Antisera induced by infusions of autologous Ad-CD154-leukemia B cells identify ROR1 as an oncofetal antigen and receptor for Wnt5a

*Moores Cancer Center, and
^‡Chronic Lymphocytic Leukemia Research Consortium, University of California at San Diego, La Jolla, CA 92093; and
^‖Memgen, Solana Beach, CA 92075

Contributed by Dennis A. Carson, December 28, 2007 (received for review December 5, 2007)

Abstract

We examined the sera of six patients before and after i.v. infusions of autologous chronic lymphocytic leukemia (CLL) cells transduced ex vivo with an adenovirus encoding CD154 (Ad-CD154). Five patients made high-titer antibodies against adenovirus and three made IgG reactive with a leukemia-associated surface antigen, which we identified as ROR1. Anti-ROR1 antibodies were not detected in the sera of untreated patients. We generated anti-ROR1 mAbs and found they reacted specifically with the CLL cells of all patients, but not with nonleukemic leukocytes, a wide variety of normal adult tissues, or blood mononuclear cells, including CD5⁺ B cells of healthy adults. ROR1 could bind Wnt5a, which induced activation of NF-κB when coexpressed with ROR1 in HEK293 cells and enhanced the survival of CLL cells in vitro, an effect that could be neutralized by posttreatment anti-ROR1 antisera. We conclude that patients with CLL can break immune tolerance to ROR1, which is an oncofetal surface antigen and survival-signaling receptor in this neoplastic disease.

Footnotes

**To whom correspondence may be addressed. E-mail: dcarson{at}ucsd.edu or tkipps{at}ucsd.edu
Author contributions: T.F. and L.C. contributed equally to this work; L.C. and T.J.K. designed research; T.F., L.C., T.E., L.T., D.L., J.E.C., G.F.W., L.Z.R., M.J.C., and T.J.K. performed research; T.E., L.Z.R., C.E.P., and T.J.K. contributed new reagents/analytic tools; T.F., L.C., T.E., D.L., G.F.W., D.A.C., and T.J.K. analyzed data; and T.J.K. wrote the paper.
↵ ^†Present address: Department of Hematology, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan.
↵ ^§Present address: Hokkaido University Graduate School of Medicine, N-15, W-7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan.
↵ ^¶Present address: Adventrx, 6725 Mesa Ridge Road, Suite 100, San Diego, CA 92121.
The authors declare no conflict of interest.