Inhibition of placental growth factor in renal cell carcinoma

Placental growth factor (PlGF) is up-regulated in major malignant diseases or following antiangiogenic therapy, although it is present in low levels under normal physiological conditions. TB403, a monoclonal antibody against PlGF, was investigated in clear cell renal cell carcinoma (ccRCC) xenografts since it has been proposed as a potential target in oncology. Human ccRCCs were implanted in athymic nude mice to evaluate the efficacy of TB403 and to excise xenograft tumors for molecular experiments. TB403 did not significantly inhibit tumor growth in treatment-naïve or sunitinib-resistant ccRCC xenografts. Gene expression profiling resulted in over-expression of the C1orf38 gene, which induced immunoreactivity in macrophages. Angiogenesis PCR arrays showed that VEGFR-1 was not expressed in ccRCC xenografts. PlGF blockade did not have a broad antiangiogenic efficacy; however, it might be effective on-target in VEGFR1-expressing tumors. The inhibition of VEGF pathway may induce the activity of tumor-associated-macrophages for angiogenesis escape.