Cytotoxic and senescence-inducing effects of BLU554 in pancreatic ductal adenocarcinoma: an in vitro study.

BACKGROUND: Fibroblast growth factor receptor 4 (FGFR4) is overexpressed in up to 50% of pancreatic ductal adenocarcinoma (PDAC) cases. BLU9931, a selective FGFR4 inhibitor, exerts cytotoxic effects on PDAC cells and induces cellular senescence. This study aimed to investigate the effects of BLU554, another selective FGFR4 inhibitor, whose efficacy and safety in hepatocellular carcinoma has been proven in clinical trials, on PDAC cell lines. METHODS: BLU554 was applied to PDAC cell lines, and cytotoxicity in PK-1 and T3M-4 cells was assessed by counting viable cells. BLU554-induced senescence was detected using γH2AX immunocytochemical staining; qualitative polymerase chain reaction (qPCR) analysis of CDKN1A, LMNB1, and senescence-associated secretory phenotype (SASP) factors; transmission electron microscopy of lysosomal structures and numbers; and the senescence-associated-β-galactosidase assay. In addition, we assessed whether dasatinib and quercetin, two representative senolytic agents, could reduce the viability of BLU554-treated cells, using an ATP assay. RESULTS: BLU554 suppressed the growth of PK-1 and T3M-4 cells, which express high FGFR4 levels, with a stronger effect in T3M-4 cells. Cellular senescence, which can be triggered by chemotherapy-induced stress, was induced in both PK-1 and T3M-4 cells, as evidenced by elevated γH2AX expression. Treatment with BLU554 increased the number of PDAC cells exhibiting lysosomal enzyme activity abnormalities, as indicated by SA-β-galactosidase staining. The number of PDAC cells showing lysosomal morphological alterations, observed under transmission electron microscopy, also increased. Increased CDKN1A and decreased LMNB1 mRNA levels, combined with changes in the expression of SASP factors, further confirmed the induction of cellular senescence. Application of the senolytic drugs dasatinib or quercetin significantly reduced the viability of BLU554-treated cells, which are associated with increased malignancy. CONCLUSIONS: This two-step strategy may represent a novel therapeutic approach for the treatment of therapy-resistant PDAC through senescence induction and subsequent senolysis.