We have synthesized a novel analogue of pancratistatin with comparable anti-cancer activity as native pancratistatin; interestingly, combinatory treatment with tamoxifen yielded a drastic enhancement in apoptotic and autophagic induction by mitochondrial targeting with minimal effect on noncancerous fibroblasts. Thus, JCTH-4 in combination with tamoxifen could provide a safe anti-cancer therapy.
Breast cancer is one of the most common cancers amongst women in North America. Many current anti-cancer treatments, including ionizing radiation, induce apoptosis via DNA damage. Unfortunately, such treatments are non-selective to cancer cells and produce similar toxicity in normal cells. We have reported selective induction of apoptosis in cancer cells by the natural compound pancratistatin (PST). Recently, a novel PST analogue, a C-1 acetoxymethyl derivative of 7-deoxypancratistatin (JCTH-4), was produced by de novo synthesis and it exhibits comparable selective apoptosis inducing activity in several cancer cell lines. Recently, autophagy has been implicated in malignancies as both pro-survival and pro-death mechanisms in response to chemotherapy. Tamoxifen (TAM) has invariably demonstrated induction of pro-survival autophagy in numerous cancers. In this study, the efficacy of JCTH-4 alone and in combination with TAM to induce cell death in human breast cancer (MCF7) and neuroblastoma (SH-SY5Y) cells was evaluated. TAM alone induced autophagy, but insignificant cell death whereas JCTH-4 alone caused significant induction of apoptosis with some induction of autophagy. Interestingly, the combinatory treatment yielded a drastic increase in apoptotic and autophagic induction. We monitored time-dependent morphological changes in MCF7 cells undergoing TAM-induced autophagy, JCTH-4-induced apoptosis and autophagy, and accelerated cell death with combinatorial treatment using time-lapse microscopy. We have demonstrated these compounds to induce apoptosis/autophagy by mitochondrial targeting in these cancer cells. Importantly, these treatments did not affect the survival of noncancerous human fibroblasts. Thus, these results indicate that JCTH-4 in combination with TAM could be used as a safe and very potent anti-cancer therapy against breast cancer and neuroblastoma cells.
PST and similar compounds have been shown to have anti-cancer properties11-15,21. We have previously reported natural PST to destabilize the mitochondria selectively in cancer cells, which thereby induces apoptosis by the release of apoptogenic factors12,14. It is most likely that JCTH-4 acts through the same mechanism; JCTH-4 caused MMP collapse in MCF7 cells as seen with TMRM staining (Fig. 5a), and increased generation of ROS in isolated mitochondria from SH-SY5Y cells (F…
The authors have nothing to disclose.
This work has been supported by the Knights of Columbus Chapter 9671 (Windsor, Ontario), and a CIHR Frederick Banting and Charles Best Canada Graduate Scholarship awarded to Dennis Ma. Thank you to Robert Hodge and Elizabeth Fidalgo da Silva for their assistance with the time-lapse microscopy. Thank you to Katie Facecchia for editing the time-lapse microscopy videos. We would also like to thank Sudipa June Chatterjee and Phillip Tremblay for the critical review of this manuscript. This work is dedicated in memory of Kevin Couvillon who lost his battle against cancer in 2010.
Material Name | Company | Catalogue number |
SH-SY5Y cell line | ATCC | CRL-2266 |
Dulbecco’s Modified Eagles Medium F-12 HAM | Sigma-Aldrich | 51448C |
Fetal bovine serum | Gibco BRL | 16000-044 |
MCF7 cell line | ATCC | HTB-22 |
RPMI-1640 medium | Sigma-Aldrich | R 0883 |
Apparently normal human fetal fibroblast cell line (NFF) | Coriell Institute for Medical Research | AG04431B |
Dulbecco’s Modified Eagle’s Medium, High Glucose medium | Thermo Scientific | SH30022.01 |
Tamoxifen citrate salt | Sigma-Aldrich | T9262 |
35 mm glass bottom culture dishes | MatTek | P35G-014-C |
Leica DMI6000 B inverted microscope | Leica Microsystems | N/A |
Hoechst 33342 dye | Molecular Probes | H3570 |
Leica DM IRB inverted fluorescence microscope | Leica Microsystems | N/A |
Annexin V AlexaFluor-488 | Invitrogen | A13201 |
Trypan Blue solution | Sigma-Aldrich | T8154-20ML |
Haemocytometer | Fisher Scientific | 267110 |
WST-1 reagent | Roche Applied Science | 11644807001 |
Wallac Victor3 1420 Multilabel Counter | PerkinElmer | 1420-011 |
Tetramethylrhodamine methyl ester (TMRM) | Gibco BRL | T-668 |
Glass tissue grinder | Fisher Scientific | K8885300-0002 |
BioRad protein assay | Bio-Rad Laboratories | 500-0001Bottom of Form |
Amplex Red | Invitrogen | A12222 |
Horseradish peroxidase (HRP) | Sigma-Aldrich | P8125 |
SpectraMax Gemini XPS | Molecular Devices | 3126666 |
Anti-LC3 antibody raised in rabbit | Novus Biologicals | NB100-2220 |
Anti-mouse HRP-conjugated secondary antibody | Abcam | ab6728 |
Anti-rabbit HRP-conjugated secondary antibody | Abcam | ab6802 |
Chemiluminescence peroxidase substrate | Sigma-Aldrich | CPS160 |
Monodansylcadaverine | Sigma-Aldrich | 30432 |