The small-molecule drug homoharringtonine targets HSF1 to suppress pancreatic cancer progression.

Heat shock factor 1 (HSF1), an essential transcription factor for stress response, is exploited by various tumors to facilitate their initiation, progression, invasion, and migration. Amplification of HSF1 is widely regarded as an indicator in predicting cancer severity, the likelihood of treatment failure and reduced patient survival. Notably, HSF1 is markedly amplified in 40% of pancreatic cancer (PC), which typically have limited treatment options. HSF1 has been proven to be a promising therapeutic target for multiple cancers. However, a direct small molecule HSF1 inhibitor with sufficient bioactivity and reliable safety has not been developed clinically. In this study, we successfully established a high-throughput screening system utilizing luciferase reporter assay specifically designed for HSF1, which leads to the discovery of a potent small molecule inhibitor targeting HSF1. Homoharringtonine (HHT) selectively inhibited PC cell viability with high HSF1 expression and induced a markedly stronger tumor regression effect in the subcutaneous xenograft model than the comparator drug KRIBB11, known for its direct action on HSF1. Moreover, HHT shows promise in countering the resistance encountered with HSP90 inhibitors, which have been observed to increase heat shock response intensity in clinical trials. Mechanistically, HHT directly bound to HSF1, suppressing its expression and thereby inhibiting transcription of HSF1 target genes. In conclusion, our work presents a preclinical discovery and validation for HHT as a HSF1 inhibitor for PC treatment.

The natural product trienomycin A is a STAT3 pathway inhibitor that exhibits potent in vitro and in vivo efficacy against pancreatic cancer.

BACKGROUND AND PURPOSE: Pancreatic cancer is an exceptionally fatal disease. However, therapeutic drugs for pancreatic cancer have presented a serious shortage over the past few decades. Signal transducer and activator of transcription-3 (STAT3) is persistently activated in many human cancers where it promotes tumour development and progression. Natural products serve as an inexhaustible source of anticancer drugs. Here, we identified the natural product trienomycin A (TA), an ansamycin antibiotic, as a potential inhibitor of the STAT3 pathway with potent activity against pancreatic cancer. EXPERIMENTAL APPROACH: Effects of trienomycin A on transcriptional activity of STAT3 were assessed by the STAT3-luciferase (STAT3-luc) reporter system. In vitro and in vivo inhibitory activity of TA against pancreatic cancer made use of molecular docking, surface plasmon resonance (SPR) assay, MTS assay, colony formation assay, transwell migration/invasion assay, flow cytometric analysis, immunofluorescence staining, quantitative real-time polymerase chain reaction (PCR), western blotting, tumour xenograft model, haematoxylin and eosin (H&E) staining and immunohistochemistry. KEY RESULTS: Trienomycin A directly bound to STAT3 and inhibited STAT3 (Tyr705) phosphorylation, thus inhibiting the STAT3 pathway. Trienomycin A also inhibited colony formation, proliferation, migration and invasion of pancreatic cancer cell lines. Trienomycin A also markedly blocked pancreatic tumour growth in vivo. More importantly, trienomycin A did not show obvious toxicity at the effective dose in mice. CONCLUSIONS AND IMPLICATIONS: Trienomycin A exerted anti-neoplastic activity by suppressing STAT3 activation in pancreatic cancer. This natural product could be a novel therapeutic candidate for pancreatic cancer.

Synthesis of novel heterocyclic ring-fused 18ß-glycyrrhetinic acid derivatives with antitumor and antimetastatic activity.

Glycyrrhetinic acid (GA) is one of the most important triterpenoic acids shows many pharmacological effects, especially antitumor activity. GA triggers apoptosis in various tumor cell lines. However, the antitumor activity of GA is weak, thus the synthesis of new synthetic analogs with enhanced potency is needed. By introducing various five-member fused heterocyclic rings at C-2 and C-3 positions, 18 novel GA derivatives were obtained. These compounds were evaluated for their inhibitory activity against the growth of eight different tumor cell lines using a SRB assay. The most active compound 37 showed IC50 between 5.19 and 11.72 µm, which was about 11-fold more potent than the lead compound GA. An apoptotic effect of GA and 37 was determined using flow cytometry and trypan blue exclusion assays. We also demonstrated here for the first time that GA and the synthetic derivatives exhibited inhibitory effect on migration of the tested tumor cells, especially 37 which was about 20-fold more potent than GA on antimetastatic activity.

A novel peptide from human apolipoprotein(a) inhibits angiogenesis and tumor growth by targeting c-Src phosphorylation in VEGF-induced human umbilical endothelial cells.

Many angiogenesis inhibitors are derived from large plasma proteins. Previous studies showed that the Kringle5-like domain (termed KV) in human apolipoprotein (a) is a potential antiangiogenic factor. However, its active region and the underling molecular mechanism remain elusive. Here, we identified an 11-amino acid peptide (named KV11) as the key region for the antiangiogenic function of the KV domain of apolipoprotein (a). We demonstrate that KV11 inhibits angiogenesis in vitro by suppressing human umbilical vein endothelial cell migration and microtubule formation. KV11 inhibits angiogenesis in chicken chorioallantoic membrane assays and mouse corneal micropocket angiogenesis assays in vivo. KV11 peptide shows no effect on tumor cell growth or proliferation, but significantly inhibits tumor growth in SCID mouse xenograft tumor model (p < 0.01) by preventing tumor angiogenesis. We elucidate that KV11 peptide suppresses angiogenesis and tumor progression by targeting the c-Src/ERK signaling pathways. Together, these studies provide the first evidence that KV11 from apolipoprotein KV domain has anti-angiogenesis functions and may be an anti-tumor drug candidate.

[A synthetic peptide selected by bioinformatics inhibits mouse corneal neovascularization].

OBJECTIVE: To identify the active anti-angiogenic region in the amino acid sequence of human apolipoprotein (a) [apo (a)] kringle V (KV), and to evaluate the role of this synthetic peptide on VEGF-induced angiogenesis of mouse cornea in vivo. METHODS: The characterization of the structure and biological activity of the amino acid sequence of apo (a) KV was analyzed using the bioinformatic methods which included sequence alignment, analysis of antigenicity, surface accessibility and hydrophilicity, and then a peptides was selected. The peptide was synthesized with a high efficiency solid-phase method. Corneal neovascularization was induced with a pellet containing 160 ng vascular endothelial growth factor (VEGF) in a mouse corneal micropocket model. 40 C57BL/6 mice (40 eyes) were divided randomly into 4 groups (10 eyes per group). Four kinds of pellets were made containing 160 ng VEGF plus the dose range of 0.0, 0.5, 1.0 and 1.5 microg synthetic peptide for control group, group A, group B and group C, respectively. Neovascularization was observed biomicroscopically on day 7 after the operation, and the corneas were then examined histologically. RESULTS: The result of bioinformatic analysis showed that the peptide contained a majority of conservative residues and possessed fine properties of antigenicity, surface accessibility and hydrophilicity. The synthetic peptide at the doses of 1.0 microg and 1.5 microg showed significant inhibition of mouse corneal neovascularization induced by VEGF in the parameters of vessel length, clock hours and area compared with the control group on day 7 after the operation (P < 0.01). There was no difference in the two doses (1.0 microg and 1.5 microg peptide) in the inhibition of the neovascularization. The dose of 0.5 microg peptide did not show any significant inhibition of the neovascularization compared with the control group (P > 0.05). CONCLUSIONS: The peptide, selected from the amino acid sequence of apo (a) KV by bioinformatics, appears to inhibit VEGF-induced angiogenesis in a mouse corneal micropocket assay in vivo, therefore, the study suggest that this amino acid sequence may locate at the active anti-angiogenic region of apo (a) KV.