Inhibition of aberrant proliferation and induction of apoptosis in HER-2/neu oncogene transformed human mammary epithelial cells by N-(4-hydroxyphenyl)retinamide

Abstract

Epithelial cells from non-cancerous mammary tissue in response to exposure to chemical carcinogens or transfection with oncogenes exhibit hyperproliferation and hyperplasia prior to the development of cancer. Aberrant proliferation may, therefore, represent a modifiable early occurring preneoplastic event that is susceptible to chemoprevention of carcinogenesis. The synthetic retinoid N-(4-hydroxyphenyl)retinamide (HPR), has exhibited preventive efficacy in several in vitro and in vivo breast cancer models, and represents a promising chemopreventive compound for clinical trials. Clinically relevant biochemical and cellular mechanisms responsible for the chemopreventive effects of HPR, however, are not fully understood. Experiments were performed on preneoplastic human mammary epithelial 184-B5/HER cells derived from reduction mammoplasty and initiated for tumorigenic transformation by overexpression of HER-2/neu oncogene, to examine whether HPR inhibits aberrant proliferation of these cells and to identify the possible mechanism(s) responsible for the inhibitory effects of HPR. Continuous 7-day treatment with HPR produced a dose-dependent, reversible growth inhibition. Long-term (21 day) treatment of 184-B5/HER cells with HPR inhibited anchorage-dependent colony formation by approximately 80% (P < 0.01) relative to that observed in the solvent control. A 24 h treatment with cytostatic 400 nM HPR produced a 25% increase (P = 0.01) in G0/G1 phase, and a 36% decrease (P = 0.01) in S phase of the cell cycle. HPR treatment also induced a 10-fold increase (P = 0.02) in the sub-G0 (apoptotic) peak that was down-regulated in the presence of the antioxidant N-acetyl-L-cysteine. Treatment with HPR resulted in a 30% reduction of cellular immunoreactivity to tyrosine kinase, whereas immunoreactivity to p185HER remained essentially unaltered. HPR exposure resulted in time-dependent increase in cellular metabolism of the retinoid as evidenced by increased formation of the inert metabolite N-(4-methoxyphenyl)-retinamide (MPR) and progressive increase in apoptosis. Thus, HPR-induced inhibition of aberrant proliferation may be caused, in part, by its ability to inhibit HER-2/neu-mediated proliferative signal transduction, retard cell cycle progression and upregulate cellular apoptosis.

HER2/neu reduces the apoptotic effects of N-(4-hydroxyphenyl)retinamide (4-HPR) in breast cancer cells by decreasing nitric oxide production

“…However, Jinno et al (1999) reported that 4-HPR was able to induce apoptosis in the preneoplastic human mammary epithelial 184-B5/HER cell line bearing high levels of HER2/ neu. This discrepancy may be due to their use of an immortalized, nontumorigenic mammary epithelial cell line, whereas we used breast tumorigenic cell lines.…”

Prevention of early-onset familial/hereditary colon cancer: New models and mechanistic biomarkers (Review)

“…Our previous studies on mammary and colon cell culture models have demonstrated that, independent of the nature of carcinogenic insult, the target cells exhibit perturbed expression of relevant biomarkers in vitro preceding tumorigenesis in vivo (17)(18)(19)(20)23,30,31,33). Furthermore, initiated target cells in response to mechanistically distinct chemopreventive agents exhibit down-regulation of perturbed end-point biomarkers (21)(22)(23)(24)(25)(26)(27)(28)30,31,(33)(34)(35)(36).…”

“…In these cell lines, exposure to chemical carcinogens or transfection with selected clinically relevant oncogenes results in aberrant cell cycle progression, down-regulation of apoptosis, altered expression of cell cycle regulatory and apoptosis associated gene products, and anchorage-independent growth in vitro preceding tumorigenesis in vivo (17)(18)(19)(20). Additionally, the transformed cell lines respond to treatment with several mechanistically distinct chemopreventive agents, and exhibit effective modulation of the perturbed surrogate end-point biomarkers for carcinogenic risk (21)(22)(23)(24)(25)(26)(27)(28) The present review provides an in-depth discussion of the data on preclinical animal models of FAP and HNPCC syndromes, and summarizes recently completed studies on the newly developed cell culture models for early-onset familial/hereditary colon cancer.…”

RAR agonists stimulate SOX9 gene expression in breast cancer cell lines: evidence for a role in retinoid-mediated growth inhibition

“…Rb, cyclin D and E, cyclin dependent kinases 2, 4, and 6, and their inhibitors p15, p16, p21 and p27 have all been suggested as potential targets for retinoids in normal and malignant breast cells as well as other cell types that are sensitive to retinoidmediated growth inhibition (Langenfeld et al, 1996;Seewaldt et al, 1997b;Zhou et al, 1997). In addition to mediating cell cycle changes, apoptosis of retinoid responsive cells has been observed by several investigators (Jinno et al, 1999;Mangiarotti et al, 1998;Shao et al, 1995;Sheikh et al, 1995;Teixeira and Pratt, 1997). Despite the cloning and characterization of the RARs and RXRs, and study of the activities of a variety of retinoid receptor specific ligands in breast cancer cell lines (Arafa et al, 1996(Arafa et al, , 2000Desai et al, 2000;Gianni et al, 1996;Willhite et al, 1996), the fundamental mechanisms of retinoid-mediated growth inhibition remain poorly understood.…”