Tumor-free Mice Research Articles

Dysosma versipellis Extract Inhibits Esophageal Cancer Progression through the Wnt Signaling Pathway.

Objective In this study, we aim to investigate the effect of Dysosma versipellis extract on biological behavior of esophageal cancer cells and its underlying mechanisms. Methods A total of 30 BALB/C nude mice (class SPF) were equally and randomly divided into the control group, model group, and Dysosma versipellis group. CP-C cell of esophageal cancer was subcutaneously injected into the model group as well as the Dysosma versipellis group, and the same amount of normal saline into the control group, in order to compare the tumorigenesis of nude mice of three groups. Wnt, β-catenin, and p-GSK3β/GSK3β expression in tumor tissues was detected using Western blot. CP-C cells in logarithmic growth were selected and divided into 4 groups, including the control group, podophyllotoxin group, Wnt activator group, and combined group (mixture of podophyllotoxin and Wnt activator). The cell viability, apoptosis, and invasion ability, Wnt, β-catenin, and p-GSK3β/GSK3β expression level of CP-C cells in each group were detected via MTT assay, flow cytometry, transwell, and Western blot, respectively. Results The tumorigenesis rates of the control group, model group, and Dysosma versipellis group were 0%, 90% (1 tumor-free mouse), and 80% (2 tumor-free mice), respectively. The tumor mass in the Dysosma versipellis group was significant less than that in the model group. Based on the results of Western blot, Wnt, ß-catenin, and p-GSK3β/GSK3β expression of the Dysosma versipellis group was lower than that of the control group. The in vitro viability test indicated that there was a significant difference in cell viability exhibited among four groups. Cell viability level in the 3 groups, including the combined group, blank group, and Wnt activator group, was higher than the podophyllotoxin group at each time point. In vitro apoptosis assay revealed that significant differences in cell apoptosis exhibited among four groups. Cell apoptosis rate was higher in the podophyllotoxin group compared to the remaining three groups. The Wnt activator group showed the lowest cell apoptosis rate. The in vitro invasion assay demonstrated that numbers of transmembrane cell in the 3 groups, involving the combined group, blank group, and Wnt activator group, showed a higher level than the podophyllotoxin group. The results of Western blot manifested that the podophyllotoxin group showed lower level of Wnt, ß-catenin, and p-GSK3β/GSK3β expression compared to the other 3 groups. Conclusion Podophyllotoxin in Dysosma versipellis has an excellent antiesophageal cancer effect and is able to inhibit cell viability as well as invasion ability and promote apoptosis of esophageal cancer cells by inhibiting the Wnt signaling pathway, which could be potentially used in future clinical treatment of esophageal cancer.

T Cells Promote Metastasis by Regulating Extracellular Matrix Remodeling following Chemotherapy.

Metastasis is the main cause of cancer-related mortality. Despite intense efforts to understand the mechanisms underlying the metastatic process, treatment of metastatic cancer is still challenging. Here we describe a chemotherapy-induced, host-mediated mechanism that promotes remodeling of the extracellular matrix (ECM), ultimately facilitating cancer cell seeding and metastasis. Paclitaxel (PTX) chemotherapy enhanced rapid ECM remodeling and mechanostructural changes in the lungs of tumor-free mice, and the protein expression and activity of the ECM remodeling enzyme lysyl oxidase (LOX) increased in response to PTX. A chimeric mouse model harboring genetic LOX depletion revealed chemotherapy-induced ECM remodeling was mediated by CD8+ T cells expressing LOX. Consistently, adoptive transfer of CD8+ T cells, but not CD4+ T cells or B cells, from PTX-treated mice to naïve immunodeprived mice induced pulmonary ECM remodeling. Lastly, in a clinically relevant metastatic breast carcinoma model, LOX inhibition counteracted the metastasis-promoting, ECM-related effects of PTX. This study highlights the role of immune cells in regulating ECM and metastasis following chemotherapy, suggesting that inhibiting chemotherapy-induced ECM remodeling represents a potential therapeutic strategy for metastatic cancer. SIGNIFICANCE: Chemotherapy induces prometastatic pulmonary ECM remodeling by upregulating LOX in T cells, which can be targeted with LOX inhibitors to suppress metastasis.See related commentary by Kolonin and Woodward, p. 197.

Synergistic effects of exosomal crocin or curcumin compounds and HPV L1-E7 polypeptide vaccine construct on tumor eradication in C57BL/6 mouse model.

Cervical cancer is the most common malignant tumor in females worldwide. Human papillomavirus (HPV) infection is associated with the occurrence of cervical cancer. Thus, developing an effective and low-cost vaccine against HPV infection, especially in developing countries is an important issue. In this study, a novel HPV L1-E7 fusion multiepitope construct designed by immunoinformatics tools was expressed in bacterial system. HEK-293T cells-derived exosomes were generated and characterized to use as a carrier for crocin and curcumin compounds. The exosomes loaded with crocin and curcumin compounds as a chemotherapeutic agent (ExoCrocin and ExoCurcumin) were used along with the L1-E7 polypeptide for evaluation of immunological and anti-tumor effects in C57BL/6 mouse model. In vitro studies showed that ExoCrocin and ExoCurcumin were not cytotoxic at a certain dose, and they could enter tumor cells. In vivo studies indicated that combination of the L1-E7 polypeptide with ExoCrocin or ExoCurcumin could produce a significant level of immunity directed toward Th1 response and CTL activity. These regimens showed the protective and therapeutic effects against tumor cells (the percentage of tumor-free mice: ~100%). In addition, both ExoCrocin and ExoCurcumin represented similar immunological and anti-tumor effects. Generally, the use of exosomal crocin or curcumin forms along with the L1-E7 polypeptide could significantly induce T-cell immune responses and eradicate tumor cells.

Paclitaxel chemotherapy disrupts behavioral and molecular circadian clocks in mice

Cancer patients experience circadian rhythm disruptions in activity cycles and cortisol release that correlate with poor quality of life and decreased long-term survival rates. However, the extent to which chemotherapy contributes to altered circadian rhythms is poorly understood. In the present study, we examined the extent to which paclitaxel, a common chemotherapy drug, altered entrained and free-running circadian rhythms in wheel running behavior, circulating corticosterone, and circadian clock gene expression in the brain and adrenal glands of tumor-free mice. Paclitaxel injections delayed voluntary wheel running activity onset in a light–dark cycle (LD) and lengthened the free-running period of locomotion in constant darkness (DD), indicating an effect on inherent suprachiasmatic nucleus (SCN) pacemaker activity. Paclitaxel attenuated clock gene rhythms in multiple brain regions in LD and DD. Furthermore, paclitaxel disrupted circulating corticosterone rhythms in DD by elevating its levels across a 24-hour cycle, which correlated with blunted amplitudes of Arntl, Nr1d1, Per1, and Star rhythms in the adrenal glands. Paclitaxel also shortened SCN slice rhythms, increased the amplitude of adrenal gland oscillations in PER2::luciferase cultures, and increased the concentration of pro-inflammatory cytokines and chemokines released from the SCN. These findings indicate that paclitaxel disrupts clock genes and behavior driven by the SCN, other brain regions, and adrenal glands, which were associated with chemotherapy-induced inflammation. Together, this preclinical work demonstrates that chemotherapy disrupts both central and peripheral circadian rhythms and supports the possibility that targeted circadian realignment therapies may be a novel and non-invasive way to improve patient outcomes after chemotherapy.

Estrogen markedly reduces circulating low-density neutrophils and enhances pro-tumoral gene expression in neutrophil of tumour-bearing mice

BackgroundNeutrophils are important for immune surveillance of tumour cells. Neutrophils may also be epigenetically programmed in the tumour microenvironment to promote tumour progression. In addition to the commonly known high-density neutrophils (HDN) based on their separation on density gradient, recent studies have reported the presence of high levels of low-density neutrophils (LDN) in tumour-bearing mice and cancer patients. We reported previously that estrogen promotes the growth of estrogen receptor α-negative mammary tumours in mice undergoing mammary involution through stimulating pro-tumoral activities of neutrophils in the mammary tissue.MethodsFemale BALB/cAnNTac mice at 7–8 weeks old were mated and bilateral ovariectomy was performed 2 days post-partum. At 24 h after forced-weaning of pups to induce mammary involution, post-partum female mice were injected with either E2V, or vehicle control on alternative days for 2-weeks. On 48 h post-weaning, treated female mice were inoculated subcutaneously with 4 T1-Luc2 cells into the 9th abdominal mammary gland. Age-matched nulliparous female was treated similarly. Animals were euthanized on day 14 post-tumour inoculation for analysis. To evaluate the short-term effect of estrogen, post-partum females were treated with only one dose of E2V on day 12 post-tumour inoculation.ResultsEstrogen treatment for 2-weeks reduces the number of blood LDN by more than 10-fold in tumour-bearing nulliparous and involuting mice, whilst it had no significant effect on blood HDN. The effect on tumour-bearing mice is associated with reduced number of mitotic neutrophils in the bone marrow and increased apoptosis in blood neutrophils. Since estrogen enhanced tumour growth in involuting mice, but not in nulliparous mice, we assessed the effect of estrogen on the gene expression associated with pro-tumoral activities of neutrophils. Whilst 48 h treatment with estrogen had no effect, 2-weeks treatment significantly increased the expression of Arg1, Il1b and Tgfb1 in both HDN and LDN of involuting mice. In contrast, estrogen increased the expression of Arg1 and Ccl5 in HDN and LDN of nulliparous mice.ConclusionsProlonged estrogenic stimulation in tumour-bearing mice markedly hampered tumour-associated increase of LDN plausibly by inhibiting their output from the bone marrow and by shortening their life span. Estrogen also alters the gene expression in neutrophils that is not seen in tumour-free mice. The results imply that estrogen may significantly influence the tumour-modulating activity of blood neutrophils.

Caspase-cleavable peptide-doxorubicin conjugate in combination with CD47-antagonizing nanocage therapeutics for immune-mediated elimination of colorectal cancer

Here we report a novel combination of a caspase-cleavable peptide-doxorubicin conjugate (MPD-1) with CD47-antagonizing nanocage therapeutics for the treatment of microsatellite-stable (MSS) colorectal cancer (CRC). MPD-1 (i) upregulated markers of immunogenic cell death (ICD) in tumor, and increased co-stimulatory markers on dendritic cells (DCs), (ii) enhanced CD8+ T cell infiltration and antigen presenting cell (APC) activation, and (iii) showed negligible off-target immune-related toxicity compared to free dox. Then, the CD47 antagonist FS nanocage, a SIRPα-expressing ferritin nanocage, was co-administered with MPD-1 that resulted in 95.2% (p < 0.001) tumor growth inhibition in an established CRC model. T cell-mediated elimination of tumors was also confirmed by the tumor-specific activation of T cells detected by IFNγ and tumor-free mice were observed (95%) that bared a memory response when re-challenged. The strategically developed MPD-1 is an ideal adjuvant to immunotherapy and the combination with FS nanocage triggers potent immunity against MSS CRC. In summary, we present an approach to initiate and stimulate immune-mediated eradication of cancer cells using synergistic immunogenic agents targeting the MSS CRC.

Doxorubicin Paradoxically Ameliorates Tumor-Induced Inflammation in Young Mice.

Doxorubicin (DOX) is one of the most widely used chemo-therapeutic agents in pediatric oncology. DOX elicits an inflammatory response in multiple organs, which contributes to DOX-induced adverse effects. Cancer itself causes inflammation leading to multiple pathologic conditions. The current study investigated the inflammatory response to DOX and tumors using an EL4-lymphoma, immunocompetent, juvenile mouse model. Four-week old male C57BL/6N mice were injected subcutaneously with EL4 lymphoma cells (5 × 104 cells/mouse) in the flank region, while tumor-free mice were injected with vehicle. Three days following tumor implantation, both tumor-free and tumor-bearing mice were injected intraperitoneally with either DOX (4 mg/kg/week) or saline for 3 weeks. One week after the last DOX injection, the mice were euthanized and the hearts, livers, kidneys, and serum were harvested. Gene expression and serum concentration of inflammatory markers were quantified using real-time PCR and ELISA, respectively. DOX treatment significantly suppressed tumor growth in tumor-bearing mice and caused significant cardiac atrophy in tumor-free and tumor-bearing mice. EL4 tumors elicited a strong inflammatory response in the heart, liver, and kidney. Strikingly, DOX treatment ameliorated tumor-induced inflammation paradoxical to the effect of DOX in tumor-free mice, demonstrating a widely divergent effect of DOX treatment in tumor-free versus tumor-bearing mice.

Abstract 514: Specific anti-HER2 host immunity conferred by HER2-targeted antibody drug conjugate therapy and checkpoint blockade

Abstract Using HER2-targeted antibody drug conjugates (ADC), we tested the therapeutic efficacy, direct impact on cancer stem cells (CSCs), and potential added benefit when combined with PD-L1 blockade in immunocompetent mouse tumor models. Two murine mammary tumor models were used in this study: D2F2/E2, a cell line resulting from stable transfection of parental D2F2 murine mammary tumor cells with wild-type human HER2, and 4T1-HER2, derived from parental 4T1 by stable transduction with wild-type human HER2. We demonstrate that HER2-targeted ADC treatment induced both cellular and humoral anti-HER2 adaptive immune responses which effectively targeted both bulk tumor and cancer stem cells. We recently investigated induction of host immunity using a tumor re-challenge strategy in tumor free animals subjected to ADC or ADC + anti-PD-L1 therapy. D2F2/E2 tumor-bearing mice were treated with ADC or ADC + anti-PD-L1 to generate tumor free mice. These tumor free animals were re-challenged with the relevant tumor D2F2/E2 or irrelevant tumor WT 4T1 respectively. While all the tumor free animals re-challenged with WT 4T1 showed aggressive tumor growth, ADC-treated tumor free animals re-challenged with D2F2/E2 demonstrated significantly (p&amp;lt;0.0001) slower tumor growth compared with the age-matched naive mice, and this protection was significantly (p=0.0078) enhanced in ADC + anti-PD-L1-treated tumor free animals, resulting in completely rejection of the re-challenge and thus documenting immunological memory formation. B cell activation was obvious by the significant upregulation of Ki67 and GL7 CD86 on both CD45+CD19+ tumor-infiltration lymphocytes (TILs) and splenocytes. B cell differentiation was evident by the upregulation of GL7 on both TILs and splenocytes, as well as the expression of CD138 on splenotytes. We found that IgG1 was the predominant isotype in treated mice vs. IgG2a, IgG2b, IgG3, and ADC + anti-PD-L1 dual treatment drastically increased the amount of IgG1 in serum. In addition, ADC+ anti-PD-L1 dual treatment significantly increased the frequency of CD8+IFNγ+ cells in TILs. Both ADC alone (p=0.0004) and ADC+anti-PD-L1 dual treatment (p=0.01) significantly decreased CD4+FoxP3+ regulatory T cells. These results provide evidence that HER2-targeted ADC + anti-PD-L1 immunotherapy-induced B cell activation and differentiation along with the modulation of T cell subsets could confer host anti-HER2 immunity. Citation Format: You Qin, Hannah E. Dobson, Frank I. Comer, Alfred E. Chang, Max S. Wicha, Qiao Li. Specific anti-HER2 host immunity conferred by HER2-targeted antibody drug conjugate therapy and checkpoint blockade [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 514.

Abstract 1563: DRP-104, a broad acting glutamine antagonist, synergizes with immune checkpoint blockade in vivo

Abstract We previously reported that DRP-104, a novel broad acting glutamine antagonist, has significant therapeutic potential in cancer by directly targeting tumor metabolism and simultaneously inducing a potent antitumor immune response. We also reported the immunomodulatory effect of DRP-104 on tumor growth inhibition (TGI) as a single agent and in combination with PD-1/PD-L1 checkpoint inhibitors in the MC38 and CT26 colon cancer syngeneic models(1). DRP-104 mediated TGI is associated with increased tumor-infiltrating leukocytes (TIL) including T, NKT, and NK cells; M1-polarized tumor associated macrophages; and decreased immune-suppressive cells such as MDSCs.Here we further elucidate the immunomodulatory effect of DRP-104 on tumor growth inhibition. In the MC38 mouse model, CD8+, CD4+, or NK cells were depleted by anti-CD8+Ab, anti-CD4+Ab, or anti-asialoGM1 Ab respectively to assess the contribution of these immune cells towards DRP-104 efficacy. CD8+T cell depletion significantly reduced anti-tumor efficacy for DRP-104 (73.9% TGI in CD8+T depletion setting vs 120% TGI with 57.8% regression in undepleted animals). NK cell depletion delayed early anti-tumor response to DRP-104 treatment, while in undepleted mice DRP-104 treatment showed TGI as early as 2 days after dose initiation. Interestingly, CD4+depleted mice showed enhanced efficacy to DRP-104 with TGI of 213% (regressions) and 6/8 tumor free mice 29 days after the end of treatment vs 1/8 mice tumor free in the CD4+ undepleted group with DRP-104 treatment. As such, we tested the combination of DRP-104 with anti-TIGIT antibody which has been reported to deplete Treg cells in the TME(2). In MC38 (anti-TIGIT insensitive) and CT26 (anti-TIGIT sensitive), DRP-104 showed significant single agent TGI. Furthermore, combination of DRP-104 with anti-TIGIT Ab demonstrated enhanced tumor growth inhibition and resulted in improvement in survival. In summary, immune cell depletion experiments confirmed DRP-104's immuno-oncology mechanism of action. CD8+ or NK cell depletion reduced DRP-104 efficacy while CD4+ cell depletion enhanced efficacy. Furthermore, combination therapy of DRP-104 with anti-PD-1 or anti-TIGIT Ab achieved significantly enhanced anti-tumor efficacy even in checkpoint inhibitor resistant models. This unique and non-overlapping mechanism of action supports clinical development of DRP-104 alone and in combination with immune checkpoint inhibitors. The first in human clinical study of DRP-104 is ongoing.

The Dual PI3K-δ,γ Inhibitor Duvelisib Stimulates Anti-Tumor Immunity and Enhances Efficacy of Immune Checkpoint and Co-Stimulatory Antibodies in a B Cell Lymphoma Model

Duvelisib is an orally active, dual inhibitor of phosphoinositide 3-kinase (PI3K)-δ and PI3K-γ which has shown clinical activity as a monotherapy in chronic lymphocytic leukemia (CLL), small lymphocytic lymphoma (SLL), follicular lymphoma (FL), and T cell lymphoma (O'Brien ASH 2014; Flinn ASH 2014; Horwitz ASH 2014) and is being developed broadly for the treatment of B cell malignancies. Recent publications have demonstrated that PI3K-δ inhibition decreases immunosuppressive regulatory T cells (Tregs) in the tumor microenvironment (Ali, Nature, 2014; Ahmad, Cancer Res 2017) whereas PI3K-γ inhibition decreases immunosuppressive myeloid cells (MDSCs and M2 tumor-associated macrophages) (Kaneda, Nature, 2016; De Henau, Nature, 2016). Accordingly, duvelisib has recently been shown to reduce tumor and spleen MDSCs in a preclinical tumor model (Davis, Cancer Res 2017). These data collectively suggest that reduction of Tregs and immunosuppressive myeloid cells in the tumor microenvironment may contribute to the activity of duvelisib as a monotherapy, and may also augment the efficacy of immune checkpoint or co-stimulatory antibodies.These findings led us to investigate the efficacy of duvelisib (50 mg/kg po, BID) in combination with immune checkpoint (anti-PD-1, RMP1-14) or co-stimulatory (anti-OX40, clone OX86) antibodies. In the murine syngeneic A20 B cell lymphoma model, duvelisib and anti-PD-1 treatments each induced tumor growth delay. When duvelisib and anti-PD-1 were combined in mice bearing pre-existing A20 tumors, strong synergy was observed in the anti-tumor response (see figure). Similarly, duvelisib and anti-OX40 each induced tumor growth delay as single agents in the A20 model. When anti-OX40 and duvelisib were combined, striking tumor regression was observed (see figure). To assess immune memory, tumor-free mice following anti-OX40 alone or anti-OX40 + duvelisib combination were injected with A20 lymphoma cells in the contralateral flank with no further treatment. Whereas the mice that had received anti-OX40 alone grew new tumors upon A20 re-challenge, all tumor-free mice that had received the anti-OX40 + duvelisib combination did not grow A20 tumors upon re-challenge and showed elevated memory T cells in the blood and spleen. These findings demonstrate that the anti-OX40 + duvelisib treatment established immune memory, potentially contributing to the observed tumor regression.These data indicate that duvelisib treatment stimulates anti-tumor immunity. Furthermore, the unique dual inhibition of PI3K-δ and PI3K-γ may make duvelisib especially effective in enhancing the anti-tumor efficacy of immune checkpoint and co-stimulatory antibodies. These data support further exploration of duvelisib in combination with anti-PD-1/PD-L1 or co-stimulatory antibodies in patients with B cell malignancies. [Display omitted] DisclosuresPachter:Verastem, Inc.: Employment. Weaver:Verastem, Inc.: Employment.

PD-1 Mediates Lineage Fate Determination and Function of Myeloid Cells in Response to Tumor-Mediated “Emergency” Myelopoiesis

PD-1 is an inhibitory receptor for which blocking agents have achieved significant success as anti-cancer therapeutics. The mechanism(s) of how PD-1 compromises anti-tumor function and how such effect is reversed by PD-1 blockade remain poorly understood. The rapid change in hematopoietic output that occurs in response to immunologic stress is known as “emergency” myelopoiesis. This process is co-opted by tumors to evade the immune system by inducing potent immunosuppression. Cancer-driven granulo-monocytopoiesis modifies the composition of the hematopoietic output by stimulating the expansion of tumor promoting immature myeloid populations, defined as myeloid-derived suppressor cells (MDSCs), and tumor-associated macrophages (TAMs). Monocytic (M-) and granulocytic (PMN-) MDSCs and TAMs differentiate from granulocyte/macrophage progenitors (GMP) in the bone marrow. We analyzed the myeloid compartment of tumor-bearing mice to determine the expression and function of PD-1 in myeloid cells during cancer-driven emergency myelopoiesis. Using three different mouse tumor models (MC38, B16 and MC17), we determined that PD-1 and its natural ligand PD-L1, were expressed at high levels in all subsets of myeloid cells isolated from the spleen of tumor-bearing mice, including CD11b+Ly6C+ M-MDSC, CD11b+Ly6G+ PMN-MDSC, CD11b+F/480+ macrophages and CD11b+HLA-DR+ dendritic cells (DC). This was in contrast to the significantly lower or undetectable levels of PD-1 expressed in these cellular counterparts isolated from non-tumor bearing mice. High expression of PD-1 and PD-L1 was also identified in these myeloid subsets isolated from the tumor site and at sites of secondary myelopoiesis in the gut. Because these myeloid cell populations differentiate from GMP upon cancer-mediated emergency myelopoiesis, we examined bone marrow myeloid progenitors in tumor bearing and control, non-tumor bearing mice. In non-tumor bearing mice, PD-1 was detected in Lin-/Sca+/Kit+ (LSK) myeloid progenitors, whereas PD-L1 was expressed in Lin-/Sca-/Kit+ (LK), common myeloid progenitors (CMP) and GMP. In tumor-bearing mice, both PD-1 and PD-L1 expression was significantly higher in all myeloid progenitors compared to tumor-free control mice. To determine whether PD-1-mediated signaling in myeloid cells might affect the magnitude and composition of the myeloid output that is altered by cancer-mediated emergency response, we used PD-1 deficient mice. PD-1 ablation, which decreased tumor growth and metastasis, stimulated the differentiation of hematopoietic progenitor cells and resulted in increase of Ly6Chi monocytes and monocyte-derived DC (mo-DC). Abrogation of PD-1 signaling enhanced the maturation of MDSCs by inducing the lineage commitment transcription factors IRF8, IRF4 and RORC1. IRF8 and IRF4 promote monocyte/macrophage and hinder granulocyte differentiation, whereas RORC1 is required for expansion of Ly6Chi monocytes and resolution of inflammation. To examine whether the effects of PD-1 on cancer-mediated emergency myelopoiesis and on myeloid lineage commitment and differentiation were mediated by myeloid cell-intrinsic mechanisms, we generated mice with conditional targeting of the PD-1 gene in the myeloid compartment by crossing PD-1fl/fl with LysM-Cre mice. Myeloid-specific ablation of PD-1 signaling in PD-1fl/fl/LysM-Cre mice impaired tumor growth to a similar extent as global PD-1 ablation in PD1-KO mice and induced a myeloid cell fate switch from MDSCs to effector-like myeloid cells that could be identified in spleen and tumor. Further, abrogation of PD-1 signaling in the myeloid compartment prevented the expansion of tumor-stress associated GMP in PD-1fl/fl/LysM-Cre mice and resulted in increased differentiation of committed monocyte progenitors (CMOP) and monocyte progenitors (MP) in the bone marrow. Moreover, PD-1 deletion significantly diminished NO production by M-MDSC and reversed their ability to suppress antigen-specific T cell responses. Our results reveal a previously unidentified role of the PD-1:PD-L1 pathway in the differentiation of lineage-committed myeloid progenitors during tumor-mediated emergency myelopoiesis to promote MDSCs and suppress effector monocytes and mo-DCs. Switch of myeloid progenitor fate commitment might be a key mechanism by which PD-1 blockade mediates its anti-tumor function. DisclosuresNo relevant conflicts of interest to declare.

Adjuvant properties of IFN-γ and GM-CSF in the scFv6.C4 DNA vaccine against CEA-expressing tumors.

Tumor-associated carcinoembryonic antigen (CEA) is a natural target for vaccines against colorectal cancers. Our previous experience with a DNA vaccine with scFv6.C4, a CEA surrogate, showed a CEA-specific immune response with 40% of tumor-free mice after challenge with B16F10-CEA and 47% with MC38-CEA cells. These percentages increased to 63% after using FrC as an adjuvant. To further enhance the vaccine efficacy, we tested GM-CSF and IFNγ as adjuvants. C57BL/6J-CEA2682 mice were immunized 4 times with uP-PS/scFv6.C4, uP-PS/scFv6.C4 + uP-IFNγ, or uP-PS/scFv6.C4 + uP-GMCSF. After one week, the mice were challenged with MC38-CEA, and tumor growth was monitored over 100 days. Immunization with scFv6.C4 and scFv6.C4 + GM-CSF resulted in a gradual increase in the anti-CEA antibody titer, while scFv6.C4 + IFNγ immunization led to a rapid and sustained increase in the titer. The addition of IFNγ also induced higher CD4 + and CD8 + responses. When challenged, almost80% of the scFv6.C4 + IFNγ-vaccinated mice did not develop tumors, while the others had a significant tumor growth delay. The probability of being tumor-free was 2700% higher using scFv6.C4 + IFNγ than scFv6.C4. The addition of GM-CSF had no additional effect on tumor protection. DNA immunization with scFv6.C4 + IFNγ, but not GM-CSF, increased the antitumor effect via readily sustained specific humoral and cytotoxic responses to CEA.

IL-6 contributes to metastatic switch via the differentiation of monocytic-dendritic progenitors into prometastatic immune cells

BackgroundMetastasis is the major cause of death in patients with cancer. Myeloid skewing of hematopoietic cells is a prominent promoter of metastasis. However, the reservoir of these cells in the...

A novel CXCR4 antagonist counteracts paradoxical generation of cisplatin-induced pro-metastatic niches in lung cancer

Platinum-based chemotherapy remains widely used in advanced non-small cell lung cancer (NSCLC) despite experimental evidence of its potential to induce long-term detrimental effects, including the promotion of pro-metastatic microenvironments. In this study, we investigated the interconnected pathways underlying the promotion of cisplatin-induced metastases.In tumor-free mice, cisplatin treatment resulted in an expansion in the bone marrow of CCR2+CXCR4+Ly6Chigh inflammatory monocytes (IMs) and an increase in lung levels of stromal SDF-1, the CXCR4 ligand. In experimental lung metastasis assays, cisplatin-induced IMs promoted the extravasation of tumor cells and the expansion of CD133+CXCR4+ metastasis-initiating cells (MICs). Peptide R, a novel CXCR4 inhibitor designed as an SDF-1 mimetic peptide, prevented cisplatin-induced IM expansion, the recruitment of IMs into the lungs, and the promotion of metastasis. At the primary tumor site, cisplatin treatment reduced tumor size while simultaneously inducing tumor release of SDF-1, MIC expansion, and recruitment of pro-invasive CXCR4+ macrophages. Co-recruitment of MICs and CCR2+CXCR4+ IMs to distant SDF-1-enriched sites also promoted spontaneous metastases that were prevented by CXCR4 blockade. In clinical specimens from NSCLC patients SDF-1 levels were found to be higher in platinum-treated samples and related to a worse clinical outcome. Our findings reveal that activation of the CXCR4/SDF-1 axis specifically mediates the pro-metastatic effects of cisplatin and suggest CXCR4 blockade as a possible novel combination strategy to control metastatic disease.

Gemcitabine treatment modulates myelopoiesis progenitors and monocytes to promote lung metastasis

Abstract Metastasis-associated macrophages (MAMs) play important roles in tumor metastasis through the formation of a pre-metastatic niche. In mouse models of lung metastasis, interstitial macrophages (IMs) markedly accumulate in the lungs and differentiate into MAMs. Regarding the origin of IMs/MAMs, tissue-resident macrophages and bone marrow (BM)-derived classical monocytes (BM-Mo) contribute to the pool of MAMs. Chemotherapy offers long-term clinical benefits to many cancer patients. However, several pre-clinical studies have demonstrated that certain cytotoxic drugs enhance metastasis by multiple mechanisms. Our recent studies suggest that Gemcitabine (GEM) promotes the immunosuppressive function of monocytic MDSC (M-MDSC) in the tumor microenvironment via the tumor-derived GM-CSF and efferocytosis signaling. In this study, we hypothesize that host responses to GEM treatment enhance the accumulation of BM-derived monocytes in lung, which promotes lung metastasis. Multi-dose of GEM treatment induces the increase of BM LSK cells and multipotent progenitors (MPPs) in tumor-free mice, which is associated with the increase of treatment induce mitochondrial ROS (mtROS). Thus, the percentage of BM Ly6C+ monocytes is significantly increased because of increased progenitor monocyte differentiation potential and monocyte proliferation. Further, GEM treatment increases the percentages of lung CCR2+Ly6C+ monocytes and IMs. Consequently, GEM pre-treated mice have a significantly higher number of pulmonary metastases compared to untreated mice in the experimental metastasis model. These results suggest a novel mechanism for chemotherapy induced metastasis via the modulation of myelopoiesis progenitors.

Analysis of microRNAs in Urinary Exosomes of Tumor‐bearing Mice as a Non‐invasive Tool for Lymphoma Diagnosis

Lymphoma consists of a subgroup of immunological cancers, which arise from malignant B and T lymphocytes. Comprising approximately 4% of cancers in the United States, lymphoma accounts for up to 19,940 deaths per year. Surgical biopsy is the primary method for lymphoma staging and diagnosis. Unfortunately, there are many risks associated with this procedure, including cosmetic disfigurement, seeding of malignant cells into previously unaffected tissue, and expense incurred by patients. Identification of unique cancer-related biomarkers in urinary exosomes may provide a novel non-invasive and cost-effective tool for lymphoma diagnosis. Although analyses of biomarkers obtained from urinary exosomes have been used to evaluate urological cancers, these methods have not yet been translated to non-urological pathologies, such as lymphomas. The objective for this study was to analyze the profile of microRNAs (miRNAs) obtained from urinary exosomes of mice bearing lymphoma tumors and compare it to miRNAs identified in urinary exosomes of tumor free (-) control mice. Male and female C57BL/6 mice were injected with either 2.5x105 mouse EL-4 lymphoma cells [tumor (+) mice, n=6] or phosphate-buffered saline [tumor (-) mice, n=6]. Tumor growth was monitored for up to 20 days with collection of serum, tumor tissues, and organs at the end of this period. Urine was collected for 48 hours beginning on day 17. Extraction of urinary exosomes was followed by total RNA isolation and RT-qPCR using a set of PCR arrays consisting of 709 mouse-specific miRNA primers. Fold changes in miRNA expression were quantified using the ∆∆Ct method. Mice developed tumors by day 13 with initial tumor appearance around day seven. There were no statistically significant differences between final tumor mass, body weights, or food and water intake in tumor (+) versus tumor (-) mice. RT-qPCR arrays of miRNAs extracted from urinary exosomes revealed 464 differentially expressed miRNAs between tumor (+) and tumor (-) mice. Specifically, the expression of two miRNAs, significantly increased in urinary exosomes of tumor (+) mice compared to tumor (-) mice, was also increased in the lymphoma tissue of origin. One miRNA with a significantly decreased expression in the urinary exosomes of tumor (+) mice was found to have a decreased expression in the lymphoma tissue of origin. Expression of miRNAs in mouse tissue was analyzed by RT-qPCR. These results revealed that mice challenged with lymphoma tumors are releasing tumor-specific miRNAs in their urine. These findings are in support of future clinical studies on the use of miRNA analysis in urinary exosomes for non-invasive diagnostics of lymphoma patients.

Therapeutic Vaccine (TheraVac) in combination with cGAMP cures more differentiated melanomas in mice

Abstract We have identified a combination of immunotherapeutics, termed TheraVac, capable of curing multiple large established mouse tumors, but it failed to cure melanoma in mice. TheraVac consists of an immunostimulating arm containing an agonist (HMGN1) for TLR4 and an agonist (R848) for TLR7/8 that synergize to activate tumor-infiltrating dendritic cells (DCs) and upregulate the polarization of Th1 immune responses. The second arm uses an immune checkpoint blockade inhibitor, αPDL-1, to diminish tumor associated immunosuppression. Here, we investigated supplementation of TheraVac by a STING agonist, cGAMP, because they synergize in activating DC’s and produced more immunostimulating IL-12p70 and TNFα cytokines. We therefore treated five different tumor types including melanin producing B16F1, M3, and M4 mouse melanomas that are homologous to human melanomas with intratumoral delivery of cGAMP and TheraVac. This eradicated 80% of the B16F1, 80% of the M3 and 60% of the M4 tumors, but still failed to cure the non-melanin producing undifferentiated M1 and M2 tumors. Biopsies of M3 tumor treated with TheraVac plus cGAMP showed a significant increase of CD8+ CTL’s infiltrating into the tumor. Importantly, there was a marked increase of both CD4 and CD8 memory T cells and generation of functional tumor specific CTLs in tumor-draining lymph nodes. The resultant tumor-free mice were selectively resistant to subsequent challenge with the same tumors, indicating long-term tumor specific protective immunity. Overall, our findings have important implications for clinical trials with a combination of immunotherapeutics to cure melanin producing human melanomas, without the need for exogenous tumor antigens and no obvious toxic effects in mice.

Virus-Like Particle-Drug Conjugates Induce Protective, Long-lasting Adaptive Antitumor Immunity in the Absence of Specifically Targeted Tumor Antigens.

This study examined the ability of a papillomavirus-like particle drug conjugate, belzupacap sarotalocan (AU-011), to eradicate subcutaneous tumors after intravenous injection and to subsequently elicit long-term antitumor immunity in the TC-1 syngeneic murine tumor model. Upon in vitro activation with near-infrared light (NIR), AU-011-mediated cell killing was proimmunogenic in nature, resulting in the release of damage-associated molecular patterns such as DNA, ATP, and HMGB-1, activation of caspase-1, and surface relocalization of calreticulin and HSP70 on killed tumor cells. A single in vivo administration of AU-011 followed by NIR caused rapid cell death, leading to long-term tumor regression in ∼50% of all animals. Within hours of treatment, calreticulin surface expression, caspase-1 activation, and depletion of immunosuppressive leukocytes were observed in tumors. Combination of AU-011 with immune-checkpoint inhibitor antibodies, anti-CTLA-4 or anti-PD-1, improved therapeutic efficacy, resulting in 70% to 100% complete response rate that was durable 100 days after treatment, with 50% to 80% of those animals displaying protection from secondary tumor rechallenge. Depletion of CD4+ or CD8+ T cells, either at the time of AU-011 treatment or secondary tumor rechallenge of tumor-free mice, indicated that both cell populations are vital to AU-011's ability to eradicate primary tumors and induce long-lasting antitumor protection. Tumor-specific CD8+ T-cell responses could be observed in circulating peripheral blood mononuclear cells within 3 weeks of AU-011 treatment. These data, taken together, support the conclusion that AU-011 has a direct cytotoxic effect on tumor cells and induces long-term antitumor immunity, and this activity is enhanced when combined with checkpoint inhibitor antibodies.

Nrf2/HO-1 Axis Regulates the Angiogenesis of Gastric Cancer via Targeting VEGF.

PurposeGastric cancer (GC) is one of the most fatal digestive tumors worldwide. Abnormal activation or accumulation of the nuclear factor-erythroid 2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) axis is a malignant event in numerous solid tumors. However, its involvement in angiogenesis of GC remains unknown. This study investigated the role of the Nrf2/HO-1 axis in angiogenesis of GC.MethodsThe expression of Nrf2, HO-1, and vascular endothelial growth factor (VEGF) in BGC-823 cells under hypoxia was analyzed using immunocytochemistry, immunofluorescence, Western blotting, and quantitative polymerase chain reaction. The effects of brusatol (Nrf2 inhibitor) and tert-butylhydroquinone (Nrf2 inducer) on these factors and angiogenesis were examined using immunofluorescence, Western blotting, quantitative polymerase chain reaction, and tube formation assay. Moreover, immunohistochemistry and Western blotting were used to determine these factors and microvessel density in tumor and normal tissues of tumor-bearing and tumor-free mice, respectively. Immunohistochemistry and Western blotting were employed to examine these factors and microvessel density in human paracancerous tissues, well-differentiated GC, and poorly differentiated GC. The correlations between Nrf2, HO-1, and VEGF gene expression in 375 patients with GC from The Cancer Genome Atlas cohort were analyzed.ResultsThe expression of Nrf2, HO-1, and VEGF was increased in hypoxic BGC-823 cells (P<0.05). Although brusatol decreased their expression and angiogenesis (P<0.05), tert-butylhydroquinone had the opposite effect (P<0.05). Moreover, the expression of Nrf2, HO-1, and VEGF, and microvessel density in tumor tissues was higher than that recorded in normal tissues of nude mice (P<0.05). Similarly, these parameters were low in paracancerous tissues, but high in GC tissues (P<0.05). Also, they were weak in well-differentiated GC, but strong in poorly differentiated GC (P<0.05). In addition, there was a significant correlation between Nrf2, HO-1, and VEGF (P<0.05).ConclusionThe Nrf2/HO-1 axis may regulate the angiogenesis of GC via targeting VEGF. These findings provide a promising biomarker and potential treatment target for GC.

BIMG-05. TO BE OR NOT TO BE GLYCOLYTIC: DEUTERATED GLUCOSE-BASED ASSESSMENT OF THE WARBURG EFFECT ALLOWS NON-INVASIVE IMAGING OF TUMOR BURDEN AND TREATMENT RESPONSE IN MUTANT IDH GLIOMAS IN VIVO

The Warburg effect, characterized by elevated glucose uptake and flux to lactate, is a metabolic hallmark of cancer. Recent studies have identified deuterium 2H-magnetic resonance spectroscopy (MRS) using 6,6’-2H-glucose as a novel method of imaging the Warburg effect in high-grade primary glioblastomas (GBMs). However, its utility for imaging low-grade gliomas has not been tested. The goal of this study was to determine whether 6,6’-2H-glucose can be used for imaging tumor burden and treatment response in mutant isocitrate dehydrogenase (IDHmut) low-grade gliomas in vivo. We examined mice bearing orthotopic tumors of the patient-derived BT257 astrocytoma model. 1H-MRS, providing a readout of steady-state metabolite levels, confirmed the presence of 2-hydroxyglutarate, the product of IDHmut, in BT257 tumor tissue but not normal brain. Previous studies comparing IDHmut gliomas with GBMs suggest that IDHmut gliomas undergo lactate dehydrogenase silencing, potentially leading to a non-glycolytic phenotype. Nevertheless, our results indicated that, compared to normal brain, glucose uptake and concomitant flux to lactate were significantly higher in BT257 tumor tissue. Importantly, 6,6’-2H-glucose metabolism to lactate was observed in BT257 tumor-bearing mice, but not tumor-free mice. Furthermore, imaging studies confirmed spatial localization of lactate production to the tumor vs. contralateral normal brain. We then examined the ability of 6,6’-2H-glucose to assess treatment response. Poly-(adenosine 5′-diphosphate-ribose) polymerase inhibitors (PARPi) inhibit IDHmut glioma growth and are in clinical trials for IDHmut glioma patients. Treatment with the PARPi niraparib reduced 6,6’-2H-glucose flux to lactate in BT257 tumor-bearing mice. Importantly, this reduction was observed at early time-points when no difference in tumor volume could be detected using anatomical imaging, pointing to the ability of 6,6’-2H-glucose to assess pseudoprogression. Collectively, our results suggest that IDHmut gliomas display a glycolytic phenotype amenable to non-invasive 2H-MRS-based imaging of tumor burden and treatment response.