ab17_3

Lack of Fas and Fas-L mutations in patients with lymphoproliferative disorders associated with Sjögren's syndrome and type II mixed cryoglobulinemia

F. Bertolo¹, S. De Vita², R. Dolcetti¹, A. Carbone³, G.F. Ferraccioli², E. Bartoli², M. Boiocchi¹

Divisions of ¹Experimental Oncology I and ³Pathology, Centro di Riferimento Oncologico, Aviano; ²Rheumatic Disease Unit and Department of Internal Medicine, University of Udine, Udine, Italy.

ABSTRACT
Objective
Murine models (MRL/gld/gld mice) and recent evidence in humans suggest a possible role of Fas and Fas ligand (Fas-L) germline mutations in the pathogenesis of autoimmune-related lymphoproliferation, including adult cases. In this study, the presence of Fas and Fas-L germline mutations was investigated in a consecutive series of adult patients with lymphoproliferative disorders occurring in the context of Sjögren’s syndrome (SS) and type II mixed cryoglobulinemia (MC).

Methods
Eleven patients (8 primary SS and 3 type II MC; F/M: 10/1; mean age 64 yrs.) were investigated. All patients were suffering from atypical lymphoproliferative disorders or MALT lymphoproliferative lesions (mean duration 3.5 yrs.). Four patients later developed a malignant lymphoma. DNA from peripheral blood mononuclear cells from 11 patients and 10 controls was tested for germline mutations in the Fas gene (exons 4, 8 and 9) and Fas-L gene (exon 4) by the polymerase chain reaction-single strand conformation polymorphism (SSCP) method.

Results
All DNA samples from both patients and controls showed amplification of Fas and Fas-L specific fragments. Identical SSCP migration patterns were observed in all the cases, indicating the lack of mutations in the whole series.

Conclusion
Although it cannot be excluded that Fas and Fas-L mutations might be present in exons different from those analyzed, our data do not support the hypothesis that germline mutations in these genes are responsible for a major subset of lymphoproliferative syndromes in adult patients with SS and type II MC. Additional studies would be worthwhile in SLE-related lymphoproliferation, which is, however, a subset of limited clinical relevance when considering all cases with autoimmune-related lymphoproliferation.

Key words:
Fas, Fas ligand, Sjögren’s syndrome, cryoglobulinemia, lymphoma.

Please address correspondence and reprints requests to: Dr. Mauro Boiocchi, Division of Experimental Oncology 1, Centro di Riferimento Oncologico, Via Pedemontana Occidentale 12, 33081 Aviano (PN) Italy.