CD155 and CD73 significantly correlated with PD-L1 expression on the tumour (p = 0.004 for CD155, p = 0.001 for CD73). Patients with CD155 positivity ≥10% were more likely to have a poor chemotherapy response, as evidenced by higher MDACC Residual Cancer Burden Index scores and Class II/III than those without CD155 expression (100% vs 82.6%, p = 0.03). At a median follow-up time of 80 months (range, 24-239), patients with high CD73 expression showed improved 10-year disease-free survival (DFS) and disease-specific survival (DSS) rates compared to those with low CD73 expression. In contrast, patients with CD155 (≥10%) expression exhibited a decreasing trend in 10-year DFS and DSS compared to cases with lower expression, although statistical significance was not reached. However, patients with coexpression of CD155 (≥10%) and low CD73 were significantly more likely to have decreased 10-year DFS and DSS rates compared to others (p = 0.005).

Conclusion

These results demonstrate high expression of CD73 and CD155 in patients with residual tumours following NAC. CD155 expression was associated with a poor response to NAC and poor prognosis in this chemotherapy-resistant TNBC cohort, supporting the use of additional immune checkpoint receptor inhibitor therapy. Interestingly, the interaction between CD155 and CD73 at lower levels resulted in a worse outcome than either marker alone, which calls for further investigation in future studies.

CD8+ CD226high T cells in liver metastases dictate the prognosis of colorectal cancer patients treated with chemotherapy and radical surgery

CD226 has been reported to participate in the rescue of CD8+ T cell dysfunction. In this study, we aimed to assess the prognostic value of CD226 in tumor-infiltrating lymphocytes (TILs) derived from colorectal cancer (CRC) liver metastases treated with chemotherapy and radical surgery. TILs from 43 metastases were isolated and analyzed ex vivo using flow cytometry. CD155 and CD3 levels in the tumor microenvironment were assessed by immunohistochemistry. Exploration and validation of biological processes highlighted in this study were performed by bioinformatics analysis of bulk RNA-seq results for 28 CRC liver metastases pretreated with chemotherapy as well as public gene expression datasets. CD226 expression contributes to the definition of the immune context in CRC liver metastases and primary tumors. CD226 on CD8+ T cells was not specifically coexpressed with other immune checkpoints, such as PD1, TIGIT, and TIM3, in liver metastases. Multivariate Cox regression analysis revealed CD226 expression on CD8+ T cells to be an independent prognostic factor (p = 0.003), along with CD3 density at invasion margins (p = 0.003) and TIGIT expression on CD4+ T cells (p = 0.019). CD155 was not associated with the prognostic value of CD226. Gene expression analysis in a validation dataset confirmed the prognostic value of CD226 in CRC liver metastases but not in primary tumors. Downregulation of CD226 on CD8+ TILs in the liver microenvironment was restored by IL15 treatment. Overall, CD226 expression on liver metastasis-infiltrating CD8+ T cells selectively contributes to immune surveillance of CRC liver metastases and has prognostic value for patients undergoing radical surgery.

Immunohistochemical expression of CD155 in invasive female breast carcinoma and its correlation with tumor infiltrating natural killer cells

Background

CD155 is an immune checkpoint protein that interacts with ligands on natural killer cells to regulate the tumor associated immunity. CD155 overexpression has been detected in many human cancer types. CD155 and its pathways are promising tumor immunotherapy targets. We aimed to evaluate the immunohistochemical expression of CD155 in invasive breast carcinomas and to correlate such expression with the pathological parameters of the tumors and also with natural killer - tumor infiltrating lymphocytes (NK-TILs) density in breast carcinomas tissue as highlighted by CD56 immunostaining. This study included 78 cases of breast carcinomas. Immunohistochemistry was performed using antibodies against CD155 which was detected on the tumor cells and CD56 as a marker for stromal NK cells.

Results

CD155 expression by the tumor cells was detected in 30.8% of the cases and correlated significantly with advanced prognostic stage, Estrogen receptor (ER) and Progesterone receptor (PR) negativity, high Ki-67 index and Human epidermal receptor 2 (HER2) enriched molecular subtype. High stromal TILs CD56 expression was detected in 28.2% of the cases and correlated significantly with high histologic grade, PR negativity, HER2 neu over-expression, high Ki-67 index, high stromal TILs and more aggressive molecular subtypes; triple negative breast cancer, HER2 enriched and Luminal B-HER2 positive. Finally, statistically significant direct correlation was detected between Tumor cells CD155 expression and high TILs CD56 expression.

Conclusions

Our results support tumor cell CD155 expression and TILs CD56 expression in breast cancers that are high grade, TILs rich and hormone receptors negative, highlighting those cases as possible candidates for CD155 targeted therapy.

T cell-derived interleukin-22 drives the expression of CD155 by cancer cells to suppress NK cell function and promote metastasis

Although T cells can exert potent anti-tumor immunity, a subset of T helper (Th) cells producing interleukin-22 (IL-22) in breast and lung tumors is linked to dismal patient outcome. Here, we examined the mechanisms whereby these T cells contribute to disease. In murine models of lung and breast cancer, constitutional and T cell-specific deletion of Il22 reduced metastases without affecting primary tumor growth. Deletion of the IL-22 receptor on cancer cells decreases metastasis to a degree similar to that seen in IL-22-deficient mice. IL-22 induced high expression of CD155, which bound to the activating receptor CD226 on NK cells. Excessive activation led to decreased amounts of CD226 and functionally impaired NK cells, which elevated the metastatic burden. IL-22 signaling was also associated with CD155 expression in human datasets and with poor patient outcomes. Taken together, our findings reveal an immunosuppressive circuit activated by T cell-derived IL-22 that promotes lung metastasis.

Tiragolumab (Anti-TIGIT) in SCLC: Skyscraper-02, a Towering Inferno

Small cell lung cancer (SCLC) is characterized by rapid progression and poor prognosis. Although the phase II CITYSCAPE-02 trial found objective response rate (ORR) and progression-free survival (PFS) of non-small cell lung cancer (NSCLC) patients improved when tiragolumab was added to atezolizumab and chemotherapy, the phase III SKYSCRAPER-02 failed to find PFS or OS benefit in patients with SCLC. Atezolizumab was the first immunotherapy to show survival benefit in extensive SCLC based on the phase III IMpower133 study. Given that immunotherapy has become the standard of care for SCLC patients, further research is needed into ways to augment the immune system to better treat these patients.

Blockade of the immunosuppressive KIR2DL5/PVR pathway elicits potent human NK cell-mediated antitumor immunity

Cancer immunotherapy targeting the TIGIT/PVR pathway is currently facing challenges. KIR2DL5, a member of the human killer cell, immunoglobulin-like receptor (KIR) family, has recently been identified as another binding partner for PVR. The biology and therapeutic potential of the KIR2DL5/PVR pathway are largely unknown. Here we report that KIR2DL5 was predominantly expressed on human NK cells with mature phenotype and cytolytic function and that it bound to PVR without competition with the other 3 known PVR receptors. The interaction between KIR2DL5 on NK cells and PVR on target cells induced inhibitory synapse formation, whereas new monoclonal antibodies blocking the KIR2DL5-PVR interaction robustly augmented the NK cytotoxicity against PVR+ human tumors. Mechanistically, both intracellular ITIM and ITSM of KIR2DL5 underwent tyrosine phosphorylation after engagement, which was essential for KIR2DL5-mediated NK suppression by recruiting SHP-1 and/or SHP-2. Subsequently, ITIM/SHP-1/SHP-2 and ITSM/SHP-1 downregulated the downstream Vav1/ERK1/2/p90RSK/NF-κB signaling. KIR2DL5+ immune cells infiltrated in various types of PVR+ human cancers. Markedly, the KIR2DL5 blockade reduced tumor growth and improved overall survival across multiple NK cell-based humanized tumor models. Thus, our results revealed functional mechanisms of KIR2DL5-mediated NK cell immune evasion, demonstrated blockade of the KIR2DL5/PVR axis as a therapy for human cancers, and provided an underlying mechanism for the clinical failure of anti-TIGIT therapies.

Prognostic and clinicopathological significance of CD155 expression in cancer patients: a meta-analysis

Background

It has been previously reported that CD155 is often over-expressed in a variety of cancer types. In fact, it is known to be involved in cancer development, and its role in cancer has been widely established. However, clinical and mechanistic studies involving CD155 yielded conflicting results. Thus, the present study aimed to evaluate overall prognostic value of CD155 in cancer patients, using a comprehensive analysis.

Methods

Online databases were searched, data was collected, and clinical value of CD155 was evaluated by combining hazard ratios (HRs) or odds ratios (ORs).

Results

The present study involved meta-analysis of 26 previous studies that involved 4325 cancer patients. These studies were obtained from 25 research articles. The results of the study revealed that increased CD155 expression was significantly associated with reduced OS in patients with cancer as compared to low CD155 expression (pooled HR = 1.772, 95% CI = 1.441–2.178, P < 0.001). Furthermore, subgroup analysis demonstrated that the level of CD155 expression was significantly associated with OS in patients with digestive system cancer (pooled HR = 1.570, 95% CI = 1.120–2.201, P = 0.009), hepatobiliary pancreatic cancer (pooled HR = 1.677, 95% CI = 1.037–2.712, P = 0.035), digestive tract cancer (pooled HR = 1.512, 95% CI = 1.016–2.250, P = 0.042), breast cancer (pooled HR = 2.137, 95% CI = 1.448–3.154, P < 0.001), lung cancer (pooled HR = 1.706, 95% CI = 1.193–2.440, P = 0.003), head and neck cancer (pooled HR = 1.470, 95% CI = 1.160–1.862, P = 0.001). Additionally, a significant correlation was observed between enhanced CD155 expression and advanced tumor stage (pooled OR = 1.697, 95% CI = 1.217–2.366, P = 0.002), LN metastasis (pooled OR = 1.953, 95% CI = 1.253–3.046, P = 0.003), and distant metastasis (pooled OR = 2.253, 95% CI = 1.235–4.110, P = 0.008).

Conclusion

Altogether, the results of the present study revealed that CD155 acted as an independent marker of prognosis in cancer patients, and it could provide a new and strong direction for cancer treatment.

Tumor-infiltrating lymphocytes for treatment of solid tumors: It takes two to tango?

Tumor-infiltrating lymphocytes (TILs), frontline soldiers of the adaptive immune system, are recruited into the tumor site to fight against tumors. However, their small number and reduced activity limit their ability to overcome the tumor. Enhancement of TILs number and activity against tumors has been of interest for a long time. A lack of knowledge about the tumor microenvironment (TME) has limited success in primary TIL therapies. Although the advent of engineered T cells has revolutionized the immunotherapy methods of hematologic cancers, the heterogeneity of solid tumors warrants the application of TILs with a wide range of specificity. Recent advances in understanding TME, immune exhaustion, and immune checkpoints have paved the way for TIL therapy regimens. Nowadays, TIL therapy has regained attention as a safe personalized immunotherapy, and currently, several clinical trials are evaluating the efficacy of TIL therapy in patients who have failed conventional immunotherapies. Gaining favorable outcomes following TIL therapy of patients with metastatic melanoma, cervical cancer, ovarian cancer, and breast cancer has raised hope in patients with refractory solid tumors, too. Nevertheless, TIL therapy procedures face several challenges, such as high cost, timely expansion, and technical challenges in selecting and activating the cells. Herein, we reviewed the recent advances in the TIL therapy of solid tumors and discussed the challenges and perspectives.

The role of the natural killer (NK) cell modulation in breast cancer incidence and progress

The importance of the immune system on tumor surveillance has been investigated for many years, and its impact on controlling tumor progression has been verified. An important subgroup of the innate immune system is natural killer (NK) cells, whose essential function in modulating tumor behavior and suppressing metastasis and tumor growth has been demonstrated. The first idea of NK cells' crucial biological processes was demonstrated through their potent ability to conduct direct cellular cytotoxicity, even without former sensitization. These properties of NK cells allow them to recognize transformed cells that have attenuated self-ligand and express stress-induced ligands. Furthermore, secretion of various cytokines and chemokines after their activation leads to tumor elimination via either direct cytotoxic effect on malignant cells or activation of the adaptive immune system. In addition, novel immunotherapeutic approaches tend to take advantage of NK cells' ability, leading to antibody-based approaches, the formation of engineered CAR-NK cells, and adoptive cell transfer. However, the restricted functionality of NK cells and the inability to infiltrate tumors are its blind spots in breast cancer patients. In this review, we gathered newly acquired data on the biology and functions of NK cells in breast cancer and proposed ways to employ this knowledge for novel therapeutic approaches in cancers, particularly breast cancer.

CD155 in tumor progression and targeted therapy

CD155, also known as the poliovirus receptor (PVR), has received considerable attention in recent years because of its intrinsic and extrinsic roles in tumor progression. Although barely expressed in host cells, CD155 is upregulated in tumor-infiltrating myeloid cells. High expression of CD155 in tumor cells across multiple cancer types is common and associated with poor patient outcomes. The intrinsic functions of CD155 in tumor cells promote tumor progression and metastasis, whereas its extrinsic immunoregulatory functions in the tumor microenvironment (TME) involve interaction with the upregulated inhibitory immune cell receptor and checkpoint TIGIT, suggesting that CD155 and CD155 pathways are promising tumor immunotherapy targets. Preclinical studies demonstrate that targeting CD155 and its receptor (anti-TIGIT) using a single treatment or in combination with anti-PD-1 can improve immune-mediated tumor control. However, there is still a limited understanding of CD155 and its associated targeting strategies, especially antibody and immune cell editing-related strategies of CD155 in cancer. Here, we review the role of CD155 in host and tumor cells in controlling tumor progression and discuss the potential of targeting CD155 for tumor therapy.

CD155 promotes radioresistance and malignancy of esophageal cancer by regulating Hippo-YAP pathway

The expression of CD155 has been observed to increase in various human cancers, but its role in the development of esophageal cancer (EC) is unclear. Radiotherapy is one of the primary therapeutic options for EC. However, radioresistance is still a severe issue in EC treatment. In this study, Oncomine database mining, immunohistochemistry, and survival analysis showed that higher expression of CD155 in patients with EC than in healthy controls. In vitro and in vivo, we found for the first time that irradiation increased the expression of CD155 in EC cells. CD155 knockdown inhibited cell proliferation and migration and tumor formation, and significantly increased radiosensitivity in EC. The in vivo model with high CD155 expression significantly promoted the proliferation and migration of EC cells. Furthermore, increased CD155 expression was associated with poor prognosis in patients with EC. CD155 regulated the Hippo-Yap pathway, influencing cell proliferation and migration. Therefore, CD155 is essential for the proliferation, migration, and radioresistance of EC. CD155 inhibition may be a viable strategy for improving radiation treatment efficacy in individuals with EC.

Tumor cell intrinsic and extrinsic features predict prognosis in estrogen receptor positive breast cancer

Although estrogen-receptor-positive (ER+) breast cancer is generally associated with favorable prognosis, clinical outcome varies substantially among patients. Genomic assays have been developed and applied to predict patient prognosis for personalized treatment. We hypothesize that the recurrence risk of ER+ breast cancer patients is determined by both genomic mutations intrinsic to tumor cells and extrinsic immunological features in the tumor microenvironment. Based on the Cancer Genome Atlas (TCGA) breast cancer data, we identified the 72 most common genomic aberrations (including gene mutations and indels) in ER+ breast cancer and defined sample-specific scores that systematically characterized the deregulated pathways intrinsic to tumor cells. To further consider tumor cell extrinsic features, we calculated immune infiltration scores for six major immune cell types. Many individual intrinsic features are predictive of patient prognosis in ER+ breast cancer, and some of them achieved comparable accuracy with the Oncotype DX assay. In addition, statistical learning models that integrated these features predicts the recurrence risk of patients with significantly better performance than the Oncotype DX assay (our optimized random forest model AUC = 0.841, Oncotype DX model AUC = 0.792, p = 0.04). As a proof-of-concept, our study indicates the great potential of genomic and immunological features in prognostic prediction for improving breast cancer precision medicine. The framework introduced in this work can be readily applied to other cancers.

Immune checkpoint CD155 promoter methylation profiling reveals cancer-associated behaviors within breast neoplasia

BACKGROUND

CD155 immune checkpoint has recently emerged as a compelling immunotherapeutic target. Epigenetic DNA methylation changes are recognized as key molecular mechanisms in cancer development. Hence, the identification of methylation markers that are sensitive and specific for breast cancer may improve early detection and predict prognosis. We speculate that CD155 promoter methylation can be a valuable epigenetic biomarker, based upon strong indications for its immunoregulatory functions.

METHODS

Methylation analyses were conducted on 14 CpGs sites in the CD155 promoter region by bisulfite pyrosequencing. To elucidate the related gene expression changes, a transcriptional study using RT-qPCR was performed. Statistical analyses were performed to evaluate correlations of CD155 methylation profiles with mRNA expression together with clinical-pathological features, prognosis and immune infiltrate.

RESULTS

CD155 promoter methylation profile was significantly associated with SBR grade, tumor size, molecular subgroups, HER2 and hormonal receptors expression status. Low CD155 methylation rates correlated with better prognosis in univariate cox proportional hazard analysis and appeared as an independent survival predictor in cox-regression multivariate analysis. Further, methylation changes at CD155 specific CpG sites were consistent with CD155 membranous mRNA isoform expression status. Statistical analyses also showed a significant association with immune Natural Killer cell infiltrate when looking at the CpG7, CpG8, CpG9 and CpG11 sites.

CONCLUSION

Altogether, our results contribute to a better understanding of the impact of CD155 immune checkpoint modality expression in breast tumors, revealing for the first time that specific CpG sites from CD155 promoter may be a potential biomarker in breast cancer monitoring.

CD155: A Key Receptor Playing Diversified Roles

Cluster of differentiation (CD155), formerly identified as poliovirus receptor (PVR) and later as immunoglobulin molecule involved in cell adhesion, proliferation, invasion and migration. It is a surface protein expressed mostly on normal and transformed malignant cells. The expression of the receptor varies based on the origin of tissue. The expression of the protein is determined by factors involved in sonic hedgehog pathway, Ras-MEK-ERK pathway and during stress conditions like DNA damage response. The protein uses alternate splicing mechanism, producing four isoforms - two being soluble (CD155β and CD155γ) and two being transmembrane protein (CD155α and CD155δ). Apart from being a viral receptor, researchers have identified CD155 having important roles in cancer research and cell signaling field. The receptor is recognized as biomarker for identifying cancerous tissue. The receptor interacts with molecules involved in cells defense mechanism. The immune-surveillance role of CD155 is being deciphered to understand the mechanistic approach it utilizes as onco-immunologic molecule. CD155 is a non-MHC-I ligand which helps in identifying non-self to NK cells via an inhibitory TIGIT ligand. The TIGIT-CD155 pathway is a novel MHC-I-independent education mechanism for cell tolerance and activation of NK cell. The receptor also has a role in metastasis of cancer and trans endothelial mechanism. In this review, authors discuss the virus-host interaction that occurs via single transmembrane receptor, the poliovirus infection pathway, which is being exploited as therapeutic pathway. The oncolytic virotherapy is now promising way for curing cancer.

Perspectives on immune checkpoint ligands: expression, regulation, and clinical implications

In the tumor microenvironment, immune checkpoint ligands (ICLs) must be expressed in order to trigger the inhibitory signal via immune checkpoint receptors (ICRs). Although ICL expression frequently occurs in a manner intrinsic to tumor cells, extrinsic factors derived from the tumor microenvironment can fine-tune ICL expression by tumor cells or prompt non-tumor cells, including immune cells. Considering the extensive interaction between T cells and other immune cells within the tumor microenvironment, ICL expression on immune cells can be as significant as that of ICLs on tumor cells in promoting anti-tumor immune responses. Here, we introduce various regulators known to induce or suppress ICL expression in either tumor cells or immune cells, and concise mechanisms relevant to their induction. Finally, we focus on the clinical significance of understanding the mechanisms of ICLs for an optimized immunotherapy for individual cancer patients.

Emerging roles of the nectin family of cell adhesion molecules in tumour-associated pathways

Tumour cells achieve maximum survival by modifying cellular machineries associated with processes such as cell division, migration, survival, and apoptosis, resulting in genetically complex and heterogeneous populations. While nectin and nectin-like cell adhesion molecules control development and maintenance of multicellular organisation in higher vertebrates by mediating cell-cell adhesion and related signalling processes, recent studies indicate that they also critically regulate growth and development of different types of cancers. In this review, we detail current knowledge about the role of nectin family members in various tumours. Furthermore, we also analyse the seemingly opposing roles of some members of nectin family in tumour-associated pathways, as they function as both tumour suppressors and oncogenes. Understanding this functional duality of nectin family in tumours will further our knowledge of molecular mechanisms regulating tumour development and progression, and contribute to the advancement of tumour diagnosis and therapy.

Immunohistochemical analysis of CD155 expression in triple-negative breast cancer patients

Introduction

CD155 is an immune checkpoint protein. Its overexpression is an indicator of poor prognosis in some types of cancer. However, the significance of CD155 expression in patients with triple-negative breast cancer, and the relationship between CD155 and programmed death-ligand 1 (PD-L1) expression, have not yet been analyzed in detail.

Methods

Using immunohistochemical staining and tissue microarrays, we analyzed the expression profiles of CD155 and PD-L1 in 61 patients with triple-negative breast cancer. Relapse-free survival and overall survival rates were compared according to CD155 expression. The correlation between CD155 expression and clinicopathological factors, including PD-L1 expression (using SP142 and 73–10 assays), was also examined.

Results

CD155 expression was noted in 25 patients (41.0%) in this cohort. CD155 expression did not correlate with pathological stage, histological grade, Ki-67 labeling index, or stromal tumor-infiltrating lymphocytes. Only PD-L1 expression in tumor cells by SP142 assay significantly correlated with CD155 expression (p = 0.035); however, PD-L1 expression in tumor cells by 73–10 assay did not show a correlation (p = 0.115). Using the 73–10 assay, 59% of patients showed CD155 and/or PD-L1 expression in tumor cells. Moreover, using the SP142 assay, 63.3% of patients showed CD155 and/or PD-L1 expression in immune cells. CD155 expression did not correlate with either relapse-free survival or overall survival (p = 0.485 and 0.843, respectively).

Conclusions

CD155 may be a novel target for antitumor immunotherapy. The results of this study indicate that CD155 may expand the pool of candidates with triple-negative breast cancer who could benefit from antitumor immunotherapy.

Prognostic and therapeutic role of tumor-infiltrating lymphocyte subtypes in breast cancer

Increased levels of total tumor-infiltrating lymphocytes (TILs) are generally associated with good prognosis in several breast cancer subtypes. Subtypes of TILs impact both tumor cells and immune cells in a variety of different ways, leading to either a pro-tumor or antitumor effect. Tumor-infiltrating CD8+ T cells and natural killer (NK) cells perform as effector cells against tumor cells and are associated with better clinical outcome. Immunotherapy approaches that improve the antitumor activity and proliferation of CD8+ T and NK cells include PD-1/PD-L1 blockade, CAR T cell therapy, or ex vivo-stimulated NK cells. A subset of CD8+ T cells, tissue-resident memory T cells, has also recently been associated with good prognosis in breast cancer patients, and has potential to serve as a predictive biomarker and therapeutic target. Tumor-infiltrating B cells also secrete apoptosis-inducing IgG antibodies and can act as antigen-presenting cells to prime CD4+ and CD8+ T cells. On the other hand, regulatory T and regulatory B cells modulate the immune response from CD8+ T cells and NK cells by secreting immunosuppressive cytokines and inhibiting maturation of antigen-presenting cells (APCs). These regulatory cells are typically associated with poor prognosis, therefore rendering suppression of their regulatory function a key immunotherapeutic strategy.

Immune checkpoint molecules B7-H6 and PD-L1 co-pattern the tumor inflammatory microenvironment in human breast cancer

B7-H6 and PD-L1 belong to the B7 family co-stimulatory molecules fine-tuning the immune response. The present work investigates the clinical effect of B7-H6 protein expression with PD-L1 status and the infiltration of natural killer cells as potential biomarkers in breast tumor inflammatory microenvironment. The expression levels of B7-H6 protein by cancer cells and immune infiltrating cells in human breast cancer tissues and evaluate their associations with PD-L1 expression, NK cell status, clinical pathological features and prognosis were explored. The immunohistochemistry labeling method was used to assess B7-H6 and PD-L1 proteins expression by cancer and immune cells. The associations between immune checkpoint, major clinical pathological variables and survival rates were analyzed. B7-H6 protein was depicted in both breast and immune cells. Results showed that Tumor B7-H6 expression is highly associated with Her-2 over expression. B7-H6 + immune cells are highly related to the Scarff–Bloom–Richardson grade and associated with PD-L1 expression and NK cells status. Survival analysis revealed a better prognosis in patients with low expression of B7-H6 by cancer cells. Conversely, B7-H6 + immune cells were significantly associated with longer survival. Findings strongly suggest an interaction between B7 molecules that contributes to a particular design of the inflammatory microenvironment. This may influence the efficiency of therapies based on antibodies blocking the PD-L1/PD1 pathway and can explain the detection of clinical benefits only in a fraction of patients treated with immune checkpoint inhibitors.

Targeting NK Cells to Enhance Melanoma Response to Immunotherapies

Natural killer (NK) cells are a key component of an innate immune system. They are important not only in initiating, but also in augmenting adaptive immune responses. NK cell activation is mediated by a carefully orchestrated balance between the signals from inhibitory and activating NK cell receptors. NK cells are potent producers of proinflammatory cytokines and are also able to elicit strong antitumor responses through secretion of perforin and granzyme B. Tumors can develop many mechanisms to evade NK cell antitumor responses, such as upregulating ligands for inhibitory receptors, secreting anti-inflammatory cytokines and recruiting immunosuppressive cells. Enhancing NK cell responses will likely augment the effectiveness of immunotherapies, and strategies to accomplish this are currently being evaluated in clinical trials. A comprehensive understanding of NK cell biology will likely provide additional opportunities to further leverage the antitumor effects of NK cells. In this review, we therefore sought to highlight NK cell biology, tumor evasion of NK cells and clinical trials that target NK cells.

Therapeutic Targeting of Checkpoint Receptors within the DNAM1 Axis

Therapeutic antibodies targeting the CTLA4/PD-1 pathways have revolutionized cancer immunotherapy by eliciting durable remission in patients with cancer. However, relapse following early response, attributable to primary and adaptive resistance, is frequently observed. Additional immunomodulatory pathways are being studied in patients with primary or acquired resistance to CTLA4 or PD-1 blockade. The DNAM1 axis is a potent coregulator of innate and adaptive immunity whose other components include the immunoglobulin receptors TIGIT, PVRIG, and CD96, and their nectin and nectin-like ligands. We review the basic biology and therapeutic relevance of this family, which has begun to show promise in cancer clinical trials. SIGNIFICANCE: Recent studies have outlined the immuno-oncologic ascendancy of coinhibitory receptors in the DNAM1 axis such as TIGIT and PVRIG and, to a lesser extent, CD96. Biological elucidation backed by ongoing clinical trials of single-agent therapy directed against TIGIT or PVRIG is beginning to provide the rationale for testing combination regimens of DNAM1 axis blockers in conjunction with anti-PD-1/PD-L1 agents.

Cancer Immunotherapy and the Nectin Family

It is increasingly clear that the nectin family and its immunoreceptors shape the immune response to cancer through several pathways. Yet, even as antibodies against TIGIT, CD96, and CD112R advance into clinical development, biological and therapeutic questions remain unanswered. Here, we review recent progress, prospects, and challenges to understanding and tapping this family in cancer immunotherapy.

TIGIT/CD226 Axis Regulates Anti-Tumor Immunity

Tumors escape immune surveillance by inducing various immunosuppressive pathways, including the activation of inhibitory receptors on tumor-infiltrating T cells. While monoclonal antibodies (mAbs) blocking programmed cell death 1 (PD-1), programmed death-ligand 1 (PD-L1), and cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) have been approved for multiple cancer indications, only a subset of patients benefit from immune checkpoint blockade therapies, highlighting the need for additional approaches. Therefore, the identification of new target molecules acting in distinct or complementary pathways in monotherapy or combination therapy with PD-1/PD-L1 blockade is gaining immense interest. T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif (ITIM) domains (TIGIT) has received considerable attention in cancer immunotherapy. Recently, anti-TIGIT mAb (tiragolumab) has demonstrated promising clinical efficacy in non-small cell lung cancer treatment when combined with an anti-PD-L1 drug (Tecentriq), leading to phase III trial initiation. TIGIT is expressed mainly on T and natural killer cells; it functions as an inhibitory checkpoint receptor, thereby limiting adaptive and innate immunity. CD226 competes for binding with the same ligands with TIGIT but delivers a positive stimulatory signal to the immune cells. This review discusses the recent discoveries regarding the roles of TIGIT and CD226 in immune cell function and their potential application in cancer immunotherapy.

Prognostic Value of Natural Killer Cells Besides Tumor-Infiltrating Lymphocytes in Breast Cancer Tissues

BACKGROUND

Each subgroup of immune cells has a different prognostic role in breast cancer; however, the prognostic impact of tumor-infiltrating natural killer cells (TINKs) is still not well established. Our aim was to assess the prognostic impact of natural killer (NK) cells in breast carcinomas.

MATERIALS AND METHODS

NK cells infiltration were assessed by immunohistochemistry (IHC). Statistical analyses were performed to evaluate the correlation of NK cells with clinical-pathological features and outcome.

RESULTS

CD56 IHC was realized in 126 patients. NK cells infiltration showed significant and positive association with tumor high Scarff-Bloom-Richardson (SBR) grade. NK cells were significantly associated with HER2-positive breast cancer and triple-negative breast cancer subtypes. Analyses showed significant and inverse correlation with progesterone and estrogen receptors expression status. High NK cells were significantly related to high Ki-67 labeling index. Our data showed that high NK cells infiltrate was significantly associated with tumor-infiltrating lymphocytes in breast cancer tissues. At a median follow-up of 5.5 years, high CD56 expression (≥ 5 cells/10 high power field) was associated significantly with a good overall survival and with good disease-free survival.

CONCLUSION

In this study, we assessed the important prognostic role of TINKs in breast carcinomas, which seems to be evident despite its association with aggressive pathological features. Thus evaluation of NK cells can be standardized and integrated in daily routine.

CD155-Prognostic and Immunotherapeutic Implications Based on Multiple Analyses of Databases Across 33 Human Cancers

Growing evidence has suggested that CD155 participates in the regulation of many biological processes ranging cell growth, invasion, and migration from regulation of immune responses in most malignances. However, the impact of prognostic value and CD115-related immune response on the survival in multiple cancers remains incompletely clear. In our study, we assessed the prognostic significance and immune-associated mechanism of CD155 based on data from multiple databases and methods, including UCSC Xena, Oncomine, PrognoScan. We identified that CD155 was commonly upregulated in most human cancers, and High expression of CD155 was closely correlated with unfavorable clinical outcomes in 10/33 of human cancers, while CD155 at low level was responsible for better survival in KICH and PAAD. More intriguingly, CD155 expression had a significant interaction with immune function in several tumors by analyzing Tumor mutational burden and microsatellite in stability, immune score and stromal score. The correlation between immune infiltration and CD155 expression also indicated that CD155 expression positively correlated with CD4+ T cells in Head and Neck squamous cell carcinoma, Lung adenocarcinoma and Colon adenocarcinoma, while had inversely interaction with CD8+ T in Kidney renal clear cell carcinoma and Head and Neck squamous cell carcinoma as well as Tregs in Skin Cutaneous Melanoma, Head and Neck squamous cell carcinoma and Bladder Urothelial Carcinoma. These findings indicate CD155 correlates with cancer immunotherapy function. In conclusions, our observations revealed CD155 might function as immune-associated system in the development of human cancers, and acted as a promising prognostic and therapeutic target against human cancers.

Hitting the complexity of the TIGIT-CD96-CD112R-CD226 axis for next-generation cancer immunotherapy

Antibody-based therapeutics targeting the inhibitory receptors PD-1, PD-L1, or CTLA-4 have shown remarkable clinical progress on several cancers. However, most patients do not benefit from these therapies. Thus, many efforts are being made to identify new immune checkpoint receptor-ligand pathways that are alternative targets for cancer immunotherapies. Nectin and nectin-like molecules are widely expressed on several types of tumor cells and play regulatory roles in T- and NK-cell functions. TIGIT, CD226, CD96 and CD112R on lymphoid cells are a group of immunoglobulin superfamily receptors that interact with Nectin and nectin-like molecules with different affinities. These receptors transmit activating or inhibitory signals upon binding their cognate ligands to the immune cells. The integrated signals formed by their complex interactions contribute to regu-lating immune-cell functions. Several clinical trials are currently evaluating the efficacy of anti-TIGIT and anti-CD112R blockades for treating patients with solid tumors. However, many questions still need to be answered in order to fully understand the dynamics and functions of these receptor networks. This review addresses the rationale behind targeting TIGIT, CD226, CD96, and CD112R to regulate T- and NK-cell functions and discusses their potential application in cancer immunotherapy.

CD155 Overexpression Correlates With Poor Prognosis in Primary Small Cell Carcinoma of the Esophagus

CD155/TIGIT overexpression has been detected in various human malignancies; however, its expression status in primary small cell carcinoma of the esophagus (PSCCE) and its prognostic significance remain unclear. In this study, we aimed to explore the expression and prognostic value of CD155 and TIGIT in PSCCE. We detected CD155 and TIGIT expression in 114 cases of PSCCE using immunohistochemistry (IHC) and evaluated their relationship with the clinicopathological characteristics and survival of the patients. Survival analyses were performed using the Kaplan-Meier method and Cox proportional hazards model. Nomogram performance was assessed via the concordance index (C-index) and calibration plots. Decision curve analysis (DCA) was performed to evaluate the net benefit of the nomogram. We found that CD155 and TIGIT were overexpressed in PSCCE tissues, CD155 expression correlated positively with TIGIT (p < 0.001) and was significantly associated with tumor size, T stage, distant metastasis, TNM stage, and Ki-67 score. TIGIT expression was also significantly associated with T stage, distant metastasis, and TNM stage. Patients with high CD155 and TIGIT expression had a significantly shorter overall survival (OS) and progression-free survival (PFS), while the multivariate model showed that CD155 expression and the therapeutic strategy are independent prognostic factors for PSCCE. In the validation step, OS was shown to be well-calibrated (C-index = 0.724), and a satisfactory clinical utility was proven by DCA. In conclusion, our findings revealed that CD155 and TIGIT are highly expressed in patients with PSCCE and are associated with shorter OS and PFS, supporting their role as prognostic biomarker.

Natural Killer Cell Defects in Breast Cancer: A Key Pathway for Tumor Evasion

As the most important innate immune component cancers invader, natural killer (NK) cells have a magnificent role in antitumor immunity without any prior sensitization. Different subsets of NK cells have distinct responses during tumor cell exposure, according to their phenotypes and environments. Their function is induced mainly by the activity of both inhibitory and activating receptors against cancerous cells. Since the immunosuppression in the tumor microenvironment of breast cancer patients has directly deteriorated the phenotype and disturbed the function of NK cells, recruiting compensatory mechanisms indicate promising outcomes for immunotherapeutic approaches. These evidences accentuate the importance of NK cell distinct features in protection against breast tumors. In this review, we discuss the several mechanisms involved in NK cells suppression which consequently promote tumor progression and disease recurrence in patients with breast cancer.

NK cell infiltration is associated with improved overall survival in solid cancers: A systematic review and meta-analysis

The immune landscape of a tumor is highly connected to patient prognosis and response to treatment, but little is known about how natural killer (NK) cells predict overall survival (OS) among patients with solid tumors. We present the first meta-analysis on NK cell infiltration into solid tumors as a prognostic indicator for OS, considering cancer types independently, and together. Samples were collected from 1973 to 2016 with results published between 1989 and 2020. From 53 studies, we found that NK cell infiltration corresponds with decreased risk of death (HR=0.34, 95% CI: 0.26-0.46; p<0.0001). Among studies that investigated the prognostic potential of NK cells in specific regions of the tumor, intraepithelial infiltration was better predictive of OS than NK infiltration in the tumor-adjacent stroma. Generally, NK cell infiltration is lower in advanced-stage and lower-grade tumors; nevertheless, it remains prognostically beneficial. This meta-analysis highlights an important prognostic role of NK cells in solid tumors, but exposes that few studies have considered the contributions of NK cells. Toward NK cell-based immunotherapies, it will be important to understand the conditions under which NK cells can be effective agents of tumor control.

Tumor-derived soluble CD155 inhibits DNAM-1-mediated antitumor activity of natural killer cells

CD155 is a ligand for DNAM-1, TIGIT, and CD96 and is involved in tumor immune responses. Unlike mouse cells, human cells express both membranous CD155 and soluble CD155 (sCD155) encoded by splicing isoforms of CD155. However, the role of sCD155 in tumor immunity remains unclear. Here, we show that, after intravenous injection with sCD155-producing B16/BL6 melanoma, the numbers of tumor colonies in wild-type (WT), TIGIT knock-out (KO), or CD96 KO mice, but not DNAM-1 KO mice, were greater than after injection with parental B16/BL6 melanoma. NK cell depletion canceled the difference in the numbers of tumor colonies in WT mice. In vitro assays showed that sCD155 interfered with DNAM-1–mediated NK cell degranulation. In addition, DNAM-1 had greater affinity than TIGIT and CD96 for sCD155, suggesting that sCD155 bound preferentially to DNAM-1. Together, these results demonstrate that sCD155 inhibits DNAM-1–mediated cytotoxic activity of NK cells, thus promoting the lung colonization of B16/BL6 melanoma.

NK Cell Adoptive Immunotherapy of Cancer: Evaluating Recognition Strategies and Overcoming Limitations

Natural killer (NK) cells, the primary effector cells of the innate immune system, utilize multiple strategies to recognize tumor cells by (1) detecting the presence of activating receptor ligands, which are often upregulated in cancer; (2) targeting cells that have a loss of major histocompatibility complex (MHC); and (3) binding to antibodies that bind to tumor-specific antigens on the tumor cell surface. All these strategies have been successfully harnessed in adoptive NK cell immunotherapies targeting cancer. In this review, we review the applications of NK cell therapies across different tumor types. Similar to other forms of immunotherapy, tumor-induced immune escape and immune suppression can limit NK cell therapies' efficacy. Therefore, we also discuss how these limitations can be overcome by conferring NK cells with the ability to redirect their tumor-targeting capabilities and survive the immune-suppressive tumor microenvironment. Finally, we also discuss how future iterations can benefit from combination therapies with other immunotherapeutic agents.

Targeting the "PVR-TIGIT axis" with immune checkpoint therapies

Checkpoint inhibitors have become an efficient way to treat cancers. Indeed, anti-CTLA-4, anti-PD1, and anti-PDL-1 antibodies are now used as therapies for cancers. However, while these therapies are very efficient in certain tumors, they remain poorly efficient in others. This might be explained by the immune infiltrate, the expression of target molecules, and the influence of the tumor microenvironment. It is therefore critical to identify checkpoint antigens that represent alternative targets for immunotherapies. PVR-like molecules play regulatory roles in immune cell functions. These proteins are expressed by different cell types and have been shown to be upregulated in various malignancies. PVR and Nectin-2 are expressed by tumor cells as well as myeloid cells, while TIGIT, CD96, and DNAM-1 are expressed on effector lymphoid cells. PVR is able to bind DNAM-1, CD96, and TIGIT, which results in two distinct profiles of effector cell activation. Indeed, while binding to DNAM-1 induces the release of cytokines and cytotoxicity of cytotoxic effector cells, binding TIGIT induces an immunosuppressive and non-cytotoxic profile. PVR is also able to bind CD96, which induces an immunosuppressive response in murine models. Unfortunately, in humans, results remain contradictory, and this interaction might induce the activation or the suppression of the immune response. Similarly, Nectin-2 was shown to bind TIGIT and to induce regulatory profiles in effectors cells such as NK and T cells. Therefore, these data highlight the potential of each of the molecules of the “PVR–TIGIT axis” as a potential target for immune checkpoint therapy. However, many questions remain to be answered to fully understand the mechanisms of this synapse, in particular for human CD96 and Nectin-2, which are still understudied. Here, we review the recent advances in “PVR–TIGIT axis” research and discuss the potential of targeting this axis by checkpoint immunotherapies.

Prognostic significance of tumor poliovirus receptor and CTLA4 expression in patients with surgically resected non-small-cell lung cancer

INTRODUCTION

Poliovirus receptor (PVR) is a tumor promoter and a regulatory checkpoint that enhances immunosuppression. We investigated PVR expression by applying immunohistochemistry (IHC) staining. A positive association existed between PVR expression and cytotoxic T lymphocyte-associated antigen 4 (CTLA4) expression in patients with surgically resected non-small-cell lung cancer (NSCLC). PVR expression is a prognosis predictor of lung adenocarcinoma.

PURPOSE

To investigate the prognostic significance of PVR expression and CTLA4 expression for surgically resected NSCLC.

PATIENTS AND METHODS

The medical records of 108 Chinese patients with primary NSCLC who underwent surgery were retrospectively reviewed. The expression of PVR and CTLA4 were measured through IHC. Clinical characteristics, the association between PVR and CTLA4, and the prognostic significance of PVR were analyzed.

RESULTS

A significant positive association was observed between PVR and CTLA4 expression in NSCLC (P = 0.016). PVR had a high positive rate among females, nonsmokers, and patients with adenocarcinoma and advanced lung cancer. The overall survival (OS) of patients with negative PVR expression was significantly longer than that of patients with positive PVR expression (P = 0.049), especially among females (P = 0.03) and nonsmokers (P = 0.025). Multivariate analysis results showed that advanced tumor stage and PVR expression were independent prognosis predictors of poor OS.

CONCLUSION

PVR can potentially serve as a prognostic predictor and biomarker for NSCLC and cancer anti-CTLA4 immunotherapy response.

Overexpression of an Immune Checkpoint (CD155) in Breast Cancer Associated with Prognostic Significance and Exhausted Tumor-Infiltrating Lymphocytes: A Cohort Study

Purpose

The immune checkpoint inhibitor is approved for breast cancer treatment, but the low expression of PD-L1 limits the immunotherapy. CD155 is another immune checkpoint protein in cancers and interacts with ligands to regulate immune microenvironment. This study is aimed at investigating the expression of CD155 and the association with prognosis and pathological features of breast cancer.

Methods

126 patients were recruited this cohort study consecutively, and CD155 expression on tumor cells was detected by immunohistochemistry. The Kaplan-Meier survival curve and Cox hazard regression model were used to estimate the association.

Results

38.1% patients had an overexpression of CD155, and the proportion of tumor cells with CD155 overexpression was 17%, 39%, 37%, and 62% among Luminal A, Luminal B, HER2-positive, and triple negative breast cancer cases, respectively (p < 0.05). Patients with CD155 overexpression had the Ki-67 index significantly higher than that of patients with low expression (42% vs. 26%). Though the number of tumor-infiltrating lymphocytes was higher among patients with CD155 overexpression (144/HPF vs. 95/HPF), the number of PD-1⁺ lymphocytes was significantly higher (52/HPF vs. 25/HPF, p < 0.05). Patients of CD155 overexpression had the disease-free and overall survival decreased by 13 months and 9 months, respectively (p < 0.05). CD155 overexpression was associated with an increased relapse (HR = 13.93, 95% CI 2.82, 68.91) and death risk for breast cancer patients (HR = 5.47, 1.42, 20.99).

Conclusions

Overexpression of CD155 was correlated with more proliferative cancer cells and a dysfunctional immune microenvironment. CD155 overexpression introduced a worse relapse-free and overall survival and might be a potential immunotherapy target for breast cancer.

Dually regulating the proliferation and the immune microenvironment of melanoma via nanoparticle-delivered siRNA targeting onco-immunologic CD155

Nanoparticle-delivered siRNA targeting CD155 for dual regulation of the proliferation and of the immune microenvironment of melanoma.

Tumor intrinsic and extrinsic immune functions of CD155

CD155 (PVR/necl5/Tage4), a member of the nectin-like family of adhesion molecules, is highly upregulated on tumor cells across multiple cancer types and has been associated with worse patient outcomes. In addition to well described cell-intrinsic roles promoting tumor progression and metastasis, CD155 has now been implicated in immune regulation. The role of CD155 as a potent immune ligand with diverse cell-extrinsic functions is now being defined. CD155 signaling to immune cells is mediated through interactions with the co-stimulatory immune receptor CD226 (DNAM-1) and the inhibitory checkpoint receptors TIGIT and CD96, which are differentially regulated at the cell surface on T cells and NK cells. The integration of signals from CD155 cognate receptors modifies the activity of tumor-infiltrating lymphocytes in a context-dependent manner, making CD155 an attractive target for immune-oncology. Preclinical studies suggest that targeting this axis can improve immune-mediated tumor control, particularly when combined with existing anti-PD-1 checkpoint therapies. In this review, we discuss the roles of CD155 on host and tumor cells in controlling tumor progression and discuss the possibility of targeting CD155 for cancer therapy.

Targeting the TIGIT-PVR immune checkpoint axis as novel therapeutic option in breast cancer

Immune checkpoints are intensively investigated as targets in cancer therapy. T-cell immunoreceptor with immunoglobulin (Ig) and ITIM domains (TIGIT) and its ligand poliovirus receptor (PVR) are recently emerging as novel promising targets in immunotherapy. Here, we show that high expression of PVR represents an independent prognostic marker being associated with poor outcome for breast cancer patients. Furthermore, PVR mRNA, as well as protein expression, is associated with more aggressive breast cancer subtypes such as HER2 positive and triple-negative breast cancer. In vitro, blocking TIGIT or PVR resulted in enhanced immune cell-mediated lysis of breast cancer cell lines SKBR-3, MDA-MB-231, MDA-MB-468, and BT549 and additionally increased the cytotoxic effects of a bispecific T cell engager BiTE® antibody construct targeting EGFR. Taken together, our data identify the immune checkpoint factor PVR as a novel prognostic marker in breast cancer and indicate that blocking the TIGIT-PVR axis might represent a novel therapeutic option for the treatment of breast cancer patients.