Chromosome 15 trisomy in spontaneous and carcinogen-induced murine lymphomas of B-cell origin.

G-banding analyses of 14 independently derived B-cell lymphomas showed the frequent occurrence of chromosome 15 trisomy. It was present in seven of nine spontaneous B-cell lymphomas, but in company with other trisomies, monosomies and marker chromosomes. In five carcinogen-induced primary B-cell leukemias, trisomy 15 was the dominating change. Taken together with the previously demonstrated importance of chromosome 15 trisomy for T-cell leukemogenesis and of the 12;15 translocation in plasmacytogenesis in the mouse, it appears likely that the distal part of chromosome 15 carries a cluster of genes, perhaps a supergene region, that may play an important role in the differentiation and/or the normal responsiveness of various lymphoreticular cell types to growth control.

The plate-implant as a bioassay for the neoplastic potential of cultured cells.

One objective of this study was to test the plate implant as an in vivo bioassay for the neoplastic state with pairs of cell lines that were non-tumorigenic and tumorigenic when inoculated in suspension at various sites. Each pair originated from a common cell pool or from one cell derived from normal rat or mouse embryonic tissue. The implantation of cells attached to polycarbonate plates was compared with the subcutaneous injection of comparable numbers of cells in suspension or the intraocular injection of 10(5) cells. In addition, some implants of glass helices with attached cells were made into syngeneic mice and compared with injection of comparable cell numbers intramuscularly into X-irradiated hosts. A total of 10 lines or clones were tested on plates. Of four lines that were non-tumorigenic when inoculated in suspension either subcutaneously or intraocularly, two were tumorigenic when implanted subcutaneously attached to plastic plates. The remaining two are the first permanent rodent lines that have not been tumorigc on plastic plates. Of the remaining six lines, all were tumorigenic on plates and two produced sarcomas at a higher frequency on plates than in suspension. Cytologic diagnoses of the cells implanted on plates, subcutaneously and intraocularly, correlated best with the results from plate implants. Of three mouse lines implanted on helices, two were equally tumorigenic in suspension and on helices, whereas the third was tumorigenic on helices only. The plate implant was more satisfactory technically than the helices and proved to be one of the most sensitive bioassays for the neoplastic state of cultured cells.

Two spontaneous BALB/c lymphomas synthesize IgM: monomers and half molecules are isolated and characterized whereas another molecule resembles IgD.

Spontaneous lymphomas of BALB/c mice, both in vivo tumors and cell lines established in long term tissue cultures, were investigated for their ability to synthesize IgM by using radiolabeled amino acid precursors. Immunoglobulins manufactured by lymphomas K46 and L10A had the m.w. of monomeric IgM and IgM half molecule. Both of these molecules could be immunoprecipitated with class-specific anti-IgM but not anti-IgA or anti-IgG. When precipitated with polyvalent anti-Ig L10A synthesized monomeric immunoglobulins that migrated as two peaks in contrast to their single counterpart precipitated with anti-IgM. The second peak migrated in the region expected for IgD. Monomer and half molecules were composed of similar ratios of mu-chains to light chains linked by disulfide bonds. The mu2L2 monomer of these B cell lines migrated slightly slower in SDS PAGE than a mu2L2 secreted by a myeloma. Thus, these lymphomas synthesize immunoglobulins with the chemical and antigenic characteristics typical of monomeric membrane-attached IgM and IgM half molecules, plus a molecule resembling IgD on L10A only. Lymphoma assembly of monomeric IgM may follow the same initial biosynthetic sequence as myeloma assembly.