Grandifloridin D: A Potent Antiausterity Agent Targeting Pancreatic Cancer Cells via Akt/mTOR and Autophagy Inhibition

The hypovascular nature of pancreatic tumors creates a nutrient-scarce, hypoxic microenvironment, yet pancreatic cancer cells adapt by altering their metabolism to thrive under austere conditions-a phenomenon known as "austerity."Targeting this adaptation offers a promising strategy for next-generation therapeutics that selectively impair pancreatic cancer cell viability in nutrient-deprived states without toxicity under nutrient-rich conditions. Here, we evaluated the anti-pancreatic cancer properties of grandifloridin D, a synthetic derivative of (+)-grandifloracin. In vitro antiausterity assays demonstrated that grandifloridin D potently and preferentially reduced the viability of MIA PaCa-2 pancreatic cancer cells under nutrient deprivation at a PC50 concentration of 0.14 μM. Live-cell imaging and ethidium bromide/acridine orange (EB/AO) dual staining confirmed that grandifloridin D induces cell death by disrupting membrane integrity. Under nutrient-rich conditions, grandifloridin D exhibited antimetastatic activity, significantly inhibiting MIA PaCa-2 cell migration in real-time assays and suppressing colony formation and spheroid formation. Western blot analysis revealed that grandifloridin D is a potent inhibitor of the protein kinase B (Akt) and mammalian target of rapamycin (mTOR) signaling pathway while also suppressing the autophagy-related proteins microtubule-associated protein 1 light chain 3 (LC3). These results suggest that grandifloridin D is a promising antiausterity agent for pancreatic cancer drug development.