[Early immune reconstitution after hematopoietic stem cell transplantation]

OBJECTIVE

To search for differences in early immune reconstitution after allogenic or autologous hematopoietic stem cell transplantation (HSCT).

METHODS

The peripheral blood (PB) from 31 adult patients undergoing allogenic HSCT (allo-HSCT, 15 patients) or autologous HSCT (auto-HSCT, 16 patients) for the treatment of hematological malignancies and from 20 related healthy controls (HC) from December 2011 to August 2014 was used to analyze the kinetic recovery of lymphocyte subsets by means of flow cytometry during 12 months after HSCT. The T cell receptor rearrangement excision circle (TREC) levels among CD3(+) T cells were measured in the patients and HC to evaluate the thymic-dependent T cell reconstitution.

RESULTS

The allo- and auto-HSCT recipients did not differ significantly in CD4(+) T cells, CD8 naive T cells, effecter memory T cells (TEM), CD4 central memory T cells (TCM), mid-activated T cells and dendritic cells (DC)during the follow-up (P>0.05). But they both differed significantly from HC (P<0.05). CD8(+) T cells and NK cells reconstructed rapidly. There was no significant difference in the numbers of B cells between the allo- and auto-HSCT groups from M1 to M3 (P>0.05). B cells in both the groups were lower than those in HC (P<0.05). The recovery of B cells in auto-HSCT group was faster than in allo-HSCT group at M6 and M12 (P<0.05). The frequencies of CD4 naive T cells and later activated T cells in allo-HSCT group were significantly higher than in auto-HSCT group at M6 and M12 (P<0.05). The frequencies of CD8 TCM in auto-HSCT group were significantly higher than in allo-HSCT group at M6 and M12 (P<0.05). The TREC levels were significantly lower than in both the groups compared with the age-matched HC during the follow-up (P<0.05). No significant difference was observed between allo-HSCT and auto-HSCT groups (P>0.05).

CONCLUSION

The differences of the nature and the speed of lymphocyte reconstitution observed between the two patents groups were minor. This leads us to conclude that in allografted patients, immune reconstitution and subpopulations of peripheral blood lymphocytes are probably not related to the allogenicity of the graft, but due to the impaired thymus functions and slow differentiation of T lymphocytes in thymus.

Loss of c-Kit and bone marrow failure upon conditional removal of the GATA-2 C-terminal zinc finger domain in adult mice

Heterozygous mutations in the transcriptional regulator GATA-2 associate with multilineage immunodeficiency, myelodysplastic syndrome (MDS), and acute myeloid leukemia (AML). The majority of these mutations localize in the zinc finger (ZnF) domains, which mediate GATA-2 DNA binding. Deregulated hematopoiesis with GATA-2 mutation frequently develops in adulthood, yet GATA-2 function in the bone marrow remains unresolved. To investigate this, we conditionally deleted the GATA-2 C-terminal ZnF (C-ZnF) coding sequences in adult mice. Upon Gata2 C-ZnF deletion, we observed rapid peripheral cytopenia, bone marrow failure, and decreased c-Kit expression on hematopoietic progenitors. Transplant studies indicated GATA-2 has a cell-autonomous role in bone marrow hematopoiesis. Moreover, myeloid lineage populations were particularly sensitive to Gata2 hemizygosity, while molecular assays indicated GATA-2 regulates c-Kit expression in multilineage progenitor cells. Enforced c-Kit expression in Gata2 C-ZnF-deficient hematopoietic progenitors enhanced myeloid colony activity, suggesting GATA-2 sustains myelopoiesis via a cell intrinsic role involving maintenance of c-Kit expression. Our results provide insight into mechanisms regulating hematopoiesis in bone marrow and may contribute to a better understanding of immunodeficiency and bone marrow failure associated with GATA-2 mutation.

Loss of PTEN Promotes Resistance to T Cell-Mediated Immunotherapy

T cell-mediated immunotherapies are promising cancer treatments. However, most patients still fail to respond to these therapies. The molecular determinants of immune resistance are poorly understood. We show that loss of PTEN in tumor cells in preclinical models of melanoma inhibits T cell-mediated tumor killing and decreases T-cell trafficking into tumors. In patients, PTEN loss correlates with decreased T-cell infiltration at tumor sites, reduced likelihood of successful T-cell expansion from resected tumors, and inferior outcomes with PD-1 inhibitor therapy. PTEN loss in tumor cells increased the expression of immunosuppressive cytokines, resulting in decreased T-cell infiltration in tumors, and inhibited autophagy, which decreased T cell-mediated cell death. Treatment with a selective PI3Kβ inhibitor improved the efficacy of both anti-PD-1 and anti-CTLA-4 antibodies in murine models. Together, these findings demonstrate that PTEN loss promotes immune resistance and support the rationale to explore combinations of immunotherapies and PI3K-AKT pathway inhibitors.

SIGNIFICANCE

This study adds to the growing evidence that oncogenic pathways in tumors can promote resistance to the antitumor immune response. As PTEN loss and PI3K-AKT pathway activation occur in multiple tumor types, the results support the rationale to further evaluate combinatorial strategies targeting the PI3K-AKT pathway to increase the efficacy of immunotherapy.

Loss of PTEN Promotes Resistance to T Cell-Mediated Immunotherapy

T cell-mediated immunotherapies are promising cancer treatments. However, most patients still fail to respond to these therapies. The molecular determinants of immune resistance are poorly understood. We show that loss of PTEN in tumor cells in preclinical models of melanoma inhibits T cell-mediated tumor killing and decreases T-cell trafficking into tumors. In patients, PTEN loss correlates with decreased T-cell infiltration at tumor sites, reduced likelihood of successful T-cell expansion from resected tumors, and inferior outcomes with PD-1 inhibitor therapy. PTEN loss in tumor cells increased the expression of immunosuppressive cytokines, resulting in decreased T-cell infiltration in tumors, and inhibited autophagy, which decreased T cell-mediated cell death. Treatment with a selective PI3Kβ inhibitor improved the efficacy of both anti-PD-1 and anti-CTLA-4 antibodies in murine models. Together, these findings demonstrate that PTEN loss promotes immune resistance and support the rationale to explore combinations of immunotherapies and PI3K-AKT pathway inhibitors.

SIGNIFICANCE

This study adds to the growing evidence that oncogenic pathways in tumors can promote resistance to the antitumor immune response. As PTEN loss and PI3K-AKT pathway activation occur in multiple tumor types, the results support the rationale to further evaluate combinatorial strategies targeting the PI3K-AKT pathway to increase the efficacy of immunotherapy.

Loss of PTEN Promotes Resistance to T Cell-Mediated Immunotherapy

T cell-mediated immunotherapies are promising cancer treatments. However, most patients still fail to respond to these therapies. The molecular determinants of immune resistance are poorly understood. We show that loss of PTEN in tumor cells in preclinical models of melanoma inhibits T cell-mediated tumor killing and decreases T-cell trafficking into tumors. In patients, PTEN loss correlates with decreased T-cell infiltration at tumor sites, reduced likelihood of successful T-cell expansion from resected tumors, and inferior outcomes with PD-1 inhibitor therapy. PTEN loss in tumor cells increased the expression of immunosuppressive cytokines, resulting in decreased T-cell infiltration in tumors, and inhibited autophagy, which decreased T cell-mediated cell death. Treatment with a selective PI3Kβ inhibitor improved the efficacy of both anti-PD-1 and anti-CTLA-4 antibodies in murine models. Together, these findings demonstrate that PTEN loss promotes immune resistance and support the rationale to explore combinations of immunotherapies and PI3K-AKT pathway inhibitors.

SIGNIFICANCE

This study adds to the growing evidence that oncogenic pathways in tumors can promote resistance to the antitumor immune response. As PTEN loss and PI3K-AKT pathway activation occur in multiple tumor types, the results support the rationale to further evaluate combinatorial strategies targeting the PI3K-AKT pathway to increase the efficacy of immunotherapy.

Macrophage proinflammatory response to the titanium alloy equipment in dental implantation

Titanium alloy and stainless steel (SS) had been widely used as dental implant materials because of their affinity with epithelial tissue and connective tissue, and good physical, chemical, biological, mechanical properties and processability. We compared the effects of titanium alloy and SS on macrophage cytokine expression as well as their biocompatibility. Mouse macrophage RAW264.7 cells were cultured on titanium alloy and SS surfaces. Cells were counted by scanning electron microscopy. A nitride oxide kit was used to detect released nitric oxide by macrophages on the different materials. An enzyme linked immunosorbent assay was used to detect monocyte chemoattractant protein-1 levels. Scanning electron microscopy revealed fewer macrophages on the surface of titanium alloy (48.2 ± 6.4 x 10(3) cells/cm(2)) than on SS (135 ± 7.3 x 10(3) cells/cm(2)). The nitric oxide content stimulated by titanium alloy was 22.5 mM, which was lower than that stimulated by SS (26.8 mM), but the difference was not statistically significant (P = 0.07). The level of monocyte chemoattractant protein-1 released was significantly higher in the SS group (OD value = 0.128) than in the titanium alloy group (OD value = 0.081) (P = 0.024). The transforming growth factor-b1 mRNA expression levels in macrophages after stimulation by titanium alloy for 12 and 36 h were significantly higher than that after stimulation by SS (P = 0.31 and 0.25, respectively). Macrophages participate in the inflammatory response by regulating cytokines such as nitric oxide, monocyte chemoattractant protein-1, and transforming growth factor-b1. There were fewer macrophages and lower inflammation on the titanium alloy surface than on the SS surface. Titanium alloy materials exhibited better biological compatibility than did SS.

Moussalli MJ, Elias E, Li HS, Watowich SS, Shureiqi I. Abstract 1959: 15-lipoxygenase-1 suppression of colitis-associated colon cancer through inhibition of the IL-6/STAT3 signaling pathway

The IL-6/STAT3 pathway is a critical signaling pathway for colitis-associated colorectal cancer (CAC). PPAR-delta (PPAR-d), a lipid nuclear receptor, upregulates IL-6. 15-Lipoxygenase-1 (15-LOX-1) is crucial to produce lipid signaling mediators to terminate inflammation. 15-LOX-1 downregulates PPAR-d. 15-LOX-1 effects on IL-6/STAT3 signaling and CAC tumorigenesis are unknown. We here report that intestinally targeted transgenic 15-LOX-1 expression in mice (15-LOX-1-Gut mice) inhibited azoxymethane and dextran sodium sulfate-induced CAC, IL-6 expression, STAT3 phosphorylation, and IL-6/STAT3 downstream target expression (Notch and MUC1). 15-LOX-1 downregulation was associated with IL-6 upregulation in human colon cancer mucosa. Re-expression of 15-LOX-1 in human colon cancer cells suppressed IL-6 mRNA expression, STAT3 phosphorylation, IL-6 promoter activity, and PPAR-d mRNA and protein expression. PPAR-d overexpression in colonic epithelial cells (PPAR-d-Gut mice) promoted CAC tumorigenesis in mice and increased IL-6 expression and STAT3 phosphorylation, whereas concomitant 15-LOX-1 expression in colonic epithelial cells (15-LOX-1-PPAR-d-Gut mice) suppressed these effects [e.g., tumor number per mouse (mean ± SE) was 4.22 ± 0.68 in wild-type littermates, 6.67 ± 0.83 in PPAR-d-Gut mice (p = 0.026), and 2.25 ± 0.25 in 15-LOX-1-PPAR-d-Gut mice (p = 0.0006)]. Identification of 15-LOX-1 suppression of PPAR-d to inhibit IL-6/STAT3 signaling-driven CAC tumorigenesis provides mechanistic insights that can be utilized to molecularly target CAC.

Citation Format: Xiangsheng Zuo, Fei Mao, Min Xu, Weiguo Xu, Rui Tian, Micheline J. Micheline J. Moussalli, Elias Elias, Haiyan S. Li, Stephanie S. Watowich, Imad Shureiqi. 15-lipoxygenase-1 suppression of colitis-associated colon cancer through inhibition of the IL-6/STAT3 signaling pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1959. doi:10.1158/1538-7445.AM2015-1959

Innate immune regulation by STAT-mediated transcriptional mechanisms

The term innate immunity typically refers to a quick but non-specific host defense response against invading pathogens. The innate immune system comprises particular immune cell populations, epithelial barriers, and numerous secretory mediators including cytokines, chemokines, and defense peptides. Innate immune cells are also now recognized to play important contributing roles in cancer and pathological inflammatory conditions. Innate immunity relies on rapid signal transduction elicited upon pathogen recognition via pattern recognition receptors (PRRs) and cell:cell communication conducted by soluble mediators, including cytokines. A majority of cytokines involved in innate immune signaling use a molecular cascade encompassing receptor-associated Jak protein tyrosine kinases and STAT (signal transducer and activator of transcription) transcriptional regulators. Here, we focus on roles for STAT proteins in three major innate immune subsets: neutrophils, macrophages, and dendritic cells (DCs). While knowledge in this area is only now emerging, understanding the molecular regulation of these cell types is necessary for developing new approaches to treat human disorders such as inflammatory conditions, autoimmunity, and cancer.

15-Lipoxygenase-1 suppression of colitis-associated colon cancer through inhibition of the IL-6/STAT3 signaling pathway

The IL-6/signal transducer and activator of transcription 3 (STAT3) pathway is a critical signaling pathway for colitis-associated colorectal cancer (CAC). Peroxisome proliferator-activated receptor (PPAR)-δ, a lipid nuclear receptor, up-regulates IL-6. 15-Lipoxygenase-1 (15-LOX-1), which is crucial to production of lipid signaling mediators to terminate inflammation, down-regulates PPAR-δ. 15-LOX-1 effects on IL-6/STAT3 signaling and CAC tumorigenesis have not been determined. We report that intestinally targeted transgenic 15-LOX-1 expression in mice inhibited azoxymethane- and dextran sodium sulfate-induced CAC, IL-6 expression, STAT3 phosphorylation, and IL-6/STAT3 downstream target (Notch3 and MUC1) expression. 15-LOX-1 down-regulation was associated with IL-6 up-regulation in human colon cancer mucosa. Reexpression of 15-LOX-1 in human colon cancer cells suppressed IL-6 mRNA expression, STAT3 phosphorylation, IL-6 promoter activity, and PPAR-δ mRNA and protein expression. PPAR-δ overexpression in colonic epithelial cells promoted CAC tumorigenesis in mice and increased IL-6 expression and STAT3 phosphorylation, whereas concomitant 15-LOX-1 expression in colonic epithelial cells (15-LOX-1-PPAR-δ-Gut mice) suppressed these effects: the number of tumors per mouse (mean ± sem) was 4.22 ± 0.68 in wild-type littermates, 6.67 ± 0.83 in PPAR-δ-Gut mice (P = 0.026), and 2.25 ± 0.25 in 15-LOX-1-PPAR-δ-Gut mice (P = 0.0006). Identification of 15-LOX-1 suppression of PPAR-δ to inhibit IL-6/STAT3 signaling-driven CAC tumorigenesis provides mechanistic insights that can be used to molecularly target CAC.

STAT3 restrains RANK- and TLR4-mediated signalling by suppressing expression of the E2 ubiquitin-conjugating enzyme Ubc13

The transcriptional regulator STAT3 curbs pro-inflammatory cytokine production mediated by NF-κB signaling in innate immune cells, yet the mechanism by which this occurs has been unclear. Here we identify STAT3 as a pivotal negative regulator of Ubc13, an E2 ubiquitin-conjugating enzyme that facilitates TRAF6 K63-linked ubiquitination and NF-κB activation. Ubc13 accumulates intracellularly in the absence of STAT3. Depletion of Ubc13 in Stat3-deficient macrophages subdues excessive RANKL- or LPS-dependent gene expression, indicating Ubc13 overexpression mediates enhanced transcriptional responses in the absence of STAT3. In RANKL-activated macrophages, STAT3 is stimulated by autocrine IL-6 and inhibits accrual of Ets-1, Set1 methyltransferase and trimethylation of histone H3 lysine 4 (H3K4me3) at the Ube2n (Ubc13) promoter. These results delineate a mechanism by which STAT3 operates as a transcriptional repressor on Ube2n, thus modulating NF-κB activity by regulation of Ubc13 abundance. Our data suggest this pathway plays important roles in bone homeostasis and restraint of inflammation.

Pathological analysis of extracapsular extension of metastatic lymph node and its potential impact on nodal clinical target volume in the radiotherapy of esophageal squamous cell carcinoma

There is no consensus regarding the clinical target volume (CTV) margins which surround the gross tumor volume of metastatic lymph nodes (LN) in radiotherapy of esophageal squamous cell carcinoma (ESCC). This study retrospectively assessed the distance of extracapsular extension (ECE) of metastatic LN in thoracic ESCC and defined nodal CTV margins. Histological sections of metastatic LNs from 217 patients with thoracic ESCC were re-examined. The incidence and maximal distance of ECE of metastatic LNs were assessed. The relationships between ECE and clinicopathologic features were also investigated. The ECE was found in 37.3% of patients (81/217) and 23.1% of metastatic LN (159/689), and the incidences had a significant relationship with N stage and LN size. The median distance of ECE was 1.0 mm (range, 0.2-9.7 mm). The distance of ECE showed a positive correlation with LN size (Spearman's correlation coefficient = 0.419; p<0.001). The ECE distances of LN with <10 mm diameter were significantly smaller than LN with 10-30 mm diameter (p<0.001). The 95th percentiles of ECE distances for these two groups were 3 mm and 5 mm, respectively. For pathologic LN <10 mm in diameter, a 3-mm CTV margin appears to be adequate to encompass 95% of the microscopic ECE, and for LN 10-30 mm, a 5-mm CTV margin is recommended.

USP15 stabilizes MDM2 to mediate cancer-cell survival and inhibit antitumor T cell responses

Deubiquitinases (DUBs) are a new class of drug targets, although the physiological function of only few DUBs has been characterized. Here we identified the DUB USP15 as a crucial negative regulator of T cell activation. USP15 stabilized the E3 ubiquitin ligase MDM2, which in turn negatively regulated T cell activation by targeting the degradation of the transcription factor NFATc2. USP15 deficiency promoted T cell activation in vitro and enhanced T cell responses to bacterial infection and tumor challenge in vivo. USP15 also stabilized MDM2 in cancer cells and regulated p53 function and cancer-cell survival. Our results suggest that inhibition of USP15 may both induce tumor cell apoptosis and boost antitumor T cell responses.

Noncanonical NF-κB pathway controls the production of type I interferons in antiviral innate immunity

Production of type I interferons (IFN-I) is a crucial innate immune mechanism against viral infections. IFN-I induction is subject to negative regulation by both viral and cellular factors, but the underlying mechanism remains unclear. We report that the noncanonical NF-κB pathway was stimulated along with innate immune cell differentiation and viral infections and had a vital role in negatively regulating IFN-I induction. Genetic deficiencies in major components of the noncanonical NF-κB pathway caused IFN-I hyperinduction and rendered cells and mice substantially more resistant to viral infection. Noncanonical NF-κB suppressed signal-induced histone modifications at the Ifnb promoter, an action that involved attenuated recruitment of the transcription factor RelA and a histone demethylase, JMJD2A. These findings reveal an unexpected function of the noncanonical NF-κB pathway and highlight an important mechanism regulating antiviral innate immunity.

Assessing the development of murine plasmacytoid dendritic cells in Peyer's patches using adoptive transfer of hematopoietic progenitors

This protocol details a method to analyze the ability of purified hematopoietic progenitors to generate plasmacytoid dendritic cells (pDC) in intestinal Peyer's patch (PP). Common dendritic cell progenitors (CDPs, lin(-) c-kit(lo) CD115(+) Flt3(+)) were purified from the bone marrow of C57BL6 mice by FACS and transferred to recipient mice that lack a significant pDC population in PP; in this case, Ifnar(-/-) mice were used as the transfer recipients. In some mice, overexpression of the dendritic cell growth factor Flt3 ligand (Flt3L) was enforced prior to adoptive transfer of CDPs, using hydrodynamic gene transfer (HGT) of Flt3L-encoding plasmid. Flt3L overexpression expands DC populations originating from transferred (or endogenous) hematopoietic progenitors. At 7-10 days after progenitor transfer, pDCs that arise from the adoptively transferred progenitors were distinguished from recipient cells on the basis of CD45 marker expression, with pDCs from transferred CDPs being CD45.1(+) and recipients being CD45.2(+). The ability of transferred CDPs to contribute to the pDC population in PP and to respond to Flt3L was evaluated by flow cytometry of PP single cell suspensions from recipient mice. This method may be used to test whether other progenitor populations are capable of generating PP pDCs. In addition, this approach could be used to examine the role of factors that are predicted to affect pDC development in PP, by transferring progenitor subsets with an appropriate knockdown, knockout or overexpression of the putative developmental factor and/or by manipulating circulating cytokines via HGT. This method may also allow analysis of how PP pDCs affect the frequency or function of other immune subsets in PPs. A unique feature of this method is the use of Ifnar(-/-) mice, which show severely depleted PP pDCs relative to wild type animals, thus allowing reconstitution of PP pDCs in the absence of confounding effects from lethal irradiation.

Diversification of dendritic cell subsets: Emerging roles for STAT proteins

The term dendritic cell (DC) refers to a population of hematopoietic cells with critical roles in immunity, including immune activation in response to pathogen-elicited danger signals and immune tolerance. Aberrant DC activity is an important contributing factor in autoimmunity, while severe DC depletion accompanies certain immunodeficiency conditions. By contrast, DCs have become attractive candidates to manipulate in immune therapy. Recent studies show that STAT transcription factors have unique roles in DCs, a feature that might be exploited in future DC-based therapies. Here, we focus on the functions of STAT1, STAT3, and STAT5 in DC generation and DC-mediated immune responses.

BRAF inhibition increases tumor infiltration by T cells and enhances the antitumor activity of adoptive immunotherapy in mice

PURPOSE

Treatment of melanoma patients with selective BRAF inhibitors results in objective clinical responses in the majority of patients with BRAF-mutant tumors. However, resistance to these inhibitors develops within a few months. In this study, we test the hypothesis that BRAF inhibition in combination with adoptive T-cell transfer (ACT) will be more effective at inducing long-term clinical regressions of BRAF-mutant tumors.

EXPERIMENTAL DESIGN

BRAF-mutated human melanoma tumor cell lines transduced to express gp100 and H-2D(b) to allow recognition by gp100-specific pmel-1 T cells were used as xenograft models to assess melanocyte differentiation antigen-independent enhancement of immune responses by BRAF inhibitor PLX4720. Luciferase-expressing pmel-1 T cells were generated to monitor T-cell migration in vivo. The expression of VEGF was determined by ELISA, protein array, and immunohistochemistry. Importantly, VEGF expression after BRAF inhibition was tested in a set of patient samples.

RESULTS

We found that administration of PLX4720 significantly increased tumor infiltration of adoptively transferred T cells in vivo and enhanced the antitumor activity of ACT. This increased T-cell infiltration was primarily mediated by the ability of PLX4720 to inhibit melanoma tumor cell production of VEGF by reducing the binding of c-myc to the VEGF promoter. Furthermore, analysis of human melanoma patient tumor biopsies before and during BRAF inhibitor treatment showed downregulation of VEGF consistent with the preclinical murine model.

CONCLUSION

These findings provide a strong rationale to evaluate the potential clinical application of combining BRAF inhibition with T-cell-based immunotherapy for the treatment of patients with melanoma.

miR-22 controls Irf8 mRNA abundance and murine dendritic cell development

MicroRNAs (miRNAs) have emerged as critical regulators of many cellular responses, through the action of miRNA-induced silencing complex (miRISC)- or miRNA ribonucleoprotein complex (miRNP)-mediated gene repression. Here we studied the role of miRNAs in the development of dendritic cells (DCs), an important immune cell type that is divided into conventional DC (cDC) and plasmacytoid DC (pDC) subsets. We found that miR-22 was highly expressed in mouse CD11c⁺ CD11b⁺ B220⁻ cDCs compared to pDCs, and was induced in DC progenitor cell cultures with GM-CSF, which stimulate CD11c⁺ CD11b⁺ B220⁻ cDC differentiation. Enforced overexpression of miR-22 during DC development enhanced CD11c⁺ CD11b⁺ B220⁻ cDC generation at the expense of pDCs, while miR-22 knockdown demonstrated opposite effects. Moreover, overexpression and knockdown of miR-22 showed significant effects on the mRNA abundance of Irf8, which encodes the transcription factor IRF8 that plays essential roles in DC development. Luciferase reporter assays confirmed that miR-22 binds directly to the 3′UTR of the mouse Irf8 mRNA. Collectively, these results suggest that miR-22 targets Irf8 mRNA for posttranscriptional repression and controls DC subset differentiation.

BRAF inhibition increases tumor infiltration by T cells and enhances the antitumor activity of adoptive immunotherapy in mice

PURPOSE

Treatment of melanoma patients with selective BRAF inhibitors results in objective clinical responses in the majority of patients with BRAF-mutant tumors. However, resistance to these inhibitors develops within a few months. In this study, we test the hypothesis that BRAF inhibition in combination with adoptive T-cell transfer (ACT) will be more effective at inducing long-term clinical regressions of BRAF-mutant tumors.

EXPERIMENTAL DESIGN

BRAF-mutated human melanoma tumor cell lines transduced to express gp100 and H-2D(b) to allow recognition by gp100-specific pmel-1 T cells were used as xenograft models to assess melanocyte differentiation antigen-independent enhancement of immune responses by BRAF inhibitor PLX4720. Luciferase-expressing pmel-1 T cells were generated to monitor T-cell migration in vivo. The expression of VEGF was determined by ELISA, protein array, and immunohistochemistry. Importantly, VEGF expression after BRAF inhibition was tested in a set of patient samples.

RESULTS

We found that administration of PLX4720 significantly increased tumor infiltration of adoptively transferred T cells in vivo and enhanced the antitumor activity of ACT. This increased T-cell infiltration was primarily mediated by the ability of PLX4720 to inhibit melanoma tumor cell production of VEGF by reducing the binding of c-myc to the VEGF promoter. Furthermore, analysis of human melanoma patient tumor biopsies before and during BRAF inhibitor treatment showed downregulation of VEGF consistent with the preclinical murine model.

CONCLUSION

These findings provide a strong rationale to evaluate the potential clinical application of combining BRAF inhibition with T-cell-based immunotherapy for the treatment of patients with melanoma.

G-CSF-activated STAT3 enhances production of the chemokine MIP-2 in bone marrow neutrophils

Neutrophil mobilization from the bone marrow is a critical aspect of the innate immune response, enabling a rapid deployment of phagocytes to infected or inflamed tissue. The cytokine G-CSF, which is induced rapidly during infection, elicits a swift and potent mobilizing response, yet its mechanisms of action remain poorly understood. Here, we studied the role of G-CSF and its principal signal transducer STAT3 in regulating expression of the neutrophil chemoattractant MIP-2. Our studies revealed Gr-1(hi) mature neutrophils as major sources of Cxcl2 (MIP-2) mRNA in bone marrow and G-CSF-responsive MIP-2 protein production. Induction of Cxcl2 was regulated directly by G-CSF-activated STAT3 via interaction at a STAT consensus element in the Cxcl2 promoter. G-CSF coordinately stimulated the association of STAT3, induction of the transcriptionally active H3K4me3 modification, and recruitment of RNA Pol II at the Cxcl2 proximal promoter, as well as the promoter region of Il8rb, encoding the MIP-2 receptor. These results suggest that the G-CSF-STAT3 pathway directly regulates transcriptional events that induce neutrophil mobilization.

Single nucleotide polymorphisms in NOS2A and NOS3 genes are not associated with treatment response of non-small cell lung cancer patients following the definitive radiochemotherapy

Nitric oxide (NO), is endogenously synthesized from L-arginine by nitric oxide synthase (NOS), exhibits a dual role in sensitivity to radiotherapy and chemotherapy of cancer cells. The aim of this study was to evaluate the influence of polymorphisms in NOS genes on treatment response of non-small-cell lung cancer (NSCLC) patients after radiochemotherapy. A cohort of 198 NSCLC patients treated with radiochemotherapy between 2009 and 2011 were included in this study. Genotyping analyses of 35 SNPs ( NOS2A, 21 and NOS3, 14) in each sample were conducted by using the Sequenom MassArray system. Unconditional logistic regression was performed to assess the association between treatment response and each genotype while adjusting or not for other covariates. Of 198 patients, 87 (43.9%) had objective responses, and 111(56.1%) did not respond. We observed no significant associations between treatment response and each genotype. While adjusting for other covariates, the associations were also not significant. Our results suggest that genetic variations within the NOS2A and NOS3 genes may not influence the treatment response in NSCLC patients with radiochemotherapy. Future studies in this problem are required to confirm our findings.

A STATus report on DC development

DCs have a vital role in the immune system by recognizing exogenous or self-antigens and eliciting appropriate stimulatory or tolerogenic adaptive immune responses. DCs also contribute to human autoimmune disease and, when depleted, to immunodeficiency. Moreover, DCs are being explored for potential use in clinical therapies including cancer treatment. Thus, understanding the molecular mechanisms that regulate DCs is crucial to improving treatments for human immune disease and cancer. DCs constitute a heterogeneous population including plasmacytoid (pDC) and classic (cDC) subsets; however, the majority of DCs residing in lymphoid organs and peripheral tissues in steady state share common progenitor populations, originating with hematopoietic stem cells. Like other hematopoietic lineages, DCs require extracellular factors including cytokines, as well as intrinsic transcription factors, to control lineage specification, commitment, and maturation. Here, we review recent findings on the roles for cytokines and cytokine-activated STAT transcription factors in DC subset development. We also discuss how cytokines and STATs intersect with lineage-regulatory transcription factors and how insight into the molecular basis of human disease has revealed transcriptional regulators of DCs. Whereas this is an emerging area with much work remaining, we anticipate that knowledge gained by delineating cytokine and transcription factor mechanisms will enable a better understanding of DC subset diversity, and the potential to manipulate these important immune cells for human benefit.

Abstract 5396: Interferon-α receptor dependent and independent inhibition of type I interferon production in plasmacytoid dendritic cells from mice and melanoma patients

IFN-α is pleiotropic cytokine belonging to the type I Interferon (IFNs) family and can induce multiple biological effects, e.g. induction of apoptosis and inhibition of cell growth. These cytokines exhibit a long record of clinical use in patients with some types of cancer and viral diseases. Notably, certain autoimmune disorders have been postulated to be mediated by endogenous IFN-α and are often observed in some IFN-α-treated cancer patients. How IFN-α promotes the generation of antitumor T-cell immunity and its regulation mechanisms are still unclear. To address these questions, we focus on the main producer of IFNs, Plasmacytoid dendritic cells (pDCs), which reside in bone marrow and lymphoid organs and typically secrete type I IFNs on Toll-like receptor (TLR) triggering. We detected cytokines production by human pDCs from leukapheresis cells of melanoma patients who were treated with IFNs for 25 weeks. After stimulation with CpG-A, these pDCs after treatment (IFN-α-pDCs) produce 70% less IFN-α compare to before treatment, but compatible amount of other inflammatory cytokines e.g. IL-6. We observed the similar phenomena in murine models either after VSV infection or by systemic IFN-α delivery. We showed that these IFN-α-pDCs possess more active and mature morphology as DCs and they are particularly more effective in inducing T- and NK-cell immunity by increasing cell proliferation and differentiation. Of note, IFN-α-pDCs skewed the naïve CD4+ T cells to a Th17 antigen-presenting subset by producing more IL-17 but less IFN-γ compare to wide type pDCs. The ensemble of these results suggests that IFN-α-pDCs could be successfully used in strategies of cancer immunotherapy, especially in melanoma patients. We also demonstrate that pDCs possess two fundamental, but separate, physiologic mechanisms for negative feedback control of IFN-α production after IFNs treatment in melanoma patients. Both signaling through the canonical TLR-MyD88 pathway and feedback inhibition from IFN-α itself through the IFN-α/βR render pDCs unable to synthesize type I interferon upon TLR triggering. Mechanistically, we found that IFN-α-pDCs show increased IRF7 mRNA and protein upon TLR stimulation, but despite efficient nuclear IRF-7 translocation, type I IFN was not produced. Interestingly, Ifn-α6 promoter activity was blocked in the IFN-α-pDCs, suggesting a block of type I IFN transcription despite nuclear IRF-7 translocation. Taken together, triggering of TLR and of IFN-α/βR act independently to tightly limit systemic IFN-α production after IFNs treatment. All this reveals the complexity of the IFN-α-pDC interactions under normal and pathological conditions and stimulates further studies for identifying optimal modalities in either using these cytokines or controlling their production in melanoma patients.

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 5396. doi:1538-7445.AM2012-5396

STAT5 protein negatively regulates T follicular helper (Tfh) cell generation and function

Recent work has identified a new subset of CD4(+) T cells named as Tfh cells that are localized in germinal centers and critical in germinal center formation. Tfh cell differentiation is regulated by IL-6 and IL-21, possibly via STAT3 factor, and B cell lymphoma 6 (Bcl6) is specifically expressed in Tfh cells and required for their lineage specification. In the current study, we characterized the role of STAT5 in Tfh cell development. We found that a constitutively active form of STAT5 effectively inhibited Tfh differentiation by suppressing the expression of Tfh-associated factors (CXC motif) receptor 5 (CXCR5), musculoaponeurotic fibrosarcoma (c-Maf), Bcl6, basic leucine zipper transcription factor ATF-like (Batf), and IL-21, and STAT5 deficiency greatly enhanced Tfh gene expression. Importantly, STAT5 regulated the expression of Tfh cell suppressor factor B lymphocyte-induced maturation protein 1 (Blimp-1); STAT5 deficiency impaired Blimp-1 expression and resulted in elevated expression of Tfh-specific genes. Similarly, inhibition of IL-2 potentiated Tfh generation, associated with dampened Blimp-1 expression; Blimp-1 overexpression inhibited Tfh gene expression in Stat5-deficient T cells, suggesting that the IL-2/STAT5 axis functions to regulate Blimp-1 expression. In vivo, deletion of STAT5 in CD4(+) T cells resulted in enhanced development of Tfh cells and germinal center B cells and led to an impairment of B cell tolerance in a well defined mouse tolerance model. Taken together, this study demonstrates that STAT5 controls Tfh differentiation.

Alterations in the mortality and growth cycle of cervical cancer cells treated with electroporation at different electric strengths

OBJECTIVE

To explore the biological effects of electric fields of various strengths on Hela cells.

METHODS

Electroporation experiments were performed using Hela cells. Changes in cell mortality, cell vitality, cell cycle, and apoptosis status were examined. In addition, temperature changes in the surrounding tissue were measured.

RESULTS

Cell proliferation was markedly inhibited after treatment with field strengths of 2-2.5 kV/cm. The expression of caspase-3 increased significantly in cells treated with field strengths of 1.5-2.5 kV/cm. Field strengths of 1.75-2.5 kV/cm produced complete cancer cell ablation. G2 phase frequency increased significantly after treatment with field strengths of 2-2.5 kV/cm. During this process, the maximum temperature increase in the pulsed electric field was 4.9 -/+ 1.17 degrees C under free air convection.

CONCLUSIONS

IRE can be used alone for the treatment of cancer, and its thermal effect is negligible. Cell death was caused by the effects of IRE and apoptosis. The tumor cells must be destroyed completely, or the altered cell cycle may lead to tumor recurrence and accelerated growth.