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Deficiencies in the DNA mismatch repair system (MMR) have been well described in a variety of neoplasms in humans; however, naturally occurring animal models of MMR deficiency associated carcinogenesis are lacking. Recently, our lab has shown that deficiencies in the MMR are common in canine lower urinary tract carcinomas through the identification of microsatellite instability and decreased expression of MSH2. In order to further investigate MMR in the dog, cell lines were derived from canine lower urinary tract carcinomas. Briefly, samples of a prostatic urothelial carcinoma from an 8-year-old neutered male Beagle were minced into 0.5-1mm3 pieces and incubated in culture plates with 1:1 DMEM/F12 supplemented with 10% fetal bovine serum, penicillin, streptomycin, and l-glutamine. Resulting colonies of epithelioid cells were harvested with 0.05% trypsin and subcultured. Two distinct cell populations emerged following repeated subculture, which were subsequently isolated from one another through selective trypinization. Thus, two distinct cell lines, TYLER1 and TYLER2, were established. While these cell lines were derived from the same tumor, they differ greatly in terms of morphology and expression of DNA mismatch repair genes. Cells of TYLER1 are polygonal with regular dimensions, and grow in fairly discrete aggregates. Cells of TYLER2 are spindle-shaped to stellate, and grow in haphazardly arranged interlacing patterns. Both cell lines express cytokeratins confirming their epithelial origin; however, the specific cytokeratins expressed by each line differs and both cell lines strongly express vimentin. In contrast to the primary tumor, both cell lines express prostatic acid phosphatase (PAP), a marker of prostatic differentiation, and neither cell line expresses uroplakin III, an urothelial marker. This is likely a reflection of plasticity of cells of the lower urinary tract in terms of their ability to differentiate. Comparing microsatellite sequences obtained from a blood sample from the dog of origin to those in the cell lines, there is variability in the length of select microsatellites suggesting functional MMR deficiency. The gene and protein expression of MSH2 and MSH6 are significantly lower in TYLER2 than TYLER1 as determined by Western blot and RT PCR, respectively. In preliminary studies using XTT assays, the MMR deficient TYLER2 cell line is more sensitive to gemcitabine and carboplatin than TYLER1, although both are more sensitive to these agents than other canine urothelial carcinoma cell lines that strongly express MSH2 and MSH6. Overall, given the differences in apparent MMR expression and differences observed in morphology and response to treatment, these cell lines will undoubtedly prove valuable in future studies of MMR in dogs and the effects MMR deficiency on cancer treatment response and progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5258. doi:1538-7445.AM2012-5258

Tumor hypoxia substantially impacts the prognosis of cancer patients by impairing the response to therapy and by promoting the acquisition of a malignant cellular phenotype. A variety human tumors exhibit hypoxia including head and neck squamous cell carcinoma (HNSCC) where it is considered a barrier to successful management of these patients. In the feline, HNSCC is a common and aggressive malignancy that shares morphologic, clinical and molecular features with human HNSCC. Therefore, feline HNSCC may serve as an informative model. To date, there are no data concerning the occurrence of hypoxia in feline HNSCC. We hypothesized that like its human counter part, feline HNSCC would demonstrate regions of intratumoral hypoxia and that hypoxia would be a feature of malignant rather than benign oral tumors. To test this hypothesis, cats with spontaneously occurring oral tumors (N=7) were administered 2 mCi 64Cu- diacetyl-bis(N4-methylthiosemicarbazone) (ATSM) IV 20 minutes prior to PET-CT scan (Discovery ST, GE Healthcare). Histologically, 4 cats had invasive squamous cell carcinoma, 1 had osteosarcoma and 2 had inflammatory lesions (1 polyp and 1 granuloma). All four squamous cell carcinomas and both inflammatory lesions demonstrated strong diffuse uptake of 64Cu within the tumor. Two cats with metastases to regional lymph nodes also demonstrated significant 64Cu uptake. Tumor hypoxia was confirmed by fluorescent lifetime probe measurements (Oxylab pO2), Oxford Optronix) in 4 cats and pimonidazole (HypoxyporbeTM-1, Hypoxyprobe Inc) uptake in biopsy samples in 4 cats. These data indicate that HNSCC in the cat exhibits significant, diffuse hypoxia. Hypoxia was also significant in inflammatory lesions and thus was not a marker of malignancy, but could indicate that inflammatory disease may provide a selective microenvironement to promote tumorigenesis in the cat. The feline model may provide an important tool for studying clinical methods to modulate hypoxia and to study the role of hypoxia on oral carcinogenesis. We are currently evaluating the effect of vascular modulating agents on feline HNSCC and intratumoral hypoxia as a means to optimize this therapy for combination with irradiation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 439.