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.

Stroma cells: a novel target of herceptin activity.

PURPOSE: Stroma cells play a relevant role in tumor development and progression. We investigated the activity of herceptin (HER), a humanized monoclonal antibody widely used for the treatment of HER2-overexpressing epithelial cancer, toward stroma cell lines L87/4 and L88/5. EXPERIMENTAL DESIGN: We studied the antiproliferative potential of HER and role of human serum in HER activity. We also investigated the ability of HER to alter ancillary functions of L87/4 and L88/5, such as support to long-term hematopoiesis, growth factor production, breast cancer cell adhesion, and proliferation. RESULTS: Flow cytometry showed that HER2 membrane expression in L87/4 and L88/5 stroma cells was intermediate between the expression in HER2-negative/dim MCF-7 breast cancer cells and HER2-bright SK-BC3 breast cancer cells. HER2 gene amplification was not detected by fluorescence in situ hybridization in either stromal cell lines. HER significantly inhibited L87/4 and L88/5 proliferation. Mean ID(50)s were found to be 2000 and 1700 micro g/ml for L87/4 and L88/5, respectively, after 3-day exposure and 800 micro g/ml for both cell lines after 9-day exposure. The presence of 10% human serum in the culture increased HER inhibitory activity. IC(50) of stroma cells was found to be intermediate between HER2-bright breast cancer cells (SK-BC3) and HER2-negative/dim breast cancer cells (MCF-7). The drug did not significantly affect the ability of stroma cells to support long-term hematopoiesis in the cobblestone area forming cell assay. In contrast, in coculture assay, MCF7 cells demonstrated a worse adhesion and growth capability on HER-treated stroma layers when compared with untreated stroma. Moreover, HER significantly reduced vascular endothelial growth factor production by L88/5 cells. CONCLUSIONS: Our data support the novel finding that HER may have a relevant activity against stroma cells.