THE PROLIFERATION OF MULTIPLE-MYELOMA COLONIES (MY-CFU-C) IN-VITRO ISINDEPENDENT OF PROGNOSIS AND IS NOT ASSOCIATED WITH MUTATED N-RAS OR K-RAS ALLELES IN HUMAN BONE-MARROW ASPIRATES

During the period September 1987 to March 1993 the proliferation of my eloma cells as colonies (MY-CFUc) in vitro was examined in bone marrow aspirates from 43 patients with multiple myeloma and two patients wit h Waldenstrom's macroglobulinaemia. Twenty-four samples from 45 patien ts, of whom three were at presentation, four were in complete remissio n (CR), six had achieved a partial response (PR) and 11 had progressiv e disease (PD), produced MY-CFUc in vitro. The same bone marrow aspira tes or one taken within 2 mon:hs of that assessed for MY-CFUc were use d in the polymerase chain reaction (PCR). Genomic DNA was analysed for mutations in N- and K-ras by slot blotting of the amplified products from the PCR with P-32-labelled probes and by direct sequencing. No mu tations were detected in N- or K-ras proto-oncogenes al codons 12, 13 or 61 in any sample. Eleven of the patients from whom MY-CFUc were pro duced remain alive with a median survival of 73 months (range 15-75 mo nths). MY-CFUc have been cultured from 19 of these 24 patients on subs equent occasions, of whom nine remain alive. Among patients whose cell s did not produce MY-CFUc in vitro at the time of sampling for mutated ras alleles, biopsy samples from four patients have produced MY-CFUc in vitro on subsequent occasions, of whom one patient remains alive. T he data show that the proliferation of MY-CFUc in vitro occurred indep endently of disease status and was not indicative of prognosis. The fa ilure to detect mutated N- or K-ras alleles in any sample suggests tha t if such mutations were present in the cells which form colonies in v itro they represented less than 0.1% of the tumour burden and did not affect the survival of this group of patients.