Genetic signatures of High- and Low-Risk Aberrant Crypt Foci in a Mouse Model of Sporadic Colon Cancer

Abstract

To determine whether cancer risk is related to histopathological features of preneoplastic aberrant crypt foci (ACF), gene expression analysis was performed on ACF from two mouse strains with differing tumor sensitivity to the colonotropic carcinogen, azoxymethane. ACF from sensitive A/J mice were considered at high risk, whereas ACF from resistant AKR/J mice were considered at low risk for tumorigenesis. A/J and AKR/J mice received weekly injections of azoxymethane (10 mg/kg body weight), and frozen colon sections were prepared 6 weeks later. Immunohistochemistry was performed using biomarkers associated with colon cancer, including adenomatous polyposis coli, ␤-catenin, p53, c-myc, cyclin D1, and proliferating cell nuclear antigen. Hyperplastic ACF, dysplastic ACF, microadenomas, adjacent normal-appearing epithelium, and vehicle-treated colons were laser captured, and RNA was linearly amplified (LCM-LA) and subjected to cDNA microarray-based expression analysis. Patterns of gene expression were identified using adaptive centroid algorithm. ACF from low-and high-risk colons were not discriminated by immunohistochemistry, with the exception of membrane staining of ␤-catenin. To develop genetic signatures that predict cancer risk, LCM-LA RNA from ACF was hybridized to cDNA arrays. Of 4896 interrogated genes, 220 clustered into six broad clusters. A total of 226 and 202 genes was consistently altered in lesions from A/J and AKR/J mice, respectively. Although many alterations were common to both strains, expression profiles stratified high-and low-risk lesions. These data demonstrate that ACF with distinct tumorigenic potential have distinguishing molecular features. In addition to providing insight into colon cancer promotion, our data identify potential biomarkers for determining colon cancer risk in humans.

The apoptosis-inducing effect of gastrin on colorectal cancer cells relates to an increased IEX-1 expression mediating NF-κB inhibition

“…The finding that IEX-1 seems to be implicated in the tumor-suppressive activity of G17 fits to the recent observations indicating that IEX-1 expression and carcinogenesis are inversely related, for example, in mammary and colon cancer (Hu et al, 2004;Nambiar et al, 2004) or in neuroendocrine tumors (Dilley et al, 2005). Most notably, a recent study identified IEX-1 as a potential tumor-suppressive gene in colorectal carcinogenesis where IEX-1 is downregulated early in premalignant lesions giving rise to colon cancer (Nambiar et al, 2004) and the same authors performed an immunohistochemical analysis demonstrating that tumor tissue from colon cancer patients is devoid of IEX-1 expression, whereas in normal colonic tissue IEX-1 expression was readily detectable.…”

“…Most notably, a recent study identified IEX-1 as a potential tumor-suppressive gene in colorectal carcinogenesis where IEX-1 is downregulated early in premalignant lesions giving rise to colon cancer (Nambiar et al, 2004) and the same authors performed an immunohistochemical analysis demonstrating that tumor tissue from colon cancer patients is devoid of IEX-1 expression, whereas in normal colonic tissue IEX-1 expression was readily detectable. It is, therefore, tempting to speculate that, by inducing IEX-1 expression, G17 induces apoptosis in colorectal cancer cells, thereby preventing rather than favoring tumorigenesis in the colon.…”

Susceptibility of Snark‐deficient mice to azoxymethane‐induced colorectal tumorigenesis and the formation of aberrant crypt foci

“…Aberrant crypt foci are regarded as preneoplastic lesions in rodent models and humans. (19)(20)(21)(22)(23)(24)(25) Although the C57BL/6 strain is known to be resistant to the induction of colon tumors by AOM, (26) at least one ACF was detected in all of the mice in the long-term experiment ( Table 2). The high AOM dose and the relatively long experimental period might have contributed to the increased susceptibility to ACF formation seen in wild-type mice.…”

Epidemiology of colonic aberrant crypt foci: Review and analysis of existing studies

“…In addition, if specific molecular signatures in ACF of malignant potential are discovered (for example, by gene expression profiling; [60]), then for at least those lesions in the distal colon/ rectum that are examined, their removal could decrease future risk and result in cancer prevention. …”