Background: Andrographolide (Andro), a diterpenoid lactone, has been used for treatment of various cancers with less adverse effects. However, the underlying mechanisms regarding its anti-tumor mechanism still remain unclear. Methods: Cell viability and proliferation were measured by CCK8 and CFSE dilution assay. The localization of p50/p65 or cytochrome c was determined using confocal immunofluorescence. Streptavidin-agarose pulldown or ChIP assays were used to detect the binding of multiple transactivators to COX-2 promoter. The promoter activity was examined by a dual-Luciferase reporter assay. The functions of Andro on COX-2-mediated angiogenesis were also investigated using human HUVEC cells through tube formation and spheroids sprouting assay. The in vivo anti-tumor efficacy of Andro was analyzed in xenografts nude mice. Results: The results indicated that Andro could significantly inhibit the proliferation of human breast cancers, and suppress COX-2 expression at both protein and mRNA levels. Furthermore, Andro could dose-dependently inhibit COX-2-mediated angiogenesis in human endothelial cells. We have also found that Andro significantly promoted the activation of cytochrome c and activated caspase-dependent apoptotic signaling pathway. Our further explorations demonstrated that Andro inhibited the binding of the transactivators CREB2, C-Fos and NF-κB and blocked the recruitment of coactivator p300 to COX-2 promoter. Moreover, Andro could effectively inhibit the activity of p300 histone acetyltransferase (HAT), thereby attenuating the p300-mediated acetylation of NF-κB. Besides, Andro could also dramatically inhibit the migration, invasion and tubulogenesis of HUVECs in vitro. In addition, Andro also exhibited effective anti-tumor efficacy as well as angiogenesis inhibition in vivo. Conclusion: In current study, we explore the potential effects of Andro in suppressing breast cancer growth and tumor angiogenesis, as well as the precise mechanisms. This work demonstrated the potential anti-cancer effects of Andro, indicating that Andro could inhibit COX-2 expression through attenuating p300 HAT activity and suppress angiogenesis via VEGF pathway, and thereby could be developed as an antitumor agent for the treatment of breast cancer.

Gamabufotalin (CS-6), a major bufadienolide of Chansu, has been used for cancer therapy due to its desirable metabolic stability and less adverse effect. However, the underlying mechanism of CS-6 involved in anti-tumor activity remains poorly understood. The biological functions of gamabufotalin (CS-6) were investigated by migration, colony formation and apoptosis assays in NSCLC cells. The nuclear localization and interaction between transcriptional co-activator p300 and NF-κB p50/p65 and their binding to COX-2 promoter were analyzed after treatment with CS-6. Molecular docking study was used to simulate the interaction of CS-6 with IKKβ. The in vivo anti-tumor efficacy of CS-6 was also analyzed in xenografts nude mice. Western blot was used to detect the protein expression level. Gamabufotalin (CS-6) strongly suppressed COX-2 expression by inhibiting the phosphorylation of IKKβ via targeting the ATP-binding site, thereby abrogating NF-κB binding and p300 recruitment to COX-2 promoter. In addition, CS-6 induced apoptosis by activating the cytochrome c and caspase-dependent apoptotic pathway. Moreover, CS-6 markedly down-regulated the protein levels of COX-2 and phosphorylated p65 NF-κB in tumor tissues of the xenograft mice, and inhibited tumor weight and size. Our study provides pharmacological evidence that CS-6 exhibits potential use in the treatment of COX-2-mediated diseases such as lung cancer.

Background: Glioblastoma multiforme (GBM) is one of the most refractory and palindromic central nervous system (CNS) neoplasms, and current treatments have poor effects in GBM patients. Hence, the identification of novel therapeutic targets and the development of effective treatment strategies are essential. Alantolactone (ATL) has a wide range of pharmacological activities, and its anti-tumor effect is receiving increasing attention. However, the molecular mechanism underlying the anti-GBM activity of ATL remains poorly understood. Methods: The biological functions of ATL in GBM cells were investigated using migration/invasion, colony formation and cell cycle/apoptosis assays. The localization of nuclear factor kappa B (NF-κB) p50/p65 and its binding to the cyclooxygenase 2 (COX-2) promoter were determined using confocal immunofluorescence, a streptavidin-agarose pulldown assay and a chromatin immunoprecipitation (ChIP) assay. IKKβ kinase activity was determined using a cell IKKβ kinase activity spectrophotometry quantitative detection kit and a molecular docking study. LC-MS/MS analysis was performed to determine the ability of ATL to traverse the blood-brain barrier (BBB). The in vivo anti-tumor efficacy of ATL was also analyzed in xenografted nude mice. Western blot analysis was performed to detect the protein expression levels. Results: ATL significantly suppressed the growth of GBM in vivo and in vitro. ATL significantly reduced the expression of COX-2 by inhibiting the kinase activity of IKKβ by targeting the ATP-binding site and then attenuating the binding of NF-κB to the COX-2 promoter region. Furthermore, ATL induced apoptosis by activating the cytochrome c (cyt c)/caspase cascade signaling pathway. Moreover, ATL could penetrate the BBB. Conclusions: ATL exerts its anti-tumor effects in human GBM cells at least in part via NF-κB/COX-2-mediated signaling cascades by inhibiting IKKβ kinase activity. ATL, which is a natural small molecule inhibitor, is a promising candidate for clinical applications in the treatment of CNS tumors.

P23, historically known as a heat shock protein 90 (HSP90) co-chaperone, exerts some of its critical functions in an HSP90-independent manner, particularly when it translocates into the nucleus. The molecular nature underlying how this HSP90-independent p23 function is achieved remains as a biological mystery. Here, we found that p23 is a previously unidentified transcription factor of COX-2, and its nuclear localization predicts the poor clinical outcomes. Intratumor succinate promotes p23 succinylation at K7, K33, and K79, which drives its nuclear translocation for COX-2 transcription and consequently fascinates tumor growth. We then identified M16 as a potent p23 succinylation inhibitor from 1.6 million compounds through a combined virtual and biological screening. M16 inhibited p23 succinylation and nuclear translocation, attenuated COX-2 transcription in a p23-dependent manner, and markedly suppressed tumor growth. Therefore, our study defines p23 as a succinate-activated transcription factor in tumor progression and provides a rationale for inhibiting p23 succinylation as an anticancer chemotherapy.