Most genetically engineered mouse (GEM) models for colon cancer are based on tissuewide or germline gene modification, resulting in tumors predominantly of the small intestine. Several of these models involve modification of the adenomatous polyposis coli (Apc) gene and are excellent models for familial cancer predisposition syndromes. We have developed a stochastic somatic mutation model for sporadic colon cancer that presents with isolated primary tumors in the distal colon and recapitulates the entire adenoma-carcinoma-metastasis axis seen in human colon cancer. Using this model, we have analyzed tumors that are either solely mutant in the Apc gene or in combination with another colon cancer-associated mutant gene, the Kras G12D allele. Because of the restricted location in the distal colon, the natural history of the tumors can be analyzed by serial colonoscopy. As the mammalian target of rapamycin (mTOR) pathway is a critical component of the complex signaling network in colon cancer, we used this model to assess the efficacy of mTOR blockade through rapamycin treatment of mice with established tumors. After treatment, Apc mutant tumors were more than 80% smaller than control tumors. However, tumors that possessed both Apc and Kras mutations did not respond to rapamycin treatment. These studies suggest that mTOR inhibitors should be further explored as potential colorectal cancer therapies in patients whose tumors do not have activating mutations in KRAS.colon cancer | mouse model | adenovirus | colonoscopy | mammalian target of rapamycin C olon cancer continues to be one of the leading causes of cancerrelated deaths. The prognosis for patients with early stage cancers is good, but the majority of cancers are diagnosed at later stages (1). Most drug development strategies use transplantation of human tumor cells into immunocompromised mice. These models are not truly predictive of response in human patients because they are derived from tumor cell lines grown in vitro and are implanted into ectopic sites that bear no resemblance to the colonic microenvironment (2). Furthermore, these xenograft models fail to recapitulate the heterogeneous nature of cancer and the critical endogenous interplay between tumor and supporting stroma. Genetically engineered mouse (GEM) models circumvent these shortcomings, making them an attractive platform for biomarker discovery, study of cancer biology, and preclinical therapeutic trials (2, 3).Several GEMs that use germline or tissuewide modification of genes known to be mutated in human colon cancer spontaneously develop intestinal tumors (4). Depending on the gene(s) that is modified, these are reasonable models for inherited cancer predisposition syndromes, such as familial adenomatous polyposis (FAP) and hereditary nonpolyposis colon cancer (HNPCC). However, these are not models for sporadic colon cancer, which comprises 75-80% of all cases in humans (5). In these mouse models for FAP and HNPCC, the genetic mutations are present in the germline. Consequently, they are exp...
PurposeTo examine the in vitro and in vivo efficacy of the dual PI3K/mTOR inhibitor NVP-BEZ235 in treatment of PIK3CA wild-type colorectal cancer (CRC).Experimental Design
PIK3CA mutant and wild-type human CRC cell lines were treated in vitro with NVP-BEZ235, and the resulting effects on proliferation, apoptosis, and signaling were assessed. Colonic tumors from a genetically engineered mouse (GEM) model for sporadic wild-type PIK3CA CRC were treated in vivo with NVP-BEZ235. The resulting effects on macroscopic tumor growth/regression, proliferation, apoptosis, angiogenesis, and signaling were examined.Results
In vitro treatment of CRC cell lines with NVP-BEZ235 resulted in transient PI3K blockade, sustained decreases in mTORC1/mTORC2 signaling, and a corresponding decrease in cell viability (median IC50 = 9.0–14.3 nM). Similar effects were seen in paired isogenic CRC cell lines that differed only in the presence or absence of an activating PIK3CA mutant allele. In vivo treatment of colonic tumor-bearing mice with NVP-BEZ235 resulted in transient PI3K inhibition and sustained blockade of mTORC1/mTORC2 signaling. Longitudinal tumor surveillance by optical colonoscopy demonstrated a 97% increase in tumor size in control mice (p = 0.01) vs. a 43% decrease (p = 0.008) in treated mice. Ex vivo analysis of the NVP-BEZ235-treated tumors demonstrated a 56% decrease in proliferation (p = 0.003), no effects on apoptosis, and a 75% reduction in angiogenesis (p = 0.013).ConclusionsThese studies provide the preclinical rationale for studies examining the efficacy of the dual PI3K/mTOR inhibitor NVP-BEZ235 in treatment of PIK3CA wild-type CRC.
Interferon regulatory factors (IRFs) are a large family of transcription factors involved in regulating the transcriptional response of vertebrates to interferons and viral infection. In this report we describe the cloning and genomic organization of an IRF gene from the pufferfish (Fugu rubripes). The fugu IRF gene spans 2.7 kb from the transcription start site to the polyadenylation signal. It consists of 10 exons and 9 introns and encodes a protein of 296 amino acids. The overall amino acid sequence of fugu IRF displays 55% identity to flounder IRF and approximately 44% identity to avian and mammalian IRF-1 and IRF-2. On the basis of the genomic structure and the absence of a transcriptional repression domain, we conclude that the fugu IRF is a member of the IRF-1 family. The fugu IRF gene is expressed in a wide range of tissues. While a single transcript of 1.4 kb was detected in most tissues, several larger transcripts generated using alternative polyadenylation signals were found in the gills.
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