The proto-oncogenes have the capacity for conversion to an oncogene that is capable of inducing or maintaining the transformed state when they are overly expressed or altered by mutation or rearrangement and crmsidered to play a central role in the pathogenesis of malignancv and also in nonnaf cellular growth and development. To study the possibie imolvement of these genes in the neoplastic transformation of S-cell malignancies, we evaluated expression of oncagenes in B cell malignancies using two DNA probes, c-k-ras and c-myc. A low-molecular weight c-k-ras transcript (1.2 kb) was detected in 9/18 fresh samples in addition to a high-molecular weight transcript (5.2 kb) which was detected in ail samples including normal lymphocytes. The level of expression of this low-molecular weight transcript was generaliy twofold higher than that of the high-molecular transcript. The low-molecular weight transcript was not detected in normal lymphocytes nor in cell lines we studied. There was no rearrangement nor amplification of c-k-ras gene on Southern blot analysis of fresh samples which have aberrant low molecular c-k-ras expressian. C-myc was expressed in all samples including normal lymphocytes without significant variation in the level of expression. Our study establishes certain oncogenes are aberrantiy expressed in some of fresh B-cell malig- nancies and suggests their role in the malignant transformation or normal cellular growth in a specific stage of hematopoietic differentiation.
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