NSC 74859-mediated inhibition of STAT3 enhances the anti-proliferative activity of cetuximab in hepatocellular carcinoma

HOXD-AS2-STAT3 feedback loop attenuates sensitivity to temozolomide in glioblastoma

AIMS

Glioblastoma multiforme (GBM) is the deadliest glioma and its resistance to temozolomide (TMZ) remains intractable. Long non-coding RNAs (lncRNAs) play crucial roles in that and this study aimed to investigate underlying mechanism of HOXD-AS2-affected temozolomide sensitivity in glioblastoma.

METHODS

We analyzed and validated the aberrant HOXD-AS2 expression in glioma specimens. Then we explored the function of HOXD-AS2 in vivo and in vitro and a clinical case was also reviewed to examine our findings. We further performed mechanistic experiments to investigate the mechanism of HOXD-AS2 in regulating TMZ sensitivity.

RESULTS

Elevated HOXD-AS2 expression promoted progression and negatively correlated with prognosis of glioma; HOXD-AS2 attenuated temozolomide sensitivity in vitro and in vivo; The clinical case also showed that lower HOXD-AS2 sensitized glioblastoma to temozolomide; STAT3-induced HOXD-AS2 could interact with IGF2BP2 protein to form a complex and sequentially upregulate STAT3 signaling, thus forming a positive feedback loop regulating TMZ sensitivity in glioblastoma.

CONCLUSION

Our study elucidated the crucial role of the HOXD-AS2-STAT3 positive feedback loop in regulating TMZ sensitivity, suggesting that this could be provided as a potential therapeutic candidate of glioblastoma.

Deciphering STAT3 signaling potential in hepatocellular carcinoma: tumorigenesis, treatment resistance, and pharmacological significance

Hepatocellular carcinoma (HCC) is considered one of the greatest challenges to human life and is the most common form of liver cancer. Treatment of HCC depends on chemotherapy, radiotherapy, surgery, and immunotherapy, all of which have their own drawbacks, and patients may develop resistance to these therapies due to the aggressive behavior of HCC cells. New and effective therapies for HCC can be developed by targeting molecular signaling pathways. The expression of signal transducer and activator of transcription 3 (STAT3) in human cancer cells changes, and during cancer progression, the expression tends to increase. After induction of STAT3 signaling by growth factors and cytokines, STAT3 is phosphorylated and translocated to the nucleus to regulate cancer progression. The concept of the current review revolves around the expression and phosphorylation status of STAT3 in HCC, and studies show that the expression of STAT3 is high during the progression of HCC. This review addresses the function of STAT3 as an oncogenic factor in HCC, as STAT3 is able to prevent apoptosis and thus promote the progression of HCC. Moreover, STAT3 regulates both survival- and death-inducing autophagy in HCC and promotes cancer metastasis by inducing the epithelial-mesenchymal transition (EMT). In addition, upregulation of STAT3 is associated with the occurrence of chemoresistance and radioresistance in HCC. Specifically, non-protein-coding transcripts regulate STAT3 signaling in HCC, and their inhibition by antitumor agents may affect tumor progression. In this review, all these topics are discussed in detail to provide further insight into the role of STAT3 in tumorigenesis, treatment resistance, and pharmacological regulation of HCC.

Overcoming Acquired Drug Resistance to Cancer Therapies through Targeted STAT3 Inhibition

Anti-neoplastic agents for cancer treatment utilize many different mechanisms of action and, when combined, can result in potent inhibition of cancer growth. Combination therapies can result in long-term, durable remission or even cure; however, too many times, these anti-neoplastic agents lose their efficacy due to the development of acquired drug resistance (ADR). In this review, we evaluate the scientific and medical literature that elucidate STAT3-mediated mechanisms of resistance to cancer therapeutics. Herein, we have found that at least 24 different anti-neoplastic agents-standard toxic chemotherapeutic agents, targeted kinase inhibitors, anti-hormonal agents, and monoclonal antibodies-that utilize the STAT3 signaling pathway as one mechanism of developing therapeutic resistance. Targeting STAT3, in combination with existing anti-neoplastic agents, may prove to be a successful therapeutic strategy to either prevent or even overcome ADR to standard and novel cancer therapies.

Research Progresses of Targeted Therapy and Immunotherapy for Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide, with nearly one million new cases and deaths every year. Owing to the complex pathogenesis, hidden early symptoms, rapidly developing processes, and poor prognosis, the morbidity and mortality of HCC are increasing yearly. With the progress being made in modern medicine, the treatment of HCC is no longer limited to traditional methods. Targeted therapy and immunotherapy have emerged to treat advanced and metastatic HCC in recent years. Since Sorafenib is the first molecular targeting drug against angiogenesis, targeted drugs for HCC are continually emerging. Moreover, immunotherapy plays a vital role in clinical trials. In particular, the application of immune checkpoint inhibitors, which have received increasing attention in the field of cancer treatment, is a possible research path. Interestingly, these two therapies generally complement each other at some stages of HCC, bringing new hope for patients with advanced HCC. In this paper, we discuss the research progress of targeted therapy and immunotherapy for HCC in recent years, which will provide a reference for the further development of drugs for HCC.

A 2-Benzylmalonate Derivative as STAT3 Inhibitor Suppresses Tumor Growth in Hepatocellular Carcinoma by Upregulating β-TrCP E3 Ubiquitin Ligase

The aberrant activation of a signal transducer and activator of transcription 3 (STAT3) restrains type I interferon (IFN) α/β-induced antiviral responses and is associated with the development of cancer. Designing specific STAT3 inhibitors will thus provide new options for use as IFN therapy. Herein, we identified a novel small molecule, dimethyl 2-(4-(2-(methyl(phenyl(p-tolyl)methyl)amino)ethoxy)benzyl)malonate (CIB-6), which can inhibit the IFN-α-induced interferon stimulated response element (ISRE) luciferase reporter (IC₅₀ value = 6.4 μM) and potentiate the antiproliferative effect of IFN-α in human hepatocellular carcinoma (HCC) cells. CIB-6 was found to bind to the STAT3 Src homology 2 (SH2) domain, thereby selectively inhibiting STAT3 phosphorylation without affecting Janus kinases and STAT1/2. CIB-6 also inhibited the migration and invasion of HCC cells by inhibiting the epithelial-mesenchymal transition (EMT) process. Mechanistically, CIB-6 reduced the expression of β-catenin (an EMT key protein) via upregulating β-transducin repeat-containing protein (β-TrCP) and curbed nuclear factor kappa-B (NF-κB) activation through restricting the phosphorylation of the inhibitor of NF-κB (IκB) kinase (IKK) via STAT3 inhibition. Treatment with CIB-6 significantly retarded tumor growth in nude mice with SK-HEP-1 xenografts. In addition, clinical sample analysis revealed that lower β-TrCP and higher β-catenin expression could affect the median survival time of HCC patients. Our findings suggest that CIB-6 could be a new therapeutic strategy for HCC therapy through STAT3-mediated β-TrCP/β-catenin/NF-κB axis.

LIMK1 nuclear translocation promotes hepatocellular carcinoma progression by increasing p-ERK nuclear shuttling and by activating c-Myc signalling upon EGF stimulation

LIM kinase 1 (LIMK1) is a serine/threonine and tyrosine kinase that is predominantly located in the cytoplasm. In our study, nuclear translocation of LIMK1 in clinical hepatocellular carcinoma (HCC) samples was demonstrated for the first time, especially in samples from those with intravascular tumour thrombus. LIMK1 was overexpressed in HCC tissues, and nuclear LIMK1 expression was associated with poor prognosis in HCC patients. Although the effects of cytoplasmic LIMK1 on cofilin phosphorylation and actin filament dynamics have been well studied, the function of nuclear LIMK1 is still unclear. Gain- and loss-of-function experiments were performed both in vitro and in vivo and demonstrated a correlation between nuclear LIMK1 and the enhanced aggressive phenotype of HCC. EGF could drive the nuclear translocation of LIMK1 by activating the interaction of p-ERK and LIMK1 and facilitating their roles in nuclear shuttling. Moreover, nuclear LIMK1 could directly bind to the promoter region of c-Myc and stimulate c-Myc transcription. Although the EGFR monoclonal antibody cetuximab has a poor therapeutic effect on advanced HCC patients, in vivo animal study showed that cetuximab achieved a significant inhibitory effect on the progression of nuclear LIMK1-overexpressing HCC cells. In addition, recent data have demonstrated the potential of cetuximab in combination therapy for HCC patients with LIMK1 nuclear translocation.

Neobavaisoflavone demonstrates valid antitumor effects in Non-Small-Cell Lung Cancer by inhibiting STAT3

AIM AND OBJECTIVE

Lung cancer is the most common cancer which contributes to the majority of death caused by cancer where non-small-cell lung cancer (NSCLC) accounts for approximately 85%. To treat NSCLC, STAT3 has been identified as a target with therapeutic potential. The neobavaisoflavone (NBIF) is one of the flavonoids of traditional Chinese medicine Psoralea corylifolial.

MATERIALS AND METHODS

Human NSCLC cell lines, PC-9, H460 and A549, were applied to determine NBIF's antiproliferative effects through cell viability and colony formation detection. The effect of NBIF on cell apoptosis was determined through Flow cytometry-based assay. Western blotting was used in this study to confirm the levels of P-STAT3 and Bcl-2 and Bax which are apoptotic proteins.

RESULTS

It was observed that NBIF could decrease the cell viability and migration and induce apoptosis in human NSCLC cell lines dose-dependently. Levels of P-STAT3, as well as the downstream signals of STAT3 pathway, were downregulated, suggesting that the tumor-suppression effects of NBIF might be related to the inhibition of STAT3 signaling. Furthermore, NBIF could contribute to the upregulation of BAX and downregulation of BCL2.

CONCLUSION

NBIF might perform the anti-NSCLC efficacy as a result of the inhibition on STAT3 pathway. Besides, our work suggests that NBIF could provide therapeutic alternatives for NSCLC.

Cetuximab and epirubicin HCl-combined application as a possibility to treat both parental and epirubicin HCl-resistant liver cancer cells

BACKGROUND AND AIMS

Targeted chemotherapeutics such as cetuximab can cause many side effects such as skin toxicity when used in high concentrations. In addition, cancer cells can develop resistance to some of the anticancer agents during treatment. The lack of the desired success in chemotherapy and the development of resistance to chemotherapeutics, such as epirubicin HCl, suggest that there is a need for combined therapies. The combination of targeted chemotherapeutics and conventional chemotherapy drugs may lead to the emergence of new strategies in the treatment of cancer. In this study, cytotoxic, antiproliferative, cell cycle inhibitive, oxidative stress generation, and apoptotic effects and effect mechanisms of cetuximab alone and together with epirubicin HCl on parental liver cancer cells (P-Hep G2) and epirubicin HCl-resistant liver cancer cells (R-Hep G2) were investigated.

MATERIALS

Cytotoxic effects of cetuximab alone and with epirubicin-HCl on cells were determined by Cell Titer-Blue® Cell Viability and Lactate Dehydrogenase Activity tests. Cell cycle distributions and apoptosis were detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Cetuximab with epirubicin HCl treatment increased the cytotoxic effect on both cells. Caspase-3/7 activity increased 3 and 1.5 times in comparison with control group in P-Hep G2 and R-Hep G2 cells, respectively, after treating with cetuximab alone, whereas the increase was found to be approximately 4.7 and 2.5 times when cetuximab was treated with epirubicin HCl in P-Hep G2 and R-Hep G2 cells, respectively. Both cetuximab alone and together with epirubicin HCl treatments caused increases in Bax/Bcl-2 ratio in both cells.

DISCUSSION

Treatment of cetuximab with epirubicin HCl to P-Hep G2 and R-Hep G2 cells was found to be more effective in cytotoxic effect and inducing apoptosis comparison to cetuximab alone treatment. In addition, combination treatment showed different effects on pro-apoptotic/anti-apoptotic genes expression according to cells drug resistance properties.

Evaluation of the STAT3 inhibitor GLG‑302 for the prevention of estrogen receptor‑positive and ‑negative mammary cancers

Signal transducer and activator of transcription 3 (STAT3) plays a key role in the transformation of normal cells to cancerous cells. Although inhibitors of STAT3 have been shown to suppress the growth of multiple cancer types in vitro and in vivo, such agents are of particular interest for the prevention of breast cancer, which affects over 200,000 women and claims more than 40,000 lives in the United States each year. In the present study, we employed the MMTV/Neu transgenic mouse model, which develops estrogen receptor (ER)‑negative, Neu‑overexpressing tumors, and the Sprague‑Dawley (SD) rat model, which develops ER‑positive tumors upon exposure to the carcinogen 7,12‑dimethylbenz[a]anthracene (DMBA), to test the efficacy of the STAT3 inhibitor GLG‑302 in the prevention of mammary cancer. Orally administered GLG‑302 and its trizma salt derivative reduced mammary cancer incidence, multiplicity, and tumor weights in female MMTV/Neu mice, and GLG‑302 reduced tumor multiplicity and weights in female DMBA‑treated rats. Consistent with the mechanism of action of STAT3 inhibitors, the reductions in mammary tumors were correlated with decreases in STAT3 phosphorylation and cell proliferation. These data suggest that GLG‑302 is a novel agent with potential for prevention of mammary cancer and support the further development of STAT3 inhibitors for this cause.

BP‑1‑102 exerts an antitumor effect on the AGS human gastric cancer cell line through modulating the STAT3 and MAPK signaling pathways

BP-1-102, a novel inhibitor of signal transducer and activator of transcription 3 (STAT3), exhibits significant antitumor effects in several malignancies in vitro and in vivo. However, its role in gastric cancer (GC) remains to be elucidated. In the present study, the effect and potential molecular mechanisms of BP-102 in human GC cell lines were investigated. The results showed that BP-1-02 dose-dependently inhibited the proliferation of AGS cells, whereas it had little effect on HGC-27 cells. Flow cytometric analysis indicated that BP-1-102 induced apoptosis, but had minimal effect on cell cycle distribution. In addition, cells treated with BP-1-102 demonstrated markedly suppressed migration and invasion capacities. Western blot analysis revealed that BP-1-102 inhibited the phosphorylation of STAT3 and its target genes, including c-Myc, cyclin D1 and survivin, in a time- and dose-dependent manner. Furthermore, it was found that BP-1-102 induced the phosphorylation of c-Jun N-terminal kinase and p38 mitogen-activated protein kinase (MAPK) and inhibited the activation of extracellular signal-related kinases. Taken together, these results demonstrated that BP-1-102 may be a potent antitumor agent that acts through modulating the STAT3 and MAPK signaling pathways in GC cells.

Rhein sensitizes human pancreatic cancer cells to EGFR inhibitors by inhibiting STAT3 pathway

Background

Rhein is a lipophilic anthraquinone extensively found in medicinal herbs. Emerging evidence suggests that rhein has significant antitumor effects, supporting its potential use as an antitumor agent. The IL6/STAT3 signaling pathway has been suggested as an attractive target for the discovery of novel cancer therapeutics.

Methods

The human pancreatic cancer cell lines AsPC-1, Patu8988T, BxPC-3 and PANC-1, and immunodeficient mice were chosen as models to study the effects of rhein. The potent antiproliferative and proapoptotic effects of rhein were examined by cell viability, cellular morphology, apoptosis and colony formation assays. The STAT3 luciferase report assay, immunostaining analysis and Western blot analysis revealed the inhibition of the IL6/STAT3 signaling axis.

Results

Apoptosis was induced by adjunctive use of rhein with epidermal growth factor receptor (EGFR) inhibitors in pancreatic cancer cells as verified by cell apoptosis analysis and changes in the expression level of apoptotic/anti-apoptotic proteins BCL-2, BAX, Caspase 3 and Cl-PARP. Suppression of the phosphorylation of STAT3 and EGFR were also observed as a result of the treatment with a combination of rhein and EGFR inhibitors. Most interestingly, it was found that rhein considerably sensitized cells to erlotinib, thus suppressing tumor growth in PANC-1 and BxPC-3 xenograft models. The in vivo anti-tumor effect was associated with increased apoptosis and combined inhibition of the STAT3 and EGFR pathways in tumor remnants.

Conclusions

Rhein sensitizes human pancreatic cancer cells to EGFR inhibitors through inhibition of STAT3. Taken together, the results indicate that rhein offers a novel blueprint for pancreatic cancer therapy, particularly when combined with EGFR inhibitors.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-1015-9) contains supplementary material, which is available to authorized users.

MicroRNA-9 enhances sensitivity to cetuximab in epithelial phenotype hepatocellular carcinoma cells through regulation of the eukaryotic translation initiation factor 5A-2

Hepatocellular carcinoma (HCC) is one of the most widespread malignant human tumors worldwide. Treatment options include radiotherapy, surgical intervention and chemotherapy; however, drug resistance is an ongoing treatment concern. In the present study, the effects of a microRNA (miR/miRNA), miR-9, on the sensitivity of HCC cell lines to the epidermal growth factor receptor inhibitor, cetuximab, were examined. miR-9 has been proposed to serve a role in tumorigenesis and tumor progression. In the present study, bioinformatics analyses identified the eukaryotic translation initiation factor 5A2 (eIF-5A-2) as a target of miR-9. The expression levels of miR-9 and eIF-5A-2 were examined by reverse transcription-quantitative polymerase chain reaction and HCC cell lines were transfected with miR-9 mimics and inhibitors to determine the effects of the miRNA on cell proliferation and viability. The miR-9 mimic was revealed to significantly increase the sensitivity of epithelial phenotype HCC cells (Hep3B and Huh7) to cetuximab, while the miR-9 inhibitor triggered the opposite effect. There were no significant differences in sensitivity to cetuximab observed in mesenchymal phenotype HCC cells (SNU387 and SNU449). Cells lines displaying high expression levels of eIF-5A-2 were more resistant to cetuximab. Transfection of cells with a miR-9 mimic resulted in downregulation of the expression of eIF-5A-2 mRNA, while an miR-9 inhibitor increased expression. When expression of eIF-5A-2 was knocked down with siRNA, the effects of miR-9 on cetuximab sensitivity were no longer observed. Taken together, these data support a role for miR-9 in enhancing the sensitivity of epithelial phenotype HCC cells to cetuximab through regulation of eIF-5A-2.

STAT3 signaling mediates tumour resistance to EGFR targeted therapeutics

Several EGFR inhibitors are currently undergoing clinical assessment or are approved for the clinical management of patients with varying tumour types. However, treatment often results in a lack of response in many patients. The majority of patients that initially respond eventually present with tumours that display acquired resistance to the original therapy. A large number of receptor tyrosine and intracellular kinases have been implicated in driving signaling that mediates this tumour resistance to anti-EGFR targeted therapy, and in a few cases these discoveries have led to overall changes in prospective tumour screening and clinical practice (K-RAS in mCRC and EGFR T790M in NSCLC). In this mini-review, we specifically focus on the role of the STAT3 signaling axis in providing both intrinsic and acquired resistance to inhibitors of the EGFR. We also focus on STAT3 pathway targeting in an attempt to overcome resistance to anti-EGFR therapeutics.

Let-7a enhances the sensitivity of hepatocellular carcinoma cells to cetuximab by regulating STAT3 expression

Background

Let-7 miRNAs are reported to play an inhibitory role in carcinogenesis, tumor progression, recurrence, and pluripotency of cancer. However, few studies have reported the relationship between let-7 and drug sensitivity, especially for let-7a (a subtype of let-7). This study aimed to investigate the function of let-7a in regulating the sensitivity of hepatocellular carcinoma (HCC) cell lines to cetuximab.

Methods

The cytotoxicity of cetuximab on HCC cell lines (Huh7, Hep3B, HepG2, SNU449, and SNU387) was evaluated using a cell viability assay (the Cell Counting Kit-8 assay) and a cell proliferation assay (the Click-iT EdU Imaging Kit) in the presence of a control, a let-7a mimic, and a let-7a inhibitor. Small interfering RNA to knockdown the expression of signal transducer and activator of transcription 3 (STAT3) were employed. Protein and mRNA expression levels were determined using quantitative polymerase chain reaction and Western blot analysis.

Results

It was found that let-7a enhances the sensitivity of HCC cells with an epithelial phenotype (Huh7, Hep3B, and HepG2) to cetuximab, but has no effect on cells with the mesenchymal phenotype (SNU449 and SNU387). It was determined that STAT3 was a target mRNA of let-7a using TargetScan. Expression of STAT3 and let-7a mRNA were negatively correlated in HCC cell lines. Moreover, let-7a altered the protein and mRNA expression of STAT3. Furthermore, STAT3 knockdown enhanced the function of cetuximab on HCC cell lines with epithelial phenotypes, but not on HCC cell lines with mesenchymal phenotypes. Finally, a rescue experiment confirmed that let-7a affected the sensitivity of HCC cell lines to cetuximab by interacting with STAT3.

Conclusions

There is a functional link between let-7a and STAT3 in enhancing the sensitivity of HCC cells with an epithelial phenotype to cetuximab. Our results provide novel insight into new methodologies for combating HCC drug resistance.

Mechanistic insight into the norepinephrine-induced fibrosis in systemic sclerosis

Raynaud’s phenomenon is frequently observed in systemic sclerosis (SSc) patients, and cold- or stress-induced norepinephrine (NE) has been speculated to be associated with vasoconstriction. Objective was to elucidate the role of NE in fibrosis in SSc. IL-6 is a potent stimulator of collagen production in fibroblasts. NE enhanced IL-6 production and proliferation more significantly in SSc fibroblasts than in normal fibroblasts. Furthermore, the production of IL-6 and phosphorylation of p38 in SSc fibroblasts was enhanced by adrenergic receptor (AR)β agonist, isoproterenol, but not ARα agonist, oxymetazoline. ARβ blocker, propranolol, inhibited NE-induced IL-6 production and phosphorylation of p38 in SSc fibroblasts. NE-induced IL-6 was significantly inhibited by p38 inhibitor, SB203580, suggesting that NE-induced phosphorylation of p38 via ARβ enhances IL-6 production in SSc fibroblasts. NE-induced phosphorylation of ERK1/2 via ARα inhibited IL-6 production in SSc fibroblasts. Combined treatment with NE and endothelin-1 resulted in an additive increase in IL-6 production in SSc fibroblasts. NE-induced IL-6/IL-6 receptor trans-signaling increased the production of collagen type I in SSc fibroblasts, and both propranolol and SB203580 inhibited NE-induced collagen production. These results suggest that cold exposure and/or emotional stress-induced NE might contribute to the skin fibrosis via potentiation of IL-6 production from fibroblasts in SSc.

Proteomic level changes associated with S3I201 treated U87 glioma cells

Glioblastoma multiforme is Grade IV brain tumor associated with high mortality and limited therapeutics. Signal Transducer and Activator of Transcription 3 (STAT3) is persistently active in several cancers including gliomas, and plays a major role in disease progression and survival of glioma patients, thus being a potential therapeutic target for treatment. S3I201 and its analogs inhibit the transcriptional functions of STAT3 and reduce growth of tumor tissues. Here we have studied proteomic alteration associated with S3I201 treated U87 cells using 2-DE and Isobaric tags for relative and absolute quantitation coupled with mass spectrometry. This analysis revealed 136 differentially expressed proteins which were functionally classified with gene ontology analysis. Results showed metabolism, apoptosis, cytoskeletal behaviour, cell redox homeostasis and immune response as the most affected biological processes on S3I201 treatment. Apoptosis-inducing factor 1 mitochondrial, cyclophilin A and chloride intra-cellular channel protein 1 were found to be up-regulated which possibly contributes to its anti-tumorigenic function. Several glycolytic enzymes like phosphoglycerate mutase 1 were also found to be up-regulated and its expression was validated using immunoblot. Conclusively, our study shows the downstream effects of S3I201 in U87 glioma cells and suggests its therapeutic potential.

SIGNIFICANCE

Gliomas with constitutive expression can be treated with STAT3 inhibitors. S3I201, a STAT3 inhibitor, reduces the growth of glioma cells thus could be studied further for its application as anti-glioma agent. This study investigated proteomic alteration associated with S3I201 in U87 cells using complementary proteomic approaches, and our findings suggest that S3I201 influences central metabolism, apoptosis, cytoskeletal behaviour, cell redox homeostasis and immune response as the most affected biological processes which altogether contribute to its anti-tumorigenic activity. Several proteins were identified which may serve as prognostic or predictive markers in GBM. Apoptosis-inducing factor 1 mitochondrial and cyclophilin A were identified as potential therapeutic targets and further investigations on these candidates may facilitate therapeutic development and suggests that GBM therapy can be improved by targeting cellular metabolism and by using immunotherapy.

Zoledronic acid increases the antitumor effect of gefitinib treatment for non-small cell lung cancer with EGFR mutations

Non-small cell lung cancer (NSCLC) patients with epithelial growth factor receptor (EGFR) mutations and bone metastases are often concurrently administered tyrosine kinase inhibitors (TKIs) and bisphosphonates. Yet, the effects and mechanisms of these agents are unclear. In the present study, we aimed to ascertain whether zoledronic acid (ZA) increases the antitumor effects of gefitinib treatment on NSCLC with EGFR mutations and the related mechanisms of action. The effects of ZA and gefitinib on NSCLC tumor cells with EGFR mutations (HCC827, HCC827 GR and H1975) in regards to proliferation, apoptosis, cell cycle and signaling pathways were detected. ZA increased the antitumor effects of gefitinib on NSCLC with EGFR activating mutations and TKI resistance in vitro. Gefitinib caused cell cycle arrest in the G0/G1 phase, ZA induced S phase accumulation and the effect of the combined treatment was neutralization. Combined treatment obviously inhibited STAT3 and/or p‑STAT3 protein expression compared with treatment with each single drug in vitro and in vivo, and it also significantly inhibited TKI resistance NSCLC tumor growth in vivo. In conclusion, ZA increased the antitumor effects of gefitinib on NSCLC with EGFR activating mutations and TKI resistance by regulating the cell cycle, inducing caspase-3 expression and inhibiting STAT3 expression.

IL-6/STAT3 signaling in mice with dysfunctional type-2 ryanodine receptor

Mice with genetically modified cardiac ryanodine receptor (Ryr2^ADA/ADA mice) are impaired in regulation by calmodulin, develop severe cardiac hypertrophy and die about 2 weeks after birth. We hypothesized that the interleukin 6 (IL-6)/signal transducer and activator of transcription-3 (STAT3) signaling pathway has a role in the development of the Ryr2^ADA/ADA cardiac hypertrophy phenotype, and determined cardiac function and protein levels of IL-6, phosphorylation levels of STAT3, and downstream targets c-Fos and c-Myc in wild-type and RyR2^ADA/ADA mice, mice with a disrupted IL-6 gene, and mice treated with STAT3 inhibitor NSC74859. IL-6 protein levels were increased at postnatal day 1 but not day 10, whereas pSTAT3-Tyr705/STAT3 ratio and c-Fos and c-Myc protein levels increased in hearts of 10-day but not 1-day old Ryr2^ADA/ADA mice compared with wild type. Both STAT3 and pSTAT3-Tyr705 accumulated in the nuclear fraction of 10-day old Ryr2^ADA/ADA mice compared with wild type. Ryr2^{ADA /ADA} /IL-6^−/− mice lived 1.5 times longer, had decreased heart to body weight ratio, and reduced c-Fos and c-Myc protein levels. The STAT3 inhibitor NSC74859 prolonged life span by 1.3-fold, decreased heart to body weight ratio, increased cardiac performance, and decreased pSTAT-Tyr705/STAT3 ratio and IL-6, c-Fos and c-Myc protein levels of Ryr2^{ADA /ADA} mice. The results suggest that upregulation of IL-6 and STAT3 signaling contributes to cardiac hypertrophy and early death of mice with a dysfunctional ryanodine receptor. They further suggest that STAT3 inhibitors may be clinically useful agents in patients with altered Ca²⁺ handling in the heart.

Feedback Activation of STAT3 as a Cancer Drug-Resistance Mechanism

Signal transducer and activator of transcription 3 (STAT3) plays crucial roles in several cellular processes such as cell proliferation and survival, and has been found to be aberrantly activated in many cancers. Much research has explored the leading mechanisms for regulating the STAT3 pathway and its role in promoting tumorigenesis. We focus here on recent evidence suggesting that feedback activation of STAT3 plays a prominent role in mediating drug resistance to a broad spectrum of targeted cancer therapies and chemotherapies. We highlight the potential of co-targeting STAT3 and its primary target to overcome drug resistance, and provide perspective on repurposing clinically approved drugs as STAT3 pathway inhibitors, in combination with the FDA-approved receptor tyrosine kinase (RTK) inhibitors, to improve clinical outcome of cancer treatment.

Expression of activated signal transducer and activator of transcription-3 as a predictive and prognostic marker in advanced esophageal squamous cell carcinoma

BACKGROUND

Signal transducer and activator of transcription-3 (STAT3) is an oncogenic transcription factor constitutively active and aberrantly expressed in various types of malignancies, and the expression of p-STAT3 has been recognized as a predictor of poor survival. It remains unclear how variations in p-STAT3 expression influence clinical outcomes in esophageal squamous cell carcinoma (ESCC).

METHODS

Between 1 January 2008 and 1 November 2013, 153 advanced esophageal squamous cell carcinoma patients (stage IV) from two cancer centers in West China were treated with paclitaxel and cisplatin. We retrospectively analyzed the clinical outcomes of patients with ESCC and examined the correlation between p-STAT3 levels and clinical outcomes in esophageal cancer patients.

RESULTS

Among the 153 patients, positive p-STAT3 expression was observed in 73 of 153 (47.7 %) cases. The median PFS for patients with positive expression of p-STAT3 and negative expression of p-STAT3 was 5.0 months and 6.9 months, respectively (P < 0.001). The median overall survival was significantly higher in patients with p-STAT3 negative tumors than in those with p-STAT3 positive tumors (9.9 vs 8.9 months, P = 0.026). Kaplan-Meier survival analysis showed that p-STAT3 expression was statistically indicative of a poor prognosis for progression-free survival.

CONCLUSIONS

These data showed that p-STAT3 expression was significantly associated with poor prognosis in patients with esophageal cancer and could be used as a predictive and prognostic marker in esophageal cancer.

Nuclear PKM2 contributes to gefitinib resistance via upregulation of STAT3 activation in colorectal cancer

Gefitinib (Iressa, ZD-1839), a small molecule tyrosine kinase inhibitor (TKI) of the epidermal growth factor receptor (EGFR) pathway, is currently under investigation in clinical trials for the treatment of colorectal cancer (CRC). However, as known, some patients develop resistance to TKIs, and the mechanisms mediating intrinsic resistance to EGFR-TKIs in CRC have not been fully characterized. Resistance to EGFR inhibitors reportedly involves activation of signal transducer and activator of transcription 3 (STAT3) in glioma and lung cancer. Here, we demonstrated that the nuclear pyruvate kinase isoform M2 (PKM2) levels were positively correlated with gefitinib resistance in CRC cells. The overexpression of nuclear PKM2 in HT29 cells decreased the effect of gefitinib therapy, whereas PKM2 knockdown increased gefitinib efficacy. Furthermore, the activation of STAT3 by nuclear PKM2 was associated with gefitinib resistance. Inhibition of STAT3 by Stattic, a STAT3-specific inhibitor, or STAT3-specific siRNA sensitized resistant cells to gefitinib. These results suggest that nuclear PKM2 modulates the sensitivity of CRC cells to gefitinib and indicate that small molecule pharmacological disruption of nuclear PKM2 association with STAT3 is a potential avenue for overcoming EGFR-TKI resistance in CRC patients.

STAT3 inhibition reduces toxicity of oncolytic VSV and provides a potentially synergistic combination therapy for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a refractory malignancy with a high mortality and increasing worldwide incidence rates, including the United States and central Europe. In this study, we demonstrate that a specific inhibitor of signal transducer and activator of transcription 3 (STAT3), NSC74859, efficiently reduces HCC cell proliferation and can be successfully combined with oncolytic virotherapy using vesicular stomatitis virus (VSV). The potential benefits of this combination treatment are strengthened by the ability of NSC74859 to protect primary hepatocytes and nervous system cells against virus-induced cytotoxicity, with an elevation of the VSV maximum tolerated dose in mice. Hereby we propose a strategy for improving the current regimen for HCC treatment and seek to further explore the molecular mechanisms underlying selective oncolytic specificity of VSV.

STAT3 inhibitor NSC74859 radiosensitizes esophageal cancer via the downregulation of HIF-1α

Radiotherapy is the main therapy for inoperable and locally advanced esophageal squamous cell carcinoma (ESCC). However, radioresistance in ESCC remains a challenge. The aim of this study is to investigate the radiosensitizing effects of STAT3 inhibitor NSC74859 on ESCC and explore the underlying mechanisms. ECA109 and TE13 cells were exposed to hypoxia, and treated with NSC74859 or radiation, alone or in combination. Cell proliferation, survival, apoptosis, and double-stranded DNA breaks (DSBs) were examined. Nude mice model of ECA109 xenograft was treated with radiation and/or NSC74859. The levels of STAT3, p-STAT3, HIF-1α, and VEGF were detected by Western blot analysis. NSC74859 efficiently radiosensitized ESCC cells and xenografts in nude mice, and inhibited hypoxia-/radiation-induced activation of STAT3 and upregulation of HIF-1α and VEGF expression. NSC74859 confers radiosensitivity in ESCC via the inhibition of STAT3 activation and the downregulation of HIF-1α and VEGF expression. NSC74859 may become a promising radiosensitizer for ESCC radiotherapy.

Rapamycin enhances cetuximab cytotoxicity by inhibiting mTOR-mediated drug resistance in mesenchymal hepatoma cells

The synergistic effect of combined drug therapy provides an enhanced treatment for advanced liver cancer. We aimed to investigate the underlying mechanism of cetuximab sensitization by rapamycin in hepatoma cells. Four hepatoma cell lines, HepG2, HuH7, SNU-387, and SNU-449, were treated with cetuximab or cetuximab plus rapamycin and growth inhibition was evaluated by measuring relative cell viability and cell proliferation. The cell phenotype was determined for each hepatoma cell line by western blot analysis of E-cadherin and vimentin expression and mTOR activation status. To identify the role of mTOR signaling in cetuximab sensitization, we used deferoxamine-mediated hypoxia to induce epithelial-mesenchymal transition (EMT) in HuH7 and HepG2 cells and measured mTOR activity after rapamycin treatment. Rapamycin significantly increased cetuximab cytotoxicity in hepatoma cell lines with differential sensitivities. Phenotypic differences among hepatoma cell lines, specifically epithelial (HuH7 and HepG2) and mesenchymal (SNU-387 and SNU-449), correlated with the efficacy of rapamycin cotreatment, although rapamycin treatment did not affect cell phenotype. We further showed that rapamycin inhibits mTOR in mesenchymal SNU-387 and SNU-449 cells. In addition, the induction of EMT in HuH7 and HepG2 cells significantly decreased cetuximab cytotoxicity; however, rapamycin treatment significantly restored cetuximab sensitivity and decreased mTOR signaling in these cells. In conclusion, we identified significant differences in rapamycin-induced cetuximab sensitization between epithelial and mesenchymal hepatoma cells. We therefore report that rapamycin cotreatment enhances cetuximab cytotoxicity by inhibiting mTOR signaling in mesenchymal cells.

Effects of AG490 and S3I-201 on regulation of the JAK/STAT3 signaling pathway in relation to angiogenesis in TRAIL-resistant prostate cancer cells in vitro

The aim of the present study was to analyze the molecular mechanisms involved in blocking the signaling pathway and the effects of this on the progression of prostate cancer (CaP) cells in vitro. LNCaP human CaP cell line was stimulated with interleukin-6 (IL-6) in the presence/absence of Janus kinase (JAK) 2 (AG490), signal transducer and activator of transcription 3 [(STAT3) S3I-201] inhibitors and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Cytotoxic activity, the activation of phosphorylated (p)-STAT3 protein, caspase (CASP) 3 activity at protein level, vascular endothelial growth factor (VEGF) A, VEGFC, vascular endothelial growth factor receptor 2, STAT3, matrix metalloproteinase-2, myeloid cell leukemia sequence 1 (MCL-1), CASP8 and CASP9 messenger RNA (mRNA) levels were determined. Morphology and apoptosis were confirmed by DAPI staining and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay. IL-6 rapidly induced the phosphorylation of STAT3 in a dose- and time-dependent manner with a peak expression at 3 h at a concentration of 25 ng/ml. In addition, AG490 (50 μM) and S3I-201 (300 μM) inhibited STAT3 activation. Western blotting results revealed that p-STAT3 protein expression decreased significantly with AG490 and S3I-201 treatment in LNCaP cells. AG490 and S3I-201 induced the downregulation of VEGFA, MCL-1 and STAT3 and the upregulation of CASP8 and CASP9 mRNA transcription levels. In addition, the inhibitors increased the level of CASP3 protein. Combinations of AG490- and S3I-201-TRAIL did not result in an increase in this effect. Parallel results were found by DAPI staining and TUNEL assay. To the best of our knowledge, this is the first study to investigate the possible clinical use of AG490 or S3I-201, together with the reduced use of chemotherapeutic agents with high cytotoxicity, for their ability to exert an apoptotic effect, targeting the JAK/STAT3 pathway.

Regulation of interleukin-6 in head and neck squamous cell carcinoma is related to papillomavirus infection

The prevalence of head and neck squamous cell carcinoma (HNSCC) related to human papillomavirus (HPV) is increasing, unlike tobacco- and alcohol-associated cancers. To gain a clearer understanding of the molecular mechanisms implicated in HNSCC, depending on the presence or not of a viral sequence, we investigated the expression of proteins detected in the tumor regions of HNSCC patients. Twenty-two untreated HNSCC patients were selected according to the presence of HPV-16. For six patients, tumor and controlateral healthy tissues were tested for viral detection before quantitative proteomic analysis. After confirmation by Western blot, proteins were connected into a network, leading to investigate interleukin-6 (IL-6) by immunocytochemistry and ELISA. 41 ± 5% of proteins quantified by proteomics were differentially expressed in tumor compared with healthy regions. Among them, 36 proteins were retained as modulated in HPV-16 positive or negative tumors, including cytokeratins, tubulins, annexin A1, and serpin B1. Network analysis suggested a central role of IL-6, confirmed by overexpression of IL-6 in tumor tissues as in sera of HPV-negative HNSCC compared with HPV-16-positive tumors. This modulation may contribute to the survival and proliferation of cancer cells, although it was not related to tumor stage or to the level of HPV-16 DNA.

Therapeutically targeting glypican-3 via a conformation-specific single-domain antibody in hepatocellular carcinoma

Glypican-3 (GPC3) has emerged as a candidate therapeutic target in hepatocellular carcinoma (HCC), but the oncogenic role of GPC3 in HCC is poorly understood. Here, we report a human heavy-chain variable domain antibody, HN3, with high affinity (Kd = 0.6 nM) for cell-surface-associated GPC3 molecules. The human antibody recognized a conformational epitope that requires both the amino and carboxy terminal domains of GPC3. HN3 inhibited proliferation of GPC3-positive cells and exhibited significant inhibition of HCC xenograft tumor growth in nude mice. The underlying mechanism of HN3 action may involve cell-cycle arrest at G1 phase through Yes-associated protein signaling. This study suggests a previously unrecognized mechanism for GPC3-targeted cancer therapy.

Hepatitis C virus-related hepatocellular carcinoma: An insight into molecular mechanisms and therapeutic strategies

Hepatitis C virus (HCV) infects more than 170 million people worldwide, and thereby becomes a series global health challenge. Chronic infection with HCV is considered one of the major causes of end-stage liver disease including cirrhosis and hepatocellular carcinoma. Although the multiple functions of the HCV proteins and their impacts on the modulation of the intracellular signaling transduction processes, the drive of carcinogenesis during the infection with HCV, is thought to result from the interactions of viral proteins with host cell proteins. Thus, the induction of mutator phenotype, in liver, by the expression of HCV proteins provides a key mechanism for the development of HCV-associated hepatocellular carcinoma (HCC). HCC is considered one of the most common malignancies worldwide with increasing incidence during the past decades. In many countries, the trend of HCC is attributed to several liver diseases including HCV infection. However, the development of HCC is very complicated and results mainly from the imbalance between tumor suppressor genes and oncogenes, as well as from the alteration of cellular factors leading to a genomic instability. Besides the poor prognosis of HCC patients, this type of tumor is quite resistance to the available therapies. Thus, understanding the molecular mechanisms, which are implicated in the development of HCC during the course of HCV infection, may help to design a general therapeutic protocol for the treatment and/or the prevention of this malignancy. This review summarizes the current knowledge of the molecular mechanisms, which are involved in the development of HCV-associated HCC and the possible therapeutic strategies.

Targeting Stat3 abrogates EGFR inhibitor resistance in cancer

PURPOSE

EGF receptor (EGFR) is upregulated in most epithelial cancers where signaling through EGFR contributes to cancer cell proliferation and survival. The limited clinical efficacy of EGFR inhibitors suggests that identification of resistance mechanisms may identify new pathways for therapeutic targeting. STAT3 is upregulated in many cancers and activated via both EGFR-dependent and -independent pathways. In the present study, we tested the consequences of STAT3 inhibition in EGFR inhibitor-resistant head and neck squamous cell carcinoma (HNSCC) and bladder cancer models to determine whether STAT3 blockade can enhance responses to EGFR targeting.

EXPERIMENTAL DESIGN

pSTAT3 expression was assessed in human HNSCC tumors that recurred following cetuximab treatment. Cetuximab-sensitive and -resistant cell lines were treated with a STAT3 decoy to determine EC(50) concentrations and the effects on STAT3 target gene expression by Western blotting. In vivo assays included evaluation of antitumor efficacy of STAT3 decoy in cetuximab-sensitive and -resistant models followed by immunoblotting for STAT3 target protein expression.

RESULTS

Targeting STAT3 with a STAT3 decoy reduced cellular viability and the expression of STAT3 target genes in EGFR inhibitor resistance models. The addition of a STAT3 inhibitor to EGFR blocking strategies significantly enhanced antitumor effects in vivo. Biopsies from HNSCC tumors that recurred following cetuximab treatment showed increased STAT3 activation compared with pretreatment biopsies.

CONCLUSIONS

These results suggest that STAT3 activation contributes to EGFR inhibitor resistance both in HNSCC and bladder cancer where concomitant targeting of STAT3 may represent an effective treatment strategy.

NSC 74859 enhances doxorubicin cytotoxicity via inhibition of epithelial-mesenchymal transition in hepatocellular carcinoma cells

Doxorubicin-based therapy is not effective for the treatment of hepatocellular carcinomas (HCCs), which often undergo epithelial-mesenchymal transition (EMT) during tumor progression. Activation of signal transducer and activator of transcription 3 (STAT3) is associated with chemosensitivity and may contribute to EMT during HCC chemotherapy. Low doses of NSC 78459 (a novel STAT3 inhibitor) have little effect on HCC cell proliferation, but efficiently inhibit STAT3. HuH-7, Hep3B, and HepG2 cells, with epithelial phenotypes, show significantly enhanced doxorubicin cytotoxicity following co-treatment with NSC 74859, whereas mesenchymal SNU-449 cells show no such enhancement. NSC 74859 inhibits STAT3 activity and suppressed doxorubicin-induced EMT in epithelial HCC cells. siRNA-mediated STAT3 knockdown resulted in EMT inhibition, which led to attenuation of NSC 74859-mediated chemosensitivity. Our data indicate NSC 74859 co-administration enhances doxorubicin cytotoxicity by inhibiting STAT3 in epithelial HCC cells. STAT3 deactivation and associated EMT attenuation contribute to the synergistic anti-tumor effects of combined NSC 74859/doxorubicin therapy.