c-myc proto-oncogene expression in peripheral blood mononuclear cells from patients with primary Sjögren's syndrome

We examined peripheral blood mononuclear cells (PBMC) from 16 patients with Sjögren's syndrome (SS) and 7 normal control subjects for the expression of the c-myc proto-oncogene. Patients with SS were found to have a significantly increased expression of c-myc messenger RNA compared with normal individuals. No abnormal forms of c-myc RNA were detected in the SS patients. DNA analysis did not show deletion, rearrangement, or amplification in the c-myc proto-oncogene. The methylation status of the c-myc gene in patients with SS was found to be comparable with that of the control subjects. Nuclear run-off assays showed increased transcription of the c-myc gene in some patients but normal transcription in others, suggesting that posttranscriptional mechanisms are also involved in the increased c-myc messenger RNA observed in these patients. Two patients with primary SS and B cell lymphomas were found to have normal c-myc expression in their PBMC. These results demonstrate the presence of activated PBMC in patients with primary SS and delineate some of the mechanisms that are involved at the molecular level. We speculate that increased c-myc expression may represent an early permissive event in the progression toward neoplasia in these patients.