Benzo[a]pyrene-induced respiratory tract cancer in hamsters fed a diet rich in beta-carotene. A histomorphological study.
The effect of a high dietary level of beta-carotene on the formation of preneoplastic and neoplastic respiratory tract lesions was studied in hamsters intratracheally treated with benzo[a]pyrene (B[a]P) attached to ferric oxide (Fe2O3) and suspended in saline. In addition to conventional histopathological examinations, the expression of cytokeratins and the glutathione S-transferase isoenzyme Pi (GST-Pi) was determined in tracheal epithelium using immunocytochemical techniques. B[a]P treatment increased the expression of cytokeratins in tracheal mucous and ciliated epithelial cells as detected by antibody RCK102 (cytokeratins 5 and 8), which normally recognizes basal cells only. The expression of cytokeratins in mucous and ciliated cells as detected by antibody RGE53 (cytokeratin 18) was decreased by B[a]P treatment. Furthermore, the expression of the cytokeratin detected by antibody RKSE60 (cytokeratin 10), characteristic of metaplastic squamous cells, and the expression of the GST-Pi, characteristic of metaplastic changes, was increased in trachael epithelium of hamsters treated with B[a]P. There was no evidence for dietary beta-carotene affecting the expression of cytokeratins or GST-Pi. The incidence of preneoplastic changes and tumors of the respiratory tract was not reduced by dietary beta-carotene. On the contrary, the tumor response of the respiratory epithelium was almost twice as high in hamsters fed the high beta-carotene diet than in hamsters on the low beta-carotene diet. However, this difference was not statistically significant (P = 0.15); hence, the present study did not produce evidence for a clear effect of beta-carotene on B[a]P-induced respiratory tract cancer in hamsters.
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D001564:Benzo(a)pyrene; D002338:Carotenoids / Q000008:administration & dosage*; D006224:Cricetinae; D004848:Epithelium / Q000737:chemistry; D005982:Glutathione Transferase / Q000032:analysis*; D007633:Keratins / Q000032:analysis*; D008297:Male; D008647:Mesocricetus; D009374:Neoplasms, Experimental / Q000139:chemically induced / Q000473:pathology; D012142:Respiratory Tract Neoplasms / Q000139:chemically induced / Q000473:pathology*; D014132:Trachea / Q000737:chemistry*; D019207:beta Carotene
D000970:Antineoplastic Agents; D019207:beta Carotene; D001564:Benzo(a)pyrene; D002338:Carotenoids; D007633:Keratins; D005982:Glutathione Transferase