Apoptosis-like cell death of human breast cancer cell line MCF-7 induced by buprenorphine hydrochloride

Apoptotic-like tumor cells and apoptotic neutrophils in mitochondrion-rich gastric adenocarcinomas: a comparative study with light and electron microscopy between these two forms of cell death

Mitochondrion-rich adenocarcinomas represent a rare variant of gastric adenocarcinomas composed predominantly of columnar adenocarcinoma cells with eosinophilic cytoplasm, a strong supranuclear immunoreactivity for antimitochondrial antibody, and a marked neutrophil infiltration associated to tumor cell death. The purpose of this work is to investigate, using correlated light and electron microscopy, mitochondrion-rich gastric adenocarcinomas focusing on the nature of the death in neoplastic cells and in infiltrating neutrophils. Adenocarcinoma cells, single or in small clusters, showed convoluted nuclei, irregularly condensed chromatin, loss of microvilli, and nuclear envelope dilatation. No nuclear fragmentation was observed in these dying cells and the plasma membrane did not show signs of disruption. These ultrastructural findings represent intermediate aspects between apoptosis and necrosis and are compatible with apoptosis-like programmed cell death. By contrast, some infiltrating neutrophils showed ultrastructural signs of classic apoptosis such as chromatin condensation into compact geometric (globular, crescentshaped) figures, tightly packed cytoplasmic granules and intact cell membrane. Our study provides ultrastructural evidence of apoptosislike tumour cell death in mitochondrion-rich gastric carcinomas and confirms that stereotyped outcome either as apoptosis or necrosis of tumor cells cannot always be expected in human neoplasms.

Expression of the Polyubiquitin Gene Early in the Buprenorphine Hydrochloride-induced Apoptosis of NG108-15 Cells

To clone genes expressed early in the buprenorphine hydrochloride (Bph)-induced apoptosis of NG108-15 nerve cells, we adopted a previously reported rapid and simple differential display (DD) cloning procedure. Complementary DNA was generated from differentially expressed mRNAs by reverse transcription (RT) using a fully degenerate 6-mer oligonucleotide as the primer. PCR amplification was then conducted using a combination of three arbitrary but defined 10-bp nucleotide primers. The differentially generated DNA fragments were detected by agarose gel electrophoresis, and 9 were excised from the gel and subcloned into a sequencing vector. Three DNAs that were specifically expressed upon Bph-induced apoptosis of NG108-15 cells were sequenced. Their specific expression was then confirmed by reverse-transcription PCR. One was identified as the mouse polyubiquitin gene c, and the others remain unidentified. Northern and western blots indicated the transcription and translation of polyubiquitin early in Bph-induced apoptosis. The polyubiquitination of apoptotic cellular proteins was also confirmed.

Cooperation of metallothionein and zinc transporters for regulating zinc homeostasis in human intestinal Caco-2 cells

This investigation examined the effects of zinc status on cell proliferation and the synergic roles of the metallothionein (MT) and zinc transporter (ZnT) in the human colon adenocarcinoma cell line Caco-2. Cells were treated with 0 to 300 micromol/L ZnSO(4) or 0 to 10 micromol/L N,N,N',N'-tetrakis(2-phridylmethyl) ethylenediamine (TPEN). Cell proliferation was determined by MTT assay and apoptotic cells detected by flow cytometry (Hoechst 33258 dye). mRNA expression of MT1; ZnT1; zrt, irt-like protein 1, 4 (ZIP1, 4); and divalent metal transporter (DMT1) were determined by the reverse transcription polymerase chain reaction or real-time polymerase chain reaction. The results showed that either high or low zinc could inhibit the cell proliferation. The number of apoptotic cells increased with incremental increases in the concentrations of ZnSO(4) and TPEN. The mRNA expression of ZnT1 and MT1 responded significantly after 6 and 12 hours with 200 micromol/L zinc treatment, respectively, and increased gradually with zinc levels from 0 to 200 micromol/L. Compared with the unchanged ZIP1 mRNA expression, ZIP4 was closely dependent on TPEN treatment duration and concentration. The DMT1 mRNA expression was upregulated time-dependently but not concentration-dependently in the late TPEN treatment duration. The results suggest that ZIP4 and DMT1 mRNA expressions are susceptible to low extracellular zinc concentration and upregulated to enhance zinc absorption, whereas the ZnT1 and MT1 act as the key regulators under high zinc conditions to enhance the intracellular zinc efflux to maintain zinc homeostasis. We propose that in response to variations in zinc concentration, the cooperated regulative roles of ZnT1, MT1, DMT1, and ZIP4 contribute to zinc homeostasis.

HL-37, a novel anthracene derivative, induces Ca(2+)-mediated apoptosis in human breast cancer cells

HL-37, a novel anthracene derivative, exhibited potent anticancer activity in many kinds of cancer cells. However, the exact mechanism and signaling pathway involved in HL-37-induced apoptosis have not been fully elucidated. Therefore, we explored the mechanisms of HL-37-mediated apoptosis in MCF-7 and MDA-MB-435 human breast cancer cells. When MCF-7 cells or MDA-MB-435 cells were co-incubated with HL-37, the percentage of apoptotic cell and S phase of cell cycle was markedly increased. In addition, a rise in intracellular calcium levels, ROS production, phosphorylation of JNK and activation of calpain were found in both MCF-7 cells and MDA-MB-435 cells after exposure to HL-37. With the HL-37-mediated reduction of mitochondrial membrane potential, cytochrome c was released from mitochondria to cytosol. Moreover, HL-37 strongly induced cleavage of caspase-4, caspase-9, as well as caspase-3 in MDA-MB-435 cells, whereas, activation of caspase-4, caspase-9 and caspase-7 but not caspase-3 was detected in MCF-7 cells. These results suggested that HL-37 induced MDA-MB-435 and MCF-7 cells apoptosis via oxidative stress and Ca(2+)/calpain/caspase-4 pathway.

Mixed lineage kinase 3 connects reactive oxygen species to c-Jun NH2-terminal kinase-induced mitochondrial apoptosis in genipin-treated PC3 human prostate cancer cells

It has been reported that genipin, the aglycone of geniposide, induces apoptotic cell death in human hepatoma cells via a NADPH oxidase-reactive oxygen species (ROS)-c-Jun NH(2)-terminal kinase (JNK)-dependent activation of mitochondrial pathway. This continuing work aimed to define that mixed lineage kinase 3 (MLK3) is a key mediator, which connect between ROS and JNK in genipin-induced cell death signaling. In PC3 human prostate cancer cells, genipin stimulated MLK3 activity in concentration- and time-dependent manner. The PC3 cells stably transfected with dominant-negative form of MLK3 was less susceptible to population of the sub-G1 apoptotic cells, activation of caspase, collapse of mitochondrial membrane potential, and release of cytochrome c triggered by genipin, suggesting a crucial role of MLK3 in genipin signaling to apoptotic cell death. Diphenyleneiodonium (DPI), a specific inhibitor of NADPH oxidase, markedly inhibited ROS generation and MLK3 phosphorylation in the genipin-treated cells. Pretreatment with SP0600125, a specific inhibitor of JNK but neither U0126, a specific inhibitor of MEK1/2 nor PD169316, a specific inhibitor of p38 suppressed genipin-induced apoptotic cell death. Notably, both the phosphorylation of JNK and induction of c-Jun induced by genipin were markedly inhibited in PC3-EGFP-MLK3 (K144R) cells expressing a dominant-negative MLK3 mutant. Taken together, our observations suggest genipin signaling to apoptosis of PC3 cells is mediated via activation of ROS-dependent MLK3, which leads to downstream activation of JNK.

Retrovirus-mediated tk gene therapy of implanted human breast cancer in nude mice under the regulation of Tet-On

Tight regulation of the therapeutic gene expression is critical in gene therapy. In this report, a doxycycline (Dox)-regulated retrovirus-mediated gene expression system was used to study the effects of suicide gene therapy on human breast cancer cell line MCF-7 and the nude mice model of implanted human breast cancer. To render the expression of suicide gene under control, we used two pseudoviruses simultaneously, RevTRE/HSVtk and RevTet-On, to infect MCF-7 cells or xenografts of nude mice. When infected by the pseudoviruses and followed by Dox and Ganciclovir (GCV) treatment, MCF-7 cells were arrested at S phase and the growth was suppressed. We then evaluated the antitumor efficiency of this system in vivo through studying the mice bearing human breast cancer xenografts. Compared with control groups, the HSVtk mRNA level increased significantly in tumor tissues, mass of the tumors shrank remarkably, and tumor necrosis features occurred after treatment with Dox and GCV. These data suggest that suicide gene therapy using the Dox-induced Tet-On-controlled HSVtk gene expression system is a feasible method to treat human breast cancer.

Identification of the mitochondrial targeting signal of the human equilibrative nucleoside transporter 1 (hENT1): implications for interspecies differences in mitochondrial toxicity of fialuridine

We have previously shown that the human equilibrative nucleoside transporter 1 (hENT1) is expressed and functional in the mitochondrial membrane and that this expression enhances the mitochondrial toxicity of the nucleoside drug, fialuridine (FIAU) (Lai, Y., Tse, C. M., and Unadkat, J. D. (2004) J. Biol. Chem. 279, 4490-4497). Here we report on identification of the mitochondrial targeting sequence of hENT1. Using confocal microscopy and different truncated and point mutants of hENT1-YFP (yellow fluorescent protein) expressed in Madin-Darby canine kidney cells, we identified amino acid residues Pro(71),Glu(72), and Asn(74) (the PEXN motif) of hENT1 as important in mitochondrial targeting of hENT1. Identification of this mitochondrial targeting sequence provides a possible explanation for the dramatic difference in mitochondrial toxicity of FIAU between humans and rodents. Although the mouse ENT1 (mENT1), expressed in Madin-Darby canine kidney cells, can transport FIAU, confocal microscopy showed that mENT1-GFP (green fluorescent protein) was not localized to the mitochondria. Consistent with this observation, mitochondria isolated from mouse livers did not transport FIAU. Sequence alignment of hENT1, mENT1, and rat ENT1 (rENT1) showed that the PEXN motif of hENT1 was substituted with a PAXS motif in both mENT1 and rENT1. Substitution of PAXS in mENT1 with PEXN (to create mENT1-PEXN-GFP) and of PEXN in hENT1 with PAXS (to create hENT1-PAXS-YFP) resulted in partial mitochondrial localization of mENT1-PEXN-GFP and loss of mitochondrial localization of hENT1-PAXS-YFP. This is the first time that the mitochondrial targeting signal of hENT1 has been identified. Our data suggest that the lack of mitochondrial toxicity of FIAU in mice is due to the lack of mENT1 targeting to and expression in the mitochondria.

Genipin-induced apoptosis in hepatoma cells is mediated by reactive oxygen species/c-Jun NH2-terminal kinase-dependent activation of mitochondrial pathway

Genipin, the aglycone of geniposide, exhibits anti-inflammatory and anti-angiogenic activities. Here we demonstrate that genipin induces apoptotic cell death in FaO rat hepatoma cells and human hepatocarcinoma Hep3B cells, detected by morphological cellular changes, caspase activation and release of cytochrome c. During genipin-induced apoptosis, reactive oxygen species (ROS) level was elevated, and N-acetyl-l-cysteine (NAC) and glutathione (GSH) suppressed activation of caspase-3, -7 and -9. Stress-activated protein kinase/c-Jun NH2-terminal kinase 1/2(SAPK/JNK1/2) but neither MEK1/2 nor p38 MAPK was activated in genipin-treated hepatoma cells. SP600125, an SAPK/JNK1/2 inhibitor, markedly suppressed apoptotic cell death in the genipin-treated cells. The FaO cells stably transfected with a dominant-negative c-Jun, TAM67, was less susceptible to apoptotic cell death triggered by genipin. Diphenyleneiodonium (DPI), an inhibitor of NADPH oxidase, inhibited ROS generation, apoptotic cell death, caspase-3 activation and JNK activation. Consistently, the stable expression of Nox1-C, a C-terminal region of Nox1 unable to generate ROS, blocked the formation of TUNEL-positive apoptotic cells, and activation of caspase-3 and JNK in FaO cells treated with genipin. Our observations imply that genipin signaling to apoptosis of hepatoma cells is mediated via NADPH oxidase-dependent generation of ROS, which leads to downstream of JNK.