Resistance to chemotherapy via Stat3-dependent overexpression of Bcl-2 in metastatic breast cancer cells

Growth-suppressive activity of raloxifene on liver cancer cells by targeting IL-6/GP130 signaling

Background

Interleukin-6 (IL-6) is a multifunctional cytokine, which is involved in the regulation of differentiation and growth of certain types of tumor cells. Constitutive activation of Signal Transducer and Activator of Transcription 3 (STAT3) induced by IL-6 is frequently detected in liver cancer and has emerged as a viable molecular target for liver cancer treatment. However, few inhibitors targeting up-streams of STAT3 are available for the therapy of liver cancer. We reported the discovery of EVISTA (Raloxifene HCl) as novel inhibitor of IL-6/GP130 protein-protein interactions (PPIs) using multiple ligand simultaneous docking (MLSD) and drug repositioning. The possible effect of Raloxifene in STAT3 signaling or liver cancer cells is still unclear.

Results

Raloxifene inhibited the P-STAT3 stimulated by IL-6, but not the induction of STAT1 and STAT6 phosphorylation by IFN-γ, IFN-α, and IL-4. Raloxifene inhibited STAT3 phosphorylation and resulted in the induction apoptosis on human liver cancer cell-lines. Raloxifene inhibited the targets of STAT3, such as Bcl-2, Bcl-xl and survivin and cell viability, cell migration, and colony formation in liver cancer cells. Further, daily administration of Raloxifene suppressed the Hep-G2 tumor growth in mice in vivo.

Materials and Methods

The inhibitory effect on STAT3 phosphorylation and activity as well as cell viability, migration, and colony forming ability by Raloxifene was examined in human liver cancer cells. Tumor growth was detected via mouse xenograft tumor mode.

Conclusions

Our results suggest that Raloxifene is a potent IL-6/GP130 inhibitor and may be a chemoprevention agent for liver cancer by targeting persistent STAT3 signaling.

Intrinsic apoptotic pathway activation increases response to anti-estrogens in luminal breast cancers

Estrogen receptor-α positive (ERα+) breast cancer accounts for approximately 70–80% of the nearly 25,0000 new cases of breast cancer diagnosed in the US each year. Endocrine-targeted therapies (those that block ERα activity) serve as the first line of treatment in most cases. Despite the proven benefit of endocrine therapies, however, ERα+ breast tumors can develop resistance to endocrine therapy, causing disease progression or relapse, particularly in the metastatic setting. Anti-apoptotic Bcl-2 family proteins enhance breast tumor cell survival, often promoting resistance to targeted therapies, including endocrine therapies. Herein, we investigated whether blockade of anti-apoptotic Bcl-2 family proteins could sensitize luminal breast cancers to anti-estrogen treatment. We used long-term estrogen deprivation (LTED) of human ERα+ breast cancer cell lines, an established model of sustained treatment with and acquired resistance to aromatase inhibitors (AIs), in combination with Bcl-2/Bcl-xL inhibition (ABT-263), finding that ABT-263 induced only limited tumor cell killing in LTED-selected cells in culture and in vivo. Interestingly, expression and activity of the Bcl-2-related factor Mcl-1 was increased in LTED cells. Genetic Mcl-1 ablation induced apoptosis in LTED-selected cells, and potently increased their sensitivity to ABT-263. Increased expression and activity of Mcl-1 was similarly seen in clinical breast tumor specimens treated with AI + the selective estrogen receptor downregulator fulvestrant. Delivery of Mcl-1 siRNA loaded into polymeric nanoparticles (MCL1 si-NPs) decreased Mcl-1 expression in LTED-selected and fulvestrant-treated cells, increasing tumor cell death and blocking tumor cell growth. These findings suggest that Mcl-1 upregulation in response to anti-estrogen treatment enhances tumor cell survival, decreasing response to therapeutic treatments. Therefore, strategies blocking Mcl-1 expression or activity used in combination with endocrine therapies would enhance tumor cell death.

Celastrol suppresses the proliferation of lung adenocarcinoma cells by regulating microRNA-24 and microRNA-181b

Cumulative evidence has indicated that celastrol may suppress cancer growth; however, the underlying mechanism requires further investigation. In the present study, A549 cells were treated with various concentrations of celastrol. Lung cancer cell proliferation was evaluated using an MTT assay and observed under a microscope. Cell apoptosis was detected by Annexin V fluorescein isothiocyanate/propidium iodide double-labeled flow cytometry. The results demonstrated that celastrol suppressed proliferation and induced apoptosis in a dose-independent manner. Celastrol may also decrease the phosphorylation levels of signal transducer and activator of transcription 3 (STAT3) and the B cell lymphoma-2 (Bcl-2)/Bcl-2 associated C protein (Bax) ratio. As microRNA (miR-24 and miR-181b) were predicated to target STAT3, STAT3 activation was inhibited in miR-24-or miR-181b-treated A549 cells compared with the control treatment. The ratio of Bcl-2/Bax was further reduced in miR-24 or miR-181b-treated A549 cells. The results were further confirmed by detecting in another lung adenocarcinoma cell line, LTEP-a-2. In summary, the results of the present study demonstrated that celastrol treatment suppressed the proliferation and induced apoptosis by regulating the expression levels of miR-24 and miR-181b.

Knockdown of long non-coding RNA HOTAIR sensitizes hepatocellular carcinoma cell to cisplatin by suppressing the STAT3/ABCB1 signaling pathway

Long non-coding RNA HOX transcript antisense RNA (HOTAIR) has been demonstrated to exhibit oncogenic activity in several types of cancer, including hepatocellular carcinoma (HCC). However, the association between HOTAIR and HCC multidrug resistance remains uncertain. The present study aimed to investigate the role of HOTAIR in HCC chemoresistance; it was found that knockdown of HOTAIR expression in HCC Huh7 cells resulted in decreased cell proliferation and increased chemosensitivity to cisplatin. Furthermore, expression levels of ATP binding cassette subfamily B member 1 (ABCB1) mRNA and protein were decreased in Huh7 cells upon HOTAIR-knockdown. In addition, HOTAIR-knockdown reduced the levels of phosphorylated signal transducer and activator of transcription 3 (STAT3), and inhibition of STAT3 phosphorylation reduced HOTAIR-mediated ABCB1 expression. Together, these findings indicated that knockdown of HOTAIR in Huh7 cells decreased STAT3 activity and ABCB1 expression, and increased chemosensitivity to cisplatin. Thus HOTAIR could serve as a novel potential therapeutic target to reverse multidrug resistance in HCC.

Silibinin sensitizes chemo-resistant breast cancer cells to chemotherapy

CONTEXT

Multiple drug resistance is the major obstacle to conventional chemotherapy. Silibinin, a nontoxic naturally occurring compound, has anticancer activity and can increase the cytotoxic effects of chemotherapy in various cancer models.

OBJECTIVE

To evaluate the effects of silibinin on enhancing the sensitivity of chemo-resistant human breast cell lines to doxorubicin (DOX) and paclitaxel (PAC).

MATERIALS AND METHODS

The cells were treated with silibinin (at 50 to 600 μM concentrations) and/or chemo drugs for 24 and 48 h, then cell viability and changes in oncogenic proteins were determined by MTT assay and Western blotting/RT-PCR, respectively. Flow cytometry was used to study apoptosis in the cells receiving different treatments. The antitumorigenic effects of silibinin (at 200 to 400 μM concentration) were evaluated by mammosphere assay.

RESULTS

Silibinin exerted significant growth inhibitory effects with IC₅₀ ranging from 200 to 570 μM in different cell lines. Treatment of DOX-resistant MDA-MB-435 cells with silibinin at 200 μM reduced DOX IC₅₀ from 71 to 10 μg/mL and significantly suppressed the key oncogenic pathways including STAT3, AKT, and ERK in these cells. Interestingly treatment of DOX-resistant MDA-MB-435 cells with silibinin at 400 μM concentration for 48 h induced a 50% decrease in the numbers of colonies as compared with DMSO-treated cells. Treatment of PAC-resistant MCF-7 cells with silibinin at 400 μM concentration generated synergistic effects when it was used in combination with PAC at 250 nM concentration (CI = 0.81).

CONCLUSION

Silibinin sensitizes chemo-resistant cells to chemotherapeutic agents and can be useful in treating breast cancers.

A novel small molecule STAT3 inhibitor, LY5, inhibits cell viability, colony formation, and migration of colon and liver cancer cells

Signal Transducer and Activator of Transcription 3 (STAT3) is persistently activated in human liver and colon cancer cells and is required for cancer cell viability, survival and migration. Therefore, inhibition of STAT3 signaling may be a viable therapeutic approach for these two cancers. We recently designed a non-peptide small molecule STAT3 inhibitor, LY5, using in silico site-directed Fragment-based drug design (FBDD). The inhibitory effect on STAT3 phosphorylation, cell viability, migration and colony forming ability by LY5 were examined in human liver and colon cancer cells. We demonstrated that LY5 inhibited constitutive Interleukin-6 (IL-6)-induced STAT3 phosphorylation, STAT3 nuclear translocation, decreased STAT3 downstream targeted gene expression and induced apoptosis in liver and colon cancer cells. LY5 had little effect on STAT1 phosphorylation mediated by IFN-γ. Inhibition of persistent STAT3 phosphorylation by LY5 also inhibited colony formation, cell migration, and decreased the viability of liver cancer and colon cancer cells. Furthermore, LY5 inhibited STAT3 phosphorylation and suppressed colon tumor growth in a mouse model in vivo. Our results suggest that LY5 is a potent STAT3 inhibitor and may be a potential drug candidate for liver and colon cancer therapy.

Implications of Bcl-2 and its interplay with other molecules and signaling pathways in prostate cancer progression

INTRODUCTION

Among several genetic alterations involved in the progression of prostate cancer, B cell lymphoma gene number 2 (BCL-2) is an important target molecule in the progression of androgen-independent prostate cancer (AIPC) after androgen ablation or castration. Nevertheless, the molecular mechanism of BCL-2 in prostate cancer progression remains elusive and controversial. In the current review, we discuss the critical role of BCL-2 in the carcinogenesis of prostate cancer with experimental evidences on the BCL-2 molecular networks in AIPC and androgen-dependent prostate cancer (ADPC) and subsequently suggest perspective research targeting BCL-2. Areas covered: This review focused on the molecular implications of BCL-2 in association with other molecules and signaling pathways involved in the progression and carcinogenesis of prostate cancer. Expert opinion: BCL-2 plays a pivotal role in the progression of AIPC than in ADPC since androgen represses BCL-2. BCL-2 acts as a pro-survival molecule in association with androgen-related signaling in the progression of ADPC, while BCL-2 upregulation, PTEN loss, PI3K/AKT phosphorylation and receptor tyrosine kinase (RTK) activation are primarily involved in AIPC. To identify more effective prostate cancer therapy, further mechanistic studies are required with BCL-2 inhibitors in AIPC and ADPC, considering a multi-target therapy against BCL-2 and its related signaling.

Regulation of cell signaling pathways by dietary agents for cancer prevention and treatment

Although it is widely accepted that better food habits do play important role in cancer prevention and treatment, how dietary agents mediate their effects remains poorly understood. More than thousand different polyphenols have been identified from dietary plants. In this review, we discuss the underlying mechanism by which dietary agents can modulate a variety of cell-signaling pathways linked to cancer, including transcription factors, nuclear factor κB (NF-κB), signal transducer and activator of transcription 3 (STAT3), activator protein-1 (AP-1), β-catenin/Wnt, peroxisome proliferator activator receptor- gamma (PPAR-γ), Sonic Hedgehog, and nuclear factor erythroid 2 (Nrf2); growth factors receptors (EGFR, VEGFR, IGF1-R); protein Kinases (Ras/Raf, mTOR, PI3K, Bcr-abl and AMPK); and pro-inflammatory mediators (TNF-α, interleukins, COX-2, 5-LOX). In addition, modulation of proteasome and epigenetic changes by the dietary agents also play a major role in their ability to control cancer. Both in vitro and animal based studies support the role of dietary agents in cancer. The efficacy of dietary agents by clinical trials has also been reported. Importantly, natural agents are already in clinical trials against different kinds of cancer. Overall both in vitro and in vivo studies performed with dietary agents strongly support their role in cancer prevention. Thus, the famous quote "Let food be thy medicine and medicine be thy food" made by Hippocrates 25 centuries ago still holds good.

Toosendanin demonstrates promising antitumor efficacy in osteosarcoma by targeting STAT3

Signal transducer and activator of transcription 3(STAT3) is an emerging target for cancer therapy. In this study, we identify Toosendanin (TSN) is an effective inhibitor of STAT3, leading to the impediment of various oncogenic processes in osteosarcoma. TSN selectively inactivates phospho-STAT3 (Tyr-705); subsequent molecular docking and in vitro SPR analysis uncover TSN directly binds to the SH2 domain of STAT3. Consequently, TSN blocks STAT3 dimerization and impairs the complex formation of STAT3 and epidermal growth factor receptor (EGFR). In an animal tumor model study, TSN is well tolerated, inhibits osteosarcoma growth and metastasis. In another osteosarcoma patient-derived xenografts (PDX) model, we find TSN triggers strong inhibitory effects on patient-derived tumors. Further studies show that TSN also displays activity against other solid tumors. Our preclinical work therefore supports that TSN acts as a novel inhibitor of STAT3 that blocks tumorigenesis in ostoesarcoma.

Targeting phosphorylation of STAT3 delays tumor growth in HPV-negative anal squamous cell carcinoma mouse model

Although conventional chemoradiotherapy is effective for most anal squamous cell carcinoma (ASCC) patients, HPV-negative ASCC patients respond poorly to this treatment and new therapeutic approach is required. Our group has previously established an HPV-negative ASCC mouse model and demonstrated that signal transducer and activation of transcription 3 (STAT3) is hyper-activated in the model. Here, we show that in vivo inhibition of STAT3 by S3I-201 effectively delays tumor growth in ASCC mouse model indicated by significantly smaller tumor size and burden in the treatment group compared with control group at the same point. Further analysis shows that survivin and Ki67, important biomarkers for tumor cell survival and proliferation, are significantly reduced after S3I-201 treatment. Additionally, flow cytometry and immunohistofluorescent assays reveal decreased Myeloid-derived suppressor cell (MDSC) and tumor-associated macrophage (TAM) populations in the S3I-201 treatment group, which indicates a reversion of the immunosuppressive environment, unraveling the potential role for S3I-201 in immunosuppression in ASCC. Together these results for the first time demonstrated the anti-tumor effects of STAT3 inhibitor S3I-201 in HPV-negative ASCC mouse model and its multiple effects on cancer cells and immune system. Thus we conclude that S3I-201 may be a novel therapeutic approach for HPV-negative ASCC patients.

A muscle-specific protein 'myoferlin' modulates IL-6/STAT3 signaling by chaperoning activated STAT3 to nucleus

Myoferlin, a member of ferlin family of proteins, was first discovered as a candidate gene for muscular dystrophy and cardiomyopathy. Recently, myoferlin was shown to be also expressed in endothelial and cancer cells where it was shown to modulate vascular endothelial growth factor (VEGFR)-2 and epidermal growth factor receptor (EGFR) signaling by enhancing their stability and recycling. Based on these reports, we hypothesized that myoferlin might be regulating IL-6 signaling by modulating IL-6R stabilization and recycling. However, in our immunoprecipitation (IP) experiments, we did not observe myoferlin binding with IL-6R. Instead, we made a novel discovery that in resting cells myoferlin was bound to EHD2 protein and when cells were treated with IL-6, myoferlin dissociated from EHD2 and binds to activated STAT3. Interestingly, myoferlin depletion did not affect STAT3 phosphorylation, but completely blocked STAT3 translocation to nucleus. In addition, inhibition of STAT3 phosphorylation by phosphorylation-defective STAT3 mutants or JAK inhibitor blocked STAT3 binding to myoferlin and nuclear translocation. Myoferlin knockdown significantly decreased IL-6-mediated tumor cell migration, tumorsphere formation and ALDH-positive cancer stem cell population, in vitro. Furthermore, myoferlin knockdown significantly decreased IL-6-meditated tumor growth and tumor metastasis. Based on these results, we have proposed a novel model for the role of myoferlin in chaperoning phosphorylated STAT3 to the nucleus.

Repositioning Bazedoxifene as a novel IL-6/GP130 signaling antagonist for human rhabdomyosarcoma therapy

Interleukins-6 (IL-6)/GP130 signaling pathway represents a promising target for cancer therapy due to its critical role in survival and progression of multiple types of cancer. We have identified Bazedoxifene, a Food and Drug Administration (FDA)-approved drug used for the prevention of postmenopausal osteoporosis, with novel function as inhibitor of IL-6/GP130 interaction. In this study, we investigate the effect of Bazedoxifene in rhabdomyosarcoma and evaluate whether inhibiting IL-6/GP130 signaling is an effective therapeutic strategy for rhabdomyosarcoma. The inhibitory effect of Bazedoxifene was assessed in rhabdomyosarcoma cell lines in vitro and RH30 xenograft model was used to further examine the suppressive efficacy of Bazedoxifene on tumor growth in vivo. Rhabdomyosarcoma cells showed their sensitivity to GP130 inhibition using gene knockdown or neutralized antibody, suggesting IL-6/GP130 as therapeutic target in rhabdomyosarcoma cells. Bazedoxifene decreased the signal transducer and activator of transcription3 (STAT3) phosphorylation, blocked STAT3 DNA binding, and down-regulated the expression of STAT3 downstream genes. Bazedoxifene also induced cell apoptosis, reduced cell viability, and inhibited colony formation in rhabdomyosarcoma cells. The inhibition of colony formation, STAT3 phosphorylation, or cell viability following Bazedoxifene treatment was partially reversed by addition of excess IL-6 or overexpression of constitutive STAT3, respectively, supporting Bazedoxifene acted through IL-6/GP130 signaling. In addition, Bazedoxifene repressed cell invasion and angiogenesis in vitro. Furthermore, oral administration of Bazedoxifene significantly suppressed tumor growth and expression of STAT3 phosphorylation in nude mice bearing established human rhabdomyosarcoma xenograft. Taken together, these findings validate IL-6/GP130 signaling as therapeutic target in rhabdomyosarcoma and provide first evidence that Bazedoxifene may serve as a novel promising drug targeting IL-6/GP130 for treatment of rhabdomyosarcoma.

Sequential combination of docetaxel with a SHP-1 agonist enhanced suppression of p-STAT3 signaling and apoptosis in triple negative breast cancer cells

Triple negative breast cancer (TNBC) is an aggressive cancer for which prognosis remains poor. Combination therapy is a promising strategy for enhancing treatment efficacy. Blockade of STAT3 signaling may enhance the response of cancer cells to conventional chemotherapeutic agents. Here we used a SHP-1 agonist SC-43 to dephosphorylate STAT3 thereby suppressing oncogenic STAT3 signaling and tested it in combination with docetaxel in TNBC cells. We first analyzed messenger RNA (mRNA) expression of SHP-1 gene (PTPN6) in a public TNBC dataset (TCGA) and found that higher SHP-1 mRNA expression is associated with better overall survival in TNBC patients. Sequential combination of docetaxel and SC-43 in vitro showed enhanced anti-proliferation and apoptosis associated with decreased p-STAT3 and decreased STAT3-downstream effector cyclin D1 in the TNBC cell lines MDA-MB-231, MDA-MB-468, and HCC-1937. Ectopic expression of STAT3 reduced the increased cytotoxicity induced by the combination therapy. In addition, this sequential combination showed enhanced SHP-1 activity compared to SC-43 alone. Furthermore, the combination treatment-induced apoptosis was attenuated by small interfering RNA (siRNA) against SHP-1 or by ectopic expression of SHP-1 mutants that caused SC-43 to lose its SHP-1 agonist capability. Moreover, combination of docetaxel and SC-43 showed enhanced tumor growth inhibition compared to single-agent therapy in mice bearing MDA-MB-231 tumor xenografts. Our results suggest that the novel SHP-1 agonist SC-43 enhanced docetaxel-induced cytotoxicity by SHP-1 dependent STAT3 inhibition in human triple negative breast cancer cells. TNBC patients with high SHP-1 expressions show better survival. Docetaxel combined with SC-43 enhances cell apoptosis and reduces p-STAT3. SHP-1 inhibition reduces the enhanced effect of docetaxel-SC-43 combination. Docetaxel-SC-43 combination suppresses xenograft tumor growth and reduces p-STAT3.

KEY MESSAGES

TNBC patients with high SHP-1 expressions show better survival. Docetaxel combined with SC-43 enhances cell apoptosis and reduces p-STAT3. SHP-1 inhibition reduces the enhanced effect of docetaxel-SC-43 combination. Docetaxel-SC-43 combination suppresses xenograft tumor growth and reduces p-STAT3.

Leptin signaling and cancer chemoresistance: Perspectives

Obesity is a major health problem and currently is endemic around the world. Obesity is a risk factor for several different types of cancer, significantly promoting cancer incidence, progression, poor prognosis and resistance to anti-cancer therapies. The study of this resistance is critical as development of chemoresistance is a serious drawback for the successful and effective drug-based treatments of cancer. There is increasing evidence that augmented adiposity can impact on chemotherapeutic treatment of cancer and the development of resistance to these treatments, particularly through one of its signature mediators, the adipokine leptin. Leptin is a pro-inflammatory, pro-angiogenic and pro-tumorigenic adipokine that has been implicated in many cancers promoting processes such as angiogenesis, metastasis, tumorigenesis and survival/resistance to apoptosis. Several possible mechanisms that could potentially be developed by cancer cells to elicit drug resistance have been suggested in the literature. Here, we summarize and discuss the current state of the literature on the role of obesity and leptin on chemoresistance, particularly as it relates to breast and pancreatic cancers. We focus on the role of leptin and its significance in possibly driving these proposed chemoresistance mechanisms, and examine its effects on cancer cell survival signals and expansion of the cancer stem cell sub-populations.

Sorafenib analogue SC-60 induces apoptosis through the SHP-1/STAT3 pathway and enhances docetaxel cytotoxicity in triple-negative breast cancer cells

Recurrent triple-negative breast cancer (TNBC) needs new therapeutic targets. Src homology region 2 domain-containing phosphatase-1 (SHP-1) can act as a tumor suppressor by dephosphorylating oncogenic kinases. One major target of SHP-1 is STAT3, which is highly activated in TNBC. In this study, we tested a sorafenib analogue SC-60, which lacks angiokinase inhibition activity, but acts as a SHP-1 agonist, in TNBC cells. SC-60 inhibited proliferation and induced apoptosis by dephosphorylating STAT3 in both a dose- and time-dependent manner in TNBC cells (MDA-MB-231, MDA-MB-468, and HCC1937). By contrast, ectopic expression of STAT3 rescued the anticancer effect induced by SC-60. SC-60 also increased the SHP-1 activity, but this effect was inhibited when the N-SH2 domain (DN1) was deleted or with SHP-1 point mutation (D61A), implying that SHP-1 is the major target of SC-60 in TNBC. The use of SC-60 in combination with docetaxel synergized the anticancer effect induced by SC-60 through the SHP-1/STAT3 pathway in TNBC cells. Importantly, SC-60 also displayed a significant antitumor effect in an MDA-MB-468 xenograft model by modulating the SHP-1/STAT3 axis, indicating the anticancer potential of SC-60 in TNBC treatment. Targeting SHP-1/p-STAT3 and the potential combination of SHP-1 agonist with chemotherapeutic docetaxel is a feasible therapeutic strategy for TNBC.

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.

Artesunate acts as fuel to fire in sensitizing HepG2 cells towards TRAIL mediated apoptosis via STAT3 inhibition and DR4 augmentation

In the present study, we investigated in vitro, the role of artesunate (ATS) with comparable potency to oxaliplatin (OXP) in sensitizing tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) resistant HepG2 cells towards apoptosis. ATS in consistency with OXP was found to reverse TRAIL resistant HepG2 cells towards TRAIL mediated apoptosis by enhancing caspase-3 and cleavage of PARP. Additionally, ATS also suppressed the nuclear translocation of activated signal transducers and activators of transcription 3 (STAT3) thereby sensitizing the HepG2 cells towards only death receptor 4 (DR4) mediated apoptosis. Furthermore, ATS exposure in TRAIL resistant cells resulted in significant increase of both DR4/DR5 expression and STAT3 inhibition thereby arbitrating TRAIL mediated apoptosis in HepG2 cells. The increase in expression was comparable to that of STAT3 silenced cells. From all the above observations, we conclude that ATS up-regulated DR4 expression by targeting STAT3, which in turn sensitized HepG2 cells to TRAIL mediated apoptosis.

Therapeutic vaccination based on side population cells transduced by the granulocyte-macrophage colony-stimulating factor gene elicits potent antitumor immunity

Among cancer immunotherapies, granulocyte-macrophage colony-stimulating factor (GM-CSF) gene-transduced tumor cell vaccine (GVAX) therapies appear promising and have been shown to be safe and effective in multiple clinical trials. However, the antitumor efficacies of GVAX therapy alone are in some cases limited. Here we showed that GVAX therapy targeting cancer stem cells (CSCs) substantially suppressed tumor development in syngeneic immunocompetent mice recapitulating normal immune systems. CSCs were isolated as side population (SP) cells from 4T1 murine breast carcinoma cell line and transduced with GM-CSF gene delivered by non-transmissible Sendai virus (4T1-SP/GM). Impaired tumorigenicity of subcutaneously injected 4T1-SP/GM depended on CD8⁺ T cells in concert with CD4⁺ T cells and natural killer cells. Mice therapeutically vaccinated with irradiated 4T1-SP/GM cells had markedly suppressed tumor development of subcutaneously transplanted 4T1-SP cells compared with those treated with irradiated cells of non-transduced 4T1-SP cells or non-SP (4T1-NSP/GM) cells. Tumor suppression was accompanied by the robust accumulation of mature dendritic cells at vaccination sites and T-helper type 1-skewed systemic cellular immunity. Our results suggested that CSC cell-based GVAX immunotherapy might be clinically useful for inducing potent tumor-specific antitumor immunity.

Adaptive mechanisms of resistance to anti-neoplastic agents

Intrinsic and acquired resistance to conventional and targeted therapeutics is a fundamental reason for treatment failure in many cancer patients. Targeted approaches to overcome chemoresistance as well as resistance to targeted approaches require in depth understanding of the underlying molecular mechanisms. The anti-cancer activity of a drug can be limited by a broad variety of molecular events at different levels of drug action in a cell-autonomous and non-cell-autonomous manner. This review summarizes recent insights into the adaptive mechanisms used by tumours to resist therapy including cellular phenotypic plasticity, dynamic alterations of the tumour microenvironment, activation of redundant signal transduction pathways, modulation of drug target expression levels, and exploitation of pro-survival responses.

Key Survival Factor, Mcl-1, Correlates with Sensitivity to Combined Bcl-2/Bcl-xL Blockade

An estimated 40,000 deaths will be attributed to breast cancer in 2016, underscoring the need for improved therapies. Evading cell death is a major hallmark of cancer, driving tumor progression and therapeutic resistance. To evade apoptosis, cancers use antiapoptotic Bcl-2 proteins to bind to and neutralize apoptotic activators, such as Bim. Investigation of antiapoptotic Bcl-2 family members in clinical breast cancer datasets revealed greater expression and more frequent gene amplification of MCL1 as compared with BCL2 or BCL2L1 (Bcl-xL) across three major molecular breast cancer subtypes, Luminal (A and B), HER2-enriched, and Basal-like. While Mcl-1 protein expression was elevated in estrogen receptor α (ERα)-positive and ERα-negative tumors as compared with normal breast, Mcl-1 staining was higher in ERα⁺ tumors. Targeted Mcl-1 blockade using RNAi increased caspase-mediated cell death in ERα⁺ breast cancer cells, resulting in sustained growth inhibition. In contrast, combined blockade of Bcl-2 and Bcl-xL only transiently induced apoptosis, as cells rapidly acclimated through Mcl-1 upregulation and enhanced Mcl-1 activity, as measured in situ using Mcl-1/Bim proximity ligation assays. Importantly, MCL1 gene expression levels correlated inversely with sensitivity to pharmacologic Bcl-2/Bcl-xL inhibition in luminal breast cancer cells, whereas no relationship was seen between the gene expression of BCL2 or BCL2L1 and sensitivity to Bcl-2/Bcl-xL inhibition. These results demonstrate that breast cancers rapidly deploy Mcl-1 to promote cell survival, particularly when challenged with blockade of other Bcl-2 family members, warranting the continued development of Mcl-1-selective inhibitors for targeted tumor cell killing.Implications: Mcl-1 levels predict breast cancer response to inhibitors targeting other Bcl-2 family members, and demonstrate the key role played by Mcl-1 in resistance to this drug class. Mol Cancer Res; 15(3); 259-68. ©2016 AACR.

Cancer-associated fibroblasts treated with cisplatin facilitates chemoresistance of lung adenocarcinoma through IL-11/IL-11R/STAT3 signaling pathway

Cancer-associated fibroblasts (CAF) are recognized as one of the key determinants in the malignant progression of lung adenocarcinoma. And its contributions to chemoresistance acquisition of lung cancer has raised more and more attention. In our study, cancer associated fibroblasts treated with cisplatin conferred chemoresistance to lung cancer cells. Meanwhile, Interleukin-11(IL-11) was significantly up-regulated in the CAF stimulated by cisplatin. As confirmed in lung adenocarcinoma cells in vivo and in vitro, IL-11 could protect cancer cells from cisplatin-induced apoptosis and thus promote their chemoresistance. Furthermore, it was also observed that IL-11 induced STAT3 phosphorylation and increased anti-apoptotic protein Bcl-2 and Survivin expression in cancer cells. The effect could be abrogated by suppressing STAT3 phosphorylation or silencing IL-11Rα expression in cancer cells. In conclusion, chemotherapy-induced IL-11 upregulation in CAF promotes lung adenocarcinoma cell chemoresistance by activating IL-11R/STAT3 anti-apoptotic signaling pathway.

Gp130-mediated STAT3 activation by S-propargyl-cysteine, an endogenous hydrogen sulfide initiator, prevents doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) could trigger a large amount of apoptotic cells in the myocardium, which leads to dilated cardiomyopathy and heart failure. S-propargyl-cysteine (SPRC), a producing agent of endogenous hydrogen sulfide (H2S), possesses cardioprotective efficacy. However, the specific effect and mechanism of SPRC in Dox-induced cardiotoxicity remain elusive. Given gp130 with its main downstream signaling molecule, signal transducer and activator of transcription 3 (STAT3), is involved in cardiac myocyte survival and growth; the present study was performed to elucidate whether SPRC counteracts Dox-induced cardiotoxicity, and if so, whether the gp130/STAT3 pathway is involved in this cardioprotective activity. SPRC stimulated the activation of STAT3 via gp130-mediated transduction tunnel in vitro and in vivo. In Dox-stimulated cardiotoxicity, SPRC enhanced cell viability, restored expression of gp130/STAT3-regulated downstream genes, inhibited apoptosis and oxidative stress, and antagonized mitochondrial dysfunction and intracellular Ca(2+) overload. Intriguingly, blockade of gp130/STAT3 signaling abrogated all these beneficial capacities of SPRC. Our findings present the first piece of evidence for the therapeutic properties of SPRC in alleviating Dox cardiotoxicity, which could be attributed to the activation of gp130-mediated STAT3 signaling. This will offer a novel molecular basis and therapeutic strategy of H2S donor for the treatment of heart failure.

Stat3 contributes to cancer progression by regulating Jab1/Csn5 expression

Our previous studies demonstrated that Jab1/Csn5 overexpression is correlated with low survival rates in cancer patients, including nasopharyngeal carcinoma (NPC), breast cancer and hepatocellular carcinoma, and contributes to NPC's resistance to radiotherapy and cisplatin by regulating DNA damage and repair pathways. However, the molecular mechanism by which Jab1/Csn5 expression is upregulated in NPCs has yet to be determined. In the present study, we identified the upstream regulator of Jab1/Csn5 expression and demonstrated its role in intrinsic resistance of NPC cells to treatment with cisplatin. Signal transducer and activator of transcription-3 (Stat3) expression correlates with and contributes to Jab1/Csn5 transcription. Consistently, silencing of Stat3 in tumors reduced Jab1/Csn5 expression, thereby sensitizing NPC cells to cisplatin-induced apoptosis both in vitro and in vivo. Mechanistically, Stat3 transcriptionally regulated Jab1/Csn5. Furthermore, high mRNA expression levels of Stat3 or Jab1 in colon cancer, breast cancer and glioblastoma are associated with significantly shorter survival times from the R2 online database. These findings identify a novel Stat3-Jab1/Csn5 signaling axis in cancer pathogenesis with therapeutic and prognostic relevance.

Overexpression of Bcl-2 induces STAT-3 activation via an increase in mitochondrial superoxide

We recently reported a novel interaction between Bcl-2 and Rac1 and linked that to the ability of Bcl-2 to induce a pro-oxidant state in cancer cells. To gain further insight into the functional relevance of this interaction, we utilized computer simulation based on the protein pathway dynamic network created by Cellworks Group Inc. STAT3 was identified among targets that positively correlated with Rac1 and/or Bcl-2 expression levels. Validating this, the activation level of STAT3, as marked by p-Tyr705, particularly in the mitochondria, was significantly higher in Bcl-2-overexpressing cancer cells. Bcl-2-induced STAT3 activation was a function of GTP-loaded Rac1 and NADPH oxidase (Nox)-dependent increase in intracellular superoxide (O₂^•−). Furthermore, ABT199, a BH-3 specific inhibitor of Bcl-2, as well as silencing of Bcl-2 blocked STAT3 phosphorylation. Interestingly, while inhibiting intracellular O₂^•− blocked STAT3 phosphorylation, transient overexpression of wild type STAT3 resulted in a significant increase in mitochondrial O₂^•− production, which was rescued by the functional mutants of STAT3 (Y705F). Notably, a strong correlation between the expression and/or phosphorylation of STAT3 and Bcl-2 was observed in primary tissues derived from patients with different sub-sets of B cell lymphoma. These data demonstrate the presence of a functional crosstalk between Bcl-2, Rac1 and activated STAT3 in promoting a permissive redox milieu for cell survival. Results also highlight the potential utility of a signature involving Bcl-2 overexpression, Rac1 activation and STAT3 phosphorylation for stratifying clinical lymphomas based on disease severity and chemoresistance.

Proteasome Inhibitor YSY01A Enhances Cisplatin Cytotoxicity in Cisplatin-Resistant Human Ovarian Cancer Cells

Cisplatin is one of the most common drugs used for treatment of solid tumors such as ovarian cancer. Unfortunately, the development of resistance against this cytotoxic agent limits its clinical use. Here we report that YSY01A, a novel proteasome inhibitor, is capable of suppressing survival of cisplatin-resistant ovarian cancer cells by inducing apoptosis. And YSY01A treatment enhances the cytotoxicity of cisplatin in drug-resistant ovarian cancer cells. Specifically, YSY01A abrogates regulatory proteins important for cell proliferation and anti-apoptosis including NF-κB p65 and STAT3, resulting in down-regulation of Bcl-2. A dramatic increase in cisplatin uptake was also observed by inductively coupled plasma-mass spectrometry following exposure to YSY01A. Taken together, YSY01A serves as a potential candidate for further development as anticancer therapeutics targeting the proteasome.

Identification of selective cytotoxic and synthetic lethal drug responses in triple negative breast cancer cells

Background

Triple negative breast cancer (TNBC) is a highly heterogeneous and aggressive type of cancer that lacks effective targeted therapy. Despite detailed molecular profiling, no targeted therapy has been established. Hence, with the aim of gaining deeper understanding of the functional differences of TNBC subtypes and how that may relate to potential novel therapeutic strategies, we studied comprehensive anticancer-agent responses among a panel of TNBC cell lines.

Method

The responses of 301 approved and investigational oncology compounds were measured in 16 TNBC cell lines applying a functional profiling approach. To go beyond the standard drug viability effect profiling, which has been used in most chemosensitivity studies, we utilized a multiplexed readout for both cell viability and cytotoxicity, allowing us to differentiate between cytostatic and cytotoxic responses.

Results

Our approach revealed that most single-agent anti-cancer compounds that showed activity for the viability readout had no or little cytotoxic effects. Major compound classes that exhibited this type of response included anti-mitotics, mTOR, CDK, and metabolic inhibitors, as well as many agents selectively inhibiting oncogene-activated pathways. However, within the broad viability-acting classes of compounds, there were often subsets of cell lines that responded by cell death, suggesting that these cells are particularly vulnerable to the tested substance. In those cases we could identify differential levels of protein markers associated with cytotoxic responses. For example, PAI-1, MAPK phosphatase and Notch-3 levels associated with cytotoxic responses to mitotic and proteasome inhibitors, suggesting that these might serve as markers of response also in clinical settings. Furthermore, the cytotoxicity readout highlighted selective synergistic and synthetic lethal drug combinations that were missed by the cell viability readouts. For instance, the MEK inhibitor trametinib synergized with PARP inhibitors. Similarly, combination of two non-cytotoxic compounds, the rapamycin analog everolimus and an ATP-competitive mTOR inhibitor dactolisib, showed synthetic lethality in several mTOR-addicted cell lines.

Conclusions

Taken together, by studying the combination of cytotoxic and cytostatic drug responses, we identified a deeper spectrum of cellular responses both to single agents and combinations that may be highly relevant for identifying precision medicine approaches in TNBC as well as in other types of cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12943-016-0517-3) contains supplementary material, which is available to authorized users.

Cancer chemoresistance; biochemical and molecular aspects: a brief overview

The effectiveness of chemotherapy is one of the main challenges in cancer treatment and resistance to classic drugs and traditional treatment processes is an obstacle to this goal. Drug resistance that may be inherent or adventitious can cause poor treatment outcome and tumor relapse. In most cases, resistance to a drug can lead to resistance to many other drugs structure and function of which is not necessarily similar to the first drug. This phenomenon is the main mechanism behind failure of many of metastatic cancers. There are various molecular mechanisms involved in multidrug resistance, including change in the activity of membrane transporters (such as ABC transporters), increase of drug metabolism, change of the target enzyme (such as mutations that change thymidylate synthase and topoisomerases), promotion of DNA damage repair, and escape from drug induced apoptosis. Clinical and laboratory investigations on biomarkers involved in the response to chemotherapy have characterized the key factors behind the failure of treatments. Knowing the molecular factors involved in drug resistance may help us to develop new strategies for more promising chemotherapy and reduce the rate of relapse. In this brief review, molecular mechanisms and tumor microenvironment leading to decreased drug sensitivity, and strategies of reversing drug resistance are described.

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.

Cisplatin-induced CCL5 secretion from CAFs promotes cisplatin-resistance in ovarian cancer via regulation of the STAT3 and PI3K/Akt signaling pathways

Currently, acquired resistance to cisplatin (DDP) is a substantial obstacle to reducing the morbidity and mortality due to ovarian malignant tumors. Nevertheless, cisplatin plays a vital role in killing the tumor cells while it may also be a 'primer' involved in chemotherapy resistance. We found that the cisplatin-induced chemokine (C-C motif) ligand 5 (CCL5) secretion derived from cancer-associated fibroblasts (CAFs) promoted ovarian cancer cell resistance to cisplatin. Via a cytokine chip assay, we identified a spectrum of secreted proteins that were derived from the CAFs through cisplatin-induced treatment. Among these, CCL5 significantly attenuated the cytotoxic effect of cisplatin chemotherapy in vitro and in vivo. Additionally, CCL5 expression was also detected in 62 serous ovarian cancer patient tissue specimens using IHC, and the results demonstrated that chemotherapy resistant patients displayed higher expression of CCL5 than the chemo-sensitive patients (P<0.05). Mechanistically, we found that CCL5 notably increased STAT3 and Akt phosphorylation levels in ovarian cancer cells. These results indicated that cisplatin- induced CCL5 secretion derived from the CAFs may promote cisplatin resistance, which was mediated by regulation of the STAT3 and PI3K/Akt signal pathways.

Mitochondrial Stat3, the Need for Design Thinking

Stat3 has been studied extensively as a transcription factor, however the finding that Stat3 also localizes to mitochondria has opened a new area to discover non-classical functions. Here we review the current knowledge of mitochondrial Stat3 as a regulator of the electron transport chain (ETC) and its impact on mitochondrial production of ATP and ROS. We also describe recent findings identifying Stat3 as a regulator of mitochondrial Ca(2+) homeostasis through its effect on the ETC. It is becoming evident that these non-classical functions of Stat3 can have a major impact on cancer progression, cardiovascular diseases, and inflammatory diseases. Therefore, mitochondrial Stat3 functions challenge the current design of therapies that solely target Stat3 as a transcription factor and suggest the need for "design thinking," which leads to the development of novel strategies, to intervene the Stat3 pathway.

Functional characterization of TRPM7 in nasopharyngeal carcinoma and its knockdown effects on tumorigenesis

The aim of this study was to evaluate the association of functional expression of TRPM7 with nasopharyngeal carcinoma (NPC) growth. We examined the correlation of TRPM7 expression with cell growth and proliferation, cell cycle, and apoptosis in vitro in NPC cell lines and NPC tumorigenesis in mice by conducting experiments in mice and by further analyzing the tumor volume and growth. We further explored to see whether there is any positive correlation with the TRPM7 knockdown in NPC cells with their sensitivity to radiation. We found that the functional expression of TRPM7 in nasopharyngeal carcinoma is a critical requirement for physiological processes such as cell cycle, resistance to apoptosis, and cell proliferation. TRPM7 knockdown also enhanced sensitivity to radiotherapy of nasopharyngeal carcinoma. Moreover, we identified TRPM7 as a novel potential regulator of cell proliferation in NPC, through signal transducer and activator of transcription 3 (STAT3)-mediated signaling pathway and other anti-apoptotic factors. TRPM7 and STAT3 activation might be critical for the growth of NPC cells and could be an effective target for treatment of nasopharyngeal carcinoma.

Erdr1 Suppresses Murine Melanoma Growth via Regulation of Apoptosis

Melanoma, one of the aggressive cancers, is known to be resistant to chemotherapy. Because of its aggressive nature, effectively inducing apoptosis is necessary to treat melanoma. Erythroid differentiation regulator 1 (Erdr1) is known to be a stress-related survival factor exhibiting anti-cancer effects in several cancers. However, little is known about the functions and underlying mechanisms of Erdr1 so far. To demonstrate the effect of Erdr1 in melanoma apoptosis, recombinant murine Erdr1 was injected into mice implanted with B16F10 melanoma cells. In vivo tumor growth was significantly inhibited in mice injected with Erdr1 compared to the control. In addition, the tumor from Erdr1-injected mice showed an increased level of apoptosis. Accordingly, apoptosis-regulating factors including anti-apoptotic marker Bcl-2 and pro-apoptotic marker Bax in the tumor tissues were examined. As expected, the decreased level of Bcl-2 and increased level of Bax were detected in tumors within the mice injected with Erdr1. Based on the in vivo study, the role of Erdr1 in tumor apoptosis was further tested by incubating it with cells of the murine melanoma cell line B16F10. Erdr1-induced apoptosis in B16F10 cells was observed. Additionally, Erdr1 downregulated STAT3 activity, inhibiting apoptosis via regulation of the Bcl-2 family. Overall, data demonstrate that Erdr1 induced murine melanoma apoptosis through the regulation of Bcl-2 and Bax. These findings suggest that Erdr1 is a novel regulator of apoptosis in melanoma.

Emerging nanomedicine approaches fighting tumor metastasis: animal models, metastasis-targeted drug delivery, phototherapy, and immunotherapy

Nanomedicine approaches may bring new opportunities for tumor metastasis treatment.

Non-canonical Stat3 signaling in cancer

Stat3 is a member of the signal transducers and activators of transcription family and is a known regulator of essential biologic processes including angiogenesis, apoptosis, cell cycle progression, and cell migration. Canonical Stat3-mediated signaling involves tyrosine phosphorylation on specific residues that leads to homodimerization and translocation to the nucleus. For many years it was presumed that most, if not all, of the functions of Stat3, both normal and aberrant, were due to the canonical cytokine and growth factor signaling mechanisms. Recent studies suggest that Stat3 functions through alternate non-canonical pathways to bring about some of these biological functions both in normal cells as well as during cancer development and progression. A number of studies have now shown that Stat3 has a function in mitochondria and that unphosphorylated Stat3 (uStat3) can also function as a transcription factor broadening the potential mechanisms involved in Stat3 action. In this review article, we discuss these two main non-canonical functions of Stat3 and their potential roles in oncogenesis. Given the many facets of Stat3 signaling, additional comprehensive investigations are required to fully understand the role of non-canonical Stat3 signaling in cancer and whether these pathways can be targeted for cancer prevention and treatment. © 2015 Wiley Periodicals, Inc.

IL-6 Inhibits Starvation-induced Autophagy via the STAT3/Bcl-2 Signaling Pathway

IL-6, a pleiotropic cytokine, has been investigated for its role in regulating autophagy. Yet, its mechanism of action remains unclear. Here, we show that IL-6 exerted anti-autophagic effects on U937 cells through the STAT3 signaling pathway in vitro. The addition of IL-6 to starved U937 cells significantly activated the phosphorylation level of STAT3 (p-STAT3) at Tyr705 and reduced the protein levels of microtubule-associated protein 1 light chain 3 of type II (LC3-II) and Beclin 1. By immunoblotting, we also observed a positive correlation between the p-STAT3 level and Bcl-2 level. Furthermore, treatment with a STAT3 inhibitor, LLL12, or overexpression of a mutant form, STAT3Y705F, reversed the inhibitory effect of IL-6 on autophagy. Knockdown of Beclin 1 or Atg14 by siRNA and over-expression of Beclin 1 indicated the involvement of class III PI3K complex in IL-6-mediated inhibition of autophagy. Taken together, these data indicate that IL-6 inhibits starvation-induced autophagy and that p-STAT3 mediates the signal transduction from IL-6 to downstream proteins including Bcl-2 and Beclin1.

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.

Berberine and Curcumin Target Survivin and STAT3 in Gastric Cancer Cells and Synergize Actions of Standard Chemotherapeutic 5-Fluorouracil

Aberrantly expressed survivin and STAT3 signaling have emerged as major determinants of chemoresistance in gastric cancer. We evaluated effects of potent herbal derivatives curcumin, berberine, and quercetin on STAT3 signaling, survivin expression, and response to 5-fluorouracil (5-FU) treatment in gastric cancer cells (AGS). Cytotoxic and inhibitory effects of berberine, curcumin, and quercetin alone or in combination with 5-FU were examined by MTT assay, and their effect on survivin, STAT3, and the phosphorylated active STAT3 (pSTAT3) expression was examined by western blotting. Effect of these herbal derivatives on STAT3 DNA binding activity was measured by electrophoretic mobility shift assay. Curcumin, berberine, and quercetin effectively downregulated pSTAT3 levels, survivin expression, and gastric cancer cells viability in a dose-dependent manner (with corresponding IC50 values of 40.3μM, 29.2μM and 37.5μM, respectively). Berberine was more effective in inhibiting survivin expression as compared to other herbal agents. 5-FU in combination with berberine or curcumin showed a synergistic inhibition of survivin and STAT3 level resulting in enhanced cell death in gastric cancer cells. Overall, our data suggest use of berberine and curcumin as adjunct therapeutics to overcome chemoresistance during treatment of gastric malignancies.

Apoptotic effects of psiRNA-STAT3 on 4T1 breast cancer cells in vitro

BACKGROUND

The aim of this study was to investigate the effect of a Lipofectamine2000 (Life2000) Transfection Reagent transfected psiRNA-STAT3 plasmid on 4T1 breast cancer cells.

MATERIALS AND METHODS

MTT was used to detect the cell proliferation of breast cancer 4T1 cells at different periods (0h, 6h, 8h, 10h); the cell cycle was assessed by flow cytometry; variation of apoptosis and mitochondrial membrane potential was observed under a fluorescence microscope; immunohistochemical staining was used to determine the expression of caspase-3 and cyclin-D1 protein.

RESULTS

An obvious effect of inhibition to 4T1 cancer cells could be observed at 8h after the psiRNA-STAT3 was transfected. Typical alterations of apoptotic morphological features were visible in the psiRNA-STAT3 treatment group. Mitochondrial membrane potential decreased significantly, the number of cells was increased in G0/G1 phase, and the number of cells was decreased in S phase, and the data were statistically significant (p<0.05), compared with the Scramble and Mock groups. Expression of caspase-3 protein was increased significantly, while that of cyclin D1 was significantly decreased.

CONCLUSIONS

Life2000 transfected psiRNA-STAT3 plasmid can inhibit 4T1 tumor cell proliferation and promote apoptosis of 4T1 tumor cells, which process depends on the regulation of expression of cyclin D1 and caspase-3 protein.

STAT3-Mediated Metabolic Reprograming in Cellular Transformation and Implications for Drug Resistance

Signal transducer and activator of transcription (STAT)3 mediates the signaling downstream of cytokine and growth factor receptors, regulating the expression of target genes. It is constitutively phosphorylated on tyrosine (Y-P) in many tumors, where its transcriptional activity can induce a metabolic switch toward aerobic glycolysis and down-regulate mitochondrial activity, a prominent metabolic feature of most cancer cells, correlating with reduced production of ROS, delayed senescence, and protection from apoptosis. STAT3 can, however, also localize to mitochondria, where its serine-phosphorylated (S-P) form preserves mitochondrial oxidative phosphorylation and controls the opening of the mitochondrial permeability transition pore, also promoting survival and resistance to apoptosis in response to specific signals/oncogenes such as RAS. Thus, downstream of different signals, both nuclear, Y-P STAT3, and mitochondrial, S-P STAT3, can act by promoting cell survival and reducing ROS production. Here, we discuss these properties in the light of potential connections between STAT3-driven alterations of mitochondrial metabolism and the development of drug resistance in cancer patients.

Nifuroxazide induces apoptosis and impairs pulmonary metastasis in breast cancer model

Breast carcinoma is the most common female cancer with considerable metastatic potential. Signal transducers and activators of the transcription 3 (Stat3) signaling pathway is constitutively activated in many cancers including breast cancer and has been validated as a novel potential anticancer target. Here, we reported our finding with nifuroxazide, an antidiarrheal agent identified as a potent inhibitor of Stat3. The potency of nifuroxazide on breast cancer was assessed in vitro and in vivo. In this investigation, we found that nifuroxazide decreased the viability of three breast cancer cell lines and induced apoptosis of cancer cells in a dose-dependent manner. In addition, western blot analysis demonstrated that the occurrence of its apoptosis was associated with activation of cleaved caspases-3 and Bax, downregulation of Bcl-2. Moreover, nifuroxazide markedly blocked cancer cell migration and invasion, and the reduction of phosphorylated-Stat3^Tyr705, matrix metalloproteinase (MMP) MMP-2 and MMP-9 expression were also observed. Furthermore, in our animal experiments, intraperitoneal administration of 50 mg/kg/day nifuroxazide suppressed 4T1 tumor growth and blocked formation of pulmonary metastases without detectable toxicity. Meanwhile, histological and immunohistochemical analyses revealed a decrease in Ki-67-positive cells, MMP-9-positive cells and an increase in cleaved caspase-3-positive cells upon nifuroxazide. Notably, nifuroxazide reduced the number of myeloid-derived suppressor cell in the lung. Our data indicated that nifuroxazide may potentially be a therapeutic agent for growth and metastasis of breast cancer.

Bcl-2 family proteins in breast development and cancer: could Mcl-1 targeting overcome therapeutic resistance?

Apoptosis, cell death executed by caspases, is essential to normal breast development and homeostasis. Pro-apoptotic and anti-apoptotic signals are tightly regulated in normal breast epithelial cells. Dysregulation of this balance is required for breast tumorigenesis and increases acquired resistance to treatments, including molecularly targeted therapies, radiation and chemotherapies. The pro-apoptotic or anti-apoptotic Bcl-2 family members interact with each other to maintain mitochondrial integrity and regulate cellular commitment to apoptosis. Among the anti-apoptotic Bcl-2 family members, Mcl-1 is uniquely regulated by numerous oncogenic signaling pathways. This review will focus on the role of Bcl-2 family proteins in normal breast development, breast tumorigenesis and acquired resistance to breast cancer treatment strategies, while highlighting Mcl-1 as a promising target to improve breast cancer tumor cell killing.

Ponicidin induces apoptosis via JAK2 and STAT3 signaling pathways in gastric carcinoma

Ponicidin has a variety of biological effects such as immunoregulatory and anti-inflammatory functions as well as anti-viral functions especially in the upper respiratory tract infection. This study was aimed to elucidate the antitumor effect of ponicidin in gastric carcinoma MKN28 cells and the possible molecular mechanism involved. Cell viability was measured by the Cell Count Kit-8 (CCK8). Cell apoptosis was assessed by flow cytometry as well as cell cycle and reactive oxygen species (ROS) analysis. Western blot analysis was used to detect the active form of caspase-3 as well as Bax and B-cell lymphoma-2 (Bcl-2) expressions after cells were treated with different concentrations of ponicidin. The results revealed that ponicidin could inhibit the growth of MKN28 cells significantly in both a time- and dose-dependent manner. The cell cycle was blocked and ROS generation was increased after the cells were treated with ponicidin. Bcl-2 expression was down-regulated remarkably while Bax expression and the active form of caspase-3 were increased after apoptosis occurred. We therefore conclude that ponicidin exhibited significant growth inhibition of gastric carcinoma cell line MKN28 and induced apoptosis of MKN28 cells via the signaling pathway regulated by Janus kinase 2 (JAK2) and signal transducers and activators of transcription 3 (STAT3). Ponicidin may serve as a potential therapeutic agent for gastric carcinoma.

Synergistic antiproliferative effects of methotrexate-loaded smart silica nanocomposites in MDA-MB-231 breast cancer cells

In this study, the ability of methotrexate (MTX)-loaded stimuli-responsive novel silica nanocomposites (MSNs) (with mean diameter of ± 60 nm) in the induction of apoptosis, and change in the Bax/Bcl-2 mRNA levels, were investigated. MTT assay and RT -PCR analysis were performed on MDA-MB-231 breast cancer cells, to evaluate their anti-proliferative, apoptotic and anti-apoptotic effects. MTX-loaded MSNs caused marked decrease in the percentage of viable cells, with a significant down-regulation in the level of expression of the anti-apoptotic gene (Bcl-2), and up-regulation in the apoptotic gene (Bax). MTX-loaded MSNs increased the efficacy of the chemotherapeutic agents in the inhibition of cell proliferation and induction of apoptosis.

Different protein expression associated with chemotherapy response in oropharyngeal cancer according to HPV status

BACKGOUND

Oropharyngeal cancer (OPC) associated with human papilloma virus (HPV OPC) shows better treatment outcomes than non-HPV OPC. We investigated the expression of p53, β-tubulin, bcl-2 and ERCC 1, which are well-known biomarkers to predict the chemotherapy response, according to HPV status in OPC patients.

METHODS

Patients who treated with at least 2 cycles of induction chemotherapy followed by concurrent chemoradiotherapy for locally advanced oropharyngeal cancer were reviewed. HPV PCR and immunohistochemical stain was done in paraffin embedded tumor tissue and evaluated the relation with the chemotherapy response and survival outcomes according to HPV status.

RESULTS

Seventy-four patients were enrolled for this study and all patients received induction chemotherapy with docetaxel, 5-FU and cisplatin. After induction chemotherapy, complete response (CR) was shown in 22 patients (30%) and partial response (PR) in 46 patients (62%). HPV + was detected in 21 patients (28%), while 35 patients (47%) showed p16+ expression by IHC analysis. p16 positive patients showed better overall response, PFS and OS than p16 negative patients. p53 and class III beta-tubulin expression were significantly higher in HPV- and p16- than HPV + and p16+ patients. Conversely, bcl-2 expression was greater in HPV + or p16+ than HPV- or p16- patients. ERCC1 expression did not differ significantly according to HPV status. In multivariate analyses, early T stage (p = 0.036) and good PS (PS 0) (p = 0.029) showed a better 3Y-PFS rate, and low p53 expression (p = 0.012) and complete response after induction chemotherapy (p = 0.026) were highly associated with 3Y-OS rate. Low expression of p53 and p16 positive patients showed significantly prolonged OS than others (p = 0.010).

CONCLUSION

P53, class III beta-tubulin and bcl-2 were differently expressed in OPC according to HPV status and present study suggested the underlying mechanism of better response to chemotherapy in case of HPV OPC than non-HPV OPC. Among these biomarkers, p53 is the strongest prognostic marker in OPC and p53 in addition to p16 support the rationale to study of de-escalation strategy for OPC.