Research Information System
EACR 2023: Innovative Cancer Science, Turin, Italy, 12 - 15 June 2023, vol.17, pp.481-482
Introduction
Temozolomide (TMZ) resistance is a major challenge for Glioblastoma (GB). Hypoxia leads to aggressive GB tumor phenotype and TMZ therapy failure. Diet-derived flavonoids show chemopreventive effects on cancer. Among these flavonoids, fisetin (FIS) promises anticancer effects through its antiproliferative and apoptotic properties. Therefore, this study investigated the impact of FIS on GB and its potential as a complementary therapy to prevent TMZ resistance in hypoxic conditions in-vitro GB models.
Material and Methods
The effect of FIS and TMZ-FIS was analyzed in GB cell lines, TMZ-resistant T98G, and TMZ-sensitive A172. The murine fibroblast cell, L929, was used as a non-cancerous cell line. The type of combined effect of FIS and TMZ was detected by SynergyFinder (version 3.0). Cell proliferation was assessed by real-time cell monitoring and colony formation. An annexin V assay analyzed the cell viability in TMZ-resistant T98G cells. A scratch wound-healing assay showed the difference in the migration rate of T98G and A172 cells in normoxia and hypoxia (1% O2, 5% CO2, 94% N2). Data were confirmed by a hypoxic GB tumor model using 3D tumor spheres of TMZ-resistant T98G cells.
Results and Discussions
The 13.78uM and 16.40uM of FIS were detected as IC50 values over 24 hours in A172 and T98G cells, respectively (p<0,05). In contrast, these concentrations were ineffective in the fibroblast cell, L929. In normoxia, FIS induced apoptosis (p<0.0001) and additively affected the apoptosispromoting capacity of TMZ in TMZ-resistant T98G cells (p<0,0001). In addition, the number of colonies formed by T98G and A172 cells decreased, and their migration rates slowed upon FIS and FIS-TMZ treatments compared to untreated and TMZ-only treated cells (p<0.0001). In hypoxia, where GB cells became more resistant to chemotherapy, FIS reduced the excessive migration rate of TMZ-resistant T98G cells compared to untreated cells. Moreover, FIS-TMZ treatments increased the anti-invasive effect of TMZ in T98G cells (p<0.0001). In support of this, FIS and TMZ equally decreased the size of 3D tumor spheres formed by T98G cells, and FIS-TMZ decreased the size of tumor spheres more strongly compared to TMZonly (p<0.0001).
Conclusion
Our findings showed that FIS reduces hypoxia-induced
TMZ resistance and contributes to the tumor-healing effect
of TMZ, suggesting that FIS could be a promising additive
therapy to TMZ for GB patients. The underlying
mechanism of this effect of FIS is an open area to clarify in
future drug development research.