In vitro malignant progression of cells derived from Abelson murine leukaemia virus-induced thymic lymphomas

Moloney virus induction of T-cell lymphomas in a plasmacytomagenic strain of E mu-v-abl transgenic mice

Although the v-abl gene can provoke several types of lymphoid neoplasm, mice of a transgenic strain (E mu-v-abl 40) in which lymphocytes are targeted for expression of v-abl by a linked immunoglobulin enhancer (E mu) spontaneously develop only plasmacytomas. To determine whether other lymphocytes of this strain were susceptible to transformation, and to identify genes that can collaborate with v-abl in tumorigenesis, E mu-v-abl 40 mice were subjected to insertional mutagenesis by neonatal infection with Moloney murine leukemia virus. Tumorigenesis was accelerated moderately, but nearly all the tumors were T lymphomas. The altered tumor type may reflect both the T-cell tropism of Moloney virus and the higher level of E mu-v-abl 40 expression found in T lymphocytes than in B lymphocytes. Insertion near the c-myc, N-myc or pim-I gene was observed in 42% of the induced tumors, indicating that each of these genes may collaborate with v-abl in lymphomagenesis. Most of the accelerated tumors had a surprisingly low level of transgene expression. Thus, high expression of v-abl may not be required for Moloney-induced T lymphomagenesis.

Tumours induced by Moloney murine sarcoma virus are clonal in rats, not clonal in mice

Moloney murine sarcoma virus (M-MSV) induces rapidly growing tumours in adult mice of most conventional strains. Rats are less susceptible to M-MSV oncogenesis, but the few rhabdomyosarcomas that do develop after viral inoculation of newborn animals closely resemble conventional malignancies: they develop after a long latency, grow progressively, and metastasize to regional lymph nodes and lungs. Southern blot analysis with a v-mos-specific probe of M-MSV-induced tumours in both species demonstrated an oligo-, monoclonal pattern of exogenous v-mos integration only in the rat system, while mouse tumours were not clonal in origin. Furthermore, the same type of analysis of lymph node and lung metastases showed that cell clones already present in the primary rat lesion colonized secondary sites during tumour progression. Apparently, Moloney murine leukemia virus (M-MuLV) was not involved in rhabdomyosarcoma pathogenesis since M-MuLV-specific DNA sequences could not be demonstrated in three of the six rat tumours. Finally, in all mouse tumours, unintegrated linear M-MSV proviruses could be readily detected.

In Vitro Immune-Receptor Gene Rearrangemets in Clonal Thymic Lymphomas Induced by Abelson Murine Leukemia Virus

The Abelson and Moloney murine leukemia virus complex (A-MuLV/M-MuLV) induces rapidly growing thymic lymphomas following direct injection into the thymus of newborn BALB/c and C57BL/6 mice. Southern blot analysis with a v-abl specific probe not only demonstrated that primary tumors are clonal, but also that the pattern of A-MuLV provirus integration is quite stable in primary tumor cells, as well as in their derived cell lines and clones. Most of the cell samples were able to rearrange the immunoglobulin heavy chain genes in culture, whereas in two cases the T cell receptor gamma chain genes also underwent rearrangement. Since the recombination mechanism is operative only in very immature lymphoid cells, these data provide indirect evidence for the lack of differentiation of A-MuLV cell targets in the thymus.