hydrogel reservoir unlocks the potential of HSV-1 virotherapy in cancer

In a recent study published in Communications Biologythe researchers evaluated the therapeutic efficacy of Navoximod, combined with herpes simplex virus 1 (HSV-1) virus therapy, against hepatocellular carcinoma (HCC).

Study: Navoximod modulates local HSV-1 replication to reshape the tumor immune microenvironment for enhanced immunotherapy via an injectable hydrogel. Image Credit: PaeGAG/Shutterstock.com

Background

Cancer immunotherapy has achieved tremendous success in treating various cancers. However, the HCC threatens the effectiveness of immunotherapeutics due to low response rates and adverse outcomes due to the complex and potently immunosuppressive tumor microenvironment (TME). Thus, new strategies are needed to improve HCC outcomes.

Oncolytic virotherapy can destroy tumor cells and generate generalized antitumor immune responses. However, it has limited efficacy in humans due to impaired viral replication and inability to overcome TME.

Antitumor immunological activation and antiviral immunological suppression must be carefully modulated and balanced to optimize virus-based therapies.

The protein indoleamine 2, 3-dioxygenase 1 (IDO1) is an essential immunosuppressive molecule that is thought to be upregulated in multiple tumors. IDOI inhibits cytotoxics [natural killer (NK) and cluster of differentiation 8-expressing (CD8+)] T cells and lymphocytes, improves regulation T-cell (Treg) and facilitates the recruitment of myeloid suppressor cells (MDSC) by accelerating the conversion of tryptophan to kynurenine. Studies have reported that IDO1 inhibitors are effective options for immunotherapy.

About the study

The present study investigated whether Navoximod, an indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor, could boost HSV-1 therapy and improve HCC outcomes.

The team loaded Navoximod and HSV-1 into an injectable, biocompatible hydrogel for local drug delivery and maximized HCC viral delivery for virotherapy. They performed single-cell ribonucleic acid sequencing (scRNA-seq) to assess immunological profiles at the tumor site.

The study then explored interferon-stimulated genes (ISGs) that inhibit HSV-1 proliferation to optimize HSV-1-based oncolytic immunotherapy.

Green fluorescent protein (GFP) signals generated from GFP-tagged HSV-1 were also used to assess HSV-1 multiplication. Additionally, quantitative polymerase chain reaction (qPCR) and Western blot analyzes were performed to assess IDO1 levels in Hepa1-6 cells after HSV-1 treatment.

The impact of Navoximod on HSV-1 multiplication was verified using SMMC-7721 cells (human hepatocellular carcinoma), 4T1 cells (murine breast cancer) and live using the VX-2 rabbit liver cancer model.

Silk hydrogels were generated from cocoons to deliver oncolytic virus. Scanning electron microscopy (SEM) and confocal microscopy (CFM) were performed to assess hydrogel porosity and virion distribution.

The team measured HSV-1 deoxyribonucleic acid (DNA) levels in the nervous system, blood and peripheral organs after subcutaneous injections of the hydrogel to assess their cytotoxicity.

Tumor sections were stained using hematoxylin and eosin (H&E), TUNEL and Ki67 stains to assess cytolytic damage to tumor tissues. Flow cytometry (FC) analysis and immunohistochemical (IHC) staining were performed to confirm systemic TME changes.

Results

RNA-seq results indicated that IDO1 was overexpressed in HCC, based on the Cancer Genome Atlas (TCGA) dataset. Navoximod promoted HSV-1 multiplication and herpes simplex virus 1-induced oncolysis in tumor cells and, therefore, may be an effective treatment option when combined with viral oncolytic therapy based on herpes simplex virus 1.

With a single injection, the hydrogel developed a regional depot to maximize viral reproduction and dissemination at the tumor site.

Of note, the hydrogel prolonged the disease-free life of mice with HCC, protected them from tumor recurrence, and was effective in the rabbit orthotopic liver tumor model. Mechanically, HSV-1 virotherapy and IDO1 inhibition, when combined, completely reprogrammed the tumor microenvironment via scRNA sequencing.

The hydrogel served as a reservoir for regional delivery, allowing HSV-1 to maintain its cytotoxic activity and spread to the tumor site while reducing off-target damage to peripheral organs. The method produced complete treatment responses in HCC subcutaneous malignancies, but HSV-1 or HSV-1/Navoximod mixtures without being incorporated into the hydrogels produced only slight responses.

The hydrogel could counteract the immunosuppressive tumor microenvironment by modifying the population of immune cells mainly comprising effector memory (EM) and accumulation of NK T cells. Upregulation of IDO1 inhibited HSV-1 proliferation, as indicated by levels of HSV DNA and gD envelope proteins.

Results were consistently observed using 4T1 and SMMC-7721 cells. IDO1 was found to be overproduced in tumor tissues and further increased by herpes simplex virus-1 therapy, acting as a form of negative feedback to inhibit herpes simplex virus-1 proliferation in tumor cells. cancer cells.

Myeloid-derived cells (M1 macrophages, monocytes and dendritic cells) and T/NK cells mainly infiltrated the tumor site.

Reverse transcription PCR indicated that hydrogel treatment upregulated the CC chemokine ligand 2 (CCL-2) and CXC motif ligand (CXCL) -10 and -11 genes, following results of gene ontology (GO) enrichment analysis. IDO1 suppressed anti-tumor immunity, implying that IDO1 must be blocked during herpes simplex virus-1 immunotherapy.

The hydrogel rapidly eradicated tumor recurrence by inducing a conversion of naïve and central memory (CM) T cells into effector memory (EM) T cells. Given its efficacy, biosafety and low systemic toxicity, it has shown promising potential as an oncolytic virus delivery route.

Conclusion

Study results showed that the combination of Navoximod with HSV-1 could stimulate viral replication and remodel the TME for tumor eradication through the hydrogel reservoir.

Navoximod enhanced the oncolytic and replicative effects of herpes simplex virus-1 in vitro And live and need to be further investigated to develop new strategies and reduce the global cancer burden.