Transformation of single myeloid precursor cells by the malignant histiocytosis sarcoma virus (MHSV): Generation of growth‐factor‐independent myeloid colonies and permanent cell lines

Abstract

Direct single-cell assays for oncogenic transformation are available for fibroblasts but not for other cell types. Using malignant histiocytosis sarcoma virus (MHSV), a member of the ras family of retroviruses, in vivo-infected granulocyte/macrophage and macrophage precursor cells lost the requirement for externally added hematopoietic growth factors. Factor-independent growth was demonstrated by colony-transfer experiments. More than 25% of the independent colonies were established as permanent macrophage cell lines following a phase of adaptation to tissue culture conditions. Factor-independent colony growth was also obtained by in vitro infection of single cells. As many as 50% of all myeloid precursor cells were target cells for MHSV as measured by this assay. About 2 x 10(-3) of these colony-forming cells acquired growth factor independence and immortality after in vitro infection. Cell lines derived from these colonies did not require adaptation to tissue culture conditions.

Genetic and immunological parameters governing in vivo susceptibility/resistance to retrovirally induced murine malignant histiocytosis

“…In the human, the long arm of chromosome 5 has a cluster of genes encoding growth factors and growth factor receptors the interruption of which may have grave consequences for hematopoiesis [36,37]. For example, the genes for CSF1 and the CSFR (also called c-fms) which, on deregulation by the 5q35:6p21 translocation, give rise to the factor-independent growth of transformed macrophages [38] also seen in mice with MHSVinduced malignant transformation of macrophages [39,40]. Wherever the reciprocal translocation may occur, the common feature is the break at 5q35 [5], the location of the CSF receptor near the gene for CSF itself, setting the stage for an uncontrolled receptor ligand stimulatory loop to augment the transformation event.…”

The malignant histiocytosis sarcoma virus, a recombinant of Harvey murine sarcoma virus and Friend mink cell focus-forming virus, has acquired myeloid transformation specificity by alterations in the long terminal repeat

“…Ha-MuSV, MHSV induces a very rapid malignant histiocytosis in adult mice (25) and allows the establishment of growth factor-independent macrophage cell lines from infected spleens (12,19). In vitro infection of single granulocyte-macrophage or macrophage precursor cells results in immediate factor-independent growth and, more rarely, can be adapted to permanent growth in vitro (16,18). In contrast, Ha-MuSV causes only a transient increase of macrophage colony forming cells in the spleen (25), and in vitro bone marrow infection results in transformed macrophage cells that are neither immortal nor factor independent (31,36).…”

“…Biologically cloned MHSV, in contrast to Ha-MuSV, induces a disease in adult mice which is characterized by a huge and preferential increase of macrophages and macrophage precursor cells. Although some macrophage precursors infected with Ha-MuSV do not require CSFs for proliferation and colony formation, this loss of CSF requirement is much more pronounced in macrophage precursors infected with MHSV (12,18). To test whether these properties were unaltered in the molecularly cloned MHSV and whether they were influenced by the type of LTR, spleen cells from mice infected with MHSV, Ha-MuSV, and MHSV-Hi U3 were analyzed by hematopoietic colony assays.…”

“…On infection of single isolated myeloid precursor cells, MHSV, unlike other acutely transforming murine retroviruses, induces growth factor-independent proliferation and differentiation at a high frequency (16,18). A minority of these cells can acquire immortality after prolonged in vitro culture.…”

Heterogeneity in a mouse model of histiocytosis: transformation of Langerin+ dendritic cells, macrophages, and precursors

“…However, the primary target cell of the virus is probably not or not only a mature M, but a precursor of these cells. This is suggested by the finding that in vitro, as well as in vivo infection of hematopoietic cells with MHSV facilitates, in the absence of exogenously added growth factors, the proliferation of a significant fraction of myeloid progenitor cells [8].…”