96 . F. B. BANG 



controls, is there morphological evidence of lysogeny and/or latency, and is 

 the continued presence of virus demonstrable throughout the existence of the 

 tumor? 



3. Is the specificity ascribed to some tumor viruses reflected in analogous 

 specific effects in tissue culture? This question remains unsettled, even with 

 respect to the well-studied Rous chicken tumor virus. Although the answers 

 to these questions cannot yet be conclusive, it is encouraging that it is now 

 feasible to ask them, and that the implements for finding the answers are 

 available. The five selected types of tumors will emphasize the variety of 

 cellular reactions to the viruses. This variety of reactions should not, how- 

 ever, obscure the fact that data on the above questions are not complete for 

 any one virus-host cell system relationship. 



A. Rous Chicken Sarcoma 



Although this tumor was proved to be of viral etiology almost 50 years 

 ago (Rous, 1911), there is a present need to understand the effect of this virus 

 on living cells of established strains. Many early observations on living cells 

 have been obscured by controversy over the nature of the tumor cell, whether 

 it is macrophage or fibroblast. It is ticklish today to describe with assurance 

 the effect of the virus on macrophages and fibroblasts, for it has been pro- 

 posed both that the virus could convert macrophages into fibroblasts (Carrel 

 and Ebeling, 1926), and that under other virus-induced conditions fibro- 

 blasts could become phagocytic (Fischer and Laser, 1927). Some light may 

 have been shed on the enigma by the study of Sanford et al. (1952), who 

 showed that fibroblasts grown in horse sera would support growth of the 

 virus for six months, while macrophages failed to support it after a few days. 

 There is no record of a comparable experiment using chicken sera. 



Borel (1926) showed that cultures of the Rous tumor consisted of two types 

 of cell: round basophilic cells and fusiform fibroblasts. The macrophages 

 often yielded multinucleated plasmodia which at times reached a diameter 

 of 600 /x. The fusiform cells were occasionally equally large. Both types of 

 cells showed an accumulation of eosinophilic material in the cytoplasm 

 corresponding to the eosinophilic paranuclear mass seen in the tumor cells 

 in the animal. Hypertrophied nuclei and an accumulation of fat droplets 

 were characteristic, as was an extraordinarily lavish network of mitochondria. 



1. Effect on Cells in Tissue Culture 



The most detailed study of these cells as cultivated in vitro is that of 

 Doljanski and Tenenbaum (1942; Tenenbaum and Doljanski, 1943). They 

 documented and fully illustrated the "distinctive syndrome of severe cell 

 disease." Although their work was carried out on an "18-year old strain of 

 the tumor," it was maintained with the regular addition of fragments of 



