Adipose tissue inflammation contributes to obesity-induced insulin resistance. However, increasing evidence shows that high BMI (obesity) is not an accurate predictor of poor metabolic health in individuals. The molecular mechanisms regulating the metabolically activated M1 macrophage phenotype in the adipose tissues leading to insulin resistance remain largely unknown. Although the Janus Kinase (Jak)/signal transducer and activator of transcription 3 (Stat3) signaling in myeloid cells are known to promote the M2 phenotype in tumors, we demonstrate here that the Jak2/Stat3 pathway amplifies M1-mediated adipose tissue inflammation and insulin resistance under metabolic challenges. Ablating Jak2 in the myeloid compartment reduces insulin resistance in obese mice, which is associated with a decrease in infiltration of adipose tissue macrophages (ATMs). We show that the adoptive transfer of Jak2-deficient myeloid cells improves insulin sensitivity in obese mice. Furthermore, the protection of obese mice with myeloid-specific Stat3 deficiency against insulin resistance is also associated with reduced tissue infiltration by macrophages. Jak2/Stat3 in the macrophage is required for the production of pro-inflammatory cytokines that promote M1 macrophage polarization in the adipose tissues of obese mice. Moreover, free fatty acids (FFAs) activate Stat3 in macrophages, leading to the induction of M1 cytokines. Silencing the myeloid cell Stat3 with an in vivo siRNA targeted delivery approach reduces metabolically activated pro-inflammatory ATMs, thereby alleviating obesity-induced insulin resistance. These results demonstrate Jak2/Stat3 in myeloid cells is required for obesity-induced insulin resistance and inflammation. Moreover, targeting Stat3 in myeloid cells may be a novel approach to ameliorate obesity-induced insulin resistance.

The participation of a specific subset of B cells and how they are regulated in cancer is unclear. Here, we demonstrate that the proportion of CD5(+) relative to interleukin-6 receptor alpha (IL-6R alpha)-expressing B cells was greatly increased in tumors. CD5(+) B cells responded to IL-6 in the absence of IL-6R alpha. IL-6 directly bound to CD5, leading to activation of the transcription factor STAT3 via gp130 and its downstream kinase JAK2. STAT3 upregulated CD5 expression, thereby forming a feed-forward loop in the B cells. In mouse tumor models, CD5(+) but not CD5(-) B cells promoted tumor growth. CD5(+) B cells also showed activation of STAT3 in multiple types of human tumor tissues. Thus, our findings demonstrate a critical role of CD5(+) B cells in promoting cancer.

Preclinical studies have suggested that VEGFR1-positive cells potentially foster the development of metastases by establishing a "premetastatic niche." We sought to test this hypothesis in high-risk localized prostate cancer and assess potential niche modulation by the VEGFR1-targeting drug axitinib. Formalin-fixed, paraffin-embedded tissue derived from benign lymph nodes was collected and VEGFR1-positive cell clustering was assessed in benign lymph nodes via IHC. Recursive partitioning was used to define a threshold for VEGFR1 clustering that could segregate patients based on time to biochemical recurrence (TTBR). Multivariate analyses were used to determine whether VEGFR1 clustering, age, pathologic T-stage, Gleason score, or baseline PSA could independently predict TTBR. A randomized, phase II clinical trial comparing axitinib for 28 days followed by radical prostatectomy and pelvic lymph node dissection (RP/PLND) to RP/LND alone was then conducted, with the primary endpoint of demonstrating downregulation of VEGFR1-positve cell clustering in benign lymph nodes. Our retrospective analysis assessed a cohort of 46 patients. A threshold of 1.65 VEGFR1-positive cells per high power field was identified, below which TTBR was delayed. VEGFR1 clustering was an independent predictor of TTBR in a multivariate analysis. Only 11 out of the planned 44 patients were accrued to the phase II trial. While preoperative axitinib was safe and well tolerated, there was no sign of clinical activity or VEGFR1 downregulation. Our results validate previous findings that suggest VEGFR1-positive cells in benign lymph nodes can predict clinical outcome. Further work is needed to develop a viable clinical strategy for modulating VEGFR1 in these tissues.

Increasing evidence suggests that premetastatic niches, consisting mainly of myeloid cells, provide microenvironment critical for cancer cell recruitment and survival to facilitate metastasis. While CD8+ T cells exert immunosurveillance in primary human tumors, whether they can exert similar effects on myeloid cells in the premetastatic environment is unknown. Here, we show that CD8+ T cells are capable of constraining premetastatic myeloid cell accumulation by inducing myeloid cell apoptosis in C57BL/6 mice. Ag‐specific CD8+ T‐cell cytotoxicity against myeloid cells in premetastatic lymph nodes is compromised by Stat3. We demonstrate here that Stat3 ablation in myeloid cells leads to CD8+ T‐cell activation and increased levels of IFN‐γ and granzyme B in the premetastatic environment. Furthermore, Stat3 negatively regulates soluble Ag cross‐presentation by myeloid cells to CD8+ T cells in the premetastatic niche. Importantly, in tumor‐free lymph nodes of melanoma patients, infiltration of activated CD8+ T cells inversely correlates with STAT3 activity, which is associated with a decrease in number of myeloid cells. Our study suggested a novel role for CD8+ T cells in constraining myeloid cell activity through direct killing in the premetastatic environment, and the therapeutic potential by targeting Stat3 in myeloid cells to improve CD8+ T‐cell immunosurveillance against metastasis.

Intracellular therapeutic targets that define tumor immunosuppression in both tumor cells and T cells remain intractable. Here, we have shown that administration of a covalently linked siRNA to an aptamer (apt) that selectively binds cytotoxic T lymphocyte-associated antigen 4 (CTLA4(apt)) allows gene silencing in exhausted CD8⁺ T cells and Tregs in tumors as well as CTLA4-expressing malignant T cells. CTLA4 expression was upregulated in CD8⁺ T cells in the tumor milieu; therefore, CTLA4(apt) fused to a STAT3-targeting siRNA (CTLA4(apt)-STAT3 siRNA) resulted in internalization into tumor-associated CD8⁺ T cells and silencing of STAT3, which activated tumor antigen-specific T cells in murine models. Both local and systemic administration of CTLA4(apt)-STAT3 siRNA dramatically reduced tumor-associated Tregs. Furthermore, CTLA4(apt)-STAT3 siRNA potently inhibited tumor growth and metastasis in various mouse tumor models. Importantly, CTLA4 expression is observed in T cells of patients with blood malignancies, and CTLA4(apt)-STAT3 siRNA treatment of immunodeficient mice bearing human T cell lymphomas promoted tumor cell apoptosis and tumor growth inhibition. These data demonstrate that a CTLA4(apt)-based siRNA delivery strategy allows gene silencing in both tumor-associated T cells and tumor cells and inhibits tumor growth and metastasis.

BACKGROUND:Signaling pathways underlying BV8-mediated oncogenesis remain unknown.RESULTS:BV8-STAT3 forms a feed-forward loop in both normal and malignant myeloid cells and promotes tumor growth.CONCLUSION:JAK2/STAT3 signaling plays critical roles in BV8-mediated myeloid cell-dependent oncogenesis.SIGNIFICANCE:This study identifies a novel role of BV8-STAT3 signaling in mediating cross-talk between tumor microenvironment and tumor cells. An important role of BV8 in mobilization of myeloid cells and myeloid cell-dependent angiogenesis has been established. Recently, it has also been shown that granulocyte colony-stimulating factor (G-CSF)-induced BV8 expression is STAT3 dependent in CD11b(+)Gr1(+) myeloid cells. However, the BV8 downstream signaling pathway(s) intrinsic to myeloid cells crucial for angiogenesis, and potentially also for development of cancers of myeloid origin, remains largely unknown. Here we show that BV8 activates STAT3, which is critical for regulating genes important for both tumor cell proliferation/survival and tumor angiogenesis, in both normal and malignant myeloid cells. Further, BV8-induced STAT3 activation requires Janus-activated kinase 2 (JAK2) activity as shown by both genetic and pharmacologic inhibition. Knocking down BV8 in human myeloid leukemia cells inhibits STAT3 activity and expression of STAT3 downstream angiogenic and pro-proliferation/survival genes, leading to a decrease in tumor cell viability. BV8 shRNA expressing leukemia cells exhibit reduced STAT3 activity and tumor growth in vivo. Taken together, we have delineated a signaling pathway downstream of BV8 that plays critical roles in both the tumor microenvironment and malignant myeloid cells for angiogenesis and tumor cell proliferation/survival.

STAT3 operates in both cancer cells and tumor-associated immune cells to promote cancer progression. As a transcription factor, it is a highly desirable but difficult target for pharmacologic inhibition. We have recently shown that the TLR9 agonists CpG oligonucleotides can be used for targeted siRNA delivery to mouse immune cells. In the present study, we demonstrate that a similar strategy allows for targeted gene silencing in both normal and malignant human TLR9(+) hematopoietic cells in vivo. We have developed new human cell-specific CpG(A)-STAT3 siRNA conjugates capable of inducing TLR9-dependent gene silencing and activation of primary immune cells such as myeloid dendritic cells, plasmacytoid dendritic cells, and B cells in vitro. TLR9 is also expressed by several human hematologic malignancies, including B-cell lymphoma, multiple myeloma, and acute myeloid leukemia. We further demonstrate that oncogenic proteins such as STAT3 or BCL-X(L) are effectively knocked down by specific CpG(A)-siRNAs in TLR9(+) hematologic tumor cells in vivo. Targeting survival signaling using CpG(A)-siRNAs inhibits the growth of several xenotransplanted multiple myeloma and acute myeloid leukemia tumors. CpG(A)-STAT3 siRNA is immunostimulatory and nontoxic for normal human leukocytes in vitro. The results of the present study show the potential of using tumoricidal/immunostimulatory CpG-siRNA oligonucleotides as a novel 2-pronged therapeutic strategy for hematologic malignancies.

Background: This study aimed to understand the role of myeloid cell clusters in uninvolved regional lymph nodes from early stage non-small cell lung cancer patients.Methods: Uninvolved regional lymph node sections from 67 patients with stage I-III resected non-small cell lung cancer were immunostained to detect myeloid clusters, STAT3 activity and occult metastasis. Anthracosis intensity, myeloid cluster infiltration associated with anthracosis and pSTAT3 level were scored and correlated with patient survival. Multivariate Cox regression analysis was performed with prognostic variables. Human macrophages were used for in vitro nicotine treatment.Results: CD68(+) myeloid clusters associated with anthracosis and with an immunosuppressive and metastasis-promoting phenotype and elevated overall STAT3 activity were observed in uninvolved lymph nodes. In patients with a smoking history, myeloid cluster score significantly correlated with anthracosis intensity and pSTAT3 level (P<0.01). Nicotine activated STAT3 in macrophages in long-term culture. CD68(+) myeloid clusters correlated and colocalized with occult metastasis. Myeloid cluster score was an independent prognostic factor (P = 0.049) and was associated with survival by Kaplan-Maier estimate in patients with a history of smoking (P = 0.055). The combination of myeloid cluster score with either lymph node stage or pSTAT3 level defined two populations with a significant difference in survival (P = 0.024 and P = 0.004, respectively).Conclusions: Myeloid clusters facilitate a pro-metastatic microenvironment in uninvolved regional lymph nodes and associate with occult metastasis in early stage non-small cell lung cancer. Myeloid cluster score is an independent prognostic factor for survival in patients with a history of smoking, and may present a novel method to inform therapy choices in the adjuvant setting. Further validation studies are warranted.

Signal transducer and activator of transcription-3 (STAT3) is critical for cancer progression by regulating tumor cell survival, proliferation, and angiogenesis. Herein, we investigated the regulation of STAT3 activation and the therapeutic effects of Icaritin, a prenyl flavonoid derivative from Epimedium Genus, in renal cell carcinoma (RCC). Icaritin showed significant antitumor activity in the human and mouse RCC cell lines, 786-O and Renca, respectively. Icaritin inhibited both constitutive and IL-6-induced phospho-STAT3 (STAT3(Y705)) and reduced the level of STAT3-regulated proteins Bcl-xL, Mcl-1, Survivin, and CyclinD1 in a dose-dependent manner. Icaritin also inhibited activation of Janus-activated kinase-2 (JAK2), while it showed minimal effects on the activation of other key signaling pathways, including AKT and MAPK. Expression of the constitutively active form of STAT3 blocked Icaritin-induced apoptosis, while siRNA directed against STAT3 potentiated apoptosis. Finally, Icaritin significantly blunted RCC tumor growth in vivo, reduced STAT3 activation, and inhibited Bcl-xL and Cyclin E, as well as VEGF expression in tumors, which was associated with reduced tumor angiogenesis. Overall, these results suggest that Icaritin strongly inhibits STAT3 activation and is a potentially effective therapeutic option for the treatment of renal cell carcinoma.

The role of B cells in cancer and the underlying mechanisms remain to be further explored. Here, we show that tumor-associated B cells with activated STAT3 contribute to tumor development by promoting tumor angiogenesis. B cells with or without Stat3 have opposite effects on tumor growth and tumor angiogenesis in both B16 melanoma and Lewis Lung Cancer mouse models. Ex vivo angiogenesis assays show that B cell-mediated tumor angiogenesis is mainly dependent on the induction of pro-angiogenic gene expression, which requires Stat3 signaling in B cells. Furthermore, B cells with activated STAT3 are mainly found in or near tumor vasculature and correlate significantly with overall STAT3 activity in human tumors. Moreover, the density of B cells in human tumor tissues correlates significantly with expression levels of several STAT3-downstream pro-angiogenic genes, as well as the degree of tumor angiogenesis. Together, these findings define a novel role of B cells in promoting tumor progression through angiogenesis and identify STAT3 in B cells as potential therapeutic target for anti-angiogenesis therapy.

Background: Several previous studies have identified a strong association between T-cell infiltration and clinical outcome in ovarian cancer. The role of B-cells remains controversial, however.Methods: Forty-nine paraffin-embedded omental specimens derived from patients with high grade epithelial ovarian cancer were assessed. Immunohistochemical analyses were performed to characterize expression of CD19+B-cells and pSTAT3 as high (>50% positively staining cells [PSCs]) or low (>50% PSCs). The Kaplan-Meier method with log-rank test was used to determine the association between clinicopathologic parameters and overall survival (OS). A multi-variate Cox proportional hazards regression analysis including nature of debulking (primary vs secondary), histology, tumor grade, receipt of prior chemotherapy, B-cell infiltration and pSTAT3 expression was performed.Results: Median OS was 160.6 months in those patients with low B-cell expression vs 47.3 months in those with high B-cell expression (P = 0.0015). Similarly, median OS was improved in those patients with low pSTAT3 expression (160.6 vs 47.9 months, P = 0.02). In a multivariate model to predict survival, only the degree of B-cell infiltration and clinical stage were retained. pSTAT3 expression did not enter the final model, possibly be due to a high positive correlation with B-cell infiltration (r = 0.82, P<0.0001).Conclusions: Increased B-cell infiltration and pSTAT3 expression in omental tissue are associated with poorer survival.

205 Background: High-risk prostate cancer (PCa) is a heterogeneous disease, and biomarkers that accurately predict clinical outcome within this subset are lacking. The pre-metastatic niche (PMN) represents one possible biomarker—this harbinger of future metastasis may be characterized by infiltration of VEGFR1+ cells [Kaplan et al Nature 139:820, 2005]. Given the predilection of PCa to spread to nodal sites, the association between VEGFR1 expression in benign pelvic lymph nodes and clinical outcome was examined. Methods: The City of Hope Prostate Cancer Registry (COH PCR) was used to identify 46 patients with high-risk PCa (baseline PSA > 20, pT3a-4 disease, or biopsy Gleason 8–10) who had undergone radical prostatectomy and pelvic lymph node dissection (PLND). The COH PCR prospectively collects clinical data associated with patients undergoing prostatectomy at the institution, and warehouses available clinical specimens. Benign tissue specimens derived from PLND were acquired for each patient, and were stained for VEGFR1 expression. VEGFR1+ cell clusters were counted within 8 distinct 40x fields, and the cluster count was averaged. Results: VEGFR1+ clustering in benign PLND specimens was a significant predictor of biochemical recurrence on multivariate Cox proportional hazards analysis, and outperformed other variables including established prognostic factors such as age, extracapsular spread, seminal vesicle invasion, and the aforementioned high-risk features. Patients with increased VEGFR1+ clustering pelvic lymph node tissue had a shorter interval to biochemical recurrence (HR 0.18, P<0.10). Conclusions: These preliminary results indicate that increased VEGFR1+ cell clustering in benign nodal tissue may predict poorer clinical outcome in patients with high-risk PCa. VEGFR1+ cells (a purported constituent of the PMN) represents a targetable entity. A randomized, phase II study employing axitinib (VEGFR1 IC50=1 nM) as neoadjuvant therapy in patients with high-risk PCa is nearing initiation at City of Hope ( NCT01385059 ).

Recent studies underscore the importance of myeloid cells in rendering distant organs hospitable for disseminating tumor cells to colonize. However, what enables myeloid cells to have an apparently superior capacity to colonize distant organs is unclear. Here, we show that S1PR1-STAT3 upregulation in tumor cells induces factors that activate S1PR1-STAT3 in various cells in premetastatic sites, leading to premetastatic niche formation. Targeting either S1PR1 or STAT3 in myeloid cells disrupts existing premetastatic niches. S1PR1-STAT3 pathway enables myeloid cells to intravasate, prime the distant organ microenvironment and mediate sustained proliferation and survival of their own and other stromal cells at future metastatic sites. Analyzing tumor-free lymph nodes from cancer patients shows elevated myeloid infiltrates, STAT3 activity, and increased survival signal.

STAT3 has important functions in both tumor cells and the tumor microenvironment to facilitate cancer progression. The STAT regulatory kinase Janus-activated kinase (JAK) has been strongly implicated in promoting oncogenesis of various solid tumors, including the use of JAK kinase inhibitors such as AZD1480. However, direct evidence that JAK drives STAT3 function and cancer pathogenesis at the level of the tumor microenvironment is yet to be established clearly. In this study, we show that AZD1480 inhibits STAT3 in tumor-associated myeloid cells, reducing their number and inhibiting tumor metastasis. Myeloid cell–mediated angiogenesis was also diminished by AZD1480, with additional direct inhibition of endothelial cell function in vitro and in vivo. AZD1480 blocked lung infiltration of myeloid cells and formation of pulmonary metastases in both mouse syngeneic experimental and spontaneous metastatic models. Furthermore, AZD1480 reduced angiogenesis and metastasis in a human xenograft tumor model. Although the effects of AZD1480 on the tumor microenvironment were important for the observed antiangiogenic activity, constitutive activation of STAT3 in tumor cells themselves could block these antiangiogenic effects, showing the complexity of the JAK/STAT signaling network in tumor progression. Together, our results indicated that AZD1480 can effectively inhibit tumor angiogenesis and metastasis mediated by STAT3 in stromal cells as well as tumor cells. Cancer Res; 71(21); 1–10. 2011 AACR.

Abstract Objectives: High-risk prostate cancer (PC) represents a heterogeneous disease, and metastatic potential varies within this subset of patients. The occurrence of metastasis involves both tumor cells and tumor-associated stromal cells. In the present study, murine models were used to examine the association between Stat3 activation and tumor-associated stromal cells. The latter may confer metastatic potential through the formation of pre-metastatic niches. These parameters were subsequently assessed in the benign lymph nodes of patients with high-risk PC. Methods: To induce pre-metastatic conditions, we injected tumor-conditioned media from murine tumor cell lines over-expressing the Stat3 activator, S1PR1, into C57BL/6 mice. Subsequently, mice were challenged with parental tumor cells via tail vein injection. For assessing a potential role of Stat3 in formation of the pre-metastatic niche, we analyzed mouse lung tissue by immunofluorescent staining and Western blot. We also increased and decreased myeloid cell Stat3 activity by retrovirus transduction and genetic ablation, respectively. For clinical correlation, paraffin-embedded lymph node tissue derived from 50 patients with high-risk PC was acquired. High-risk PC was defined by standard criteria as follows: (1) baseline prostate specific antigen (PSA) ≫ 20, (2) clinical stage T3a disease, or (3) Gleason score 8-10. Immunohistochemistry (IHC) staining was performed to assess pStat3 levels and CD68+ myeloid cell clustering. Results: In the murine models examined, increasing Stat3 activity in tumor cells by its newly identified activator, S1PR1, produced factors that activated Stat3 in lung tissue. This led to a dramatic increase in myeloid clustering and metastasis. Up-regulating Stat3 activity within myeloid cells enhanced the interaction between myeloid cells and endothelial cells in vivo, increased angiogenesis, and promoted subsequent formation of metastasis. In contrast, ablation of Stat3 in myeloid cells prevented the formation of pre-metastatic niches and metastasis. IHC staining of benign lymph node tissue in patients with high-risk PC yielded a spectrum of pStat3 levels. Higher levels of pStat3 were qualitatively associated with infiltration of CD68+ macrophages, appearing in distinct clusters. Conclusion: The current study indicates a critical role of Stat3 in promoting metastatic potential, possibly through mediating myeloid cell infiltration and formation of pre-metastatic niches. In the context of high-risk PC, differential levels of pStat3 and a potential association with myeloid cell clustering was observed. While correlation between these parameters and clinical outcome is ongoing, these preliminary findings suggest a putative role for Stat3 as a therapeutic target to prevent and/or reduce pre-metastatic niche formation and metastasis. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 405. doi:10.1158/1538-7445.AM2011-405

Abstract STAT3 has important functions in both tumor cells and the tumor microenvironment to facilitate cancer progression. The STAT regulatory kinase Janus-activated kinase (JAK) has been strongly implicated in promoting oncogenesis of various solid tumors, including the use of JAK kinase inhibitors such as AZD1480. However, direct evidence that JAK drives STAT3 function and cancer pathogenesis at the level of the tumor microenvironment is yet to be established clearly. In this study, we show that AZD1480 inhibits STAT3 in tumor-associated myeloid cells, reducing their number and inhibiting tumor metastasis. Myeloid cell–mediated angiogenesis was also diminished by AZD1480, with additional direct inhibition of endothelial cell function in vitro and in vivo. AZD1480 blocked lung infiltration of myeloid cells and formation of pulmonary metastases in both mouse syngeneic experimental and spontaneous metastatic models. Furthermore, AZD1480 reduced angiogenesis and metastasis in a human xenograft tumor model. Although the effects of AZD1480 on the tumor microenvironment were important for the observed antiangiogenic activity, constitutive activation of STAT3 in tumor cells themselves could block these antiangiogenic effects, showing the complexity of the JAK/STAT signaling network in tumor progression. Together, our results indicated that AZD1480 can effectively inhibit tumor angiogenesis and metastasis mediated by STAT3 in stromal cells as well as tumor cells. Cancer Res; 71(21); 6601–10. ©2011 AACR.

Abstract Objectives: Surgical resection offers the most promising chance for cure in patients who present with early-stage disease, although the majority will experience recurrence due to microscopic disease at the time of surgery. In this study, we sought to identify markers of metastatic potential within benign regional lymph nodes of patients with completely resected non-small cell lung cancer (NSCLC) with a focus on VEGFR-1, myeloid cells and pStat3. Methods: Paraffin-embedded benign pulmonary lymph node specimens from 46 lung cancer patients with stage I-III resected disease were stained for CD68 (AbD Serotec, Raleigh, NC), CD163 (AbD Serotec, Raleigh, NC), VEGFR-1 (Santa Cruz, Santa Cruz, CA), phospho-Stat3 (Cell Signaling, Danvers, MA), MMP-9 (Cell Signaling, Danvers, MA) and VEGF-A (Abcam, Cambridge, MA) by immunohistochemistry or immunofluorescence. Anthracosis in the lymph nodes was evaluated using HE-stained sections. The sections were analyzed with Image Pro Plus or evaluated by two independent observers who were not aware of the patient information (double-blinded). Results: In benign lymph nodes from resected lung cancer patients, CD68 was highly expressed, while VEGFR-1 demonstrated low expression. Furthermore, these cells were associated with anthracotic deposition. Upon additional evaluation, we found that the infiltrating cells with anthracotic pigment display CD68+ CD163+, suggestive of an M2 macrophage phenotype, which are immunosuppressive and cancer promoting. These M2 macrophages expressed MMP-9 and VEGF-A, and in at least 40% of the patient lymph node tissue, pStat3 was elevated in these anthracotic macrophages. The infiltration of CD68+ macrophages was closely correlated with the intensity of anthracosis (P<0.0001, One-way ANOVA). In some lymph nodes, the infiltration of M2 macrophages was dramatically increased. We also observed positive correlations between overall pStat3 level with M2 macrophage infiltration and anthracosis intensity (P<0.05 and P<0.01, respectively, One-way ANOVA). In addition, pStat3 levels in anthracotic cells increased with the intensity of anthracosis in the lymph nodes. Conclusion: Our results indicate the presence of M2 macrophages and anthracosis in benign lymph nodes of patients with stage I-III NSCLC. The infiltration of M2 macrophages in benign pulmonary lymph nodes might serve as a predictive factor for micrometastasis and patient prognosis. Correlations between M2 macrophage in lymph nodes with smoking status, patient stage and survival will also be evaluated. Supported by NIH R01 CA115815 (hy) and NIH K12 CA001727 (klr; skp). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 407. doi:10.1158/1538-7445.AM2011-407

Abstract Inflammatory conditions elicited by extrinsic environmental factors promote malignant cell transformation, tumor growth, and metastasis. Although most attention has been focused on innate immune mechanisms of inflammatory carcinogenesis, more recently the role of T cells in cancer promotion has been examined. Although IFN-dependent Th1 responses that promote Stat1 signaling inhibit tumor growth, the role of T helper type 17 responses, and interleukin-17 (IL-17) in particular, has been controversial. Indeed, IL-17 has been reported to either enhance or inhibit the growth of transplantable tumors, depending on the system. Little is known about the role of IL-17 in de novo carcinogenesis. Using IL-17 knockout mice, we examined the role of IL-17 in the classic DMBA/TPA-induced skin carcinogenesis model. Disruption of IL-17 dramatically reduced tumorigenesis in this model in a manner correlated with diminished Stat3 activation in the tumor microenvironment. IL-17 loss reduced Stat3-associated proliferative and antiapoptotic gene expression along with epidermal cell proliferation and hyperplasia. In addition, IL-17 loss was associated with reduced expression of Stat3-regulated chemokines that attract myeloid cells and a decreased infiltration of myeloid cells into the local tumor microenvironment. Together, our findings point to a critical role of the IL-17–Stat3 pathway in supporting cancer-associated inflammation in the tumor microenvironment. Therapeutic approaches that target this pathway may therefore be effective to inhibit carcinogenesis. Cancer Res; 70(24); 10112–20. ©2010 AACR.