Malignant pleural mesothelioma (MPM) has limited treatment options and poor prognosis. Frequent inactivation of the tumour suppressors BAP1, NF2 and P16 may differentially sensitise tumours to treatments. We have established chick chorioallantoic membrane (CAM) xenograft models of low-passage MPM cell lines and protocols for evaluating drug responses. Ten cell lines, representing the spectrum of histological subtypes and tumour suppressor status, were dual labelled for fluorescence/bioluminescence imaging and implanted on the CAM at E7. Bioluminescence was used to assess viability of primary tumours, which were excised at E14 for immunohistological staining or real-time PCR. All MPM cell lines engrafted efficiently forming vascularised nodules, however their size, morphology and interaction with chick cells varied. MPM phenotypes including local invasion, fibroblast recruitment, tumour angiogenesis and vascular remodelling were evident. Bioluminescence imaging could be used to reliably estimate tumour burden pre- and post-treatment, correlating with tumour weight and Ki-67 staining. In conclusion, MPM-CAM models recapitulate important features of the disease and are suitable to assess therapies using a broad range of MPM cell lines that allow histological or genetic stratification. They are amenable to multi-modal imaging, offering a time and cost-efficient, 3Rs-compliant alternative to rodent xenograft models to prioritise candidate compounds from in vitro studies.

Despite the recent advances in melanoma therapy, the need for new targets and novel approaches to therapy is urgent. We previously reported melanoma actives that work via binding and downregulating spliceosomal proteins hnRNPH1 and H2. In a separate study, we reported that these compounds were non-toxic to Balb/C mice at 50 mg/kg suggesting their utility in in vivo studies. In the present study, we aimed to determine the therapeutic potential of these compounds by testing them in A375 cell-line derived xenograft in nu/nu mice. Animals were randomized into four groups (n=12/group) to receive subcutaneous administration of vehicle, 10 mg/kg vemurafenib, and 25 mg/kg 2155-14 and 2155-18 three times per week for 15 days along with a control group. The results revealed that both 2155-14 and 2155-18 significantly decreased the growth of A375 tumors, which was comparable to vemurafenib. These results were confirmed by tumor volume, weight, and histopathological examination. In conclusion, these results suggest a therapeutic potential of targeting spliceosomal proteins hnRNPH1 and H2.

Patient-derived xenograft (PDX) models are created by engraftment of patients’ tumor tissues into immunocompetent mice. Since PDX model keep the characteristics of primary patient’s tumor such as gene expression profiles and drug sensitivity, it now becomes most reliable in vivo human cancer model. The engraftment rate are increased with the introduction of NOD/Scid based immunocompromised mice, especially, NK cell defective NOD strains such as NOD/Scid/IL2Rγnu (NOG/ NSG) mice and NOD/Scid/Jak3null (NOJ) mice. Success ratio differs from the origin of tumor: Gastrointestinal tumors tend to higher success rate and breast cancer is lower. Subcutaneous transplantation is most popular method to establish PDX, but some tumor needs orthotropic or renal capsule transplantation, and human hormone treatment is needed to establish hormone dependent cancers such as prostate and breast cancer. PDX library with patient’s clinical data, gene-expression patterns, mutational status, drug responsiveness and tumor architecture will be the powerful tool for developing specific biomarker and novel individualized therapy and establishing precision cancer medicine.

In order to overcome the disadvantages of existing treatments in heart valve tissue engineering, decellularization studies are carried out. The main purpose of decellularization is to eliminate the immunogenicity of biologically derived grafts and to obtain a scaffold that allows recellularization while preserving the natural tissue architecture. SD and SDS are detergent derivatives frequently used in decellularization studies. The aim of our study is to decellularize the pulmonary heart valves of young Merino sheep by using low-density SDS and SD detergents together, and then to perform their detailed characterization to determine whether they are suitable for clinical studies. Pulmonary heart valves of 4-6 month old sheep were decellularized in detergent solution for 24 hours. The amount of residual DNA was measured to determine the efficiency of decellularization. Then, the effect of decellularization on the ECM by histological staining was examined. In addition, the samples were visualized by SEM to determine the surface morphologies of the scaffolds. Uniaxial tensile test was performed to examine the effect of decellularization on biomechanical properties. The results showed DNA removal of 94% and 98% from the decellularized leaflet and artery portions after decellularization relative to the control group. No cell nuclei were found in histological staining and it was observed that the 3-layer leaflet structure was preserved. As a result of the tensile test, it was determined that there was no statistically significant difference between the control and decellularized groups in the UTS and elasticity modulus, and the biomechanical properties did not change. In conclusion, we suggest that the pulmonary valves of decellularized young Merino sheep can be used as a initial matrix in heart valve tissue engineering studies.

Glioblastoma (GBM) is a major type of primary brain tumors without ideal prognosis and it’s necessary to find novel compound possessing therapeutic effect. Chrysomycin A (Chr-A) has been reported to inhibit the proliferation, migration and invasion of U251 and U87-MG cells, but the mechanism of Chr-A against glioblastoma in vivo and whether Chr-A modulates apoptosis of neuroglioma cells is unclear.The present study was to elucidate the potential of Chr-A against glioblastoma in vivo and how Chr-A modulates apoptosis of neuroglioma cells. Briefly, The an-ti-glioblastoma activity was assessed in human glioma U87 xenografts nude mice. Chr-A-related targets were identified by RNA-seq. Apoptotic ratio and caspase 3/7 activity of U251 and U87-MG cells were assayed by flow cytometry. Apoptosis-related proteins and possible molecular mecha-nism were validated via Western blotting. The results showed that Chr-A treatment significantly inhibits glioblastoma progression in xenografts nude mice, and enrichment analysis suggested that apoptosis, PI3K-Akt and Wnt signaling pathway were involved in the possible mechanism. Chr-A increased apoptotic ratio and the activity of caspase 3/7 in U251 and U87-MG cells. Western blot revealed that Chr-A broke the balance between Bax and Bcl-2 activating caspase cascade re-action and downregulated the expression of p-Akt and p-GSK-3β, suggesting that Chr-A may contribute to glioblastoma regression modulating Akt/GSK-3β signaling pathway to promote apoptosis of neuroglioma cells in vivo and in vitro. Therefore, Chr-A may hold therapeutic promise for glioblastoma.

Cisplatin (CDDP) is widely used to treat several types of cancer. However, CDDP induces nephrotoxicity. This toxicity could be avoided, applying a lower cisplatin dose; however, it could induce a lesser therapeutic activity. In this paper, we present the cytotoxic activity against prostate human cancer cell line (PC-3) of the combination of CDDP with masticadienonic acid (MDA), a triterpene isolated from Amphypterygium adstringens.The combinations A (half of the IC₅₀), B (IC₅₀) and C (twice IC₅₀ of the compounds) in a radio 1:1 were evaluated. Our results showed that the B and C combinations presented synergism effect. However, B combination showed almost 100% inhibition of cell proliferative activity and increased apoptosis compared with those presented by each compound apart. A pretreatment of MDA 24 h to cells before the CDDP, AMD or B combination administration result in a resistance to the treatments. A xenograft study using PC-3 cells showed that the combination of 47.5 mM/kg (AMD) plus 4 mM/kg (CDDP) administered weekly for 3 weeks reducing the tumor volume in approximately 47 %. However, the combination of 47.5 mg/kg (AMD) plus 2 mg/kg (CDDP) administered every third day for 21 days reduce, approximately 82% of tumor compared with mice no treated.

Multimodal therapy including surgery, radiation treatment and temozolomide (TMZ) is performed on glioblastoma (GBM). However, the prognosis is still poor and there is an urgent need to develop effective treatments to improve survival. Molecular biological analysis was conducted to exam-ine the signal activation patterns at GBM specimens and remains an open problem. Advanced macrolides, such as azithromycin, reduce the phosphorylation of p70 ribosomal protein S6 kinase (p70S6K), a downstream mammalian target of rapamycin (mTOR) effector, and suppress the proliferation of T-cells. We focused on its unique profile and screened for the antitumor activity of approved macrolide antibiotics. Clindamycin (CLD) reduced the viability of GBM cells in vitro. We assessed the effects of the candidate macrolide on the mTOR pathway through Western blotting. CLD attenuated p70S6K phosphorylation in a dose dependent manner. These effects of on GBM cells were enhanced by co-treatment with TMZ. Furthermore, CLD inhibited the expression of O6-methylguanine-DNA methyltransferase (MGMT) protein in cultured cells. In the mouse xenograft model, CLD and TMZ co-administration significantly suppressed the tumor growth and markedly decreased the number of Ki-67 (clone MIB-1) positive cells within the tumor. These results suggest that CLD suppresses GBM cell growth by the inhibiting mTOR signaling. Moreover, CLD and TMZ showed promising synergistic antitumor activity.

There is a need for versatile in vivo nuclear imaging reporter systems to foster preclinical and clinical research. We explore the applicability of the SNAPTag and novel radiolabeled small-molecule ligands as a versatile reporter gene system for in vivo nuclear imaging. SNAPTag is a high-affinity protein tag used in a variety of biochemical research areas and based on the suicide DNA repair enzyme O6-methylguanine methyl transferase (MGMT). Its ligands are well suited for reporter gene imaging as the benzyl guanine core scaffold can be derivatized with fluorescent or radiolabeled moieties for various applications. Three guanine-based SNAPTag ligands ([18F]FBBG, [18F]pFBG and [18F]mFBG) were synthesized in high yields and were (radio)chemically characterized. HEK293 cells were engineered to express the SNAPTag on the cell surface and served as cell model to assess target affinity by radiotracer uptake assays, Western blotting and SDS-PAGE autoradiography. A subcutaneous HEK293-SNAPTag xenograft model in immunodeficient mice was used for in vivo evaluation of [18F]FBBG amd [18F]pFBG while the biodistribution of [18F]mFBG was characterized in naïve animals. The results were validated by ex vivo biodistribution studies and immunofluorescence staining of the xenografts. All three radiotracers were produced in high radiochemical purity, molar activity and good yields. Western blot analysis revealed successful SNAPTag expression by the transfected HEK293 cells. In vitro testing revealed high target affinity of all three tracers with an up to 191-fold higher signal in the HEK293-SNAPTag cells compared to untransfected cells. This was further supported by a prominent radioactive protein band at the expected size in the SDS-PAGE autoradiograph of cells incubated with [18F]FBBG or [18F]pFBG. The in vivo studies demonstrated high uptake in HEK293-SNAP xenografts compared to HEK293 xenografts with excellent tumor-to-muscle ratios (7.5 ± 4.2 for [18F]FBBG and 10.6 ± 6.2 for [18F]pFBG). In contrast to [18F]pFBG and its chemical analogue [18F]mFBG, [18F]FBBG showed no signs of unspecific bone uptake and defluorination in vivo. Radiolabeled SNAPTag ligands bear great potential for clinical applications such as in vivo tracking of cell populations, antibody fragments and targeted radiotherapy. With excellent target affinity, good stability, and low non-specific binding, [18F]FBBG is a highly promising candidate for further preclinical evaluation.

Though the cancer research community has used mouse xenografts for decades more than zebrafish xenografts, zebrafish have much to offer: they are cheap, easy to work with, and the embryonic model is relatively easy to use in high-throughput assays. Zebrafish can be imaged live, allowing us to observe cellular and molecular processes in vivo in real time. Opponents dismiss the zebrafish model due to the evolutionary distance between zebrafish and humans, as compared to mice, but proponents argue for the zebrafish xenograft’s superiority to cell culture systems and its advantages in imaging. This review places the zebrafish xenograft in the context of current views on cancer and gives an overview of how several aspects of this evolutionary disease can be addressed in the zebrafish model. Zebrafish are missing homologs of some human proteins and (of particular interest) several members of the matrix metalloproteinase (MMP) family of proteases, which are known for their importance in tumour biology. This review draws attention to the implicit evolutionary experiment taking place when the molecular ecology of the xenograft host is significantly different than that of the donor.

Prostate cancer is a common cancer among men and typically progresses slowly for several decades before becoming aggressive and spreading to other organs, leaving few treatment options. While large animals have been studied, the dog's prostate is anatomically similar to humans and has been used to study spontaneous prostate cancer. However, most research currently focuses on the mouse as a model organism due to the ability to genetically modify their prostatic tissues for molecular analysis. One hallmark in this research was the identification of the prostate-specific promoter Probasin, allowing for prostate-specific expression of transgenes. This has led to generations of mice with aggressive prostatic tumors through overexpression of the SV40 oncogene. The Probasin promoter is also used to drive Cre expression and allow researcher to generated prostate specific loss-of-function studies. Another landmark in the process of modeling prostate cancer in mice was orthoptic delivery of viral particles. This technology allows selective overexpression of oncogenes from lentivirus or the use of CRISPR to generate complex loss of function studies. These genetic modified models are complemented by classical xenografts of human prostate tumor cells in immune deficient mice. Overall, pre-clinical models have provided a portfolio of model systems to study and address complex mechanisms in prostate cancer for improved treatment options. This review will focus on the advances of each technique.

We describe the development and validation of a HPLC-MS/MS method to assess the pharmacokinetics and tumour distribution of ZST316, an arginine analogue with inhibitory activity towards dimethylarginine dimethylaminohydrolase 1 (DDAH1) and vasculogenic mimicry, and its active metabolite L-257 in a xenograft model of triple negative breast cancer (TNBC). The method proved to be reproducible, precise, and highly accurate for the measurement of both compounds in plasma and tumour tissue following acute and chronic (five days) intraperitoneal administration of ZST316 (30mg/Kg daily) in six-week-old SCID mice inoculated with MDA-MB-231 TNBC cells. ZST316 was detected in tumour tissue and plasma after 1 hour (6.47 and 9.01M, respectively) and 24 hours (0.13 and 0.16M, respectively) following acute administration, without accumulation during chronic treatment. Similarly, the metabolite L-257 was found in tumour tissue and plasma after 1 hour (15.06 and 8.72M, respectively) and 24 hours (0.17 and 0.17M, respectively) following acute administration of ZST316, without accumulation during chronic treatment. The half-live after acute and chronic treatment ranged between 4.4-7.1hrs (plasma) and 4.5-5.0hrs (tumour) for ZST316, and 4.2-5.3hrs (plasma) and 3.6-4.9hrs (tumour) for L-257. The results of our study demonstrate the a) capacity to accurately measure ZST316 and L-257 concentrations in plasma and tumour tissue in mice using the newly developed HPLC-MS/MS method, b) rapid conversion of ZST316 into L-257, c) good intra-tumour penetration of both compounds, and d) lack of accumulation of both ZST316 and L-257 in plasma and tumour tissue during chronic administration. The new HPLC-MS/MS method is useful to investigate the in vivo effects of ZST316 and L-257 on vasculogenic mimicry, tumour mass, and metastatic burden in xenograft models of TNBC.

Current methodologies for developing patient-derived xenografts (PDX) in humanized mice in preclinical trials to test response to immune-based therapies are limited by graft versus host disease. Here we compared two approaches for establishing PDX tumors in humanized mice: 1) PDX are first established in immune-deficient mice; 2) PDX are initially established in humanized mice, before transplanting established PDX’s to a larger cohort of humanized mice for preclinical trials. With the first approach, there was rapid wasting of PDX-bearing humanized mice with high levels of activated T cells in the circulation and organs, indicating immune-mediated toxicity. In contrast, with the second approach, toxicity was less of an issue and long-term human melanoma tumor growth and maintenance of human chimerism was achieved. Pre-clinical trials from the second approach revealed that rigosertib, but not anti-PD-1, increased CD8/CD4 T cell ratios in spleen and blood and inhibited PDX tumor growth. Resistance to anti-PD-1 was associated with limited infiltration of CD8+ T cell into the tumor. Our findings suggest that it is essential to carefully manage immune editing by first establishing PDX tumors in the presence of human immune cells before expanding PDX tumors into a larger cohort of humanized mice to evaluate therapy response.

The problem of filling the bone cavity remains relevant in maxillofacial and oral surgery. There is a large selection of osteotropic materials of various natures for filling of bone defects of different etiology. The aim of our research was to improve the result of surgical treatment in a patient with a complicated mandibular fracture with the use of collagenic xenograft during osteosynthesis. In this article, we introduce our experience in the treatment of a patient with a complicated mandibular angle fracture in a combination with the follicular cyst. The obligate steps of treatment included stabilization of the bony fragments, a decrease of risk in fracture line malposition along with titan mini- plates, and shortening in the time of bone regeneration due to a filling of bone defect with the osteotropic material. This approach allowed us to reduce the rehabilitation period and further prosthetic treatment after 4-5 months without additional bone grafting manipulations. Though, the use of collagen osteotropic material, possessing osteoconductive properties, can improve the treatment of patients with mandibular fractures.

Cadaver bone is possibly the most common transplant material used today. Common types of cadaver bone transplants are freeze dried bone allografts and xenografts. In the case of freeze dried bone allograft transplants, it was theorized that these materials mineralize by way of osteoinduction and stimulating osteogenesis. However, these theories have been proven false. It has been proposed that these materials mineralize via osteoconduction however, there are no studies to support this hypothesis. This study was undertaken to determine how these transplants mineralize and what type of bone they produce. Materials and Methods: This study is a histological analysis of human cadaver bone graft healing from the incipient stages of mineralization through completed mineralization. All cadaver bone grafts used for evaluation in this study were particulate bone graft materials in the maxilla or mandible. No block grafts were evaluated. Results: The mineralization of cadaver bone transplants was produced by an inflammatory response to the transplanted tissue. The histologic findings of the mineralized bone produced by this process was sclerotic bone. No resorption of cadaver bone graft particles was found. When loaded the sclerotic bone was found to fail through an accumulation of microfractures.Conclusions: Particulate freeze-dried bone allografts and xenografts do not heal via the normal processes of mineralization. Cadaver bone grafts produce significant inflammation and are hypothesized to mineralize by a process termed antigenic ossification. The process of antigenic ossification produces sclerotic bone that is not capable of self-repair which can ultimately lead to bone failure.

Regenerative capacity of well-preserved blood clot may be enhanced by biologics like enamel matrix derivative (EMD). This retrospective analysis compares outcomes reported by three centers using different heterografts. Center 1 (C1) treated intrabony defects combining cross-linked heavy weight hyaluronic acid (xHyA) with a xenograft, Center 2 (C2) used EMD with an allograft combination to graft residual pocket. Center 3 (C3) combined xHyA with placement of resorbable polymer membrane for defect cover. Clinical parameters, BoP reduction and radiographically observed defect fill at 12-months examination are reported. The 12-months evaluation yielded significant improvement in PPD and CAL at each center (p<0.001, respectively). Analyses of Covariance revealed significant improvement of all parameters, significantly greater CAL gain disclosed C2 vs. C1 (p=0.006). Radiographic defect fill presented with significantly higher scores for C2 and C3 vs. C1 (P=.003 and =.014; C2 vs. C3 P=1.00). Gingival recession increased in C1 and C3 (P=1.00), while C2 reported no GR after 12-months (C2:C1 P=.002; C2:C3 P=.005). BoP tendency and pocket closure rate shared similar rates. Within limitations of the study, data comparison indicated that xHyA showed similar capacity to enhance regenerative response, as known for EMD. Radiographic follow-up underlined xHyA staying alone role in new attachment formation.

Tocilizumab against interleukin-6 receptor (IL-6R) has been demonstrated to inhibit the progression of diverse cancers in vitro and in vivo. Nonetheless, evidence regarding the anti-tumor effects of Tocilizumab on human colorectal carcinoma (CRC) corresponding to IL-6R expression levels re-mains scarce. To investigate the influence of IL-6R expression, SW480 and HT-29 cells inoculated subcutaneously into NU/NU mice were used as our human CRC xenograft models with anti-IL-6R antibody (Tocilizumab) therapy. IL-6R expression levels, the histology of CRC growth/ invasiveness and tumor growth-related signaling pathway were estimated by H&E and immunohistochemical staining. SW480 tumor cells with higher IL-6R expression levels exerted better responsiveness in Tocilizumab therapy than the treated HT-29 group. Likewise, therapeutic effects of Tocilizumab on the proliferative ability with mitotic index and Ki-67 expressions, the invasiveness with MMP-9 proteinase expressions, ERK 1/2 and STAT3 signaling transduction in SW480 treatment group were superior to HT-29 treatment group. In light of our results, IL-6R is the key indicator for the efficacy of Tocilizumab treatment in CRC xenografts. From the perspective of precision medicine, tumor response to anti-IL-6R antibody therapy could be predicted on the basis of IL-6R expression levels. In this manner, Tocilizumab may serve as a targeted and promising anti-CRC therapy.

Two monoclonal antibodies (mAbs) against human epidermal growth factor receptor 2 (HER2), trastuzumab and pertuzumab, were clinically approved. We previously developed a highly sensitive and specific anti-HER2 mAb, H2Mab-139 (mouse IgG1, kappa). In this study, we produced a defucosylated IgG2a version of anti‑HER2 mAb (H2Mab-139-mG2a-f) to enhance ADCC-mediated antitumor activity. H2Mab-139-mG2a-f exhibits a high binding affinity in flow cytometry with the dissociation constant (KD) determined to be 3.9 × 10‑9 M and 7.7 × 10‑9 M against HER2‑overexpressed Chinese hamster ovary (CHO)-K1 (CHO/HER2) and HER2-positive BT-474 cells, respectively. Moreover, we showed that H2Mab-139-mG2a-f exerted ADCC and complement-dependent cytotoxicity against CHO/HER2 and BT-474 cells in vitro and exhibited potent antitumor activities in the xenograft models. These results indicated that H2Mab-139-mG2a-f exerts antitumor effects against HER2-positive human breast cancers and could be useful for an antibody treatment regimen for HER2-positive human cancers.

We previously developed a highly sensitive and specific anti-PDPN mAb, LpMab-23 (mouse IgG1, kappa). In this study, we produced a humanized IgG1 version (humLpMab-23) and its defucosylated form (humLpMab-23-f) of an anti‑PDPN mAb to potentiate the ADCC activity. The humLpMab-23 could recognize PDPN‑overexpressed Chinese hamster ovary (CHO)-K1 (CHO/PDPN) and PDPN-positive PC-10 and LN319 cells by flow cytometry. Furthermore, we found that humLpMab-23-f exerted ADCC and complement-dependent cytotoxicity against CHO/PDPN, PC-10 and LN319 cells in vitro and exhibited potent antitumor activities in the xenograft models. These results indicated that humLpMab-23-f could be useful for an antibody treatment regimen for PDPN-positive human cancers.

Gastroenteropancreatic neuroendocrine neoplasms (GEP NENs) are rare cancers consisting of neuroendocrine carcinomas (NECs) and neuroendocrine tumors (NETs), which have been increasing in incidence in recent years. Few cell lines and pre-clinical models exist for the study of GEP NECs and NETs, limiting the ability to discover novel imaging and treatment modalities. To address this gap, we isolated tumor cells from cryopreserved patient GEP NECs and NETs and injected them into the flanks of immunocompromised mice to establish patient-derived xenograft (PDX) models. Two of 6 mice developed tumors (NEC913 and NEC1452). Over 90% of NEC913 and NEC1452 tumor cells stained positive for Ki67. NEC913 PDX tumors expressed neuroendocrine markers such as chromogranin A (CgA), synaptophysin (SYP), and somatostatin receptor-2 (SSTR2) whereas NEC1452 PDX tumors do not express SSTR2. Exome sequencing revealed loss of p53 and RB1 in both tumors. To demonstrate an application of these novel NEC PDX models for SSTR2-targeted peptide imaging, the NEC913 and NEC1452 cells were bilaterally injected into mice. Near infrared-labelled octreotide was administered and fluorescent signal was specifically observed for the NEC913 SSTR2 positive tumors. These 2 GEP NEC PDX models serve as valuable resource for GEP NEN therapy testing.

Ketogenic diet (KD) is getting in the focus as auxiliary cancer therapy, since it provides sufficient energy supply for healthy cells, while impairing energy production in tumor cells underlying the Warburg effect. Thereby, it can assist in inhibiting tumor growth and simultaneously counteract cachexia, which is frequently observed in cancer patients under chemotherapy. In order to provide molecular evidence for the proposed synergistic inhibition of tumor growth, we applied untargeted quantitative metabolome analysis on a breast cancer xenograft mouse model. Healthy mice and such bearing breast cancer xenografts and receiving chemotherapy were compared after treatment with control diet and KD. Metabolomic profiling was performed on plasma samples, applying high-performance liquid chromatography coupled to tandem mass spectrometry. Statistical analysis revealed metabolic fingerprints comprising numerous significantly regulated features in the group of mice bearing breast cancer. This fingerprint disappeared after treatment with KD, resulting in recovery to the metabolic status observed in healthy mice receiving control diet. Moreover, amino acid metabolism as well as fatty acid transport were found to be affected by both, the tumor and the applied KD. Our results provide clear evidence of a significant molecular effect of KD in the context of tumor growth inhibition.

Macrophages and dendritic cells (DCs) acquire functionally distinct properties in response to various environmental stimuli; the interaction of these cells with myeloid-derived suppressor cells (MDSCs) in tumor microenvironments regulates cancer progression. Immunodeficient mice lacking T cells are less likely to reject human cancer cells because of major histocompatibility complex (MHC) mismatches. The xenograft tumor microenvironment, comprising human cancer and mouse host cells, exhibits more complex bidirectional signaling and function than a syngeneic tumor microenvironment. Here human and mouse colorectal cancer cells were transplanted into nude mice to elucidate differences in macrophage, DC, and MDSC functions in human xenograft and mouse allograft tumor models. Plasma interferon-γ and interleukin-18 concentrations in the former model after intraperitoneal lipopolysaccharide (LPS) administration were significantly higher than those in the latter model and non-transplanted control group. Splenic MHC class I, II, and CD80 expression increased in CD11b+ and MDSC populations after LPS administration in only the xenograft tumor model. The number of CD80- and MRC1-expressing cells decreased upon LPS administration in only the xenograft tumor. These results suggxest that macrophages and DCs function normally in xenograft tumor models, whereas their functions in response to LPS administration vary in allograft tumor models.