Identification of a new HLA‐A*0201‐restricted cryptic epitope from CYP1B1

Cytochrome P450 1B1 (CYP1B1) was recently shown to be a candidate tumor antigen broadly expressed in solid and hematologic malignancies. Nevertheless, use of such self‐antigens as targets for immune intervention can be limited because of loss of high‐avidity T cells during negative selection in the thymus. Recent data suggest that targeting of cryptic epitopes may represent a way to circumvent such self‐tolerance and induce efficient antitumor CTL responses. Here, we present the identification and characterization of a novel, cryptic HLA‐A*0201‐binding peptide from CYP1B1. The nanomer CYP246 was identified by epitope deduction using algorithms to predict HLA‐A*0201‐binding peptides. CYP246 is characterized by strong initial HLA‐A*0201 binding but a short MHC/peptide binding half‐life. Expansion of high‐avidity CTL was readily possible using autologous CD40‐activated B cells from normal donors and cancer patients as antigen‐presenting cells, suggesting that an intact T‐cell repertoire can be expanded for this epitope. Lysis of CYP1B1‐expressing, HLA‐A*0201 + tumor cell lines and primary tumor cells confirmed that sufficient levels of CYP246 are presented by tumor cells for effector CTL killing. These findings indicate that CYP246 is a candidate cryptic epitope for immune interventions in which tumor CYP1B1 is targeted. © 2005 Wiley‐Liss, Inc.