Characterization of Solid Tumors Induced by Polycyclic Aromatic Hydrocarbons in Mice

BACKGROUND: To assess the effects of single polycyclic aromatic hydrocarbons (PAHs) on solid tumor initiation, and investigate their roles in immune response regulation. MATERIAL/METHODS: Mice (100) were randomly divided into 5 groups (n=20) to be intraperitoneally injected with 10 daily doses of DMSO (control), anthracene (50 mg/kg), benzo-(a)-pyrene (10 mg/kg), benzo-(a)-pyrene (20 mg/kg), and benzo-[G, H, I])-perylene (5 mg/kg), respectively. Three months later, serum IL-2 and IL-6 levels were assessed by ELISA; liver, kidney, stomach and lung tissues were subjected to histopathological examinations. RESULTS: Liver cancer incidences after benzo-[G, H, I]-perylene, benzo-(a)-pyrene (10 mg/kg), benzo-(a)-pyrene (20 mg/kg), and anthracene were 21.1, 26.3, 35.3, and 27.8%, respectively; 21.1, 0, 41.2, and 0% showed stomach cancer, respectively; 0, 0, 11.8 and 0% displayed kidney cancer, respectively. The occurrences of precancerous liver lesions for benzo-[G, H, I]-perylene, benzo-(a)-pyrene (10 mg/kg), benzo-(a)-pyrene (20 mg/kg) and anthracene groups, respectively, were 68.4, 73.7, 64.7, and 55.6%; 78.9, 68.4, 29.4, and 27.8% showed precancerous stomach lesions, while 42.1, 47.4, 58.8, and 33.3% had precancerous kidney lesions; respectively. No obvious lung lesions were found in any group. Serum IL-2 and IL-6 levels in treatment groups were significantly lower compared with control values (P<0.01). CONCLUSIONS: PAHs induce cancer and precancerous lesions in the liver, stomach, and kidney. Benzo (a) pyrene initiates gastric cancer in a dose-dependent manner, but does not induce precancerous lung lesions. Lower IL-2 and IL-6 levels in treatment groups compared with controls suggest that PAHs cause overt immune inhibition.