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Background/aim Colorectal cancer is one of the most common malignancies worldwide. Small molecule-based chemotherapy is an attractive approach for the chemoprevention and treatment of colorectal cancer. Methylsulfonylmethane (MSM) is a natural organosulfur compound with anticancer properties, as revealed by studies on in vitro models of gingival, prostate, lung, hepatic, and breast cancer. However, the molecular mechanisms underlying the effects of MSM in colon cancer cells remain unclear. Materials and methods Here, we investigated the effects of MSM, especially on the cell cycle arrest and apoptosis, in HT-29 cells. Results MSM suppressed the viability of HT-29 cells by inducing apoptosis and cell cycle arrest at the G0/G1 phase. MSM suppressed the sphere-forming ability and expression of stemness markers in HT-29 cells. Conclusion MSM has anti-cancer effects on HT-29 cells, and induces cell cycle arrest and apoptosis, while suppressing the stemness potential.

Background/aim Non-small cell lung cancer (NSCLC) is one among the most common cancers worldwide. Recently, dietary phytochemicals have been reported as an attractive approach to improve the symptoms of NSCLC patients. Tannic acid is a natural polyphenol, which is known to have anticancer effects on in vitro models of breast, gingival and colon cancer. However, the molecular mechanisms associated with the actions of tannic acid on A549 human lung cancer cells have not been elucidated. Materials and methods In this study, we analyzed the effect of tannic acid on A549 cells and their underlying mechanisms using western blotting, flow cytometry, invasion assay and tumorsphere formation assay. Results Tannic acid treatment suppressed the viability of A549 cells through cell cycle arrest and induction of the intrinsic pathways of apoptosis. In addition, the various malignant phenotypes of A549 cells including invasion, migration, and stemness were inhibited by tannic acid treatment. Conclusion Tannic acid could be used as an effective inhibitor of lung cancer progression.

Janus kinase 2 (JAK2) and STAT3 signaling is considered a major pathway in lipopolysaccharide (LPS)-induced inflammation. Toll-like receptor 4 (TLR-4) is an inflammatory response receptor that activates JAK2 during inflammation. STAT3 is a transcription factor for the pro-inflammatory cytokine IL-6 in inflammation. Sulfur is an essential element in the amino acids and is required for growth and development. Non-toxic sulfur (NTS) can be used in livestock feeds as it lacks toxicity. The present study aimed to inhibit LPS-induced inflammation in C2C12 myoblasts using NTS by regulating TLR-4 and JAK2/STAT3 signaling via the modulation of IL-6. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was conducted to analyze cell viability and reverse transcription polymerase chain reaction and western blotting performed to measure mRNA and protein expression levels. Chromatin immunoprecipitation and enzyme-linked immunosorbent assays were used to determine the binding activity of proteins. The results indicated that NTS demonstrated a protective effect against LPS-induced cell death and inhibited LPS-induced expression of TLR-4, JAK2, STAT3 and IL-6. In addition, NTS inhibited the expression of nuclear phosphorylated-STAT3 and its binding to the IL-6 promoter. Therefore, NTS may be a potential candidate drug for the treatment of inflammation.

Non-small-cell lung cancer (NSCLC) is the most common lung cancer subtype and accounts for more than 80% of all lung cancer cases. Epidermal growth factor receptor (EGFR) phosphorylation by binding growth factors such as EGF activates downstream prooncogenic signaling pathways including KRAS-ERK, JAK-STAT, and PI3K-AKT. These pathways promote the tumor progression of NSCLC by inducing uncontrolled cell cycle, proliferation, migration, and programmed death-ligand 1 (PD-L1) expression. New cytotoxic drugs have facilitated considerable progress in NSCLC treatment, but side effects are still a significant cause of mortality. Gallic acid (3,4,5-trihydroxybenzoic acid, GA) is a phenolic natural compound, isolated from plant derivatives, that has been reported to show anticancer effects. We demonstrated the tumor-suppressive effect of GA, which induced the decrease of PD-L1 expression through binding to EGFR in NSCLC. This binding inhibited the phosphorylation of EGFR, subsequently inducing the inhibition of PI3K and AKT phosphorylation, which triggered the activation of p53. The p53-dependent upregulation of miR-34a induced PD-L1 downregulation. Further, we revealed the combination effect of GA and anti-PD-1 monoclonal antibody in an NSCLC-cell and peripheral blood mononuclear&ndash, cell coculture system. We propose a novel therapeutic application of GA for immunotherapy and chemotherapy in NSCLC.

Cortisol is a hormone involved in stress during exercise. The application of natural compounds is a new potential approach for controlling cortisol-induced stress. Tumour suppressor protein p53 is activated during cellular stress. Succinate dehydrogenase complex subunit A (SDHA) and hypoxanthine phosphoribosyl transferase 1 (HPRT1) are considered to be two of the most stable reference genes when measuring stress during exercise in horses. In the present study cells were considered to be in a ‘stressed state’ if the levels of these stable genes and the highly stress responsive gene p53 were altered. It was hypothesized that a natural organic sulphur-containing compound, methylsulfonylmethane (MSM), could inhibit cortisol-induced stress in racing horse skeletal muscle cells by regulating SDHA, HPRT1 and p53 expression. After assessing cell viability using MTT assays, 20 µg/ml cortisol and 50 mM MSM were applied to horse skeletal muscle cell cultures. Reverse transcription-quantitative PCR and western blot analysis demonstrated increases in SDHA, HPRT1 and p53 expression in cells in response to cortisol treatment, which was inhibited or normalized by MSM treatment. To determine the relationship between p53 and SDHA/HPRT1 expression at a transcriptional level, horse gene sequences of SDHA and HPRT1 were probed to identify novel binding sites for p53 in the gene promoters, which were confirmed using a chromatin immunoprecipitation assay. The relationship between p53 and SDHA/HPRT1 expression was confirmed using western blot analysis following the application of pifithrin-α, a p53 inhibitor. These results suggested that MSM is a potential candidate drug for the inhibition of cortisol-induced stress in racehorse skeletal muscle cells.

As human lifespans have increased, the incidence of osteoporosis has also increased. Methylsulfonylmethane (MSM) affects the process of mesenchymal stem cell (MSC) differentiation into osteoblasts via the Janus kinase 2 (Jak2)/signal transducer and activator of transcription (STAT)5b signaling pathway, and bone morphogenetic protein 2 (BMP‑2) is also known to significantly affect bone health. In addition, the phosphorylation of small mothers against decapentaplegic (Smad)1/5/8 regulates the Runt‑related transcription factor 2 (Runx2) gene, which encodes a transcription factor for osteoblast differentiation markers. In the present study, the differentiation of MSCs treated with MSM, BMP‑2, and their combination were examined. The differentiation of osteoblasts was demonstrated through observation of morphological changes and mineralization, using alizarin red and Von Kossa staining. Western blotting analysis demonstrated that the combination of MSM and BMP-2 increased the phosphorylation of the BMP signaling-associated protein, Smad1/5/8. Combination of MSM and BMP-2 significantly increased osteogenic differentiation and mineralization of the MSCs compared with either MSM or BMP-2 alone. Additionally, reverse transcription-polymerase chain reaction analysis demonstrated that combination of MSM and BMP-2 increased the expression level of the Runx2 gene and the osteoblast differentiation marker genes, alkaline phosphatase, bone sialoprotein and osteocalcin, in MSCs compared with controls. Thus, the combination of MSM and BMP-2 may promote the differentiation of MSCs into osteoblasts.

We investigated the effect and molecular mechanism of 24-MCF-induced PPAR-γ2 on angiogenesis-related genes in MCF7 cells. cDNA microarray, semi-quantitative reverse transcription (RT)-PCR, and western blotting revealed that 24-MCF mediated the expression of genes related to angiogenesis in MCF-7 cells. Luciferase reporter assay demonstrated that promoter activation of the LIF gene, an anti-angiogenesis factor, was increased upon PPAR-γ2 overexpression and 24-MCF treatment, whereas activation of HoxA7 and VEGF promoters, known pro-angiogenesis factors, decreased upon PPAR-γ2 overexpression and 24-MCF treatment. We identified PPAR-response elements (PPRE) located in the VEGF (-913 to +1), HoxA7 (-1107 to +1), and LIF promoter regions (-9032 to -8403). VEGF promoter activity was abolished by mutation of the PPRE motif. Treatment with 24-MCF inhibited expression of VEGF and inhibited the Akt/mTOR pathway. Treatment with 24-MCF also decreased VEGF secretion in MCF7 cells and PMA-stimulated tube formation in HUVECs. Our findings suggest that 24-MCF induces PPAR-γ2-mediated regulation of anti-angiogenesis via PPRE motifs in VEGF, HoxA7, and LIF promoters or upstream regions. Furthermore, 24-MCF treatment inhibits angiogenesis by blocking VEGF secretion.

The major hallmarks of tumor progression are angiogenesis, migration and metastasis. Among the components of Rhodiola rosea, salidroside (p‑hydroxyphenethyl-β‑d-glucoside) is one of the most potent, and is present in all Rhodiola species. Recent data have revealed the anticancer effects of salidroside; however, the mechanism underlying its ability to inhibit tumor angiogenesis remains unknown. The present study aimed to analyze how salidroside affects major factors involved in breast cancer, and to elucidate its ability to inhibit angiogenesis and invasion. Signal transducer and activator of transcription 3 (STAT3) is a marker for tumor angiogenesis and migration, which interacts with matrix metalloproteinases (MMPs). Specifically, MMPs act as a downstream target for STAT3. Using western blotting and reverse transcription-quantitative polymerase chain reaction analysis, the present study demonstrated that treatment of MDA‑MB 231 triple-negative breast cancer (TNBC) cells with salidroside led to inhibition of invasion and migration markers, and of STAT3 signaling. Furthermore, in vitro angiogenesis analyses in human umbilical vein endothelial cells confirmed the anti-angiogenic activity of salidroside. An electrophoretic mobility shift assay also demonstrated that salidroside may inhibit the DNA-binding activity of STAT3, preventing STAT3 from binding to a novel binding site of the MMP2 gene promoter. In conclusion, the present results demonstrated that salidroside may downregulate the STAT3 signaling pathway, and inhibit cell viability, migration and invasion through MMPs in breast cancer cells.

Breast cancer is the most common cancer in women globally. The factors that increase risk include: late age at first birth, alcohol, radiation exposure, family history of breast cancer, and postmenopausal hormone therapy. Numerous drugs are being developed to treat breast cancer. Among them, Herceptin is used for the treatment of human epidermal growth factor receptor 2 (HER2)-positive cases and targets HER2 effectively and efficiently, but it is very expensive. Methylsulfonylmethane (MSM) is an organic sulfur-containing natural compound having no reported toxicity. We examined MSM in breast cancer cell lines and found it inhibited the proliferation of estrogen receptor-positive and HER2-positive breast cancer cells in a dose-dependent manner. It also suppressed the activation of STAT5b and expression of HER2 in breast cancer cells. We determined the STAT5b binding site (GAS element) in the HER2 gene. Detailed analysis showed that MSM decreased the ability of STAT5b to bind the promoter of the HER2 gene and a luciferase assay demonstrated reduced activity. We confirmed that MSM can effectively regulate STAT5b, and thereby decrease HER2 expression. Therefore, we recommend the use of MSM as an inhibitor for the management of HER2-positive breast cancers.

Tannic acid (TA), is a potent anti-oxidant, showing anti-proliferative effects on numerous cancers. The ability of TA to induce proliferation inhibition on the rare tumor, gingival squamous cell carcinoma (GSCC), comprising

Sorghum contains phytochemicals that can protect against multiple forms of cancers. However, the underlying molecular targets and cellular mechanisms remain unknown. We investigated the role of Hwanggeumchal sorghum extracts (HSE) on colon cancer cells. We found HSE inhibited the proliferation of human colon cancer cells in a dose-dependent manner by inducing G1 phase arrest and apoptosis. Likewise, it suppressed the Jak2/STAT3 and PI3K/AKT/mTOR pathways. Studies on STAT3 transcription regulatory functions showed HSE inhibited the STAT3/DNA binding and transcription promoter activity. Thereby the expression of STAT3 downstream targets VEGF and VEGF-R2 were dropped. Furthermore, HSE treatment suppressed tumor growth and pulmonary metastasis in animal models. Together, these findings suggested that the targeted inhibition of Jak2/STAT3 and PI3K/Akt/mTOR contribute to cancer therapy potential of H. sorghum (HS). Thus, use of sorghum as a dietary supplement has the potential as a nutraceutical to prevent the onset of colon cancer, without any side effects.

Tumor angiogenesis is one of the major hallmarks of tumor progression. Nobiletin is a natural flavonoid isolated from citrus peel that has anti-angiogenic activity. Steroid receptor coactivator (Src) is an intracellular tyrosine kinase so that focal adhesion kinase (FAK) binds to Src to play a role in tumor angiogenesis. Signal transducer and activator of transcription 3 (STAT3) is a marker for tumor angiogenesis which interacts with Src. Paxillin (PXN) acts as a downstream target for both FAK and STAT3. The main goal of this study was to assess inhibition of tumor angiogenesis by nobiletin in estrogen receptor positive (ER+) breast cancer cells via Src, FAK, and STAT3-mediated signaling through PXN. Treatment with nobiletin in MCF-7 and T47D breast cancer cells inhibited angiogenesis markers, based on western blotting and RT-PCR. Validation of in vitro angiogenesis in the human umbilical vein endothelial cells (HUVEC) endothelial cell line proved the anti-angiogenic activity of nobiletin. Electrophoretic mobility shift assay and the ChIP assay showed that nobiletin inhibits STAT3/DNA binding activity and STAT3 binding to a novel binding site of the PXN gene promoter. We also investigated the migration and invasive ability of nobiletin in ER+ cells. Nobiletin inhibited tumor angiogenesis by regulating Src, FAK, and STAT3 signaling through PXN in ER+ 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 p21Waf1/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/p21Waf1/Cip1 pathways and induce G1‐arrest and intrinsic apoptosis in breast carcinomas.

Sorghum is a principal cereal food in a number of parts of the world and is critical in folk medicine in Asia and Africa. However, its effects on bone are unknown. Growth hormone (GH) is a regulator of bone growth and bone metabolism. GH activates several signaling pathways, including the Janus kinase (Jak)/signal transducer and activator of transcription (STAT) pathways, thereby regulating expression of genes, including insulin‑like growth factor (IGF)‑1. Bone morphogenetic proteins (BMPs) induce the differentiation of cells of the osteoblastic lineage, increasing the pool of IGF‑1 target cells, the mature osteoblasts. In the present study, the effects of Hwanggeumchal sorghum extracts (HSE) on GH signaling via the Jak/STAT pathway in osteoblasts were investigated. HSE was not observed to be toxic to osteoblastic cells and increased the expression of BMP7 and GH‑related proteins, including STAT5B, p‑STAT5B, IGF‑1 receptor (IGF-1R), growth receptor hormone (GHR) and Jak2 in MC3T3‑E1 cells. In addition, HSE increased BMP7 and GHR mRNA expression in MC3T3‑E1 cells. The expression of HSE‑induced BMP7 and GHR was inhibited by AG490, a Jak2 kinase inhibitor. The observations indicate that HSE‑induced signaling is similar to GH signaling via the GHR‑Jak2 signaling axis. Using small interference RNA (siRNA) analysis, STAT5B was found to play an essential role in HSE‑induced BMP7 and GH signaling in MC3T3‑E1 cells. Results of the current study indicate that HSE promotes bone growth through activation of STAT5B.

Worldwide, breast cancer (BCa) is the most common cancer in women. Among its subtypes, triple-negative breast cancer (TNBC) is an aggressive form associated with diminished survival. TNBCs are characterized by their absence, or minimal expression, of the estrogen and progesterone receptors, as well as the human epidermal growth factor receptor 2 (i.e. ER-/-, PR-/-, Her2-/Low). Consequently, treatment for this subtype of BCa remains problematic. Silibinin, a derivative of the flavonoid silymarin, is reported to have anticancer activities against hepatic and non-small cell lung cancers. We hypothesized that silibinin might inhibit cell-extracellular matrix interactions via the regulation, expression, and activation of STAT3 in TNBCs, which could directly inhibit metastasis in silibinin-treated BCa cells. Using proliferation assays, we found that exposure to silibinin at a concentration of 200 µM inhibited the proliferation of breast cancer (BCa) cells; this concentration also inhibited phosphorylation of STAT3 and its principal upstream kinase, Jak2. Furthermore, we found that silibinin inhibited the nuclear translocation of STAT3, as well as its binding to the MMP2 gene promoter. The ability of silibinin to inhibit metastasis was further studied using an in vitro invasion assay. The results confirm the role of STAT3 as a critical mediator in the invasive potential of BCa cells, and STAT3 knock-down resulted in inhibition of invasion. The invasion ability of silibinin-treated BCa cells was studied in detail with the expression of MMP2. Prevention of STAT3 activation also resulted in the inhibition of MMP2 expression. Use of a small interfering RNA to knock down STAT3 (siSTAT3) allowed us to confirm the role of STAT3 in regulating MMP2 expression, as well as the mechanism of action of silibinin in inhibiting MMP2. Taken together, we found that silibinin inhibits the Jak2/STAT3/MMP2 signaling pathway, and inhibits the proliferation, migration, and invasion of triple-negative BCa cells.

Osteoclast differentiation is dependent on the activities of receptor activator NF-kB ligand (RANKL) and macrophage colony-stimulating factor (M-CSF). Given that RANKL plays a critical role in osteoclast formation and bone resorption, any new compounds found to alter its activity would be predicted to have therapeutic potential for disorders associated with bone loss. Methylsulfonylmethane (MSM) is a naturally occurring sulfur compound with well-documented anti-oxidant and anti-inflammatory properties; currently its effects on osteoclast differentiation are unknown. We sought to investigate whether MSM could regulate osteoclastogenesis, and if so, its mechanism of action. In this study, we investigated the effects of MSM on RANKL-induced osteoclast differentiation, together with STAT3's involvement in the expression of osteoclastic gene markers. These experiments were conducted using bone marrow derived macrophages (BMMs) and cell line material, together with analyses that interrogated both protein and mRNA levels, as well as signaling pathway activity. Although MSM was not toxic to osteoclast precursors, MSM markedly inhibited RANKL-induced TRAP activity, multinucleated osteoclast formation, and bone resorptive activity. Additionally, the expression of several osteoclastogenesis-related marker genes, including TRAF6, c-Fos, NFATc1, cathepsin K, and OSCAR were suppressed by MSM. MSM mediated suppression of RANKL-induced osteoclastogenesis involved inhibition of ITAM signaling effectors such as PLCγ and Syk, with a blockade of NF-kB rather than MAPK activity. Furthermore, MSM inhibited RANKL-induced phosphorylation of STAT3 Ser727. Knockdown of STAT3 using shRNAs resulted in reduced RANKL-mediated phosphorylation of Ser727 STAT3, and TRAF6 in cells for which depletion of STAT3 was confirmed. Additionally, the expression of RANKL-induced osteoclastogenic marker genes were significantly decreased by MSM and STAT3 knockdown. Taken together, these results indicate that STAT3 plays a pivotal role in RANKL-induced osteoclast formation, and that MSM can attenuate RANKL-induced osteoclastogenesis by blocking both NF-kB and STAT3 activity.

Background Combination therapy, which reduces the dosage intensity of the individual drugs while increasing their efficacy, is not a novel approach for the treatment of cancer. Methylsulfonylmethane (MSM) is an organic sulfur compound shown to act against tumor cells. Tamoxifen is a commercially available therapeutic agent for breast malignancies. Methods In the current study, we analyzed the combinatorial effect of MSM and tamoxifen on the suppression of ER-positive breast cancer xenograft growth and metastasis. Additionally, we also validated the molecular targets by which the drug combination regulated tumor growth and metastasis. Results We observed that the combination of MSM and tamoxifen regulated cell viability and migration in vitro. The intragastric administration of MSM and subcutaneous implantation of tamoxifen tablets led to tumor growth suppression and inhibition of the Janus kinase 2 (Jak2)/signal transducer and activator of transcription 5b (STAT5b) pathway. Our study also assessed the regulation of signaling molecules implicated in the growth, progression, differentiation, and migration of cancer cells, such as Jak2, STAT5b, insulin-like growth factor-1Rβ, and their phosphorylation status. Conclusions Study results indicated that this combination therapy inhibited tumor growth and metastasis. Therefore, this drug combination may have a synergistic and powerful anticancer effect against breast cancer. Electronic supplementary material The online version of this article (doi:10.1186/s12885-015-1445-0) contains supplementary material, which is available to authorized users.

Hypoxia, a common consequence of solid tumor growth in breast cancer or other cancers, serves to propagate a cascade of molecular pathways which include angiogenesis, glycolysis, and various cell-cycle control proteins. As we have shown previously, hypoxia activates STAT5 (signal transducer and activator of transcription 5) and increases its binding activity to the GAS element in mammary epithelial cells. In this study we attempted to elucidate the mechanism by which cyclin D1 is regulated by the STAT5 protein under hypoxic conditions. Our data demonstrate that hypoxia (2% O(2)) or desferrioxamine (DFO) induces tyrosine and serine phosphorylation of STAT5 in human breast cancer cells (MCF-7) and mammary epithelial cells (HC11). Imunoprecipitation and subsequent Western analysis showed that Jak2 leads to the tyrosine phosphorylation and activation of STAT5a or STAT5b under hypoxic conditions. Using a transfected COS-7 cell model system, we demonstrate that the activity of a cyclin D1 promoter-luciferase construct increased under hypoxic conditions or DFO treatment. The activity of the STAT5b/cyclin D1 promoter increased significantly by 12 h of hypoxia, whereas the activity of the STAT5a/cyclin D1 promoter was unaffected under hypoxic conditions. These increases in promoter activity are predominantly mediated by the Jak2/STAT5b signaling pathway. We have shown by EMSA that hypoxia induces STAT5 to bind to the cyclin D1 promoter (GAS-1) in MCF-7 and HC11 cells. These data suggest that STAT5b may mediate the transcriptional activation of cyclin D1 after hypoxic stimulation.

Aberrantly enhanced vascular endothelial growth factor (VEGF) gene expression is associated with increased tumor growth and metastatic spread of solid malignancies, including human renal carcinomas. Persistent activation of STAT3 is linked to tumor-associated angiogenesis, but underlying mechanisms remain unclear. Therefore, we examined whether STAT3 modulates the stability and activity of hypoxia-inducible factor-1alpha (HIF-1alpha), and in turn enhances VEGF expression. We found that STAT3 was activated in ischemic rat kidneys and hypoxic human renal carcinoma cells. We also found that hypoxia-induced activation of STAT3 transactivated the VEGF promoter and increased the expression of VEGF transcripts. Consistent with these findings, STAT3 inhibition attenuated the hypoxic induction of VEGF. Interestingly, activated STAT3 increased HIF-1alpha protein levels due to the HIF-1alpha stability by blocking HIF-1alpha degradation and accelerated its de novo synthesis. The novel interaction of STAT3 with HIF-1alpha was identified in hypoxic renal carcinoma cells. Furthermore, hypoxia recruited STAT3, HIF-1alpha, and p300 to the VEGF promoter and induced histone H3 acetylation. Therefore, these findings provide compelling evidence that a causal relationship exists between STAT3 activation and HIF-1-dependent angiogenesis and suggest that therapeutic modalities designed to disrupt STAT3 signaling hold considerable promise for the blocking tumor growth and enhancing apoptosis of cancer cells and tissues.

Human urinary bladder cancer is the fifth most common cancer, with a worldwide estimate of about two million patients. Recurrence after complete transurethral prostatic resection is the most important problem in therapy. Combination therapy is a new approach in the treatment of cancers that do not respond to current therapies. These therapies have many advantages over conventional therapies, such as fewer side-effects and greater efficiency. Research efforts using natural compounds for the elimination or growth suppression of the cancer arise from studies on methylsulfonylmethane (MSM). MSM is a natural sulfur compound with no side-effects. AG490 is a tyrosine kinase inhibitor that has been extensively used for inhibiting Jak2 in vitro and in vivo. In our study, the combinatorial effect of these two agents on human bladder cancer cell lines and xenografts was analyzed. We observed that the combination of AG490 and MSM inhibited cancer cell viability and cell migration in vitro. This combination inhibited VEGF mRNA expression in bladder cancer cell lines. In vivo experiments showed that oral administration of AG490 and MSM combination significantly inhibited the growth of tumor xenografts in mice. Our study clearly demonstrates that the predominant effect of this combination is the reduction of signaling molecules including STAT3, STAT5b, IGF-1R, VEGF and VEGF-R2 which are involved in the growth, progression and metastasis of human bladder cancer. The anti-metastatic ability of this drug combination is confirmed using metastatic animal models. Therefore, this combination could have the effect of genesistasis and powerful anticancer effects against bladder cancer.

Hsp90α is a molecular chaperone protein involved in the structural maturation of oncogenic signaling proteins. Hsp90 was recently identified as an anticancer target; various studies are ongoing to find ways for managing cancer through Hsp90α. However, this approach is limited by reported side-effects. Hypoxia is a hallmark of solid tumors, including those of breast cancer and the extent of tumor hypoxia is associated with resistance to treatment and poor prognosis. One of the major signaling pathways in cancer cells, the Jak2/STAT5b pathway, has been found to be closely correlated with hypoxia. The objective of this study was to investigate the role of Jak2/STAT5b in the regulation of Hsp90α expression so that Hsp90α targeting can be achieved indirectly by modulating the Jak2/STAT5b pathway. We examined the role of the Jak2/STAT5b pathway in the expression of Hsp90α under hypoxic conditions by immunoblotting, reporter gene assays, EMSA and RNA interference analysis. With the help of in vivo models, we also analyzed the expression of Hsp90α in different parts of solid tumor tissues. We found a close association between hypoxic stress and Hsp90α expression. We also determined that STAT5b regulates the expression of Hsp90α during hypoxic stimulation. Under hypoxic conditions the expression of Hsp90α and STAT5b were proportional. siRNA analysis and nucleotide analysis showed that the promoter of Hsp90α has a STAT5b binding domain. Our work confirmed that STAT5b is one of the transcription factors that regulate Hsp90α. We, therefore, concluded that under hypoxic conditions, the Jak2/STAT5b pathway regulates Hsp90α expression and it could serve as a promising target for the treatment of solid tumors.

Cyclin D1 and insulin-like growth factor 1 receptor (IGF-1R) are key regulators of cell proliferation that are overexpressed in most breast cancers. The purpose of the present study was to investigate the molecular mechanism by which hemin exerts its inhibitory effects on aggressive breast cancer cells. We found that hemin regulates cyclin D1 and IGF-1R proteins and insulin-like growth factor-1 gene expression through STAT5b in breast cancer cells. We confirmed that STAT5b, cyclin D1, and IGF-1R is up-regulated by hypoxia, and the increased STAT5b binds strongly to the STAT5-binding sites contained within the distal 5'-flanking region of IGF-1 gene in breast cancer cells. EMSA studies showed that STAT5 binding activity to the IGF-1 and cyclin D1 promoter was distinctly decreased by hemin in STAT5b-transfected COS-7 or MDA-MB 231 cells. IGF-1 gene expression was also decreased by hemin in mammary epithelial cells. STAT5b expression was inhibited in siRNA experiments and by hemin, leading to decreased levels of IGF-1. These results provide a basis for molecular targets in cancer treatment via the STAT5b/IGF-1 or /cyclin D1 pathway in solid tumor cells. These data indicate that hemin inhibits the cyclin D1 and IGF-1 expression via STAT5b under hypoxia in ERalpha-negative breast cancer cells. These findings are valuable toward understanding the role of hemin-induced inhibition of cyclin D1 and IGF-1 expression under hypoxia in invasive and metastatic breast cancer.

The KLF6 is a zinc-finger tumor suppressor that is frequently mutated in several human cancers and broadly involved in differentiation and development, growth-related signal transduction, cell proliferation, apoptosis, and angiogenesis. To determine whether genetic alterations of KLF6 gene are involved in the development and/or progression of gastric cancer, we have screened a set of 80 sporadic gastric cancers for mutations and allele loss of the KLF6 gene. Four missense mutations, S155R, P172 T, S180L, and R198 K, were detected in transactivation domain of the KLF6 gene and one of them had biallelic mutations with somatic mutation of one allele and loss of the remaining allele. All of the cases with mutation were of advanced intestinal-type gastric cancer with lymph node metastasis. In addition, 16 (43.2%) of 37 informative cases showed allelic loss at KLF6 locus. Interestingly, allelic loss was also frequent in intestinal-type gastric cancer. Therefore, our data suggest that genetic alterations of KLF6 gene might play an important role in the development or progression of sporadic gastric cancers.

Several constitutively activated signal transducers and activators of transcription (STAT) proteins have been observed in a wide number of human cancer cell lines and primary tumors. Normal cells maintain normoxic conditions but tumor cells are characteristically hypoxic. We studied the altered activation and tyrosine phosphorylation of STATs under hypoxic conditions (2% O2) or desferrioxamine (DFO) treatment in mouse mammary epithelial cells (HC11) and a human breast cancer cell line (MCF-7). STAT1, -3 and -5 proteins are especially important and are observed at elevated levels in tumorigenesis. We also investigated the serine phosphorylation of STAT1, -3, and -5 under hypoxic conditions or DFO treatment in HC11 and MCF-7 cells. Here we show that DFO or hypoxia stimulates the tyrosine and/or serine phosphorylation and the expression of STAT proteins in breast cancer cells. Our data suggest that DFO or hypoxic condition is a critical stimulator for the activation of STAT proteins in breast cancer cells. These results may provide the basis for identifying another mechanism of breast tumorigenesis via the JAK/STAT pathway in hypoxia. Also, activation of STAT proteins by hypoxia may play an important role in the physiological phenomenon of embryonic stem cells and old cells with hypoxic conditions.

We analyzed the genetic alterations of VHL, HGF/SF, and Met genes and the expression pattern of HGF/SF and Met protein in 26 renal cell carcinomas (RCCs). We found five mutations of the VHL gene and frequent LOH (50%) only in non-papillary clear cell RCC. We found six cases in which the CpG island of VHL was methylated. In addition, one missense mutation of the HGF/SF gene was detected in clear cell RCC. HGF/SF and Met protein were expressed in 84.6% and 80.7% of RCCs, respectively. All of the cases with the genetic alterations of VHL or HGF/SF demonstrated strong expression of HGF/SF and Met protein in RCC cells. Statistically, genetic alterations of VHL and HGF/SF were significantly correlated with HGF/SF and Met expression (Fisher's exact test, p=0.022 and p=0.0070). Thus, these results strongly suggest that the expression of HGF/SF and Met protein is closely associated with the genetic alterations of VHL and HGF/SF in primary RCCs.

Gastric carcinoma may occur sporadically or in association with hereditary diseases, such as Peutz-Jehgers syndrome (PJS). The PJS gene (named STK11 or LKB1) was mapped to 19p13.3 and recently cloned. Germ-line mutations of the gene have been detected in familial PJS patients and are predicted to predispose STK11 carriers to the development of a wide range of gastrointestinal and other neoplasms. To elucidate the etiological role of the STK11 gene in sporadic gastric carcinoma tumorigenesis, we analyzed 28 gastric carcinomas (22 of intestinal type and 6 of diffuse type) for STK11 gene mutations. STK11 gene mutations were detected in 3 of 28 gastric carcinomas but were not seen in the corresponding germ-line DNA sequence. In one tumor, a missense mutation, C-to-T transition, was detected at codon 324 resulting in proline to leucine substitution; in the other two, silent mutations were detected at codons 106 and 350, respectively. While these results suggest that somatic STK11 mutations are not common in sporadic gastric carcinomas, they may occur in a subset of these tumors.

Methylsulfonylmethane (MSM) is a naturally occurring sulfur compound with well-known anti-oxidant properties and anti-inflammatory activities. But, its effects on bone are unknown. Growth hormone (GH) is regulator of bone growth and bone metabolism. GH activates several signaling pathways such as the Janus kinase (Jak)/signal transducers and activators of transcription (STAT) pathway, thereby regulating expression of genes including insulin-like growth factor (IGF)-1. GH exerts effects both directly and via IGF-1, which signals by activating the IGF-1 receptor (IGF-1R). In this study, we investigated the effects of MSM on the GH signaling via the Jak/STAT pathway in osteoblasts and the differentiation of primary bone marrow mesenchymal stem cells (MSCs). MSM was not toxic to osteoblastic cells and MSCs. MSM increased the expression of GH-related proteins including IGF-1R, p-IGF-1R, STAT5b, p-STAT5b, and Jak2 in osteoblastic cells and MSCs. MSM increased IGF1R and GHR mRNA expression in osteoblastic cells. The expression of MSM-induced IGF-1R and GHR was inhibited by AG490, a Jak2 kinase inhibitor. MSM induced binding of STAT5 to the IGF-1R and increased IGF-1 and IGF-1R promoter activities. Analysis of cell extracts by immunoprecipitation and Western blot showed that MSM enhanced GH-induced activation of Jak2/STAT5b. We found that MSM and GH, separately or in combination, activated GH signaling via the Jak2/ STAT5b pathway in UMR-106 cells. Using siRNA analysis, we found that STAT5b plays an essential role in GH signaling activation in C3H10T1/2 cells. Osteogenic marker genes (ALP, ON, OCN, BSP, OSX, and Runx2) were activated by MSM, and siRNA-mediated STAT5b knockdown inhibited MSM-induced expression of osteogenic markers. Furthermore, MSM increased ALP activity and the mineralization of MSCs. Taken together, these results indicated that MSM can promote osteogenic differentiation of MSCs through activation of STAT5b.

Background Cancer is one of the highly virulent diseases known to humankind with a high mortality rate. Breast cancer is the most common cancer in women worldwide. Sorghum is a principal cereal food in many parts of the world, and is critical in folk medicine of Asia and Africa. In the present study, we analyzed the effects of HSE in metastatic breast cancer. Methodology/Principal Findings Preliminary studies conducted on MDA-MB 231 and MCF-7 xenograft models showed tumor growth suppression by HSE. Western blotting studies conducted both in vivo and in vitro to check the effect of HSE in Jak/STAT pathways. Anti-metastatic effects of HSE were confirmed using both MDA-MB 231 and MCF-7 metastatic animal models. These studies showed that HSE can modulate Jak/STAT pathways, and it hindered the STAT5b/IGF-1R and STAT3/VEGF pathways not only by down-regulating the expression of these signal molecules and but also by preventing their phosphorylation. The expression of angiogenic factors like VEGF, VEGF-R2 and cell cycle regulators like cyclin D, cyclin E, and pRb were found down-regulated by HSE. In addition, it also targets Brk, p53, and HIF-1α for anti-cancer effects. HSE induced G1 phase arrest and migration inhibition in MDA-MB 231 cells. The metastasis of breast cancer to the lungs also found blocked by HSE in the metastatic animal model. Conclusions/Significance Usage of HS as a dietary supplement is an inexpensive natural cancer therapy, without any side effects. We strongly recommend the use of HS as an edible therapeutic agent as it possesses tumor suppression, migration inhibition, and anti-metastatic effects on breast cancer

Breast cancer is the most aggressive form of all cancers, with high incidence and mortality rates. The purpose of the present study was to investigate the molecular mechanism by which methylsulfonylmethane (MSM) inhibits breast cancer growth in mice xenografts. MSM is an organic sulfur-containing natural compound without any toxicity. In this study, we demonstrated that MSM substantially decreased the viability of human breast cancer cells in a dose-dependent manner. MSM also suppressed the phosphorylation of STAT3, STAT5b, expression of IGF-1R, HIF-1 alpha, VEGF, BrK and p-IGF-1R and inhibited triple-negative receptor expression in receptor-positive cell lines. Moreover, expression in receptor-positive cell-lines. Moreover, MSM decreased the DNA-binding activities of STAT5b and STAT3, to the target gene promoters in MDA-MB 231 or co-transfected COS-7 cells. We confirmed that MSM significantly decreased the relative luciferase activities indicating crosstalk between STAT5b/IGF-1R, STAT5b/HSP90 alpha, and STAT3/VEGF. To confirm these findings in vivo, xenografts were established in Balb/c athymic nude mice with MDA-MB 231 cells and MSM was administered for 30 days. Concurring to our in vitro analysis, these xenografts showed decreased expression of STAT3, STAT5b, IGF-1R and VEGF. Through in vitro and in vivo analysis, we confirmed that MSM can effectively regulate multiple targets including STAT3/VEGF and STAT5b/IGF-1R. These are the major molecules involved in tumor development, progression, and metastasis: Thus, we strongly recommend the use of MSM as a trial drug for treating all types of breast cancers including triple-negative cancers.

We have shown previously that hypoxia activates the cyclin D1 promoter via the Jak2/STAT5b pathway in breast cancer cells. Most solid tumors contain hypoxic components and overexpression of cyclin D1. The purpose of the present study was to investigate the molecular mechanism by which momilactone B exerts its inhibitory effects on breast cancer cells. Momilactone B, extracted from Korean rice hulls, suppressed hypoxia-induced increases in phospho-STAT5, STAT5b, cyclin D1, and cdk4 protein levels in human breast cancer cells. STAT5b expression was inhibited by siRNA experiments leading to decreased cyclin D1. The effects of momilactone B on cell growth and apoptosis-related gene expression were investigated in breast cancer cells under hypoxic conditions (2% O2). Bax and p21 expression was found to be up-regulated, whereas ppRb and bcl-2 were down-regulated in momilactone B-treated cells under hypoxic conditions. However, the p53 protein level did not change. Flow cytometry with Annexin-FITC staining showed that the number of apoptotic cells increased in hypoxic cells treated with momilactone B compared with untreated hypoxic cells. Furthermore, caspase activity increased upon treatment with momilactone B under hypoxic conditions. These results indicate that momilactone B inhibits the growth of breast cancer cells, regulates the expression of apoptosis-related genes, and induces apoptosis through STAT5b and a caspase-3 dependent pathway. We suggest that momilactone B accelerates hypoxia-induced apoptosis of human breast cancer cells through STAT5b, and may represent an effective chemopreventive or therapeutic agent against breast cancer.