The mechanisms of extracorporeal photochemotherapy (ExP) therapeutic activity in cutaneous T-cell lymphomas (CTCLs) are not yet well understood, even though it has been suggested that a major mechanism may be induction of apoptosis. In vitro studies demonstrate that UVA-induced apoptosis is mediated by CD95-Fas expression and inhibited by Bcl-2 up-regulation and that UVA irradiation is able to down-regulate Bcl-2 expression. High-resolution multiparameter flow-cytometric analyses were used to evaluate Bcl-2/CD95-Fas expression on phenotypically identifiable circulating clonal T cells from 7 patients with CTCL (4 with Sézary syndrome and 3 with mycosis fungoides with peripheral involvement) before and during ExP, in an attempt to ascertain whether Bcl-2/CD95-Fas status can be related to the hematologic response. A Bcl-2 normal phenotype before ExP or a normalization in Bcl-2 expression during ExP were related to a better clinical response, whereas a persistent Bcl-2 high expression was a negative prognostic factor. On the other hand, no response was found in patients with a CD95-Fas-negative phenotype, whereas the expression of CD95-Fas was associated with hematologic remission. Although further studies are needed to confirm these preliminary results, this study suggests that Bcl-2 and CD95-Fas expression could be evaluated, together with the other known clinical and immunologic factors, as additional parameters related to clinical response in patients with CTCL undergoing ExP.
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