Age-induced changes in anti-tumor immunity alter the tumor immune infiltrate and impact response to immuno-oncology treatments

Introduction

Immuno-oncology (IO) research relies heavily on murine syngeneic tumor models. However, whilst the average age for a cancer diagnosis is 60 years or older, for practical purposes the majority of preclinical studies are conducted in young mice, despite the fact that ageing has been shown to have a significant impact on the immune response.

Methods

Using aged (60-72 weeks old) mice bearing CT26 tumors, we investigated the impact of ageing on tumor growth as well as the immune composition of the tumor and peripheral lymphoid organs.

Results

We found many differences in the immune cell composition of both the tumor and tumor-draining lymph node between aged and young mice, such as a reduction in the naïve T cell population and a decreased intratumoral CD8/Treg ratio in aged animals. We hypothesized that these differences may contribute to impaired anti-cancer immune responses in aged mice and therefore assessed the anti-tumor efficacy of different IO therapies in aged mice, including both co-stimulation (using an anti-OX40 antibody) and immune checkpoint blockade (using anti-PD-L1 and anti-CTLA-4 antibodies). Whilst aged mice retained the capacity to generate anti-tumor immune responses, these were significantly attenuated when compared to the responses observed in young mice.

Discussion

These differences highlight the importance of age-related immunological changes in assessing and refining the translational insights gained from preclinical mouse models.

Expression of GFP and DsRed fluorescent proteins after gene electrotransfer of tumour cells in vitro

Fluorescent reporter genes are widely used to study the transfection of various types of primary cells and cell lines. The aim of our research was to investigate the expression dynamics of GFP and DsRed reporter genes individually and combined after gene electrotransfer of plasmids with two different electroporation protocols in B16F10 and CT26 cells in vitro. The cytotoxicity after gene electrotransfer of both plasmids was first determined. Second, the intensity of fluorescence and the percentage of cells transfected with both plasmids individually and in combination were monitored in real time. The results show that the percentage of viability after gene electrotransfer of plasmids using the EP2 pulses was significantly higher compared to the EP1 pulses. In contrast, the percentage of transfected cells and fluorescence intensity were higher after gene electrotransfer with the EP1 pulse protocol. Moreover, the percentage of transfected cells was higher and started earlier in the B16F10 cell line than in the CT26 cell line. However, fluorescence intensity was higher in CT26 cells. Co-expression of fluorescent proteins was achieved only in a small number of cells. In conclusion, this study elucidated some of the dynamics of reporter gene expression in cancer cell lines after gene electrotransfer.

Inhibition of mouse colon cancer growth following immunotherapy with a fraction of hydatid cyst fluid

BACKGROUND

Hydatid cyst is the larval stage of the tape worm Echinococcus granulosus which is located in human and livestock viscera. There are some scientific evidences indicating that parasitic infections induce antitumor activity against certain types of cancers. In this study, the effects of a fraction of hydatid cyst fluid on colon cancer tumor in BALB/c mice were investigated.

MATERIALS AND METHODS

In this experimental work six groups of mice were challenged with mouse colon cancer cells. 5 days later when the sign of tumor growth in mice was seen, group 1-4 were injected with hydatid cyst fluid, the 78 kDa fraction, live protoscolices and BCG respectively. Group five was injected with alum alone and the sixth group left intact without any injection. The size of the tumor was measured and compared in all groups. Then blood samples of mice were evaluated for serum cytokine levels.

RESULT

In mice injected with hydatid cyst antigens especially a fraction of hydatid cyst fluid, tumor size was smaller than the that of control groups and the difference of tumor size in cases and control groups was statistically significant.

CONCLUSION

The results of this study showed that injection of mice with a fraction of hydatid cyst fluid significantly inhibits the growth of mouse colon cancer and this inhibition may be related to effect of immune response to these antigens.

Chemokine Homeostasis in Healthy Volunteers and during Pancreatic and Colorectal Tumor Growth in Murine Models

Chemokines are involved in the humoral regulation of body homeostasis. Changes in the blood level of chemokines were found in cancer, atherosclerosis, diabetes, and other systemic diseases. It is essential to distinguish the effects of co-morbid pathologies and cancer on the level of chemokines in the blood. We aimed to analyze, by multiplex cytometry, the levels of chemokines in the blood of healthy young volunteers as well as of intact mice and mice with CT26 colon and Pan02 pancreatic tumors. Two types of chemokines were identified both in human and murine plasmas: homeostatic ones, which were found in high concentrations (>100 pg/mL), and inducible ones, which can be undetectable or determined at very low levels (0−100 pg/mL). There was a high variability in the chemokine levels, both in healthy humans and mice. To analyze chemokine levels during tumor growth, C57BL/6 and BALB/c were inoculated with Pan02 or CT26 tumor cells, accordingly. The tumors significantly differed in the growth and the mortality of mice. However, the blood chemokine levels did not change in tumor-bearing mice until the very late stages. Taken collectively, blood chemokine level is highly variable and reflects in situ homeostasis. Care should be taken when considering chemokines as prognostic parameters or therapeutic targets in cancer.

Amplification of the CXCR3/CXCL9 axis via intratumoral electroporation of plasmid CXCL9 synergizes with plasmid IL-12 therapy to elicit robust anti-tumor immunity

Clinical studies have demonstrated that local expression of the cytokine IL-12 drives interferon-gamma expression and recruits T cells to the tumor microenvironment, ultimately yielding durable systemic T cell responses. Interrogation of longitudinal biomarker data from our late-stage melanoma trials identified a significant on-treatment increase of intratumoral CXCR3 transcripts that was restricted to responding patients, underscoring the clinical relevance of tumor-infiltrating CXCR3⁺ immune cells. In this study, we sought to understand if the addition of DNA-encodable CXCL9 could augment the anti-tumor immune responses driven by intratumoral IL-12. We show that localized IL-12 and CXCL9 treatment reshapes the tumor microenvironment to promote dendritic cell licensing and CD8⁺ T cell activation. Additionally, this combination treatment results in a significant abscopal anti-tumor response and provides a concomitant benefit to anti-PD-1 therapies. Collectively, these data demonstrate that a functional tumoral CXCR3/CXCL9 axis is critical for IL-12 anti-tumor efficacy. Furthermore, restoring or amplifying the CXCL9 gradient in the tumors via intratumoral electroporation of plasmid CXCL9 can not only result in efficient trafficking of cytotoxic CD8⁺ T cells into the tumor but can also reshape the microenvironment to promote systemic immune response.

A novel cocktail therapy based on quintuplet combination of oncolytic herpes simplex virus-2 vectors armed with interleukin-12, interleukin-15, GM-CSF, PD1v, and IL-7 × CCL19 results in enhanced antitumor efficacy

BACKGROUND

Selectively replicating herpes simplex virus-2 (HSV-2) vector is a promising treatment for cancer therapy. The insertion of multiple transgenes into the viral genome has been performed to improve its oncolytic activity.

METHODS

Herein, we simultaneously constructed five "armed" oncolytic viruses (OVs), designated oHSV2-IL12, -IL15, GM-CSF, -PD1v, and IL7 × CCL19. These OVs delete the ICP34.5 and ICP47 genes with the insertion of transgenes into the deleted ICP34.5 locus. The anti-tumor efficacy in vivo was tested in the syngeneic 4T1 and CT26 tumor-bearing mice model.

RESULTS

The OVs showed comparable oncolytic capability in vitro. The combination therapy of oHSV2-IL12, -IL15, GM-CSF, -PD1v, and IL7 × CCL19 exhibited the highest tumor inhibition efficacy compared with the treatment of single OV or two OVs combination.

CONCLUSIONS

The OVs armed with different transgenes combination therapy also named 5-valent oHSV2 (also called cocktail therapy) might be an effective therapeutic strategy for solid tumors.

[Effects of a novel polyamine metabolic enzyme inhibitor SI-4650 on proliferation of colon cancer CT-26 cells and its mechanism]

OBJECTIVE

To investigate the effects of a novel polyamine metabolism enzyme inhibitor SI-4650 on autophagy and apoptosis of colon cancer CT-26 cells as well as their correlation.

METHODS

CT-26 cells treated with 40, 80 μmol·L^-1 SI-4650 alone or in combination with 3-MA were used as experimental group. CT-26 cells treated with 0 μmol·L^-1 SI-4650 alone or in combination with 3-MA were used as control group. Chemiluminescence was used to analyze the effect of SI-4650 on spermine oxidase (SMO) and acetylpolyamine oxidase(APAO) activity. High performance liquid chromatography (HPLC) was performed to detect cellular polyamine content.The CCK8 method was used to detect the inhibitory effect of SI-4650 on proliferation of CT-26 cells. PI single-staining/flow cytometry (FCM) were used to analyze cell cycle. Western blot were used to analyze autophagy. Apoptosis was analyzed by PI/FITC-Annexin V double staining, JC-1 fluorescent probe and Fluo-3 AM calcium ion fluorescent probe combined with flow cytometry and Western blot.

RESULTS

CCK8 assay showed that 24-,48-,72-hours treated with SI-4650 all could inhibit the proliferative activity of CT-26 cells in a dose- and time-dependent manner (P＜0.01) . The inhibition rate was 36.98% and 46.91% in 40 μmol·L^-1 SI-4650 group and 80 μmol·L^-1 SI-4650 group respectively. SI-4650 could significantly inhibit the activities of SMO and APAO interfere with polyamine metabolism and reduce the content of total polyamine in CT-26 cells (P＜0.01). SI-4650 could block CT-26 cells in G0/G1 phase, significantly reduce the number of cells in S phase(P＜0.01), and lead to a significant increase in the contents of autophagy-related Beclin-1, LC3-II in CT-26 cells(P＜0.01); At the same time, the concentration of calcium in CT-26 cells was increased, the mitochondrial membrane potential was decreased, the expressions of c-PARP and Bax were increased, the content of Bcl-2 was decreased, and the number of apoptotic cells was increased. After SI-4650 combined with autophagy inhibitor 3-MA treatment of CT-26 cells, the level of autophagy, the apoptosis-related protein, mitochondrial membrane potential and calcium ion concentration were decreased, and the number of apoptotic cells was decreased.

CONCLUSION

SI-4650 has the pharmacological activity of killing colon cancer CT-26 cells, and its mechanism may be related to the interference of polyamine metabolism and induction of cell apoptosis and autophagy. In this process, autophagy is inhibited to block apoptosis, autophagy and apoptosis combined to kill tumor cells.

Granzyme B PET Imaging of Immune Checkpoint Inhibitor Combinations in Colon Cancer Phenotypes

PURPOSE

Immune checkpoint inhibitor (ICI) monotherapy and combination regimens are being actively pursued as strategies to improve durable response rates in cancer patients. However, the biology surrounding combination therapies is not well understood and may increase the likelihood of immune-mediated adverse events. Accurate stratification of ICI response by non-invasive PET imaging may help ensure safe therapy management across a wide number of cancer phenotypes.

PROCEDURES

We have assessed the ability of a fluorine-labelled peptide, [18F]AlF-mNOTA-GZP, targeting granzyme B, to stratify ICI response in two syngeneic models of colon cancer, CT26 and MC38. In vivo tumour uptake of [18F]AlF-mNOTA-GZP following ICI monotherapy, or in combination with PD-1 was characterised and correlated with changes in tumour-associated immune cell populations.

RESULTS

[18F]AlF-mNOTA-GZP showed good predictive ability and correlated well with changes in tumour-associated T cells, especially CD8+ T cells; however, overall uptake and response to monotherapy or combination therapies was very different in the CT26 and MC38 tumours, likely due to the immunostimulatory environment imbued by the MSI-high phenotype in MC38 tumours.

CONCLUSIONS

[18F]AlF-mNOTA-GZP uptake correlates well with changes in CD8+ T cell populations and is able to stratify tumour response to a range of ICIs administered as monotherapies or in combination. However, tracer uptake can be significantly affected by preexisting phenotypic abnormalities potentially confusing data interpretation.

Blockade of CTLA-4 increases anti-tumor response inducing potential of dendritic cell vaccine

The immunosuppressive state of the tumor microenvironment diminishes the efficacy of dendritic cell (DC)-based cancer immunotherapy. Inhibitory immune checkpoint molecules expressed on tumor-infiltrating T lymphocytes, such as cytotoxic T-lymphocyte antigen 4 (CTLA-4) molecules are one of the main barriers in priming T cells by DCs. Therefore, it seems that blockade of such molecules facilitates the T cells activation by the DC vaccine. In this study, we intended to suppress the expression of CTLA-4 molecule on tumor-infiltrating T cells by siRNA-loaded chitosan-lactate (CL) nanoparticles to facilitate priming anti- tumor T cells by tumor lysate-loaded DC vaccine. Nanoparticles (NPs) have also provided an opportunity for specific drug delivery into the tumor site. CL NPs exhibited favorable physicochemical characteristics (size about 75 nm, polydispersive index<0.2, and a zeta potential about 14), which were associated with a high transfection rate and low toxicity. Moreover, the administration of anti-CTLA-4 siRNA-loaded NPs into CT26 and 4 T1 tumor -bearing mice led to the downregulation of CTLA-4 on tumor -infiltrating T cells, which was associated with tumor regression and increased mice survival. Moreover, while the treatment of tumor -bearing mice with DC vaccine had mild therapeutic outcomes, its combination with siRNA-loaded NPs may exhibit synergistic anti- tumor effects. This possible synergistic ameliorating effect is achieved through the reduction of immunosuppressive cells, the improved cytotoxicity of T lymphocytes, decreased inhibitory and increased inflammatory cytokines, and reduced angiogenesis and metastasis processes. These results indicate that the silencing of CTLA-4 can potentiate the T cell priming capacity of the DC vaccine, proposing a practical anti-cancer therapeutic approach.

IL-33 reduces tumor growth in models of colorectal cancer with the help of eosinophils

In many types of cancer, presence of eosinophils in tumors correlate with an improved disease outcome. In line with this, activated eosinophils have been shown to reduce tumor growth in colorectal cancer (CRC). Interleukin (IL)-33 has recently emerged as a cytokine that is able to inhibit the development of tumors through eosinophils and other cells of the tumor microenvironment thereby positively influencing disease progress. Here, we asked whether eosinophils are involved in the effects of IL-33 on tumor growth in CRC.

In models of CT26 cell engraftment and colitis-associated CRC, tumor growth was reduced after IL-33 treatment. The growth reduction was absent in eosinophil-deficient ΔdblGATA-1 mice but was restored by adoptive transfer of ex vivo-activated eosinophils indicating that the antitumor effect of IL-33 depends on the presence of eosinophils. In vitro, IL-33 increased the expression of markers of activation and homing in eosinophils, such as CD11b and Siglec-F, and the degranulation markers CD63 and CD107a. Increased expression of Siglec-F, CD11b and CD107a was also seen in vivo in eosinophils after IL-33 treatment. Viability and cytotoxic potential of eosinophils and their migration properties toward CCL24 were enhanced indicating direct effects of IL-33 on eosinophils. IL-33 treatment led to increased levels of IL-5 and CCL24 in tumors.

Our data show that the presence of eosinophils is mandatory for IL-33-induced tumor reduction in models of CRC and that the mechanisms include eosinophil recruitment, activation and degranulation. Our findings also emphasize the potential use of IL-33 as an adjuvants in CRC immunotherapy.

Abbreviations

AOM: azoxymethane; bmRPMI: bone marrow RPMI; CRC: colorectal cancer; CFSE: carboxyfluorescein succinimidyl ester; DSS: dextran sulfate sodium; EPX: eosinophil peroxidase; INF-γ: interferon gamma; ILC: innate lymphoid cell; IL-33: interleukin-33; IL-5: interleukin-5; MDSC: myeloid derived suppressor cells; NK cells: natural killer cells; P/S: penicillin/streptomycin; rm: recombinant mouse; T regs: regulatory T cells; TATE: tumor associated tissue eosinophilia; TNF-α: tumor necrosis factor alpha

Development of Tumor Cell-Based Vaccine with IL-12 Gene Electrotransfer as Adjuvant

Tumor cell-based vaccines use tumor cells as a source of tumor-associated antigens. In our study, we aimed to develop and test a tumor vaccine composed of tumor cells killed by irradiation combined with in vivo interleukin-12 gene electrotransfer as an adjuvant. Vaccination was performed in the skin of B16-F10 malignant melanoma or CT26 colorectal carcinoma tumor-bearing mice, distant from the tumor site and combined with concurrent tumor irradiation. Vaccination was also performed before tumor inoculation in both tumor models and tumor outgrowth was followed. The antitumor efficacy of vaccination in combination with tumor irradiation or preventative vaccination varied between the tumor models. A synergistic effect between vaccination and irradiation was observed in the B16-F10, but not in the CT26 tumor model. In contrast, up to 56% of mice were protected from tumor outgrowth in the CT26 tumor model and none were protected in the B16-F10 tumor model. The results suggest a greater contribution of the therapeutic vaccination to tumor irradiation in a less immunogenic B16-F10 tumor model, in contrast to preventative vaccination, which has shown greater efficacy in a more immunogenic CT26 tumor model. Upon further optimization of the vaccination and irradiation regimen, our vaccine could present an alternative tumor cell-based vaccine.

Discovery of low-molecular weight anti-PD-L1 peptides for cancer immunotherapy

Background

Immunotherapy using checkpoint inhibitors, especially PD-1/PD-L1 inhibitors, has now evolved into the most promising therapy for cancer patients. However, most of these inhibitors are monoclonal antibodies, and their large size may limit their tumor penetration, leading to suboptimal efficacy. As a result, there has been a growing interest in developing low-molecular-weight checkpoint inhibitors.

Methods

We developed a novel biopanning strategy to discover small peptide-based anti-PD-L1 inhibitors. The affinity and specificity of the peptides to PD-L1 were examined using various assays. Three-dimensional (3D) spheroid penetration study was performed to determine the tumor penetration capability of the peptides. Anti-tumor activity of the peptides was evaluated in mice bearing CT26 tumor cells.

Results

We discover several anti-PD-L1 peptide inhibitors to block PD-1/PD-L1 interaction. The peptides exhibit high affinity and specificity to human PD-L1 protein as well as PD-L1-overexpressing human cancer cells MDA-MB-231 and DU-145. Molecular docking studies indicate that the peptide CLP002 specifically binds to PD-L1 at the residues where PD-L1 interacts with PD-1. The peptide also blocks the CD80/PD-L1 interaction, which may further enhance the immune response of tumor-infiltrating T cells. Compared to antibody, the peptide CLP002 exhibits better tumor penetration in a 3D tumor spheroid model. The peptide CLP002 restores proliferation and prevents apoptosis of T cells that are co-cultured with cancer cells. The peptide CLP002 also inhibits tumor growth and increases survival of CT26 tumor-bearing mice.

Conclusions

This study demonstrated the feasibility of using phage display to discover small peptide-based checkpoint inhibitors. Our results also suggested that the anti-PD-L1 peptide represents a promising low-molecular-weight checkpoint inhibitor for cancer immunotherapy.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0705-y) contains supplementary material, which is available to authorized users.

Adenovirus and Oxaliplatin cooperate as agnostic sensitizers for immunogenic cell death in colorectal carcinoma

Treatments with cytotoxic agents or viruses may cause Immunogenic Cell Death (ICD) that immunize tumor-bearing hosts but do not cause complete regression of tumor. We postulate that combining two ICD inducers may cause durable regression in immunocompetent mice. ICD was optimized in vitro by maximizing calreticulin externalization in human colorectal carcinoma (CRC) cells by exposure to mixtures of Oxaliplatin (OX) and human adenovirus (AdV). Six mm diameter CT26 or 4T1 carcinomas in flanks of BALB/c mice were injected once intratumorally (IT) with OX, AdV or their mixture. Tumor growth, Tumor-Infiltrating Lymphocytes (TIL), nodal cytotoxicity, and rejection of a viable cell challenge were measured. Tumors injected IT once with an optimum mixture of 80 µM OX - AdV 25 Multiplicity of Infection (MOI) in PBS buffer were 17-29% the volume of control tumors. When buffer was changed from PBS to 5% dextrose in water (D5W), volumes of tumors injected IT with 80 µM OX-AdV 25 MOI were 10% while IT OX or AdV alone were 32% and 40% the volume of IT buffer-treated tumors. OX-AdV IT increased CD3+ TIL by 4-fold, decreased CD8+ PD-1+ TIL from 79% to 19% and induced cytotoxicity to CT26 cells in draining node lymphocytes while lymphocytes from CT26-bearing untreated mice were not cytotoxic. OX-AdV IT in D5W caused complete regression in 40% of mice. Long-term survivors rejected a contralateral challenge of CT26. The buffer for Oxaliplatin is critical. The two ICD inducer mixture is promising as an agnostic sensitizer for carcinomas like colorectal carcinoma.

Silencing PARG decreases invasion in CT26 cells

In this study we investigated the effect of poly (ADP-ribose) glycohydrolase (PARG) deficiency on the ability of invasion in CT26 murine colon carcinoma cell and its possible mechanism. We examined the effects of PARG protein knockdown by RNA interference on invasion, migration, and matrix adhesion of colon carcinoma CT26 cell line in vitro and using a murine model of liver metastasis in vivo to observe the average survival time. The expression of integrin-β1, matrix metalloproteinases-9 (MMP-9) and matrix metalloproteinases-2 (MMP-2) was detected by western blot. The activities of MMP-9 and MMP-2 in various group supernatants were measured by zymography. We observed that PARG silencing caused a significant decrease in the number of CT26 cells that adhered to fibronectin (P < 0.5) and invaded to the lower surface of the membrane (P < 0.5). The expression of integrin-β1, MMP-9, and matrix MMP-2 in CT26 cells of the PARG-shRNA group was lower than that of two control groups (P < 0.5). Similar results were observed in the activities of MMP-9 and MMP-2 in various group supernatants (P < 0.5). The average survival time of BALB/c mice with spleen-transplanted PARG-shRNA CT26 tumors was longer compared with control groups (P < 0.05). To conclude, PARG silencing can inhibit the adhesive and invasive abilities of CT26 cells and delay liver metastasis in a mouse model, which might be useful for therapeutic purposes in CRC patients with distant metastasis.

Apoptotic effect of enterodiol, the final metabolite of edible lignans, in colorectal cancer cells

BACKGROUND

Enterodiol (END) is transformed by human intestinal bacteria from lignans contained in various whole-grain cereals, nuts, legumes, flaxseed, and vegetables. It is known to have several physiological effects, but its effects on mitogen-activated protein kinase (MAPK) signaling and apoptosis in colorectal cancer (CRC) cells have not yet been elucidated. We therefore investigated the effects of END on apoptosis in CRC cells and whether these effects are mediated via MAPK signaling.

RESULTS

Cell proliferation was decreased by END treatment in a time-dependent manner. In particular, END treatment resulted in an apoptosis rate of up to 40% in CT26 cells but showed no cytotoxicity toward RAW264.7 macrophages. Treatment with END also suppressed the migration of CRC cells in a concentration-dependent manner. The phosphorylation of extracellular signal-regulated kinase (ERK), jun N-terminal kinase (JNK), and p38 was down-regulated with END treatment. Furthermore, END decreased the expression levels of anti-apoptotic proteins in CRC cells.

CONCLUSION

Enterodiol inhibited the growth of CRC cells by controlling the MAPK signaling pathway involved in proliferation and apoptosis. These results demonstrate that END has an apoptotic effect in CRC cells. © 2018 Society of Chemical Industry.

Enhancing Checkpoint Inhibitor Therapy with Ultrasound Stimulated Microbubbles

Checkpoint inhibitor (CI) immunotherapy is playing an increasingly prominent role in the treatment of cancer but is effective and durable in only a subset of patients. There are concerted efforts to improve CI therapy through the use of multiple CIs or use of CIs in combination with other anti-cancer agents. Here we investigate the use of "anti-vascular" ultrasound-stimulated microbubble (USMB) treatments in combination with anti-PD-1 CI therapy. The colorectal cancer cell line CT26 was used to conduct longitudinal growth studies along with acute experiments to assess ultrasound-induced anti-tumor immune responses using flow cytometry and enzyme-linked immunospot (ELISPOT) analysis. Longitudinal experiments indicated that USMB + anti-PD-1 treatments significantly enhanced tumor growth inhibition and animal survival relative to monotherapies. Flow cytometry and ELISPOT data did not clearly support a T cell-dependent mechanism for the enhancement. Therefore, the results indicate the ability of anti-vascular USMBs to increase the anti-tumor effects of CI therapy; the specific mechanisms of enhancement remain to be established.

Antitumor Effects of Umbelliprenin in a Mouse Model of Colorectal Cancer

Umbelliprenin is a sesquiterpene coumarin with vitro anti-carcinogenic activities. The aim of this study was to investigate the antitumor effects of umbelliprenin in animal models of colorectal cancer. The cytotoxic effects of umbelliprenin were explored on CT26 and L929by MTT assay. In this study, colorectal tumors developed in mice by intradermal injection of CT26 cell line. Tumor size, serum levels of IFN-γ and IL-4 by ELISA, and Ki-67, MMP2, MMP9, VEGF and E-cadherin markers by IHC method were evaluated. The results showed that umbelliprenin inhibited the cancer cells in a concentration-dependent manner. IC50 Evaluation showed that L929 cells were more resistant to Umbelliprenin than CT26 cells. Umbelliprenin treatment in both tumor-bearing mice and control normal mice showed significantly increased IFN-γ and decreased IL-4(P < 0.05). The pathologic findings had shown that the E-cadherin marker in the umbelliprenin treated cancerous mice were significantly higher compared to the control group (P < 0.05) while the expression of Ki-67 marker was reduced significantly (P < 0.05). Markers involved in angiogenesis including VEGF, MMP2, and MMP-9 in the cancerous mice group treated with umbelliprenin showed a significant decrease compared to the control group (P < 0.05). Metastasis to lung and liver was reduced in umbelliprenin treated group. Our results showed that umbelliprenin inhibited CT26 tumor cells in-vitro. The in-vivo reduction of tumor size, angiogenesis, and proliferation markers and the absence of metastasis represents the antitumor effects of umbelliprenin on colorectal cancer. The results showed that umbelliprenin can be considered as a good candidate for the treatment of colorectal cancer.

Vascular endothelial growth receptor 1 acts as a stress-associated protein in the therapeutic response to thalidomide

Thalidomide (THD) exhibits antitumor effects in several types of cancer. However, the failure of THD to inhibit tumor growth has also been observed in a number of murine models in vivo. The mechanism involved in the therapeutic failure of THD remains unclear. The present study demonstrated that, accompanied by growth-arresting and apoptosis-inducing effects (P<0.05), THD upregulated vascular endothelial growth factor receptor 1 (VEGFR1) expression levels in CT26 murine colorectal carcinoma cell lines. This in vitro phenomenon was also observed in various other cell lines, including human umbilical vein endothelial cells, SW480, SW620 and HCT116. Reactive oxygen species (ROS) levels were increased compared with those in the untreated control when cells were exposed to THD (P<0.05). Furthermore, results suggested that ROS suppression may have provoked the induction of VEGFR1 expression to some extent. In addition, the results revealed that THD failed to inhibit CT26 tumor growth in vivo and the expression of VEGFR1 protein was elevated by THD treatment compared with the control group in the murine colorectal tumor model (P<0.05). The results of further experiments suggested that VEGFR1 was elevated in response to various stress-associated situations, including chemotherapy, radiotherapy and thermotherapy, which indicate that it may act as a stress-associated protein. The present findings provide a foundation for the future study of VEGFR1-targeted therapy to enhance the efficacy of current therapies.

Interleukin-21 combined with PD-1 or CTLA-4 blockade enhances antitumor immunity in mouse tumor models

Recent advances in cancer treatment with checkpoint blockade of receptors such as CTLA-4 and PD-1 have demonstrated that combinations of agents with complementary immunomodulatory effects have the potential to enhance antitumor activity as compared to single agents. We investigated the efficacy of immune-modulatory interleukin-21 (IL-21) combined with checkpoint blockade in several syngeneic mouse tumor models. After tumor establishment, mice were administered recombinant mouse IL-21 (mIL-21) alone or in combination with blocking monoclonal antibodies against mouse PD-1 or CTLA-4. In contrast to monotherapy, IL-21 enhanced antitumor activity of mCTLA-4 mAb in four models and anti-PD-1 mAb in two models, with evidence of synergy for one or both of the combination treatments in the EMT-6 and MC38 models. The enhanced efficacy was associated with increased intratumoral CD8+ T cell infiltrates, CD8+ T cell proliferation, and increased effector memory T cells, along with decreased frequency of central memory CD8+ T cells. In vivo depletion of CD8+ T cells abolished the antitumor activities observed for both combination and monotherapy treatments, further supporting a beneficial role for CD8+ T cells. In all studies, the combination therapies were well tolerated. These results support the hypothesis that the combination of recombinant human IL-21 with CTLA-4 or PD-1 monoclonal antibodies could lead to improved outcomes in cancer patients.

Changes in the spectral index of skin-surface laser Doppler signals of nude mice following the injection of CT26 tumor cells

This study investigated microcirculatory-blood-flow responses in nude mice following the injection of CT26 tumor cells by analyzing the frequency content of skin blood-flow signals recorded on the skin surface. CT26 cells were injected subcutaneously (10^4/100 μl) into the right back flank of each 7-week-old mouse. Three-minute laser Doppler flowmetry (LDF) signals were measured in 60 nude mice. The data sequences were obtained at 1, 2, and 3 weeks after injecting CT26 cells. Mouse tissue samples were cut into sections and examined microscopically to determine the condition of cancer metastasis. Spectral analysis performed after 1 week revealed a significant decrease in the relative energy contribution of the endothelium-related frequency band, and significant increases in those of the myogenic and respiration-related frequency bands of the LDF signals in the metastasis group (n=12). To the best of our knowledge, this is the first study demonstrating the feasibility of evaluating metastasis in animal subjects based on changes in noninvasively measured LDF parameters. Changes in the LDF spectral indexes can be attributed to differences in the microcirculatory regulatory activities. The present measurements performed on the skin surface provide a noninvasive and real-time method for evaluating the microcirculatory responses induced by implanting CT26 tumor cells.

Perioperative treatment with the new synthetic TLR-4 agonist GLA-SE reduces cancer metastasis without adverse effects

The use of TLR agonists as an anti-cancer treatment is gaining momentum given their capacity to activate various host cellular responses through the secretion of inflammatory cytokines and type-I interferons. It is now also recognized that the perioperative period is a window of opportunity for various interventions aiming at reducing the risk of cancer metastases-the major cause of cancer related death. However, immune-stimulatory approach has not been used perioperatively given several contraindications to surgery. To overcome these obstacles, in this study, we used the newly introduced, fully synthetic TLR-4 agonist, Glucopyranosyl Lipid-A (GLA-SE), in various models of cancer metastases, and in the context of acute stress or surgery. Without exerting evident adverse effects, a single systemic administration of GLA-SE rapidly and dose dependently elevated both innate and adaptive immunity in the circulation, lungs and the lymphatic system. Importantly, GLA-SE treatment led to reduced metastatic development of a mammary adenocarcinoma and a colon carcinoma by approximately 40-75% in F344 rats and BALB/c mice, respectively, at least partly through elevating marginating-pulmonary NK cell cytotoxicity. GLA-SE is safe and well tolerated in humans, and currently is used as an adjuvant in phase-II clinical trials. Given that the TLR-4 receptor and its signaling cascade is highly conserved throughout evolution, our current results suggest that GLA-SE may be a promising immune stimulatory agent in the context of oncological surgeries, aiming to reduce long-term cancer recurrence.

Etoposide sensitizes CT26 colorectal adenocarcinoma to radiation therapy in BALB/c mice

AIM: To investigate the combined effect of etoposide and radiation on CT26 colorectal adenocarcinoma implanted into BALB/c mice.

METHODS: We evaluated the radiosensitizing effect of etoposide on CT26 colorectal adenocarcinoma in a syngeneic animal model. BALB/c mice were subcutaneously implanted with CT26 cells and divided into four groups: control (intra-peritoneal saline2) group, etoposide (5 mg/kg intra-peritoneally2) group, radiation therapy (RT 5 Gy2 fractions) group, and combination therapy with etoposide (5 mg/kg intra-peritoneally 1 h before radiation) group.

RESULTS: Tumor growth was significantly inhibited by RT and combination therapy. The effect of combination therapy was better than that of RT. No significant changes were noted in body weight, plasma alanine aminotransferase, or creatinine in any group. The leukocyte count significantly but transiently decreased in the RT and combination therapy groups, but not in the etoposide and control groups. There was no skin change or hair loss in the RT and combination therapy groups.

CONCLUSION: Etoposide can sensitize CT26 colorectal adenocarcinoma in BALB/c mice to RT without significant toxicity.