CXCR4 neutralization, a novel therapeutic approach for non-Hodgkin's lymphoma.

The chemokine stromal cell-derived factor-1 (CXCL12/SDF-1) and its monogamous receptor CXCR4 are involved in trafficking of B cells and hematopoietic progenitors. CXCR4 expression was found in the large majority of non-Hodgkin's lymphoma (NHL) cell lines and primary cells, and CXCR4 neutralization by monoclonal antibodies had profound in vitro effects on NHL cells including inhibition of transendothelial/stromal migration, enhanced apoptosis, decreased proliferation, and inhibition of pseudopodia formation. In a nonobese diabetes/severe combined immunodeficiency (NOD/SCID) mouse model of human high-grade NHL, CXCR4 neutralization had an impressive efficacy. In a first tumor-challenge trial, CXCR4 neutralization of Namalwa cells injected i.p. delayed tumor growth and reduced tumor weight. In a second tumor-challenge trial, NOD/SCID mice received Namalwa cells i.v. All of the controls died of neoplasia within day 36, whereas 83% of mice injected with cells incubated with anti-CXCR4 were still alive and disease-free >150 days after transplant. The crucial role of CXCR4 in tumor cell extravasation was confirmed by the finding that CXCR4 neutralization before i.v. injection of Namalwa cells in NOD/SCID mice increased the number of cancer cells circulating 24 h after injection. In additional preclinical trials, the therapeutic effect of anti-CXCR4 antibodies was evaluated in mice bearing Namalwa cells injected 3 days before. Tumor growth was abrogated in the majority of treated mice and significantly delayed in the remaining group. Taken together, these data support clinical studies on CXCR4 neutralization in NHL patients by monoclonal antibodies or CXCR4 antagonists.