Induction of haem oxygenase-1 by nitric oxide and ischaemia in experimental solid tumours and implications for tumour growth

• Published in: British Journal of Cancer 1999-08, Vol.80 (12), p.1945-1954
• Main Authors: Doi, K, Akaike, T, Fujii, S, Tanaka, S, Ikebe, N, Beppu, T, Shibahara, S, Ogawa, M, Maeda, H
• Format: Article
• Language: English
• Subjects: Animal tumors. Experimental tumors; Animals; Biological and medical sciences; Biomedical and Life Sciences; Biomedicine; Cancer Research; Cell Division - drug effects; Drug Resistance; Electron Spin Resonance Spectroscopy; Enzyme Induction; Enzyme Inhibitors - pharmacology; Epidemiology; Experimental tumors, general aspects; Gene Expression Regulation, Neoplastic; Heme Oxygenase (Decyclizing) - biosynthesis; Heme Oxygenase (Decyclizing) - genetics; Heme Oxygenase-1; Liver Neoplasms, Experimental - enzymology; Liver Neoplasms, Experimental - genetics; Liver Neoplasms, Experimental - pathology; Macrophages - enzymology; Macrophages - pathology; Medical sciences; Molecular Medicine; Nitric Oxide - physiology; Nitric Oxide Synthase - biosynthesis; Nitric Oxide Synthase - genetics; Nitric Oxide Synthase Type II; Oncology; Protoporphyrins - pharmacology; Rats; Rats, Inbred Strains; Regular; regular-article; Tumors
• ISSN: 0007-0920; 1476-5381; 1532-1827
• DOI: 10.1038/sj.bjc.6690624

Summary Induction of haem oxygenase-1 (HO-1) as well as nitric oxide (NO) biosynthesis during tumour growth was investigated in an experimental solid tumour model (AH136B hepatoma) in rats. An immunohistochemical study showed that the inducible isoform of NO synthase (iNOS) was localized in monocyte-derived macrophages, which infiltrated interstitial spaces of solid tumour, but not in the tumour cells. Excessive production of NO in the tumour tissue was unequivocally verified by electron spin resonance spectroscopy. Tumour growth was moderately suppressed by treatment with either N ω -nitro- L -arginine methyl ester ( L -NAME) or S -methylisothiourea sulphate (SMT). In contrast, HO-1 was found only in tumour cells, not in macrophages, by in situ hybridization for HO-1 mRNA. HO-1 expression in AH136B cells in culture was strongly enhanced by an NO (NO + ) donor S -nitroso- N -acetyl penicillamine. HO-1 mRNA expression in the solid tumour in vivo decreased significantly after treatment with low doses of NOS inhibitors such as L -NAME and SMT (6–20 mg kg –1 ). However, the level of HO-1 mRNA in the solid tumour treated with higher doses of NOS inhibitor was similar to that of the solid tumour without NOS inhibitor treatment. Strong induction of HO-1 was also observed in solid tumours after occlusion or embolization of the tumour-feeding artery, indicating that ischaemic stress which may involve oxidative stress triggers HO-1 induction in the solid tumour. Lastly, it is of great importance that an HO inhibitor, zinc protoporphyrin IX injected intra-arterially to the solid tumour suppressed the tumour growth to a great extent. In conclusion, HO-1 expression in the solid tumour may confer resistance of tumour cells to hypoxic stress as well as to NO-mediated cytotoxicity.