Novel 1-benzyl-oxindole indole hybrids targeting PDGFR-β, SRC, and c-MET signaling and inducing caspase-3-dependent apoptosis in pancreatic cancer cells

As part of our ongoing efforts to develop N-benzylated oxindole derivatives as multi-target anticancer agents, novel N-benzyl oxindole indoles (4a–z) were designed, synthesized and structurally characterized. Their cytotoxic activities were evaluated against HCT-116, HT-29, A549, MIA PaCa-2, A498, CAKI-1, MDA-MB-231, and MCF-7 cancer cells, as well as Beas2b noncancerous cells. Most compounds exhibited significantly stronger cytotoxicity and selectivity than the reference drug sunitinib malate. Mechanistic studies were performed on compounds 4a, 4b, 4d, 4g, 4i, 4q, and 4y, which displayed submicromolar cytotoxic effects (IC50 = 0.27- 0.97 μM) and high selectivity indices (SI = 91.3->370.4). Among these, compounds 4a, 4b, and, 4i, which exhibited stronger cytotoxic effects than sunitinib malate, significantly induced apoptosis and markedly suppressed general tyrosine kinase (TK) activity. Compounds 4a (IC50 = 0.27 μM, SI = 167.8) and 4b (IC50 = 0.48 μM; SI = 91.2) markedly reduced PDGFR-β and SRC signaling, and inhibited ERK signaling more potently than sunitinib malate (IC50 = 4.03 μM, SI = 3.2) in MIA PaCa-2 cells. Notably, compound 4a also exhibited stronger reduction c-MET signaling than sunitinib malate, whereas compound 4b was less effective against this target. Overall, compound 4a displayed the most potent multi-target inhibitory profile and was identified as lead candidate. Molecular docking studies further supported its stable binding within the ATPbinding pockets of PDGFR-β, SRC, and c-MET kinases, consistent with its observed inhibitory activity. Further mechanistic studies demonstrated that compound 4a induces caspase-3-mediated apoptosis through a Bax/Bcl-2- independent pathway, accompanied by increased levels of cytochrome c and p53. Collectively, these findings identify compound 4a as a potent, selective, and multi-target lead candidate for further development against pancreatic cancer.