Factors influencing development of tumors in frogs

Is cancer communicable?

Recent developments in cancer epidemiology have led to the possibility of an exceedingly complex communicable factor(s) in cancer etiology. The transmission of such an agent(s) may require a susceptible genotype and/or other promotional events. Likely candidates which support this supposition include: Epstein-Barr virus (nasopharyngeal carcinoma, Burkitt's lymphoma, salivary gland tumor among Eskimos, X-linked lymphoproliferative syndrome of Purtilo); human T-cell leukemia virus (adult T-cell leukemia); acquired immune deficiency syndrome (AIDS), complicated by Kaposi's sarcoma (etiologic agent remains elusive, though epidemiology suggests possible infectious transmission); abnormal immune phenomena in households of Hodgkin's disease patients; and clustering of various types of cancer in spouses, the general population, and families. We have selectively reviewed the literature and evolved an etiologic hypothesis which integrates a communicable agent(s) in concert with genetic and/or environmental carcinogenic interaction which could conceivably explain a significant fraction of the total cancer burden.

Isolation and characterization of viruses from the kidneys of Rana pipiens with renal adenocarcinoma before and after passage in the red eft (Triturus viridescens)

Viruses were isolated from kidneys of normal and renal tumor-bearing Vermont Rana pipiens after subinoculation into red eft newts (Triturus viridescens). Organs of efts inoculated with viable cell suspensions from four of seven tumor-bearing kidneys yielded virus (LT-1, -2, -3, -4) when inoculated into TH-1 (Terrapene heart) cell culture. One tumor-bearing kidney also yielded virus (L-4) by direct inoculation into TH-1 cells. An additional isolate (L-5) was obtained from 1 of 52 normal Vermont frog kidneys inoculated directly into TH-1 cells. LT-1 was propagated with cytopathic effect (CPE) in each of 38 cell types tested, of fish, amphibian, reptilian, avian, and mammalian origin, at 23 or 30 C. LT-1 through LT-4, L-4 and L-5, and FV-1 through FV-3 each induced similar CPE in all cells tested. LT-2, however, induced CPE that progressed at a slower rate than that caused by the other isolates and produced smaller plaques (<0.8 mm) under starch gel overlay. Each of the viruses replicated to high titer in embryonated eggs incubated at 30 C. The viruses also grew in efts and adult newts, but not in bullfrog (Rana catesbeiana) tadpoles or adult leopard frogs. Tumor induction in adult leopard frogs inoculated with LT-1 was not demonstrated. Electron microscopic observations of LT-1 and LT-2 viruses revealed cytoplasmic particles, hexagonal in cross section, approximately 120 to 140 mmu in diameter, containing a dense nucleoid. LT-1 and LT-2 viruses were indistinguishable from FV-1 and Tipula iridescent virus. LT-1 was presumed to be a deoxyribonucleic acid virus on the basis of 5-bromodeoxyuridine inhibition. The isolates were ether-sensitive. On the basis of biological, physicochemical, and antigenic similarities, LT-1 through LT-4, L-4, L-5, FV-1 through FV-3, and isolates recently recovered from the bullfrog and the newt may represent strains of the same amphibian cytoplasmic virus.