We previously identified a novel mutant mouse strain on the C3HeB/FeJ background named gene that greatly reduces expression of the encoded protein a nuclear factor implicated in transcriptional regulation. for pancytokeratin (AE1/AE3) and p63. While CK5/6 immunostaining was seen in the much of the tumor cells it was often lacking in pleomorphic areas. Tumor cells lacked immunoreactivity for mice and that LDN193189 HCl these tumors may offer a valuable model for study of EGFR regulation. Combined our data suggest that mice warrant further investigation for use as a mouse model for human salivary gland neoplasia. Salivary gland tumors are histologically one of the most heterogeneous group of tumors as compared to tumors in other areas of the body LDN193189 HCl which presents significant difficulties in both diagnosis LDN193189 HCl and management (1). Although malignant salivary gland tumors are rare representing approximately 3-5% of all head and neck cancers these tumors can be difficult to treat and high-grade tumors are associated with a poor prognosis (2). Efforts to appropriately diagnose and treat salivary gland tumors have been hampered by limited knowledge of molecular biomarkers LDN193189 HCl that can serve as indicators of salivary gland tumorigenesis (3). Additionally there is a lack of mouse models for spontaneous salivary gland tumor development which would be valuable for studying the pathogenesis and treatment of this disease. The most well-known salivary gland tumor models are the transgenic PLAG1-overexpressing mouse model to study salivary gland pleomorphic adenoma (4) and the These mice carry a recessive point mutation in a phylogenetically conserved gene called mice expression of Gon4l protein is dramatically reduced resulting in a profound arrest in Tsc2 B cell development. We found that 25% of mice spontaneously develop salivary gland tumors suggesting that loss of Gon4l expression may be involved in salivary gland tumorigenesis in mice. We also characterized the morphologic and immunomarker phenotype of these tumors including the possible role of epidermal growth factor receptor (EGFR) signaling. Our findings suggest that the mouse strain may provide a tractable model for longitudinal study of salivary gland tumorgenesis and for testing therapeutics that target salivary gland tumors. MATERIALS AND METHODS Mice All procedures involving mice were approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Iowa and conformed to guidelines established by the National Institutes of Health (NIH). Mice homozygous for the mutation in (referred to here as mice) have been previously described (9 12 13 mice were generated C3HeB/FeJ (C3H) genetic background and subjected to a standard breeding scheme to isolate the relevant mutation. Afterward the mutant strain was maintained by intercrossing Justy mice. A cohort of 55 mice comprised of individuals aged 6 months or older was monitored up to 12 months of age for overt signs of disease. A cohort of 25 wild-type C3H mice was maintained in parallel as controls. Mice that developed cervical swelling or enlargement of the neck area were euthanized with CO2 inhalation and subject to a complete necropsy. LDN193189 HCl Tissues At necropsy cervical masses in affected mice were excised en bloc with adjacent salivary glands and immersion fixed in 10% neutral buffered formalin. Following fixation (approximately 5 days) tissues were routinely processed paraffin-embedded sectioned at 4 μm and stained with hematoxylin and eosin (HE). Markers of epithelial and mesenchymal tumor differentiation were assessed by immunohistochemistry (Table 1). The scoring for the immunohistochemical staining was as follows: “Neg” – none; “+” rare to 33% of tumor cells; “++” ~34% to 66% of tumor cells; “+++” ~67% to diffuse cellular immunostaining. Table 1 Primary antibodies and conditions for immunohistochemistry RESULTS Gross Pathology Individuals in a cohort of mice aged 6 months and older were found to sporadically develop ventrolateral cervical masses (Figure 1) with an incidence of 25%. These masses were generally circumscribed fluctuant to touch and when punctured would leak fluid contents that partially collapsed the tumor. The tumor tissue was often adherent to the adjacent salivary gland chain. Therefore the tumor and salivary glands were prosected en bloc for fixation and study. Among the mice there was no bias in tumor development with respect to sex and no tumors were observed in a similarly aged cohort of wild-type C3H mice. Figure 1 Gross anatomy of salivary.