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C57BL/6J mice carrying the Min allele of Adenomatous polyposis coli (Apc) develop numerous adenomas along the entire length of the intestine and consequently die at an early age. This short lifespan would prevent the accumulation of somatic genetic mutations or epigenetic alterations necessary for tumor progression. To overcome this limitation, we generated F1 ApcMin/+ hybrids by crossing C57BR/cdcJ and SWR/J females to C57BL/6J ApcMin/+ males. These hybrids developed few intestinal tumors and often lived longer than 1 year. Many of the tumors (24-87%) were invasive adenocarcinomas, in which neoplastic tissue penetrated through the muscle wall into the mesentery. In a few cases (3%), lesions metastasized by extension to regional lymph nodes. The development of these familial cancers does not require chromosomal gains or losses, a high level of microsatellite instability, or the presence of Helicobacter. To test whether genetic instability might accelerate tumor progression, we generated ApcMin/+ mice homozygous for the hypomorphic allele of the Nijmegen breakage syndrome gene (Nbs1ΔB) and also treated ApcMin/+ mice with a strong somatic mutagen. These imposed genetic instabilities did not reduce the time required for cancers to form nor increase the percentage of cancers nor drive progression to the point of distant metastasis. In summary, we have found that the ApcMin/+ mouse model for familial intestinal cancer can develop frequent invasive cancers in the absence of overt genomic instability. Possible factors that promote invasion include age-dependent epigenetic changes, conservative somatic recombination, or direct effects of alleles in the F1 hybrid genetic background. [Cancer Res 2009;69(14):5768–75]

Alterations of the Wnt/β-catenin signaling pathway are positively associated with the development and progression of human cancer, including carcinoma of the prostate. To determine the role of activated Wnt/β-catenin signaling in mouse prostate carcinogenesis, we created a mouse prostate tumor model using probasin-Cre–mediated deletion of Apc. Prostate tumors induced by the deletion of Apc have elevated levels of β-catenin protein and are highly proliferative. Tumor formation is fully penetrant and follows a consistent pattern of progression. Hyperplasia is observed as early as 4.5 weeks of age, and adenocarcinoma is observed by 7 months. Continued tumor growth usually necessitated sacrifice between 12 and 15 months of age. Despite the high proliferation rate, we have not observed metastasis of these tumors to the lymph nodes or other organs. Surgical castration of 6-week-old mice inhibited tumor formation, and castration of mice with more advanced tumors resulted in the partial regression of specific prostate glands. However, significant areas of carcinoma remained 2 months postcastration, suggesting that tumors induced by Apc loss of function are capable of growth under conditions of androgen depletion. We conclude that the prostate-specific deletion of Apc and the increased expression of β-catenin associated with prostate carcinoma suggests a role for β-catenin in prostate cancer and offers an appropriate animal model to investigate the interaction of Wnt signaling with other genetic and epigenetic signals in prostate carcinogenesis. [Cancer Res 2007;67(6):2490–6]

Animal models, particularly mouse models, play a central role in the study of the etiology, prevention, and treatment of human prostate cancer. While tissue culture models are extremely useful in understanding the biology of prostate cancer, they cannot recapitulate the complex cellular interactions within the tumor microenvironment that play a key role in cancer initiation and progression. The National Cancer Institute (NCI) Mouse Models of Human Cancers Consortium convened a group of human and veterinary pathologists to review the current animal models of prostate cancer and make recommendations about the pathologic analysis of these models. More than 40 different models with 439 samples were reviewed, including genetically engineered mouse models, xenograft, rat, and canine models. Numerous relevant models have been developed over the past 15 years, and each approach has strengths and weaknesses. Analysis of multiple genetically engineered models has shown that reactive stroma formation is present in all the models developing invasive carcinomas. In addition, numerous models with multiple genetic alterations display aggressive phenotypes characterized by sarcomatoid carcinomas and metastases, which is presumably a histologic manifestation of epithelial–mesenchymal transition. The significant progress in development of improved models of prostate cancer has already accelerated our understanding of the complex biology of prostate cancer and promises to enhance development of new approaches to prevention, detection, and treatment of this common malignancy. Cancer Res; 73(9); 2718–36. ©2013 AACR.

Aberrations in the phosphoinositide 3-kinase (PI3K) signaling pathway play a key role in the pathogenesis of numerous cancers by altering cellular growth, metabolism, proliferation, and apoptosis. Mutations in the catalytic domain of PI3K that generate a dominantly active kinase are commonly found in human colorectal cancers and have been thought to drive tumor progression but not initiation. However, the effects of constitutively activated PI3K upon the intestinal mucosa have not been previously studied in animal models. Here, we show that the expression of a dominantly active form of the PI3K protein in the mouse intestine results in hyperplasia and advanced neoplasia. Mice expressing constitutively active PI3K in the epithelial cells of the distal small bowel and colon rapidly developed invasive adenocarcinomas in the colon that spread into the mesentery and adjacent organs. The histologic characteristics of these tumors were strikingly similar to invasive mucinous colon cancers in humans. Interestingly, these tumors formed without a benign polypoid intermediary, consistent with the lack of aberrant WNT signaling observed. Together, our findings indicate a noncanonical mechanism of colon tumor initiation that is mediated through activation of PI3K. This unique model has the potential to further our understanding of human disease and facilitate the development of therapeutics through pharmacologic screening and biomarker identification. Cancer Res; 72(12); 2931–6. ©2012 AACR.

Background: Colorectal cancer (CRC) often arises from adenomatous polyps that progress to invasive cancer, but polyps can also remain static in size, regress, or resolve. Predicting which progress and which remain benign is difficult, since longitudinal analysis of individual polyps is impossible due to removal in humans. There are currently no molecular signatures that can identify adenomas that will eventually progress. In patients with stage II and III CRC , adjuvant chemotherapy on a 5-fluorouracil (5FU)-based regimen is considered following surgery. Despite receiving post-operative therapy, almost 50% of patients with stage III cancer recur. Again, there is no molecular signature that can predict response to 5FU. The purpose of this study was to identify gene expression differences in colon tumors using a mouse model. Individual tumors in mice can be monitored longitudinally throughout progression and treatment. Specifically, we aimed to: (1) develop and characterize a new mouse model of colon cancer; (2) identify differences in molecular progression prior to histopathologcial progression; and (3) identify a priori differences in gene expression between tumors that are resistant or sensitive to 5FU. Methods: (SWRxB6)F1.ApcMin/+ (F1.Min) mice were treated with the inflammatory agent dextran sodium sulfate to induce tumors in the distal colon. Colonoscopy was used to identify, follow, and biopsy individual tumors. To best define chemotherapy response, only tumors that exhibited stasis for 4 weeks prior were treated with 5FU. Gene expression was analyzed from serial biopsies from pre- and post-treatment tumor using microarray and qPCR. Results: Tumors in F1.Min mice exhibit growth, stasis, and spontaneous regression. A majority of tumors become static in size after an initial period of growth. Histological evaluation of tumors revealed that many tumors remained adenomas (71%), while some advanced to intramucosal carcinomas (23%) and adenocarcinomas (3%). Interestingly, 3 tumors that remained adenomas and 3 that progressed to intramucosal carcinomas displayed differential expression of 68 genes regardless of time point. Analysis of pre-5FU biopsies from 5 resistant tumors and 6 sensitive tumors revealed differential expression patterns of Hp1bp3 and Xpo7. Conclusions: F1.Min mice develop tumors that can progress to invasive adenocarcinomas, and tumor response to treatment with chemotherapy can be followed in real time. Differential expression of genes with prognostic benefit can occur early and can be sustained throughout tumor development. Molecular determinants of 5FU sensitivity can be identified prior to treatment. Defining expression patterns that predict outcomes to chemotherapy in CRC might minimize the risk of undergoing ineffective chemotherapy and identify patients that may benefit from other treatment approaches in the adjuvant setting. Citation Format: Jamie N. Hadac, Terrah J. Paul Olson, Alyssa A. Leystra, Dawn M. Albrecht, Linda Clipson, Ruth Sullivan, Michael A. Newton, Richard B. Halberg, William R. Schelman. Characterization of molecular signatures predicting response to 5-FU based chemotherapy in mouse models of colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2356. doi:10.1158/1538-7445.AM2014-2356

Lung cancer has the highest United States and worldwide rate of cancer mortality, exceeding the mortality rates of colorectal, breast and prostate cancers combined. Tobacco smoking is well established as the major etiological risk factor for lung cancer, contributing to an increased risk in long-term smokers compared with non-smokers. The risk of the development of lung cancer in lifelong smokers is 20-40 times higher than that in non-smokers. Moreover, tobacco use accounts for 30% of overall lung cancer mortality. Given the large population at increased risk of developing lung cancer, the development of approaches to prevent smoking related lung cancer would have great clinical benefit. Pomegranate (Punica granatum, Punicaceae), is an edible fruit cultivated in Mediterranean countries, Afghanistan, India, China, Japan, Russia and the United States. Based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, pomegranate fruit extract (PFE) was found to contain anthocyanins (such as delphinidin, cyanidin and pelargonidin) and several hydrolyzable tannins (such as punicalin, pedunculagin, punicalagin, gallagic and ellagic acid esters of glucose) which account for 92% of the antioxidant activity of the whole fruit. We have earlier reported that PFE inhibits prosurvival signaling pathways in human lung carcinoma A549 cells and tumor growth in athymic nude mice (Carcinogenesis 2007; 28:163-73) and A/J mice (Cancer Res 2007; 67:3475-82). In this study, the effect of PFE consumption during progression of lung adenomas to adenocarcinomas was investigated in two mouse tumor protocols. NNK, a tobacco-specific N-nitrosamine, is believed to be one of the most promising candidates of lung carcinogen in humans. B(a)P is one of the most ubiquitous environmental polycyclic aromatic hydrocarbons present in automobile exhaust and cigarette smoke and it induces lung tumors in mice. Since majority of current and ex-smokers have small nodules, it is highly desirable to prevent additional growth of lung cancer after the appearance of nodules. To mimic this situation, PFE (0.2% PFE, w/v) was given to A/J mice in drinking water after the establishment of lung adenomas induced by NNK and B(a)P. Treatment with PFE significantly reduced the lung tumor multiplicity by 33% in mice treated with NNK and 29% in B(a)P-treated mice. PFE also caused significant reduction in the expression of COX-2, RAR-β, VEGF, CD-31 and angiopoietin-2 in lungs of mice treated with NNK and B(a)P. On administration of PFE, there was decrease in the multiplicity and incidence of lung adenomas and adenocarcinomas in mice treated with NNK and B(a)P. Thus, our results indicate that PFE has the potential to be developed as an agent against tobacco smoke-induced lung cancer and for improving the quality of life of early stage lung cancer patients and ex-smokers. Citation Format: Naghma Khan, Ruth Sullivan, Tien Hoang, Tejaswi Dittakavi, Hasan Mukhtar. Delay in the progression of lung adenoma to adenocarcinoma in mice by oral consumption of pomegranate fruit extract. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 194. doi:10.1158/1538-7445.AM2013-194

Background: Mutations in PIK3CA are a common feature of human cancers and multiple new PI3K inhibitors are in clinical development. These mutations are present in 20-30% of colorectal cancers in humans; however, the effects of such mutations on the intestinal mucosa have not been previously studied in animal models. Here we demonstrate that the expression of a dominant active form of the PI3K protein in the mouse intestine results not only in hyperplasia but also advanced neoplasia. Methods: Mice carrying a transgene in which the fatty acid binding protein promoter is fused to Cre recombinase (FC) were crossed to mice carrying a transgene encoding a chimeric protein with the iSH2 domain of the p85 subunit fused to the N-terminus of p110 (PIK3ca*). Progeny carrying both transgenes (FC PIK3ca*) express this constitutively active form of p110 in epithelial cells of the distal small bowel and colon. Results: Invasive mucinous adenocarcinomas develop in the proximal colon by only 50 days of age. These tumors are very aggressive, spreading into the mesentery and adjacent organs, and their histological characteristics are strikingly similar to those of invasive colon cancers in humans. Neoplastic cells exhibit a high rate of cell proliferation as seen by increased Ki67 immunohistochemical staining and phosphorylation of AKT, pS6, and p4E-BP1 by western blot demonstrating downstream signaling of PI3K. Interestingly, these cells did not exhibit perturbations in ERK and WNT signaling. Consistent with the lack of aberrant WNT signaling, no benign polypoid intermediaries were identified. Together, the results indicate that tumors in this model form via a non-canonical mechanism. A cohort of FC PIK3ca* mice were imaged by FDG dual hybrid PET/CT colonography and mice with similar sized tumors were divided into control and experimental arms. The experimental arm was treated with rapamycin (6mg/kg/day) for 14 days. Both groups were re-imaged 14 days later. The full results of the rapamycin treatment will be presented. Conclusion: This unique model of advanced colonic invasive adenocarcinomas has the potential to further our understanding of human disease and facilitate the development of therapeutics, especially inhibitors targeting downstream of PI3K. 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 1341. doi:1538-7445.AM2012-1341

Mouse models have been invaluable tools for studying human cancer. Given the contribution of mouse models to understanding tumorigenesis, when a spontaneous mouse mutant that developed heritable T cell lymphoblastic leukemia/lymphoma (T-ALL) arose in our colony, we pursued studies to both characterize the disease in these mice and to identify the mutant gene responsible for the phenotype. Because the mutation was spontaneous and the phenotype was dominant, we named the mutant Spontaneous dominant leukemia (Sdl). Sdl heterozygous mice develop disease with short latency and high penetrance; while mice homozygous for the mutation die early during embryonic development. We have discovered a spontaneously acquired mutation in Mcm4 in Sdl mice by whole exome sequencing. MCM4 is part of the heterohexameric complex of MCM2–7 that is important for licensing of DNA origins prior to S phase and also serves as the core of the replicative helicase that unwinds DNA at the replication fork. Previous studies in murine models have discovered that reduced levels of MCM complexes resulting from hypomorphic Mcm alleles promote tumor formation by causing genomic instability. However, Sdl mice possess normal levels of MCMs and there is no evidence for loss-of-heterozygosity at the Mcm4 locus in Sdl leukemias; indicating that the Sdl Mcm4 allele is not a hypomorphic or loss-of-function allele. Sdl mice harbor increased numbers of spontaneous micronuclei and Sdl T-ALLs are characterized by intragenic deletions at the Notch1 locus. Therefore, our studies indicate that dominantly acting alleles of MCMs can be compatible with viability but have dramatic oncogenic consequences caused by chromosome instability. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A37.