Direct evidence that bevacizumab, an anti-VEGF antibody, up-regulates SDF1alpha, CXCR4, CXCL6, and neuropilin 1 in tumors from patients with rectal cancer

Abstract

Clinical studies converge on the observation that circulating cytokines are elevated in most cancer patients by anti-vascular endothelial growth factor (VEGF) therapy. However, the source of these molecules and their relevance in tumor escape remain unknown. We examined the gene expression profiles of cancer cells and tumor-associated macrophages in tumor biopsies before and 12 days after monotherapy with the anti-VEGF antibody bevacizumab in patients with rectal carcinoma. Bevacizumab up-regulated stromal cell-derived factor 1alpha (SDF1alpha), its receptor CXCR4, and CXCL6, and down-regulated PlGF, Ang1, and Ang2 in cancer cells. In addition, bevacizumab decreased Ang1 and induced neuropilin 1 (NRP1) expression in tumor-associated macrophages. Higher SDF1alpha plasma levels during bevacizumab treatment significantly associated with distant metastasis at three years. These data show that VEGF blockade up-regulates inflammatory pathways and NRP1, which should be evaluated as potential targets for improving anti-VEGF therapy.

Figure 1

Changes in expression in cancer cells and TAMs from rectal carcinoma and in circulating plasma SDF1α levels after bevacizumab treatment. A, representative image of tumor tissue after selected tumor cells were burned by the capture laser and before RNA extraction (inset). B, selection of TAMs for LCM guided by CD68 immunostaining. Images of TAMs, burned by the capture laser of the cap containing TAMs (inset ; magnification, ×20). C, comparison of relative SDF1α and CXCR4 RNA levels in tumor cells captured by LCM from 12 pairs of serial biopsy samples collected before and 12 d after bevacizumab monotherapy. Columns, mean fold change in gene expression compared with pretreatment value. GAPDH was used as RNA control in the PCR. D, kinetics of plasma SDF1α after treatment with bevacizumab alone (day 12) and after bevacizumab with chemoradiation (day 32). Note the relatively high circulating levels of SDF1α (median of >1 ng/mL, shown with 95% confidence intervals) and the lack of consistent change in the overall population. Pre-Tx, pretreatment.