No evidence for the mutation of ras gene in psoriatic epidermis.

The ras oncogene product, ras p21, is structurally homologous to guanine nucleotide-binding proteins, which play an important role in transmembrane signaling systems. Recently, enhanced expression of ras p21 has been reported in the psoriatic hyperproliferative epidermis, in which various alterations in the transmembrane signaling systems are well established. Since ras-proto-oncogenes are known to be activated by a single point mutation that is restricted to the amino acid residues either at position 12, 61 or in their vicinity, we investigated whether the increased expression of ras p21 in psoriatic epidermis is accompanied by mutation of the ras gene at these sites. The results obtained using samples from five cases of psoriasis revealed no evidence for such mutation. Although the psoriatic epidermis may exhibit enhanced expression of ras p21, this is apparently not accompanied by ras mutation.