Combination of temozolomide and oncolytic viral therapy potentiates apoptosis and inhibits cell migration of glioblastoma in vitro

Background. Glioblastoma (GBM) is the most aggressive and malignant type of glioma, representing the most common and lethal primary central nervous system (CNS) neoplasm in adults. Despite current therapeutic approaches, the median overall survival remains low. Oncolytic virotherapy is a highly promising alternative strategy. One such approach utilizes the Herpes Simplex Virus Thymidine Kinase (HSV-TK) enzyme combined with the prodrug ganciclovir (GCV). This TK-GCV system is converted into a toxic metabolite that induces apoptosis in target cells. Combining the TK-GCV system with temozolomide (TMZ), the standard first-line chemotherapeutic agent for glioma, targets two critical survival mechanisms of GBM: DNA repair and apoptosis regulation. This combination has the potential to significantly improve therapeutic efficacy.

Aim. We evaluated the impact of combined TK-GCV and TMZ therapy on glioblastoma cell viability and migratory capacity in vitro.

Material and Methods. This work employed the following cell lines: GBM cell lines U87-MG and U251-MG, HEK293T/17 cells, and human mesenchymal stem cells. Recombinant viral particles encoding the thymidine kinase (TK) gene were generated using genetic engineering techniques. Optimal concentrations of TMZ and GCV were determined. Cell viability was assessed using the MTT assay; cell cycle distribution (G2/M phase) and Bax expression were analyzed by flow cytometry; gene expression was quantified via quantitative PCR (qPCR); and cell migration was measured using a wound-healing assay.

Results. The combination of TMZ and the TK-GCV system results in a significant increase in GBM cell death compared to monotherapy. Specifically, this enhanced cell death is characterized by a higher proportion of apoptotic cells. Furthermore, expression levels of EMT markers such as CD44, ZEB1, SNAI1, SNAI2, and VIM were significantly reduced under the combined treatment of TK-GCV and TMZ.

Conclusion. The combination of TK-GCV and TMZ demonstrates a synergistic effect between the two therapeutic approaches. Compared to each method administered separately, the combined treatment results in increased GBM cell death and reduced cell migration.

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