Oncolytic vaccinia virotherapy of anaplastic thyroid cancer in vivo.

CONTEXT

Anaplastic thyroid carcinoma (ATC) is a fatal disease with a median survival of only 6 months. Novel therapies are needed to improve dismal outcomes.

OBJECTIVE

A mutated, replication-competent, vaccinia virus (GLV-1h68) has oncolytic effects on human ATC cell lines in vitro. We assessed the utility of GLV-1h68 in treating anaplastic thyroid cancer in vivo.

DESIGN

Athymic nude mice with xenograft flank tumors of human ATCs (8505C and DRO90-1) were treated with a single intratumoral injection of GLV-1h68 at low dose (5x10(5) plaque-forming unit), high dose (5x10(6) plaque-forming unit), or PBS. Virus-mediated marker gene expression (luciferase, green fluorescent protein, and beta-galactosidase), viral biodistribution, and flank tumor volumes were measured.

RESULTS

Luciferase expression was detected 2 d after injection. Continuous viral replication within tumors was reflected by increasing luciferase activity to d 9. At d 10, tumor viral recovery was increased more than 50-fold as compared with the injected dose, and minimal virus was recovered from the lung, liver, brain, heart, spleen, and kidneys. High-dose virus directly injected into normal tissues was undetectable at d 10. The mean volume of control 8505C tumors increased 50.8-fold by d 45, in contrast to 10.5-fold (low dose) and 2.1-fold (high dose; P=0.028) increases for treated tumors. DRO90-1 tumors also showed significant growth inhibition by high-dose virus. No virus-related toxicity was observed throughout the study.

CONCLUSIONS

GLV-1h68 efficiently infects, expresses transgenes within, and inhibits the growth of ATC in vivo. These promising findings support future clinical trials for patients with ATC.