Zika Virus: A Novel Oncolytic Strategy Against Neuroblastoma in Children


Neuroblastoma, a formidable adversary in pediatric oncology, is a cancer that originates along the sympathetic nervous system and adrenal glands. It stands out as the most common extracranial solid tumor and the leading malignancy in infants. Despite constituting only 6% of all childhood cancers, it is responsible for a striking 15% of childhood cancer-related deaths in the United States.

The standard treatments, including surgery, radiotherapy, and chemotherapy, often fall short, especially in 60%-70% of high-risk neuroblastoma cases. These treatments are fraught with severe complications like growth retardation, renal impairment, and thyroid dysfunction, among others. Unfortunately, the long-term survival rate for patients with high-risk neuroblastoma remains below 40%.

This cancer exhibits complex heterogeneity, with survival prognosis influenced by factors such as age at diagnosis, tumor site, grade, histology, and the amplification of the MYCN gene. The latter, present in about 25% of cases, is a pivotal biomarker for high-risk neuroblastoma, closely associated with advanced disease and poor survival outcomes. Despite two decades of research, there has been minimal improvement in survival rates for children with MYCN-amplified neuroblastoma.

In the quest for better treatment approaches, oncolytic therapies have garnered attention. These involve repurposing viruses, including hepatitis, Epstein-Barr, and adenovirus, to exploit their oncolytic properties. The FDA-approved T-VEC, a modified herpes simplex virus, for certain melanoma cases, exemplifies this approach’s potential.

A groundbreaking development in this domain is the emergence of the Zika virus (ZIKV) as an oncolytic agent. Belonging to the Flaviviridae family, ZIKV primarily causes mild symptoms, with a significant portion of infections being asymptomatic. Its predilection for infecting neuronal progenitor cells, which was revealed during investigations into maternal-fetal ZIKV syndrome, paved the way for its use in targeting cancers with a central nervous system background, such as glioblastoma and glioma. Our studies have notably demonstrated the profound sensitivity of neuroblastoma cells to ZIKV, specifically linked to the expression of the CD24 membrane protein.

CD24, a glycophosphatidylinositol-linked sialoglycoprotein, varies significantly in glycosylation across cell types. It’s found on progenitor and metabolically active cells, including hematopoietic and neural cells, and is implicated in tumor progression and poor prognosis in various cancers. It’s a biomarker for neural stem cell differentiation and plays a critical role in neural development. Interestingly, CD24 is commonly expressed in neuroblastomas, linking it to tumor differentiation and anaplastic features.

Our study focused on the oncolytic effects of ZIKV on neuroblastoma using in vivo models, including high-risk MYCN-amplified and non-amplified tumors. The results were promising, showing a significant tumoricidal effect and survival advantage, correlating with CD24 expression in the tumors. This highlights the dual role of CD24 in tumor proliferation and as a predictor of ZIKV permissiveness, offering a new avenue for alternative therapies in primary and multidrug-resistant neuroblastoma cases.

Materials and Methods

The study utilized various cell lines, including SK-N-AS and IMR-32, cultured under specified conditions. ZIKV experiments used the MR766 strain, with preparation methods tailored for both in vitro and in vivo studies. Tissue Microarray Staining was employed to analyze neuroblastoma and peripheral nerve tissue, using specific antibodies and imaging techniques.

In vivo, the study involved the use of NCr nude athymic mice, with tumor studies conducted on various cell lines. Tumor growth and response to treatments were meticulously monitored, and the experiments adhered to strict ethical guidelines.

CD24 expression’s role was further elucidated through the construction of IMR-32 cells stably expressing CD24 short hairpin RNA, with subsequent validation using qRT-PCR and Western blot analysis. The sensitivity of these modified cells to ZIKV was assessed using cytotoxicity assays.

Discussion: The Oncolytic Potential of Zika Virus in Neuroblastoma Treatment

Selective Oncolytic Effects of ZIKV

The potential of the Zika virus (ZIKV) as an oncolytic agent has been a subject of increasing interest, particularly in the context of neuroblastoma treatment. Previous studies have demonstrated ZIKV’s selective oncolytic effects in various human central nervous system (CNS) tumors. These findings indicate a unique sensitivity profile, distinguishing between different types of CNS cancers and sparing normal neuronal cells, unlike other neurotropic flaviviruses like West Nile virus.

Differential Sensitivity and T-Cell Recruitment

The differential sensitivity of tumors to ZIKV has raised questions about the underlying mechanisms. For instance, T-cell infiltration and recruitment have been proposed as factors contributing to ZIKV’s specificity. However, this explanation falls short in accounting for the observed in vitro sensitivity and in animal models lacking functional T cells. Additionally, studies have linked the modulation of the Wnt/β-catenin signaling pathway to ZIKV-mediated cytotoxicity in various cancers, though these results have been inconsistent.

CD24 Expression and ZIKV Specificity

Our research, along with collaborative studies, has identified a connection between CD24 expression, ZIKV specificity, and the regulation of intracellular antiviral pathways like type I IFN and NFκB. These findings highlight the role of CD24 in the selective targeting of neuroblastoma cells by ZIKV. However, further in vivo confirmation of these results is necessary.

ZIKV in Neuroblastoma Tumors

Our study characterizes the oncolytic effects of ZIKV on neuroblastoma tumors. Employing an intratumoral introduction method, we found this approach effective in eliminating tumor masses in high-risk MYCN-amplified and non-amplified neuroblastoma, as well as in primary and recurrent isolates. Notably, no adverse effects were observed in experimental animal subjects, even several weeks post-administration.

CD24 Expression and Tumor Permissiveness

Our findings also correlate with the discovery that CD24 expression influences ZIKV sensitivity. Considering that CD24 is typically expressed on differentiating cells and abandoned upon terminal differentiation, its robust expression in neuroblastoma tumors is consistent with their undifferentiated nature. This suggests that CD24 may not only drive tumor proliferation but also indicate susceptibility to ZIKV.

Modulation of CD24 in Neuroblastoma

By modulating CD24 expression in vivo, we observed that its upregulation conferred a significant growth advantage to neuroblastoma cells, with a corresponding increase in sensitivity to ZIKV. This was particularly evident in SK-N-AS tumors, where exogenous CD24 expression led to a marked increase in tumor mass and sensitivity to ZIKV.

Implications for Oncolytic Therapy

Our study underscores the efficacy of ZIKV in inducing a rapid tumoricidal effect on solid neuroblastoma tumors, without recurrence or adverse effects to the host. This positions ZIKV as a promising alternative or adjunctive therapy in neuroblastoma treatment, particularly for tumors expressing CD24. Furthermore, the potential application of ZIKV therapy extends beyond pediatric neuroblastoma to include a range of adult cancers exhibiting CD24 expression.

Future Directions

The unique sensitivity profile of ZIKV, combined with the absence of significant side effects, opens new avenues for oncolytic virus therapy in cancer treatment. Further exploration of ZIKV’s mechanism of action and its interaction with tumor-specific markers like CD24 will be crucial in developing more effective and targeted therapies for neuroblastoma and other cancers.

Reference link : https://aacrjournals.org/cancerrescommun/article/4/1/65/732575/The-Oncolytic-Activity-of-Zika-Viral-Therapy-in


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