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Thirty-one hamsters were injected subcutaneously with bovine adenovirus type 3. The average titer of the virus was 4.38 lg TCD50/ml in a volume of 0.2 ml. Thirty animals developed solid tumors, while in one animal a cyst was seen. In 24 out of 30 hamsters the tumors were poorly differentiated sarcomas. However, a number of histological features suggest that they might be of vascular origin. Twenty-one tumors had the structure of a malignant hemangiopericytoma with areas of angioleiomyosarcoma. After the first passage in adult hamsters the structure of angioleiomyosarcoma became particularly distinct. In three animals the tumors had the appearance of malignant hemangioendothelioma. In some animals there were tumors which we think it reasonable to identify as malignant schwannomas and in one animal an unclassifiable polymorphocellular sarcoma was found. The transplantation of tumors of malignant hemangiopericytoma type resulted in a lowering of the level of differentiation, but the tendency to angioplasia persisted for a long time, though it grew less marked. Tumor cells of KOH-1 line after inoculation into hamsters induced tumors which had the structure of a malignant hemangiopericytoma with a well-pronounced component of angioleiomyosarcoma. Trente et un hamsters ont recu une injection sous-cutanee d'adenovirus bovin du type 3. Le titre moyen du virus etait de 4.38 lg TCD50/ml dans un volume de 0.2 ml. Trente animaux ont ete atteints de tumeurs solides et un kyste a ete observe chez le trente et unieme. Dans 24 des 30 cas, les tumeurs etaient des sarcomes peu differencies. Toutefois, un certain nombre de caracteristiques histologiques donnent a penser qu'elles pourraient ětre d'origine vasculaire. Vingt et une tumeurs avaient la structure d'un hemangiopericytome malin avec des zones d'angioleiomyosarcome. Apres le premier passage sur des hamsters adultes, la structure de l'angioleiomyosarcome est devenue particulierement nette. Chez trois animaux, les tumeurs avaient l'aspect d'un heman-gioendotheliome malin. Chez certains hamsters, nous avons observe des tumeurs que nous pensons pouvoir identifier a juste titre comme des schwannomes malins; chez un animal, nous avons trouve un sarcome polymorphocellulaire inclassable. La transplantation de tumeurs du type hemangiopericytome malin a entraine une diminution du niveau de differenciation, mais la tendance a l'angioplasie a persiste pendant long-temps, bien qu'elle soit de moins en moins nette. Apres inoculation a des hamsters, les cellules tumorales de la lignee KOH-1 ont induit des tumeurs ayant la structure d'un hemangiopericytome malin avec une forte composante du type angioleiomyosarcome.

Subcutaneous hamster tumors induced by Simian adenovirus SA7, strains C8, B105 and C626, were found to be poorly differentiated sarcomas having morphological features which distinguish them from tumors induced at the same site by papovaviruses and the Rous sarcoma virus. In general, the adenovirus-induced tumors were morphologically alike, C8-induced sarcomas showing some differences. Tumors induced by this strain in the subcutaneous tissue, muscles, peritoneum and mediastinum were morphologically identical. Tumors found in the brain were mainly malignant ependymomas and choroid plexus carcinomas, generally originating in neuroectoderm. The oncogenicity of adenovirus SA7 (C8) in meso- and ectodermal cells has thus been demonstrated.

Preparations of simian adenovirus SA7, strain C8, highly oncogenic for hamsters, contain a mixture of large- and small-plaque variants. The variants do not differ in their adsorption rates, virus yield per cell, sensitivity to sulfated agar polysaccharides or antigenic properties, as determined by neutralization tests. However, the small-plaque variant releases infectious virus from cells at a slower rate than the large-plaque variant. It is also more oncogenic for hamsters than the large-plaque variant, but the tumors induced by the two variants do not differ morphologically. The variants seem to induce a transplantation antigen of similar or related antigenicity. Fewer cells are required for transplantation of tumors induced by the original virus and the small-plaque variant than for transplantation of tumors induced by the large-plaque variant.