Radioimmunotherapy using vascular targeted 213Bi: the role of tumor necrosis factor alpha in the development of pulmonary fibrosis.
A monoclonal antibody (201B) specific to murine thrombomodulin, covalently linked to cyclohexyl diethylenetriaminepentaacetic acid, successfully delivers chelated 213Bi, an alpha-particle emitter, (213Bi-201B) rapidly to lung vascular endothelium. When injected at doses of 1 MBq/mouse, 213Bi-201B destroyed most of the 100 colonies of EMT-6 mammary carcinomas growing as lung tumors of up to 2000 cells/colony. Some mice were cured of lung tumors, and others had extended life spans compared to untreated control animals but eventually succumbed to tumor recurrence. At injected doses of 4-6 MBq/mouse, 100% of lung tumor colonies were eliminated; however, 3-4 months later, these mice developed pulmonary fibrosis and died. The mechanisms leading to the fibrotic response in other pulmonary irradiation models strongly implicate tumor necrosis factor alpha (TNF-alpha), released from damaged tissues, as the pivotal inflammatory cytokine in a cascade of events that culminate in fibrosis. Attempts to prevent the development of pulmonary fibrosis, by using antibodies or soluble receptor (rhuTNFR:Fc) as inhibitors of TNF-alpha, were unsuccessful. Additionally, mice genetically deficient for TNF-alpha production developed pulmonary fibrosis following 213Bi-201B treatment. Interestingly, non-tumor-bearing BALB/c mice receiving rhuTNFR:Fc or mice genetically deficient in TNF-alpha production and treated with 213Bi-201B, had significantly reduced life spans compared to mice receiving no treatment or 213Bi-201B alone. We speculate that in normal mice, although TNF-alpha may induce an inflammatory response following alpha-particle radiation mediated tumor clearance and pulmonary damage, its effects in the post-tumor clearance time period may actually retard the development of fibrosis.[1]References
- Radioimmunotherapy using vascular targeted 213Bi: the role of tumor necrosis factor alpha in the development of pulmonary fibrosis. Davis, I.A., Kennel, S.J. Clin. Cancer Res. (1999) [Pubmed]
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