Mechanism of T-cell lymphomagenesis: transformation of growth-factor-dependent T-lymphoblastoma cells to growth-factor-independent T-lymphoma cells.

In a previous paper we described the induction by x-irradiation or radiation-induced leukemia virus-inoculation of two classes of lymphoid T-cell neoplasms: The first class, designated T-cell lymphoblastoma (TCLB), consists of growth-factor-dependent eudiploid cells that home to the spleen and give rise to splenic tumors on injection into syngeneic mice; the second class, designated T-cell lymphoma (TCL), consists of growth-factor-independent aneuploid or pseudodiploid cells that give rise to local tumors at the site of subcutaneous injection. This paper describes the generation of a family of growth-factor-independent aneuploid or pseudodiploid TCL cells after the injection into the thymus of growth-factor-dependent diploid TCLB cells. In contrast to the donor TCLB cells, the resulting TCL cells could be cloned in semisolid medium, produced local tumors at the site of subcutaneous injection, and proliferated in a growth-factor-independent fashion in vitro. The induced growth-factor-independent TCL cells were chromosomally and phenotypically unstable and continued to evolve both in vivo and in vitro. After propagation in the thymus, the cells often showed stable translocations in addition to the evolving aneuploidy. We propose that the chromosome abnormalities induced during the proliferation of growth-factor-dependent TCLB cells in the thymus constitute a general mechanism by which neoplastic cells progress from growth-factor dependency to independency.