therapeutic agents including ionizing radiation. Cyclooxygenase-2 (COX-2) inhibition has become an attractive target forenhancing the efficacy of radiation and chemotherapy. Numerous mechanistic pathways have been proposed as the meansthrough which COX-2 inhibition enhances the efficacy of radiation. We hypothesize that the COX-2 inhibitor nimesulide willimprove the efficacy of radiation therapy (RT) via the suppression of the NF-B mediated cytoprotective pathways.

Materials/Methods: In this study we used the COX-2 inhibitor nimesulide to improve the efficacy of RT when measured bytumor regrowth assays in vivo and clonegenic survival in vitro. For the in vivo assay A549 tumor cells representing NSCLCwere subcutaneously injected into the right flank of female athymic nude mice (n � 10/group). Mice were given nimesulide viadrinking water at a concentration of 5 and 10�g/g body weight (b.w.) where the water was replenished every day and tumors weremeasured biweekly. For our in vitro study, clonegenic survival assays were evaluated to determine the effect of nimesulide, radiation,and the combination. The mechanism by which nimesulide improved the efficacy of radiation treatment was measured by Westernblot analysis of NF-B target genes. A detailed time course of 1–48 h was performed to determine the effect of nimesulide alone aswell as a combination of nimesulide concentrations from 100–300�M with x-radiation doses of 3 and 6 Gy.

Results: In vivo, mice that received combined treatments of 5�g/g b.w. nimesulide and 30 Gy radiation (3 Gy/fraction, 10 days)had significant reduction in tumor size in comparison to the 30 Gy radiation control group (p � 0.05). Whereas nimesulide at10�g/g b.w. showed no significant change in comparison to radiation alone. In vitro nimesulide alone produced a significantdecrease in clonegenic survival at doses from 300–500�M. When combined, nimsulide demonstrated an additive effect incombination with radiation. Nimesulide alone reduced MnSOD protein levels. Radiation at 3 and 6 Gy caused and elevationof MnSOD protein levels which was inhibited by prior treatment of nimesulide suggesting an inhibition of radiation inducedNF-B target genes.

Conclusions: These results support the hypothesis that COX-2 inhibitors like nimesulide can increase the efficacy of radiationtherapy. Interestingly, the lower dose of nimesulide increased the in vivo efficacy of RT whereas the higher dose produced noeffect when compared to radiation alone. In vitro, our results suggest that the radiosensitization of A549 tumor cells bynimesulide is mediated by the suppression of NF-B radiation-induced cytoprotective genes.

2051 Waterbath Versus Ultrasound Hyperthermia In Vivo: Implications for Clinical Hyperthermia

N. Thompson,1 A. Zeug,1 J. Allan,1 J. Locke1

1Radiation Oncology, Washington University School of Medicine, Saint Louis, MO

Purpose/Objective: Ultrasound is utilized clinically for both superficial and deep hyperthermia. In contrast, in vivo experi-mentation has primarily utilized waterbath limb immersion. We determined the response of xenotransplants to waterbathimmersion versus focal ultrasound hyperthermia using immunhistochemistry, histopathology, and tumor growth delay assays. Wealso assessed thermal dosimetry of ultrasound hyperthemia and compared the local, regional, and systemic temperature changes.

Materials/Methods: Nu/Nu mice were used with institutional approval. A suspension of2 x 10∧ 6 HeLa cells were injected in the bilateral proximal thigh of mice. Each mouse was inoculated with two tumors grown

to an average of 350mm∧ 3. Mice were randomly divided into treatment groups (41 C or 43 C for 60 min, and ultrasound orwaterbath treatment delivery) or control (untreated) for tumor growth delay. Waterbath (WB) hyperthermia was given via limbimmersion. Ultrasound (US) hyperthermia was given via a 1cm portal using the SAHUS system. Temperature was controlledvia a feedback loop between the thermometry units and a personal computer running customized software. Hsp70 western andTUNEL analysis were performed 18 hours following hyperthermia treatment. Tumor growth was assessed a minimum of twiceweekly with digital calipers.

Results: Consistency of hyperthermia delivery was demonstrated with both WB and US. Intratumoral probe measuredtemperatures of 43.0 C � 0.4 C and 41.0 C � 0.5 C for animals prescribed to receive 43 C or 41 C US respectively.Contralateral unheated tumor temperature in SAHUS treated animals varied a maximum of 0.9 C from baseline. Intratumortemperature with 43 C waterbath was 40.8 � 0.4 C with contralateral tumor varying 2 to 5 C higher. Rectal temperatures (32C) in ultrasound treated mice did not vary more than 1 C from baseline while animals treated with 43 C WB averaged 34.2 �0.9 C. TUNEL analysis demonstrated significant differences (p � 0.027) between ultrasound and waterbath treatment of tumorsat 43 C. Conversely, contralateral (non-treated) tumors in animals receiving 43 C demonstrated no significant differencesbetween modalities. Western blot analysis revealed increased hsp70 induction at 43 C in waterbath versus focal ultrasoundhyperthermia. T-tests revealed significant differences in tumor growth delay between tumors heated with waterbath versusultrasound at 43 but not at 41 C. No animal was removed from analysis due to toxicity of treatment. Thermal dosimetry duringUS showed average of three independent probes placed 5mm from central axis was 42.6 C � 0.5 C.

Conclusions: Consistent US hyperthermia can be achieved throughout a typical xenotransplanted tumor. Local versus systemiceffects of hyperthermia may be involved in tumor growth delay. Waterbath hyperthermia demonstrated greater local responsedespite lower intratumoral temperature measurements. The mildly elevated systemic temperature’s occurring during WB, andthe concurrent improved response, may be an important consideration for clinical trials of hyperthermia.

2052 Radiation Damage Protection by the Benzyl Styrl Sulfone Analog, Ex-Rad

A. A. Alfieri,1 L. Liu,1 A. Sharma,1 G. Gorla,1 S. Bell,2,3 R. M. Ramana,2 S. Cosenza,2 P. E. Reddy,2 C. Guha1

1Radiation Oncology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, 2Fels Institute forCancer Research, Philadelphia, PA, 3Onconova Therapeutics, Inc., Princeton, NJ

Purpose/Objective: To date, there is no effective orally available prophylactic drug to ameliorate radiation injury afteraccidental exposure to ionizing irradiation. Currently available agents have inherent toxicities. Benzyl styryl sulfones are afamily of drugs that exhibit inhibitory properties to a variety of protein kinases, such as cyclin-dependent kinases, therebyarresting cycling cells at cell cycle checkpoints. In these studies, we investigated the protective effects of a water-soluble, orallyavailable, benzyl sulfone analog (Novonex/Ex-Rad) after total body irradiation of mice.

Materials/Methods: The 4-carboxystyrl-4-chlorobenzylsulfone (ON 01210, Novonex/Ex-Rad) is stable at pH 7.6 to 2.5mg/mlfinal concentration in PBS. A dose escalating toxicity, pharmacokinetic and tissue distribution assay was performed in C57Bl/6

S367Proceedings of the 46th Annual ASTRO Meeting