THE EFFECT OF COMBINING RECOMBINANT HUMAN TUMOR-NECROSIS-FACTOR-ALPHAWITH LOCAL RADIATION ON TUMOR-CONTROL PROBABILITY OF A HUMAN GLIOBLASTOMA-MULTIFORME XENOGRAFT IN NUDE-MICE

Purpose: To evaluate the antitumor activity of recombinant human tumor necrosis factor-alpha (rHuTNF-alpha)) on a human glioblastoma multifo rme (U87) xenograft in nude mice, and to study the effect of combining rHuTNF-alpha with local radiation on the tumor control probability of this tumor model. Methods and Materials: U87 xenograft was transplant ed SC into the right hindleg of NCr/Sed nude mice (7-8 weeks old, male ). When tumors reached a volume of about 110 mm(3), mice were randomly assigned to treatment: rHuTNF-alpha alone compared with normal saline control; or local radiation plus rHuTNF-alpha vs. local radiation plu s normal saline. Parameters of growth delay, volume doubling time, per centage of necrosis, and cell loss factor were used to assess the anti tumor effects of rHuTNF-alpha on this tumor. The TCD50 (tumor control dose 50%) was used as an endpoint to determine the effect of combining rHuTNF-alpha with local radiation. Results: Tumor growth in mice trea ted with a dose of 150 mu g/kg body weight rHuTNF-alpha, IP injection daily for 7 consecutive days, was delayed about 8 days compared to tha t in controls. Tumors in the treatment group had a significantly longe r volume doubling time, and were smaller in volume and more necrotic t han matched tumors in control group. rHuTNF-alpha also induced a 2.3 t imes increase of cell loss factor. The administration of the above-men tioned dose of rHuTNP-alpha starting 24 h after single doses of locali zed irradiation under hypoxic condition, resulted in a significant red uction in TCD50 from the control value of 60.9 Gy to 50.5 Gy (p < 0.01 ). Conclusion: rHuTNF-alpha exhibits an antitumor effect against U87 x enograft in nude mice, as evidenced by an increased delay in tumor gro wth as well as cell loss factor. Also, there was an augmentation of tu mor curability when given in combination with radiotherapy, resulting in a significantly lower TCD50 value in the treatment vs. the control groups.