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

Expression of the p21ras protooncogene is reported to be increased in anima l models and in patients with SLE. However, the expression of p21ras regula tory elements has not been determined. We determined the expression of p21r as, and its regulatory elements p120-ras-GAP and hSOS, in PBMC of 10 patien ts with inactive SLE (mean SLEDAI score 1.8+/-0.53) and 10 age- and sex mat ched healthy controls. No difference was found between the two groups in th e levels of p21ras (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 compar ed to controls: 955+/-218 and 2306+/-327, P = 0.002, respectively. The mito gen-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 charac terized by reduced hSOS expression and underscore the need for a comprehens ive evaluation of p21ras pathway in these patients.