Response of human mammary epithelial cells to DNA damage induced by BPDE: involvement of novel regulatory pathways

Abstract

The responses of a line of normal human mammary epithelial cells, HME87, to treatment with the ultimate carcinogen benzo[a]pyrene diol epoxide (BPDE) were analyzed using a directed gene expression analysis technique, RAGE. Under conditions where cell number was decreased by 50% 24 or 48 h post-treatment, flow cytometry demonstrated no establishment of a G(1)/S arrest nor induction of apoptosis; cells continued to enter S phase from G(1) for at least 24 h but were blocked at G(2)/M. Using the RAGE technique, changes in gene expression were assayed for over 1000 genes, and multiple time-point data were collected for approximately 90 genes. In accord with the cell cycle studies, expression of the p21-WAF1 gene, the major mediator of p53-dependent G(1)/S arrest, did not increase until 24 h post-treatment. The expression of other target genes for transactivation by p53 was increased at early time points, including GADD45, an effector of the G(2)/M checkpoint, and WIP1. Analyses of proteins in treated cells indicated that p53 was phosphorylated at Ser15 but not at Ser20 within 30 min of treatment, and this correlated with an increase in the total amount of p53 protein. Significant expression changes were noted in a number of transcription factor genes, including ATF3 and E2A, genes that have not been previously connected to a response to DNA damage involving bulky chemical adducts. In addition, expression of the XPC gene was induced by BPDE treatment; the XPC product is thought to be involved in recognition of DNA damage by the nucleotide excision repair system.

The involvement of XPC protein in the cisplatin DNA damaging treatment-mediated cellular response

“…The XPC protein recognizes a variety of bulky DNA damages including UV-caused cyclobutane pyrimidine dimers and cisplatin-generated interstrand crosslinks (ICL) [9][10][11][12][13][14][15][16]. The XPC protein binds tightly with an HR23B protein to form a stable XPC-HR23B complex [17][18][19].…”

Benzo[a]pyrene and Human Embryo

“…Moreover, cell cycle phases showed an accumulation of cells in the G1 and G2 phase after B[a]P exposure (Vaziri et al, 1997;Zhu et al, 2005). It has also been shown that BPDE, the metabolite of B[a]P, can induce a G2/M accumulation (Wang et al, 2003). In line with these findings, G1-S arrest was observed in testis of B[a]P exposed male mice (Verhofstad et al, 2010).…”

Oncogenic role of DDX3 in breast cancer biogenesis

“…Moreover, there is emerging evidence that indicates that human mammary epithelium may be susceptible to carcinogenic transformation upon exposure to BPDE (Mei et al, 2003). For instance, human mammary epithelial cells and breast cancer cell lines, exposed to BPDE, exhibited altered cell cycle progression, decreased BRCA-1 expression and an increased spectrum of p53 mutations (Jeffy et al, 2002;Pfeifer et al, 2002;Wang et al, 2003;Burdick et al, 2006). It has also been shown that treating MCF 10A cells with 1 mM of B[a]P for 48 hours is sufficient to cause chromosomal aberrations and induce anchorageindependent growth (Caruso et al, 2001).…”