title: Quinuclidinone derivative 6 induced apoptosis in human breast cancer cells via sphingomyelinase and JNK signaling.
abstract: Novel quinuclidinone derivatives have been previously reported by our laboratory. In this study, we investigated the impact of two novel quinuclidinone derivatives 4 and 6 on apoptotic signaling in breast cancer cells (MCF-7) and their normal counterparts (MCF-12a). Our data revealed  that derivatives 4 and 6 reduced proliferation and induced apoptosis in breast cancer cells. However, derivative 6 was less cytotoxic to normal breast epithelial cells than breast cancer cells; therefore, we focused on derivative 6 for further investigation. Flow cytometric analysis showed  that quinuclidinone derivative 6 reduced the percentage of MCF-7 cells in G(2)/M which is confirmed by increased expression levels of cyclin B, while it arrests MCF12a in G1 phase judging from increased p21. Quinuclidinone derivative 6 increased expression levels of p53 and Bax at  both protein and mRNA levels and reduced expression level of Mdm2, Bcl2, Akt and Bcl-XL It also increased mitochondrial apoptotic pathways by activating release of cytochrome c which is consistent with activation of caspase-9 as confirmed by caspase-9 inhibitor LEHD-CHO. Finally, it increased  sphingomyelinase signaling and ceramide formation as well as its downstream targets ERK1/2, p38, and JNK. Inhibition of ERK1/2 with PD98059 exerted little effect on the derivative 6-induced apoptosis and p38 inhibition with SB203580 slightly lessened apoptosis, whereas inhibition of JNK with  SP600125 markedly suppressed derivative 6-induced apoptosis. These results indicate that derivative-6 induced the activation of sphingomyelinase signaling and that JNK played a pivotal role in induction of apoptosis in human breast cancer cells. In vivo studies and molecular docking  experiments are now in progress for further anticancer investigations.
authors.affiliation: Biochemistry department, Faculty of Science, Alexandria University, Egypt. ahmed.malki@gmail.com
authors.forename: Ahmed
authors.initials: A
authors.lastname: Malki
authors.forename: El Sayed
authors.initials: el S
authors.lastname: El Ashry
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002518:Ceramides / Q000378:metabolism; D019926:Cyclin B / Q000096:biosynthesis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D020935:MAP Kinase Signaling System / Q000187:drug effects* / Q000502:physiology; D011812:Quinuclidines / Q000494:pharmacology* / Q000627:therapeutic use; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013108:Sphingomyelin Phosphodiesterase / Q000235:genetics / Q000378:metabolism*
chemical_list: D002518:Ceramides; D019926:Cyclin B; D011812:Quinuclidines; D013108:Sphingomyelin Phosphodiesterase