L'inibizione della via di trasduzione del segnale di PDK1 riduce la crescita ancoraggio-indipendente delle cellule di carcinoma colonrettale.

Colorectal cancer (CRC) is one of the most frequent neoplastic disease diagnosed in the world. The progressive accumulation of genetic and epigenetic alterations drives the transformation and progression of normal colon epithelial cells into an aberrant phenotype. RAS/MAPK and PI3K/AKT pathways are frequently altered in colorectal cancer and constitute one of the leading cause of tumor progression toward an aggressive and metastatic phenotype. Despite several efforts, no definitive therapies targeting these pathways are suitable to treat such type of cancer. 3-phosphoinositide-dependent kinase 1 (PDK1) is a serine/threonine kinase able to bind PIP3 produced by PI3K. Upon binding to PIP3 PDK1 phosphorylates and activates AKT. Furthermore PDK1 phosphorylates and activates RSK, which is a RAS/MAPK downstream effector. For these reasons we proposed PDK1 as common effectors of RAS/MAPK and PI3K/AKT pathway and our work is aimed to understand if PDK1 targeting could be suited to treat colorectal cancer. As experimental model we used, seven established cell lines of colorectal cancer harboring different somatic mutations, including mutations in RAS/MAPK and PI3K/AKT pathways. In these cell lines we inhibited PDK1 kinase activity using small molecule inhibitors and we tested cell survival both in adhesion and in anchorage independence. We showed that PDK1 inhibition poorly affects cell survival while efficiently abrogated anchorage-independent growth with different sensitivity among the cell lines. Then, we evaluated the effect of the PDK1 inhibition on its downstream effectors. Both AKT and RSK phosphorylation was abolished by PDK1 silencing. Therefore, we tested the effect of the inhibition of AKT and RSK on anchorage-independent growth, and we observed that only RSK inhibition, but not AKT inhibition, correlated with PDK1 inhibition. Moreover, we tested PDK1 role in colorectal cancer culture in 3D gel matrix, where colon cancer cells formed large lumen-containing or disorganised organoids. We found that PDK1 inhibition profoundly alters 3D morphogenesis of these colorectal cancer cells. Furthermore we showed that RSK inhibition , had similar effect to PDK1 inhibition. In contrast, AKT inhibition, which affects exclusively the PI3K/AKT pathway, did not correlate with PDK1 inhibition. In summary we propose PDK1 as a possible target to inhibit tumor growth of CRC harboring mutations in RAS/MAPK and PI3K/AKT pathways.