Maslinic acid derivative induces the death of transitional bladder cancer cells through apoptosis and autophagy via the PI3K-AKT signaling pathway.

l-Phenylalanine and l-glutamine were conjugated with maslinic acid and 3-epi maslinic acid to generate 16 derivatives. Most of them exhibited higher cytotoxic activity than maslinic acid towards various tumour cell lines. Based on the results from the human apoptosis array and western blotting assays, derivative 7, a 2α,3β-dipropionylated maslinic acid-l-phenylalanine conjugate, could promote autophagy and intrinsic and extrinsic apoptosis in the T24 cell line in a dose-dependent manner. Furthermore, 7 could decrease the mitochondrial membrane potential and overload mitochondrial Ca2+ and ROS. These effects can lead to significant apoptosis induction and activate apoptotic signaling via caspase-8 and caspase-9. In addition, 7 could decline proliferation activity by inhibiting the expression of the PI3K, AKT and EGFR proteins. RNA-seq analysis suggested that 7 can induce the formation of autophagosomes by upregulating WIPI1, p62, LC3B-I/II, and Beclin-1. Meanwhile, western blotting analysis revealed that 7 could simultaneously upregulate the pro-apoptotic factors (Bax and Bak) and autophagy proteins (Beclin-1, LC3B II/I, PI3-kinase class III, mTOR and p62). This implies that 7 could synergistically promote apoptosis and autophagy to induce cell death.