Signal transducer and activator of transcription 3 (STAT3) take part in cell proliferation, differentiation, survival, apoptosis, transformation, cellular immunity and some other important physiological and pathological processes. Among STAT3 signaling pathways, the JAK-STAT signaling pathway has been comprehensively studied. Abnormal activation of STAT3 is frequently detected in various tumors, and the abnormal activation is closely related with the tumorigenesis. Recent studies have found that mutations and several specific genotypes of single nucleotide polymorphisms in STAT3 gene may be involved in tumor formation, also suggesting the important role of STAT3 in tumor biology. In this review, the role of STAT3 in the development of tumors is briefly summarized.
Humans ; Neoplasms ; metabolism ; pathology ; STAT3 Transcription Factor ; Signal Transduction

In order to investigate the mechanism of stat3 nuclear import. positioned a characterized NLS of the SV40 large T antigen into Stat3-GFP, Dstat3-GFP respectively between the C-terminus of Stat3 and the N-terminus of GFP to create Stat3-NLS-GFP and Dstat3-NLS-GFP. With NLS-GFP as the positive control, Expression of the Stat3-NLS-GFP without IL-6 stimulation and Stat3-GFP with IL-6 stimulation resulted in a predominantly nuclear localization in 293T cell. Expression of Stat3-GFP and Dstat3-NLS-GFP without IL-6 stimulation resulted in predominantly cytoplasm localization in 293T cell. The results suggest that latent Stat3 is not anchored in the cytoplasm, and that nuclear localization in response to IL-6 is facilitated by gain of an NLS function.
Active Transport, Cell Nucleus ; Cell Nucleus ; metabolism ; Nuclear Localization Signals ; Plasmids ; metabolism ; STAT3 Transcription Factor ; metabolism

OBJECTIVETo investigate the role of Janus kinase-signal transducer and transcription activator (JAK-STAT) pathway in the regulation of synthesis and release of lipopolysaccharide-induced high mobility group box-1 protein (HMGB1).

METHODSPeritoneal macrophages harvested from male Wistar rats were incubated for 3 days before the experiment. The activation of Janus kinase-2 (JAK2), signal transducer and activator of transcription-1 (STAT1) and STAT3 was observed before and 10, 30, 60 and 120 mins after LPS stimulation (4 determinations at each time point) and it was expressed as A value (absorption). In addition, the cells were divided into normal control, LPS stimulation, JAK2 inhibition (with AG490 treatment 2 hours before LPS stimulation), STAT1 inhibition (with fludarabine treatment 2 hours before LPS stimulation) and STAT3 inhibition (with rapamycin treatment 2 hours before LPS stimulation) groups. The cells in all groups except control group were stimulated with LPS 3 days after culture. The expression of HMGB1 gene and its protein release in each group were determined for 4 times and were expressed as A value.

RESULTSLPS could activate JAK2, STAT1 and STAT3 within 2 hours, especially the activation of STAT3 appeared more quickly, peaking at 10 minutes after LPS stimulation (7.47 +/- 0.56). Pretreatment with the inhibitors of JAK-STAT pathway could markedly reduce the expression of HMGB1 mRNA (P < 0.01), but exerted no effect on HMGB1 release.

CONCLUSIONJAK-STAT pathway can be activated early during endotoxin challenge, and it may play a role in the regulation of HMGB1 synthesis.

Animals ; Cell Culture Techniques ; HMGB1 Protein ; biosynthesis ; Janus Kinase 2 ; metabolism ; Lipopolysaccharides ; Macrophages, Peritoneal ; metabolism ; Male ; Rats ; Rats, Wistar ; STAT1 Transcription Factor ; metabolism ; STAT3 Transcription Factor ; metabolism

Large granular lymphocytic leukemia (LGLL) is a rare lymphoproliferative disorder of clonal expansion of cytotoxic T- or NK-cells in blood and bone marrow, and often associated with autoimmune disorders. According to the current WHO classification of the hematopoietic and lymphoid tissue tumors, the clonal LGL expansions are further classified as T-cell large granular lymphocytic leukemia (T-LGLL), chronic lymphoproliferative disorders of NK cells (CLPD-NK) and aggressive NK cell leukemia. Since there is a general lack of awareness of this disease, some patients may be misdiagnosed or some cases may be missed when diagnosis was done. At present, the pathogenesis of LGLL remains incomplete and unclear, and the therapeutic effects are unsatisfactory. For this reason, it is necessary to find prognostic marks and therapeutic targets of this disease. The constitutive activation of JAK/STAT pathway has been claimed to be involved in the development of LGLL. Recently, the somatic mutations in the SH2 domain of STAT3 in LGLL are frequently observed, which lead to the activation of JAK/STAT pathway. STAT3 is the first molecular markers that are highly specific for LGLL, and STAT3 mutations have been rarely detected in other tumor types studied, thus the STAT3 mutations can be used as molecular markers for LGLL diagnosis and can provide a novel therapeutic target for patients with LGLL.
Humans ; Janus Kinases ; genetics ; metabolism ; Leukemia, Large Granular Lymphocytic ; genetics ; metabolism ; Mutation ; STAT3 Transcription Factor ; genetics ; metabolism ; Signal Transduction

OBJECTIVE: To show that Stat3 played a key role in the G1 to S phase transition in laryngocarcinoma cells. METHOD: Human laryngocarcinoma cell lines Hep-2 were transfected with Stat3 antisense oligonucleotide mediated by liposome, MTT assay was used to measure the proliferation, flow cytometry was applied to analyze the cell cycle, and the expressions of Stat3, phosphorylation specific Stat3 (tyrosine705), CyclinD1, Cyclin E, CDK2, CDK4, CDK6, p21 and p27 were detected by western blot. RESULT: Hep-2 laryngocarcinoma cell lines expressed constitutively activated Stat3. Antisense oligonucleotide which directed blocked up the translation site resulted in growth inhibition, downregulation of Stat3, p-Stat3, Cyclins and CDKs, and upregulation of p21 and p27. CONCLUSION Our findings suggested that Stat3 played an important role in the G1 to S phase transition in laryngocarcinoma cells, Stat3 orchestrated cell cycle by regulating the balance between CDK/Cyclin complex and CKI.
Cell Line, Tumor ; G1 Phase ; Humans ; Laryngeal Neoplasms ; metabolism ; pathology ; S Phase ; STAT3 Transcription Factor ; genetics ; metabolism ; Signal Transduction ; Transfection

Proteasome is the eukaryotic organelle responsible for degradation of short-lived proteins and involved in maintaining cellular protein homeostasis. It has been reported that during the occurrence and development of hepatocellular carcinoma (HCC), the regulatory particle subunits of proteasome regulate a series of tumor-related proteins, and proliferation, survival-associated signaling molecules, including PTEN gene, P53, Bcl-2, Bcl-2 interacting mediator of cell death (Bim), cyclin-dependent kinase 4(CDK4), transforming growth factor β receptor (TGFBR), E2F1, growth factor receptor-bound protein 2 (GRB2) . Meanwhile, these subunits regulate some tumor-associated pathway protein, such as signal transducer and activator of transcription 3 (STAT3) and protein kinase B (AKT), inducing their malfunction to promote the occurrence, proliferation, invasion and metastasis of HCC. The core particle subunits are more to perform the degradation of HCC-related proteins, so inhibitors targeting the core particle show a good anti-tumor effect. This review summarizes the current research progress on the regulation and mechanism of proteasome subunits in promoting the occurrence and development .
Carcinoma, Hepatocellular ; Cell Line, Tumor ; Cell Proliferation ; Humans ; Liver Neoplasms ; Proteasome Endopeptidase Complex/metabolism* ; STAT3 Transcription Factor/metabolism* ; Signal Transduction

Cancer stands as one of the predominant causes of mortality globally, necessitating ongoing efforts to develop innovative therapeutics. Historically, natural products have been foundational in the quest for anticancer agents. Bulbocodin D (BD) and Bulbocodin C (BC), two bibenzyls derived from Pleione bulbocodioides (Franch.) Rolfe, have demonstrated notable in vitro anticancer activity. In human lung cancer A549 cells, the IC_50s for BD and BC were 11.63 and 11.71 μmol·L^-1, respectively. BD triggered apoptosis, as evidenced by an upsurge in Annexin V-positive cells and elevated protein expression of cleaved-PARP in cancer cells. Furthermore, BD and BC markedly inhibited the migratory and invasive potentials of A549 cells. The altered genes identified through RNA-sequencing analysis were integrated into the CMap dataset, suggesting BD's role as a potential signal transducer and activator of transcription 3 (STAT3) inhibitor. SwissDock and MOE analyses further revealed that both BD and BC exhibited a commendable binding affinity with STAT3. Additionally, a surface plasmon resonance assay confirmed the direct binding affinity between these compounds and STAT3. Notably, treatment with either BD or BC led to a significant reduction in p-STAT3 (Tyr 705) protein levels, regardless of interleukin-6 stimulation in A549 cells. In addition, the extracellular signal-regulated kinase (ERK) was activated after BD or BC treatment. An enhancement in cancer cell mortality was observed upon combined treatment of BD and U0126, the MEK1/2 inhibitor. In conclusion, BD and BC emerge as promising novel STAT3 inhibitors with potential implications in cancer therapy.
Humans ; Lung Neoplasms/metabolism* ; STAT3 Transcription Factor/metabolism* ; Antineoplastic Agents/chemistry* ; A549 Cells ; Apoptosis ; Cell Line, Tumor ; Cell Proliferation

Cancer stem cells (CSCs) are considered responsible for the high recurrence rate in cervical carcinoma. It has been demonstrated that the signal transducer and activator of transcription 3 (STAT3) is involved in the oncogenesis and takes part in mediating the effects of maintaining stem cell phenotype and pluripotency by regulating the expression of stem cell-related transcription factors. However, the correlation between STAT3 and stem cell-related transcription factors in cervical cancer has not been elucidated. In this study, we established overexpressing plasmid (GV316-STAT3) and siRNA-STAT3 for transfecting Siha cells. Cells negative or positive for Nanog, Oct4, or Sox2 were selected by flow cytometry. Proliferation and differentiation rate of Siha cells was determined by detecting the efficiency of tumor sphere formation. The expression of Nanog, Oct4 and Sox2 (cancer stem cell markers) and STAT3 was detected by quantitative real-time PCR and immunoblotting for Siha cells and by immunohistochemistry (IHC) for cervical tissues, respectively. The results showed that Nanog+, Oct4+, and Sox2+ Siha-STAT3 over-expressing cells displayed the typical non-adherent spheres. The sphere formation efficiency was significantly different between Siha-STAT3 overexpressing cells and siRNA-STAT3 cells (P<0.05). Meanwhile, the expression levels of Oct4, Nanog and Sox2 mRNA and protein were significantly higher in Siha-STAT3 overexprssing cells than in siRNA-STAT3 cells (P<0.05). In addition, the positive rate of STAT3, Nanog, Oct4 and Sox2 in cervical cancer tissues was higher than that in chronic cervicitis group (P<0.05). There was a significantly positive relationship between STAT3 and Nanog or Oct4 or Sox2 expression (all P<0.001). These results suggested that Oct4+, Sox2+, and Nanog+ cell population possesses stem cell properties in cervical cancer, which may contribute to cervical carcinogenesis and be regulated by STAT3.
Cell Line, Tumor ; Female ; Humans ; Neoplastic Stem Cells ; metabolism ; pathology ; STAT3 Transcription Factor ; metabolism ; Transcription Factors ; metabolism ; Uterine Cervical Neoplasms ; metabolism ; pathology

OBJECTIVETo investigate the effects of activated AKT on murine myeloid precursor cells (32D cells), and the effects of IFN-γ on 32D cells and its mechanisms.

METHODSPlasmid transduction was used to enhance the expression of AKT on 32D cells. After the transfected cells treated with IFN-γ for 24 hours, proliferation rate was tested by WST-1, apoptosis by flow cytometry, expression of phosphorylated Erk1/2, Stat3 and phosphorylated Stat3 was determined by Western blot.

RESULTS(1) IFN-γ at low concentration (100 U/ml) enhanced the growth and proliferation of 32D cells, while at high concentration (1000 U/ml) suppressed them. (2) Compared with control groups, low concentration IFN-γ increased (1124 ± 13) Stat3 phosphorylation in 32D-cell, while it high concentration IFN-γ decreased (601 ± 13). 32D cells transfected with activated Akt grew rapidly (0.287 ± 0.010) and had a low apoptotic rate [(9.57 ± 0.17)% (P < 0.05)]. (3) The expression of p-Erk1/2 in transfected 32D-cell was significantly reduced (P < 0.05). (4) Apoptosis rate of IFN-γ treated group was significantly decreased in transfected 32D cells (P < 0.05).

CONCLUSIONSIFN-γ has dual effects on 32D cells, namely, at low concentration enhanced the growth and proliferation of 32D cells, while at high concentration suppressed them. Its mechanisims is possibly through Stat3 pathway. Activated Akt can significantly promote the growth and proliferation of 32D cell and significantly inhibit apoptosis and IFN-γ can regulate cell proliferation and apoptosis through AKT. AKT activation can inhibit the Erk signal pathway, which may be affected by inhibition the modificaton of Raf1.

Animals ; Apoptosis ; drug effects ; Cell Proliferation ; drug effects ; Phosphorylation ; drug effects ; STAT3 Transcription Factor ; metabolism ; Signal Transduction ; drug effects

Periodontitis patients are at risk of alveolar bone loss during orthodontic treatment. The aim of this study was to investigate whether intermittent parathyroid hormone (1-34) treatment (iPTH) could reduce alveolar bone loss during orthodontic tooth movement (OTM) in individuals with periodontitis and the underlying mechanism. A rat model of OTM in the context of periodontitis was established and alveolar bone loss was observed. The control, iPTH and iPTH + stattic groups received injections of vehicle, PTH and vehicle, or PTH and the signal transducer and activator of transcription 3 (STAT3) inhibitor stattic, respectively. iPTH prevented alveolar bone loss by enhancing osteogenesis and suppressing bone resorption in the alveolar bone during OTM in rats with periodontitis. This effect of iPTH was along with STAT3 activation and reduced by a local injection of stattic. iPTH promoted osteoblastic differentiation and might further regulate the Wnt/β-catenin pathway in a STAT3-dependent manner. The findings of this study suggest that iPTH might reduce alveolar bone loss during OTM in rats with periodontitis through STAT3/β-catenin crosstalk.
Animals ; Homeostasis ; Humans ; Osteogenesis ; Parathyroid Hormone ; Periodontitis/drug therapy* ; Rats ; STAT3 Transcription Factor/metabolism* ; Tooth Movement Techniques ; beta Catenin