Active Stat3 is required for survival of human squamous cell carcinoma cells in serum-free conditions

Pancreatic neuroendocrine tumor progression and resistance to everolimus: the crucial role of NF-kB and STAT3 interplay

PURPOSE

The finding of mTOR overactivation in patients affected by pancreatic neuroendocrine tumors (Pa-NETs) led to their treatment with the mTOR inhibitor everolimus. Unfortunately, the efficacy of everolimus is restricted by the occurrence of resistance. The mechanisms leading to Pa-NETs' progression and resistance are not well understood. Notably, chronic inflammation is implicated in NET development. NF-kB is involved in inflammation and drug resistance mechanisms through the activation of several mediators, including STAT3. In this respect, NF-κB and STAT3 interaction is implicated in the crosstalk between inflammatory and tumor cells.

METHODS

We investigated the expression of NF-kB in different Pa-NETs by RT-qPCR and immunohistochemistry. Then, we studied the role of NF-κB and STAT3 interplay in QGP-1 cells. Subsequently, we assessed the impact of NF-κB and STAT3 inhibitors in QGP-1 cell proliferation and spheroids growth. Finally, we evaluated the implication of the NF-kB pathway in everolimus-resistant Pa-NET cells.

RESULTS

We found that the increased NF-kB expression correlates  with a higher grade in Pa-NETs. The activation of the STAT3 pathway induced by TNFα is mediated by NF-kB p65. NF-kB p65 and STAT3 inhibitors decrease QGP-1 viability, spheroids growth, and Pa-NETs cell proliferation. These effects are maintained in everolimus-resistant QGP-1R cells. Interestingly, we found that NF-kB, STAT3, IL-8, and SOCS3 are overexpressed in QGP-1R compared to QGP-1.

CONCLUSION

Since the NF-kB pathway is implicated in Pa-NETs' progression and resistance to everolimus, these data could explain the potential use of NF-kB as a novel therapeutic target in Pa-NET patients.

Chronic nitric oxide exposure induces prostate cell carcinogenesis, involving genetic instability and a pro-tumorigenic secretory phenotype

Prostate cancer is a leading cause of cancer death in men. Inflammation and overexpression of inducible nitric oxide synthase (NOS2) have been implicated in prostate carcinogenesis. We aimed to explore the hypothesis that nitric oxide NO exerts pro-tumorigenic effects on prostate cells at physiologically relevant levels contributing to carcinogenesis. We investigated the impact of acute exposure of normal immortalised prostate cells (RWPE-1) to NO on cell proliferation and activation of DNA damage repair pathways. Furthermore we investigated the long term effects of chronic NO exposure on RWPE-1 cell migration and invasion potential and hallmarks of transformation. Our results demonstrate that NO induces DNA damage as indicated by γH2AX foci and p53 activation resulting in a G1/S phase block and activation of 53BP1 DNA damage repair protein. Long term adaption to NO results in increased migration and invasion potential, acquisition of anchorage independent growth and increased resistance to chemotherapy. This was recapitulated in PC3 and DU145 prostate cancer cells which upon chronic exposure to NO displayed increased cell migration, colony formation and increased resistance to chemotherapeutics. These findings indicate that NO may play a key role in the development of prostate cancer and the acquisition of an aggressive metastatic phenotype.

The chromosome 21 kinase DYRK1A: emerging roles in cancer biology and potential as a therapeutic target

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) is a serine/threonine kinase that belongs to the DYRK family of proteins, a subgroup of the evolutionarily conserved CMGC protein kinase superfamily. Due to its localization on chromosome 21, the biological significance of DYRK1A was initially characterized in the pathogenesis of Down syndrome (DS) and related neurodegenerative diseases. However, increasing evidence has demonstrated a prominent role in cancer through its ability to regulate biologic processes including cell cycle progression, DNA damage repair, transcription, ubiquitination, tyrosine kinase activity, and cancer stem cell maintenance. DYRK1A has been identified as both an oncogene and tumor suppressor in different models, underscoring the importance of cellular context in its function. Here, we review mechanistic contributions of DYRK1A to cancer biology and its role as a potential therapeutic target.

Effects of Interleukin-6 on STAT3-regulated signaling in oral cancer and as a prognosticator of patient survival

OBJECTIVES

Human oral squamous cell carcinoma (OSCC) produces an inflammatory microenvironment enriched with cytokines including interleukin-6 (IL-6); however, the underlying molecular mechanisms of OSCC progression are unclear. We aimed to delineate the STAT3-mediated signaling pathways involved in tumor cell survival and growth.

MATERIALS AND METHODS

Immunohistochemistry was used to semi-quantitate IL-6 and STAT3 in 111 OSCC tissues. IL-6-induced STAT3 signaling pathways and effects on tumor cell survival and progression were investigated in vitro and in xenograft mouse models. Effects of blocking IL-6-induced activation of STAT3 in an OSCC cell line were determined in vitro.

RESULTS

A higher level of IL-6 or STAT3 in situ was associated with an unfavorable prognosis in OSCC patients with regard to both disease-free and overall survival rates. Overexpressed or exogenous IL-6 could induce SAS cell proliferationin vitroand significantly enhanced tumor growthin vivo. In addition, knockdown or inhibition of STAT3 expression in SAS cells significantly reduced tumor growth and abolished the responsiveness to IL-6 stimulation. Siltuximab or Tocilizumab could also significantly suppress IL-6-induced STAT3 phosphorylation and STAT3 nuclear translocation, resulting in a significant decrease of downstream anti-apoptotic proteins Bcl-2, Bcl-xL, and survivin.

CONCLUSION

The IL-6 level in the tumor microenvironment could serve as a stage-independent predictor of OSCC progression and survival. Further, IL-6 may play a role in this disease through STAT3-dependent upregulation of anti-apoptotic genes and subsequent proliferation of tumor cells.

Costunolide, a Sesquiterpene Lactone, Suppresses Skin Cancer via Induction of Apoptosis and Blockage of Cell Proliferation

Costunolide is a naturally occurring sesquiterpene lactone that demonstrates various therapeutic actions such as anti-oxidative, anti-inflammatory, and anti-cancer properties. Costunolide has recently emerged as a potential anti-cancer agent in various types of cancer, including colon, lung, and breast cancer. However, its mode of action in skin cancer remains unclear. To determine the anti-cancer potential of costunolide in skin cancer, human epidermoid carcinoma cell line A431 was treated with costunolide. A lactate dehydrogenase assay showed that costunolide diminished the viability of A431 cells. Apoptotic cells were detected by annexin V/propidium iodide double staining and Terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay assay, and costunolide induced cell apoptosis via activation of caspase-3 as well as induction of poly-ADP ribose polymerase cleavage in A431 cells. In addition, costunolide elevated the level of the pro-apoptotic protein Bax while lowering the levels of anti-apoptotic proteins, including Bcl-2 and Bcl-xL. To address the inhibitory effect of costunolide on cell proliferation and survival, various signaling pathways, including mitogen-activated protein kinases, signal transducer and activator of transcription 3 (STAT3), nuclear factor κB (NF-κB), and Akt, were investigated. Costunolide activated the p38 and c-Jun N-terminal kinase pathways while suppressing the extracellular signal-regulated kinase (ERK), STAT3, NF-κB, and Akt pathways in A431 cells. Consequently, it was inferred that costunolide suppresses cell proliferation and survival via these signaling pathways. Taken together, our data clearly indicated that costunolide exerts anti-cancer activity in A431 cells by suppressing cell growth via inhibition of proliferation and promotion of apoptosis. Therefore, it may be employed as a potentially tumor-specific candidate in skin cancer treatment.

Physalis alkekengi var. franchetii Extracts Exert Antitumor Effects on Non-Small Cell Lung Cancer and Multiple Myeloma by Inhibiting STAT3 Signaling

Background

Physalis alkekengi var. franchetii is an herb that possesses various ethnopharmacological applications. Herein, our current study focuses on the antitumor effect of a combination of physalins, which are regarded as the most representative secondary metabolites from calyces of Physalis alkekengi var. franchetii.

Materials and Methods

We mainly investigated the antitumor activity of the physalins extracted from Physalis alkekengi var. franchetii on both solid and hematologic cancers. The main cells used in this study were NCI-H1975 and U266 cells. The major assays used were the CCK-8 assay, Western blot analyses, immunofluorescence assay and Annexin V assay, and a xenograft mouse model was used.

Results

The results showed that physalins exhibited a strong antitumoural effect on both non-small cell lung cancer (NSCLC) and multiple myeloma (MM) cells by suppressing constitutive STAT3 activity and further inhibiting the downstream target gene expression induced by STAT3 signaling, which resulted in the enhanced apoptosis of tumor cells. Moreover, physalins significantly reduced tumor growth in xenograft models of lung cancer.

Conclusion

Collectively, these findings demonstrated that the physalins from Physalis alkekengi var. franchetii may potentially act as cancer preventive or chemotherapeutic agents for NSCLC and MM by inhibiting the STAT3 signaling pathway. The present study served as a promising guide to further explore the precise mechanism of Physalis alkekengi var. franchetii in cancer treatment.

Rhus verniciflua Stokes extract suppresses migration and invasion in human gastric adenocarcinoma AGS cells

BACKGROUND/OBJECTIVES

Many studies have suggested that Rhus verniciflua Stokes (RVS) and its extract are anticancer agents. However, RVS had limited use because it contains urushiol, an allergenic toxin. By improving an existing allergen-removal extraction method, we developed a new allergen-free Rhus verniciflua Stokes extract (RVSE) with higher flavonoid content. In this study, we examined whether RVSE inhibits the ability of AGS gastric cancer cells to migrate and invade.

MATERIALS/METHODS

The flavonoids content of RVSE was analyzed by HPLC. The effects of RVSE on migration and invasion in AGS cells were analyzed by each assay kit. Matrix metalloproteinase (MMP)-9, plasminogen activator inhibitor-1 (PAI-1) and urokinase-type plasminogen activator (uPA) protein expression was analyzed by protein antibody array. The Phosphorylation of signal transducer and activator of transcription (STAT) 3 were assayed by Western blot analysis.

RESULTS

RVSE treatment with 0-100 μg/mL dose-dependently reduced the ability of AGS cells to migrate and invade. Notably, treatment with RVSE strongly inhibited the expression of MMP-9 and uPA and the phosphorylation of STAT3. In contrast, RVSE treatment dramatically increased the expression of PAI-1. These results indicate that the inhibition of MMP-9 and uPA expression and STAT3 phosphorylation and the stimulation of PAI-1 expression contributed to the decreased migration and invasion of AGS cells treated with RVSE.

CONCLUSIONS

These results suggest that RVSE may be used as a natural herbal agent to reduce gastric cancer metastasis.

High expression of ALDH1A3 might independently influence poor progression-free and overall survival in patients with glioma via maintaining glucose uptake and lactate production

Recent studies have found that the acetaldehyde dehydrogenase 1A3 (ALDH1A3) gene is a marker of glioma stem cells. A total of 115 brain glioma specimens were collected and classified into grade I-IV, while non-tumor brain tissue specimens, taken from 12 patients of vascular malformation surgery, were used as control. ALDH1A3 gene promoter methylation in glioma tissues was detected by pyrosequencing, while immunohistochemistry and western blot were used to detect ALDH1A3 protein expressions in different grades of glioma tissues and normal brain tissues. The expression of ALDH1A3 in the glioma cell line U87 was detected by quantitative real-time polymerase chain reaction and RNA-Seq technology was applied to investigate differentially expressed genes before and after silencing the ALDH1A3 gene. Among the 115 glioma tissue specimens, 50 (43.48%) showed low and 65 (56.52%) high expression of ALDH1A3, but no expression was detected in the control. Univariate and multivariate COX regression analyses showed that the patient's tumor pathological grade, the methylation status of ALDH1A3 promoter, and the expression of ALDH1A3 protein were risk factors for progression-free survival (PFS) and overall survival (OS) (all P < 0.05) and the OS of mice with silenced ALDH1A3 in a glioma nude mouse model was prolonged. U87 experiments revealed that ALDH1A3 expression had significant effects on apoptosis, proliferation, cell cycle, mitochondrial membrane potential, glucose consumption, lactate production, invasion ability, and expression of the pyruvate kinase M2 (PKM2) and hexokinase 2 (HK2) in glioma cells. ALDH1A3 protein expression is a marker for poor PFS and OS in glioma patients.

Matrine enhances the efficacy of adriamycin chemotherapy in osteosarcoma cells by the STAT3 pathway

Matrine and adriamycin have been extensively considered to be effective in anticancer therapies. However, the role of matrine in the antitumor activity of adriamycin against human osteosarcoma (OS) remains elusive. The aim of this study was to investigate the effect of matrine in OS chemotherapy of adriamycin. In the study, we found that matrine promoted the inhibitory effect of adriamycin against OS cell proliferation and growth. Wound healing and transwell assays showed that the inhibitory effect of adriamycin against migration and invasion of OS cells was significantly enhanced by matrine. For the underlying mechanism investigation, we showed that adriamycin reduced the protein level of PCNA, MMP-9, phosphorylated STAT3, and survivin, which was further intensified by the application of matrine. These results show that matrine could promote the therapeutic efficacy of adriamycin against human OS.

Bradykinin promotes proliferation, migration, and invasion of cervical cancer cells through STAT3 signaling pathways

It has been reported recently that bradykinin (BK) is involved in the regulation of various processes in cancer cells. However, its role and underlying mechanism of action in cervical cancer (CC) are still unknown. In the present study, it was revealed that BK promoted proliferation, migration, and invasion of CC cells, whereas bradykinin B2 receptor antagonist HOE140 had the inverse effect. Furthermore, it was confirmed that overexpression of bradykinin B2 receptor (B2R) facilitated the proliferation, migration, and invasion of BK-treated CC cells, while knockdown of B2R had the opposite effect. Mechanistically, the present results revealed that the BK/B2R-induced biological function of CC cells occured by activating STAT3 signaling pathways, and that knockdown of B2R or B2R antagonist had the opposite effects. Moreover, it was demonstrated that BK/B2R facilitated CC cell migration and invasion by upregulating the expression of the STAT3-regulated products MMP2 and MMP9, while downregulating the expression of the pro-apoptotic protein cleaved caspase-9. Thus, the present findings revealed that BK promoted CC cell proliferation, migration, and invasion by binding to B2R via STAT3 signaling pathways.

Docoxahexaenoic Acid Induces Apoptosis of Pancreatic Cancer Cells by Suppressing Activation of STAT3 and NF-κB

The ω3-polyunsaturated fatty acid docosahexenoic acid (DHA) is known to induce apoptosis of cancer cells. In this study, DHA was shown to reduce viability of pancreatic cancer cells (PANC-1) by inducing DNA fragmentation, activating caspase-3, and increasing the ratio of Bax/Bcl-2. To determine the DHA mechanism of action, the impact of DHA on the activation of the key signaling proteins epidermal growth factor receptor (EGFR), signal transducer and activator of transcription factor 3 (STAT3), nuclear transcription factor-κB (NF-κB), and IκBα in PANC-1 cells was probed. The observed DHA suppression of NF-κB DNA-binding activity was found to result from reduced IκBα phosphorylation. The observed DHA-induced suppression of STAT3 activation was found to be the result of suppressed EGFR activation, which derives from the inhibitory effect of DHA on the integrity of localization of EGFR to cell membrane lipid rafts. Since the activation of STAT3 and NF-κB mediates the expression of survival genes cyclin D1 and survivin, DHA induced apoptosis by suppressing the STAT3/NF-κB-cyclin D1/survivin axis. These results support the proposal that DHA-induced apoptosis of pancreatic cells occurs via disruption of key pro-cell survival signaling pathways. We suggest that the consumption of DHA-enriched foods could decrease the incidence of pancreatic cancer.

Pim-3 enhances melanoma cell migration and invasion by promoting STAT3 phosphorylation

Melanoma is the deadliest form of commonly encountered skin cancer, and has fast propagating and highly invasive characteristics. Pim-3, a highly expressed oncogene in melanoma, is a highly conserved serine/threonine kinase with various biological activities, such as proliferation-accelerating and anti-apoptosis effects on cancer progression. However, whether Pim-3 regulates melanoma metastasis has not been determined. Here, we constructed a Pim-3-silencing short hairpin RNA (sh-Pim-3), a TLR7-stimulating ssRNA and a dual-function vector containing a sh-Pim-3 and a ssRNA, and transfected them into the B16F10 melanoma cell line to investigate the effects of Pim-3 on migration and invasion in melanoma. We found that sh-Pim-3 inhibited B16F10 cell migration and invasion in vitro. In a tumor-bearing mouse model, sh-Pim-3 significantly downregulated pulmonary metastasis of B16F10 melanoma cell in vivo. Mechanistically, sh-Pim-3 inhibited metastasis by regulating the expression of genes related to epithelial-mesenchymal transition (EMT). Further study revealed that by promoting the phosphorylation of STAT3 (signal transducer and activator of transcription 3), Pim-3 induced the expression of Slug, Snail, and ZEB1, which enhanced EMT-related changes and induced melanoma migration and invasion. Our study suggests that Pim-3 is a potential effective target for melanoma therapy.

STAT3 targeting by polyphenols: Novel therapeutic strategy for melanoma

Melanoma or malignant melanocytes appear with the low incidence rate, but very high mortality rate worldwide. Epidemiological studies suggest that polyphenolic compounds contribute for prevention or treatment of several cancers particularly melanoma. Such findings motivate to dig out novel therapeutic strategies against melanoma, including research toward the development of new chemotherapeutic and biologic agents that can target the tumor cells by different mechanisms. Recently, it has been found that signal transducer and activator of transcription 3 (STAT3) is activated in many cancer cases surprisingly. Different evidences supply the aspect that STAT3 activation plays a vital role in the metastasis, including proliferation of cells, survival, invasion, migration, and angiogenesis. This significant feature plays a vital role in various cellular processes, such as cell proliferation and survival. Here, we reviewed the mechanisms of the STAT3 pathway regulation and their role in promoting melanoma. Also, we have evaluated the emerging data on polyphenols (PPs) specifically their contribution in melanoma therapies with an emphasis on their regulatory/inhibitory actions in relation to STAT3 pathway and current progress in the development of phytochemical therapeutic techniques. An understanding of targeting STAT3 by PPs brings an opportunity to melanoma therapy. © 2016 BioFactors, 43(3):347-370, 2017.

Induction of immunogenic cell death of tumors by newly synthesized heterocyclic quinone derivative

Many cancer types are serious diseases causing mortality, and new therapeutics with improved efficacy and safety are required. Immuno-(cell)-therapy is considered as one of the promising therapeutic strategies for curing intractable cancer. In this study, we tested R2016, a newly developed heterocyclic quinone derivative, for induction of immunogenic tumor cell death and as a possible novel immunochemotherapeutic. We studied the anti-cancer effects of R2016 against LLC, a lung cancer cell line and B16F10, a melanoma cell line. LLC (non-immunogenic) and B16F10 (immunogenic) cells were killed by R2016 in dose-dependent manner. R2016 reduced the viability of both LLC and B16F10 tumor cells by inducing apoptosis and necrosis, while it demonstrated no cytotoxicity against normal splenocytes. Expression of immunogenic death markers on the cell surface of R2016 treated tumor cells including calreticulin (CRT) and heat shock proteins (HSPs) was increased along with the induction of their genes. Increased CRT expression correlated with dendritic cell (DC) uptake of dying tumor cells: the proportion of CRT⁺CD11c⁺cells was increased in the R2016-treated group. The gene transcription of Calr3, Hspb1, and Tnfaip6, which are related to immunogenicity induction of dead cells, was up-regulated in the R2016 treated tumor cells. On the other hand, ANGPT1, FGF7, and URGCP gene levels were down-regulated by R2016 treatment. This data suggests that R2016 induced immunogenic tumor cell death, and suggests R2016 as an effective anti-tumor immunochemotherapeutic modality.

DJ-1 promotes development of DEN-induced hepatocellular carcinoma and proliferation of liver cancer cells

Chronic liver inflammation and injuries play a critical role in development of hepatocellular carcinoma (HCC). Parkinson disease (autosomal recessive, early onset) 7, encoding PARK7 protein (also called DJ-1), plays important roles in many carcinogenesis processes and is essential in modulating inflammation. However, whether DJ-1 is involved in HCC development remains largely unknown. To determine the effect of DJ-1 on HCC development, we accessed the correlation of hepatic DJ-1 expression with overall survival (OS) and TNM stage in 96 HCC patients and found a significant inverse correlation between DJ-1 expression and OS. By adopting a classic diethylnitrosamine (DEN)-induced murine HCC model, DJ-1 knockout (KO) mice displayed reduced tumorigenesis and cell proliferation, accompanied by decreased hepatic inflammation and IL-6/STAT3 activation. Furthermore, after an acute DEN challenge, DJ-1 KO mice showed significant decreases in liver injury, hepatocyte proliferation and DNA damage. In a human HCC cell line (MHCC-97L), cancer cell proliferation was induced by overexpression of DJ-1 and is related to oncogenic signaling of MAPKs and AKT. Induction of DJ-1 may serve as a novel regulator for HCC cell proliferation and HCC development possibly through enhanced MAPK signaling and inflammation.

TGR5, Not Only a Metabolic Regulator

G-protein-coupled bile acid receptor, Gpbar1 (TGR5), is a member of G-protein-coupled receptor (GPCR) superfamily. High levels of TGR5 mRNA were detected in several tissues such as small intestine, stomach, liver, lung, especially in placenta and spleen. TGR5 is not only the receptor for bile acids, but also the receptor for multiple selective synthetic agonists such as 6α-ethyl-23(S)-methyl-cholic acid (6-EMCA, INT-777) and a series of 4-benzofuranyloxynicotinamde derivatives to regulate different signaling pathways such as nuclear factor κB (NF-κB), AKT, and extracellular signal-regulated kinases (ERK). TGR5, as a metabolic regulator, is involved in energy homeostasis, bile acid homeostasis, as well as glucose metabolism. More recently, our group and others have extended the functions of TGR5 to more than metabolic regulation, which include inflammatory response, cancer and liver regeneration. These findings highlight TGR5 as a potential drug target for different diseases. This review summarizes the basic information of TGR5 and its new functions.

MiR-204 silencing in intraepithelial to invasive cutaneous squamous cell carcinoma progression

Background

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer and frequently progresses from an actinic keratosis (AK), a sun-induced keratinocyte intraepithelial neoplasia (KIN). Epigenetic mechanisms involved in the phenomenon of progression from AK to cSCC remain to be elicited.

Methods

Expression of microRNAs in sun-exposed skin, AK and cSCC was analysed by Agilent microarrays. DNA methylation of miR-204 promoter was determined by bisulphite treatment and pyrosequencing. Identification of miR-204 targets and pathways was accomplished in HaCat cells. Immunofluorescence and immunohistochemistry were used to analyze STAT3 activation and PTPN11 expression in human biopsies.

Results

cSCCs display a marked downregulation of miR-204 expression when compared to AK. DNA methylation of miR-204 promoter was identified as one of the repressive mechanisms that accounts for miR-204 silencing in cSCC. In HaCaT cells miR-204 inhibits STAT3 and favours the MAPK signaling pathway, likely acting through PTPN11, a nuclear tyrosine phosphatase that is a direct miR-204 target. In non-peritumoral AK lesions, activated STAT3, as detected by pY705-STAT3 immunofluorescence, is retained in the membrane and cytoplasm compartments, whereas AK lesions adjacent to cSCCs display activated STAT3 in the nuclei.

Conclusions

Our data suggest that miR-204 may act as a “rheostat” that controls the signalling towards the MAPK pathway or the STAT3 pathway in the progression from AK to cSCC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0537-z) contains supplementary material, which is available to authorized users.

Ciclopirox olamine inhibits mTORC1 signaling by activation of AMPK

Ciclopirox olamine (CPX), an off-patent antifungal agent, has recently been identified as a potential anticancer agent. The mammalian target of rapamycin (mTOR) is a central controller of cell growth, proliferation and survival. Little is known about whether and how CPX executes its anticancer action by inhibiting mTOR. Here we show that CPX inhibited the phosphorylation of p70 S6 kinase 1 (S6K1) and eukaryotic initiation factor 4E binding protein 1 (4E-BP1), two downstream effector molecules of mTOR complex 1 (mTORC1), in a spectrum of human tumor cells, indicating that CPX inhibits mTORC1 signaling. Using rhabdomyosarcoma cells as an experimental model, we found that expression of constitutively active mTOR (E2419K) conferred resistance to CPX inhibition of cell proliferation, suggesting that CPX inhibition of mTORC1 contributed to its anticancer effect. In line with this, treatment with CPX inhibited tumor growth and concurrently suppressed mTORC1 signaling in RD xenografts. Mechanistically, CPX inhibition of mTORC1 was neither via inhibition of IGF-I receptor or phosphoinositide 3-kinase (PI3K), nor by activation of phosphatase and tensin homolog (PTEN). Instead, CPX inhibition of mTORC1 was attributed to activation of AMP-activated protein kinase (AMPK)-tuberous sclerosis complexes (TSC)/raptor pathways. This is supported by the findings that CPX activated AMPK; inhibition of AMPK with Compound C or ectopic expression of dominant negative AMPKα partially prevented CPX from inhibiting mTORC1; silencing TSC2 attenuated CPX inhibition of mTORC1; and CPX also increased AMPK-mediated phosphorylation of raptor (S792). Therefore, the results indicate that CPX exerts the anticancer effect by activating AMPK, resulting in inhibition of mTORC1 signaling.

At High Levels, Constitutively Activated STAT3 Induces Apoptosis of Chronic Lymphocytic Leukemia Cells

In chronic lymphocytic leukemia (CLL), the increment in PBLs is slower than the expected increment calculated from the cells' proliferation rate, suggesting that cellular proliferation and apoptosis are concurrent. Exploring this phenomenon, we found overexpression of caspase-3, higher cleaved poly (ADP-ribose) polymerase levels (p < 0.007), and a higher apoptosis rate in cells from patients with high counts compared with cells from patients with low counts. Although we previously found that STAT3 protects CLL cells from apoptosis, STAT3 levels were significantly higher in cells from patients with high counts than in cells from patients with low counts. Furthermore, overexpression of STAT3 did not protect the cells. Rather, it upregulated caspase-3 and induced apoptosis. Remarkably, putative STAT3 binding sites were identified in the caspase-3 promoter, and a luciferase assay, chromatin immunoprecipitation, and an EMSA revealed that STAT3 activated caspase-3 However, caspase-3 levels increased only when STAT3 levels were sufficiently high. Using chromatin immunoprecipitation and EMSA, we found that STAT3 binds with low affinity to the caspase-3 promoter, suggesting that at high levels, STAT3 activates proapoptotic mechanisms and induces apoptosis in CLL cells.

Resistin and interleukin-6 exhibit racially-disparate expression in breast cancer patients, display molecular association and promote growth and aggressiveness of tumor cells through STAT3 activation

African-American (AA) women with breast cancer (BC) are diagnosed with more aggressive disease, have higher risk of recurrence and poorer prognosis as compared to Caucasian American (CA) women. Therefore, it is imperative to define the factors associated with such disparities to reduce the unequal burden of cancer. Emerging data suggest that inherent differences exist in the tumor microenvironment of AA and CA BC patients, however, its molecular bases and functional impact have remained poorly understood. Here, we conducted cytokine profiling in serum samples from AA and CA BC patients and identified resistin and IL-6 to be the most differentially-expressed cytokines with relative greater expression in AA patients. Resistin and IL-6 exhibited positive correlation in serum levels and treatment of BC cells with resistin led to enhanced production of IL-6. Moreover, resistin also enhanced the expression and phosphorylation of STAT3, and treatment of BC cells with IL-6-neutralizing antibody prior to resistin stimulation abolished STAT3 phosphorylation. In addition, resistin promoted growth and aggressiveness of BC cells, and these effects were mediated through STAT3 activation. Together, these findings suggest a crucial role of resistin, IL-6 and STAT3 in BC racial disparity.

Resistance to Anti-VEGF Therapy Mediated by Autocrine IL6/STAT3 Signaling and Overcome by IL6 Blockade

Anti-VEGF therapies benefit several cancer types, but drug resistance that limits therapeutic response can emerge. We generated cell lines from anti-VEGF-resistant tumor xenografts to investigate the mechanisms by which resistance develops. Of all tumor cells tested, only A431 (A431-V) epidermoid carcinoma cells developed partial resistance to the VEGF inhibitor aflibercept. Compared with the parental tumors, A431-V tumors secreted greater amounts of IL6 and exhibited higher levels of phospho-STAT3. Notably, combined blockade of IL6 receptor (IL6R) and VEGF resulted in enhanced activity against A431-V tumors. Similarly, inhibition of IL6R enhanced the antitumor effects of aflibercept in DU145 prostate tumor cells that displays high endogenous IL6R activity. In addition, post hoc stratification of data obtained from a clinical trial investigating aflibercept efficacy in ovarian cancer showed poorer survival in patients with high levels of circulating IL6. These results suggest that the activation of the IL6/STAT3 pathway in tumor cells may provide a survival advantage during anti-VEGF treatment, suggesting its utility as a source of response biomarkers and as a therapeutic target to heighten efficacious results. Cancer Res; 76(8); 2327-39. ©2016 AACR.

Loss-of-Function PTPRD Mutations Lead to Increased STAT3 Activation and Sensitivity to STAT3 Inhibition in Head and Neck Cancer

BACKGROUND

Protein tyrosine phosphatase receptor type D (PTPRD) is a putative tumor suppressor in several cancers including head and neck squamous cell carcinoma (HNSCC). STAT3 is a frequently hyperactivated oncogene in HNSCC. As STAT3 is a direct substrate of PTPRD, we sought to determine the genetic or epigenetic alterations of PTPRD that contribute to overactive STAT3 in HNSCC.

METHODS

We analyzed data from The Cancer Genome Atlas (TCGA) and our previous whole-exome sequencing study and summarized the mutation, methylation, and copy number status of PTPRD in HNSCC and other cancers. In vitro studies involved standard transfection and MTT protocols, as well as methylation-specific PCR.

RESULTS

Our findings indicate that PTPRD mutation, rather than methylation or copy number alteration, is the primary mechanism by which PTPRD function is lost in HNSCC. We demonstrate that overexpression of wild-type PTPRD in HNSCC cells significantly inhibits growth and STAT3 activation while PTPRD mutants do not, suggesting that mutation may lead to loss of function and subsequent hyper-phosphorylation of PTPRD substrates, especially STAT3. Importantly, we determined that HNSCC cells harboring an endogenous PTPRD mutation are more sensitive to STAT3 blockade than PTPRD wild-type cells. We additionally found that PTPRD mRNA expression does not correlate with pSTAT3 expression, suggesting that alterations that manifest through altered mRNA expression, including hypermethylation and gene copy number alterations, do not significantly contribute to STAT3 overactivation in HNSCC.

CONCLUSION

PTPRD mutation, but not methylation or copy number loss, may serve as a predictive biomarker of sensitivity to STAT3 inhibitors in HNSCC.

Single nucleotide polymorphisms of the NF-κB and STAT3 signaling pathway genes predict lung cancer prognosis in a Chinese Han population

Inflammation contributes to human carcinogenesis and cancer progression. This study selected and analyzed single nucleotide polymorphisms (SNPs) of the NF-κB and STAT3 signaling pathway genes for associations with prognosis in 1,165 lung cancer patients from a Chinese Han population. The data showed that eight SNPs (i.e., rs10836, rs3732131, rs3732133, rs4072391, rs2273650, rs1053023, rs3744483, and rs28372683) can be grouped into low-, medium-, and high-risk genotypes based on survival data. The median overall survival time (MST) of this cohort of patients was 24.6 months, whereas the MST of patients with low-risk genotypes reached 79.7 months; MST of patients with the medium-risk genotypes was 25.5 months, and those with high-risk genotypes was 22.7 months. Overall survival was statistically different for sex (P = 0.004), age (P = 0.010), histological types (P = 0.035), tumor stage (P < 0.001), tumor size (P < 0.001), surgery (P < 0.001), chemoradiotherapy (P = 0.007), and Karnofsky score (P < 0.001). Multivariate analysis and the data from the current study demonstrated that sex, tumor stage and size, surgery, chemoradiotherapy, and the aforementioned eight SNPs were all independent predictors for overall survival of lung cancer patients.

Antagonizing STAT3 dimerization with a rhodium(III) complex

Kinetically inert metal complexes have arisen as promising alternatives to existing platinum and ruthenium chemotherapeutics. Reported herein, to our knowledge, is the first example of a substitutionally inert, Group 9 organometallic compound as a direct inhibitor of signal transducer and activator of transcription 3 (STAT3) dimerization. From a series of cyclometalated rhodium(III) and iridium(III) complexes, a rhodium(III) complex emerged as a potent inhibitor of STAT3 that targeted the SH2 domain and inhibited STAT3 phosphorylation and dimerization. Significantly, the complex exhibited potent anti-tumor activities in an in vivo mouse xenograft model of melanoma. This study demonstrates that rhodium complexes may be developed as effective STAT3 inhibitors with potent anti-tumor activity.

New basic approach to treat non-small cell lung cancer based on RNA-interference

BACKGROUND

To date the therapy for non-small cell lung cancer (NSCLC) is associated with severe side effects, frustrating outcomes, and does not consider different tumor characteristics. The RNA-interference (RNAi) pathway represents a potential new approach to treat NSCLC. With small interfering ribonucleic acids (siRNAs), it is possible to reduce the expression of proliferation-dependent proteins in tumor cells, leading to their apoptosis. We propose that siRNAs could be adapted to the tumor type and may cause fewer side effects than current therapy.

METHODS

Four NSCLC cell lines were cultured under standard conditions and transfected with three different concentrations of siRNAs targeted against the hypoxia-inducible factors 1α and 2α (HIF1α and HIF2α) and signal transducer and activator of transcription 3 (STAT3). The expression was observed by quantitative real-time polymerase chain reaction and western blots. For the analysis of cell growth three days after transfection, the cell number was detected using a CASY cell counter system.

RESULTS

The results of the silencing of the analyzed factors differ in each cell line. Cell growth was significantly reduced in all cell lines after transfection with HIF1α- and STAT3-siRNA. The silencing of HIF2α resulted in a significant effect on cell growth in squamous, and large-cell lung cancer.

CONCLUSIONS

This study shows that the knockdown and viability to siRNA transfection differ in each tumor type according to the used siRNA. This implies that the tumor types differ among themselves and should be treated differently. Therefore, the authors suggest a possible approach to a more personalized treatment of NSCLC.

Targeting the STAT3 signaling pathway in cancer: role of synthetic and natural inhibitors

Signal transducers and activators of transcription (STATs) comprise a family of cytoplasmic transcription factors that mediate intracellular signaling that is usually generated at cell surface receptors and thereby transmit it to the nucleus. Numerous studies have demonstrated constitutive activation of STAT3 in a wide variety of human tumors, including hematological malignancies (leukemias, lymphomas, and multiple myeloma) as well as diverse solid tumors (such as head and neck, breast, lung, gastric, hepatocellular, colorectal and prostate cancers). There is strong evidence to suggest that aberrant STAT3 signaling promotes initiation and progression of human cancers by either inhibiting apoptosis or inducing cell proliferation, angiogenesis, invasion, and metastasis. Suppression of STAT3 activation results in the induction of apoptosis in tumor cells, and accordingly its pharmacological modulation by tyrosine kinase inhibitors, antisense oligonucleotides, decoy nucleotides, dominant negative proteins, RNA interference and chemopreventive agents have been employed to suppress the proliferation of various human cancer cells in culture and tumorigenicity in vivo. However, the identification and development of novel drugs that can target deregulated STAT3 activation effectively remains an important scientific and clinical challenge. This review presents the evidence for critical roles of STAT3 in oncogenesis and discusses the potential for development of novel cancer therapies based on mechanistic understanding of STAT3 signaling cascade.

Effects and interactions of MiR-577 and TSGA10 in regulating esophageal squamous cell carcinoma

Testis specific 10 (TSGA10) was originally identified as a testis-specific protein and tumor-associated antigen in a number of cancer types. In this study, we found that down-regulation of TSGA10 was associated with increased malignancy and clinical features of esophageal squamous cell carcinomas (ESCCs). Moreover, increased expression of TSGA10 inhibited, while its knockdown promoted, tumor formation in vivo in nude mice. At the 3'UTR of the TSGA10 gene we identified two binding sites for microRNA-577 (miR-577). Further investigation demonstrated that expression levels of miR-577 and TSGA10 were negatively correlated to each other in ESCC cell lines and tumor samples. Moreover, manipulation of miR-577 and TSGA10 expression confirmed that miR-577 can regulate TSGA10 and in turn affect cell proliferation in vitro. Additionally, with flow cytometry and manipulation of the mir-577/TSGA10 axis, it was found that mir-577/TSGA10 axis influenced the growth of ESCC through regulating the G1-S phase transition. We also obtained evidence to establish that mir-577/TSGA10 axis activation was always accompanied by inactivation of the p53 pathway or the Rb pathway or both, thus, the latter two pathways are obligatory for progression of ESCCs with mir-577/TSGA10 axis activation. In addition, we found that such an interactive pathway in regulating cancer cell proliferation was restricted to a few cancer types including ESCC, but not uniformly applicable to other cancer types. This newly discovered regulatory mechanism provides a new dimension for ESCC diagnosis and therapy.

Loss of has-miR-337-3p expression is associated with lymph node metastasis of human gastric cancer

Background

Metastasis is the major cause of cancer-related death in patients with gastric cancer, and aberrant expression of various microRNAs (miRNAs) is associated with cancer metastasis.

Methods

Profiling of differentially expressed miRNAs was performed in three cases of primary gastric cancer and the corresponding metastatic lymph node tissues. Then, the five most altered miRNAs were further verified in 16 paired samples. Two of these five miRNAs were further assessed for their effects on the regulation of gastric cancer cell growth and invasion.

Results

The miRNA profile data showed 151 upregulated miRNAs (≥ 1.5-fold) and 285 downregulated miRNAs (≤ 0.67-fold) in the metastatic tissues compared to the primary gastric cancer tissues. Among these five miRNAs (i.e., hsa-miR-508-5p, hsa-miR-30c, hsa-miR-337-3p, hsa-miR-483-5p, and hsa-miR-134), expression of hsa-miR-337-3p and hsa-miR-134 was significantly downregulated in these 16 lymph node metastatic tissues compared to their primary tumor tissues (P<0.05) and in nine gastric cancer cell lines compared to the nonmalignant GES cell line. Furthermore, induction of hsa-miR-134 or hsa-miR-337-3p expression did not dramatically affect gastric cancer cell proliferation, but transfection of the hsa-miR-337-3p mimic did reduce gastric cancer cell invasion capacity.

Conclusions

These findings indicate that hsa-miR-337-3p plays a role in the reduction of gastric cancer cell invasion capacity, and further studies on the mechanism of hsa-miR-337-3p in gastric cancer metastasis are warranted.

WITHDRAWN: Intrinsic molecular characteristics of inhibiting STAT3 activation and dimerization through targeting the phosphotyrosine binding site within the SH2 domain-A molecular dynamics study

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Resveratrol induces cell cycle arrest and apoptosis in malignant NK cells via JAK2/STAT3 pathway inhibition

Natural killer (NK) cell malignancies, particularly aggressive NK cell leukaemias and lymphomas, have poor prognoses. Although recent regimens with L-asparaginase substantially improved outcomes, novel therapeutic approaches are still needed to enhance clinical response. Resveratrol, a naturally occurring polyphenol, has been extensively studied for its anti-inflammatory, cardioprotective and anti-cancer activities. In this study, we investigated the potential anti-tumour activities of resveratrol against the NK cell lines KHYG-1, NKL, NK-92 and NK-YS. Resveratrol induced robust G0/G1 cell cycle arrest, significantly suppressed cell proliferation and induced apoptosis in a dose- and time-dependent manner for all four cell lines. In addition, resveratrol suppressed constitutively active STAT3 in all the cell lines and inhibited JAK2 phosphorylation but had no effect on other upstream mediators of STAT3 activation, such as PTEN, TYK2, and JAK1. Resveratrol also induced downregulation of the anti-apoptotic proteins MCL1 and survivin, two downstream effectors of the STAT3 pathway. Finally, resveratrol induced synergistic effect on the apoptotic and antiproliferative activities of L-asparaginase against KHYG-1, NKL and NK-92 cells. These results suggest that resveratrol may have therapeutic potential against NK cell malignancies. Furthermore, our finding that resveratrol is a bonafide JAK2 inhibitor extends its potential benefits to other diseases with dysregulated JAK2 signaling.

Topical curcumin-based cream is equivalent to dietary curcumin in a skin cancer model

Skin squamous cell carcinoma (SCC), the most common cancer in the USA, is a growing problem with the use of tanning booths causing sun-damaged skin. Antiproliferative effects of curcumin were demonstrated in an aggressive skin cancer cell line SRB12-p9 (P < 0.05 compared to control). Topical formulation was as effective as oral curcumin at suppressing tumor growth in a mouse skin cancer model. Curcumin at 15 mg administered by oral, topical, or combined formulation significantly reduced tumor growth compared to control (P = 0.004). Inhibition of pAKT, pS6, p-4EBP1, pSTAT3, and pERK1/2 was noted in SRB12-p9 cells post-curcumin treatment compared to control (P < 0.05). Inhibition of pSTAT3 and pERK1/2 was also noted in curcumin-treated groups in vivo. IHC analysis revealed human tumor specimens that expressed significantly more activated pERK (P = 0.006) and pS6 (P < 0.0001) than normal skin samples. This is the first study to compare topical curcumin to oral curcumin. Our data supports the use of curcumin as a chemopreventive for skin SCC where condemned skin is a significant problem. Prevention strategies offer the best hope of future health care costs in a disease that is increasing in incidence due to increased sun exposure.

Comparative analysis of mesenchymal stem cells from adult mouse adipose, muscle, and fetal muscle

Recently, increasing evidence supports that adult stem cells are the part of a natural system for tissue growth and repair. This study focused on the differences of mesenchymal stem cells from adult adipose (ADSCs), skeletal muscle (MDSCs) and fetal muscle (FMSCs) in biological characteristics, which is the key to cell therapy success. Stem cell antigen 1 (Sca-1) expression of MDSCs and FMSCs at passage 3 was two times more than that at passage 1 (P < 0.0001). After 28-day myogenic induction, higher expression levels of skeletal muscle-specific genes were observed in MDSCs than FMSCs (P < 0.01), and the lowest expression levels were demonstrated in ADSCs among three cells (P < 0.01). Besides, M-Cad and MyHC expressions in ADSCs were not detected by immunofluorescence or real-time quantitative PCR. Furthermore, after 14 days adipogenic induction, PPARγ2, LPL and aP2 mRNA expressions were higher in ADSCs vs. MDSCs (P < 0.01). Besides, MSCs from adult or fetal muscle expressed higher OCN and OPN than ADSCs after 28 days osteogenic induction (P < 0.01). Taken together, our results suggested that cell source and developmental stage had great impacts on biological properties of mesenchymal stem cells, and proper consideration of all the issues is necessary.

STAT3 inhibition, a novel approach to enhancing targeted therapy in human cancers (review)

Signal transducer and activator of transcription 3 (STAT3) regulates many critical functions in human normal and malignant tissues, such as differentiation, proliferation, survival, angiogenesis and immune function. Constitutive activation of STAT3 is implicated in a wide range of human cancers. As such, STAT3 has been studied as a tumour therapeutic target. This review aimed principally to summarise the updated research on STAT3 inhibition studies and their therapeutic potential in solid tumours. Recent literature associated with STAT3 inhibition was reviewed through PubMed and Medline database, followed by critical comparison and analysis. Constitutive activation of STAT3 has been identified as abnormal and oncogenic. The pathway of STAT3 activation and signal transduction identifies 3 approaches for inhibition: modulating upstream positive or negative regulators, regulating RNA (DN-STAT3, anti-sense RNA, siRNA and microRNA) or targeting STAT3 protein at different domains. The last approach using small molecule STAT3 inhibitors has been the most examined so far with both preclinical and clinical studies. Targeting STAT3 using a specific inhibitor may be a useful cancer treatment approach, with the potential for a broad clinical impact.

Effects of the tropical ginger compound,1'-acetoxychavicol acetate, against tumor promotion in K5.Stat3C transgenic mice

The purpose of the current study was to determine whether a tropical ginger derived compound 1'-acetoxychavicol acetate (ACA), suppresses skin tumor promotion in K5.Stat3C mice. In a two-week study in which wild-type (WT) and K5.Stat3C mice were co-treated with either vehicle, ACA, galanga extract, or fluocinolone acetonide (FA) and tetradecanoyl phorbol acetate (TPA), only the galanga extract and FA suppressed TPA-induced skin hyperproliferation and wet weight. None of these agents were effective at suppressing p-Tyr705Stat3 expression. However, ACA and FA showed promising inhibitory effects against skin tumorigenesis in K5.Stat3C mice. ACA also suppressed phospho-p65 NF-κB activation, suggesting a potential mechanism for its action.

STAT3 gene polymorphisms and susceptibility to non-small cell lung cancer

Signal transducer and activator of transcription protein 3 (STAT3) has been implicated in cancer development and is recognized as a type of oncogene. However, association studies of single nucleotide polymorphisms (SNPs) in the STAT3 gene with cancer risk are rare and not available for lung cancer. We examined whether STAT3 polymorphisms are associated with the risk of non-small cell lung cancer (NSCLC). Eight SNPs in the STAT3 gene were genotyped by TaqMan assays in 326 NSCLC cases and 432 controls in a Chinese population. Significant decreased risk of NSCLC was observed for carriers of minor alleles rs4796793 (odds ratio (OR) = 0.68, 95% confidence interval (CI) = 0.51-0.92), rs7211777 (OR = 0.67, 95%CI = 0.50-0.90), rs12949918 (OR = 0.73, 95%CI = 0.54-0.97), rs744166 (OR = 0.69, 95%CI = 0.51-0.92), rs9912773 (OR = 0.75, 95%CI = 0.55-0.98), and rs3869550 (OR = 0.70, 95%CI = 0.53-0.94). The GGCGGC haplotype, comprised of minor alleles of the six NSCLC-associated SNPs, had a 0.78-fold (95%CI = 0.62-0.97) significantly decreased risk of NSCLC, as compared to the most common haplotype of CATACT. Stratification analyses by clinical stage showed that the trend for the association between STAT3 polymorphisms and NSCLC risk was present both for stage I/II and stage III/IV, and appeared moderately stronger for stage III/IV. We conclude that polymorphisms in the STAT3 gene may have a protective role in the development of NSCLC, particular of stage III/IV NSCLC.

HGF/c-met/Stat3 signaling during skin tumor cell invasion: indications for a positive feedback loop

BACKGROUND

Stat3 is a cytokine- and growth factor-inducible transcription factor that regulates cell motility, migration, and invasion under normal and pathological situations, making it a promising target for cancer therapeutics. The hepatocyte growth factor (HGF)/c-met receptor tyrosine kinase signaling pathway is responsible for stimulation of cell motility and invasion, and Stat3 is responsible for at least part of the c-met signal.

METHODS

We have stably transfected a human squamous cell carcinoma (SCC) cell line (SRB12-p9) to force the expression of a dominant negative form of Stat3 (S3DN), which we have previously shown to suppress Stat3 activity. The in vitro and in vivo malignant behavior of the S3DN cells was compared to parental and vector transfected controls.

RESULTS

Suppression of Stat3 activity impaired the ability of the S3DN cells to scatter upon stimulation with HGF (c-met ligand), enhanced their adhesion, and diminished their capacity to invade in vitro and in vivo. Surprisingly, S3DN cells also showed suppressed HGF-induced activation of c-met, and had nearly undetectable basal c-met activity, as revealed by a phospho-specific c-met antibody. In addition, we showed that there is a strong membrane specific localization of phospho-Stat3 in the wild type (WT) and vector transfected control (NEO4) SRB12-p9 cells, which is lost in the S3DN cells. Finally, co-immunoprecipitation experiments revealed that S3DN interfered with Stat3/c-met interaction.

CONCLUSION

These studies are the first confirm that interference with the HGF/c-met/Stat3 signaling pathway can block tumor cell invasion in an in vivo model. We also provide novel evidence for a possible positive feedback loop whereby Stat3 can activate c-met, and we correlate membrane localization of phospho-Stat3 with invasion in vivo.

Squamous carcinoma cells influence monocyte phenotype and suppress lipopolysaccharide-induced TNF-alpha in monocytes

Bacteria and chronic inflammation are present in squamous cell carcinoma of the head and neck (HNSCC), but their roles in the pathogenesis of HNSCC are unclear. Our studies described here revealed that human monocytes co-cultured short term with HNSCC cells were more likely to express CD16, and CD16(+) small mononuclear cells were common in HNSCC specimens. In addition, we identified monocytes as the primary source of LPS-induced IL-6 and TNF-alpha in the monocyte-HNSCC co-cultures. Remarkably, relative to LPS-stimulated monocytes cultured alone, HNSCC cells profoundly suppressed LPS-induced TNF-alpha in monocytes, without compromising IL-6 production. High levels of cytoprotective factors like IL-6 and low levels of TNF-alpha are important for the tumor microenvironment that enables tumor cell survival, affects monocyte differentiation and may contribute to tumor colonization by bacteria. This study provides novel observations that HNSCC cells affect monocyte phenotype and function, which are relevant to the regulation of the HNSCC microenvironment.

Keratinocyte-specific stat3 heterozygosity impairs development of skin tumors in human papillomavirus 8 transgenic mice

Human papillomaviruses (HPV) of the genus β are thought to play a role in human skin cancers, but this has been difficult to establish using epidemiologic approaches. To gain insight into the transforming activities of β-HPV, transgenic mouse models have been generated that develop skin tumors. Recent evidence suggests a central role of signal transducer and activator of transcription 3 (Stat3) as a transcriptional node for cancer cell-autonomous initiation of a tumor-promoting gene signature associated with cell proliferation, cell survival, and angiogenesis. Moreover, high levels of phospho-Stat3 have been detected in tumors arising in HPV8-CER transgenic mice. In this study, we investigate the in vivo role of Stat3 in HPV8-induced skin carcinogenesis by combining our established experimental model of HPV8-induced skin cancer with epidermis-restricted Stat3 ablation. Stat3 heterozygous epidermis was less prone to tumorigenesis than wild-type epidermis. Three of the 23 (13%) Stat3(+/-):HPV8 animals developed tumors within 12 weeks of life, whereas 54.3% of Stat3(+/+):HPV8 mice already exhibited tumors in the same observation period (median age for tumor appearance, 10 weeks). The few tumors that arose in the Stat3(+/-):HPV8 mice were benign and never progressed to a more malignant phenotype. Collectively, these results offer direct evidence of a critical role for Stat3 in HPV8-driven epithelial carcinogenesis. Our findings imply that targeting Stat3 activity in keratinocytes may be a viable strategy to prevent and treat HPV-induced skin cancer.

Dangerous liaisons: STAT3 and NF-kappaB collaboration and crosstalk in cancer

Transcriptional factors of the NF-kappaB family and STAT3 are ubiquitously expressed and control numerous physiological processes including development, differentiation, immunity, metabolism and cancer. Both NF-kappaB and STAT3 are rapidly activated in response to various stimuli including stresses and cytokines, although they are regulated by entirely different signaling mechanisms. Once activated, NF-kappaB and STAT3 control the expression of anti-apoptotic, pro-proliferative and immune response genes. Some of these genes overlap and require transcriptional cooperation between the two factors. The activation of and interaction between STAT3 and NF-kappaB plays a key role in controlling the dialog between the malignant cell and its microenvironment, especially with inflammatory/immune cells that infiltrate tumors. Quite often, cytokines whose expression is induced in response to NF-kappaB in immune cells of the tumor microenvironment lead to STAT3 activation in both malignant and immune cells. While within malignant and pre-malignant cells STAT3 exerts important oncogenic functions, within inflammatory cells it may also suppress tumor promotion through its anti-inflammatory effects. Other interactions and forms of crosstalk between NF-kappaB and STAT3 include physical interaction between the two, cooperation of these factors at gene promoters/enhancers, the NF-kappaB dependent expression of inhibitors of STAT3 activation and the participation of STAT3 in inflammatory cells in the negative regulation NF-kappaB. Despite these versatile and occasionally antagonistic interactions, NF-kappaB and STAT3 cooperate to promote the development and progression of colon, gastric and liver cancers. In addition to explaining the molecular pathogenesis of cancer, these interactions also offer opportunities for the design of new therapeutic interventions.

NF-kappaB mediates the survival of human bronchial epithelial cells exposed to cigarette smoke extract

BACKGROUND

We have previously reported that low concentrations of cigarette smoke extract induce DNA damage without leading to apoptosis or necrosis in human bronchial epithelial cells (HBECs), and that IL-6/STAT3 signaling contributes to the cell survival. Since NF-kappaB is also involved in regulating apoptosis and cell survival, the current study was designed to investigate the role of NF-kappaB in mediating cell survival in response to cigarette smoke exposure in HBECs.

METHODS

Both the pharmacologic inhibitor of NF-kappaB, curcumin, and RNA interference targeting p65 were used to block NF-kappaB signaling in HBECs. Apoptosis and cell survival were then assessed by various methods including COMET assay, LIVE/DEAD Cytotoxicity/Viability assay and colony formation assay.

RESULTS

Cigarette smoke extract (CSE) caused DNA damage and cell cycle arrest in S phase without leading to apoptosis in HBECs as evidenced by TUNEL assay, COMET assay and DNA content assay. CSE stimulated NF-kappaB -DNA binding activity and up-regulated Bcl-XL protein in HBECs. Inhibition of NF-kappaB by the pharmacologic inhibitor curcumin (20 microM) or suppression of p65 by siRNA resulted in a significant increase in cell death in response to cigarette smoke exposure. Furthermore, cells lacking p65 were incapable of forming cellular colonies when these cells were exposed to CSE, while they behaved normally in the regular culture medium.

CONCLUSION

The current study demonstrates that CSE activates NF-kappaB and up-regulates Bcl-XL through NF-kB activation in HBECs, and that CSE induces cell death in cells lacking p65. These results suggest that activation of NF-kappaB regulates cell survival following DNA damage by cigarette smoke in human bronchial epithelial cells.

Interleukin-6 predicts recurrence and survival among head and neck cancer patients

BACKGROUND

Increased pretreatment serum interleukin (IL)-6 levels among patients with head and neck squamous cell carcinoma (HNSCC) have been shown to correlate with poor prognosis, but sample sizes in prior studies have been small and thus unable to control for other known prognostic variables.

METHODS

A longitudinal, prospective cohort study determined the correlation between pretreatment serum IL-6 levels, and tumor recurrence and all-cause survival in a large population (N = 444) of previously untreated HNSCC patients. Control variables included age, sex, smoking, cancer site and stage, and comorbidities. Kaplan-Meier plots and univariate and multivariate Cox proportional hazards models were used to study the association between IL-6 levels, control variables, and time to recurrence and survival.

RESULTS

The median serum IL-6 level was 13 pg/mL (range, 0-453). The 2-year recurrence rate was 35.2% (standard error, 2.67%). The 2-year death rate was 26.5% (standard error, 2.26%). Multivariate analyses showed that serum IL-6 levels independently predicted recurrence at significant levels [hazard ratio (HR) = 1.32; 95% confidence interval (CI), 1.11 to 1.58; P = .002] as did cancer site (oral/sinus). Serum IL-6 level was also a significant independent predictor of poor survival (HR = 1.22; 95% CI, 1.02 to 1.46; P = .03), as were older age, smoking, cancer site (oral/sinus), higher cancer stage, and comorbidities.

CONCLUSIONS

Pretreatment serum IL-6 could be a valuable biomarker for predicting recurrence and overall survival among HNSCC patients. Using IL-6 as a biomarker for recurrence and survival may allow for earlier identification and treatment of disease relapse.

Dedifferentiated liposarcoma with leukocytosis. A case report of G-CSF-producing soft-tissue tumors, possible association with undifferentiated liposarcoma lineage

Background

Granulocyte-colony-stimulating factor (G-CSF) functions as a hematopoietic growth factor and it is responsible for leukocytosis. G-CSF-producing tumors associated with leukocytosis include various types of malignancies.

Case presentation

We report the case of a 72-year-old man with dedifferentiated liposarcoma characterized by dedifferentiated components of malignant fibrous histiocytoma (MFH)-like features in addition to well-differentiated lipoma-like liposarcoma, arising from his upper arm. Preoperative laboratory data showed leukocytosis (103,700/μl). The serum level of G-CSF was also elevated (620 pg/ml [normal, <8 pg/ml]). Nine days after the surgery, the leukocytosis was relieved (WBC; 6,920/μl) and the elevated serum G-CSF level was significantly decreased (G-CSF; 12 pg/ml). One month after the surgery, leukocytosis gradually began to appear again. Three months after the surgery metastatic lung lesions were confirmed, and the patient subsequently died of respiratory problems. In the English literature regarding soft-tissue tumors with leukocytosis, including the current case, we could review a total of 6 cases of liposarcoma with leukocytosis. The subtype of these 6 liposarcoma cases was undifferentiated liposarcoma, comprising dedifferentiated liposarcoma in 4 cases and pleomorphic liposarcoma in 2 cases.

Conclusion

Since the only other soft-tissue tumor that was associated with leukocytosis was MFH, and since MFH is characterized by the absence of any specific differentiation, we would like to propose a possible association between G-CSF-producing soft-tissue tumors and an undifferentiated liposarcoma lineage, such as dedifferentiated liposarcoma or pleomorphic liposarcoma.

Granulocyte colony-stimulating factor/granulocyte colony-stimulating factor receptor biological axis promotes survival and growth of bladder cancer cells

OBJECTIVES

A significant fraction of invasive bladder carcinomas express both granulocyte colony-stimulating factor (G-CSF) and granulocyte colony-stimulating factor receptor (G-CSFR). We sought to determine whether G-CSF/G-CSFR signaling promotes survival and growth of bladder cancer cells. The bladder carcinoma cell line 5637 constitutively secretes G-CSF but lacks G-CSFR expression. In contrast, TCC-SUP lacks expression of both G-CSF and G-CSFR. Using these bladder cancer cell lines as our model systems, we studied the effects of G-CSFR expression on cell proliferation, survival, and growth in vivo.

METHODS

The TCC-SUP and 5637 cells were transiently transfected with either empty vector (3.1) or G-CSFR (GR). Cell proliferation was assessed with or without G-CSF by MTT assay in TCC-SUP-3.1 and TCC-SUP-GR cells. Apoptosis was examined by flow cytometry in 5637-GR with or without anti-G-CSF antibody and in TCC-SUP-GR in the presence of increasing concentrations of G-CSF. We examined the effects of STAT3 (signal transducer and activator of transcription 3) dominant-negative expression on G-CSF/G-CSFR-mediated STAT3 phosphorylation by Western blotting in TCC-SUP-3.1 and TCC-SUP-GR cells. We characterized the effects of STAT3-dominant-negative expression on G-CSF/G-CSFR-mediated survivin expression by flow cytometry in TCC-SUP-3.1 and TCC-SUP-GR cells. We also examined tumor growth using 5637-3.1 and 5637-GR in the nude mice xenograft model.

RESULTS

The G-CSF/G-CSFR loop significantly increased proliferation in TCC-SUP-GR cells. Anti-G-CSF antibody significantly increased apoptosis in serum-starved 5637-GR cells, G-CSF abrogated apoptosis in serum-starved TCC-SUP-GR cells in a dose-dependent manner. STAT3-dominant-negative expression blocked G-CSF-mediated STAT3 phosphorylation and survivin expression in TCC-SUP-GR cells. Furthermore, 5637-GR cells produced a significantly larger tumor in the subcutaneous nude mice xenograft model.

CONCLUSIONS

The G-CSF/G-CSFR autocrine/paracrine signaling loop significantly promotes survival and growth of bladder cancer cells.

Effect of human antisense FXYD6 on the proliferation and invasion of human cholangiocarcinoma cells in vitro

AIM: To investigate the effect of human antisense FXYD6 (FXYD domain containing ion transport regulator 6) on the proliferation and invasion of human cholangiocarcinoma cell line QBC939 in vitro.

METHODS: Human cholangiocarcinoma cell line QBC939 was transfected with the plasmid expressing human antisense FXYD6. Meanwhile, the empty vector and non-transfection group were designed. The mRNA transcription level of hFXYD6 was assayed by real-time reverse transcriptase polymerase chain reaction (RT-PCR) with SYBR Green I, and the expression of hFXYD6 protein was detected by immunohistochemistry. MTT and the colony-forming assay were used to measure the ability of cell growth. The cell cycle distribution was analyzed by flow cytometry and Transwell chamber model was employed to test the ability of cell invasion in vitro.

RESULTS: In comparison with the cells transfected with empty vector or without transfection, QBC939 cells transfected with antisense hFXYD6 had a significant decrease in mRNA transcription and protein expression. The cell doubling time was augmented (46.8 h vs 34.5 h, 35.3 h), whereas the colony formation was decreased (24.3% ± 5.3% vs 61.0% ± 8.5%, 58.0% ± 5.6%; P < 0.001). The G₁-phase cell population was obviously increased (66.4% ± 2.9% vs 33.5% ± 2.3%, 39.4% ± 3.7%, P < 0.001), but the S-phase one was decreased (18.6% ± 1.6% vs 36.2% ± 2.1%, 34.1% ± 1.6%, P < 0.001). The cells moved from the upper chamber into the lower one in Transwell chamber assay had no marked difference. Between the cells without transfection and transfected with empty vector, there were no significant differences in cell doubling time, colony forming ability, cell cycle distribution and the ability of cell invasion in vitro.

CONCLUSION: Transfection of antisense hFXYD6 can inhibit the ability of cell proliferation, but it has no effect on the ability of cell invasion in human cholangiocarcinoma cell line QBC939 in vitro.