PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s): Tumors often contain hypoxic regions resistant to chemo- and radiotherapy. TH-302 is an investigational hypoxia-activated prodrug that selectively releases the DNA cross-linker bromo-isophosphoramide mustard under hypoxic conditions. TH-302 mainly acts on hypoxic condition instead of normal oxygen condition. There have been some phase II clinical trials of TH-302 in soft tissue sarcoma and pancreatic cancer, it shows that TH-302 has good effect on these tumors. Radiation is less sensitive to tumor cells on hypoxic conditon. This study is to investigate the effect of TH-302 combined with radiation in gastrointestinal tumors and the mechanism of TH-302 on hypoxic condition.
Materials/Methods: HCT116 cells, HT29 cells (both are intestinal cancer cells) and MKN28 cells (gastric cancer cells) are chosen for the following experiments. Firstly, 48h and 72h IC50s of TH-302 both on normal oxygen condition (O2%=21%) and hypoxic condition (O2%=1.3%) are obtained through drug cytotoxicity tests. Then tumor cells on hypoxic condition are dealt with TH-302 and radiation, CCK8 of the cells are tested. What’s more, cells are treated with TH302 (24h) on normal oxygen condition (O2%=21%) and hypoxic condition (O2%=1.3%) respectively. Cell apoptosis is examined using Flow Cytometry. At last, expression of HIF-1α protein related to hypoxia mechanism is examined through Western Blot and expression of HIF-1α gene is examined through qPCR.
Results: TH-302 is sensitive to tumor cells on hypoxic condition and has lower IC50.The 48h IC50 of TH-302 in HCT116 cells on normal oxygen and hypoxic condition is 2.8*10^8nmol/L and 2,074nmol/L respectively.In HT29 and MKN28 cells the data is 118,400 nmol/L vs 40,790 nmol/L and 29,143 nmol/L vs 1,473 nmol/L.TH-302 combined with radiation on hypoxic condition has more effect than radiation and TH-302 alone. The figure will be shown in the final paper. Tumor cells dealt with TH-302 have more apoptosis on hypoxic condition than normal oxygen condition. In HCT116 +/+, HCT116 -/-, MKN28 cells, the apoptosis ratio is 11.3% vs 0.9%, 17.0% vs 4.3% and 73.8% vs 16.5%. There is not much difference of HIF-1 gene expression between hypoxia and normal oxygen condition. ON hypoxic condition, tumor cells have higher HIF-1 protein expression level.
Conclusion: TH-302 is sensitive to tumor cells on hypoxic condition. TH-302 can be used as a radiosensitizer in gastrointestinal tumors. The mechanism of how TH-302 works on hypoxic condition has relationship with apoptosis.
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