Decreased expression of the p21ras stimulatory factor hSOS in PBMC from inactive SLE patients

Expression of the p21 ras protooncogene is reported to be increased in animal models and in patients with SLE. However, the expression of p21ras regulatory elements has not been determined. We determined the expression of p21ras, and its regulatory elements p120-ras-GAP and hSOS, in PBMC of 10 patients with inactive SLE (mean SLEDAI score 1.8+/-0.53) and 10 age- and sex-matched healthy controls. No difference was found between the two groups in the levels of p21 ras (3760+/-513 and 3367+/-335, P=0.25) and ras-GAP (1048+/-261 and 1534+/-247, P=0.11) in patients and controls, respectively. In contrast, levels of hSOS were significantly decreased in patients as compared to controls: 955+/-218 and 2306+/-327, P = 0.002, respectively. The mitogen-induced proliferative response was comparable in the two groups: SI 20.8+/-4.2 and 15.03+/-4.9, P=0.135, in patients and controls, respectively. Taken together, our data demonstrate that nonactive SLE patients are characterized by reduced hSOS expression and underscore the need for a comprehensive evaluation of p21ras pathway in these patients.