A method comprising: inferring activity of a PI3K cellular signaling pathway in a tissue and/or cells and/or a body fluid of a medical subject based at least on expression levels of one or more target gene(s) of the PI3K cellular signaling pathway measured in an extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, wherein the inferring comprises: determining a level of a FOXO transcription factor element in the extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, the FOXO TF element controlling transcription of the one or more target gene(s) of the PI3K cellular signaling pathway, the determining being based at least in part on evaluating a mathematical model relating expression levels of the one or more target gene(s) of the PI3K cellular signaling pathway to the level of the FOXO TF element; inferring the activity of the PI3K cellular signaling pathway in the tissue and/or the cells and/or the body fluid of the medical subject based on the determined level of the FOXO TF element in the extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, wherein the inferring is performed by a digital processing device using the mathematical model. inferring activity of a PI3K cellular signaling pathway in a tissue and/or cells and/or a body fluid of a medical subject based at least on expression levels of one or more target gene(s) of the PI3K cellular signaling pathway measured in an extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, wherein the inferring comprises: determining a level of a FOXO transcription factor element in the extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, the FOXO TF element controlling transcription of the one or more target gene(s) of the PI3K cellular signaling pathway, the determining being based at least in part on evaluating a mathematical model relating expression levels of the one or more target gene(s) of the PI3K cellular signaling pathway to the level of the FOXO TF element; inferring the activity of the PI3K cellular signaling pathway in the tissue and/or the cells and/or the body fluid of the medical subject based on the determined level of the FOXO TF element in the extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, determining a level of a FOXO transcription factor element in the extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, the FOXO TF element controlling transcription of the one or more target gene(s) of the PI3K cellular signaling pathway, the determining being based at least in part on evaluating a mathematical model relating expression levels of the one or more target gene(s) of the PI3K cellular signaling pathway to the level of the FOXO TF element; inferring the activity of the PI3K cellular signaling pathway in the tissue and/or the cells and/or the body fluid of the medical subject based on the determined level of the FOXO TF element in the extracted sample of the tissue and/or the cells and/or the body fluid of the medical subject, wherein the inferring is performed by a digital processing device using the mathematical model.