Mechanistic Study Of Transketolase And GRIM-19 In Regulating Cancer Cell Metabolism

Metabolic deregulation is a new hallmark of cancer cells.In order to achieve the goal of rapid proliferation,survival and metastasis,aerobic glycolysis and pentose phosphate pathway are up-regulated while mitochondrial respiration is inhibited in cancer cells.Studying metabolic regulation in cancer cells will provide novel strategies for cancer treatment.Studies have shown that the level of TKT is upregulated in human liver cancer when compared to non-malignant liver tissues.However,the role of TKT in initiation and progression of liver cancer remains to be elucidated.In our study,we generated a liver specific TKT knockout mice-TKT^fl/flAlb-cre,then induced liver cancer with diethylnitrosamine（DEN）and high fat diet（HFD）.We found that 100%wide type and around 95%heterozygote mice developed liver cancer whereas the tumor incidence decreased to 40%in TKT knockout mice at 9-month old following the DEN/HFD protocol.Our results showed that loss of TKT in liver attenuated the process from hepatic steatosis to liver fibrosis and liver cancer induced by DEN and HFD.The results demonstrated that TKT deficiency alleviated DEN-induced liver damage,increased apoptosis and reduced proliferation,on the other side,TKT deficiency downregulated the expression of proinflammatory factors TNF-α,IL-6 and activity of STAT3.In addition,metabonomics analysis indicated that TKT deficiency reduced cellular NADPH levels leading to ROS accumulation and increased apoptosis after DNA damage.Loss of TKT decreased Serine biosynthsis and deoxycholate levels,which might contribute to delayed liver cancer initiation and progression.The other part of the thesis mainly focuses on the roles of GRIM-19 which is a non-catalytic subunit of mitochondrial electron transport chain complex I in regulating HNSCC cell metabolism and proliferation.We found that endogenous levels of GRIM-19 mRNA and protein were positively correlated with oxygen consumption rates while negatively correlated with glycolytic activity in five HNSCC cell lines.Changing GRIM-19 expression in HNSCC cell lines could reprogram metabolic pathways,alter p53,STAT3 and HIF-1αsignalling and regulate cell proliferation.In conclusion,our research will not only help to elucidate how TKT and GRIM-19regulate tumor cell metabolism and proliferation,but also provide new strategies for designing therapeutic targets in liver cancer and HNSCC.