The present invention concerns a biomarker useful in adoptive cell therapy. The biomarker in question is CD150, otherwise termed SLAM or SLAMF1. Herein we demonstrate that expression of CD150 on tumour infiltrating lymphocytes infusion products correlates with the response rate seen in those patients. High CD150 expression is found on patients who go on to have a complete response and low expression on patients who do not respond to therapy. The invention relates to the use of the biomarker to predict response rate or stratify patients for treatment. It also covers exploitation of this receptor in adoptive cell therapy regimens in general, including but not limited to over expression of the receptor in T-cell populations or isolation of cells expressing CD150 in an effort to increase efficacy.
