CD44 VARIANT EXPRESSION IN CUTANEOUS T-CELL LYMPHOMA

Expression of the lymphocyte homing receptor CD44 and its splice varia nts have been linked to tumour dissemination and poor prognosis in non -Hodgkin's lymphoma. Specifically, the in vitro expression of variant exon V6 confers metastatic potential in rat pancreatic carcinoma cell lines. In this study, we investigated the expression of CD44 splice va riants in cutaneous T-cell lymphomas, including patients with mycosis fungoides (MF), Sezary syndrome (SS), large-cell anaplastic lymphoma ( LCAL) and HTLV1-associated cutaneous lymphoma. In addition, 4 involved lymph nodes from 2 patients with MF and 1 patient with SS were examin ed. Inflammatory dermatoses, lichen planus and psoriasis, and normal s kin were also studied. Immunohistochemistry was performed using a pane l of monoclonal antibodies, including those with specificity for CD44H (standard isoform) and variant exons V3, V6 and V8-9. Normal epiderma l keratinocytes were consistently CD44H and CD44 V3, V6 and V8-9 posit ive. In all the different clinicopathological subtypes and stages of c utaneous T-cell lymphomas, including involved lymph nodes, tumour cell s consistently expressed CD44H, but were CD44 V3 and V6 negative. CD44 V8-9 was expressed on a majority of tumour cells in 2/5 LCAL and on o ccasional tumour cells in 2/5 LCAL. Occasional V8-9 positive tumour ce lls were also identified in 6/13 MF, 1/4 SS and 3/4 HTLV1. In 2/3 lymp h node samples from 2 patients with tumour-stage MF, CD44 V8-9 express ion was found on a small percentage of atypical mononuclear cells. Sca ttered V8-9 positive dermal mononuclear cells were present in sections of lichen planus and psoriasis. We have found no evidence to suggest that the metastasis-associated CD44 variant exon (V6) is expressed in cutaneous T-cell lymphoma, or that CD44H expression is associated with an adverse prognostic group. It is not clear whether the strong expre ssion of CD44 V8-9 in 2 patients with CD30 positive LCAL reflects acti vation status or metastatic potential. (C) Munksgaard 1997.