Efficacy of a third-generation oncolytic herpes simplex virus in neuroendocrine tumor xenograft models

Virus-associated neuroendocrine cancers: Pathogenesis and current therapeutics

Neuroendocrine neoplasms (NENs) comprise malignancies involving neuroendocrine cells that often lead to fatal pathological conditions. Despite escalating global incidences, NENs still have poor prognoses. Interestingly, research indicates an intricate association of tumor viruses with NENs. However, there is a dearth of comprehension of the complete scenario of NEN pathophysiology and its precise connections with the tumor viruses. Interestingly, several cutting-edge experiments became helpful for further screening of NET for the presence of polyomavirus, Human papillomavirus (HPV), Kaposi sarcoma-associated herpesvirus (KSHV), Epstein Barr virus (EBV), etc. Current research on the neuroendocrine tumor (NET) pathogenesis provides new information concerning their molecular mechanisms and therapeutic interventions. Of note, scientists observed that metastatic neuroendocrine tumors still have a poor prognosis with a palliative situation. Different oncolytic vector has already demonstrated excellent efficacies in clinical studies. Therefore, oncolytic virotherapy or virus-based immunotherapy could be an emerging and novel therapeutic intervention. In-depth understanding of all such various aspects will aid in managing, developing early detection assays, and establishing targeted therapeutic interventions for NENs concerning tumor viruses. Hence, this review takes a novel approach to discuss the dual role of tumor viruses in association with NENs' pathophysiology as well as its potential therapeutic interventions.

Treatment of HPV-Related Uterine Cervical Cancer with a Third-Generation Oncolytic Herpes Simplex Virus in Combination with an Immune Checkpoint Inhibitor

Cervical cancer is one of the most common cancers in women. The development of new therapies with immune checkpoint inhibitors (ICIs) is being investigated for cervical cancer; however, their efficacy is not currently sufficient. Oncolytic virus therapy can increase tumor immunogenicity and enhance the antitumor effect of ICIs. In this report, the therapeutic potential of a triple-mutated oncolytic herpes virus (T-01) with an ICI for human papillomavirus (HPV)-related cervical cancer was evaluated using a bilateral syngeneic murine model. The efficacy of intratumoral (i.t.) administration with T-01 and subcutaneous (s.c.) administration of anti-programmed cell death ligand 1 (PD-L1) antibody (Ab) was equivalent to that of anti-PD-L1 Ab alone on the T-01-injected side. Moreover, combination therapy had no significant antitumor effect compared to monotherapy on the T-01-non-injected side. Combination therapy significantly increased the number of tumor specific T cells in the tumor. While T-01 could not be isolated from tumors receiving combination therapy, it could be isolated following T-01 monotherapy. Furthermore, T-01 had a cytotoxic effect on stimulated T cells. These results suggest that T-01 and anti-PD-L1 Ab partially counteract and therefore concomitant administration should be considered with caution.

Immunotherapy in Gastroenteropancreatic Neuroendocrine Neoplasia

The worldwide prevalence and incidence of gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) and of NENs, in general, have been increasing recently. While valuing the considerable progress made in the treatment strategies for GEP-NEN in recent years, patients with advanced, metastasized disease still have a poor prognosis, which calls for urgent novel therapies. The immune system plays a dual role: both host-protecting and "tumor-promoting." Hence, immunotherapy is potentially a powerful weapon to help NEN patients. However, although recent successes with checkpoint inhibitors have shown that enhancing antitumor immunity can be effective, the dynamic nature of the immunosuppressive tumor microenvironment presents significant hurdles to the broader application of these therapies. Studies led to their approval in NEN of the lung and Merkel cell carcinoma, whereas results in other settings have not been so encouraging. Oncolytic viruses can selectively infect and destroy cancer cells, acting as an in situ cancer vaccine. Moreover, they can remodel the tumor microenvironment toward a T cell-inflamed phenotype. Oncolytic virotherapy has been proposed as an ablative and immunostimulatory treatment strategy for solid tumors that are resistant to checkpoint inhibitors alone. Future efforts should focus on finding the best way to include immunotherapy in the GEP-NEN treatment scenario. In this context, this study aims at providing a comprehensive generalized review of the immune checkpoint blockade and the oncolytic virotherapy use in GEP-NENs that might improve GEP-NEN treatment strategies.

Efficacy of a third-generation oncolytic herpes simplex virus in refractory soft tissue sarcoma xenograft models

Malignant soft tissue tumors, particularly highly malignant leiomyosarcomas, are resistant to chemotherapy and associated with a poor prognosis. T-01, a third-generation genetically modified herpes simplex virus type 1, replicates in tumor cells alone and exerts a cell-killing effect. The current study aimed to investigate the antitumor effect of T-01, which is a novel treatment for leiomyosarcoma. In vitro, six human cell lines and one mouse sarcoma cell line were assessed for T-01 cytotoxicity. In vivo, the efficacy of T-01 was examined in subcutaneously transplanted leiomyosarcoma (SK-LMS-1) cells and subcutaneously or intraperitoneally transplanted mouse sarcoma (CCRF S-180II) cells. Cytokines were assessed using ELISpot assay with splenocytes from the allogeneic models for immunological evaluation. T-01 showed cytotoxicity in all seven cell lines (p < 0.001). In the SK-LMS-1 xenotransplantation model, tumor growth was suppressed by T-01 administration (p = 0.02). In the CCRF S-180II subcutaneous tumor model, bilateral tumor growth was significantly suppressed in the T-01-treated group compared with the control group (p < 0.001). In the peritoneal dissemination model, T-01 treatment caused significant survival prolongation compared with the control (p < 0.01). In conclusion, third-generation genetically modified herpes simplex virus type 1 may be an effective novel therapy against refractory sarcomas.

Advances in the Diagnosis and Therapeutic Management of Gastroenteropancreatic Neuroendocrine Neoplasms (GEP-NENs)

Neuroendocrine neoplasms (NENs) are an increasingly common cause of neoplastic diseases. One of the largest groups of NENs are neoplasms localized to the gastroenteropancreatic system, which are known as gastroenteropancreatic NENs (GEP-NENs). Because of nonspecific clinical symptoms, GEP-NEN patient diagnosis and, consequently, their treatment, might be difficult and delayed. This situation has forced researchers all over the world to continue progress in the diagnosis and treatment of patients with GEP-NENs. Our review is designed to present the latest reports on the laboratory diagnostic techniques, imaging tests and surgical and nonsurgical treatment strategies used for patients with these rare neoplasms. We paid particular attention to the nuclear approach, the use of which has been applied to GEP-NEN patient diagnosis, and to nonsurgical and radionuclide treatment strategies. Recent publications were reviewed in search of reports on new strategies for effective disease management. Attention was also paid to those studies still in progress, but with successful results. A total of 248 papers were analyzed, from which 141 papers most relevant to the aim of the study were selected. Using these papers, we highlight the progress in the development of diagnostic and treatment strategies for patients with GEP-NENs.

Oncolytic virotherapy with human telomerase reverse transcriptase promoter regulation enhances cytotoxic effects against gastric cancer

Currently, gastric cancer is the third most common cause of cancer-associated mortality worldwide. Oncolytic virotherapy using herpes simplex virus (HSV) has emerged as a novel therapeutic strategy against cancer. Telomerase is activated in >90of malignant tumors, including gastric cancer, and human telomerase reverse transcriptase (hTERT) is one of the major components of telomerase enzyme. Therefore, in oncolytic HSV, placing the essential genes under the regulation of the hTERT promoter may enhance its antitumor efficacy. The present study examined the antitumor effect of fourth-generation oncolytic HSVs, which contain the ICP6 gene under the regulation of the hTERT promoter (T-hTERT). To examine the association between hTERT expression and prognosis in patients with gastric cancer, immunohistochemical analysis of resected tumor specimens was performed. The enhanced efficacy of T-hTERT was determined in human gastric cancer cell lines in vitro and in human gastric adenocarcinoma specimens in vivo. In in vitro experiments, enhanced cytotoxicity of T-hTERT was observed in MKN1, MKN28 and MKN45 cells compared with that of a third-generation oncolytic HSV, T-null. In particular, the cytotoxicity of T-hTERT was markedly enhanced in MKN45 cells. Furthermore, in vivo experiments demonstrated that 36.7 and 54.9% of cells were found to be lysed 48 h after infection with T-null or T-hTERT viruses at 0.01 pfu/cell, respectively. The T-hTERT-treated group exhibited considerably lower cell viability than the control [phosphate-buffered saline (-)] group. Therefore, employing oncolytic HSVs that contain the ICP6 gene under the regulation of the hTERT promoter may be an effective therapeutic strategy for gastric cancer. To the best of our knowledge, the present study was the first to describe the effect of an oncolytic HSV with ICP6 expression regulated by the hTERT promoter on gastric cancer cells.

Drug Development in Neuroendocrine Tumors: What Is on the Horizon?

OPINION STATEMENT

Neuroendocrine neoplasms (NENs) constitute a heterogenous group of malignancies. Translational research into NEN cell biology is the cornerstone for drug development strategies in this field. Somatostatin receptor type 2 (SSTR2) expression is the hallmark of well-differentiated neuroendocrine tumors (NETs). Somatostatin analogs and peptide receptor radionuclide therapy (PRRT) form the basis of anti-SSTR2 treatment onto new combination strategies, antibody-drug conjugates and bispecific antibodies. Classical pathways involved in NET development (PI3K-Akt-mTOR and antiangiogenics) are reviewed but new potential targets for NET treatment will be explored. Epigenetic drugs have shown clinical activity in monotherapy and preclinical combination strategies are more than attractive. Immunotherapy has shown opposite results in different NEN settings. Although the NOTCH pathway has been targeted with disappointing results, new strategies are being developed. Finally, after years of solid preclinical evidence on different genetically engineered oncolytic viruses, clinical trials for refractory NET patients are now ongoing.

Oncolytic virotherapy with SOCS3 enhances viral replicative potency and oncolysis for gastric cancer

Oncolytic virotherapy is an encouraging treatment using herpes simplex virus (HSV) for gastric cancer patients. To treat gastric cancer, we generated and evaluated the efficacy of an attractive type of oncolytic HSV expressing the suppressor of cytokine signaling 3 (SOCS3). We constructed a third-generation type of oncolytic HSV (T-SOCS3) arming with SOCS3 by a bacterial artificial chromosome (BAC) system. We examined the viral replicative intensification and oncolysis of T-SOCS3 for human gastric cancer cell lines ex vivo. T-SOCS3 enhanced its replication and potentiated its cell-killing effect for MKN1 human gastric cancer cell lines, which are resistant to a non-armed third-generation type of oncolytic HSV (T-01) ex vivo. T-SOCS3 also induced the destruction within human gastric cancer specimens. Armed oncolytic HSVs expressing SOCS3 may be an efficacious therapeutic agent for gastric cancer treatment.

Oncolytic Adenovirus CD55-Smad4 Suppresses Cell Proliferation, Metastasis, and Tumor Stemness in Colorectal Cancer by Regulating Wnt/β-Catenin Signaling Pathway

During the past few decades, colorectal cancer (CRC) incidence and mortality have significantly increased, and CRC has become the leading cause of cancer-related death worldwide. Thus, exploring novel effective therapies for CRC is imperative. In this study, we investigated the effect of oncolytic adenovirus CD55-Smad4 on CRC cell growth. Cell viability assay, animal experiments, flow cytometric analysis, cell migration, and invasion assays, and Western blotting were used to detect the proliferation, apoptosis, migration, and invasion of CRC cells. The oncolytic adenovirus CD55-Smad4 was successfully constructed and effectively suppressed CRC cell proliferation in vivo and in vitro. Notably, CD55-Smad4 activated the caspase signaling pathway, inducing the apoptosis of CRC cells. Additionally, the generated oncolytic adenovirus significantly suppressed migration and invasion of CRC cells by overexpressing Smad4 and inhibiting Wnt/β-catenin/epithelial-mesenchymal transition (EMT) signaling pathway. Moreover, CRC cells treated with CD55-Smad4 formed less and smaller spheroid colonies in serum-free culture than cells in control groups, suggesting that CD55-Smad4 suppressed the stemness of CRC cells by inhibiting the Wnt/β-catenin pathway. Together, the results of this study provide valuable information for the development of a novel strategy for cancer-targeting gene-virotherapy and provide a deeper understanding of the critical significance of Smad4 in gene therapy of CRC.

Herpes Simplex Virus Oncolytic Immunovirotherapy: The Blossoming Branch of Multimodal Therapy

Oncolytic viruses are smart therapeutics against cancer due to their potential to replicate and produce the needed therapeutic dose in the tumor, and to their ability to self-exhaust upon tumor clearance. Oncolytic virotherapy strategies based on the herpes simplex virus are reaching their thirties, and a wide variety of approaches has been envisioned and tested in many different models, and on a range of tumor targets. This huge effort has culminated in the primacy of an oncolytic HSV (oHSV) being the first oncolytic virus to be approved by the FDA and EMA for clinical use, for the treatment of advanced melanoma. The path has just been opened; many more cancer types with poor prognosis await effective and innovative therapies, and oHSVs could provide a promising solution, especially as combination therapies and immunovirotherapies. In this review, we analyze the most recent advances in this field, and try to envision the future ahead of oHSVs.

The efficacy of a third-generation oncolytic herpes simplex viral therapy for an HPV-related uterine cervical cancer model

PURPOSE

Cervical cancer is the fourth most common cancer in women and the seventh most common of all human cancers. Development of new treatments is mandatory to improve the outcome of this disease. Replication-selective oncolytic herpes simplex viruses (HSVs) have emerged as a new platform for cancer therapy. The therapeutic potential of a triple-mutated oncolytic HSV (T-01) for human papillomavirus (HPV)-related cervical cancer was evaluated with immunodeficient and immune-complete models.

METHODS

(1) The in vitro efficacy of T-01 on human cervical cancer cell lines, TC-1, HeLa, CaSki, and SKG IIIa was evaluated. (2) The in vivo efficacy of T-01 was examined in human HeLa xenograft and TC-1 syngeneic models of human cervical cancer. After flank tumors reached 5 mm in diameter, the first intratumoral (i.t.) administration of T-01 was performed. Intratumoral administration of T-01 was performed with a 5 day interval a total of 6 times.

RESULTS

In the in vitro study, T-01 was highly cytotoxic for all cell lines (48 h after infection with T-01 at 1 × 10⁵ PFU, T-01 killing HeLa: 67.5%, Caski: 62.8%, SKG IIIa: 43.2%). Furthermore, in the human HeLa xenograft and TC-1 syngeneic models, T-01 resulted in a significant reduction of tumor growth. In addition, tumor-bearing mice treated with T-01 showed significantly increased numbers of CD8 + T-cells precursors than the control mice (p = 0.03).

CONCLUSIONS

These results demonstrate that T-01 has cytotoxic efficacy and inhibited against HPV-related cervical cancer cells. These findings indicate that T-01 has therapeutic potential for HPV-related cervical cancer.