CXCR4 is a chemokine receptor frequently over-expressed on hematological cancers and solid tumors. CXCR4 and its ligand SDF1α (stromal derived factor-1α or CXCL12) play an important role in cancer metastasis, regulation of stem cell trafficking and neovascularization. We have observed previously that treatment with the small molecule CXCR4 antagonists Plerixafor (AMD3100, Mozobil) and AMD3465 in combination with Campath or Rituxan had a synergistic effect resulting in a prolongation of survival greater than that obtained with either agent alone in disseminated human B-lymphoma tumor models. We next explored the mechanism of action of CXCR4 antagonists in vitro using the human B-lymphoma cell lines Ramos, Raji, B104, BL31, IM9 or Wien133 which display similarly strong levels of cell surface CXCR4 expression. All cell lines responded to SDF1α but, in spite of comparable levels of CXCR4 expression, showed varying degrees of calcium influx and cell migration when stimulated. There was a good correlation between calcium influx and migratory responses for a given cell line. Addition of the CXCR4 antagonists Plerixafor or AMD3465 inhibited both responses. The compounds did not show any direct cytotoxicity and failed to inhibit spontaneous proliferation of Ramos, Raji and B104 human B-lymphoma cell lines. However, they did inhibit SDF1α-induced proliferation of these cell lines in agreement with their ability to block CXCR4. Moreover, CXCR4 antagonists inhibited SDF1α-induced phosphorylation of multiple proteins involved in cell migration, proliferation and survival signal pathways as well as some transcription factors, including Akt, ERK1/2, JNK, p70S6, p90RSK, GSK-3a/b, Tyk2, p38, MEK1, c-Jun, STAT3 and CREB.

These results suggest that the CXCR4/SDF1α axis plays an important role in the migration, proliferation and survival of human B-lymphoma cells and that disruption of these functions with CXCR4 antagonists may contribute to their observed ability to enhance the anti-tumor activity of Campath and Rituxan in human B-lymphoma models.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4460.