Prec-O1-03 - Understanding the function of CD30 in cutaneous T-cell lymphoma: implications for therapy and prognosis

Abstract

<h3>Introduction and objectives:</h3> Targeted therapies for cutaneous T-cell lymphoma (CTCL) are limited and curative approaches are still lacking. Relapses and drug-induced side effects are major challenges in the therapeutic management of CTCL patients, resulting in an urgent need for new, effective therapies. Expression of CD30 receptor is usually restricted to a small population of activated B- and T-cells, but is also found in hematologic malignancies, such as CTCL. In mycosis fungoides (MF) its expression seems to be associated with advanced disease stage and large-cell transformation. However, the functional role of CD30 in CTCL remains unknown. Consequently, this study aims to determine 1) CD30 and CD30 ligand (CD30L) expression in CTCL cell lines and primary CD4-positive cells from CTCL patients, 2) the dynamics of CD30 expression over time and after treatment, 3) CD30 function <i>in vitro</i>, <i>ex vivo</i> and <i>in vivo</i>, 4) mechanisms involved in CD30 signaling. <h3>Materials and methods:</h3> The CTCL cell lines HH, SeAx and HUT-78 were used for <i>in vitro</i> experiments. For <i>ex vivo</i> analysis, primary CD4-positive T-cells isolated from fresh blood samples of patients with Sézary syndrome were used. Cells were challenged with dimethyl fumarate for 24 hours. CD30 was stimulated via its natural ligand. Methods used for expression and pathway analysis were FACS, western blot, PCR and luciferase assay. For <i>in vivo</i> experiments, CTCL cells were suspended in PBS/Matrigel (1:1, vol/vol) and injected intradermally into the right flank of female NOD/SCID/Il2Rg null (NSG) mice. After development of tumors, CD30L was injected into the lesions. <h3>Results:</h3> We found that CD30 activation can influence viability of CTCL cells <i>in vitro</i>, which is currently under investigation in an <i>in vivo</i> setting. Involved mechanisms include the MEK/ERK and NF-κB pathway. The highest CD30 expression was detected in the HH cell line. The primary CD4-positive cells analyzed so far were negative for CD30 surface expression. However, intracellular CD30 protein was detectable via western blot. CD30 levels were influenced by cell culture conditions in HH cells and significantly reduced upon therapeutic NFκB inhibition in HH, SeAx and HUT-78 cells. <h3>Conclusions:</h3> Our results indicate a therapeutic potential of CD30 receptor stimulation as a new targeted therapy in CD30-positive MF <i>in vitro</i>, which has to be proven <i>in vivo</i>. Furthermore, we found a dynamic nature of CD30 expression in CTCL, which might account for the described effectiveness of the antibody-drug conjugate brentuximab vedotin directed to CD30 also in patients diagnosed as CD30 low-expressing.