Five oral cancer cell lines, FaDu, HEp-2 SCC-4, 1483, OEC-M1, and one epidermoid carcinoma cell line, A-431, were examined for their expression level of c-Ki-ras 2 gene and the presence of activating mutations. Northern blot analysis revealed
that
the
expression level of c-Ki-ras 2 mRNA of FaDu cells was 4 times that of primary cultured normal human oral keratinocytes (NHOK).
OEC-M1 cells expressed mRNA of a little smaller size than normal and the expression level was much higher than in NHOK. Other cells expressed c-Ki-ras 2 mRNA at comparable levels to NHOK. DNA sequencing of c-Ki-ras 2 gene exon 1 and exon 2 was
performed
using polymerase chain reactionamplified DNA fragments. OEC-M1 cells had three point mutations in their c-Ki-ras 2 gene exon 1 and exon 2 resulting in amino acid substitutions, asparagine to aspartic acid, phenylalanine to leucine, and glycine to
arginine at 24the , 28th and 53rd residues respectively. However, other cells had no mutation in their c-Ki-ras 2 gene exon 1 and exon 2. This result shows that abberant expression of c-ki-ras 2 gene and the point mutations are quite often
associated
with oral cancer.
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