TUMOR REDUCTION IN-VIVO AFTER ADENOVIRAL MEDIATED GENE-TRANSFER OF THE HERPES-SIMPLEX VIRUS THYMIDINE KINASE GENE AND GANCICLOVIR TREATMENTIN HUMAN HEAD AND NECK SQUAMOUS-CELL CARCINOMA

Gene transfer offers the possibility of novel therapies for head and n eck squamous cell carcinoma (HNSCC), To this end, we demonstrate that a replication deficient adenovirus vector (Ad.RSVlacZ) can efficiently transduce foreign genes into human HNSCC cell lines in vitro, and tha t adenoviral mediated transfer of herpes simplex virus thymidine kinas e (Ad.RSVtk) followed by exposure to ganciclovir results in tumor cell killing in vitro and in vivo. Exposure to Ad.RSVlacZ resulted in lacZ expression at multiplicities of infection (MOIs) of 10 and 100 for th e cell lines HEp-2 and FaDu, respectively. This increased to 97% (HEp- 2) and 49% (FaDu) at an MOI of 10,000. For HEp-2, maximum expression o ccurred during the first 48 hours after exposure (52% at 24 hours, 48% at 48 hours; MOI 500), then declined by 40% per day, This rapid decli ne may be caused by dilution of the gene through cell proliferation, b ecause normalizing for the increase in total protein shows that the to tal number of cells expressing lacZ is stable from days 1 to 4. FaDu a nd HEp-2 were then transduced by AD.RSVtk and exposed to 20 mu M ganci clovir for 24 hours. Significant tumor cell killing, as measured by a colony forming assay, occurred at an MOI of 2 for HEp-2 and 20 for FaD u, At an MOI of 200, 100% of HEp-2 and 97% of FaDu cells were killed, Next, subcutaneous tumor nodules derived from FaDu and HEp-2 were esta blished in the flanks of SCID mice. Direct intratumoral injection of A d.RSVtk followed by 7 days of ganciclovir therapy resulted in an adeno virus dose dependent reduction of tumor growth, and an actual size red uction of established tumor nodules at the highest does (10(10) plaque forming units), In conclusion, an adenovirus vector can efficiently t ransduce HNSCC cell lines in vitro. Maximum marker gene expression occ urred during the first 48 hours after transduction, Transduction by Ad .RSVtk followed by exposure to ganciclovir resulted in tumor cell kill ing in vitro and in vivo.