Amplification of Mycn, Ddx1, Rrm2, and Odc1 in rat uterine endometrial carcinomas

Abstract

The BDII rat is genetically predisposed to estrogen-dependent endometrial adenocarcinoma and represents a valuable model for this type of tumor. Tumors arising in strain crosses involving the BDII rats had previously been screened for DNA copy number changes using comparative genome hybridization (CGH). It was found that extra copies of the proximal region of rat chromosome (RNO) 6 commonly could be detected in these tumors. Based on RH-mapping data and comparative mapping with mouse and human, seven cancer-related genes were predicted to be situated in RNO6q14-q16. Rat PACs were isolated for the N-myc proto-oncogene (Mycn), apolipoprotein B (Apob), the DEAD box gene 1 (Ddx1), ornithine decarboxylase 1 (Odc1), proopiomelanocortin (Pomc1), ribonucleotide reductase, M2 polypeptide (Rrm2), and syndecan 1 (Sdc1). The localization of the genes to the region was verified by FISH (fluorescence in situ hybridization) mapping, and the detailed order among them was determined by dual-color FISH. By Southern blot analysis, it was found that the Mycn locus was highly amplified in two out of 10 cell cultures derived from the tumors. In one of them (designated RUT30), the amplification level of Mycn was estimated at 140x. Two other genes were coamplified (Ddx1 and Rrm2) at much lower levels. Similarly, in another culture (designated RUT2), Mycn was amplified more than 40x, whereas three of the other genes (Ddx1, Rrm2, and Odc1) were coamplified at lower levels. Using FISH on metaphase chromosomes from the cell cultures analyzed, the amplified sequences were shown to be located in typical HSRs. With competitive RT-PCR, distinct overexpression of Mycn and Ddx1 could be demonstrated in both RUT2 and RUT30. In addition, Mycn was overexpressed in two other tumors not exhibiting Mycn amplification. Taken together, our results suggest that overexpression of Mycn plays an important role in the development of endometrial cancer in the BDII rat. In humans, Mycn amplification has been reported mainly from tumors of neuronal origin. To our knowledge, this is the first report of Mycn amplification and overexpression in hormone-dependent tumors.

Molecular classification of spontaneous endometrial adenocarcinomas in BDII rats

“…Additionally, neither microsatellite instability (Behboudi et al 2001, Adamovic et al 2005, Nordlander et al 2005 nor Erbb2 amplifications were previously found among BDII rat tumors. Expression of Estrogen receptor a (ER1) was detected in the majority and progesterone receptor (Pgr) in a subset of these tumors (Karlsson et al 2001). Here, we combined gene expression, AI, and gene mutation analysis to further characterize molecular features of endometrial carcinogenesis in the BDII rat model with respect to available molecular data for different subtypes of human ECs (Table 4).…”

“…In conclusion, the EC developed in BDII rats are suggested to be related to human type I tumors, since they are hormone-related , Deerberg et al 1995, express Esr1 (Karlsson et al 2001) and histologically from endometrioid type (Kaspareit-Rittinghausen et al 1987). At the molecular level, it has been shown that P16 deletions (Adamovic (Nordlander et al 2007) are frequent, Furthermore, Erbb2 amplification, K-ras mutation , and microsatellite instability (Behboudi et al 2001, Adamovic et al 2005, Nordlander et al 2005 were not common features of BDII rat EAC tumors.…”

Weighted Gene Co-expression Network Analysis in Identification of Endometrial Cancer Prognosis Markers

“…MYCN is proved high amplification in endometrial adenocarcinoma. This suggests overexpression of MYCN contributes to the development of EC in the BDII rat (Karlsson et al, 2001). The PAX5 protein targets and activates the expression of MYCN (Nutt et al, 1998;Bougel et al, 2010).…”

“…Several studies indicate that extra copies of the proximal region of rat chromosome (RNO) 6 commonly could be detected in endometrial adenocarcinoma. Cancerrelated genes were located in RNO6q14-q16, such as MYCN (Karlsson et al, 2001;Adamovic et al, 2005). MYCN is a member of the MYC family of oncogenes which code for transcription factors containing a basichelix-loop-helix-leucine zipper domain.…”

Chromosome ideograms of the laboratory rat <i>(Rattus norvegicus)</i> based on high-resolution banding, and anchoring of the cytogenetic map to the DNA sequence by FISH in sample chromosomes

“…PAC probes were obtained as described previously (Karlsson et al, 2001;Adamovic et al, 2005). For BAC probes, rat genomic and/or cDNA sequence data for each gene was secured from the GenBank database (http://www2.ncbi.nlm.nih.gov/genbank/).…”