AKT is a central protein in many different cellular pathways, which involves cell survival, proliferation, glucose uptake, metabolism, angiogenesis, radiation response and drug response. The three isoforms of AKT, (AKT1, AKT2 and AKT3) are proposed to have different physiological functions, properties and expression patterns, in a cell type dependent manner. But not much is known about the influence of the different AKT isoforms in the whole genome and their effect in metabolism in colorectal cancer cells. We have previously shown that both AKT1 and AKT2 interact with the DNA-repair protein DNA-PKcs and that disruption of AKT1 and AKT2 increased the radiation sensitivity as well as influenced the expression of cancer stem cell markers CD44 and CD133.
In this study, the DLD-1 isogenic AKT 1-, AKT2-, and AKT1/2 knockout colon cancer cell lines were used as a model system together with the parental cell line in order to further elucidate the differences between the AKT isoforms and how they are involved in various cellular pathways. This was done using whole genome expression analyses, metabolomic analyses, and cell migration assays.
In conclusion, the downregulation of genes in the cell adhesion-, extracellular matrix- and Notch-pathway as well as upregulation of apoptosis and metastasis inhibitory genes in the p53-pathway confirms that the knockout of both AKT1 and 2 will attenuate metastasis and tumor cell growth. This was verified with a reduction in migration rate in the AKT1 KO and AKT2 KO, but mostly in the AKT1/2 KO. Furthermore, the knockout of AKT1, AKT2 or both, resulted in a reduction in lactate and alanine which suggests that the metabolism of carbohydrates and glutathione was impaired. This was also verified in the gene expression analysis, with a downregulation of genes involved in glucose metabolism. Additionally, both AKT1 KO and AKT2 KO had impaired fatty acid metabolism and folate biosynthesis, though possibly through different mechanisms.
However, genes were upregulated in the Wnt pathway and cell proliferation pathway which could oppose this effect. We therefore suggest that AKT inhibition should be combined with other drugs to attain the best effect.
Microarray, metabolism, cell migration AKT1, AKT2, AKT, PKB, gene expression, colon-cancer, DLD-1, metabolomics, CD44, CD133