An unusual H-Ras mutant isolated from a human multiple myeloma line leads to transformation and factor-independent cell growth.
Multiple myeloma (MM) is an incurable plasma cell malignancy. To investigate biochemical lesions associated with MM, we constructed an expression cDNA library from the OPM-2 human myeloma line. A highly transforming H-Ras mutant was identified by transfection analysis using NIH 3T3 cells. DNA sequencing demonstrated a single-point mutation at position 117 located in the guanine nucleotide-binding site resulting in a lysine-to-glutamic acid substitution. This mutant, H-Ras (K117E), was found to be constitutively activated in terms of GTP binding. We compared the biological effects of H-Ras (K117E) and H-Ras (G12V) in 32D murine hematopoietic progenitor cells. Whereas both Ras proteins are constitutively activated, 32D cells expressing H-Ras (G12V) are still dependent on IL-3 for survival and proliferation while cells carrying H-Ras (K117E) become IL-3 independent. Similar experiments conducted with the B9 line, an IL-6-dependent hybridoma, also demonstrated that B9/H-Ras (K117E) became IL-6-independent. Expression of H-Ras (K117E) in the human IL-6-dependent ANBL-6 myeloma line resulted in enhanced proliferation at suboptimal concentrations of IL-6. These observations suggest that H-Ras mutations at the binding site for the GTP nucleotide ring structure may also represent activating lesions and have additional biological effects when compared to previously described Ras mutants.
Crowder
Chun
C
Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Kopantzev
Eugene
E
Williams
Kevin
K
Lengel
Carol
C
Miki
Toru
T
Rudikoff
Stuart
S
D000818:Animals; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D011905:Genes, ras / Q000502:physiology; D006133:Growth Substances / Q000502:physiology; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D051379:Mice; D009101:Multiple Myeloma / Q000235:genetics*; D009154:Mutation; D014407:Tumor Cells, Cultured
D006133:Growth Substances; D006160:Guanosine Triphosphate