Tumor cell-expressed lipolysis-stimulated lipoprotein receptor negatively regulates T-cell function.

Lipolysis-stimulated lipoprotein receptor (LSR) is known as a lipoprotein receptor. LSR is expressed in various solid tumors, including epithelial ovarian, gastric, and colon cancers. High LSR expression is significantly associated with poor prognosis, but its role in cancer has not been fully elucidated. LSR belongs to the Ig protein superfamily, which is conserved in B7 family. Here, we assessed LSR as a novel immune checkpoint molecule. We developed a novel anti-LSR antibody (#27-6 mF-18) that defects antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity activity. The #27-6 mF-18 cross-reacts with both human and mouse LSR. We found that LSR was expressed on 4T1 murine breast cancer cell line. The #27-6 mF-18 exhibited antitumor effects against the 4T1 syngeneic tumor model, a poor immunogenic model refractory to treatment with anti-PD-1 or anti-CTLA-4 antibodies. Compared with control antibody-treated mice, mice treated with #27-6 mF-18 showed significantly increased numbers of CD8+ T cells and a ratio of activated CD8+ T cells infiltrated in the tumor tissue. This antitumor effect was abrogated by CD8+ T-cell depletion through anti-CD8 antibody treatment, indicating that LSR negatively regulates tumor immunity by repressing CD8+ T cells. These findings show that LSR negatively regulates T-cell immune activity. LSR targeting could provide immune checkpoint inhibitors for cancer immunotherapy.

Gene therapy with SOCS1 induces potent preclinical antitumor activities in oral squamous cell carcinoma.

BACKGROUND: Constitutive activation of STAT3 promotes oncogenesis and growth of oral squamous cell carcinoma (OSCC). We investigated the mechanism of action of suppressor of cytokine signaling 1 (SOCS1), an endogenous inhibitor of JAK, as gene therapy for OSCC. METHODS: Antitumor effect of SOCS1 was compared to JAK inhibitor I by cell proliferation assay, cell cycle analysis, and apoptosis analysis in vitro. In addition, antitumor effect was evaluated using xenograft mouse models in vivo. RESULTS: JAK inhibitor I inhibited the proliferation of KOSC2 cl3-43 or T3M-1 clone2 OSCC cell lines in vitro. While JAK inhibitor I arrested both cell lines at the G2/M phase, induction of apoptosis was observed in T3M-1 clone2 cells, but not KOSC2-cl3-43 cells. An adenoviral vector expressing SOCS1 (AdSOCS1) significantly decreased the proliferation of both OSCC cell lines and induced G2/M phase cell cycle arrest and apoptosis, suggesting that induction of apoptosis of KOSC2 cl3-43 cells by AdSOCS1 is regulated by the JAK/STAT independent pathway. Overexpression of SOCS1 inhibited activation of the JAK/STAT and p44/42 MAPK pathways, while JAK inhibitor I inhibited activation of the JAK/STAT pathway only. Consistently, expression of Mcl-1 was decreased by overexpression of SOCS1, but not JAK inhibitor I. Additionally, KOSC2 cl3-43 or T3M-1 clone2 OSCC cells were subcutaneously implanted in the flanks of two xenograft mouse models. As compared to a control adenovirus vector (AdLacZ), intratumor injection of AdSOCS1 significantly decreased the tumor volume and induced apoptosis in vivo. CONCLUSION: SOCS1 gene therapy may be a beneficial approach for the treatment of OSCC.

LSR promotes epithelial ovarian cancer cell survival under energy stress through the LKB1-AMPK pathway.

Lipolysis-stimulated lipoprotein receptor (LSR), also known as a component of tricellular tight junctions, is highly expressing in epithelial ovarian cancer (EOC). However, the biological role of LSR in EOC cells remains unclear. In this study, we evaluated liver kinase B1 (LKB1) mediated AMP-activated protein kinase (AMPK) activity and investigated the effect of LSR on EOC cell survival under energy stress. LSR increased the levels of phospho-AMPKα at Thr172 and phospho-acetyl-CoA carboxylase (ACC) at Ser79 via LKB1-AMPK pathway in glucose deprivation in vitro. The increase of P-AMPKα (Thr172) and P-ACC (Ser79) was also detected in tumor microenvironment in vivo. Meanwhile, LSR promoted LKB1 localization at the cell membrane of EOC cells. By cell survival analysis, LSR attenuated glucose deprivation-induced cell death in EOC cells in vitro. Our results suggest that LSR promotes EOC cell survival and tumor growth through the LKB1-AMPK pathway.

Anti-glypican-1 antibody-drug conjugate is a potential therapy against pancreatic cancer.

BACKGROUND: Pancreatic cancer (PDAC) is the most lethal malignancy. New treatment options for it are urgently required. The aim was to develop an antibody-drug conjugate (ADC) targeting glypican-1 (GPC-1) as a new therapy for PDAC. METHODS: We evaluated GPC-1 expression in resected PDAC specimens and PDAC cell lines. We then measured the antitumour effect of anti-GPC-1 monoclonal antibody conjugated with the cytotoxic agent monomethyl auristatin F (MMAF) in vitro and in vivo. RESULTS: GPC-1 was overexpressed in most primary PDAC cells and tissues. The PDAC cell lines BxPC-3 and T3M-4 strongly expressed GPC-1 relative to SUIT-2 cells. Compared with control ADC, GPC-1-ADC showed a potent antitumour effect against BxPC-3 and T3M-4, but little activity against SUIT-2 cells. In the xenograft and patient-derived tumour models, GPC-1-ADC significantly and potently inhibited tumour growth in a dose-dependent manner. GPC-1-ADC-mediated G2/M-phase cell cycle arrest was detected in the tumour tissues of GPC-1-ADC-treated mice relative to those of control-ADC-treated mice. CONCLUSIONS: GPC-1-ADC showed significant tumour growth inhibition against GPC-1-positive pancreatic cell lines and patient-derived, GPC-1-positive pancreatic cancer tissues. Our preclinical data demonstrated that targeting GPC-1 with ADC is a promising therapy for patients with GPC-1-positive pancreatic cancer.

TAS-116 inhibits oncogenic KIT signalling on the Golgi in both imatinib-naïve and imatinib-resistant gastrointestinal stromal tumours.

BACKGROUND: Despite the effectiveness of imatinib mesylate (IM), most gastrointestinal stromal tumours (GISTs) develop IM resistance, mainly due to the additional kinase-domain mutations accompanied by concomitant reactivation of KIT tyrosine kinase. Heat-shock protein 90 (HSP90) is one of the chaperone molecules required for appropriate folding of proteins such as KIT. METHODS: We used a novel HSP90 inhibitor, TAS-116, which showed specific binding to HSP90α/ß with low toxicity in animal models. The efficacy and mechanism of TAS-116 against IM-resistant GIST were evaluated by using IM-naïve and IM-resistant GIST cell lines. We also evaluated the effects of TAS-116 on the other HSP90 client protein, EGFR, by using lung cell lines. RESULTS: TAS-116 inhibited growth and induced apoptosis in both IM-naïve and IM-resistant GIST cell lines with KIT activation. We found KIT was activated mainly in intracellular compartments, such as trans-Golgi cisternae, and TAS-116 reduced autophosphorylated KIT in the Golgi apparatus. In IM-resistant GISTs in xenograft mouse models, TAS-116 caused tumour growth inhibition. We found that TAS-116 decreased phosphorylated EGFR levels and inhibited the growth of EGFR-mutated lung cancer cell lines. CONCLUSION: TAS-116 may be a novel promising drug to overcome tyrosine kinase inhibitor-resistance in both GIST and EGFR-mutated lung cancer.

Anti-glypican-1 antibody-drug conjugate exhibits potent preclinical antitumor activity against glypican-1 positive uterine cervical cancer.

Glypican-1 (GPC1) is highly expressed in solid tumors, especially squamous cell carcinomas (SCCs), and is thought to be associated with disease progression. We explored the use of a GPC1-targeted antibody-drug conjugate (ADC) as a novel treatment for uterine cervical cancer. On immunohistochemical staining, high expression levels of GPC1 were detected in about 50% of uterine cervical cancer tissues and also in a tumor that had relapsed after chemoradiotherapy. Novel anti-GPC1 monoclonal antibodies were developed, and clone 01a033 was selected as the best antibody for targeted delivery of the cytotoxic agent monomethyl auristatin F (MMAF) into GPC1-positive cells. The anti-GPC1 antibody was conjugated with MMAF. On flow cytometry, HeLa and ME180 cervical cancer cells highly expressed GPC1, however, RMG-I ovarian clear cell cancer cell line showed weak expression. The GPC1-ADC was rapidly internalized into GPC1-expressing cells in vitro and was potently cytotoxic to cancer cells highly expressing GPC1. There were no inhibitory effects on cancer cells with low expression of GPC1. In a murine xenograft model, GPC1-ADC also had significant and potent tumor growth inhibition. GPC1-ADC-mediated G2/M phase cell cycle arrest was detected, indicating that the dominant antitumor effect in vivo was MMAF-mediated. The toxicity of GPC-ADC was tolerable within the therapeutic dose range in mice. Our data showed that GPC1-ADC has potential as a promising therapy for uterine cervical cancer.

Leucine rich α-2 glycoprotein is a potential urinary biomarker for renal tubular injury.

Recent evidence suggests that renal tubular injury plays a key role in deterioration of renal function in both chronic kidney disease (CKD) and acute kidney injury (AKI). Since commonly used biochemical indicators such as GFR, serum creatinine, blood urea nitrogen and creatinine clearance are inappropriate for detecting alteration in renal tubules, biomarkers reflecting renal tubular injury have been extensively explored. Our research group identified leucine rich α-2 glycoprotein (LRG) as a novel serum biomarker for various inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. In inflammatory diseases, LRG expression is up-regulated at the site of inflammation, in accordance with the induction of LRG in many cell types by various inflammatory cytokines. Recently, urinary LRG was reported as a possible biomarker for several renal diseases, but the mechanism of LRG excretion in urine is still unclear. In this study, by analyzing a mouse albumin (ALB) overload model that is commonly used to study proteinuria-induced renal tubular injury, we provided evidence that urinary LRG is produced in renal tubular epithelial cells by interleukin-1ß (IL-1ß) that is released during proteinuria-induced renal damage. In this model, urinary LRG became detectable after ALB overload. In kidney, mRNA expression of LRG together with that of NACHT LRR and PYD domains-containing protein 3 (NLRP3) and IL-1ß was significantly up-regulated in ALB-overloaded mice, compared to PBS-treated mice. By pathological analysis of kidney, LRG was detected in the injured proximal tubules, distal tubules and collecting ducts in ALB-overloaded mice. Accordingly, in vitro stimulation of mouse renal cortical tubular epithelial cells with excessive ALB led to LRG mRNA up-regulation and its protein secretion, which was effectively blocked by IL-1 receptor antagonist. These results suggest that urinary LRG could be applied to a biomarker detecting renal tubular injury in various renal diseases.

SOCS1 gene therapy has antitumor effects in imatinib-resistant gastrointestinal stromal tumor cells through FAK/PI3 K signaling.

BACKGROUND: Most of the gastrointestinal stromal tumors (GIST) have mutations in the KIT gene, encoding a receptor tyrosine kinase. Imatinib, a receptor tyrosine kinase inhibitor, is the first-line therapy for unresectable and metastatic GISTs. Despite the revolutionary effects of imatinib, some patients are primarily resistant to imatinib and many become resistant because of acquisition of secondary mutations in KIT. This study investigated the antitumor effects of SOCS1 gene therapy, which targets several signaling pathways. METHODS: We used GIST-T1 (imatinib-sensitive) and GIST-R8 (imatinib-resistant) cells. We infected both cell lines with an adenovirus expressing SOCS1 (AdSOCS1) and examined antitumor effect and mechanisms of its agent. RESULTS: The latter harboured with secondary KIT mutation and had imatinib resistance > 1000-fold higher than the former cells. We demonstrated that AdSOCS1 significantly decreased the proliferation and induced apoptosis in both cell lines. Moreover, SOCS1 overexpression inhibited the phosphorylation of signal transducer and activator of transcription 3 (STAT3), AKT, and focal adhesion kinase (FAK) in both of them. Inhibition of JAK signaling did not affect the proliferation enough. However, inhibition of the FAK signaling with an FAK inhibitor or RNA interference significantly showed inhibitory effect on cell growth and suppressed the phosphorylation of AKT, indicating a cross-talk between the AKT and FAK pathways in both the imatinib-sensitive and imatinib-resistant GIST cells. CONCLUSIONS: Our results indicate that the activation of FAK signaling is critical for proliferation of both imatinib-sensitive and -resistant GIST cells and the interference with FAK/AKT pathway might be beneficial for therapeutic target.

Suppressor of cytokine signaling-1 gene therapy induces potent antitumor effect in patient-derived esophageal squamous cell carcinoma xenograft mice.

Chronic inflammation is involved in cancer growth in esophageal squamous cell carcinoma (ESCC), which is a highly refractory cancer with poor prognosis. This study investigated the antitumor effect and mechanisms of SOCS1 gene therapy for ESCC. Patients with ESCC showed epigenetics silencing of SOCS1 gene by methylation in the CpG islands. We infected 10 ESCC cells with an adenovirus-expressing SOCS1 (AdSOCS1) to examine the antitumor effect and mechanism of SOCS1 overexpression. SOCS1 overexpression markedly decreased the proliferation of all ESCC cell lines and induced apoptosis. Also, SOCS1 inhibited the proliferation of ESCC cells via multiple signaling pathways including Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and focal adhesion kinase (FAK)/p44/42 mitogen-activated protein kinase (p44/42 MAPK). Additionally, we established two xenograft mouse models in which TE14 ESCC cells or ESCC patient-derived tissues (PDX) were subcutaneously implanted. Mice were intra-tumorally injected with AdSOCS1 or control adenovirus vector (AdLacZ). In mice, tumor volumes and tumor weights were significantly lower in mice treated with AdSOCS1 than that with AdLacZ as similar mechanism to the in vitro findings. The Ki-67 index of tumors treated with AdSOCS1 was significantly lower than that with AdLacZ, and SOCS1 gene therapy induced apoptosis. These findings demonstrated that overexpression of SOCS1 has a potent antitumor effect against ESCC both in vitro and in vivo including PDX mice. SOCS1 gene therapy may be a promising approach for the treatment of ESCC.

Overexpression of glypican-1 implicates poor prognosis and their chemoresistance in oesophageal squamous cell carcinoma.

BACKGROUND: Despite the recent improvements in multimodal therapies for oesophageal squamous cell carcinoma (ESCC), the prognosis remains poor. The identification of suitable biomarkers for predicting the prognosis and chemo-sensitivity is required to develop targeted treatments and improve treatment results. METHODS: Proteins highly expressed in ESCC cell lines compared with normal oesophageal cell lines were screened by isobaric tag for relative and absolute quantitation (iTRAQ). We identified glypican-1 (GPC1) as a novel molecule. The clinicopathological characteristics of GPC1 were evaluated by immunohistochemistry using ESCC specimens, and clinical parameters were assessed. The correlation between GPC1 expression levels and chemo-sensitivity were analysed in vitro. RESULTS: In the immunohistochemical assessment of 175 ESCC patients, 98.8% expressed GPC1. These patients demonstrated significantly poorer prognosis compared with patients with low-GPC1 expression by survival assay (P<0.001). Higher chemoresistance was observed in the GPC1 high-expression group. GPC1 expression levels positively correlated with chemo-sensitivity against cis-Diammineplatinum (II) dichloride (CDDP), and are potentially associated with anti-apoptotic function based on alterations in the MAPK downstream signalling pathway and Bcl-2 family member proteins. CONCLUSIONS: GPC1 is an independent prognostic factor in ESCC and is a critical molecule for altering the threshold of chemoresistance to CDDP.

Salt-inducible kinase 3 deficiency exacerbates lipopolysaccharide-induced endotoxin shock accompanied by increased levels of pro-inflammatory molecules in mice.

Macrophages play important roles in the innate immune system during infection and systemic inflammation. When bacterial lipopolysaccharide (LPS) binds to Toll-like receptor 4 on macrophages, several signalling cascades co-operatively up-regulate gene expression of inflammatory molecules. The present study aimed to examine whether salt-inducible kinase [SIK, a member of the AMP-activated protein kinase (AMPK) family] could contribute to the regulation of immune signal not only in cultured macrophages, but also in vivo. LPS up-regulated SIK3 expression in murine RAW264.7 macrophages and exogenously over-expressed SIK3 negatively regulated the expression of inflammatory molecules [interleukin-6 (IL-6), nitric oxide (NO) and IL-12p40] in RAW264.7 macrophages. Conversely, these inflammatory molecule levels were up-regulated in SIK3-deficient thioglycollate-elicited peritoneal macrophages (TEPM), despite no impairment of the classical signalling cascades. Forced expression of SIK3 in SIK3-deficient TEPM suppressed the levels of the above-mentioned inflammatory molecules. LPS injection (10 mg/kg) led to the death of all SIK3-knockout (KO) mice within 48 hr after treatment, whereas only one mouse died in the SIK1-KO (n = 8), SIK2-KO (n = 9) and wild-type (n = 8 or 9) groups. In addition, SIK3-KO bone marrow transplantation increased LPS sensitivity of the recipient wild-type mice, which was accompanied by an increased level of circulating IL-6. These results suggest that SIK3 is a unique negative regulator that suppresses inflammatory molecule gene expression in LPS-stimulated macrophages.

Suppressor of cytokine signalling-1 induces significant preclinical antitumor effect in malignant melanoma cells.

Malignant melanoma is the most aggressive form of skin cancer, responsible for the majority of skin cancer-related deaths. Metastatic melanoma is resistant to surgery, radiation or chemotherapy, and an effective therapy has not yet been established. Our study investigated the therapeutic potential of the suppressor of cytokine signalling-1 (SOCS-1), an endogenous inhibitor of the intracellular cytokine signalling pathway, for treating melanoma. Adenovirus vectors encoding the SOCS-1 gene were used to overexpress SOCS-1 in three melanoma cell lines (G361, SK-MEL5 and SK-MEL28). In G361 and SK-MEL5, overexpression of SOCS-1 significantly reduced cell proliferation and induced apoptosis in vitro and in vivo. Furthermore, we indicated that the antiproliferative effect of SOCS-1 correlated not only with decreased levels of the activation of signal transducer and activator of transcription (STAT)3 but also with increased levels of p53 expression and phosphorylation. These findings indicate the potential for clinical use of SOCS-1 for melanoma treatment.

The influence of excessive IL-6 production in vivo on the development and function of Foxp3+ regulatory T cells.

IL-6 is a proinflammatory cytokine and its overproduction is implicated in a variety of inflammatory disorders. Recent in vitro analyses suggest that IL-6 is a key cytokine that determines the balance between Foxp3(+) regulatory T cells (Tregs) and Th17 cells. However, it remains unclear whether excessive IL-6 production in vivo alters the development and function of Foxp3(+) Tregs. In this study, we analyzed IL-6 transgenic (Tg) mice in which serum IL-6 levels are constitutively elevated. Interestingly, in IL-6 Tg mice, whereas peripheral lymphoid organs were enlarged, and T cells exhibited activated phenotype, Tregs were not reduced but rather increased compared with wild-type mice. In addition, Tregs from Tg mice normally suppressed proliferation of naive T cells in vitro. Furthermore, Tregs cotransferred with naive CD4 T cells into SCID-IL-6 Tg mice inhibited colitis as successfully as those transferred into control SCID mice. These results indicate that overproduction of IL-6 does not inhibit development or function of Foxp3(+) Tregs in vivo. However, when naive CD4 T cells alone were transferred, Foxp3(+) Tregs retrieved from SCID-IL-6 Tg mice were reduced compared with SCID mice. Moreover, the Helios(-) subpopulation of Foxp3(+) Tregs, recently defined as extrathymic Tregs, was significantly reduced in IL-6 Tg mice compared with wild-type mice. Collectively, these results suggest that IL-6 overproduced in vivo inhibits inducible Treg generation from naive T cells, but does not affect the development and function of natural Tregs.

Lipolysis-stimulated lipoprotein receptor-targeted antibody-drug conjugate demonstrates potent antitumor activity against epithelial ovarian cancer.

BACKGROUND: Epithelial ovarian cancer (EOC) is a lethal malignant tumor, for which new treatment options are urgently required. Lipolysis-stimulated lipoprotein receptor (LSR) is widely expressed in EOC, and it is associated with poor prognosis. In this study, we developed an antibody-drug conjugate (ADC) targeting LSR as a new therapeutic approach to EOC. METHODS: We, herein, developed novel anti-LSR monoclonal antibodies (mAbs) and an LSR-ADC by conjugating monomethyl auristatin E as a payload. We subsequently evaluated the in vitro and in vivo (on xenograft models) antitumor effect of the LSR-ADC. RESULTS: An overexpression of LSR was observed not only in the primary EOC tumor but also in its lymph node and omental metastases. The EOC cell lines NOVC7-C and OVCAR3 strongly expressed LSR (as compared to ES2 cells). Both the anti-LSR mAb and the LSR-ADC were able to specifically bind to LSR-positive cells and were rapidly internalized and trafficked to the lysosomes. The LSR-ADC demonstrated a potent antitumor effect against NOVC-7C and OVCAR3, but little activity against ES2 cells. In vitro, the LSR-ADC exhibited a potent antitumor effect against NOVC-7C and OVCAR3. Moreover, in the OVCAR3 xenograft models as well as in the patient-derived xenograft models of LSR-positive EOC, the LSR-ADC significantly inhibited tumor growth. The LSR-ADC also suppressed the omental/bowel metastases in OVCAR3-Luc xenografts and improved the median survival. CONCLUSION: The developed LSR-ADC demonstrated a significant antitumor activity against LSR-positive EOC cell lines and tumors. Our preclinical data support the use of the LSR-ADC as a novel therapy for patients with LSR-positive ovarian cancer.

Nano-particulate Toll-like Receptor 9 Agonist Potentiates the Antitumor Activity of Anti-Glypican-1 Antibody.

BACKGROUND/AIM: Monoclonal antibodies (mAbs) that target tumor antigens have recently been developed. Their antitumor activity is mainly achieved through antibody-dependent cellular cytotoxicity (ADCC) via effector cells such as tumor-infiltrated macrophages and natural killer (NK) cells. CpG oligodeoxynucleotides (ODNs) have potent antitumor activity and are considered to increase the tumor infiltration of macrophages and NK cells; however, a completely solubilized novel CpG-schizophyllan (SPG) complex, K3-SPG, displays more potent antitumor activity. We recently reported the significant antitumor activity of anti-glypican-1 (GPC1) mAb against GPC1-positive esophageal squamous cell carcinoma (ESCC) via ADCC. The aim of this study was to evaluate the potential synergistic antitumor activity of anti-GPC1 mAb and K3-SPG and elucidate the underlying mechanisms using a xenograft model of GPC1-positive human ESCC cells. MATERIALS AND METHODS: The established human esophageal cancer cell line TE14 was subcutaneously injected into SCID mice. Xenograft mice were treated with anti-GPC1 mAb, K3-SPG, or their combination. Antitumor activity was evaluated by measuring the tumor volume. For FACS analysis, agents were administrated, and tumors were resected 1 day after the final treatment. RESULTS: Anti-GPC1 mAb or K3-SPG monotherapy showed dose-dependent antitumor activity, and combination therapy with anti-GPC1 mAb and K3-SPG showed antitumor activity (p=0.0859). Flow cytometry revealed significantly increased numbers of macrophages (p=0.0133) and of the ratio of activated NK cells/total NK cells (p=0.0058) following K3-SPG or combination therapy. CONCLUSION: Combination therapy with K3-SPG and anti-GPC1 mAb or another antitumor mAb may represent a new cancer treatment option acting via ADCC.

SOCS1 Gene Therapy for Head and Neck Cancers: An Experimental Study.

BACKGROUND/AIM: Head and neck squamous cell carcinoma (HNSCC) is a fatal and debilitating disease, which is characterized by steady, poor survival rates despite advances in treatment. Suppressor of cytokine signaling (SOCS) 1 is up-regulated following cytokine-induced Janus kinase - signal transducer and activator of transcription (JAK-STAT) pathway activation, and inhibitors of cytokine signaling play roles in regulating cell growth and differentiation. We investigated the therapeutic potential of SOCS1 for HNSCC. MATERIALS AND METHODS: We used cell lines of oropharyngeal and tongue cancers (Detroit-562 and SCC-9, respectively) and a recombinant adenovirus vector expressing SOCS1 (AdSOCS1). RESULTS: AdSOCS1-induced SOCS1 overexpression significantly decreased cell proliferation through G2M phase cell cycle arrest and apoptosis. AdSOCS1 inhibited cell growth more strongly in SCC-9 cells than in Detroit-562 cells. JAK inhibitor I induced cell cycle arrest at the G0/G1 and GfM phases in Detroit-562 and SCC-9 cells, respectively. AdSOCS1 also decreased the activity of phosph-STAT3 (pSTAT3) and phosphop44/42 mitogen-activated protein kinase (p-p44/42 MAPK), as well as the expression of the anti-apoptotic protein B-cell lymphoma-extra large (Bcl-xL). JAK inhibitor I decreased the expression of pSTAT3, but not p-p44/42 or Bcl-xL. The MAPK/extracellular signal-regulated kinase (MEK) inhibitor, U0126, decreased the expression of Bcl-xL in SCC-9 cells, but not in Detroit-562 cells. AdSOCS1 treatment inhibited tumor growth in mouse xenograft models. CONCLUSION: Overexpression of SOCS1 has a potent antitumor effect on HNSCC, suggesting the potential for clinical use. The varying effectiveness among cancer cells by over expression of SOCS1 may contribute to efficacy of SOCS 1 gene therapy for clinical use.

Green tea polyphenol epigallocatechin gallate inhibits cell signaling by inducing SOCS1 gene expression.

Therapeutic effects of green tea involve an inhibitory function of its constituent polyphenol epigallocatechin gallate (EGCG) on cell signaling. The specificity and mechanism(s) by which EGCG inhibits cell signaling have remained unclear. Here, we demonstrate that green tea and EGCG induce suppressor of cytokine signaling 1 (SOCS1) gene expression, a negative regulator of specific cell signaling pathways. In mouse immune cells, EGCG induces SOCS1 expression via an oxidative (superoxide) pathway and activation of the signal transducer and activator of transcription 5 transcription factor. EGCG inhibited SOCS1-regulated cell signaling, but this inhibitory effect was abrogated in cells deficient in SOCS1. These findings identify a mechanism by which EGCG inhibits cell signaling with specificity, mediated by induction of the negative regulator SOCS1.

IL-6 blockade inhibits the induction of myelin antigen-specific Th17 cells and Th1 cells in experimental autoimmune encephalomyelitis.

The development of Th17 cells is a key event in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a murine model of human multiple sclerosis (MS). Previous studies have demonstrated that an IL-6-dependent pathway is involved in the differentiation of Th17 cells from naïve CD4-positive T cells in vitro. However, the role of IL-6 in vivo in the development of Th17 cells in EAE has remained unclear. In the present study, we found that IL-6 blockade by treatment with an anti-IL-6 receptor monoclonal antibody (anti-IL-6R mAb) inhibited the development of EAE and inhibited the induction of myelin oligodendrocyte glycoprotein (MOG) peptide-specific CD4-positive, CD8-positive, and Th17 T cells, in inguinal lymph nodes. Thus, the protective effect of IL-6 blockade in EAE is likely to be mediated via the inhibition of the development of MOG-peptide-specific Th17 cells and Th1 cells, which in turn leads to reduced infiltration of T cells into the CNS. These findings indicate that anti-IL-6R mAb treatment might represent a novel therapy for human MS.

Correction: Lipolysis-stimulated lipoprotein receptor overexpression is a novel predictor of poor clinical prognosis and a potential therapeutic target in gastric cancer.

[This corrects the article DOI: 10.18632/oncotarget.25952.].