Allelic imbalance at 11p15.5–15.4 correlated with c‐Ha‐ras mutation during radiation‐induced neoplastic transformation of human breast epithelial cells

Abstract

Breast cancer is the most frequent malignancy in women throughout much of the developed world and is associated with a multistage process involving a number of genetic mutations and their corresponding cellular phenotypic alterations. It has already been shown that neoplastic transformation of a spontaneously immortalized human breast epithelial (MCF-10F) cell line by radiation, in combination with estrogen, represents a successful model in studying the molecular and biological alterations that may contribute to the tumorigenic process. In the present study, the incidence of allelic alterations (microsatellite instability/loss of heterozygosity) on chromosome 11 in different radiation-induced primary and secondary tumorigenic cell lines, relative to the control MCF-10F cells was investigated. We identified 3 regions of the chromosome 11 (11p15-p15.5, 11q13 and 11q23) that showed high incidence of LOH among these tumor cell lines and suggested a potential role for these chromosomal regions in breast carcinogenesis. Among them, locus 11p15.5, where c-Ha-ras oncogene is located, had incidence of allelic imbalance between 25-40%. Furthermore, direct sequencing analysis of codons 12 and 61 of the c-Ha-ras oncogene identified various point mutations. These data highlight the importance of chromosome 11 in radiation induced malignant transformation of human breast epithelial cells and suggest the usefulness of the model in uncovering specific derangements during breast cancer progression.

Cooperative induction of rat mammary cancer by radiation and 1‐methyl‐1‐nitrosourea via the oncogenic pathways involving c‐Myc activation and H‐ras mutation

“…37 Assuming that loss of the nonmutated allele is rate limiting during MNU-induced H-ras-mediated carcinogenesis, it is reasonable to speculate that radiation enhances this step through its delayed mutagenic effect. However, this is not likely because the normal H-ras allele was still present in most of the cancers in our study.…”

Effect of curcumin on irradiated and estrogen-transformed human breast cell lines

“…To test for cell growth in semisolid medium, curcumin-treated cells were trypsinized and plated at a density of 1x10 5 cells in 10 ml of 0.35% agarose over a 0.7% agar base in 100-mm culture dishes as described (23,24). Media were replenished every day and colonies were scored after 21 days in culture.…”

“…Among the oncogenes, c-Ha-Ras and Ras homologous A (Rho-A) from the Ras super family have been shown to promote both cell proliferation and invasion indicating their importance in malignant transformation (20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). A critical step in the stimulation of cell surface receptors by their ligand involves the accumulation of Ras proteins in their active GTP-bound state.…”

CLCA2 tumour suppressor gene in 1p31 is epigenetically regulated in breast cancer

“…Once a small region of frequent LOH has been identified, it is then possible to use positional cloning strategies to isolate candidate genes from the region. Although there is evidence that genes in chromosome regions 11p15 (Lichy et al, 1998;Roy et al, 2003) and 17p13 (Hoff et al, 2001) may be important in breast cancer tumorigenesis, chromosome 1 is the most frequently involved in rearrangements in sporadic tumours (Hoggard et al, 1995;Nagai et al, 1995;Tsukamoto et al, 1998). These aberrations frequently result in loss of material from the short arm of chromosome 1 (1p).…”