Chemically induced murine T lymphomas: continued rearrangement within the T-cell receptor beta-chain gene during serial passage.

The first constant region of the Tcrb gene was completely deleted from the DNA of 8/10 mouse cell lines established from 3-methylcholanthrene-induced RF/J thymic lymphomas, but 6/7 primary lymphomas contained the first constant region sequences. DNA from RF/J thymic lymphomas induced by N-methyl-N-nitrosourea was then examined serially as the tumors were passaged in vivo and adapted to growth in culture as uncloned and, in some cases, cloned lines. Patterns of Tcrb-specific restriction fragments from most tumors changed extensively during continued propagation. Analysis of the patterns often suggested that initial DNA rearrangements within the Tcrb complexes of monoclonal tumors had been followed by further rearrangements within the same genes. However, these different patterns may alternatively have represented successive outgrowth of separate lineages from lymphomas that were polyclonal in origin.