Analysis of candidate genes included in the mammary cancer susceptibility 1 (Mcs1) region

Abstract

The rat strain COP is resistant to spontaneous and carcinogen-induced mammary cancer, whereas the strain WF is susceptible. Using genetic linkage analysis of (WF x COP) F1 x WF backcrosses, LC Hsu, LA Shepel and co-workers showed that a region at the centromeric end of Chromosome (Chr) 2 (2q1) segregates with the sensitivity to mammary cancer development. The responsible locus was named Mcs1 (for mammary cancer susceptibility 1). We have developed the chromosome map of the 2q1 region by localizing 18 genes, 4 ESTs, and several anonymous markers, using radiation hybrids and fluorescence in situ hybridization. The region containing Mcs1 was delineated to 2q12-q14. Five of the genes (Mef2c, Map1b, Ccnh, Rasa, Rasgrf2) were assigned to this region and were shown to be expressed in the rat mammary glands, while three possible functional candidate genes, Pi3kr1, Rad17, and Naip, were excluded from the critical region. Since cyclin H, encoded by Ccnh, plays an important role in the control of the cell cycle and since the proteins encoded by Rasa and Rasgrf2 control the activity of the RAS oncoprotein, the corresponding genes appeared as both functional and positional Mcs1 candidates. RT-PCR experiments on RNA extracted from mammary glands of the two rat strains (COP, WF) was done. No amino acid sequence difference was found between the two strains. These results argue against the hypothesis that any of these three genes is Mcs1.

Allelic imbalance and altered expression of genes in chromosome 2q11–2q16 from rat mammary gland carcinomas induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine

“…The approximate region of under-representation found by CGH analysis of PhIP-induced rat mammary gland carcinomas is from Christian et al (2002). The approximate location of several physically mapped genes and microsatellite markers is from http://ratmap.gen.gu.se as refined according to Laes et al (2001) and Quan et al (2000) Position from SHRSP Â BN or FHH Â ACI of genetic map (http://rgd.mcw.edu/). N/A, not available.…”

“…Out of the 34 markers examined, nine markers residing by linkage analysis in the centromeric region of 2q showed allelic imbalance involving MSI and/or LOH. Of the markers showing allelic imbalance, D2Rat188 and D2Rat189 are by linkage mapping most proximally located (Laes et al, 2001). Approximately, 50% of carcinomas showed allelic imbalance at these markers.…”

“…The centromeric region of rat chromosome 2q contains multiple genes potentially involved in mammary gland carcinogenesis such as the mammary gland cancer susceptibility 1 (Mcs1) gene (Hsu et al, 1994;Haag et al, 1996;Shepel et al, 1998;Szpirer et al, 1999;Quan et al, 2000;Laes et al, 2001) (http://ratmap.gen.gu.se/) (Figure 1). Mcs1 is one of the several mammary gland cancer susceptibility genes that modify the susceptibility of rats to chemical and radiation-induced mammary carcinogenesis (Shepel et al, 1998).…”

“…Six of six PhIPinduced mammary carcinomas examined by CGH analysis show under-representation in the centromeric region of 2q, and therefore possibly involving the Mcs1 gene locus (Christian et al, 2002). Multiple microsatellite markers are currently available to examine this region for allelic imbalance in more detail (http:// ratmap.gen.gu.se/) (Szpirer et al, 1999;Quan et al, 2000;Laes et al, 2001). Several of the known genes mapped in this region include genes that regulate the activity of Ras including Rasa (Ras GTP-ase activating protein, Ras-GAP) and Rasgrf2 (Ras guanine nucleotide exchange factor 2).…”

“…In addition, this region harbors Pi3kr1, the p85a subunit of phosphatidylinositol 3-kinase (PI3K), a gene known to cooperate with H-Ras in cellular transformation (Rodriguez-Viciana et al, 1997;Rodriguez-Viciana and Downward, 2001). Other genes in this region include Ccnb1 and Ccnh, as well as Il6st (gp130), a cytokine receptor modulator, all potentially implicated in carcinogenesis and/or mammary gland carcinogenesis (Szpirer et al, 1999;Laes et al, 2001). With the purpose of obtaining a view to the involvement of genes in the frequently deleted region of chromosome 2q, the current study examines 2q11-2q16 for allelic imbalance with microsatellite markers, and evaluates the expression of known cancer-regulating genes residing in this region by quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry (IHC).…”