Antitumoral effects of defective herpes simplex virus-mediated transfer oftissue inhibitor of metalloproteinases-2 gene in malignant glioma US7 in vitro: Consequences for anti-cancer gene therapy

We set up experiments to evaluate the effects of defective herpes simplex v irus (HSV)-mediated in vitro gene transfer of tissue inhibitor of metallopr oteinases-2 (TIMP-2) in malignant glioma cells. Intrinsic TIMPs are known t o be inhibitors of the strong invasive activities of matrix metalloproteina ses in malignant gliomas. The defective HSV vectors dvSRaTIMP2 was engineer ed to express human TIMP-2 (hTIMP-2) with a combination of replication-comp etent HSV mutant, temperature-sensitive HSVt5K, and amplicon plasmid-contai ning hTIMP-2. The hTIMP-2 gene was driven by the simian virus 40 promoter. The helper virus (HSV-tsK) was thermosensitive; consequently, this vector c ould proliferate only at 31.5 degrees C. After infection of U87 human gliob lastoma cells with the vector in vitro, expression of TIMP-2 was confirmed by reverse zymography. The U87 cells infected in vitro either with dvSRaTIM P2 or HSV-tsK were efficiently destroyed under replication-permissive condi tions (at 31.5 degrees C) and significantly lowered under replication-nonpe rmissive conditions (at 37 degrees C). The invasive activity of U87 was cle arly inhibited by dvSRaTIMP2 infection at both 31.5 degrees C and 37 degree s C. Our studies suggest that TIMP-2 expressing the defective HSV vector is possibly useful for the treatment of malignant brain tumors.