Everolimus (RAD001) and anti-angiogenic cyclophosphamide show long-term control of gastric cancer growth in vivo.
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-1alpha 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-1alpha 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-1alpha, activated caspase 3, microvascular density (MVD) and tumor necrotic area assessed. Everolimus decreased proliferation and attenuated production of HIF-1alpha 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 < 0.02) and trends for decreased proliferation, increased apoptosis, decreased HIF-1alpha and lower tumor MVD (p = n.s.). The combination of everolimus and cyclophosphamide resulted in a striking and highly significant long-term tumor growth control compared to monotherapy (p < 0.001), which was associated with a sharp increase in central tumor necrosis (p < 0.001). In conclusion, the combination of everolimus and metronomic cyclophosphamide showed synergistic anti-tumor activity. Depriving cancer cells by everolimus of factors necessary for their survival under hypoxia induced by anti-angiogenic chemotherapy appears to be a promising approach for treatment of gastric cancer.
Cejka
Daniel
D
Section of Experimental Oncology/Molecular Pharmacology, Department of Clinical Pharmacology, Medical University Vienna, Vienna, Austria.
Preusser
Matthias
M
Woehrer
Adelheid
A
Sieghart
Wolfgang
W
Strommer
Sabine
S
Werzowa
Johannes
J
Fuereder
Thorsten
T
Wacheck
Volker
V
D020533:Angiogenesis Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D053148:Caspase 3 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D003520:Cyclophosphamide / Q000494:pharmacology* / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D004789:Enzyme Activation / Q000187:drug effects; D000068338:Everolimus; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D009336:Necrosis / Q000473:pathology; D009389:Neovascularization, Pathologic / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D011897:Random Allocation; D020123:Sirolimus / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D013274:Stomach Neoplasms / Q000098:blood supply* / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D047368:Tumor Burden / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays / Q000379:methods
D020533:Angiogenesis Inhibitors; D000970:Antineoplastic Agents; D019394:Ki-67 Antigen; D003520:Cyclophosphamide; D000068338:Everolimus; D053148:Caspase 3; D020123:Sirolimus