Molecular analysis of expression of parental cell properties in hybrids between monocytes and a myeloma cell line

Interspecific hybrid cell lines (HINS lines) between human monocytes and a mouse (H-2d) myeloma cell line, NS1, initially showed myeloma properties, but later expressed macrophage properties, while losing myeloma cell characteristics and undergoing a marked reduction in the number of chromosomes. The aged HINS cells showed mouse but not human phenotypes. Molecular genetic analysis demonstrated loss of BLUR8 genes, expression of mouse macrophage specific genes, and enhanced transcription of H-2d and mouse beta 2-microglobulin genes in the aged cells, confirming that the hybrids' macrophage properties were attributable to NS1 genes. Transcription of kappa light chain genes was not detectable in aged HINS cells, although the genes were retained. Since some rearrangements of the genes were suggested and cycloheximide treatment induced no transcription of the genes, cis mechanisms might be involved in the loss of expression of the genes.