Relationship of microsatellite instability to mismatch repair deficiency in malignant tumors of dogs.

BACKGROUND: Microsatellite instability (MSI) is a type of genomic instability caused by mismatch repair deficiency (dMMR) in tumors. Studies on dMMR/MSI are limited, and the relationship between dMMR and MSI is unknown in tumors of dogs. OBJECTIVES: We aimed to identify the frequency of dMMR/MSI by tumor type and evaluate the relationship between dMMR and MSI in tumors of dogs. ANIMALS: In total, 101 dogs with 11 types of malignant tumors were included. METHODS: We extracted DNA from fresh normal and tumor tissues. Twelve microsatellite loci from both normal and tumor DNA were amplified by PCR and detected by capillary electrophoresis. Each microsatellite (MS) was defined as MSI if a difference in product size between the tumor and normal DNA was detected. The dMMR was evaluated by immunohistochemistry with formalin-fixed paraffin-embedded tumor tissues. Next, we confirmed whether dMMR induces MSI by serial passaging of MMR gene knockout cell lines for 3 months. RESULTS: Microsatellite instability was detected frequently in oral malignant melanoma. The number of MSI-positive markers was higher in cases with dMMR than in those with proficient MMR (P < .0001). Statistical analysis indicated that the occurrence of MSI in FH2305 might have relevance to dMMR. Furthermore, MSI occurred in dMMR cell lines 3 months after passaging. CONCLUSIONS AND CLINICAL IMPORTANCE: Microsatellite instability and dMMR more frequently were found in oral malignant melanoma than in other tumors, and dMMR has relevance to MSI in both clinical cases and cell lines.

Potent adjuvant effect elicited for tumor immunotherapy by a liposome conjugated pH-sensitive polymer and dendritic cell-targeting Toll-like-receptor ligand.

The generation of DCs with augmented functions is a strategy for obtaining satisfactory clinical outcomes in tumor immunotherapy. We developed a novel synthetic adjuvant comprising a liposome conjugated with a DC-targeting Toll-like-receptor ligand and a pH-sensitive polymer for augmenting cross-presentation. In an in vitro study using mouse DCs, these liposomes were selectively incorporated into DCs, significantly enhanced DC function and activated immune responses to present an epitope of the incorporated antigen on the major histocompatibility complex class I molecules. Immunization of mice with liposomes encapsulating a tumor antigen significantly enhanced antigen-specific cytotoxicity. In tumor-bearing mice, vaccination with liposomes encapsulating a tumor antigen elicited complete tumor remission. Furthermore, vaccination significantly enhanced cytotoxicity, targeting not only the vaccinated antigen but also the other antigens of the tumor cell. These results indicate that liposomes are an ideal adjuvant to develop DCs with considerably high potential to elicit antigen-specific immune responses; they are a promising tool for cancer therapy with neoantigen vaccination.

Potential role of SC1, a cell adhesion molecule, in mammary gland tumors.

SC1, an immunoglobulin superfamily cell adhesion molecule, is expressed in embryonic tissues and plays an important role in development through its cell adhesive activity. SC1 is also found in a variety of tumors and its expression is associated with a poor prognosis. The expressional patterns of SC1 were examined in sporadic cases of canine mammary gland tumors and it was found that this molecule is enriched in adenocarcinomas and is weaker in benign mixed tumors. SC1 might therefore be involved in the malignancy and progression of canine mammary gland tumors. To confirm this paradigm, the mammary gland cell line JYG-B was used as the recipient of SC1 cDNA. The resulting SC1-transfected cells were subsequently analyzed using a convenient in vitro model system. The self-aggregation activity of SC1-transfected cells was significantly increased and was blocked by an anti-SC1 antibody generated by hyper-immunized ostrich yolk. In addition, cell locomotion assays revealed an enhanced migration activity of SC1-transfected cells on SC1-coated transwell chambers. The in vivo activities of the cells were examined by subcutaneous implantation into nude mice. Tumor growth was significantly promoted in the mice after implantation with SC1-transfected cells, in comparison to parental- and mock-transfectants. This growth was inhibited by oral administration of gold-ion water. The invasion of SC1-transfectants into the surrounding muscular and adipose tissues was rigorously enhanced. These findings suggest that SC1 might promote the progression of mammary gland tumor cells by increasing cell adhesion.