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Chemical Induction of Subcutaneous Tumors in BALB/c and Swiss Mice Infected with Wild Type C RNA Viruses Derived from BALB/c Tissues¹

Department of Viral-Chemical Oncology, Microbiological Associates, Inc., Bethesda, Maryland 20014 [R. A. S., C. E. W.], and Department of Zoology, University of Maryland, College Park, Maryland 20742 [G. M. R.]

The effect of exogenous type C RNA viruses derived from BALB/c mice on the chemical induction of s.c. tumors in mice was determined in relation to host strain, age at treatment, sex, carcinogen dose, and virus strain. Viruses that were cocarcinogenic in Swiss mice were anticarcinogenic or without effect in BALB/c mice under similar treatment conditions. Such effects of viruses on tumor induction by 100 µg 3-methylcholanthrene occurred when the chemical was given at newborn but not weanling age. In BALB/c mice, the mean effect of all viral inocula was related to sex and to the dose of 3-methylcholanthrene administered. Virus decreased the induction of tumors by 25 µg 3-methylcholanthrene in males or by 100 µg 3-methylcholanthrene in females; however, virus increased tumor induction by 25 µg 3-methylcholanthrene in females or by 100 µg 3-methylcholanthrene in males. Viruses derived from tumor-bearing BALB/c mice were more co- and anticarcinogenic than viruses derived from nontumorous mice. Mixing viruses isolated from neoplasms in equal proportions with viruses isolated from normal mice averaged the effects of the individual isolates. This study indicated that wild type C RNA virus may significantly influence chemical carcinogenesis; however, the type of modifying effect depended on the mouse strain, sex and age at treatment, carcinogen dose, and virus strain.

¹ This study was conducted under Contracts NIH 70-2068 and NIH-43-67-697 within the Special Virus-Cancer Program of the National Cancer Institute, NIH, USPHS, at Microbiological Associates, Inc., and The Council for Tobacco Research.

² Submitted to the faculty of the University of Maryland in partial fulfillment of the requirements for the Ph.D. degree.

Received 6/21/72. Accepted 10/ 4/72.