Tanshinone I inhibits the growth and metastasis of osteosarcoma via suppressing JAK/STAT3 signalling pathway

Tanshinone I (Tan I) is a widely used diterpene compound derived from the traditional Chinese herb Danshen. Increasing evidence suggests that it exhibits anti‐cancer activity in various human cancers. However, the in vitro and in vivo effects of Tan I on osteosarcoma (OS) remain inadequately elucidated, especially those against tumour metastasis. Our results showed that Tan I significantly inhibited OS cancer cell proliferation, migration and invasion and induced cell apoptosis in vitro. Moreover, treatment with 10 and 20 mg/kg Tan I effectively suppressed tumour growth in subcutaneous xenografts and orthotopic xenograft mouse models. In addition, Tan I significantly inhibited tumour metastasis in intracardiac inoculation xenograft models. The results also showed that Tan I‐induced increased expression of the proapoptotic gene Bax and decreased expression of the anti‐apoptotic gene Bcl‐2 is the possible mechanism of its anti‐cancer effects. Tan I was also found to abolish the IL‐6‐mediated activation of the JAK/STAT3 signalling pathway. Conclusively, this study is the first to show that Tan I suppresses OS growth and metastasis in vitro and in vivo, suggesting it may be a potential novel and efficient drug candidate for the treatment of OS progression.     

Exercise-induced peptide EIP-22 protect myocardial from ischaemia/reperfusion injury via activating JAK2/STAT3 signalling pathway

Recent studies have revealed that exercise has myocardial protective effects, but the exact mechanism remains unclear. Studies have increasingly found that peptides play a protective role in myocardial ischaemia-reperfusion (I/R) injury. However, little is known about the role of exercise-induced peptides in myocardial I/R injury. To elucidate the effect of exercise-induced peptide EIP-22 in myocardial I/R injury, we first determined the effect of EIP-22 on hypoxia/reperfusion (H/R)- or H₂O₂-induced injury via assessing cell viability and lactate dehydrogenase (LDH) level. In addition, reactive oxygen species (ROS) accumulation and mitochondrial membrane potential (MMP) was assessed by fluorescence microscope. Meanwhile, Western blot and TUNEL methods were used to detect apoptosis level. Then, we conducted mice I/R injury model and verified the effect of EIP-22 by measuring cardiac function, evaluating heart pathology and detecting serum LDH, CK-MB and cTnI level. Finally, the main signalling pathway was analysed by RNA-seq. In vitro, EIP-22 treatment significantly improved cells viabilities and MMP and attenuated the LDH, ROS and apoptosis level. In vivo, EIP-22 distinctly improved cardiac function, ameliorated myocardial infarction area and fibrosis and decreased serum LDH, CK-MB and cTnI level. Mechanistically, JAK/STAT signalling pathway was focussed by RNA-seq and we confirmed that EIP-22 up-regulated the expression of p-JAK2 and p-STAT3. Moreover, AG490, a selective inhibitor of JAK2/STAT3, eliminated the protective roles of EIP-22. The results uncovered that exercise-induced peptide EIP-22 protected cardiomyocytes from myocardial I/R injury via activating JAK2/STAT3 signalling pathway and might be a new candidate molecule for the treatment of myocardial I/R injury.     

Periplocymarin alleviates pathological cardiac hypertrophy via inhibiting the JAK2/STAT3 signalling pathway

Pathological cardiac hypertrophy is the most important risk factor for developing chronic heart failure. Therefore, the discovery of novel agents for treating pathological cardiac hypertrophy remains urgent. In the present study, we examined the therapeutic effect and mechanism of periplocymarin (PM)‐mediated protection against pathological cardiac hypertrophy using angiotensinII (AngII)‐stimulated cardiac hypertrophy in H9c2 cells and transverse aortic constriction (TAC)‐induced cardiac hypertrophy in mice. In vitro, PM treatment significantly reduced the surface area of H9c2 cells and expressions of hypertrophy‐related proteins. Meanwhile, PM markedly down‐regulated AngII‐induced translocation of p‐STAT3 into the nuclei and enhanced the phosphorylation levels of JAK2 and STAT3 proteins. The STAT3 specific inhibitor S3I‐201 or siRNA‐mediated depleted expression could alleviate AngII‐induced cardiac hypertrophy in H9c2 cells following PM treatment; however, PM failed to reduce the expressions of hypertrophy‐related proteins and phosphorylated STAT3 in STAT3‐overexpressing cells, indicating that PM protected against AngII‐induced cardiac hypertrophy by modulating STAT3 signalling. In vivo, PM reversed TAC‐induced cardiac hypertrophy, as determined by down‐regulating ratios of heart weight to body weight (HW/BW), heart weight to tibial length (HW/TL) and expressions of hypertrophy‐related proteins accompanied by the inhibition of the JAK2/STAT3 pathway. These results revealed that PM could effectively protect the cardiac structure and function in experimental models of pathological cardiac hypertrophy by inhibiting the JAK2/STAT3 signalling pathway. PM is expected to be a potential lead compound of the novel agents for treating pathological cardiac hypertrophy.     

Inhibition of JAK2/STAT3 signalling induces colorectal cancer cell apoptosis via mitochondrial pathway

Abnormalities in the JAK2/STAT3 pathway are involved in the pathogenesis of colorectal cancer (CRC), including apoptosis. However, the exact mechanism by which dysregulated JAK2/STAT3 signalling contributes to the apoptosis has not been clarified. To investigate the role of both JAK2 and STAT3 in the mechanism underlying CRC apoptosis, we inhibited JAK2 with AG490 and depleted STAT3 with a small interfering RNA. Our data showed that inhibition of JAK2/STAT3 signalling induced CRC cellular apoptosis via modulating the Bcl-2 gene family, promoting the loss of mitochondrial transmembrane potential (Δψm) and the increase of reactive oxygen species. In addition, our results demonstrated that the translocation of cytochrome c (Cyt c), caspase activation and cleavage of poly (ADP-ribose) polymerase (PARP) were present in apoptotic CRC cells after down-regulation of JAK2/STAT3 signalling. Moreover, inhibition of JAK2/STAT3 signalling suppressed CRC xenograft tumour growth. We found that JAK2/STAT3 target genes were decreased; meanwhile caspase cascade was activated in xenograft tumours. Our findings illustrated the biological significance of JAK2/STAT3 signalling in CRC apoptosis, and provided novel evidence that inhibition of JAK2/STAT3 induced apoptosis via the mitochondrial apoptotic pathway. Therefore, JAK2/STAT3 signalling may be a potential target for therapy of CRC.     

Tannic acid inhibits EGFR/STAT1/3 and enhances p38/STAT1 signalling axis in breast cancer cells

Tannic acid (TA), a naturally occurring polyphenol, is a potent anti‐oxidant with anti‐proliferative effects on multiple cancers. However, its ability to modulate gene‐specific expression of tumour suppressor genes and oncogenes has not been assessed. This work investigates the mechanism of TA to regulate canonical and non‐canonical STAT pathways to impose the gene‐specific induction of G1‐arrest and apoptosis. Regardless of the p53 status and membrane receptors, TA induced G1‐arrest and apoptosis in breast cancer cells. Tannic acid distinctly modulated both canonical and non‐canonical STAT pathways, each with a specific role in TA‐induced anti‐cancer effects. Tannic acid enhanced STAT1 ser727 phosphorylation via upstream serine kinase p38. This STAT1 ser727 phosphorylation enhanced the DNA‐binding activity of STAT1 and in turn enhanced expression of p21^Waf1/Cip1. However, TA binds to EGF‐R and inhibits the tyrosine phosphorylation of both STAT1 and STAT3. This inhibition leads to the inhibition of STAT3/BCL‐2 DNA‐binding activity. As a result, the expression and mitochondrial localization of BCl‐2 are declined. This altered expression and localization of mitochondrial anti‐pore factors resulted in the release of cytochrome c and the activation of intrinsic apoptosis cascade involving caspases. Taken together, our results suggest that TA modulates EGF‐R/Jak2/STAT1/3 and P38/STAT1/p21^Waf1/Cip1 pathways and induce G1‐arrest and intrinsic apoptosis in breast carcinomas.     

IGF2BP3 facilitates cell proliferation and tumorigenesis via modulation of JAK/STAT signalling pathway in human bladder cancer

Insulin‐like growth factor‐2 messenger RNA‐binding protein 3 (IGF2BP3) has been reported to contribute to tumorigenesis in several human cancers. However, the biological functions of IGF2BP3 in bladder cancer are poorly understood. We investigated the relation between IGF2BP3 expression and prognosis of bladder cancer patients. Cell proliferation, cell cycle and cell apoptosis assays were performed to assess IGF2BP3 functions. The results showed that IGF2BP3 was overexpressed in bladder cancer tissues compared with that in normal bladder tissues, and its higher expression was closely correlated with poor prognosis in bladder cancer patients. Overexpression of IGF2BP3 markedly promoted cell proliferation and cell cycle progression and inhibited cell apoptosis, while knockdown of IGF2BP3 notably suppressed the proliferation, promoted cell apoptosis and induced cell cycle arrest at the G0/G1 phase. Mechanistically, we revealed that IGF2BP3 promotes the activation of the JAK/STAT pathway in bladder cancer cells. Moreover, the JAK/STAT inhibitor dramatically blocked the tumour‐promoting activity of IGF2BP3. Tumour growth in vivo was also suppressed by knocking down of IGF2BP3. Hence, IGF2BP3 facilitated bladder cancer cell proliferation by activating the JAK/STAT signalling pathway. These findings suggest that IGF2BP3 exhibits an oncogenic effect in human bladder cancer progression.     

Scutellarin inhibits proliferation and invasion of hepatocellular carcinoma cells via down‐regulation of JAK2/STAT3 pathway

The prognosis of hepatocellular carcinoma (HCC) is poor because of high incidence of recurrence and metastasis. JAK/STAT signalling pathway regulates cell proliferation, apoptosis, differentiation and migration and epithelial‐mesenchymal transition (EMT) is also considered to contribute to invasion and metastasis of epithelial malignant tumours. Scutellarin is an active component found in many traditional Chinese herbs and has been regularly used in anti‐inflammatory and antitumour medicine. This study aimed to identify the effect of scutellarin and its possible mechanism of action in HCC cells. Proliferation, colony‐forming, apoptosis and cell migration assays were used to examine the effect of scutellarin on HCC cells. Quantitative real‐time PCR and Western blotting were performed to study the molecular mechanisms of action of scutellarin. Light and electron microscopy and immunofluorescence analysis were performed to study the effect of scutellarin on cellular mechanics. We show that scutellarin potentially suppresses invasiveness of HepG2 and MHCC97‐H cells in vitro by remodelling their cytoskeleton. The molecular mechanism behind it might be the inhibition of the EMT process, which could be attributed to the down‐regulation of the JAK2/STAT3 pathway. These findings may provide new clinical ideas for the treatment of liver cancer.     

TWEAK/Fn14 mediates atrial‐derived HL‐1 myocytes hypertrophy via JAK2/STAT3 signalling pathway

Atrial myocyte hypertrophy is one of the most important substrates in the development of atrial fibrillation (AF). The TWEAK/Fn14 axis is a positive regulator of cardiac hypertrophy in cardiomyopathy. This study therefore investigated the effects of Fn14 on atrial hypertrophy and underlying cellular mechanisms using HL‐1 atrial myocytes. In patients with AF, Fn14 protein levels were higher in atrial myocytes from atrial appendages, and expression of TWEAK was increased in peripheral blood mononuclear cells, while TWEAK serum levels were decreased. In vitro, Fn14 expression was up‐regulated in response to TWEAK treatment in HL‐1 atrial myocytes. TWEAK increased the expression of ANP and Troponin T, and Fn14 knockdown counteracted the effect. Inhibition of JAK2, STAT3 by specific siRNA attenuated TWEAK‐induced HL‐1 atrial myocytes hypertrophy. In conclusion, TWEAK/Fn14 axis mediates HL‐1 atrial myocytes hypertrophy partly through activation of the JAK2/STAT3 pathway.