Chapter XII 



Problems Concerning the Tumor Viruses 



Howard B. Andervont 



National Cancer Institute, National Institutes of Health, 



Bethesda, Maryland 



I. Introduction 307 



II. Problems Reviewed 308 



A. Visceral Lymphomatosis of Chickens 308 



B. Rous Sarcoma of Chickens 314 



1. Host-Virus Relationships 315 



2. Biological Properties of the Virus 319 



C. Papillomatosis of Rabbits 327 



1. Transmission of the Virus 327 



2. The Papilloma- to-Carcinoma Sequence 331 



D. Fibroma of Rabbits 335 



E. Mammary Cancer of Mice 336 



1. The Role of the Virus 338 



2. The Latency of the Virus 341 



3. The Age Factor in Response to the Virus 344 



F. Leukemia of Mice 346 



1 . Leukemia 347 



2. Parotid Gland Tumors 352 



3. Sarcomas 356 



4. Adrenal Tumors 358 



5. Discussion 358 



III. Conclusion 363 



References 363 



I. Introduction 



The idea that viruses could be implicated in the origin of tumors was 

 expressed by various investigators, especially by Borrel (1903) in connection 

 with his studies of other viruses. He was impressed with the number of viruses 

 that elicited hyperplastic reactions in infected tissues and drew the inference 

 that a continuation of this proliferative property could result in malignancy. 

 His suggestions were justified for, within a few years, viruses were implicated 

 in the origin of several tumors of chickens and, subsequently, in tumors of 

 rabbits, frogs, and mice. 



It is now known that tumor viruses may have insect vectors, may be 

 transmitted by way of the excreta, the egg, or in mother's milk. They are not 



307 



