CT26 Tumor Cells Research Articles

Modulation of the tumor microenvironment by intratumoral administration of IMO-2125, a novel TLR9 agonist, for cancer immunotherapy.

The objective of cancer immunotherapy is to prime the host's immune system to recognize and attack malignant tumor cells. IMO‑2125, a Toll‑like receptor9(TLR9) agonist, exhibited potent antitumor effects in the murine syngeneic A20 lymphoma and the CT26 colon carcinoma models. IMO‑2125 exhibited superior A20 antitumor activity when injected intratumorally(i.t.) compared with equivalent subcutaneous doses. In mice bearing dual CT26 grafts, the i.t. injection of right flank tumors elicited infiltration of cluster of differentiation(CD)3+ T lymphocytes into tumors, resulting in the regression of injected and uninjected left flank tumors. Depletion of CD8+, but not CD4+, T‑cells abrogated the IMO‑2125‑mediated antitumor response, suggesting that CD8+ lymphocytes are required for the antitumor activity. In mice harboring right flank CT26 and left flank β‑galactosidase (β‑gal)‑expressing CT26.CL25 grafts, the i.t. administration of IMO‑2125 to the CT26 graft resulted in potent and dose‑dependent antitumor activity against the two grafts. Splenic T‑cells isolated from these mice responded to AH1 antigen (present in the two tumors) and β‑gal antigen (present only in CT26.CL25) in an interferon γenzyme‑linked immunospot assay, suggesting the clonal expansion of T‑cells directed against antigens from the two tumors. Mice with ablated CT26 tumors by previous IMO‑2125 treatment rejected re‑implanted CT26 tumor cells, but not A20 tumor cells, demonstrating that the initial IMO‑2125 treatment created a long‑lived tumor‑specific immune memory of CT26 antigens. A quantitative increase in CD3+ Tlymphocytes in injected A20 tumors and an upregulation of selected checkpoint genes, including indoleamine2,3‑dioxygenase (IDO)‑1, IDO‑2, programmed cell death protein-1(PD-1); programmed cell death protein ligand1(PD-L1), carcinoembryonic antigen‑related cell adhesion molecule1, tumor necrosis factor receptor superfamily member4(OX40), OX40 ligand, T‑cell immunoglobulin and mucin‑domain‑containing 3protein, lymphocyte‑activation gene3, cytotoxic T‑lymphocyte‑associated protein4, were observed following IMO‑2125 treatment. IMO‑2125 also increased immune checkpoint gene expression in injected and uninjected contralateral CT26 tumors, suggesting that the co‑administration of anti‑CTLA‑4, anti‑PD‑1 or anti‑PD‑L1 therapies with IMO‑2125 may provide additional therapeutic efficacy.

Synergy between peroxisome proliferator-activated receptor γ agonist and radiotherapy in cancer.

Angiogenesis and inflammation are crucial processes through which the tumor microenvironment (TME) influences tumor progression. In this study, we showed that peroxisome proliferator‐activated receptor γ (PPARγ) is not only expressed in CT26 and 4T1 tumor cell lines but also in cells of TME, including endothelial cells and tumor‐associated macrophages (TAM). In addition, we showed that rosiglitazone may induce tumor vessel normalization and reduce TAM infiltration. Additionally, 4T1 and CT26 tumor‐bearing mice treated with rosiglitazone in combination with radiotherapy showed a significant reduction in lesion size and lung metastasis. We reported that a single dose of 12 Gy irradiation strongly inhibits local tumor angiogenesis. Secretion of C‐C motif chemokine ligand 2 (CCL2) in response to local irradiation facilitates the recruitment of migrating CD11b+ myeloid monocytes and TAM to irradiated sites that initiate vasculogenesis and enable tumor recurrence after radiotherapy. We found that rosiglitazone partially decreases CCL2 secretion by tumor cells and reduces the infiltration of CD11b+ myeloid monocytes and TAM to irradiated tumors, thereby delaying tumor regrowth after radiotherapy. Therefore, combination of the PPARγ agonist rosiglitazone with radiotherapy enhances the effectiveness of radiotherapy to improve local tumor control, decrease distant metastasis risks and delay tumor recurrence.

Tumor necrosis factor receptor II (TNFR2) promotes the growth of mouse CT26 colon cancer

Abstract TNFR2 is expressed by several tumor cells including colon cancer, Hodgkin lymphoma, myeloma, renal carcinoma and ovarian cancer. Recently, TNFR2 is becoming appreciated as an oncogene. However, the exact role of TNFR2 on the tumor development remains to be fully understood. In this study, we examined the tumorigenesis and growth of mouse CT26 colon cancer cell lines with genetically modified TNFR2 expression in syngeneic Balb/c mice. We used CRISPR/Cas9- induced loss-of-function approaches to obtain stable TNFR2 KO CT26 cell line and gain-of-function techniques to obtain TNFR2 overexpressing CT26 cell line. WT, TNFR2 KO and TNFR2 overexpressing CT26 cells were inoculated s.c. into the mice. Although TNFR2 overexpressing CT26 tumor grew markedly faster than TNFR2 KO CT26 cells, there was no difference in the initial tumorigenesis, Intriguingly, all TNFR2 KO CT26 tumors completely regressed 2 weeks after inoculation. The proportion of Foxp3+ Tregs, as well as their TNFR2 expression, in the draining LNs was markedly higher in mice bearing TNFR2 overexpressing CT26 tumor. The levels of soluble TNFR2 in the peripheral blood of CT26 tumor bearing mice were ~3 folds higher than that in tumor free mice, which is comparable with the elevated levels of soluble TNFR2 in human tumor patients. In mice bearing TNFR2 overexpressing CT26 tumors, the levels of soluble TNFR2 was >4 folds higher than that in mice bearing WT CT26 tumors. In vitro, exogenous TNF was able to up-regulate TNFR2 surface expression on CT26 tumor cells. Taken together, our data suggest that TNF-TNFR2 signaling pathway may play a major role in tumor growth and tumor immune evasion, and thus may represent an important therapeutic target.

Synthesis and evaluation of 68 Ga-HBED-CC-EDBE-folate for positron-emission tomography imaging of overexpressed folate receptors on CT26 tumor cells.

The 68 Ga is a positron-emitting radionuclide that can be combined with bifunctional chelating agents and bioactive substances for use as positron-emission tomography (PET) diagnostic agents. The HBED-CC is an acyclic chelating agent that is rapidly labeled with 68 Ga under mild conditions. To target cancer cells, bioactive substances can be conjugated to the carboxyl terminus of HBED-CC. Because folic acid strongly binds to folate receptors that are overexpressed on the surfaces of many types of cancer cells, it was coupled with HBED-CC through a small polyethylene glycol-based linker (EDBE) to generate an active, receptor-selective targeting system. The HBED-CC-EDBE-folate (HCEF) precursor was readily labeled with 68 Ga in 5minutes at room temperature (98% radiochemical yield; 99% radiochemical purity after isolation). In cellular uptake tests, higher uptakes of 68 Ga-HCEF were observed for the CT26 and KB cell lines (which express folate receptors) than for the A549 cell line (which does not). Finally, in vivo micro-PET measurements over 2hours of binding in BALB/c mice into which CT26 tumors had been transplanted showed the selective accumulation of 68 Ga-HCEF in the folate receptor-expressing CT26 tumors. These results confirmed the potential of 68 Ga-HCEF as a PET diagnostic agent for tumors that express folate receptors.

Abstract 1015: Directionality of T-cell-mediated cross-protection against the same tumor in lungs versus skin

Abstract Immunotherapy is a new pillar of cancer therapy. One theoretical advantage of immunotherapy of cancer is that effector cells induced at one site should be able to kill metastatic cancer cells in other sites or tissues. On the other hand, it has been recognized that each tissue has unique immune components that play critical roles in protection against pathogens. However, very little is known whether effector T cells induced against tumors in one tissue can work against the same tumors in other tissues. To address this question, we compared the effect of effector cells induced against the same tumor cells growing in either the skin or the lung by using CT26 murine tumor models. Rejection of s.c. CT26 tumors was achieved by pretreatment with anti-CD25, which blocks the function of Treg cells. Both CD4 and CD8 T cells were necessary for the protection. When anti-CD25-pretreated mice challenged with s.c. CT26 were simultaneously inoculated i.v. with CT26, they also rejected tumors in the lung, while anti-CD25-pretreated mice without s.c. CT26 did not. This observation suggested that T cell mediated anti-tumor protective immunity induced against s.c. tumors can also protect against lung metastases of the same tumors. In contrast to Treg depletion which allowed for the induction of protective immunity in the s.c. tumor model, NKT cell-deficiency in CD1d KO mice induced significant CD8 T cell-mediated protection against lung metastasis of CT26 but had no effect on the growth of s.c. CT26 tumors. When CD1d KO mice rejecting i.v. CT26 were simultaneously challenged with s.c. CT26, the development of s.c. tumors was not affected, indicating that tumor rejection induced against the CT26 in the lung did not confer protection for the same tumor cells in the skin. Since the protection against CT26 in the lung in CD1d KO mice is mediated by CD8 T cells, we transferred T cells from CD1d KO mice inoculated i.v. with CT26 into RAG1 KO recipients, and challenged the recipient mice with the CT26 tumor cells. The recipient RAG1 KO mice were highly resistant to CT26 inoculated i.v. but not s.c. confirming that the CD8 T cells protective in the lung are not protective in the skin. These data indicate the effector cells against the same tumor do not work in all tissues, and the induction site of the effector T cells is critical to control metastasis. Citation Format: Jessica J. O'Konek, Elena Ambrosino, Anja Bloom, Liat Izhak, Jay A. Berzofsky, Masaki Terabe. Directionality of T-cell-mediated cross-protection against the same tumor in lungs versus skin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1015. doi:10.1158/1538-7445.AM2017-1015

Abstract 2612: Anti-Tigit induces T cell mediated anti-tumor immune response and combines with immune checkpoint inhibitors to enhance strong and long term anti-tumor immunity

Abstract TIGIT (T cell immunoreceptor with Ig and ITIM domains) has been recently described as an inhibitory receptor which blocks CD8 T cell-mediated anti-tumor immune responses. We have generated an anti-mouse TIGIT antibody (313R12) to evaluate drug efficacy and mechanism of action in pre-clinical tumor models. Anti-TIGIT as a single agent promoted an anti-tumor immune response in multiple syngeneic mouse tumor models. Anti-TIGIT enhanced tumor specific T cell responses, particularly of the Th1 type and reduced Th2 type responses and also increased the function of cytotoxic T cells. Furthermore, anti-TIGIT displayed combination activity with immune checkpoint inhibitors anti-PD1 and anti-PDL1 in inhibiting tumor growth, promoting complete tumor rejection and significantly increasing mouse survival in the murine CT26 colon carcinoma model as compared to controls and single agents alone. Mice “cured” with anti-TIGIT/anti-PDL1 or anti-TIGIT/anti-PD1 combination treatments did not form tumors upon subsequent re-challenges with increasing number of CT26 tumor cells, suggesting the existence of immunologic memory. IL2 and tumor-specific IFN-γ production by splenic T cells were increased in mice who responded to combination treatment compared to controls. Additionally, both effector and memory CD8+ T cell frequencies were increased within the total CD8+ T cell population in responding mice. We also demonstrated a systemic increase in tumor-specific CD8 T cells after anti-TIGIT/anti-PDL1 combination treatment compared to controls. Therefore, these results suggest that co-targeting of TIGIT and PD1 or PDL1 may be an effective and durable cancer therapy by increasing T cell-mediated anti-tumor immune responses and promoting long-term immunological memory. Citation Format: Minu K. Srivastava, Rui Yun, Erin Mayes, Janice Yu, Hyun-Bae Jie, Fumiko Axelrod, Ming-Hong Xie, Jorge Monteon, Andrew Lam, May Ji, Yuwang Liu, John Lewicki, Tim Hoey, Austin Gurney, Angie Inkyung Park. Anti-Tigit induces T cell mediated anti-tumor immune response and combines with immune checkpoint inhibitors to enhance strong and long term anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2612. doi:10.1158/1538-7445.AM2017-2612

Magnesium improves cisplatin-mediated tumor killing while protecting against cisplatin-induced nephrotoxicity.

Approximately 30% of all cancer patients treated with cisplatin, a widely used broad-spectrum chemotherapeutic agent, experience acute kidney injury (AKI). Almost all patients receiving cisplatin have magnesium (Mg) losses, which are proposed to aggravate AKI. Currently, there are no methods to successfully treat or prevent cisplatin-AKI. Whereas Mg supplementation has been shown to reduce AKI in experimental models and several small clinical trials, the effects of Mg status on tumor outcomes in immunocompetent tumor-bearing mice and humans have not been investigated. The purpose of this study was to further examine the effects of Mg deficiency (±Mg supplementation) on cisplatin-mediated AKI and tumor killing in immunocompetent mice bearing CT26 colon tumors. Using a model where cisplatin alone (20 mg/kg cumulative dose) produced minimal kidney injury, Mg deficiency significantly worsened cisplatin-mediated AKI, as determined by biochemical markers (blood urea nitrogen and plasma creatinine) and histological renal changes, as well as markers of renal oxidative stress, inflammation, and apoptosis. By contrast, Mg supplementation blocked cisplatin-induced kidney injury. Using LLC-PK1 renal epithelial cells, we observed that Mg deficiency or inhibition of Mg uptake significantly enhanced cisplatin-induced cytotoxicity, whereas Mg supplementation protected against cytotoxicity. However, neither Mg deficiency nor inhibition of Mg uptake impaired cisplatin-mediated killing of CT26 tumor cells in vitro. Mg deficiency was associated with significantly larger CT26 tumors in BALB/c mice when compared with normal-fed control mice, and Mg deficiency significantly reduced cisplatin-mediated tumor killing in vivo. Finally, Mg supplementation did not compromise cisplatin's anti-tumor efficacy in vivo.

In vivo amelioration of endogenous antitumor autoantibodies via low-dose P4N through the LTA4H/activin A/BAFF pathway

Cancer progression is associated with the development of antitumor autoantibodies in patients' sera. Although passive treatment with antitumor antibodies has exhibited remarkable therapeutic efficacy, inhibitory effects on tumor progression by endogenous antitumor autoantibodies (EAAs) have been limited. In this study, we show that P4N, a derivative of the plant lignan nordihydroguaiaretic acid (NDGA), enhanced the production of EAAs and inhibited tumor growth at low noncytotoxic concentrations via its immunoregulatory activity. Intratumoral injection of P4N improved the quantity and quality of EAAs, and passive transfer of P4N-induced EAAs dramatically suppressed lung metastasis formation and prolonged the survival of mice inoculated with metastatic CT26 tumor cells. P4N-induced EAAs specifically recognized two surface antigens, 78-kDa glucose-regulated protein (GRP78) and F1F0 ATP synthase, on the plasma membrane of cancer cells. Additionally, P4N treatment led to B-cell proliferation, differentiation to plasma cells, and high titers of autoantibody production. By serial induction of autocrine and paracrine signals in monocytes, P4N increased B-cell proliferation and antibody production via the leukotriene A4 hydrolase (LTA4H)/activin A/B-cell activating factor (BAFF) pathway. This mechanism provides a useful platform for studying and seeking a novel immunomodulator that can be applied in targeting therapy by improving the quantity and quality of the EAAs.

Repeated cycles of 5-fluorouracil chemotherapy impaired anti-tumor functions of cytotoxic T cells in a CT26 tumor-bearing mouse model.

BackgroundRecently, the immunostimulatory roles of chemotherapeutics have been increasingly revealed, although bone marrow suppression is still a common toxicity of chemotherapy. While the numbers and ratios of different immune subpopulations are analyzed after chemotherapy, changes to immune status after each cycle of treatment are less studied and remain unclear.ResultsTo determine the tumor-specific immune status and functions after different cycles of chemotherapy, we treated CT26 tumor-bearing mice with one to four cycles of 5-fluorouracil (5-FU). Overall survival was not improved when more than one cycle of 5-FU was administered. Here we present data concerning the immune statuses after one and three cycles of chemotherapy. We analyzed the amount of spleen cells from mice treated with one and three cycles of 5-FU as well as assayed their proliferation and cytotoxicity against the CT26 tumor cell line. We found that the absolute numbers of CD8 T-cells and NK cells were not influenced significantly after either one or three cycles of chemotherapy. However, after three cycles of 5-FU, proliferated CD8 T-cells were decreased, and CT26-specific cytotoxicity and IFN-γ secretion of spleen cells were impaired in vitro. After one cycle of 5-FU, there was a greater percentage of tumor infiltrating CD8 T-cells. In addition, more proliferated CD8 T-cells, enhanced tumor-specific cytotoxicity as well as IFN-γ secretion of spleen cells against CT26 in vitro were observed. Given the increased expression of immunosuppressive factors, such as PD-L1 and TGF-β, we assessed the effect of early introduction of immunotherapy in combination with chemotherapy. We found that mice treated with cytokine induced killer cells and PD-L1 monoclonal antibodies after one cycle of 5-FU had a better anti-tumor performance than those treated with chemotherapy or immunotherapy alone.ConclusionsThese data suggest that a single cycle of 5-FU treatment promoted an anti-tumor immune response, whereas repeated chemotherapy cycles impaired anti-tumor immune functions. Though the amount of immune cells could recover after chemotherapy suspension, their anti-tumor functions were damaged by multiple rounds of chemotherapy. These findings also point towards early implementation of immunotherapy to improve the anti-tumor effect.Electronic supplementary materialThe online version of this article (doi:10.1186/s12865-016-0167-7) contains supplementary material, which is available to authorized users.

TLR7-based cancer immunotherapy decreases intratumoral myeloid-derived suppressor cells and blocks their immunosuppressive function

ABSTRACTMyeloid-derived suppressor cells (MDSC) are a heterogeneous population of immature myeloid cells with the capacity to inhibit immunological responses. During cancer progression, MDSC are recruited to the tumor sites and secondary lymphoid organs, leading to the suppression of the antitumor function of NK and T cells. Here, we show that the TLR7/8 agonist resiquimod (R848) has a direct effect on MDSC populations in tumor-bearing mice. Systemic application of R848 led to a rapid reduction in both intratumoral and circulating MDSC. The subpopulation of monocytic MDSC (m-MDSC) was the most affected by R848 treatment with an up to 5-fold decrease in the tumor. We found that TLR7 stimulation in tumor-bearing mice led to a maturation and differentiation of MDSC with upregulation of the surface molecules CD11c, F4/80, MHC-I, and MHC-II. MDSC treated with R848 lost their immunosuppressive function and acquired instead an antigen-presenting phenotype with the capability to induce specific T-cell proliferation. Importantly, we found that MDSC co-injected s.c. with CT26 tumor cells lost their ability to support tumor growth after pretreatment with R848. Our results demonstrate that treatment of tumor-bearing mice with a TLR7/8 agonist acts directly on MDSC to induce their maturation and leads them to acquire a non-suppressive status. Considering the obstacles posed by MDSC for cancer immunotherapy, targeting these cells by a TLR7/8 agonist may improve immune responses against cancer.

Anticancer Properties of Chrysin on Colon Cancer Cells, In vitro and In vivo with Modulation of Caspase-3, -9, Bax and Sall4.

Background The SALL4/Sall4 is constitutively expressed in human and mice. SALL4 mRNA could be used as a marker for the diagnosis of different types of cancers. On the other hand, chrysin has diverse biological properties. Objectives In the present study, the effect of the chrysin was investigated on the CT26 colon cancer in vitro and in vivo. Furthermore, the expression levels of the stem cell markers; sall4 and Bax was analyzed, as well. Materials and Methods The cytotoxic effects and the type of cell death induced by chrysin were evaluated using a number of biological assays. The apoptotic pathway was examined by caspase-3and caspase-9 assay. The in vivo antitumor efficacy of chrysin on transplanted CT26 tumor cells in BALB/c mice was investigated. In addition, mRNA expression of sall4, Bax was analyzed with RT-PCR. Results MTT assay and morphological characteristics showed that chrysin exerted a cytotoxic effect on CT26 cells in a dose dependent manner with IC50= 80 μg.mL-1. The biological assays have indicated that chrysin administrated cytotoxicity on colon cancer cells through recruitment of the apoptosis. Caspase-3 and caspase-9 colorimetric assays, in addition to Bax expression analysis, have indicated the involvement of intrinsic apoptotic pathway in the cytotoxic effect of the chrysin. The in vivo assay revealed a remarkable reduction of the colon tumor volume in treated mice (8, 10 mg.kg -1) as compared to the untreated mice. RT-PCR elucidated that chrysin attenuated tumor volume through down regulation of the sall4 and up-regulation of the Bax. Conclusions It was demonstrated that chrysin accomplishes anti-cancer effect on colon cancer cells via induction of the apoptosis and attenuation of the sall4 the expression. These findings introduce chrysin as an efficient apoptosis based therapeutic agent against colon cancer.

Abstract 2328: ICOS signaling promotes CD4+ effector T-cell function during antitumor responses

Abstract Inducible costimulator (ICOS) is a CD28-related cell surface receptor which provides an important costimulatory signal to T cells during activation. Prior work has found that anti-ICOS antibodies can promote anti-tumor immunity in vivo, but it is unclear whether this effect results from ICOS signaling blockade and/or agonism, or whether direct antibody-mediated depletion of ICOS+ Tregs is responsible for enhancing anti-tumor immunity. Here, we generated anti-ICOS-L blocking antibodies in mice and engineered such antibodies to contain mouse IgG1 Fc regions with low Fc receptor engagement and good pharmacokinetics. These reagents were used in vivo to specifically block ICOS signaling in syngeneic mouse tumor models without potential depletion of immune cells through ADCC. The role of ICOS signaling in anti-tumor immunity was addressed both in isolation, and together with combination immunotherapy treatments of mouse syngeneic tumor models, followed by flow cytometry-based characterization of peripheral and tumor-infiltrating T cell subsets. Finally, CT26 tumor cells were engineered to express mouse ICOS-L in a doxycycline-inducible fashion to promote additional ICOS signaling within the tumor microenvironment. Initial characterization of ICOS blockade in tumor models revealed that inhibition of ICOS signaling alone was sufficient to mediate a modest anti-tumor effect, and characterization of intratumoral T cell populations demonstrated a specific reduction of intratumoral Tregs with ICOS signal deprivation. A survey of previously identified immunomodulators found that, like anti-CTLA-4, anti-OX40 treatment of tumors was able to drive upregulation of ICOS on multiple T cell subsets, while anti-4-1BB therapy was not. Combining ICOS-L blockade with these additional immunotherapeutic approaches showed that inhibition of ICOS signaling had little impact on CD8+ T cell-mediated anti-tumor immunity induced by anti-4-1BB. However, the efficacy of anti-OX40 therapy, which depletes Tregs and relies to a large degree on CD4+ effector T cells responses, was significantly impaired with ICOS-L blockade. In contrast, the induction of additional intratumoral ICOS signaling in established tumors increased the frequency of tumor rejection and overall survival when combined with anti-OX40 therapy. Taken together, these results show that ICOS signaling during the anti-tumor immune response acts on both effector and regulatory T cell subsets, and thus manipulation of ICOS signaling alone may be an inefficient strategy for immunotherapy. However, the use of ICOS agonists in combination with Treg-depleting therapies such as anti-OX40 should limit the potential to promote Treg function or expansion and instead result only in enhanced CD4+ effector T cell responses. Citation Format: Todd C. Metzger, Hua Long, Shobha Potluri, John C. Lin, Reid M.R. Feldman. ICOS signaling promotes CD4+ effector T-cell function during antitumor responses. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2328.

Abstract 5262: Chemopreventive and angiopreventive activity of a purified polyphenol-rich extract from olive mill wastewaters

Abstract The presence of diverse phenolic molecules in dietary elements, has been shown to prevent the occurrence of a variety of chronic and inflammatory diseases. Olives and extra virgin oil, a basic component of mediterranean diet represent an important source of these poliphenols, including hydroxytyrosol. While the strong antioxidant potential of these molecules has extensively investigated, their anti-angiogenic and chemopreventive activities remain unknown. Here we assessed the anti-angiogenic and chemopreventive activities exerted by an extracts from olive mill wastewaters (OMWWs), termed A009, which represent a waste product from olive oil industry, in vitro and in vivo on endothelial and different tumour cell lines, as compared with hydroxytyrosol alone The ability of A009 to affect cell proliferation and survival was evaluated on human umbelical endothelial vein cells (HUVECs), six different tumor cell lines, MCF-7 and MDA-MB-231 (breast), HT-29 and HCT-116 (colon) PC-3 and DU-145 (prostate) and the murine CT26 CRC cells by MTT assay, while the induction of apoptosis and reactive oxygen species (ROS) were assessed by flow cytometry. Functional studies evaluated the capacity of OMWWs to interfere with endothelial cell tube formation, migration and invasion by morphogenesis and Boyden chamber assays, respectively. Finally, the inhibition of angiogenesis and tumor cell growth was evaluated in vivo, by the matrigel sponge assay and tumor xenograft. The A009 extract was able to inhibit both HUVECs and tumor cell lines growth in a dose dependent manner, exerting a stronger inhibitory effect as compared to the pure hydroxytyrosol alone. This effect was directly associated with the induction of apoptosis and ROS on HUVECs. HT-29 anc HCT-116 CRC cell lines exposed to A009 decreased thei ability to release VEGF and IL-8. Functional studies of HUVECs exposed to A009 demostrated impaired migratory and invasive abilities as far as reduced capability to form capillary-lile-structure in a dose dependent manner. Finally, A009s interfered with angiogenesis and CT26 tumor cell growth in vivo. Our results suggest that the polyphenol enriched extracts from olive oil processing (OMWWs) A009, show promising angio-preventive and chemo-preventive potentials. In particular, our data demonstrate that a pool of specific polyphenols are characterized by stronger anti-angiogenic/anti-tumor properties compared to hydroxytyrosol alone, a well known polyphenol with anti-tumor activity. Citation Format: Adriana Albini, Antonino Bruno, Barbara Bassani, Nicoletta Macrì, Francesca Caudano, Paola Corradino, Teresa Rossi, Douglas M. Noonan. Chemopreventive and angiopreventive activity of a purified polyphenol-rich extract from olive mill wastewaters. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5262.

Apoptosis inducing capacity of Holothuria arenicola in CT26 colon carcinoma cells in vitro and in vivo.

Sea cucumber is one of the classes of echinoderms, which is considered as a health marine product and possess various biological characteristics with therapeutic application. The present investigation attempted to evaluate the potential of anti-cancer Persian Gulf sea cucumber species Holothuria arenicola (H. arenicola) aqueous extract on mice colon carcinoma cells in vitro and in vivo. The CT26 carcinoma cells were treated with various concentrations of extract in 24 and 48 hr, and then its anti-proliferative effect was measured by MTT assay and morphological observations. The apoptotic effect was examined by fluorescence microscopy (DNA fragmentation assay), Flow cytometry, caspase-3 and -9 colorimetric assays. The in vivo anti-tumor efficacy of sea cucumber extract on CT26 tumor cells transplanted in BALB/c mice was also investigated. The results showed that the water extract of sea cucumber revealed remarkable anti-proliferative effect on CT26 tumor cells with IC50= 31 µg/ml with recruitment of intrinsic apoptotic pathway in vitro. In addition, the colon tumor volume in treated groups remarkably reduced in homozygous mice. Histopathological examination elucidated that sea cucumber extract attenuated tumor size and volume along with apoptosis characteristics. Moreover, RT-PCR analysis revealed that sea cucumber extract induced intrinsic apoptosis in vivo through suppression of Bcl-2 expression. Our data confirmed this notion that sea cucumber administrates anti-cancer effect that can be used as complementary in preclinical experiments, so further characterization are recommended for detection sea cucumber metabolites and clinical application.

Synthesis and evaluation of multivalent M2pep peptides for targeting alternatively activated M2 macrophages

The tumor microenvironment in the majority of cancers is known to favor polarization of tumor-associated macrophages (TAMs) to alternatively activated M2 phenotype, promoting disease progression and reducing patient survival. Effective therapy targeting this M2 macrophage population is thus a promising adjuvant to approved cancer therapies. One of the challenges in targeting M2-like TAMs is a lack of high affinity targeting ligand with good selectivity over anti-tumor M1-like TAMs. We have previously identified an M2 macrophage-targeting peptide (M2pep) that binds preferentially to murine M2 macrophages and M2-like TAMs. A fusion peptide of M2pep with pro-apoptotic peptide KLA (M2pepKLA) was further used to reduce TAM population in vivo but high concentrations and frequent dosing were required due to low binding affinity of M2pep for M2 macrophage. The goal of this study was to develop more potent TAM depletion constructs by increasing the valency of both the M2pep targeting and KLA drug domains. Divalent and tetravalent displays of M2pep ([M2pep]2–Biotin and [M2pep]4–Biotin) were synthesized and evaluated for improvement in binding avidity to the murine macrophages. High avidity and selective binding of [M2pep]2–Biotin to M2 macrophages were achieved with at least 10-fold lower concentration than required for monovalent M2pep activity. Increasing M2pep valency to four, however, resulted in a reduction in both binding activity and selectivity. Surprisingly, both divalent and tetravalent M2pep, without conjugation of any cytotoxic drug cargo, exhibited M2 macrophage-selective toxicity not observed in monovalent M2pep treatment. We next synthesized divalent M2pep with monovalent and divalent KLA ([M2pep]2–[KLA] and [M2pep]2–[KLA]2) to evaluate its enhanced potency compared to M2pepKLA. While both constructs were significantly more toxic than M2pepKLA to primary, bone marrow-derived M2 macrophage, desired selectivity was retained only with [M2pep]2–[KLA]. Finally, we evaluated all multivalent M2pep and M2pepKLA analogs using a syngeneic CT-26 tumor cell suspension. In this setting, [M2pep]4–Biotin and [M2pep]2–[KLA]2 exhibited selective toxicity to both M2-like TAMs and malignant cells but not to M1-like TAMs. Therefore, these constructs are promising anti-cancer constructs with dual-modality mechanisms: malignant cell killing and TAM-based immunomodulation.

The BRAF and MEK Inhibitors Dabrafenib and Trametinib: Effects on Immune Function and in Combination with Immunomodulatory Antibodies Targeting PD-1, PD-L1, and CTLA-4.

To assess the immunologic effects of dabrafenib and trametinib in vitro and to test whether trametinib potentiates or antagonizes the activity of immunomodulatory antibodies in vivo. Immune effects of dabrafenib and trametinib were evaluated in human CD4(+) and CD8(+) T cells from healthy volunteers, a panel of human tumor cell lines, and in vivo using a CT26 mouse model. Dabrafenib enhanced pERK expression levels and did not suppress human CD4(+) or CD8(+) T-cell function. Trametinib reduced pERK levels, and resulted in partial/transient inhibition of T-cell proliferation/expression of a cytokine and immunomodulatory gene subset, which is context dependent. Trametinib effects were partially offset by adding dabrafenib. Dabrafenib and trametinib in BRAF V600E/K, and trametinib in BRAF wild-type tumor cells induced apoptosis markers, upregulated HLA molecule expression, and downregulated certain immunosuppressive factors such as PD-L1, IL1, IL8, NT5E, and VEGFA. PD-L1 expression in tumor cells was upregulated after acquiring resistance to BRAF inhibition in vitro. Combinations of trametinib with immunomodulators targeting PD-1, PD-L1, or CTLA-4 in a CT26 model were more efficacious than any single agent. The combination of trametinib with anti-PD-1 increased tumor-infiltrating CD8(+) T cells in CT26 tumors. Concurrent or phased sequential treatment, defined as trametinib lead-in followed by trametinib plus anti-PD-1 antibody, demonstrated superior efficacy compared with anti-PD-1 antibody followed by anti-PD-1 plus trametinib. These findings support the potential for synergy between targeted therapies dabrafenib and trametinib and immunomodulatory antibodies. Clinical exploration of such combination regimens is under way.

Improved Efficacy of a Dendritic Cell-Based Vaccine against a Murine Model of Colon Cancer: The Helper Protein Effect.

PurposeTargeted immunotherapy using dendritic cells (DCs) has been employed in numerous investigations aiming at combating neoplasms. We previously showed that copulsing of an antigen with a helper protein could considerably enhance antigen presenting capacity of ex vivo–generated DCs. In this study, we attempted to administer an effective treatment in a murine model of colon cancer with DCs pulsed with the mixture of a tumor-specific gp70-derived peptide (AH1) and a helper protein, ovalbumin (OVA).Materials and MethodsFirst, the presence of gp70 in CT26 tumor cells and tumor tissues was verified using immunofluorescence and Western blot analyses. Next, DCs were purified from normal mice, loaded ex vivowith AH1 and OVA (DC-Pep-OVA), and injected into tumor-bearing mice. Tumor volume, in vitro antigen (Ag)-specific proliferation of splenic cells, and survival rate were measured to determine the efficacy of DC-Pep-OVA. As the control groups, tumor-bearing mice were vaccinated with DC-Pep, unpulsed DC, and DCs loaded with a mixture of OVA and an irrelevant peptide (P15), or were not vaccinated at all.ResultsDC-Pep-OVA showed superior efficacy over other groups, as indicated by smaller tumor volume, higher Ag-specific proliferation rate of splenic cells, and prolonged survival.ConclusionOverall, in the present study we showed for the first time that DCs copulsed with AH1 (tumor Ag) and OVA (helper molecule) could be considered as potentially robust weapons for use in future antitumor immunotherapies.

A polysaccharide from Ganoderma atrum inhibits tumor growth by induction of apoptosis and activation of immune response in CT26-bearing mice.

Ganoderma atrum is one species of edible and pharmaceutical mushroom with various biological activities. Recently, a novel polysaccharide, PSG-1, was purified from G. atrum. The antitumor activity and its mechanism of action were studied. In vitro, PSG-1 has little effect on inhibiting proliferation of CT26 tumor cells. However, the tumor size was significantly decreased in PSG-1-treated mice. The results showed that PSG-1 induced apoptosis in CT26 cells. Moreover, the intracellular cyclic AMP (cAMP) level and protein kinase A (PKA) activity were markedly increased in PSG-1-treated mice. In contrast, the contents of cyclic GMP and DAG and the PKC activity were decreased. Similarly, the expression of PKA protein was upregulated, while PKC protein expression in PSG-1-treated group was lowered. Additionally, PSG-1 increased the immune organ index and serum biochemistry parameter. In general, PSG-1 enhances the antitumor immune response, induces apoptosis in CT26-bearing mice, and could be a safe and effective adjuvant for tumor therapy or functional food.

MHC-mismatched mice liver transplantation promotes tumor growth in liver graft

Liver transplantation is a final therapeutic option for treatment of hepatic malignancies, but local recurrence remains high after surgery. However, the underlying mechanisms of local tumor recurrence are still unknown. We speculated that immunological status of transplanted liver may contribute to the progress of tumor development. CT-26 tumor cells are injected into graft after allogeneic or syngeneic liver transplantation. The growth pattern of tumor and the co-relationship of regulatory T cell and effector T cells in liver graft were observed and investigated at 3d, 6d, 9d and 15d post-transplantation. The Hepatic Replacement Area of tumor in allogeneic grafts was significantly larger than that in syngeneic grafts. The activation of tumor growth in allografts was due to the dysfunction of effector T cells mediated by regulatory T cells in liver graft. Using nude mice model, we further confirmed that regulatory T cells from allograft significantly weaken the function of effector T cells in vivo. Our data has showed that MHC-mismatched mice liver transplantation can promote tumor growth in liver graft. For the first time, we demonstrated that susceptibility to tumor development in liver graft is due to the down-regulation of effector T cells’ function mediated by the regulatory T cells.

Generation of a monoclonal antibody against the glycosylphosphatidylinositol-linked protein Rae-1 using genetically engineered tumor cells

BackgroundAlthough genetically engineered cells have been used to generate monoclonal antibodies (mAbs) against numerous proteins, no study has used them to generate mAbs against glycosylphosphatidylinositol (GPI)-anchored proteins. The GPI-linked protein Rae-1, an NKG2D ligand member, is responsible for interacting with immune surveillance cells. However, very few high-quality mAbs against Rae-1 are available for use in multiple analyses, including Western blotting, immunohistochemistry, and flow cytometry. The lack of high-quality mAbs limits the in-depth analysis of Rae-1 fate, such as shedding and internalization, in murine models. Moreover, currently available screening approaches for identifying high-quality mAbs are excessively time-consuming and costly.ResultsWe used Rae-1–overexpressing CT26 tumor cells to generate 60 hybridomas that secreted mAbs against Rae-1. We also developed a streamlined screening strategy for selecting the best anti–Rae-1 mAb for use in flow cytometry assay, enzyme-linked immunosorbent assay, Western blotting, and immunostaining.ConclusionsOur cell line–based immunization approach can yield mAbs against GPI-anchored proteins, and our streamlined screening strategy can be used to select the ideal hybridoma for producing such mAbs.