NEOPLASTIC TRANSFORMATION OF MOUSE C3H10T1 2 CELLS FOLLOWING EXPOSURETO NEUTRONS DOES NOT INVOLVE MUTATION OF RAS GENE AS ANALYZED BY SSCPAND CYCLE SEQUENCING/

About 25% of human tumors contain a mutated member of the ras gene fam ily. Neutron exposure is an occupational risk in several work places a nd while we know that cells exposed to neutrons can become transformed , the molecular basis of this process is not understood. To determine whether neutron-induced cellular transformation involves ras mutation, C3H10T1/2 cells were exposed to a single dose of 5.9 MeV neutrons, Ty pe II and type III foci were isolated and established as cell lines, A total of 34 foci were selected and expanded for analysis of tumorigen icity, chromosomal aberrations and mutations in members of the ras gen e family. The presence of mutations in genomic DNA in N-ras or K-ras o f each focus was examined by either single-strand conformational polym orphism (SSCP) analysis or by asymmetric PCR coupled cell cycle sequen ce analysis, Although chromosomal aberrations were detected at metapha se, no alterations in either ras gene were detected. We conclude that in vitro neutron-induced transformation must occur through a mechanism other than ms mutation.