Modulation of Akt vs Stat3 activity by the focal adhesion kinase in non-neoplastic mouse fibroblasts

Targeting STAT3 Enzyme for Cancer Treatment

A category of cytoplasmic transcription factors called STATs mediates intracellular signaling, which is frequently generated at receptors on cell surfaces and subsequently sent to the nucleus. STAT3 is a member of a responsible for a variety of human tumor forms, including lymphomas, hematological malignancies, leukemias, multiple myeloma and several solid tumor types. Numerous investigations have demonstrated constitutive STAT3 activation lead to cancer development such as breast, head and neck, lung, colorectal, ovarian, gastric, hepatocellular, and prostate cancers. It's possible to get a hold of the book here. Tumor cells undergo apoptosis when STAT3 activation is suppressed. This review highlights the STAT3 activation and inhibition which can be used for further studies.

The Protective Effect of miRNA-146a Liposome Nanoparticles on Vascular Smooth Muscle Cells After Coronary Intervention

The abnormal expression of miRNA-146a is related to the progression of coronary arteries. This study intends to explore the protective effect of miRNA-146a on vascular smooth muscle cells (VSMCs) after coronary intervention and the related mechanism. 10 miniature pigs were randomly assigned into control group, model group, blank group, miRNA-146a group, cilostazol group, and STAT3 signaling agonist group followed by analysis of the morphology and viability of VSMCs, expression of miRNA-146a, STAT3, NF-kB, TNF-a, IL-6, and AT-1R as well as the relationship between miR-146a and STAT3. The BNP (192.39±12.32) pg/ml and cTnI (14.20±2.12) μg/L of model group were significantly higher than those of control group (P < 0.05). miRNA-146a level was highest in miRNA-146a group and cilostazol group, while lower in other two groups with the lowest level in agonist group (P <0.05). The cell viability and AngII level of miRNA-146a group and cilostazol group were lower, and higher in the other two groups with highest level in pathway agonist group (P < 0.05). miRNA-146a group and cilostazol group showed lower expressions of STAT3, NF-kB, TNF-a, IL-6, AT-1R than the other two groups. The pathway agonist group showed significantly higher level than blank group (P <0.05). liposome nanoparticles carrying miRNA-146a inhibited the activity of STAT3 signaling, down-regulated the levels of downstream factors including TNF-a, IL-6, and TNF-a and subsequently decreased AngII and AT-1R levels, therefore playing a protective effect on VSMCs after coronary intervention.

Activated Src requires Cadherin-11, Rac, and gp130 for Stat3 activation and survival of mouse Balb/c3T3 fibroblasts

We previously demonstrated that engagement of cadherins, cell to cell adhesion molecules, triggers a dramatic increase in levels and activity of the Rac/Cdc42 small GTPases, which is followed by secretion of IL6 family cytokines and activation of their common receptor, gp130, in an autocrine manner. This results in phosphorylation of the Signal Transducer and Activator of Transcription-3 (Stat3) on tyrosine-705, which then dimerizes, migrates to the nucleus, and activates transcription of genes involved in cell division and survival. In the present report we demonstrate that, in mouse Balb/c3T3 fibroblasts, mutationally activated Src527F also increases Rac levels, leading to secretion of IL6 family cytokines and gp130 activation, which triggers the Stat3-ptyr705 increase. Interestingly, our results also demonstrate that cadherin-11 is required to preserve gp130 levels for IL6 family signaling. At the same time, however, activated Src527F downregulates cadherin-11, in a quantitative manner. As a result, Src527F expression to intermediate levels allows sufficient cadherin-11, hence gp130 levels for Stat3 activation, as expected. However, expressed to high levels, Src527F eliminates cadherin-11, hence gp130 signaling, thus abolishing Stat3-ptyr705 stimulation. Taken together, these data establish for the first time a loop between Src, cadherin-11, gp130, and Stat3 activation. This fine balance between Src527F and cadherin-11 levels which is required for Stat3 activation and cellular survival could have significant therapeutic implications.

Roads to Stat3 Paved with Cadherins

The engagement of cadherins, cell-to-cell adhesion proteins, triggers a dramatic increase in the levels and activity of the Rac/Cdc42 GTPases, through the inhibition of proteasomal degradation. This leads to an increase in transcription and secretion of IL6 family cytokines, activation of their common receptor, gp130, in an autocrine manner and phosphorylation of the signal transducer and activator of transcription-3 (Stat3) on tyrosine-705 by the Jak kinases. Stat3 subsequently dimerizes, migrates to the nucleus and activates the transcription of genes involved in cell division and survival. The Src oncogene also increases Rac levels, leading to secretion of IL6 family cytokines and gp130 activation, which triggers a Stat3-ptyr705 increase. Interestingly, at the same time, Src downregulates cadherins in a quantitative manner, while cadherins are required to preserve gp130 levels for IL6 family signalling. Therefore, a fine balance between Src527F/Rac/IL6 and Src527F/cadherin/gp130 levels is in existence, which is required for Stat3 activation. This further demonstrates the important role of cadherins in the activation of Stat3, through preservation of gp130 function. Conversely, the absence of cadherin engagement correlates with low Stat3 activity: In sparsely growing cells, both gp130 and Stat3-ptyr705 levels are very low, despite the fact that cSrc is active in the FAK (focal adhesion kinase)/cSrc complex, which further indicates that the engagement of cadherins is important for Stat3 activation, not just their presence. Furthermore, the caveolin-1 protein downregulates Stat3 through binding and sequestration of cadherins to the scaffolding domain of caveolin-1. We hypothesize that the cadherins/Rac/gp130 axis may be a conserved pathway to Stat3 activation in a number of systems. This fact could have significant implications in Stat3 biology, as well as in drug testing and development.