Effects of ¹⁸F-FDG on P53, XIAP, and GADD45 expressions in transplanted Lewis lung carcinoma in mice

Objective: To study the effects of internal exposure of ¹⁸F-FDG (¹⁸F-2-deoxy-2-fluoro-D-glucose) on the protein expressions of P53, XIAP (X-linked inhibitors of apoptosis protein) and GADD (growth arrest and DNA damage)45 in Lewis lung carcinoma, and to explore the possibility of applying ¹⁸F-FDG as a radiotherapy drug in vivo. Methods: Lewis lung cancer transplanted tumor models were established via subcutaneous injection of 0.2 ml of 2 × 10⁷/ml Lewis lung carcinoma cells at left hind limbs of 48 C57BL/6 mice that were randomly divided into high dose group, low dose group and control group with 16 mice each. After 7 d of cancer cell inoculation, 18.5 × 10⁷ Bq and 9.25 × 10⁷ Bq of ¹⁸F-FDG in 0.2 ml saline or equal volume of physiological saline was intraperitoneally injected into three group mice, respectively. 22 d post inoculation, the protein expressions of P53, XIAP and GADD45 were immuo-histochemically detected by using SP approach. Results: There was significant difference among the protein expressions in each group (χ² = 8.30, 16.02, 7.68, P < 0.05). The mean integral optic density of protein expression increased from 0.089 ± 0.033 in control group to 0.315 ± 0.028 in high dose group for P53, and from 0.126 ± 0.023 to 0.383 ± 0.035 for GADD45, but it decreased from 0.422 ± 0.034 to 0.149 ± 0.055 for XIAP. There was significantly difference of these protein expressions in each group (P53 : F = 5.26, P < 0.05; XIAP: F = 4.29, P < 0.05; GADD45 : F = 5.98, P < 0.05). Conclusions: ¹⁸F-FDG can up-regulate the expressions of P53 and GADD45 proteins and down-regulate the expression of XIAP protein in tumor cells, and it inhibits tumor growth by promoting cell apoptosis in the Lewis lung carcinoma tissue with a P53-dependent manner. (authors)