Factors that affect antiferritin localization in four rat hepatoma models.

The effect of tumor size, vascularity, ferritin content and the amount of injected 131I-antiferritin on tumor localization was studied in four hepatoma models with varying growth rates, histology, vascularity, and ferritin content. Separate groups of 12 animals with the H-4-II-E, 7800, 7777, and 3924A rat hepatomas with less than 2 g or greater than 2 g tumors were injected with escalating doses of 131I-antiferritin or 131I nonspecific IgG (control). Tumor vascularity was measured by 51Cr-labeled erythrocyte injection, ferritin content of tumors by radioimmunoassay and immunoperoxidase staining, and the histological location of 131I-antiferritin by autoradiography. 131I-antiferritin specifically localized in the H-4-II-E and 7800 models and correlated with the tumor size, vascular content, and amount of injected antiferritin. No localization took place in the 7777 or 3924A tumors despite the presence of ferritin in these models. The only factor that correlated with localization in the models was vascularity. The vascularity of 3924A and 7777 tumors was significantly reduced in comparison to the H-4-II-E and 7800 tumors. The dependence of targeting on vascularity was demonstrated with autoradiography as well. These findings indicate the correlation of vascularity and tumor localization with 131I-antiferritin.