Inverse relationship between chromosome ploidy and host-specificity of sixteen transplantable tumors

Abstract

A representative series of four lymphomas, five carcinomas, one melanoma, and six sarcomas (largely in the ascites form) has been surveyed for chromosome number distribution, growth capacity in foreign strains and, where possible, histocompatibility genes. This comparative analysis, supported by relevant data from other laboratories, has demonstrated a consistent influence of ploidy (2n versus 4n) upon degree of antigenicity. The diploid neoplasms were entirely strain-specific and always regressed in unrelated lines. The tumors characterized by a tetraploid modal value were able to grow in and kill hosts of one or more foreign genotypes, or even showed complete genetic indifference. This inverse relationship between chromosome number and host-requirements appears to be independent of the tumor's histology, virulence, strain of origin, method of induction, and transplantation history. The findings are suggestive of “immunologic selection” from a relatively narrow (mode near 2n) or wide (mode near 4n) range of viable antigenic variants in a malignant cell population.