VAT-associated ST2+Tregs from omentum support tolerance to peripheral tumors

Tumor metastasis to theomentum is associated with poor clinical outcomes. Although the omentum hasimmune function due to the activities of milky spots, the role of this organ inanti-tumor immunity has not been completely described.

By implanting tumor cells in mice we found that peritoneal tumors are not rejected and cause an increasein visceral adipose tissue (VAT)-associated regulatory T cells in the omentumas well as low frequency of tumor specific CD8 T cells. Additionally, peritoneal tumors impaired the immunity to secondary dermal tumors by limiting the expansion of tumor specific CD8 T cells that mediate tumor rejection.

To better understand this phenomenon, we studied the VAT-associated Tregs, which can be divided in ST2+ and ST2- (ST2 a component of the IL-33R). Particularly, VAT-associated ST2+ Tregs are not found in conventional lymphoid organs, nonetheless we find that following peritoneal tumor inoculation ST2+ Tregs are mobilized and home to secondary dermal tumors. To test whether the ST2+ Tregs were responsible for preventing secondary dermal tumors, we inoculate mice lacking ST2 (ST2−/−) with peritoneal tumors and challenged them with dermal tumors; interestingly, we found that secondary dermal tumors where rejected in ST2−/− mice whereas tumors in wild type mice continue to grow. Finally, to corroborate our findings we used a mouse strain that develops spontaneous ovarian tumors that metastasize to the omentum. By treating these mice with anti-ST2 we observed a reduction in tumor weight, decrease in ST2+Tregs and an increase in tumor specific CD8+ cells in omentum and ovaries. Together these data suggest that omental ST2+ Tregs have an important role promoting and maintaining tolerance in tumor metastasis.

Identification of antigen-specific, lung resident memory B cells after influenza infection

B cells display phenotypic and functional heterogeneity in multiple anatomical locations following vaccination or infection. Influenza-specific memory B cells (Flu+BMEM cells) are found in both lymphoid tissues and lung. It is unclear whether these cells represent circulating or resident memory B cell (BRM) populations. We hypothesized that a portion of the Flu+BMEM cell population in the lung would be non-circulating, BRMs. To determine whether Flu+BMEM cells in the lung are circulating or resident, we parabiotically joined previously-infected, congenically-mismatched mice for 2 weeks and marked those cells currently in circulation by infusing anti-B220 and identified those that have trafficked between the partners by their expression of the CD45 congenic marker. The lungs of these mice had large populations of hemagglutinin and nucleoprotein -specific BMEM cells that did not attain equilibrium within 2 weeks of parabiosis, suggesting that they are non-circulating. The Flu+ BRMs in the lungs consisted of 56% IgM+ and 43.9% isotype-switched BRMs. They were established as early as 15 days after infection and maintained for at least 60 days. The formation of Flu+ BRMs required the germinal center (GC), as blocking CD40L with MR1 antibody, during the primary infection abrogated BRM. However, MR1-treatment of mice with established BRM did not affect BRMs in the lung, even though Flu+ GC B cells could be detected in the LN for up to 90 days. These data suggest that GC-dependent lung-BRMs are established early after infection and maintained independently of GCs. These findings are important in the development of vaccines that elicit BRMs and they will provide mechanistic information into the function of Ag+BMEM cells residing in the mucosa.

Abstract POSTER-BIOL-1337: Omentum promotes suppression against peritoneal tumors

Purpose: The metastasis of ovarian cancer to the omentum is associated with poor clinical outcomes. Although the omentum has immune function due to the activities of milky spots, the role of the omentum in anti-tumor immunity has not been rigorously addressed. We hypothesize that the omentum directly modulates anti-tumor immunity to metastasized tumor cells.

Experimental procedure: We examined metastases and immunological function in mice that expresses SV40 T antigen oncogene under the Mullerian Inhibitory Substance type II Receptor promoter (MISIIR-Tag). In separate experiments we also implanted 3 x 106 EG7.1.15 cells (murine thymoma that express chicken ovalbumin (OVA)) intraperitoneally (i.p.) to induce peritoneal tumors. We used flow cytometry to analyze cells from the omentum and peritoneal exudate from mice with or without tumors.

Results: Omental tumor growth induced by EG7.1.15 cells is associated with an increase in CD4+CD25+FoxP3+ T regulatory cells (Tregs) and CD103+ DCs, while tumor-specific CD8+ T cells are reduced. Although tumor-specific CD8+ T cells generated in the periphery prior to tumor onset prevent omental and peritoneal tumor growth, tumor-specific CD8+ T cells generated after tumors are established in the omentum are unable to mediate tumor clearance. The induction of tolerance requires the omentum, is dependent on FoxP3+ Tregs, is tumor antigen-specific and takes place in as few as 6 days. The metastasis of ovarian tumor cells into the omentum also correlates with an increase in Tregs. Deleting Tregs in both models reduces tumor burden.

Conclusions: Metastasis of tumor cells to the omentum leads to immunological tolerance rather than immunity – even when tumor cells express foreign antigens. Thus, the omentum has an immunological activity that prevents, rather than promotes, immunity to peritoneal tumors.

Citation Format: Selene Meza-Perez, Maria de la Luz Garcia-Hernandez, Aaron Silva-Sanchez, Javier Rangel-Moreno, Uma Mudunuru, Edith M Lord PhD, Troy D. Randall. Omentum promotes suppression against peritoneal tumors [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr POSTER-BIOL-1337.

Intestinal microbiota alters omental tumor growth (TUM9P.1004)

The omentum is an adipose tissue that contains milky spots (MS). The MS are similar to secondary lymphoid organs and can generate B and T cell immune responses to peritoneal antigens. Additionally, omentum CD4+CD25+FoxP3+ T regulatory cells (Tregs) display an activated phenotype CD44hiCD62Llow. Moreover, the omentum also collects metastasizing tumor cells in the peritoneal cavity and tumors growing in the omentum are associated with poor clinical prognosis. Here we show that intestinal microbiota affects Tregs activation profile and impairs tumor growth in omentum. Our transplantable tumor model in wild type (WT) mice shows that peritoneal tumors grow progressively in the omentum and peritoneal cavity in WT mice, whereas in germ free (GF) mice tumors do not grow. Omental tumor growth in WT mice is associated with an increase in PD-1+ Tregs, while tumor-specific CD8+ T are reduced. However, in GF mice numbers of PD1+ Tregs remain unaltered but tumor specific CD8+ T cells are still present. After co-housed GF mice with WT mice, ex-GF mice showed tumor growth and restore the increase in PD-1+ Tregs with low number of specific CD8+ T cells. The induction of tolerance requires PD-1+ Tregs. These data suggest that intestinal microbiota has a role in omental Tr activation and in the tolerance to peritoneal tumors.

Deficiency in transient receptor potential melastatin 2 impairs alveolar macrophage activation and protects mice against endotoxin-induced lung inflammation and injury (INC5P.333)

Cellular responses to reactive oxygen species (ROS) are induced by many receptors including the non-selective cation channel TRPM2 that promotes cation influx and membrane depolarization following ROS exposure, and potentiates inflammatory cytokine production and cell death. Conflicting reports on the harmful vs. protective roles of TRPM2 in ROS-mediated disease models led us to test whether TRPM2 is required for protection against lung endotoxin exposure, one of the most common etiologies of Acute Lung Injury (ALI). We found that Trpm2-/- mice exposed to intranasal lipopolysaccharide (LPS) were protected from lung inflammation and injury and that protection was due to loss of TRPM2 in radiation-resistant lung cells. Next, we examined the role of TRPM2 in radiation-resistant alveolar macrophages (AMs) as these cells are known contributors of ROS in ALI. Using congenic mice harboring the CD45.1/CD45.2 allelic variants we generated bone marrow chimeras in which radiation-resistant host and donor-derived AMs could be distinguished. We observed increased resistance to cell death in host Trpm2-/- AMs. Furthermore, LPS-activated Trpm2-/- AMs showed decreased expression of iNOS, inflammatory cytokines and proteases. Macrophage depletion experiments are underway to investigate the protective role of Trpm2-/- AMs in vivo. Our data support a harmful role of TRPM2 in ALI, and attribute the protective phenotype of Trpm2-/- mice to impaired macrophage-mediated lung inflammatory responses.

Transient receptor potential melastatin 2 is a critical mediator of lipopolysaccharide-induced pulmonary inflammation and injury (P5076)

Lipopolysaccharide (LPS)-induced production of Reactive Oxygen Species (ROS) leads to lung inflammation and damage associated with several respiratory diseases, including Acute Respiratory Distress Syndrome (ARDS). The link between oxidative stress and inflammation in ARDS led us to hypothesize that the non-selective, redox-sensitive TRPM2 cation channel contributes to the pathogenesis of this syndrome. Following intranasal LPS challenge, Trpm2-/- mice had attenuated alveolar hemorrhage compared to wild-type mice. Flow cytometric analyses showed a modest increase in PMNs and alveolar macrophages (AMs) in the lung tissue and airways of Trpm2-/- mice at the early phase (3-12 hours) of inflammation but significant reductions in PMNs, monocytes, monocyte-derived cells and lymphocytes at the mid (1-2 days) and late (3-7 days) phases. Furthermore, Trpm2-/- mice had decreased expression of proinflammatory/chemoattractant factors and matrix metalloproteases in the lung. Irradiated bone marrow chimeric mice revealed that the protective, TRPM2-deficient phenotype is mainly due to defects in irradiation-resistant lung cells, suggesting that TRPM2 may play an important role in non-hematopoietic cells (e.g. pulmonary endothelial and epithelial cells), as well as AMs. Our data support a harmful role for TRPM2 in ARDS and highlight its pharmacological inhibition as a potential therapeutic approach in treating acute pulmonary inflammation and injury in patients with bacterial infections.

Superior efficacy of a combined epigenetic therapy against human mantle cell lymphoma cells

PURPOSE

A deregulated epigenome contributes to the transformed phenotype of mantle cell lymphoma (MCL). This involves activity of the polycomb repressive complex (PRC) 2, containing three core proteins, EZH2, SUZ12, and EED, in which the SET domain of EZH2 mediates the histone methyltransferase activity. We determined the effects of 3-deazaneplanocin A (DZNep), an S-adenosylhomocysteine hydrolase inhibitor, and/or pan-histone deacetylase inhibitor panobinostat (PS) on cultured and primary MCL cells.

EXPERIMENTAL DESIGN

Following treatment with DZNep and/or PS, apoptosis and the levels and activity of EZH2 and PRC2 proteins in cultured and primary MCL cells were determined.

RESULTS

Treatment with DZNep depleted EZH2, SUZ12, and 3MeK27H3 in the cultured human MCL cells. DZNep also increased expression of p21, p27, and FBXO32, whereas it depleted Cyclin D1 and Cyclin E1 levels in MCL cells. In addition, DZNep treatment induced cell-cycle arrest and apoptosis in cultured and primary MCL cells. Furthermore, as compared with treatment with each agent alone, cotreatment with DZNep and PS caused greater depletion of EZH2, SUZ12, 3MeK27H3, and Cyclin D1 levels, whereas it induced greater expression of FBXO32, p16, p21, and p27. Combined treatment with DZNep and PS synergistically induced apoptosis of cultured and primary MCL cells while relatively sparing normal CD34 + cells. Cotreatment with DZNep and PS also caused significantly greater inhibition of tumor growth of JeKo-1 xenografts in NOD/SCID mice.

CONCLUSIONS

These preclinical in vitro and in vivo findings show that cotreatment with DZNep and PS is an active combined epigenetic therapy worthy of further in vivo testing against MCL.

Anti-AML activity of a novel beta-catenin antagonist BC2059

10605

Background: The canonical WNT-β-catenin pathway is essential for self-renewal, growth and survivalof AML stem and progenitor cells. Deregulated WNT signaling inhibits degradation of β-catenin, causing increased nuclear translocation and interaction of β-catenin with the TCF/LEF transcription factor, which up regulates cyclin D1, Myc and survivin expression in AML progenitor cells. BC2059 (β-Cat Pharmaceuticals) is a potent, small molecule, anthraquinone oxime-analog, which inhibits WNT-β catenin pathway by promoting the degradation and attenuation of β-catenin levels. Methods: We determined the in vitro anti-AML activity of BC2059 (BC) (250 to 1000 nM) against cultured and primary human AML blast progenitors, as well as evaluated the in vivo anti-AML efficacy of BC in NOD-SCID and NOD-SCID-IL2γ receptor deficient (NSG) mice. Results: BC induced cell cycle G1 phase accumulation and apoptosis (40%) of the cultured OCI-AML3, HL-60 and HEL92.1.7 (HEL) AML cells. BC dose-dependently also induced apoptosis of primary AML versus normal progenitors. Treatment with BC resulted in proteasomal degradation and decline in the nuclear levels of β-catenin, which led to decreased activity of the LEF1/TCF4 transcription factor highlighted by reduced TOP-FLASH luciferase activity in the AML cells. This was associated with reduced protein levels of cyclin D1, MYC and survivin. Co-treatment with BC and the histone deacetylase inhibitor panobinostat (PS) (10 to 20 nM) synergistically induced apoptosis of cultured and primary AML blasts. Following tail vein infusion and establishment of AML by OCI-AML3 or HEL cells in NOD-SCID mice, treatment with BC (5, 10 or 15 mg/kg b.i.w, IV) for three weeks demonstrated improved survival, as compared to the control mice (p <0. 001). Survival was further improved upon co-treatment with BC and PS (5 mg/kg IP, MWF). BC treatment (5 or 10 mg/kg IV) also dramatically improved survival of NSG mice with established human AML following tail-vein injection of primary AML blasts expressing FLT3 ITD. Mice did not experience any toxicity or weight loss. Conclusions: These findings highlight the notable pre-clinical in vitro and in vivo activity and warrant further development and in vivo testing of BC against human AML.

Combination of pan-histone deacetylase inhibitor and autophagy inhibitor exerts superior efficacy against triple-negative human breast cancer cells

Histone deacetylase (HDAC) inhibitors (HDI) induce endoplasmic reticulum (ER) stress and apoptosis, while promoting autophagy, which promotes cancer cell survival when apoptosis is compromised. Here, we determined the in vitro and in vivo activity of the combination of the pan-HDI panobinostat and the autophagy inhibitor chloroquine against human estrogen/progesterone receptor and HER2 (triple)-negative breast cancer (TNBC) cells. Treatment of MB-231 and SUM159PT cells with panobinostat disrupted the hsp90/histone deacetylase 6/HSF1/p97 complex, resulting in the upregulation of hsp. This was accompanied by the induction of enhanced autophagic flux as evidenced by increased expression of LC3B-II and the degradation of the autophagic substrate p62. Treatment with panobinostat also induced the accumulation and colocalization of p62 with LC3B-II in cytosolic foci as evidenced by immunofluorescent confocal microscopy. Inhibition of panobinostat-induced autophagic flux by chloroquine markedly induced the accumulation of polyubiquitylated proteins and p62, caused synergistic cell death of MB-231 and SUM159PT cells, and inhibited mammosphere formation in MB-231 cells, compared with treatment with each agent alone. Finally, in mouse mammary fat pad xenografts of MB-231 cells, a tumor size-dependent induction of heat shock response, ER stress and autophagy were observed. Cotreatment with panobinostat and chloroquine resulted in reduced tumor burden and increased the survival of MB-231 breast cancer xenografts. Collectively, our findings show that cotreatment with an autophagy inhibitor and pan-HDI, for example, chloroquine and panobinostat results in accumulation of toxic polyubiquitylated proteins, exerts superior inhibitory effects on TNBC cell growth, and increases the survival of TNBC xenografts.

Heat shock protein 90 inhibition depletes TrkA levels and signaling in human acute leukemia cells

Nerve growth factor (NGF) induces autophosphorylation and downstream progrowth and prosurvival signaling from the receptor tyrosine kinase TrkA. Overexpression or activating mutation of TrkA has been described in human acute myeloid leukemia cells. In the present study, we show the chaperone association of TrkA with heat shock protein 90 (hsp90) and the inhibitory effect of the hsp90 inhibitor, 17-DMAG, on TrkA levels and signaling in cultured and primary myeloid leukemia cells. Treatment with 17-DMAG disrupted the binding of TrkA with hsp90 and the cochaperone cdc37, resulting in polyubiquitylation, proteasomal degradation, and depletion of TrkA. Exposure to 17-DMAG inhibited NGF-induced p-TrkA, p-AKT, and p-ERK1/2 levels, as well as induced apoptosis of K562, 32D cells with ectopic expression of wild-type TrkA or the constitutively active mutant Delta TrkA, and of primary myeloid leukemia cells. Additionally, 17-DMAG treatment inhibited NGF-induced neurite formation in the rat pheochromocytoma PC-12 cells. Cotreatment with 17-DMAG and K-252a, an inhibitor of TrkA-mediated signaling, induced synergistic loss of viability of cultured and primary myeloid leukemia cells. These findings show that TrkA is an hsp90 client protein, and inhibition of hsp90 depletes TrkA and its progrowth and prosurvival signaling in myeloid leukemia cells. These findings also support further evaluation of the combined activity of an hsp90 inhibitor and TrkA antagonist against myeloid leukemia cells.

Abstract C196: Co-treatment with NVP-BEZ235 and heat shock protein (hsp) 90 or pan-deacetylase (DAC) inhibitor is synergistically active against non-small cell lung cancer (NSCLC) cells with mutant RAS and LKB1

Inactivating somatic mutation of LKB1 is found in approximately 30% of NSCLC and is often coincident with activating K-RAS mutation. In a mutant K-RAS-driven model of mouse lung cancer, strong cooperation and aggressive phenotype was seen with hemizygous inactivation of LKB1. Loss of LKB1 results in activation of mTOR pathway while somatic activating mutation in K-RAS results in activation of PI3K/AKT and RAS/RAF/ERK. Therefore therapeutic stratagies which target these pathways may have significant affect on the outcome of these cancers. NVP-BEZ235 is a dual PI3K and mTOR inhibitor and panobinostat (PS) (Novartis Pharmaceuticals Inc) is a pan-histone deacetylase (HDAC) inhibitor, which has been shown to induce proteasomal degradation and depletion of the levels of hsp90 client proteins, including AKT and c-RAF. Here, we determined the effects of BEZ235 and/or PS or AUY922 (an hsp90 inhibitor) on NSCLC A549 and H460 cells with LKB1 and K-RAS mutations (A549 and H460). Treatment with BEZ235 (200 to 1000 nM), PS (25 to 50 nM) or AUY922 (25 to 100 nM) dose-dependently increased % of cells in G2/M and decreased % of cells in S phase of cell cycle, as well as induced apoptosis of the NSCLC cells. Co-treatment with AUY922 or PS increased BEZ235 mediated depletion of p-AKT, p-4EBP1 and p-p70S6K levels, as well as synergistically induced apoptosis of A549 and H460 cells (combination indices &lt; 1.0). Combined therapy with BEZ235 (25 mg/Kg) and PS (10 mg/Kg) or AUY922 (20 mg/Kg) resulted in significantly more tumor growth delay than treatment with each of the agents alone of A549 cell xenografts in nude mice (p &lt; 05). We also determined the activity of BEZ235 and/or PS in the NSCLC H368 cells with mutant K-RAS and either wild-type (H358 cells) or stable knock down of LKB1 expression (H358/LKB1-KD cells), achieved by shRNA against LKB1, mimicking the presence of mutant LKB1. As compared to each agent alone, co-treatment with BEZ235 and PS exhibited a higher level of antitumor synergy against H358/LKB1-KD versus H358 cells. These pre-clinical in vitro and in vivo studies demonstrate that combined treatment with the dual PI3K/mTOR inhibitor BEZ235 and PS or AUY922 could potentially be a promising targeted therapy for NSCLC that harbors K-ras and LKB1 mutations.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C196.