Inhibition of p-STAT3 enhances IFN-alpha efficacy against metastatic melanoma in a murine model

Mutual regulations between Toxoplasma gondii and type I interferon

In the decades since the discovery, Type I interferon (IFN-I) has been intensively studied for their antiviral activity. However, increasing evidences suggest that it may also play an important role in the infection of Toxoplasma gondii, a model organism for intracellular parasites. Recent studies demonstrated that the induction of IFN-I by the parasite depends on cell type, strain genotype, and mouse strain. IFN-I can inhibit the proliferation of T. gondii, but few studies showed that it is beneficial to the growth of the parasite. Meanwhile, T. gondii also can secrete proteins that impact the pathway of IFN-I production and downstream induced interferon-stimulated genes (ISGs) regulation, thereby escaping immune destruction by the host. This article reviews the major findings and progress in the production, function, and regulation of IFN-I during T. gondii infection, to thoroughly understand the innate immune mechanism of T. gondii infection, which provides a new target for subsequent intervention and treatment.

The complementary roles of STAT3 and STAT1 in cancer biology: insights into tumor pathogenesis and therapeutic strategies

STATs are a family of transcription factors that regulate many critical cellular processes such as proliferation, apoptosis, and differentiation. Dysregulation of STATs is frequently observed in tumors and can directly drive cancer pathogenesis. STAT1 and STAT3 are generally viewed as mediating opposite roles in cancer development, with STAT1 suppressing tumorigenesis and STAT3 promoting oncogenesis. In this review, we investigate the specific roles of STAT1 and STAT3 in normal physiology and cancer biology, explore their interactions with each other, and offer insights into therapeutic strategies through modulating their transcriptional activity.

A first-in-human Phase I trial of the oral p-STAT3 inhibitor WP1066 in patients with recurrent malignant glioma

Aim: To ascertain the maximum tolerated dose (MTD)/maximum feasible dose (MFD) of WP1066 and p-STAT3 target engagement within recurrent glioblastoma (GBM) patients. Patients & methods: In a first-in-human open-label, single-center, single-arm 3 + 3 design Phase I clinical trial, eight patients were treated with WP1066 until disease progression or unacceptable toxicities. Results: In the absence of significant toxicity, the MFD was identified to be 8 mg/kg. The most common adverse event was grade 1 nausea and diarrhea in 50% of patients. No treatment-related deaths occurred; 6 of 8 patients died from disease progression and one was lost to follow-up. Of 8 patients with radiographic follow-up, all had progressive disease. The longest response duration exceeded 3.25 months. The median progression-free survival (PFS) time was 2.3 months (95% CI: 1.7 months-NA months), and 6-month PFS (PFS6) rate was 0%. The median overall survival (OS) rate was 25 months (95% CI: 22.5 months-NA months), with an estimated 1-year OS rate of 100%. Pharmacokinetic (PK) data demonstrated that at 8 mg/kg, the T1/2 was 2-3 h with a dose dependent increase in the Cmax. Immune monitoring of the peripheral blood demonstrated that there was p-STAT3 suppression starting at a dose of 1 mg/kg. Conclusion: Immune analyses indicated that WP1066 inhibited systemic immune p-STAT3. WP1066 had an MFD identified at 8 mg/kg which is the target allometric dose based on prior preclinical modeling in combination with radiation therapy and a Phase II study is being planned for newly diagnosed MGMT promoter unmethylated glioblastoma patients.

The Network of Cytokines in Brain Metastases

Brain metastases are the most common of all intracranial tumors and a major cause of death in patients with cancer. Cytokines, including chemokines, interferons, interleukins, lymphokines, and tumor necrosis factors are key regulators in the formation of brain metastases. They regulate the infiltration of different cellular subsets into the tumor microenvironment and affect the therapeutic outcomes in patients. Elucidating the cancer cell-cytokine interactions in the setting of brain metastases is crucial for the development of more accurate diagnostics and efficacious therapies. In this review, we focus on cytokines that are found in the tumor microenvironment of brain metastases and elaborate on their trends of expression, regulation, and roles in cellular recruitment and tumorigenesis. We also explore how cytokines can alter the anti-tumor response in the context of brain metastases and discuss ways through which cytokine networks can be manipulated for diagnosis and treatment.

Using Preclinical Data to Design Combination Clinical Trials of Radiation Therapy and Immunotherapy

Immunotherapies are rapidly entering the clinic as approved treatments for diverse cancer pathologies. Radiation therapy is an integral partner in cancer therapy, commonly as part of complicated multimodality approaches that optimize patient outcomes. Preclinical studies have demonstrated that the success of radiation therapy in tumor control is due in part to immune mechanisms, and that outcomes following radiation therapy can be improved through combination with a range of immunotherapies. However, preclinical models of cancer are very different from patient tumors, and the way these preclinical tumors are treated is often very different from standard of care treatment of patients. This review examines the preclinical and clinical data for the role of the immune system in radiation therapy outcomes, and how to integrate preclinical findings into clinical trials, using ongoing studies as examples.

Intestinal epithelial HMGB1 inhibits bacterial infection via STAT3 regulation of autophagy

Extracellular HMGB1 (high mobility group box 1) is considered as a damage-associated molecular pattern protein. However, little is known about its intracellular role. We studied the mechanism whereby intestinal epithelial HMGB1 contributes to host defense, using cell culture, colonoids, conditional intestinal epithelial HMGB1-knockout mice with Salmonella-colitis, il10-/- mice, and human samples. We report that intestinal HMGB1 is an important contributor to host protection from inflammation and infection. We identified a physical interaction between HMGB1 and STAT3. Lacking intestinal epithelial HMGB1 led to redistribution of STAT3 and activation of STAT3 post bacterial infection. Indeed, Salmonella-infected HMGB1-deficient cells exhibited less macroautophagy/autophagy due to decreased expression of autophagy proteins and transcriptional repression by activated STAT3. Then, increased p-STAT3 and extranuclear STAT3 reduced autophagic responses and increased inflammation. STAT3 inhibition restored autophagic responses and reduced bacterial invasion in vitro and in vivo. Moreover, low level of HMGB1 was correlated with reduced nuclear STAT3 and enhanced p-STAT3 in inflamed intestine of il10-/- mice and inflammatory bowel disease (IBD) patients. We revealed that colonic epithelial HMGB1 was directly involved in the suppression of STAT3 activation and the protection of intestine from bacterial infection and injury. Abbreviations: ATG16L1: autophagy-related 16-like 1 (S. cerevisiae); DAMP: damage-associated molecular pattern; HBSS: Hanks balanced salt solution; HMGB1: high mobility group box 1; IBD: inflammatory bowel disease; IL1B/Il-1β: interleukin 1 beta; IL10: interleukin 10; IL17/IL-17: interleukin 17; MEFs: mouse embryonic fibroblasts; STAT3: signal transducer and activator of transcription 3; TLR: toll-like receptor; TNF/TNF-α: tumor necrosis factor.

Thymoquinone Enhances the Effect of Gamma Knife in B16-F10 Melanoma Through Inhibition of Phosphorylated STAT3

BACKGROUND

Patients with brain metastasis from melanoma have a dismal prognosis with poor survival time. Gamma Knife (GK) is an effective treatment to control brain metastasis from melanoma. Thymoquinone (TQ) has emerged as a potential therapeutic option due to its antiproliferative effects on various cancers. The purpose of the study was to assess the effect of GK on B16-F10 melanoma cells in vitro and intracerebral melanoma in vivo, and its synergistic effect in combination with TQ.

METHODS

The effects of GK and combination treatment of GK and TQ were studied on B16-F10 melanoma cells by evaluating cytotoxicity with an adenosine triphosphate assay, apoptosis by acridine orange staining, and genotoxicity by comet assay. Western blot analysis was performed to investigate the expression of STAT3, p-STAT3 (Tyr705), JAK2, p-JAK2, caspase-3, Bax, Bcl-2, survivin, and β-actin. Expression of inflammatory cytokines was assessed by enzyme-linked immunosorbent assay. GK alone and in combination with TQ was assessed in an established intracerebral melanoma tumor in mice.

RESULTS

The effects of GK on cytotoxicity, genotoxicity, and apoptosis were enhanced by TQ in B16-F10 melanoma cells. GK induced apoptosis through inhibition of p-STAT3 expression, which in turn regulated pro- and antiapoptotic proteins such as caspase-3, Bax, Bcl-2, and survivin. Adding TQ to GK irradiation further enhanced this apoptotic effect of GK irradiation. GK was shown to reduce the levels of tumor-related inflammatory cytokines in B16-F10 melanoma cells. This effect was more pronounced when TQ was added to GK irradiation. GK with 15 Gy increased the survival of mice with intracerebral melanoma compared with untreated mice. However, despite the additive effect of TQ in addition to GK irradiation on B16-F10 melanoma cells in vitro, TQ did not add any significant survival benefit to GK treatment in mice with intracerebral melanoma.

CONCLUSIONS

Our findings suggest that TQ would be a potential therapeutic agent in addition to GK to enhance the antitumor effect of irradiation. Further studies are required to support our findings.

A Multifunctional Biomimetic Nanoplatform for Relieving Hypoxia to Enhance Chemotherapy and Inhibit the PD-1/PD-L1 Axis

Hypoxia is reported to participate in tumor progression, promote drug resistance, and immune escape within tumor microenvironment, and thus impair therapeutic effects including the chemotherapy and advanced immunotherapy. Here, a multifunctional biomimetic core-shell nanoplatform is reported for improving synergetic chemotherapy and immunotherapy. Based on the properties including good biodegradability and functionalities, the pH-sensitive zeolitic imidazolate framework 8 embedded with catalase and doxorubicin constructs the core and serves as an oxygen generator and drug reservoir. Murine melanoma cell membrane coating on the core provides tumor targeting ability and elicits an immune response due to abundance of antigens. It is demonstrated that this biomimetic core-shell nanoplatform with oxygen generation can be partial to accumulate in tumor and downregulate the expression of hypoxia-inducible factor 1α, which can further enhance the therapeutic effects of chemotherapy and reduce the expression of programmed death ligand 1 (PD-L1). Combined with immune checkpoints blockade therapy by programmed death 1 (PD-1) antibody, the dual inhibition of the PD-1/PD-L1 axis elicits significant immune response and presents a robust effect in lengthening tumor recurrent time and inhibiting tumor metastasis. Consequently, the multifunctional nanoplatform provides a potential strategy of synergetic chemotherapy and immunotherapy.

The role of STAT3 in leading the crosstalk between human cancers and the immune system

The development and progression of human cancers are continuously and dynamically regulated by intrinsic and extrinsic factors. As a converging point of multiple oncogenic pathways, signal transducer and activator of transcription 3 (STAT3) is constitutively activated both in tumor cells and tumor-infiltrated immune cells. Activated STAT3 persistently triggers tumor progression through direct regulation of oncogenic gene expression. Apart from its oncogenic role in regulating gene expression in tumor cells, STAT3 also paves the way for human cancer growth through immunosuppression. Activated STAT3 in immune cells results in inhibition of immune mediators and promotion of immunosuppressive factors. Therefore, STAT3 modulates the interaction between tumor cells and host immunity. Accumulating evidence suggests that targeting STAT3 may enhance anti-cancer immune responses and rescue the suppressed immunologic microenvironment in tumors. Taken together, STAT3 has emerged as a promising target in cancer immunotherapy.

STAT3 Decoy ODN Therapy for Cancer

As an oncogene, over-activated signal transducer and activator of transcription 3 (STAT3) has been detected in many tumors. STAT3 controls cell differentiation, proliferation, and survival, and is associated with angiogenesis and immune dysfunction during tumorigenesis. Double-stranded decoy oligodeoxynucleotide (ODN) targeting over-activated STAT3 in tumor cells have shown significant antitumor efficiency. Here, we describe the materials and methods involved in STAT3 decoy ODN therapy for cancer including both the antitumor effect directly and immunotherapy indirectly.

The role of STAT3 in tumor-mediated immune suppression

The role of tumor-induced immune modulation in cancer progression is currently a focus of investigation. The signal transducer and activator of transcription 3 (STAT3) is an established molecular hub of immunosuppression, and its signaling pathways are classically overactivated within malignancies. This article will review STAT3 operational mechanisms within the immune system and the tumor microenvironment, with a focus on therapeutic strategies that may impact outcomes for patients with cancer.

STAT3 Single Nucleotide Polymorphism rs4796793 SNP Does Not Correlate with Response to Adjuvant IFNα Therapy in Stage III Melanoma Patients

Interferon alpha (IFNα) is approved for adjuvant treatment of stage III melanoma in Europe and the US. Its clinical efficacy, however, is restricted to a subpopulation of patients while side effects occur in most of treated patients. Thus, the identification of predictive biomarkers would be highly beneficial to improve the benefit to risk ratio. In this regard, STAT3 is important for signaling of the IFNα receptor. Moreover, the STAT3 single-nucleotide polymorphism (SNP) rs4796793 has recently been reported to be associated with IFNα sensitivity in metastatic renal cell carcinoma. To translate this notion to melanoma, we scrutinized the impact of rs4796793 functionally and clinically in this cancer. Interestingly, melanoma cells carrying the minor allele of rs4796793 were the most sensitive to IFNα in vitro. However, we did not detect a correlation between SNP genotype and STAT3 mRNA expression for either melanoma cells or for peripheral blood lymphocytes. Next, we analyzed the impact of rs4796793 on the clinical outcome of 259 stage III melanoma patients of which one-third had received adjuvant IFNα treatment. These analyses did not reveal a significant association between the STAT3 rs4796793 SNP and patients’ progression free or overall survival when IFNα treated and untreated patients were compared. In conclusion, STAT3 rs4796793 SNP is no predictive marker for the efficacy of adjuvant IFNα treatment in melanoma patients.

Drug delivery nanoparticles in skin cancers

Nanotechnology involves the engineering of functional systems at nanoscale, thus being attractive for disciplines ranging from materials science to biomedicine. One of the most active research areas of the nanotechnology is nanomedicine, which applies nanotechnology to highly specific medical interventions for prevention, diagnosis, and treatment of diseases, including cancer disease. Over the past two decades, the rapid developments in nanotechnology have allowed the incorporation of multiple therapeutic, sensing, and targeting agents into nanoparticles, for detection, prevention, and treatment of cancer diseases. Nanoparticles offer many advantages as drug carrier systems since they can improve the solubility of poorly water-soluble drugs, modify pharmacokinetics, increase drug half-life by reducing immunogenicity, improve bioavailability, and diminish drug metabolism. They can also enable a tunable release of therapeutic compounds and the simultaneous delivery of two or more drugs for combination therapy. In this review, we discuss the recent advances in the use of different types of nanoparticles for systemic and topical drug delivery in the treatment of skin cancer. In particular, the progress in the treatment with nanocarriers of basal cell carcinoma, squamous cell carcinoma, and melanoma has been reported.

Therapeutic modulators of STAT signalling for human diseases

The signal transducer and activator of transcription (STAT) proteins have important roles in biological processes. The abnormal activation of STAT signalling pathways is also implicated in many human diseases, including cancer, autoimmune diseases, rheumatoid arthritis, asthma and diabetes. Over a decade has passed since the first inhibitor of a STAT protein was reported and efforts to discover modulators of STAT signalling as therapeutics continue. This Review discusses the outcomes of the ongoing drug discovery research endeavours against STAT proteins, provides perspectives on new directions for accelerating the discovery of drug candidates, and highlights the noteworthy candidate therapeutics that have progressed to clinical trials.

Regulation of HGF expression by ΔEGFR-mediated c-Met activation in glioblastoma cells

The hepatocyte growth factor receptor (c-Met) and a constitutively active mutant of the epidermal growth factor receptor (ΔEGFR/EGFRvIII) are frequently overexpressed in glioblastoma (GBM) and promote tumorigenesis. The mechanisms underlying elevated hepatocyte growth factor (HGF) production in GBM are not understood. We found higher, coordinated mRNA expression levels of HGF and c-Met in mesenchymal (Mes) GBMs, a subtype associated with poor treatment response and shorter overall survival. In an HGF/c-Met-dependent GBM cell line, HGF expression declined upon silencing of c-Met using RNAi or by inhibiting its activity with SU11274. Silencing c-Met decreased anchorage-independent colony formation and increased the survival of mice bearing intracranial GBM xenografts. Consistent with these findings, c-Met activation by ΔEGFR also elevated HGF expression, and the inhibition of ΔEGFR with AG1478 reduced HGF levels. Interestingly, c-Met expression was required for ΔEGFR-mediated HGF production, anchorage-independent growth, and in vivo tumorigenicity, suggesting that these pathways are coupled. Using an unbiased mass spectrometry-based screen, we show that signal transducer and activator of transcription 3 (STAT3) Y705 is a downstream target of c-Met signaling. Suppression of STAT3 phosphorylation with WP1193 reduced HGF expression in ΔEGFR-expressing GBM cells, whereas constitutively active STAT3 partially rescued HGF expression and colony formation in c-Met knockdown cells expressing ΔEGFR. These results suggest that the c-Met/HGF signaling axis is enhanced by ΔEGFR through increased STAT3-dependent HGF expression and that targeting c-Met in Mes GBMs may be an important strategy for therapy.

Targeting blockage of STAT3 in hepatocellular carcinoma cells augments NK cell functions via reverse hepatocellular carcinoma-induced immune suppression

STAT3 is an important transcriptional factor for cell growth, differentiation, and apoptosis. Although evidence suggests a positive role for STAT3 in cancer, the inhibitory effects of tumor STAT3 on natural killer (NK) cell functions in human hepatocellular carcinoma are unclear. In this study, we found that blocking STAT3 in hepatocellular carcinoma cells enhanced NK-cell antitumor function. In the case of STAT3-blocked hepatocellular carcinoma cells, NKG2D ligands were upregulated, which promoted recognition by NK cells. Importantly, the cytokine profile of hepatocellular carcinoma cells was altered; in particular, TGF-β and interleukin 10 (IL-10) expression was reduced, and type I interferon (IFN) was induced, thus facilitating NK-cell activation. Indeed, the cytotoxicity of NK cells treated with supernatant from STAT3-blocked hepatocellular carcinoma cells was augmented, with a concomitant elevation of molecules associated with NK cytolysis. Further experiments confirmed that the recovery of NK cells depended on the downregulation of TGF-β and upregulation of type I IFN derived from STAT3-blocked hepatocellular carcinoma cells. These findings demonstrated a pivotal role for STAT3 in hepatocellular carcinoma-mediated NK-cell dysfunction, and highlighted the importance of STAT3 blockade for hepatocellular carcinoma immunotherapy, which could restore NK-cell cytotoxicity in addition to its direct influence on tumor cells.

A membrane penetrating peptide aptamer inhibits STAT3 function and suppresses the growth of STAT3 addicted tumor cells

Cancer cells are characterized by the aberrant activation of signaling pathways governing proliferation, survival, angiogenesis, migration and immune evasion. These processes are partially regulated by the transcription factor STAT3. This factor is inappropriately activated in diverse tumor types. Since tumor cells can become dependent on its persistent activation, STAT3 is a favorable drug target. Here, we describe the functional characterization of the recombinant STAT3 inhibitor, rS3-PA. This inhibitor is based on a 20 amino acid peptide which specifically interacts with the dimerization domain of STAT3. It is integrated into a thioredoxin scaffold and fused to a protein transduction domain. Protein gel blot and immunofluorescence analyses showed that rS3-PA is efficiently taken up by cells via an endocytosis independent mechanism. Intracellularly, it reduces the phosphorylation of STAT3 and enhances its degradation. This leads to the downregulation of STAT3 target gene expression on the mRNA and protein levels. Subsequently, tumor cell proliferation, survival and migration and the induction of angiogenesis are inhibited. In contrast, normal cells remain unaffected. Systemic administration of rS3-PA at doses of 7.5 mg/kg reduced P-STAT3 levels and significantly inhibited tumor growth up to 35% in a glioblastoma xenograft mouse model.

Applications of nanotechnology for melanoma treatment, diagnosis, and theranostics

Melanoma is the most aggressive type of skin cancer and has very high rates of mortality. An early stage melanoma can be surgically removed, with a survival rate of 99%. However, metastasized melanoma is difficult to cure. The 5-year survival rates for patients with metastasized melanoma are still below 20%. Metastasized melanoma is currently treated by chemotherapy, targeted therapy, immunotherapy and radiotherapy. The outcome of most of the current therapies is far from optimistic. Although melanoma patients with a mutation in the oncogene v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) have an initially higher positive response rate to targeted therapy, the majority develop acquired drug resistance after 6 months of the therapy. To increase treatment efficacy, early diagnosis, more potent pharmacological agents, and more effective delivery systems are urgently needed. Nanotechnology has been extensively studied for melanoma treatment and diagnosis, to decrease drug resistance, increase therapeutic efficacy, and reduce side effects. In this review, we summarize the recent progress on the development of various nanoparticles for melanoma treatment and diagnosis. Several common nanoparticles, including liposome, polymersomes, dendrimers, carbon-based nanoparticles, and human albumin, have been used to deliver chemotherapeutic agents, and small interfering ribonucleic acids (siRNAs) against signaling molecules have also been tested for the treatment of melanoma. Indeed, several nanoparticle-delivered drugs have been approved by the US Food and Drug Administration and are currently in clinical trials. The application of nanoparticles could produce side effects, which will need to be reduced so that nanoparticle-delivered drugs can be safely applied in the clinical setting.

Development of novel molecular probes of the Rio1 atypical protein kinase

The RIO kinases are essential protein factors required for the synthesis of new ribosomes in eukaryotes. Conserved in archaeal organisms as well, RIO kinases are among the most ancient of protein kinases. Their exact molecular mechanisms are under investigation and progress of this research would be significantly improved with the availability of suitable molecular probes that selectively block RIO kinases. RIO kinases contain a canonical eukaryotic protein kinase fold, but also display several unusual structural features that potentially create opportunity for the design of selective inhibitors. In an attempt to identify structural leads to target the RIO kinases, a series of pyridine caffeic acid benzyl amides (CABA) were tested for their ability to inhibit the autophosphorylation activity of Archeaoglobus fulgidus Rio1 (AfRio1). Screening of a small library of CABA molecules resulted in the identification of four compounds that measurably inhibited AfRio1 activity. Additional biochemical characterization of binding and inhibition activity of these compounds demonstrated an ATP competitive inhibition mode, and allowed identification of the functional groups that result in the highest binding affinity. In addition, docking of the compound to the structure of Rio1 and determination of the X-ray crystal structure of a model compound (WP1086) containing the desired functional groups allowed detailed analysis of the interactions between these compounds and the enzyme. Furthermore, the X-ray crystal structure demonstrated that these compounds stabilize an inactive form of the enzyme. Taken together, these results provide an important step in identification of a scaffold for the design of selective molecular probes to study molecular mechanisms of Rio1 kinases in vitro and in vivo. In addition, it provides a rationale for the future design of potent inhibitors with drug-like properties targeting an inactive form of the enzyme. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).

Role of the systemic immune system in brain metastasis

Metastatic disease in the central nervous system (CNS) is a cause of increasing mortality amongst cancer patients. As with other types of cancer, cells of the systemic immune system play a range of important roles in the development of metastatic lesions in the CNS, both repressing and promoting tumour growth. Recent advances in immunotherapy have changed the emphasis in cancer treatment away from conventional chemotherapy and radiotherapy for certain tumour types. Despite this, our understanding of systemic immune system involvement in CNS metastases remains poor. The blood-brain barrier prevents the majority of diagnostic and therapeutic agents from crossing into the brain parenchyma until the late stages of metastatic disease. Thus, the development of immunotherapy for CNS pathologies is particularly desirable. This review draws together our current understanding in the relationships between CNS metastases and circulating systemic immune cells. We discuss the roles that circulating systemic immune cells may play in the homing of metastatic cells to the perivascular space, and the pro-metastatic and antagonistic roles that infiltrating systemic immune cells may play at sites of metastasis. This article is part of a Special Issue entitled 'Neuroinflammation in neurodegeneration and neurodysfunction'.

YB-1 suppression induces STAT3 proteolysis and sensitizes renal cancer to interferon-α

Renal cell carcinoma (RCC) accounts for 80-95 % of kidney tumors, and approximately 30 % of RCC patients have metastatic disease at diagnosis. Conventional chemotherapy is not effective in patients with metastatic RCC (MRCC); therefore, immunotherapy with interferon-α (IFN-α) has been employed to improve survival. However, the response rate of MRCC to IFN-α therapy is low. We previously reported that a signal transducer and activator 3 (STAT3) polymorphism was a useful diagnostic marker to predict the response to IFN-α therapy in patients with MRCC. Therefore, we hypothesized the inhibition of STAT3 in the addition of IFN-α therapy might be useful. Moreover, the blockage of STAT3 itself has been reported to enhance the antitumor effects. However, because IFN-α is thought to elicit its therapeutic effect via enhancement of an antitumor immune response mediated by lymphocytes that can be activated by IFN-α administrations, it is probable that the suppression of STAT3 in vivo relates to autoimmune disorders. In the present study, we found Y-box binding protein-1 (YB-1) was poorly expressed in T lymphocytes, as compared with cancer tissues. YB-1 was reported to have an important effect on the STAT3 pathway. Suppression of STAT3 by YB-1 inhibition did not seem to enhance the potential risk for autoimmune disorders. Moreover, we found sensitivity to IFN-α was increased by YB-1 suppression, and this suppression did not down-regulate IFN-α activation of T lymphocytes.

Tim-3 expression in cervical cancer promotes tumor metastasis

BACKGROUND

T cell immunoglobulin mucin-3 (Tim-3) has been identified as a negative regulator of anti-tumor immunity. Recent studies highlight the important role of Tim-3 in the CD8(+) T cell exhaustion that takes place in both human and animal cancer models. However, the nature of Tim-3 expression in the tumor cell and the mechanism by which it inhibits anti-tumor immunity are unclear. This present study aims to determine Tim-3 is expressed in cervical cancer cells and to evaluate the role of Tim-3 in cervical cancer progression.

METHODOLOGY

A total of 85 cervical tissue specimens including 43 human cervical cancer, 22 cervical intraepithelial neoplasia (CIN) and 20 chronic cervicitis were involved. Tim-3 expression in tumor cells was detected and was found to correlate with clinicopathological parameters. Meanwhile, expression of Tim-3 was assessed by RT-PCR, Western Blot and confocal microscopy in cervical cancer cell lines, HeLa and SiHa. The migration and invasion potential of Hela cells was evaluated after inhibiting Tim-3 expression by ADV-antisense Tim-3.

CONCLUSIONS

We found that Tim-3 was expressed at a higher level in the clinical cervical cancer cells compared to the CIN and chronic cervicitis controls. We supported this finding by confirming the presence of Tim-3 mRNA and protein in the cervical cell lines. Tim-3 expression in tumor cells correlated with clinicopathological parameters. Patients with high expression of Tim-3 had a significant metastatic potential, advanced cancer grades and shorter overall survival than those with lower expression. Multivariate analysis showed that Tim-3 expression was an independent factor for predicting the prognosis of cervical cancer. Significantly, down-regulating the expression of Tim-3 protein inhibited migration and invasion of Hela cells. Our study suggests that the expression of Tim-3 in tumor cells may be an independent prognostic factor for patients with cervical cancer. Moreover, Tim-3 expression may promote metastatic potential in cervical cancers.

Variation in susceptibility of human malignant melanomas to oncolytic vesicular stomatitis virus

BACKGROUND

Vesicular stomatitis virus (VSV) is a novel, anti-cancer therapy that targets cancer cells selectively with defective antiviral responses; however, not all malignant cells are sensitive to the oncolytic effects of VSV. Herein, we have explored the mechanistic determinants of mutant M protein VSV (M51R-VSV) susceptibility in malignant melanoma cells.

METHODS

Cell viability after VSV infection was measured by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) viability assay in a panel of melanoma cell lines. VSV infectability, viral protein synthesis, and viral progeny production were quantified by flow cytometry, (35)S-methionine electrophoresis, and viral plaque assays, respectively. Interferon (IFN) responsiveness was determined using MTS assay after β-IFN pretreatment. Xenografts were established in athymic nude mice and treated with intratumoral M51R-VSV.

RESULTS

Cell viability after M51R-VSV infection at a multiplicity of infection of 10 pfu/mL, 48 hours postinfection) ranged between 0 ± 1% and 59 ± 9% (mean ± standard deviation). Sensitive cell lines supported VSV infection, viral protein synthesis, and viral progeny production. In addition, when pretreated with β-IFN, sensitive cells became resistant to M51R-VSV, suggesting that IFN-mediated antiviral signaling is defective in these cells. In contrast, resistant melanoma cells do not support VSV infection, viral protein synthesis, or viral replication, indicating that antiviral defenses remain intact. In a murine xenograft model, intratumoral M51R-VSV treatment decreased tumor growth relative to controls after 26 days in SK-Mel 5 (-21 ± 19% vs. 2,100 ± 770%; P < .0001) and in SK-Mel 3 (2,000 ± 810% vs. 7,000 ± 3,000%; P = .008) established tumors.

CONCLUSION

M51R-VSV is a viable anti-cancer therapy, but susceptibility varies among melanomas. Future work will exploit specific mechanisms of resistance to expand the therapeutic efficacy of M51R-VSV.

Delivery of interferons and siRNA targeting STAT3 using lentiviral vectors suppresses the growth of murine melanoma

Interferons (IFNs) have been investigated as important cytokines in immunotherapy. The use of IFNs in cancer immunotherapy has had limited success. In this study, IFN genes were delivered into B16 melanoma cells by lentiviral vectors, and their effects on B16 melanoma were comprehensively analyzed. Type II IFN significantly impaired the viability of B16 cells in vitro. Expression of IFNα and IFNβ in B16 cells efficiently suppressed the establishment of inoculated melanoma. However, intratumoral delivery of IFNs alone with lentiviral vectors had no therapeutic effects on established melanoma. To address the lack of response, a lentivector was constructed to simultaneously transfer therapeutic genes and small interfering RNAs (siRNAs). IFNs and siRNA targeting signal transducer and activator of transcription 3 (STAT3), which is a major immune suppressive transcription factor in melanoma, were delivered simultaneously into the tumor milieu. This treatment successfully rescued the response to IFNγ and attenuated the growth of established tumors. This method has the potential to improve the therapeutic effects of IFNs in cancer immunotherapy.

Structurally modified curcumin analogs inhibit STAT3 phosphorylation and promote apoptosis of human renal cell carcinoma and melanoma cell lines

The Janus kinase-2 (Jak2)-signal transducer and activator of transcription-3 (STAT3) pathway is critical for promoting an oncogenic and metastatic phenotype in several types of cancer including renal cell carcinoma (RCC) and melanoma. This study describes two small molecule inhibitors of the Jak2-STAT3 pathway, FLLL32 and its more soluble analog, FLLL62. These compounds are structurally distinct curcumin analogs that bind selectively to the SH2 domain of STAT3 to inhibit its phosphorylation and dimerization. We hypothesized that FLLL32 and FLLL62 would induce apoptosis in RCC and melanoma cells and display specificity for the Jak2-STAT3 pathway. FLLL32 and FLLL62 could inhibit STAT3 dimerization in vitro. These compounds reduced basal STAT3 phosphorylation (pSTAT3), and induced apoptosis in four separate human RCC cell lines and in human melanoma cell lines as determined by Annexin V/PI staining. Apoptosis was also confirmed by immunoblot analysis of caspase-3 processing and PARP cleavage. Pre-treatment of RCC and melanoma cell lines with FLLL32/62 did not inhibit IFN-γ-induced pSTAT1. In contrast to FLLL32, curcumin and FLLL62 reduced downstream STAT1-mediated gene expression of IRF1 as determined by Real Time PCR. FLLL32 and FLLL62 significantly reduced secretion of VEGF from RCC cell lines in a dose-dependent manner as determined by ELISA. Finally, each of these compounds inhibited in vitro generation of myeloid-derived suppressor cells. These data support further investigation of FLLL32 and FLLL62 as lead compounds for STAT3 inhibition in RCC and melanoma.

Induction of cell-cycle arrest and apoptosis in glioblastoma stem-like cells by WP1193, a novel small molecule inhibitor of the JAK2/STAT3 pathway

Glioma stem-like cells (GSCs) may be the initiating cells in glioblastoma (GBM) and contribute to the resistance of these tumors to conventional therapies. Development of novel chemotherapeutic agents and treatment approaches against GBM, especially those specifically targeting GSCs are thus necessary. In the present study, we found that a novel Janus kinase 2/Signal Transducer and Activator of Transcription 3 (JAK2/STAT3) pathway inhibitor (WP1193) significantly decreased the proliferation of established glioma cell lines in vitro and inhibit the growth of glioma in vivo. To test the efficacy of WP1193 against GSCs, we then administrated WP1193 to GSCs isolated and expanded from multiple human GBM tumors. We revealed that WP1193 suppressed phosphorylation of JAK2 and STAT3 with high potency and demonstrated a dose-dependent inhibition of proliferation and neurosphere formation of GSCs. These effects were at least due in part to G1 arrest associated with down-regulation of cyclin D1 and up-regulation of p21( Cip1/Waf-1 ). Furthermore, WP1193 exposure decreased expression of stem cell markers including CD133 and c-myc, and induced cell death in GSCs through apoptosis. Taken together, our data indicate that WP1193 is a potent small molecule inhibitor of the JAK2/STAT3 pathway that shows promise as a therapeutic agent against GBM by targeting GSCs.

Adjuvant therapy: melanoma

With an incidence that is increasing at 2–5% per year, cutaneous melanoma is an international scourge that disproportionately targets young individuals. Despite much research, the treatment of advanced disease is still quite challenging. Immunotherapy with high-dose interferon-α2b or interleukin-2 benefits a select group of patients in the adjuvant and metastatic settings, respectively, with significant attendant toxicity. Advances in the biology of malignant melanoma and the role of immunomodulatory therapy have produced advances that have stunned the field. In this paper, we review the data for the use of interferon-α2b in various dosing ranges, vaccine therapy, and the role of radiotherapy in the adjuvant setting for malignant melanoma. Recent trials in the metastatic setting using anticytoxic T-lymphocyte antigen-4 (anti-CTLA-4) monoclonal antibody therapy and BRAF inhibitor therapy have demonstrated clear benefit with prolongation of survival. Trials investigating combinations of these novel agents with existing immunomodulators are at present underway.

The tumor microenvironment expression of p-STAT3 influences the efficacy of cyclophosphamide with WP1066 in murine melanoma models

Melanoma is a common and deadly tumor that upon metastasis to the central nervous system (CNS) has median survival duration of less than 5 months. Activation of the signal transducer and activator of transcription 3 (STAT3) has been identified as a key mediator that drives the fundamental components of melanoma. We hypothesized that WP1066, a novel inhibitor of STAT3 signaling, would enhance the antitumor activity of cyclophosphamide (CTX) against melanoma, including disease within the CNS. The mechanisms of efficacy were investigated by tumor- and immune-mediated cytotoxic assays, in vivo evaluation of the reduction of regulatory T cells (Tregs) and by determining intratumoral p-STAT3 expression by immunohistochemistry. Combinational therapy of WP1066, with both metronomic and cytotoxic dosing of CTX, was investigated in a model system of systemic and intracerebral melanoma in syngeneic mice. Inhibition of p-STAT3 by WP1066 was enhanced with CTX in a dose-dependent manner. However, in mice with intracerebral melanoma, the greatest therapeutic benefit was seen in animals treated with cytotoxic CTX dosing and WP1066, whose median survival time was 120 days, an increase of 375%, with 57% long-term survivors. This treatment efficacy correlated with p-STAT3 expression levels within the tumor microenvironment. The efficacy of the combination of cytotoxic dosing of CTX with WP1066 is attributed to the direct tumor cytotoxic effects of the agents and has the greatest therapeutic potential for the treatment of CNS melanoma.

Preclinical approaches to study the biology and treatment of brain metastases

Metastatic spread to the central nervous system (CNS) is a common and devastating manifestation of major cancer types. Its incidence is associated with poor prognosis manifested by neurological deterioration leading to diminished quality of life and an extremely short median survival. CNS metastasis is becoming an increasingly important clinical problem. This is especially the case for certain types of cancers for which effective treatments of visceral disease are available. As a result of the present limitations in treating CNS metastases, this manifestation of tumor progression remains an unmet clinical need. Despite its significance, our general understanding of the mechanisms that regulate the brain-metastatic phenotype is currently meager. Both the analysis of mechanistic aspects of brain metastasis and the development of effective treatments necessitate the use of appropriate in vivo models that recapitulate the interaction of the tumor cells with the microenvironment of the brain. Here we review the available preclinical models of CNS metastasis and their use as tools to advance knowledge of the biology of the disease (with the aim of identifying relevant molecular determinants, prognostic biomarkers, and therapeutic targets) as well as examining effective approaches for treatment.

Intratumoral mediated immunosuppression is prognostic in genetically engineered murine models of glioma and correlates to immunotherapeutic responses

PURPOSE

Preclinical murine model systems used for the assessment of therapeutics have not been predictive of human clinical responses, primarily because their clonotypic nature does not recapitulate the heterogeneous biology and immunosuppressive mechanisms of humans. Relevant model systems with mice that are immunologically competent are needed to evaluate the efficacy of therapeutic agents, especially immunotherapeutics.

EXPERIMENTAL DESIGN

Using the RCAS/Ntv-a system, mice were engineered to coexpress platelet-derived growth factor B (PDGF-B) receptor + B-cell lymphoma 2 (Bcl-2) under the control of the glioneuronal specific Nestin promoter. The degree and type of tumor-mediated immunosuppression were determined in these endogenously arising gliomas on the basis of the presence of macrophages and regulatory T cells. The immunotherapeutic agent WP1066 was tested in vivo to assess therapeutic efficacy and immunomodulation.

RESULTS

Ntv-a mice were injected with RCAS vectors to express PDGF-B + Bcl-2, resulting in both low- and high-grade gliomas. Consistent with observations in human high-grade gliomas, mice with high-grade gliomas also developed a marked intratumoral influx of macrophages that was influenced by tumor signal transducer and activator of transduction 3 (STAT3) expression. The presence of intratumoral F4/80 macrophages was a negative prognosticator for long-term survival. In mice coexpressing PDGF-B + Bcl-2that were treated with WP1066, there was 55.5% increase in median survival time (P < 0.01), with an associated inhibition of intratumoral STAT3 and macrophages.

CONCLUSIONS

Although randomization is necessary for including mice in a therapeutic trial, these murine model systems are more suitable for testing therapeutics, especially immunotherapeutics, in the context of translational studies.

Glioma cancer stem cells induce immunosuppressive macrophages/microglia

Macrophages (MΦs)/microglia that constitute the dominant tumor-infiltrating immune cells in glioblastoma are recruited by tumor-secreted factors and are induced to become immunosuppressive and tumor supportive (M2). Glioma cancer stem cells (gCSCs) have been shown to suppress adaptive immunity, but their role in innate immunity with respect to the recruitment and polarization of MΦs/microglia is unknown. The innate immunosuppressive properties of the gCSCs were characterized based on elaborated MΦ inhibitory cytokine-1 (MIC-1), transforming growth factor (TGF-β1), soluble colony-stimulating factor (sCSF), recruitment of monocytes, inhibition of MΦ/microglia phagocytosis, induction of MΦ/microglia cytokine secretion, and the inhibition of T-cell proliferation. The role of the signal transducer and activator of transcription 3 (STAT3) in mediating innate immune suppression was evaluated in the context of the functional assays. The gCSCs produced sCSF-1, TGF-β1, and MIC-1, cytokines known to recruit and polarize the MΦs/microglia to become immunosuppressive. The gCSC-conditioned medium polarized the MΦ/microglia to an M2 phenotype, inhibited MΦ/microglia phagocytosis, induced the secretion of the immunosuppressive cytokines interleukin-10 (IL-10) and TGF-β1 by the MΦs/microglia, and enhanced the capacity of MΦs/microglia to inhibit T-cell proliferation. The inhibition of phagocytosis and the secretion of IL-10 were reversed when the STAT3 pathway was blocked in the gCSCs. The gCSCs modulate innate immunity in glioblastoma by inducing immunosuppressive MΦs/microglia, and this capacity can be reversed by inhibiting phosphorylated STAT3.

Dasatinib reduces FAK phosphorylation increasing the effects of RPI-1 inhibition in a RET/PTC1-expressing cell line

Background

TPC-1 is a papillary thyroid carcinoma (PTC)-derived cell line that spontaneously expresses the oncogene RET/PTC1. TPC-1 treated with the RET/PTC1 inhibitor RPI-1 displayed a cytostatic and reversible inhibition of cell proliferation and a strong activation of focal adhesion kinase (FAK). As dasatinib inhibition of Src results in reduction of FAK activation, we evaluated the effects of TPC-1 treatment with dasatinib in combination with RPI-1.

Results

Dasatinib (100 nM) strongly reduced TPC-1 proliferation and induced marked changes in TPC-1 morphology. Cells appeared smaller and more contracted, with decreased cell spreading, due to the inhibition of phosphorylation of important cytoskeletal proteins (p130^CAS, Crk, and paxillin) by dasatinib. The combination of RPI-1 with dasatinib demonstrated enhanced effects on cell proliferation (more than 80% reduction) and on the phosphotyrosine protein profile. In particular, RPI-1 reduced the phosphorylation of RET, MET, DCDB2, CTND1, and PLCγ, while dasatinib acted on the phosphorylation of EGFR, EPHA2, and DOK1. Moreover, dasatinib completely abrogated the phosphorylation of FAK at all tyrosine sites (Y576, Y577, Y861, Y925) with the exception of the autoactivation site (Y397). Notably, the pharmacological treatments induced an overexpression of integrin β1 (ITB1) that was correlated with a mild enhancement in phosphorylation of ERK1/2 and STAT3, known for their roles in prevention of apoptosis and in increase of proliferation and survival. A reduction in Akt, p38 and JNK1/2 activation was observed.

Conclusions

All data demonstrate that the combination of the two drugs effectively reduced cell proliferation (by more than 80%), significantly decreased Tyr phosphorylation of almost all phosphorylable proteins, and altered the morphology of the cells, supporting high cytostatic effects. Following the combined treatment, cell survival pathways appeared to be mediated by STAT3 and ERK activities resulting from integrin clustering and FAK autophosphorylation. EphA2 may also contribute, at least in part, to integrin and FAK activation. In conclusion, these data implicate ITB1 and EphA2 as promising therapeutic targets in PTC.

The small molecule curcumin analog FLLL32 induces apoptosis in melanoma cells via STAT3 inhibition and retains the cellular response to cytokines with anti-tumor activity

Background

We characterized the biologic effects of a novel small molecule STAT3 pathway inhibitor that is derived from the natural product curcumin. We hypothesized this lead compound would specifically inhibit the STAT3 signaling pathway to induce apoptosis in melanoma cells.

Results

FLLL32 specifically reduced STAT3 phosphorylation at Tyr705 (pSTAT3) and induced apoptosis at micromolar amounts in human melanoma cell lines and primary melanoma cultures as determined by annexin V/propidium iodide staining and immunoblot analysis. FLLL32 treatment reduced expression of STAT3-target genes, induced caspase-dependent apoptosis, and reduced mitochondrial membrane potential. FLLL32 displayed specificity for STAT3 over other homologous STAT proteins. In contrast to other STAT3 pathway inhibitors (WP1066, JSI-124, Stattic), FLLL32 did not abrogate IFN-γ-induced pSTAT1 or downstream STAT1-mediated gene expression as determined by Real Time PCR. In addition, FLLL32 did not adversely affect the function or viability of immune cells from normal donors. In peripheral blood mononuclear cells (PBMCs), FLLL32 inhibited IL-6-induced pSTAT3 but did not reduce signaling in response to immunostimulatory cytokines (IFN-γ, IL 2). Treatment of PBMCs or natural killer (NK) cells with FLLL32 also did not decrease viability or granzyme b and IFN-γ production when cultured with K562 targets as compared to vehicle (DMSO).

Conclusions

These data suggest that FLLL32 represents a lead compound that could serve as a platform for further optimization to develop improved STAT3 specific inhibitors for melanoma therapy.