Phospho-S6 Ribosomal Protein (Ser240/244) refers to the phosphorylated form of the S6 ribosomal protein at serine residues 240 and 244. This post-translational modification is crucial for the protein's role in regulating protein synthesis and cell growth. The phosphorylation of S6 is often induced by various growth factors and is mediated by the mammalian target of rapamycin (mTOR) through its downstream effector, the ribosomal protein S6 kinase (S6K). In the context of cell signaling, Phospho-S6 Ribosomal Protein (Ser240/244) serves as a marker for the activation of the mTOR pathway, which is involved in various cellular processes, including cell proliferation, metabolism, and survival. The mTOR pathway is frequently deregulated in cancer, making Phospho-S6 a potential biomarker for cancer diagnosis and prognosis, as well as a target for therapeutic interventions. Moreover, the level of phospho-S6 ribosomal protein has been correlated with the efficacy of mTOR inhibitors in clinical trials, suggesting its potential as a predictive marker for response to therapy.