Triptolide synergistically enhances temozolomide-induced apoptosis and potentiates inhibition of NF-κB signaling in glioma initiating cells.
Glioblastoma multiforme (GBM) is a lethal solid cancer in adults. Temozolomide (TMZ) is a first-line chemotherapeutic agent but the efficacy is limited by intrinsic and acquired resistance in GBM. Triptolide (TPL), a derivative from traditional Chinese medicine, demonstrated anti-tumor activity. In this study, we explored the interaction of TPL and TMZ in glioma-initiating cells (GICs) and the potential mechanism. A GIC line (GIC-1) was successfully established. Cell viability of GIC-1 after treatment was measured using a CCK-8 assay. The interaction between TPL and TMZ was calculated from Chou-Talalay equations and isobologram. Self-renewal was evaluated with tumor sphere formation assay. Apoptosis was assessed with flow cytometry and western blot. Luciferase assay was employed to measure NF-κB transcriptional activity. The expression of NF-κB downstream genes, NF-κB nuclear translocalization and phoshorylation of IκBα and p65 were evaluated using western blot. We found that GIC-1 cells were resistant to TMZ, with the expected IC50 of 705.7 μmol/L. Co-treatment with TPL yielded a more than three-fold dose reduction of TMZ. TPL significantly increased the percentage of apoptotic cells and suppressed the tumor sphere formation when combined with TMZ. Phosphorylation of IκBα and p65 coupled with NF-κB nuclear translocalization were notably inhibited after a combined treatment. Co-incubation synergistically repressed NF-κB transcriptional activity and downstream gene expression. TPL sensitizes GICs to TMZ by synergistically enhancing apoptosis, which is likely resulting from the augmented repression of NF-κB signaling. TPL is therefore a potential chemosensitizer in the treatment of GBM.
Department of Neurosurgery/Neuro-Oncology, Sun Yat-Sen University Cancer Center, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China , State Key Laboratory of Oncology in South China, Guangzhou, China.
Ke
K
Sai
Wen-Yu
WY
Li
Yin-Sheng
YS
Chen
Jian
J
Wang
Su
S
Guan
Qun-Ying
QY
Yang
Cheng-Cheng
CC
Guo
Yong-Gao
YG
Mou
Wei-Ping
WP
Li
Zhong-Ping
ZP
Chen
D000818:Animals; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic / Q000187:drug effects / Q000235:genetics; D003606:Dacarbazine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D004195:Disease Models, Animal; D004224:Diterpenes / Q000494:pharmacology* / Q000627:therapeutic use; D004357:Drug Synergism; D004852:Epoxy Compounds / Q000494:pharmacology / Q000627:therapeutic use; D005910:Glioma / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology*; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000502:physiology*; D009368:Neoplasm Transplantation; D010616:Phenanthrenes / Q000494:pharmacology* / Q000627:therapeutic use; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D013268:Stimulation, Chemical; D000077204:Temozolomide; D014158:Transcription, Genetic / Q000187:drug effects; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism
D018906:Antineoplastic Agents, Alkylating; D004224:Diterpenes; D004852:Epoxy Compounds; D016328:NF-kappa B; D010616:Phenanthrenes; D019253:Proto-Oncogene Proteins c-bcl-2; D051636:X-Linked Inhibitor of Apoptosis Protein; C001899:triptolide; D003606:Dacarbazine; D000077204:Temozolomide