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Dimple R Bhatia,Padma Thiagarajan School of Biosciences and Technology, Vellore Institute of Technology University, Vellore, Tamil Nadu, India Aim: This study reports the influence of hypoxia on response of colorectal cancer cells to anticancer effects of sorafenib in combination with PI3K inhibitors GDC-0941 and BEZ-235.Materials and methods: All hypoxic exposures were carried out at 1% O2/5% CO2. Antiproliferation activity was evaluated by 48hours propidium iodide and 14days clonogenic assay. Protein levels were evaluated by fluorescence ELISA. Metabolites lactate and glucose were evaluated biochemically.Results: In the 48-hour proliferation assay, sorafenib acted synergistically with GDC-0941 but not with BEZ-235. In long-term colony-forming assays, both GDC-0941 and BEZ-235 were shown to potentiate the antiproliferative activity of sorafenib. At the molecular level, the synergism is mediated through inhibition of pAKT, pS6, p4EBP1, pERK, cyclin D1, and Bcl-2. No change in hypoxia-inducible factor-1α (HIF-1α) levels was observed in cells treated with the combination of compounds under hypoxia. A significant reduction in glucose uptake and lactate release was observed in cells treated with the combination of compounds under normoxia and hypoxia.Conclusion: Combinations of sorafenib with PI3K inhibitors BEZ-235 and GDC-0941 are efficacious under hypoxia. Thus, these anticancer combinations have a potential to overcome the hypoxia-mediated resistance mechanisms to antiproliferative agents in cancer therapy. Keywords: GDC-0941, BEZ-235, anticancer, antiproliferation

Dimple R Bhatia,Padma Thiagarajan School of Biosciences and Technology, Vellore Institute of Technology University, Vellore, Tamil Nadu, India Aim: This study reports the influence of hypoxia on response of colorectal cancer cells to anticancer effects of sorafenib in combination with PI3K inhibitors GDC-0941 and BEZ-235.Materials and methods: All hypoxic exposures were carried out at 1% O2/5% CO2. Antiproliferation activity was evaluated by 48hours propidium iodide and 14days clonogenic assay. Protein levels were evaluated by fluorescence ELISA. Metabolites lactate and glucose were evaluated biochemically.Results: In the 48-hour proliferation assay, sorafenib acted synergistically with GDC-0941 but not with BEZ-235. In long-term colony-forming assays, both GDC-0941 and BEZ-235 were shown to potentiate the antiproliferative activity of sorafenib. At the molecular level, the synergism is mediated through inhibition of pAKT, pS6, p4EBP1, pERK, cyclin D1, and Bcl-2. No change in hypoxia-inducible factor-1α (HIF-1α) levels was observed in cells treated with the combination of compounds under hypoxia. A significant reduction in glucose uptake and lactate release was observed in cells treated with the combination of compounds under normoxia and hypoxia.Conclusion: Combinations of sorafenib with PI3K inhibitors BEZ-235 and GDC-0941 are efficacious under hypoxia. Thus, these anticancer combinations have a potential to overcome the hypoxia-mediated resistance mechanisms to antiproliferative agents in cancer therapy. Keywords: GDC-0941, BEZ-235, anticancer, antiproliferation