As only the son had the major clinical manifestations of ALPS-FAS, miR-21-3p should be investigated as playing a critical role in ALPS physiopathology, including the development of lymphoma.
Our principal findings are that FAS mutations have a clinical penetrance of <60%, elevated serum vitamin B12 is a reliable and accurate biomarker of ALPS-FAS, and the major causes of morbidity and mortality in these patients are the overwhelming postsplenectomy sepsis and development of lymphoma.
In normal and lymphoma B cells, this correlated to increased CD95 membrane expression, enhanced DISC activity and engagement of the mitochondrial death pathway via Bid cleavage, although the latter occurred less efficiently in B-NHLr.
Fas receptor clustering and involvement of the death receptor pathway in rituximab-mediated apoptosis with concomitant sensitization of lymphoma B cells to fas-induced apoptosis.
A loss of FAS (CD95) function has been proposed to constitute an important step in early mucosa-associated lymphoid tissue (MALT) lymphoma development and FAS mutations have been recognized in malignant lymphomas, in particular at extranodal sites.
We demonstrate that CD95 mutations occur at low frequency in NHL tumors, however, surface expression of the CD95 protein varies with the subtype of lymphoma.
Fas (CD95, APO-1) mutations were found in autoimmune diseases and some lymphomas, suggesting impairment of Fas-mediated cell death signaling that may cause tumor development.
We conclude that the diagnosis of a FAS-FAS-L deficiency should be considered in children with an otherwise unexplained atypical lymphoproliferation and that a diagnosis of lymphoma in patients with functional FAS deficiency should be made with considerable reservation.