Glioblastoma stem cells (GSCs) are the initiating cells in
glioblastoma multiforme (GBM) and contribute to the resistance of GBM to
chemotherapy and radiation. In the present study, we investigated the effects of
cardamonin (3,4,2,4-tetrahydroxychalcone) on the self-renewal and apoptosis of GSCs, and if its action is associated with
signal transducer and activator of transcription 3 (STAT3) pathway. CD133(+) GSCs, a kind of GSCs line, was established from human
glioblastoma tissues.
Cardamonin inhibited the proliferation and induced apoptosis in CD133+ GSCs. The proapoptotic effects of
temozolomide (TMZ) were further enhanced by
cardamonin in CD133+ GSCs and U87 cells in vitro. For in vivo study, injection of 5 × 10(5) cells of CD133+ GSCs subcutaneously (s.c.) into nude mice, 100 % of large
tumors were developed within 8 weeks in all mice; in contrast, only one out of five mice developed a small
tumor when 5 × 10(5) cells of CD133(-)
GMBs cells were injected.
Cardamonin also inhibited STAT3 activation by
luciferase assay and suppressed the expression of the downstream genes of STAT3, such as Bcl-XL, Bcl-2, Mcl-1,
survivin, and
VEGF. Furthermore,
cardamonin locked nuclear translocation and dimerization of STAT3 in CD133(+) GSCs. Docking analysis confirmed that
cardamonin molecule was successfully docked into the active sites of STAT3 with a highly favorable binding energy of -10.78 kcal/mol. The study provides evidence that
cardamonin is a novel inhibitor of STAT3 and has the potential to be developed as a new
anticancer agent targeting GSCs. This study also reveals that targeting STAT3 signal pathway is an important strategy for the treatment of human GBM.