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The IL6-GP130-STAT3 signaling pathway facilitates lung cancer progression and resistance to tyrosine kinase inhibitors. Although glycosylation alters the stability of GP130 receptor, its effect on the ligand IL6 remains unclear. In this study, we found that N-glycosylated IL6 primarily triggers JAK-STAT3 signaling and prolongs STAT3 phosphorylation, whereas N-glycosylation-defective IL6 (DeNG-IL6) induces shortened STAT3 activation and changes the downstream signaling preference for the SRC-YAP-SOX2 axis. This signaling shift promoted epithelial plasticity in vitro and metastasis in vivo, which were suppressed by specific inhibitors and shRNAs targeting SRC, YAP, and SOX2. EGFR TKI-resistant lung cancer cells secrete high levels of DeNG-IL6 via reduced N-glycosyltransferase gene expression and showed SRC-YAP activation. DeNG-IL6 contributes to drug resistance, as confirmed by in silico analysis of cellular and clinical transcriptomes, and signal expression in patient specimens. In summary, cell behaviors can be altered by modifying the N-glycosylation of IL6, and the glycosylation status of circulating IL6 might be a promising biomarker for monitoring the dynamics of lung cancer evolution. Citation Format: Chun Hua Hung, Shang-Yin Wu Wu, Hsuan-Heng Yeh Yeh, Chien-Chung Lin, Wu-Chou Su. N-glycosylation-defective IL6 activates the SRC-YAP-SOX2 signaling to potentiate metastasis and TKI resistance in NSCLC. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3888.

Growing evidence suggests that Stat3 contributes to chemoresistance. However, the impact of chemotherapy on Stat3 activity is unclear. We found that paclitaxel activated Stat3 in the human lung cancer cell lines PC14PE6AS2 (AS2) and H157, whereas it reduced Stat3 activation in A549 and H460 cells. Pretreatment of AS2 and H157 cells with rotenone, an inhibitor of mitochondrially produced reactive oxygen species (ROS), or carbonyl cyanide p-(trifluoromethoxy)-phenylhydrazone (FCCP), a mitochondrial uncoupler, suppressed the paclitaxel-induced activation of Stat3. Uncoupling protein 2 (UCP-2), located in the inner membrane of the mitochondria, can reduce ROS production in conditions of oxidative stress. UCP-2 protein expression in the four cancer cell lines was higher than that in normal lung epithelial cells (NL-20), but its expression was lower in AS2 and H157 cells relative to A549 and H460 cells. Silencing high UCP-2 expression with small interfering RNA (siRNA) in A549 and H460 cells restored paclitaxel-induced Stat3 activation. In addition, paclitaxel-induced Stat3 activation led to the upregulation of survivin and Mcl-1, which in turn facilitated cell survival. Moreover, the CL1-5 subline had lower UCP-2 expression relative to the parental CL1-0 cells. Treatment with paclitaxel activated Stat3 in CL1-5 but not in CL1-0 cells, whereas in CL1-5 cells, the overexpression of UCP-2 with complementary DNA (cDNA) blocked Stat3 activation. In lung cancer patients, low UCP-2 expression in cancer cells was a predictor of a poor response to chemotherapy. Therefore, UCP-2 modulates the ROS/Stat3 signaling pathway and response to chemotherapy treatment in lung cancer cells. Targeting UCP-2, ROS and Stat3 pathways may improve anticancer therapies.

Estrogens contribute to the pathogenesis of female lung cancer and function mainly through estrogen receptor-β (ERβ). However, the way in which ERβ expression is regulated in lung cancer cells remains to be explored. We have found that signal transducer and activator of transcription 3 (Stat3) activation up-regulates ERβ expression in PC14PE6/AS2 lung cancer cells in a preliminary Affymetrix oligonucleotide array study, and we sought to confirm the findings. In this study, we show that IL-6 induced ERβ mRNA and protein expression in lung cancer cells. The induction of ERβ in response to IL-6 was abolished by Janus kinase 2 inhibitor-AG490, dominant-negative mutant of Stat3, and Stat3-targeting short interfering RNA. The luciferase reporter assay and chromatin immunoprecipitation assay confirmed that IL-6-activated Stat3 binds to the ERβ promoter. Besides the Janus kinase 2/Stat3 pathway, the MEK/Erk pathway contributes to ERβ up-regulation induced by IL-6; however, the phosphoinositide 3'-kinase/Akt pathway does not. We also found that epidermal growth factor (EGF) stimulation or L858R mutation in EGF receptor (EGFR) induced Stat3 activation as well as ERβ expression in lung cancer cells. Inhibiting Stat3 activity by pharmacological or genetic approaches reduced EGF- and L858R mutant EGFR-induced ERβ expression, indicating that Stat3 activation is required for EGFR signaling-mediated ERβ up-regulation. Silencing ERβ decreased cell proliferation in lung cancer cells that overexpress L858R mutant EGFR. In conclusion, we have identified that Stat3 activation is essential for ERβ induction by IL-6, EGF, and the presence of EGFR mutation. The findings shed light on new therapeutic targets for female lung cancer, especially for those with EGFR mutations.

Gene amplification or HER-2/neu protein overexpression signals a poor outcome for bladder cancer patients. We investigated the anti-proliferative effect of IFN-gamma in HER-2/neu-transfected human bladder cancer cells (TCC-N5 and TCC-N10). The cells continued growing after IFN-gamma stimulation but did not activate the Janus kinase (Jak)/Stat pathway. We found Jak/Stat protein phosphatase in TCC-N5 and TCC-N10 cells with upregulated Src homology 2-containing protein tyrosine phosphatase-2 (SHP-2). After the cells had been treated with AG825, a HER-2/neu-specific inhibitor, SHP-2 expression declined, and Jak2/Stat1 reactivated. Similar results were reported in a mouse bladder cancer cell line, MBT2, with constitutive HER-2/neu overexpression. Further, AG825 pretreatment restored the anti-proliferation activity of IFN-gamma in TCC-N5 and TCC-N10 cells. Therefore, the suppression of IFN-gamma signaling in HER-2/neu-overexpressing bladder cancer cells might be due to SHP-2 upregulation. The regulation of SHP-2 by HER-2/neu provides a new target for blocking the HER-2/neu oncogenic pathway.

Targeted cancer therapies can effectively promote tumor regression in clinical responses. Eventually, most tumors develop resistance to these drugs. Stat3 activation has been suggested as one of the mechanisms that cause acquired resistance to EGFR-tyrosin kinase inhibitor (TKI) in non-small cell lung cancer (NSCLC). However, the underlying molecular mechanisms are not well studied. In this study, we found that treatment of gefitinib (EGFR-TKI) in NSCLC cell lines harboring EGFR-TKI sensitive mutation induced feedback activation of Stat3 in a time- and dose-dependent manner. High levels of IL-6 were detected in the conditioned medium of gefitinib-treated cells by cytokine array and were confirmed by ELISA. We demonstrated that IL-6 treatment could induce Stat3 activation and conditioned medium treatment-induced Stat3 activation was suppressed by IL-6 neutralizing antibody. We also demonstrated that gefitinib treatment-induced IL-6 secretion could be inhibited by knockdown of Stat3 expression. Moreover, pharmacological inhibition and genetic inhibition of Stat3 activation increased cell cytotoxicity of gefitinib in both PC9 and HCC827 cells that harboring EGFR-TKI sensitive mutation. Our data suggested that gefitinib treatment could induce activation of IL-6/Stat3 signaling loop and modulate cell cytotoxicity of gefitinib. Microarray and Ingenuity Pathway Analysis (IPA) analysis revealed prostaglandin I2 synthase (PTGIS) as a downstream target gene of IL-6/Stat3 signaling and PTGIS was up-regulated by gefitinib treatment. The induction of PTGIS by gefitinib via Stat3 feedback activation was confirmed in vitro genetically and pharmacologically. Moreover, we showed that cotreatment with PTGIS inhibitor improves the efficacy of EGFR inhibition in PC9 and HCC827 cells. Importantly, high expression of PTGIS was found in gefitinib-resistant PC9 cells (PC9/gef) compared with gefitinib-sensitive PC9 cells. Targeting PTGIS was also effective in decreasing viability of cells with acquired resistance to gefitinib in PC9/gef cells. Taken together, our study indicated that Stat3 feedback activation-induced PTGIS expression participates in modulating gefitinib efficacy and Stat3/PTGIS inhibition could potentially overcome acquired resistance to gefitinib in NSCLC. Note: This abstract was not presented at the meeting. Citation Format: Hsuan-Heng Yeh, Shang-Yin Wu, Chun-Hua Hung, Wu-Chou Su. Stat3 feedback activation-induced PTGIS expression is associated with acquired resistance to EGFR-TKI in lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5872. doi:10.1158/1538-7445.AM2017-5872

Transformation to small-cell lung cancer (SCLC, one of aggressive neuroendocrine [NE] tumor) is reported when activating epidermal growth factor receptor (EGFR) mutant non-small-cell lung cancer acquired resistance to tyrosine kinase inhibitors (TKI, such as gefitinib). IL-6 activation confers to acquire TKI resistance and associates with p53 and RB inactivation those are SCLC hallmark changes. Whether NE transformation could phenocopy in isogenic acquired resistance cell line and the role of IL-6 in this process remain unknown. We established 827GRs (including 827GR, 827GR+ and 827GR.M6) acquired resistance to gefitinib from HCC827 cells by long term stepwise treated with gefitinib and they still had EGFR exon 19 deletion without acquired T790M. 827GR was parental resistance line with unstable gefitinib resistance in drug-free medium by passage. We maintained 827GR in medium with or without 1μM gefitinib over 6 months to generate stable clones: 827GR+ and 827GR.M6. 827GRs had SCLC hallmark changes, i.e., inactivation of p53, RB and Notch by western blot and gene set enrichment analysis. Compared to HCC827, 827GRs were more sensitive to cisplatin and etoposide but not paclitaxel. IL-6 level was positive correlated with gefitinib resistance among 827GRs by cytokine array and ELISA. Interestingly, among 827GRs, 827GR.M6 harbored low IL-6 secretion had obviously NOTCH-ASCL1-DLL3 alteration, high NE marker expression and significant inter-rater agreement with selected Byers’ SCLC gene signature than high IL-6 secretion 827GR+, suggesting IL-6 dynamics might regulate NE marker expression. IL-6 genetic manipulation in HCC827 and 827GR+ also demonstrated this phenomenon. Moreover, IL-6 dynamics correlate with NE expression also showed in patient derived lung cancer cell line in published microarray dataset (GSE64322). In conclusion, our work demonstrated activating EGFR mutant lung cancer acquired resistance to TKI with NE transformation could phenocopy in isogenic cell line model and IL-6 dynamics might regulate this process. Citation Format: Shang-Yin Wu, Hsuan-Heng Yeh, Chun-Hua Hung, Chien-Chung Lin, Wen-Pin Su, Wu-Chou Su. IL-6 dynamics regulate neuroendocrine transformation in gefitinib acquired resistance EGFR mutant lung cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4103. doi:10.1158/1538-7445.AM2017-4103

Malignant pleural effusion (MPE) is a poor prognostic sign for patients with lung cancer. Tissue factor (TF) is a coagulation factor that participates in angiogenesis and vascular permeability and is abundant in MPE. We previously demonstrated that autocrine IL-6-activated Stat3 contributes to tumor metastasis and upregulation of VEGF, resulting in the generation of MPE in lung adenocarcinoma. In this study, we found IL-6-triggered Stat3 activation also induces TF expression. By using pharmacologic inhibitors, it was shown that JAK2 kinase, but not Src kinase, contributed to autocrine IL-6-induced TF expression. Inhibition of Stat3 activation by dominant negative Stat3 (S3D) in lung adenocarcinoma suppressed TF-induced coagulation, anchorage-independent growth in vitro, and tumor growth in vivo. Consistently, knockdown of TF expression by siRNA resulted in a reduction of anchorage-independent growth of lung adenocarcinoma cells. Inhibition of TF expression also decreased the adhesion ability of cancer cells in normal lung tissues. In the nude mouse model, both lung metastasis and MPE generation were decreased when PC14PE6/AS2-siTF cells (TF expression was silenced) were intravenously injected. PC14PE6/AS2-siTF cells also produced less malignant ascites through inhibition of vascular permeability. In summary, we showed that TF expression plays a pivotal role in the pathogenesis of MPE generation via regulating of tumor metastasis and vascular permeability in lung adenocarcinoma bearing activated Stat3.

Metformin has been used as first-line treatment in patients with type 2 diabetes, and is reported to reduce cancer risk and progression by activating the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway. Cisplatin remains the main drug for treating advanced non-small-cell lung cancer. However, drug resistance often develops through several mechanisms during the treatment course, including one mechanism mediated by the activation of the IL-6/signal transducer and activator of transcription (STAT)-3 pathway, related to the generation of reactive oxygen species (ROS). This study demonstrated a correlation between STAT3 phosphorylation and cisplatin cytotoxicity, using AS2 (PC14PE6/AS2)-derived cell lines (AS2/S3C) that contained constitutively active STAT3 plasmids as a model. A STAT3 inhibitor (JSI-124) enhanced the cisplatin sensitivity in AS2 cells, whereas metformin inhibited STAT3 phosphorylation and enhanced cisplatin cytotoxicity. By contrast, another AMPK activator (5-aminoimidazole-4-carboxamide-riboside) failed to produce these effects. LKB1-AMPK silencing by small, interfering RNA or mammalian target of rapamycin (mTOR) inhibition by rapamycin or pp242 did not alter the effect of metformin on STAT3 activity suppression, suggesting that metformin can modulate the STAT3 pathway through an LKB1-AMPK-independent and probably mTOR-independent mechanism. Metformin also inhibited cisplatin-induced ROS production and autocrine IL-6 secretion in AS2 cells. Both mechanisms contributed to the ability of metformin to suppress STAT3 activation in cancer cells, which resulted in the decreased secretion of vascular endothelial growth factor by cancer cells. The growth of subcutaneous tumor xenografts was significantly delayed by a combination of cisplatin and metformin. This is the first study to demonstrate that metformin suppresses STAT3 activation via LKB1-AMPK-mTOR-independent but ROS-related and autocrine IL-6 production-related pathways. Thus, metformin helps to overcome tumor drug resistance by targeting STAT3.

Interleukin-6 (IL-6) is critical in modulating both tumor growth and anti-tumor immunity. Here, we describe the glycosylation pattern of lung cancer cell-secreted IL-6 and examine the function of the IL-6 glycoforms in polarization of tumor-associated macrophages (TAMs). IL-6 with different molecular weights were detected in various lung cancer cells. Because in NetNGlyc 1.0 Server, one possible N-glycosylation site has been predicted at N73 on IL-6, we used tunicamycin treatment and site-directed mutagenesis on N73 to demonstrate that lung cancer cell-secreted IL-6 is modified by N-glycosylation. To explore more detailed attached glycans, we measured the expression of glycosyltransferases by qPCR and found that the expression of fucosyltransferase 8 (FUT8), responsible for core fucosylation on N-glycosylated proteins, was higher in lung cancer cells than normal bronchial cells. Core fucosylation on IL-6 was reduced by silencing FUT8. We generated AS2-IL6, AS2-IL6-shFUT8, and AS2-IL6-N73Q cells for producing full-glycosylated IL-6 (G-IL6), core fucose-depleted IL-6 (DeCF-IL6), and Asn73-N-glycan-depleted IL-6 (N73Q-IL6). To examine the effect of the IL-6 glycoforms on differentiation of TAMs, THP-1 monocytic leukemic cells were incubated with phorbol-12-myristate 13-acetate for transforming to macrophages, followed by co-culture with the AS2 cell derivatives to mimic the education of TAMs. The co-cultured TAMs of each AS2 derivative showed distinct morphology. Intriguingly, the G-IL6-producing cells promote the expression of M2-TAM markers CD204, CCR1, arginase-1, and M2-specific cytokines that benefit anti-tumor activity, while DeCF-IL6 and N73Q-IL6 favored the formation of M1 macrophages. The phagocytosis capacity of cocultured macrophages is also altered by different IL-6 glycoform-secreting cells. On the other hand, the Stat3 activation status induced by IL-6 glycoforms is concordant to our previous results, in which the G-IL6 can induce a persistant Stat3 activation that is not observed in the DeCF-IL6- and N73Q-IL6-induced macrophages. We subsequently examined the distribution and polarization of TAMs in in vivo xenograft tumor model by both subcutaneous and intravenous injection of the IL-6 glycoform-overexpressing cells. Higher proportion of M2 TAM was attracted by the N73Q-IL6 tumor than other glycoform tumors. Together, we report the presence of specific IL-6 glycoforms secreted from lung cancer cells. Moreover, the glycosylation on IL-6 changes its activity on the polarization of TAMs, suggesting the pivotal role of soluble factor(s) in orchestrating the tumor microenvironment of lung cancer. Citation Format: Chun-Hua Hung, Hao-Chen Wang, Hsuan-Heng Yeh, Chien-Chung Lin, Wu-Chou Su. IL-6 glycoforms differentially modulate the polarization of tumor-associated macrophages in lung cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4157.

Background A cross-talk between different receptor tyrosine kinases (RTKs) plays an important role in the pathogenesis of human cancers. Methods Both NIH-Met5 and T24-Met3 cell lines harboring an inducible human c-Met gene were established. C-Met-related RTKs were screened by RTK microarray analysis. The cross-talk of RTKs was demonstrated by Western blotting and confirmed by small interfering RNA (siRNA) silencing, followed by elucidation of the underlying mechanism. The impact of this cross-talk on biological function was demonstrated by Trans-well migration assay. Finally, the potential clinical importance was examined in a cohort of 65 cases of locally advanced and metastatic bladder cancer patients. Results A positive association of Axl or platelet-derived growth factor receptor-alpha (PDGFR-α) with c-Met expression was demonstrated at translational level, and confirmed by specific siRNA knock-down. The transactivation of c-Met on Axl or PDGFR-α in vitro was through a ras- and Src-independent activation of mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK/ERK) pathway. In human bladder cancer, co-expression of these RTKs was associated with poor patient survival (p < 0.05), and overexpression of c-Met/Axl/PDGFR-α or c-Met alone showed the most significant correlation with poor survival (p < 0.01). Conclusions In addition to c-Met, the cross-talk with Axl and/or PDGFR-α also contributes to the progression of human bladder cancer. Evaluation of Axl and PDGFR-α expression status may identify a subset of c-Met-positive bladder cancer patients who may require co-targeting therapy.

The retinoblastoma suppressor (Rb)-associated protein 46 (RbAp46) is a nuclear protein of 46 kDa and contains four repeats that end with Trp-Asp (WD) residues. In this study, we reveal that the RbAp46 protein level upon SUMO-1 expression was increased. The increasing level of RbAp46 protein by SUMO-1 was not regulated at the transcriptional level. SUMO-1 does not affect the degradation of RbAp46. Co-localization of RbAp46 and SUMO-1 in the nuclei of stable NIH/3T3 cells harboring the inducible Ha-ras(Val12) oncogene (pSVlacOras) designated as 7-4, and protein-protein interaction between RbAp46 and SUMO-1 was also detected by co-immunoprecipitation in these cells. However, SUMO-l-related sumoylation was not involved in the modification of RbAp46. It is possibly that SUMO-1 acts through formation of complex with RbAp46 to stabilize RbAp46 protein. Overexpression of RbAp46 protein suppressed the NIH/3T3 cell growth induced by Ha-Ras(V12). SUMO-1 further enhances the suppression of cell growth through stabilization of RbAp46 protein. This is the first report to demonstrate that SUMO-1 can suppress Ras-related cell proliferation through stabilization of RbAp46 protein.

The ras oncogene needs a second factor to induce transformation and tumorigenicity of the cell. In this study, we show that mouse fibroblast 7-4-Stat3C cells overexpressing both Ha-ras(val12) oncogene and active-form Stat3 (Stat3C) showed higher colony formation in soft agar and xenograft tumor growth in BALB/c mice. Further studies show that both serine-727 and tyrosine-705 of Stat3 were phosphorylated while Ha-ras was overexpressed. Interleukin-6 (IL-6)-induced phosphorylation of tyrosine-705 and serine-727, as well as DNA-binding and transcriptional activity of Stat3 were further enhanced by Ha-ras overexpression. In addition, overexpression of Stat3C in 7-4-Stat3C cells prevented the cells from morphological change and apoptosis triggered by the Ha-ras oncogene under serum-depleted conditions. We demonstrate that Ha-ras and Stat3 acting together synergistically induce Stat3 phosphorylation at serine-727 phosphorylation and cyclin D1 expression and further enhance transformation and tumorigenicity of the cell. Ha-ras-induced Stat3 phosphorylation at serine-727 plays a pivotal role in transcriptional activation of cyclin D1 and suppression of cell apoptosis. The effect of Ha-ras on Stat3 phosphorylation at serine-727 was also detected in human bladder (T24) and lung (H460) cancer cells. Stat3 phosphorylation at serine-727 is important in Ras-related tumorigenesis.

Cell confluence induces the activation of signal transducer and activator of transcription-3 (Stat3) in various cancer and epithelial cells, yet the biological implications and the associated regulatory mechanisms remain unclear. Because confluent polarized epithelia demonstrate dome formation and sodium influx that mimic the onset of differentiation, we sought to elucidate the role of Stat3 in association with the regulation of selective epithelial transporters in this biological phenomenon. This study established the correlation between Stat3 activation and cell confluence-induced dome formation in Madin-Darby canine kidney cells (MDCK) by following Stat3 activation events in dome-forming cells. Epifluorescent and confocal microscopy provided evidence showing specific localization of phosphorylated Stat3 Tyr(705) in the nuclei of dome-forming cells at initial stages. The relationship was further elucidated by the establishment of tetracycline-inducible expression of constitutive Stat3 mutant (Stat3-C) in MDCK cells or expression of dominant negative Stat3 (Stat3-D) stable cell lines (MDCK and NMuMG). Dome formation was promoted by the expression of Stat3-C but inhibited by Stat3-D. Two trans-epithelial transporters, NHE3 and ENaC alpha-subunit, were found to be increased during cell confluence. Interestingly, NHE3 expression could be specifically up-regulated by Stat3-C but inhibited by Stat3-D through promoter regulation, whereas NHE1 and ENaC alpha-subunit were not affected by Stat3 expression. Application of NHE3 shRNA, NHE3 inhibitors (EIPA and S3226) suppressed confluence-induced dome formation in MDCK or NMuMG cells. These results demonstrate a cell confluence-induced Stat3 signaling pathway in epithelial cells in triggering dome formation through NHE3 augmentation.

Malignant pleural effusion (MPE) is a poor prognostic sign for patients with non-small-cell lung cancer (NSCLC). The generation of MPE is largely regulated by vascular endothelial growth factor (VEGF), and upregulation of VEGF by Stat3 has been observed in several types of tumor cells. In this study, we demonstrate constitutively activated Stat3 in several human lung cancer cell lines and in tumor cells infiltrated in the pleurae of patients with adenocarcinoma cell lung cancer (ADCLC) and MPE. The observations suggest that activated Stat3 plays a role in the pathogenesis of ADCLC. In PC14PE6/AS2 cells, a Stat3-positive human ADCLC cell line, autocrine IL-6 activated Stat3 via JAKs, not via Src kinase. PC14PE6/AS2 cells express higher VEGF mRNA and protein than do Stat3-negative PC14PE6/AS2/dnStat3 cells. In an animal model, PC14P6/AS2/dnStat3 cells produced no MPE and less lung metastasis than did PC14P6/AS2 cells. PC14PE6/AS2 cells also expressed higher VEGF protein, microvessel density, and vascular permeability in tumors than did PC14P6/AS2/dnStat3 cells. Therefore, we hypothesize that autocrine IL-6 activation of Stat3 in ADCLC may be involved in the formation of malignant pleural effusion by upregulating VEGF. Higher levels of IL-6 and VEGF were also found in the pleural fluids of patients with ADCLC than in patients with congestive heart failure. The autocrine IL-6/Stat3/VEGF signaling pathway may also be activated in patients with ADCLC and MPE. These findings provide novel targets for the management of MPE.

Aberrant activation of signal transducer and activator of transcription 3 (Stat3) occurs in many cancers and plays a critical role in tumor progression. The system that Stat3-induced Sphingosine-1-phosphate receptor 1 (S1PR1) expression and the S1P-S1PR1 pathway reciprocally regulate Stat3 activity was considered a major positive feedback loop for persistent Stat3 activation in cancer cells and the cells of tumor microenvironment. Tumor cells expressing the ligand for the receptor programmed death-1 (PD-1), PD-L1, have been shown to increase apoptosis of antigen-specific human T-cell to evade the immune system. In this study, we determined the influence of disrupting Stat3-S1PR1 vicious cycle on tumor formation and PD-L1 expression in lung cancer. We have established mutant Kras-induced lung cancer mice model and found that Stat3 phosphorylation was elevated in tumor tissues of lung cancer. Treatment of lung cancer cells with AG490 (JAK2 inhibitor) inhibited Stat3 activation and AG490 administration to the mice decreased the numbers of lung cancer nodules, indicating that blockage of Stat3 activation could inhibit mutant Kras-induced lung cancer in mice. Similar effects were also detected by using Stat3 inhibitor, S3I-201. We found that lung cancer cells expressed more pStat3 showed higher PD-L1 expression levels than that of lower pStat3 expressing cells. Inhibition of Stat3 activation by AG490 decreased PD-L1 expression in vitro and in vivo, indicating that PD-L1 expression could be regulated by Stat3. Moreover, FTY720 (S1P antagonist) could inhibit S1PR1 expression, down-regulate Stat3 activity, pJAK1 expression and inhibit IL-6 secretion in lung cancer cell lines and causes inhibition of the mutant Kras-induced lung cancer in mice. Furthermore, FTY720 administration dose-dependently suppressed tumor PD-L1 expression in mice lung cancer tissues. Taken together, our study indicated that FTY720 could suppress mutant Kras induced-lung cancer formation via inhibiting persistent Stat3 activation and down-regulating tumor PD-L1 expression. Citation Format: Hsuan-Heng Yeh, Tsung-I Hsu, Jan-Jong Hung, Wen-Pin Su, Wu-Chou Su. FTY720 inhibits mutant Kras-induced lung cancer via disrupting Stat3-S1PR1 vicious cycle and downregulating tumor PD-L1 expression. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2968. doi:10.1158/1538-7445.AM2014-2968

Interleukin-6 (IL-6) is overexpressed in various cancer cells, intriguingly contributing to both tumor growth and modulating anti-tumor immunity. Cell-type-specific glycosylations on IL-6 have been deduced in early studies; however, the glycosylation pattern and biological function of cancer cell-secreted IL-6 remain unclear. Here, we describe the glycosylation pattern of lung cancer cell-secreted IL-6 and its impact on the activation of JAK/STAT pathway. IL-6 molecules with different molecular weights were detected in the conditional media of IL-6-overexpressed lung cancer cell lines by immunoblot. Because in NetNGlyc 1.0 Server, one possible N-glycosylation site has been predicted at N73 on IL-6, we used treatment of N-glycosylation-specific inhibitors and site-directed mutagenesis on N73 to demonstrate that lung cancer cell-secreted IL-6 is modified by N-glycosylation. To examine which glycotransferases may participate in the modification, we had screened the expression of glycosyltransferases using qPCR and found that the expression of fucosyltransferase 8 (FUT8), responsible for core fucosylation on N-glycosylated proteins, was higher in lung cancer cells compared to normal bronchial cell. We then reduced core fucosylation on lung cancer cell-secreted IL-6 by silencing FUT8 with shRNA transduction. Subsequently, cells were treated with conditional media containing fully-glycosylated or core fucose-depleted IL-6 to uncover the potential influences on cellular signaling from glycosylation on IL-6. The fully-gycosylated IL-6 induced prolonged STAT3Y705 phosphorylation and distinct gene population compared to core fucose-depleted IL-6. The nuclear retention of STAT3 was concordant with the prolonged STAT3 activation in cells treated with fully-gycosylated IL-6. In paired normal (N) and tumor (T) tissues from lung cancer patients, higher FUT8 mRNA was detected in tumor part than normal part. Besides, we found similar glycosylation pattern in the secreted IL-6 of short-term cultured lung cancer cells derived from malignant pleural effusions. Together, we report the presence of specific IL-6 glycoforms secreted from lung cancer cell lines and lung cancer cells from clinical samples. Moreover, the glycosylation on IL-6 changes its activity on the regulation of JAK/STAT pathway. Citation Format: Chun-Hua Hung, Hsuan-Heng Yeh, Hao-Chen Wang, Chien-Chung Lin, Tsung-Lin Tsai, Wei-Lun Huang, Chuan-Fa Chang, Wu-Chou Su. N-glycosylation on lung cancer cell-secreted IL-6 prolongs its activation on JAK/STAT pathway. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3452. doi:10.1158/1538-7445.AM2014-3452

The antitumorigenic effects of metformin were mostly interpreted as attributing to the activation of LKB1-AMPK pathway and the studies investigating the AMPK-independent mechanism of metformin remained limited. In lung cancer, cisplatin-based chemotherapy remained the first line regimen for advanced lung cancer patients especially those without EGFR mutation. Previous study demonstrated the linkage between IL6-Stat3 autocrine and chemoresistance. In this study, we first showed that lung cancer line S3C (PC14PE6/AS2 cells with expressing plasmids containing constitutively-active Stat3) was more resistant to cisplatin than PC14PE6/AS2 cell. Treating lung cancer cells with Stat3 inhibitor (JSI-124) or metformin combined with cisplatin, the proliferation of cancer cells were inhibited additionally. And metformin inhibited Stat3 phosphorylation in PC14PE6/AS2 and A549 cells. To investigate the upstream mechanism associated Stat3 phosphorylation, we examined the secretion of IL-6 which was inhibited by metformin. And VEGF secretion, representing Stat3 downstream pathway, was inhibited by metformin in vitro and in vivo. Conversely, the secretion of VEGF was not inhibited in S3C cells after metformin treatment. However, using another AMPK activator-AICAR, the enhancement of cisplatin cytotoxicity is not obvious. In contrast to metformin, AICAR induced AMPK phosphorylation but Stat3 phosphorylation was not inhibited. To verify the LKB-AMPK independent effect of metformin on Stat3 phosphorylation, PC14PE6/AS2 cells were transfected with siRNA targeting LKB1 or AMPK. We demonstrated the inhibition of Stat3 phosphorylation of metformin even under the knockdown of LKB1-AMPK pathway. We also found that MTOR downstream signal including P70S6K and 4EBP1 were inhibited by metformin. Though previous study demonstrated MTOR pathway modulated Stat3 pathway, we found P70S6K and 4EBP1 phosphorylation were inhibited after treatment with metformin at 8hr and Stat3 phosphorylation change was detected after 24hr. Using MTOR inhibitor (rapamycin), the Stat3 tyrosine phosphorylation was not inhibited. Finally, we used subcutaneous tumor xenografts to evaluate the effect of combination of metformin with cisplatin in vivo. Body weight, blood sugar, and tumor volume were recorded in four groups including control, metformin, cisplatin, and metformin combined with cisplatin. Body weights and blood sugar were not different between combination treatment group and control group. In combination group, tumor stopped growing at 18th day and the tumor sizes were obvious less than the other three groups. Immunohistochemical staining of ki67 verified the lower proliferation in combination group. Our study demonstrated that metformin, independent of LKB1-AMPK pathway, inhibits Stat3 phosphorylation which contributes the enhancement of cisplatin cytotoxicity in lung cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3222. doi:1538-7445.AM2012-3222

Background Spontaneous interleukin-6 (IL-6) production has been observed in various tumors and implicated in the pathogenesis, progression and drug resistance in cancer. However, the regulation of IL-6 autocrine production in cancer cells is not fully understood. IL-6 is auto-regulated in many types of cell. Two of the three major downstream pathways of IL-6, MEK/extracellular signal-related kinase (Erk) pathway and phosphatidylinositol 3-kinase (PI3-K)/Akt pathway, have been shown to regulate IL-6 expression through the activation of AP-1 and NF-κB. However, it is not clear what the role of Janus kinase (Jak) 2/signal transducer and activator of transcription (Stat) 3 pathway. This study was designed to determine the role of Jak2/Stat3 pathway in the regulation of IL-6 autocrine production in cancer cells. Results Inhibitors of Jak2/Stat3, MEK/Erk and PI3-K/Akt pathways down-regulated IL-6 secretion in the lung adenocarcinoma PC14PE6/AS2 (AS2) cells, which spontaneously secreted IL-6 and possessed constitutively activated Stat3. Transfection with dominant-negative Stat3, Stat3 siRNA, or Stat3 shRNA decreased IL-6 expression in AS2 cells. Conversely, transfection with constitutively-activated Stat3 increased the production of IL-6. In AS2 derived cells, resistance to paclitaxel was positively correlated with Stat3 activation status and the expression of IL-6, which is commonly secreted in drug resistant cancer cells. The pharmacological inhibition of NF-κB, PI3-K/Akt and MEK/Erk and the pharmacological inhibition and genetic inhibition (Stat3 siRNA) of Jak2/Stat3 pathway decreased IL-6 autocrine production in various drug resistant cancer cell lines and similarly decreased IL-6 autocrine production in clinically isolated lung cancer cells. Conclusions This study is the first to directly address the role Stat3 plays on the autocrine production of IL-6, which occurs through a positive-feedback loop. Our biochemical and genetic studies clearly demonstrated that Jak2/Stat3, in combination with other IL-6 downstream pathways, contributed frequently and substantially to IL-6 autocrine production in a broad spectrum of cancer cell lines as well as in clinical cancer samples. Our findings suggest that Stat3 could potentially be regulated to suppress IL-6 autocrine production in cancer cells to inhibit the progression of cancer and reduce drug resistance.