Everolimus (RAD001) and anti-angiogenic cyclophosphamide show long-term control of gastric cancer growth in vivo

Abstract

Metronomic dosing of cytotoxic drugs such as cyclophosphamide has shown anti-angiogenic activity, most likely by inducing hypoxia in tumors. Hypoxia leads to activation of escape mechanisms allowing tumor cell survival. This potentially limits the activity of anti-angiogenic strategies. We hypothesized that mTORC1 inhibition by everolimus (RAD001) leads to suppression of HIF-1α and VEGF resulting in synergistic anti-tumor activity in combination with anti-angiogenically dosed cyclophosphamide. In vitro, effects of everolimus on mTORC1 signaling, proliferation, cell cycle, HIF-1α expression and VEGF secretion were evaluated in two gastric cancer cell lines. In vivo, anti-tumor activity of everolimus in combination with metronomic cyclophosphamide was studied in a NCI-N87 human gastric cancer SCID mouse xenograft model. Expression of Ki-67 and HIF-1α, activated caspase 3, microvascular density (MVD) and tumor necrotic area was assessed.Everolimus decreased proliferation and attenuated production of HIF-1α as well as VEGF in gastric cancer cells in vitro. In vivo, everolimus significantly inhibited tumor growth. This anti-tumor activity was linked to a significant increase in tumor necrotic area (p