Analgesic Effects Of Adenovirus-mediated IL-24 On The Rats With Tibia Cancer Pain

Objective:To observe the analgesic effect of adenovirus-mediated IL-24 (Ad-IL-24) on the SD rats with tibia cancer pain and explore the mechanism through which Ad-IL-24 plays its role in the model.Methods:Transfer constructed Ad-IL-24 (with a replication-incompetent adenovirus vector) and Ad-GFP into QBI-293A cells separately many times to acquire high concentration of adenovirus. The IL-24 transgene expression in Walker 256 cells mediated by adenovirus transfection was determined by reversed transcriptase-polymerase chain reaction (RT-PCR). The GFP expression was examined by fluorescence microscopy. The cytotoxic activity of Ad-IL-24 was determined on cycotoxicity to syngeneic walker 256 cells using MTT assay and flow cytometric analysis. The effect of Ad-IL-24 on the secretion ofβ-endorphin in vitro was determined by ELISA kits.Forty female SD rats weighing 180-200g were randomly divided into 5 groups (n=8 each): group I normal; group II PBS; group III Ad-GFP; group IV Ad-IL-24; group V zoledronic acid. On the eight days after the carcinoma cells inoculation, inject PBS, Ad-GFP, Ad-IL-24 and zoledronic acid subcutaneously e.o.d for three times to the operated legs, pain threshold was assessed on the day after the administration. Cut the operated legs then stain it with haematoxylin and erosion to visualize the structure of the tumor infiltration and the bone destruction, and test the plasma concentration of TNF-α,IL-6, β-endorphin,IFN-γon the fourteenth day after the cells inoculation.Results:A significant amount of IL-24 expression was found in Ad-IL-24 transfected Walker 256 carcinoma cells. Ad-IL-24 mediated cancer gene therapy demonstrated in vitro cytotoxicity to Walker 256 cells. Ad-IL-24 significantly up-regulates the secretion ofβ-endorphin in vitro. In vivo After repeated treatment with Ad-IL-24 or zoledronic acid, mechanical allodynia was attenuated compared with Ad or PBS group (p<0.05), whereas p>0.05 when Ad-IL-24 group compared with zoledronic acid group. No detectable difference of time course of thermal hyperalgesia was found among normal rats, PBS, Ad-GFP, Ad-IL-24 and zoledronic acid treated rats received live Walker 256 carcinoma cells. The concentration of TNF-α,IL-6,β-endorphin,IFN-γwere different among normal rats, PBS, Ad-GFP, Ad-IL-24 and zoledronic acid treated rats. In animals treated with PBS or Ad-GFP, the tumor destroyed bone matrix and periosteum and grew outside of the bone. Repeated treatment with Ad-IL-24 or zoledronic acid, the tumor was retained within the bone, the bone destruction of PBS and Ad-GFP group are heavier than Ad-IL-24 and zoledronic acid groups.Conclusion:Ad-IL-24 can treat the tibia cancer pain induced by inoculation of Walker 256 cells of SD rats, its mechanism may be due to tumor growth suppression and cytotoxicity secretion modification of Ad-IL-24, the mechanism of its original pain alleviating need further study.