Investigation of Gallic Acid Induced Anticancer Effect in Human Breast Carcinoma MCF‐7 Cells

Gallic acid (GA), a polyhydroxylphenolic compound abundantly distributed in plants, fruits, and foods, has been reported to have various biological activities including an anticancer effect. In this study, we extensively investigated the anticancer effect of GA in human breast carcinoma MCF‐7 cells. Our study indicated that treatment with GA resulted in inhibition of proliferation and induction of apoptosis in MCF‐7 cells. Then, the molecular mechanism of GA's apoptotic action in MCF‐7 cells was further investigated. The results revealed that GA induced apoptosis by triggering the extrinsic or Fas/FasL pathway as well as the intrinsic or mitochondrial pathway. Furthermore, the apoptotic signaling induced by GA was amplified by cross‐link between the two pathways. Taken together, our findings may be useful for understanding the mechanism of action of GA on breast cancer cells and provide new insights into the possible application of such compound and its derivatives in breast cancer therapy.     

Design,Synthesis, and Cytotoxic Activity of 3‐Aryl‐N‐hydroxy‐2‐(sulfonamido)propanamides in HepG2, HT‐1080, KB,and MCF‐7 Cells

A new series of (sulfonamido)propanamides ( 6a1 – 6a13 , 6b1 – 6b15 , 7c1 – 7c5 , 6d1 – 6d5 , 6e1 – 6e6 ) was designed and synthesized. All the synthesized compounds were characterized by NMR and mass spectrometry. The target compounds were evaluated for their in vitro cytotoxic activity against hepatocellular carcinoma (HepG2), fibrosarcoma (HT‐1080), mouth epidermal carcinoma (KB), and breast adenocarcinoma (MCF‐7) cell lines with the sulforhodamine B (SRB) assay, with gemcitabine and mitomycin C as positive controls. Most of these compounds exhibit a more potent cytotoxic effect than the positive control group on various cancer cell lines and the most potent compound, 6a7 , shows the IC₅₀ values of 29.78±0.516 μm , 30.70±0.61 μm , and 64.89±3.09 μm in HepG2, HT‐1080, KB, and MCF‐7 cell lines, respectively. Thus, these compounds with potent cytotoxic activity have potential for development as new chemotherapy agents.     

Activation of a Cysteine Protease in MCF-7 and T47D Breast Cancer Cells during β-Lapachone-Mediated Apoptosis

β-Lapachone (β-lap) effectively killed MCF-7 and T47D cell lines via apoptosis in a cell-cycle-independent manner. However, the mechanism by which this compound activated downstream proteolytic execution processes were studied. At low concentrations, β-lap activated the caspase-mediated pathway, similar to the topoisomerase I poison, topotecan; apoptotic reactions caused by both agents at these doses were inhibited by zVAD-fmk. However at higher doses of β-lap, a novel non-caspase-mediated “atypical” cleavage of PARP (i.e., an 60-kDa cleavage fragment) was observed. Atypical PARP cleavage directly correlated with apoptosis in MCF-7 cells and was inhibited by the global cysteine protease inhibitors iodoacetamide and N-ethylmaleimide. This cleavage was insensitive to inhibitors of caspases, granzyme B, cathepsins B and L, trypsin, and chymotrypsin-like proteases. The protease responsible appears to be calcium-dependent and the concomitant cleavage of PARP and p53 was consistent with a β-lap-mediated activation of calpain. β-Lap exposure also stimulated the cleavage of lamin B, a putative caspase 6 substrate. Reexpression of procaspase-3 into caspase-3-null MCF-7 cells did not affect this atypical PARP proteolytic pathway. These findings demonstrate that β-lap kills cells through the cell-cycle-independent activation of a noncaspase proteolytic pathway.     

Activation of c-Neu Tyrosine Kinase by o,p′-DDT and β-HCH in Cell-Free and Intact Cell Preparations from MCF-7 Human Breast Cancer Cells

It has been suggested that there is a positive correlation between increased incidence of breast cancer and the presence of organochlorine residues such as DDT and HCH in breast tissues in the United States. To study possible biochemical links between these two parameters, we have examined the effect of o,p′-DDT, the most estrogenic congener of the DDT family of chemicals and β-HCH on protein phosphorylation activities in MCF-7, a line derived from human breast cancer cells. Both of these organochlorine chemicals were found to be potent activators of protein kinases. Among kinases activated, protein tyrosine kinases (PTK) appear to be most affected as judged by the antagonistic action of genistein, a class-specific PTK inhibitor. Moreover, these organochlorines were found to activate PTK even under cell-free conditions, indicating that they are likely to interact directly with the target protein tyrosine kinase. As a result of immunoprecipitation with specific antibodies, and testing on the action of these organochlorines, we could show that the major kinase activated by o,p′-DDT is c-Neu (= c-erbB2 product protein). The concentrations of these organochlorines required to activate c-Neu were extremely low (0.1–1 nM range), whereas an inactive analog p,p′-DDT showed no stimulatory property even at 100 nM. Such an action of these organochlorine compounds were not antagonized by the presence of 1 μM tamoxifen, indicating that it is not mediated through the estrogen receptor. In addition, their c-Neu activating actions were specifically antagonized by a c-Neu antibody known to interact with the extracellular domain of c-Neu only without affecting the EGF receptor. Moreover, these chemicals did not cause downregulation of the EGF receptor during the 72 hour test period. Together these data indicate that the action of these chemicals on c-Neu kinase is very specific. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 12: 83–92, 1998