Fig. 4: Expression of mTOR and its upstream suppressor PTEN, in colon organoids.

A The schematic diagram for mTOR signaling pathway. In response to growth factors, PI3K is activated and phosphorylates AKT, which inactivates the tuberous sclerosis (TSC) tumor suppressor protein, the RAS homolog enriched in brain (Rheb) small G protein which activates mTOR. Activated mTOR phosphorylates S6K1 kinase which activates translation, cell growth, and proliferation. In parallel, phosphorylation and inactivation of 4E-BP1 activates eIF4E which leads to protein synthesis, cell growth, and proliferation. B Immunohistochemical staining of phospho-mTOR (p-mTOR) in normal colon tissue, and day 45 organoids derived from isogenic control FAP1, FAP1, and FAP2. Normal colon tissue served as a control for protein expression within the normal environment. This experiment was repeated twice, and representative pictures are shown. p-mTOR expression quantification utilized the open-source image analysis software Ilastik (version 1.4.1rc2), ****P < 0.0001, t test. C Immunohistochemical staining of the tumor suppressor protein PTEN in day 45 organoids derived from isogenic FAP1, FAP1, FAP2, and normal colon tissue served as a control. X10- Scale bars- 100 µm, X20- Scale bars- 200 µm.