TNF-α deficiency as protection against sickness behavior related to external beam radiation of the pelvis in mice.

208 Background: Prostate cancer patients undergoing localized external beam radiation therapy (EBRT), experience significant fatigue during treatment, which can affect physical functioning and QOL. We hypothesize that cancer treatment related fatigue (CTRF) is the same as sickness behavior caused, in part, by increases in TNF-α. Our previous data demonstrate that pelvic EBRT induces systemic increases in TNF-α and a decline in voluntary wheel running activity (VWRA) , an objective measure of sickness in mice. A specific aim of this study was to determine the requirement of EBRT for TNF-α for the induction of sickness behavior. Methods: Daily VWRA was monitored in male WT (n=10) and TNF-α−/− (n=10) anesthetized mice undergoing pelvic EBRT at 4.6 Gy/fraction, 5 days per week for 15 fractions for a total dose of 69 Gy [4.6 X 15 = 69, not 70]. Control WT (n=10) and TNF-α−/− (n= 10) mice underwent anesthesia followed by sham EBRT. The effect of treatment on weight and food intake was also determined by calculating change in weight and daily food intake during treatment. A 2 x 2 repeated measure analysis of covariance ANCOVA was used to determine whether there was a significant interaction between treatment group (EBRT or Control) and genotype (WT or TNF-α−/−) on voluntary wheel running activity controlling for baseline differences in this variable. Similarly a 2 x 2 ANOVA was used to determine whether there was a drug x genotype interaction between change in body weight or food intake. Results: There was a significant effect of EBRT on VWRA (p< 0.001), food intake (p0.002), and weight (p<0.001). We did not however observe a significant interaction between EBRT and genotype in VWRA (p= 0.756), food intake (p=0.654), or weight (p= 0.450). Conclusions: Targeting TNF-α using specific cytokine blocking agents has been suggested as a potential strategy for preventing or managing EBRT related fatigue. Although our prior data support that localized EBRT to the pelvis may induce TNF-α and sickness behavior in mice, our latest data do not support a direct role for this cytokine in mediating these effects.