Antigenic diversity of tumors chemically induced within the progeny of a single cell

To explain why the antigens of tumors induced by oncogenic hydrocarbons are individually distinct, it has been suggested that the carcinogen induces a mutation‐like hereditary alteration expressed in the cell membrane. An alternative explanation recently proposed is that the tumor antigens pre‐exist in the normal precursor cells. Since each precursor cell contains different antigens, these are not in sufficient quantity to be recognized by the immune mechanism until clonal amplification occurs in the tumor. In order to distinguish between these propositions, low tumorigenic BALB/c 3T3 cells were first cloned in vitro and the progeny cells were then neoplastically transformed by methylcholanthrene in diffusion chambers in the abdomen of mice. The antigens of the tumors induced were still individually distinct, even though they all had been derived from the same original cell. It is concluded that the antigenic diversity of chemically induced tumors cannot be explained solely on the basis of cloning of pre‐existing variants.