APC and Familial adenomatous polyposis: Most importantly, the addition of RSPO1 to home-made WNT3A-CM or A+B led to the downregulation of the mTOR-downstream-effector phospho-S6 ribosomal protein (p-S6R), highlighting the activation of the RSPO1–pS6R in both non-APC (CRC-NM) and APC-mutated (FAP-NM) PDOs, independently from LGR5 gene expression modulation.