STING activator 2'3'-cGAMP enhanced HSV-1-based oncolytic viral therapy

Oncolytic viruses (OVs) can selectively replicate in tumor cells and remodel the microenvironment of immunologically cold tumors, making them a promising strategy to evoke antitumor immunity. Similarly, agonists of the stimulator of interferon genes (STING)-interferon (IFN) pathway, the main cellular antiviral system, provide antitumor benefits by inducing the activation of dendritic cells (DC). Considering how the activation of the STING-IFN pathway could potentially inhibit OV replication, the use of STING agonists alongside OV therapy remains largely unexplored. Here, we explored the antitumor efficacy of combining an HSV-1-based OV, C-REV, with a membrane-impermeable STING agonist, 2'3'-GAMP. Our results demonstrated that tumor cells harbor a largely defective STING-IFN pathway, thereby preventing significant antiviral IFN induction regardless of the permeability of the STING agonist. In vivo, the combination therapy induced more proliferative KLRG1-high PD1-low CD8+ T-cells and activated CD103+ DC in the tumor site and increased tumor-specific CD44+ CD8+ T-cells in the lymph node. Overall, the combination therapy of C-REV with 2'3'-cGAMP elicited antitumor immune memory responses and significantly enhanced systemic antitumor immunity in both treated and non-treated distal tumors.

The Impact of Metformin on Tumor-Infiltrated Immune Cells: Preclinical and Clinical Studies

The tumor microenvironment (TME) plays a pivotal role in the fate of cancer cells, and tumor-infiltrating immune cells have emerged as key players in shaping this complex milieu. Cancer is one of the leading causes of death in the world. The most common standard treatments for cancer are surgery, radiation therapy, and chemotherapeutic drugs. In the last decade, immunotherapy has had a potential effect on the treatment of cancer patients with poor prognoses. One of the immune therapeutic targeted approaches that shows anticancer efficacy is a type 2 diabetes medication, metformin. Beyond its glycemic control properties, studies have revealed intriguing immunomodulatory properties of metformin. Meanwhile, several studies focus on the impact of metformin on tumor-infiltrating immune cells in various tumor models. In several tumor models, metformin can modulate tumor-infiltrated effector immune cells, CD8+, CD4+ T cells, and natural killer (NK) cells, as well as suppressor immune cells, T regulatory cells, tumor-associated macrophages (TAMs), and myeloid-derived suppressor cells (MDSCs). In this review, we discuss the role of metformin in modulating tumor-infiltrating immune cells in different preclinical models and clinical trials. Both preclinical and clinical studies suggest that metformin holds promise as adjunctive therapy in cancer treatment by modulating the immune response within the tumor microenvironment. Nonetheless, both the tumor type and the combined therapy have an impact on the specific targets of metformin in the TME. Further investigations are warranted to elucidate the precise mechanisms underlying the immunomodulatory effects of metformin and to optimize its clinical application in cancer patients.

Metformin enhances the antitumor activity of oncolytic herpes simplex virus HF10 (canerpaturev) in a pancreatic cell cancer subcutaneous model

Oncolytic virus (OV) therapy is a promising cancer immunotherapy, especially for cold tumors by inducing the direct lysis of cancer cells and initiation of potent antitumor response. Canerpaturev (C-REV) is an attenuated oncolytic herpes simplex virus-1, which demonstrated a potent antitumor effect in various preclinical models when used either alone or combined. Metformin is a commonly prescribed antidiabetic drug that demonstrated a potent immune modulator effect and antitumor response. We combined C-REV with metformin in a low immunogenic bilateral murine tumor model to enhance C-REV's antitumor efficacy. In vitro, metformin does not enhance the C-REV cell cytotoxic effect. However, in in vivo model, intratumoral administration of C-REV with the systemic administration of metformin led to synergistic antitumor effect on both sides of tumor and prolonged survival. Moreover, combination therapy increased the effector CD44⁺ CD8⁺ PD1^- subset and decreased the proportion of terminally-differentiated CD103⁺ KLRG-1⁺ T-regulatory cells on both sides of tumor. Interestingly, combination therapy efficiently modulates conventional dendritic cells type-1 (cDC1) on tumors, and tumor-drained lymph nodes. Our findings suggest that combination of C-REV and metformin enhances systemic antitumor immunity. This study may provide insights into the mechanism of action of OV therapy plus metformin combination against various tumor models.

Problem-Based Learning in Child and Adolescent Psychiatry: A Perspective from Japan

PURPOSE

Japanese higher education institutions have long been striving for the globalization of medical education. Nagoya University (NU) adopted PBL as a means of enhancing intercultural awareness in globalizing medical education by working with the Norwegian University of Science and Technology (NTNU), Faculty of Medicine and Health Science, under the Trondheim NTNU-Nagoya (TroNa) partnership for mobility and internationalization of child and mental health studies. This study aims to assess students' attitudes towards PBL and to suggest future developments in this form of education by introducing common PBL scenarios experienced at NTNU and NU.

METHODS

Two 90-minute PBL sessions were conducted at NU. Ten groups of medical students were formed, each consisting of up to 10 students, and students were asked to fill in a questionnaire developed to assess their understanding of, attitudes to and satisfaction with the classes. We investigated three different groups of questions on: NU medical students' general impressions of PBL; their impressions of PBL in child and adolescent psychiatry (CAP); and their impressions of PBL in specific case scenarios. Correlations between each of the questions from the three groups were evaluated using multivariate analysis.

RESULTS

Overall, a majority of the NU medical students were satisfied with PBL, while a small number preferred traditional lecture-style learning (5%). More than half of the students agreed that PBL increased their understanding and interest in CAP (53%), although some male students felt that the amount of time spent was insufficient (20.3%). Correlations were seen for students who thought that PBL enhanced their understanding of and interest in CAP. Regarding case scenarios, most students (82.5%) agreed that PBL helped them to develop clinical problem-solving skills.

CONCLUSION

The study found an overall positive attitude towards PBL, PBL in CAP and the specific PBL case scenario presented.

S-1 facilitates canerpaturev (C-REV)-induced antitumor efficacy in a triple-negative breast cancer model

Canerpaturev (C-REV) is a highly attenuated, replication-competent, mutant strain of oncolytic herpes simplex virus type 1 that may be an effective new cancer treatment option. S-1, an oral formulation containing the 5-fluorouracil (5-FU) prodrug tegafur and the two enzyme modulators gimeracil and oteracil, is used as a key chemotherapeutic agent for metastatic recurrent breast cancer. Although the antitumor effects of oncolytic viruses combined with 5-FU in vivo have been reported, the detailed mechanisms are unknown. Here, we investigated the antitumor mechanism of the combination of C-REV and S-1 in triple-negative breast cancer (TNBC) in the context of tumor immunity. The combined effect of C-REV and S-1 was evaluated in a bilateral tumor model of murine TNBC 4T1 in vivo. S-1 enhanced the TNBC growth inhibitory effects of C-REV, and decreased the number of tumor-infiltrating, myeloid-derived suppressor cells (MDSCs), which suppress both innate and adaptive immune responses. Moreover, C-REV alone and in combination with S-1 significantly increased the number of CD8⁺ T cells in the tumor and the production of interferon γ (IFNγ) from these cells. Our findings indicate that C-REV suppresses TNBC tumor growth by inducing the expansion of effector CD8⁺ T cell subsets in tumors in which S-1 can inhibit MDSC function. Our study suggests that MDSCs may be an important cellular target for breast cancer treatment. The combination of C-REV and S-1 is a new approach that might be directly translated into future clinical trials against TNBC.

C-REV Retains High Infectivity Regardless of the Expression Levels of cGAS and STING in Cultured Pancreatic Cancer Cells

Oncolytic virus (OV) therapy is widely considered as a major breakthrough in anti-cancer treatments. In our previous study, the efficacy and safety of using C-REV for anti-cancer therapy in patients during stage I clinical trial was reported. The stimulator of interferon genes (STING)-TBK1-IRF3-IFN pathway is known to act as the central cellular host defense against viral infection. Recent reports have linked low expression levels of cGAS and STING in cancer cells to poor prognosis among patients. Moreover, downregulation of cGAS and STING has been linked to higher susceptibility to OV infection among several cancer cell lines. In this paper, we show that there is little correlation between levels of cGAS/STING expression and susceptibility to C-REV among human pancreatic cancer cell lines. Despite having a responsive STING pathway, BxPC-3 cells are highly susceptible to C-REV infection. Upon pre-activation of the STING pathway, BxPc-3 cells exhibited resistance to C-REV infection. However, without pre-activation, C-REV completely suppressed the STING pathway in BxPC-3 cells. Additionally, despite harboring defects in the STING pathway, other high-grade cancer cell lines, such as Capan-2, PANC-1 and MiaPaCa-2, still exhibited low susceptibility to C-REV infection. Furthermore, overexpression of STING in MiaPaCa-2 cells altered susceptibility to a limited extent. Taken together, our data suggest that the cGAS-STING pathway plays a minor role in the susceptibility of pancreatic cancer cell lines to C-REV infection.

Oncolytic herpes simplex virus HF10 (canerpaturev) promotes accumulation of CD8+ PD-1- tumor-infiltrating T cells in PD-L1-enriched tumor microenvironment

Oncolytic viruses (OVs) remodel the tumor microenvironment by switching a "cold" tumor into a "hot" tumor with high CD8⁺ T-cell infiltration. CD8⁺ T-cell activity plays an essential role in the antitumor efficacy of OVs. However, the activity of T cells is impaired by the programmed cell death protein-1/programmed cell death-ligand 1 (PD-1/PD-L1) interaction. To date, it remains unclear why OVs alone have a significant antitumor activity even when PD-L1 expression persists on tumor or immune cells. In this study, we found that canerpaturev (C-REV) treatment significantly suppressed tumor growth, even though it induced a significant increase in PD-L1 expression in tumors in vivo as well as persistence of high PD-L1 expression on antigen-presenting cells (macrophage and dendritic cells [DCs]). Surprisingly, we observed that C-REV treatment increased the abundance of activated CD8⁺ PD-1^- tumor-infiltrating lymphocytes (TILs) in the tumor on both the injected and contralateral sides, although infiltration of CD8⁺ PD-1^high TILs into the tumor was observed in the control group. Moreover, the difference in PD-1 expression was observed only in tumors after treatment with C-REV, whereas most CD8⁺ T cells in the spleen, tumor-draining lymph nodes and blood were PD-1-negative, and this did not change after C-REV treatment. In addition, changes in expression of T-cell immunoglobulin and mucin-domain containing-3 and T-cell immune-receptor with Ig and ITIM domains were not observed on CD8⁺ TILs after C-REV treatment. Taken together, our findings may reveal mechanisms that allow OVs to trigger an antitumor immune response, irrespective of a PD-L1-enriched tumor microenvironment, by recruitment of CD8⁺ PD-1^- TILs.

Genomic Signature of the Natural Oncolytic Herpes Simplex Virus HF10 and Its Therapeutic Role in Preclinical and Clinical Trials

Oncolytic viruses (OVs) are opening new possibilities in cancer therapy with their unique mechanism of selective replication within tumor cells and triggering of antitumor immune responses. HF10 is an oncolytic herpes simplex virus-1 with a unique genomic structure that has non-engineered deletions and insertions accompanied by frame-shift mutations, in contrast to the majority of engineered OVs. At the genetic level, HF10 naturally lacks the expression of UL43, UL49.5, UL55, UL56, and latency-associated transcripts, and overexpresses UL53 and UL54. In preclinical studies, HF10 replicated efficiently within tumor cells with extensive cytolytic effects and induced increased numbers of activated CD4⁺ and CD8⁺ T cells and natural killer cells within the tumor, leading to a significant reduction in tumor growth and prolonged survival rates. Investigator-initiated clinical studies of HF10 have been completed in recurrent breast carcinoma, head and neck cancer, and unresectable pancreatic cancer in Japan. Phase I trials were subsequently completed in refractory superficial cancers and melanoma in the United States. HF10 has been demonstrated to have a high safety margin with low frequency of adverse effects in all treated patients. Interestingly, HF10 antigens were detected in pancreatic carcinoma over 300 days after treatment with infiltration of CD4⁺ and CD8⁺ T cells, which enhanced the immune response. To date, preliminary results from a Phase II trial have indicated that HF10 in combination with ipilimumab (anti-CTLA-4) is safe and well tolerated, with high antitumor efficacy. Improvement of the effect of ipilimumab was observed in patients with stage IIIb, IIIc, or IV unresectable or metastatic melanoma. This review provides a concise description of the genomic functional organization of HF10 compared with talimogene laherparepvec. Furthermore, this review focuses on HF10 in cancer treatment as monotherapy as well as in combination therapy through a concise description of all preclinical and clinical data. In addition, we will address approaches for future directions in HF10 studies as cancer therapy.