Degree of CD25 expression in T-cell lymphoma is dependent on tissue site: implications for targeted therapy.

PURPOSE Using concurrent tumor samples from different anatomical sites, we compared expression of the therapeutic targets CD25 and CD30 in T-cell lymphoma (TCL). EXPERIMENTAL DESIGN We examined levels of CD25 and CD30 by flow cytometry in tumor cells from peripheral blood and lymph node in 13 cutaneous TCL patients and by immunohistochemistry in concurrent lymph node and skin biopsy specimens in 17 additional TCL cases, mostly mycosis fungoides. Tumor cell expression was correlated with patterns of expression in nonneoplastic lymphocytes in 14 reactive lymph node and 10 skin samples showing chronic dermatitis. Expression of CD25 and CD30 in all biopsy samples was compared with that of cutaneous lymphocyte antigen (CLA), a mediator of skin homing. RESULTS By flow cytometry, we noted significantly decreased expression of CD25 in lymph node compared with peripheral blood in 8 of 13 TCLs, with no changes in CD30 levels in 4 cases studied. Using immunohistochemistry, CD25 was strongly expressed in epidermotropic tumor cells in 13 of 17 (76%) TCL skin specimens but was decreased in the corresponding lymph node in 12 of these cases. CD30 was expressed at roughly equal intensity in tumor cells from both sites, except in 1 case. CLA showed a similar pattern to CD25, being expressed by tumor cells in 16 of 17 (94%) skin specimens, but was largely absent in tumor cells in the corresponding lymph node in 12 of these patients. In T cells from reactive lymph node biopsy specimens, CD25 was highly expressed only in dermatopathic lymphadenitis associated with transient skin rashes. CONCLUSIONS We demonstrate in vivo that decreased levels of CD25 expression occur in TCL when it involves lymph node, similar to what is seen with CLA. This demonstrable variation related to anatomical localization has implications for the measurement of surface expression of CD25 and for understanding the response of patients with cutaneous TCL to interleukin 2 receptor-targeted immunotherapy.