Maintenance of antiangiogenic and antitumor effects by orally active low-dose capecitabine for long-term cancer therapy.

Long-term uninterrupted therapy is essential for maximizing clinical benefits of antiangiogenic drugs (AADs) in cancer patients. Unfortunately, nearly all clinically available AADs are delivered to cancer patients using disrupted regimens. We aim to develop lifetime, nontoxic, effective, orally active, and low-cost antiangiogenic and antitumor drugs for treatment of cancer patients. Here we report our findings of long-term maintenance therapy with orally active, nontoxic, low cost antiangiogenic chemotherapeutics for effective cancer treatment. In a sequential treatment regimen, robust antiangiogenic effects in tumors were achieved with an anti-VEGF drug, followed by a low-dose chemotherapy. The nontoxic, low dose of the orally active prodrug capecitabine was able to sustain the anti-VEGF-induced vessel regression for long periods. In another experimental setting, maintenance of low-dose capecitabine produced greater antiangiogenic and antitumor effects after AAD plus chemotherapy. No obvious adverse effects were developed after more than 2-mo of consecutive treatment with a low dose of capecitabine. Together, our findings provide a rationalized concept of effective cancer therapy by long-term maintenance of AAD-triggered antiangiogenic effects with orally active, nontoxic, low-cost, clinically available chemotherapeutics

Off-tumor targets compromise antiangiogenic drug sensitivity by inducing kidney erythropoietin production.

Anti-VEGF drugs are commonly used for treatment of a variety of cancers in human patients, and they often develop resistance. The mechanisms underlying anti-VEGF resistance in human cancer patients are largely unknown. Here, we show that in mouse tumor models and in human cancer patients, the anti-VEGF drug-induced kidney hypoxia augments circulating levels of erythropoietin (EPO). Gain-of-function studies show that EPO protects tumor vessels from anti-VEGF treatment and compromises its antitumor effects. Loss of function by blocking EPO function using a pharmacological approach markedly increases antitumor activity of anti-VEGF drugs through inhibition of tumor angiogenesis. Similarly, genetic loss-of-function data shows that deletion of EpoR in nonerythroid cells significantly increases antiangiogenic and antitumor effects of anti-VEGF therapy. Finally, in a relatively large cohort study, we show that treatment of human colorectal cancer patients with bevacizumab augments circulating EPO levels. These findings uncover a mechanism of desensitizing antiangiogenic and anticancer effects by kidney-produced EPO. Our work presents conceptual advances of our understanding of mechanisms underlying antiangiogenic drug resistance