Oligoclonality of Moloney leukemias.

Induction of leukemia by non-transforming retroviruses results in the appearance of various hematopoietic tumors. It is believed that these tumors are monoclonal. In this work, the clonal nature of Moloney leukemia virus (MoLV)-induced tumors was studied. Two genetic parameters were used in order to identify leukemic clones: the pattern of the proviral integration sites and the rearrangement of the T-cell receptor complex (TCR). In more than 60% of the mice, different leukemic clones populated tumors developed in different organs of the same animal. Genotypic analysis of cell lines derived from a leukemic organ revealed that the tumor is composed of more than one clone. Phenotypic analysis of subclones which were derived from a monoclonal cell line showed variability in the expression of the Thy 1.2 and MHC antigens. The results indicate that MoLV-induced tumors are of oligoclonal nature. Each leukemic organ contains a mixture of leukemic clones, of which one is dominant.