Identification of a Novel Pathway That Selectively Modulates Apoptosis of Breast Cancer Cells

Abstract

Expression of the nuclear receptor interacting factor 3 (NRIF3) coregulator in a wide variety of breast cancer cells selectively leads to rapid caspase-2–dependent apoptotic cell death. A novel death domain (DD1) was mapped to a 30– amino acid region of NRIF3. Because the cytotoxicity of NRIF3 and DD1 seems to be cell type–specific, these studies suggest that breast cancer cells contain a novel “death switch” that can be specifically modulated by NRIF3 or DD1. Using an MCF-7 cell cDNA library in a yeast two-hybrid screen, we cloned a factor that mediates apoptosis by DD1 and refer to this factor as DD1-interacting factor-1 (DIF-1). DIF-1 is a transcriptional repressor that mediates its effect through SirT1, and this repression is attenuated by the binding of NRIF3/DD1. DIF-1 expression rescues breast cancer cells from NRIF3/DD1-induced apoptosis. Small interfering RNA (siRNA) knockdown of DIF-1 selectively leads to apoptosis of breast cancer cells, further suggesting that DIF-1 plays a key role in NRIF3/DD1-mediated apoptosis. A protein kinase A inhibitor (H89) also elicits apoptosis of breast cancer cells but not of the other cell types examined, and DIF-1 also protects these cells from H89-mediated apoptosis. In addition, H89 incubation results in a rapid increase in NRIF3 levels and siRNA knockdown of NRIF3 protects breast cancer cells from H89-mediated apoptosis. Our results indicate that DIF-1 plays a key role in breast cancer cell survival and further characterizing this pathway may provide important insights into developing novel therapies to selec tively target breast cancer cells for apoptosis.

A Novel Transcription Complex That Selectively Modulates Apoptosis of Breast Cancer Cells through Regulation of FASTKD2

“…DIF-1 was found to be identical to interferon regulating factor-2 binding protein 2A (IRF-2BP2A), which had been reported to act as a repressor which mediated the inhibitory effect of IRF-2 on gene expression (3). We found that DIF-1 appears to act as a repressor through Sirt1, a class III histone and protein deacetylase (34). NRIF3/DD1 acts by binding to DIF-1 and reversing the repression mediated by DIF-1 (34).…”

“…Expression of NRIF3 specifically and rapidly leads to caspase-2-dependent apoptosis in breast cancer cells but not other cell types (5,21,34). Time lapse photography documented changes characteristic of apoptosis (5).…”

“…In a subsequent study we cloned an intracellular target of NRIF3/DD1 and refer to this factor as DD1 interacting factor-1 (DIF-1) (34). DIF-1 was found to be identical to interferon regulating factor-2 binding protein 2A (IRF-2BP2A), which had been reported to act as a repressor which mediated the inhibitory effect of IRF-2 on gene expression (3).…”

Evaluation and comparison of alpha- and beta-amanitin toxicity on MCF-7 cell line

“…The α-AMA-induced apoptosis is associated with severe liver damage, especially in the early stages of poisoning (18); however, a nonlethal dose of α-AMA prevents DD1 (a novel death domain)-mediated apoptosis by disrupting the protein synthesis. In fact, this process is under investigation in cell culture experiments either alone or in combination with other medicines for the treatment of cancer (19)(20)(21). The cytotoxic effect of β-AMA has been shown in a few studies, but the stability of β-AMA has not been investigated in detail (22)(23)(24).…”

The evaluation and comparison of the alpha and beta amanitin toxicity on MCF-7 cell line

“…This result was not consistent with earlier hepatocyte culture studies (2), and the putative reason may be the cell type. It was also reported that α-AMA has antiapoptotic characteristics, which could also be the reason (19,20).…”