Induction of PDCD4 tumor suppressor gene expression by RAR agonists, antiestrogen and HER-2/neu antagonist in breast cancer cells. Evidence for a role in apoptosis

Abstract

The growth of human breast tumor cells is regulated through signaling involving cell surface growth factor receptors and nuclear receptors of the steroid/thyroid/retinoid receptor gene family. Retinoic acid receptors (RARs), members of the steroid/thyroid hormone receptor gene family, are ligand-dependent transcription factors, which have in vitro and in vivo growth inhibitory activity against breast cancer cells. RAR-agonists inhibit the proliferation of many human breast cancer cell lines, particularly those whose growth is stimulated by estradiol (E2) or growth factors. Additionally, RAR-agonists and synthetic retinoids such as Ferentinide have been shown to induce apoptosis in malignant breast cells but not normal breast cells. To better define the genes involved in RAR-mediated growth inhibition of breast cancer cells, we used oligonucleotide microarray analysis to create a database of genes that are potentially regulated by RAR-agonists in breast cancer cells. We found that PDCD4 (programmed cell death 4), a tumor suppressor gene presently being evaluated as a target for chemoprevention, was induced about three-fold by the RARalpha-selective agonist Am580, in T-47D breast cancer cells. RAR pan-agonists and Am580, but not retinoid X receptors (RXR)-agonists, stimulate the expression of PDCD4 in a wide variety of retinoid-inhibited breast cancer cell lines. RAR-agonists did not induce PDCD4 expression in breast cancer cell lines, which were not growth inhibited by retinoids. We also observed that antiestrogen and the HER-2/neu antagonist, Herceptin (Trastuzumab), also induced PDCD4 expression in T-47D cells, suggesting that PDCD4 may play a central role in growth inhibition in breast cancer cells. Transient overexpression of PDCD4 in T-47D (ER+, RAR+) and MDA-MB-231 (ER-, RAR-) cells resulted in apoptotic death, suggesting a role for PDCD4 in mediating apoptosis in breast cancer cells. PDCD4 protein expression has previously been reported in small ductal epithelium of normal breast. To date, there has been no report of induction of PDCD4 expression by RAR-agonists, antiestrogen or HER2/neu antagonist in breast cancer cells and its potential role in apoptosis in these cells.

Involvement of programmed cell death 4 in transforming growth factor-β1-induced apoptosis in human hepatocellular carcinoma

“…We have observed that PDCD4 expression was upregulated in Hep3B but rarely in HepG2 cells by TGF-b1 treatment (unpublished data). Recently, Afonia et al (2004) have reported that PDCD4 overexpression induced apoptosis PDCD4 in TGF-b1-induced apoptosis H Zhang et al of breast cancer cells, indicating the presence of PDCD4-mediated apoptotic pathway in other cell types. In our present data, PDCD4-antisense expression was less effective for the recovery of cell growth inhibited by TGF-b1 than for that by Smad7 (compare Figures 6b and 8b) despite PDCD4 expression was almost depressed by the antisense construct.…”

“…H Zhang et al gene expression is controlled by interleukins in NK cells (Azzoni et al, 1998) and upregulated by Vitamin A in breast cancer cells (Afonia et al, 2004). In chicken cells, PDCD4 gene expression is regulated by the transcription factor, myb-1 (Schlichter et al, 2001a, b).…”

Novel retinoic acid metabolism blocking agents have potent inhibitory activities on human breast cancer cells and tumour growth

“…Because ATRA and most retinoids control cell proliferation via apoptosis among several other mechanisms in a variety of cancers Toma et al, 1997;Kotake-Nara et al, 2002;Afonja et al, 2004;Simeone and Tari, 2004) and also because of the cell cycle analysis data that suggests accumulation of cell in the sub-G phase, the apoptotic potential of our RAMBAs was evaluated. Retinoic acid metabolism blocking agents-induced apoptosis in MCF-7 and T47D cells was examined in three independent experiments with ATRA and 4-HPR as positive controls.…”

Pdcd4 directly binds the coding region of c-myb mRNA and suppresses its translation

“…Pdcd4 was initially shown to suppress tumor development in an in vitro mouse keratinocyte model of tumor promotion (Cmarik et al, 1999). More recently, decreased expression of Pdcd4 has been implicated in the development and progression of human lung, colon, liver and breast cancer (Chen et al, 2003;Afonja et al, 2004;Zhang et al, 2006;Mudduluru et al, 2007). Pdcd4 expression is controlled by multiple mechanisms.…”