The bisphosphonate zoledronic acid impairs membrane localisation and induces cytochrome c release in breast cancer cells

Abstract

Bisphosphonates are well established in the management of cancer-induced bone disease. Recent studies have indicated that these compounds have direct inhibitory effects on cultured human breast cancer cells. Nitrogen-containing bisphosphonates including zoledronic acid have been shown to induce apoptosis associated with PARP cleavage and DNA fragmentation. The aim of this study was to identify the signalling pathways involved. Forced expression of the anti-apoptotic protein bcl-2 attenuated bisphosphonate-induced loss of cell viability and induction of DNA fragmentation in MDA-MB-231 cells. Zoledronic acid-mediated apoptosis was associated with a time and dose-related release of mitochondrial cytochrome c into the cytosol in two cell lines. Rescue of cells by preincubation with a caspase-3 selective inhibitor and demonstration of procaspase-3 cleavage products by immunoblotting suggests that at least one of the caspases activated in response to zoledronic acid treatment is caspase-3. In both MDA-MB-231 and MCF-7 breast cancer cells, zoledronic acid impaired membrane localisation of Ras indicating reduced prenylation of this protein. These observations demonstrate that zoledronic acidmediated apoptosis is associated with cytochrome c release and consequent caspase activation. This process may be initiated by inhibition of the enzymes in the mevalonate pathway leading to impaired prenylation of key intracellular proteins including Ras.

Antitumor Effects of Aminobisphosphonates on Renal Cell Carcinoma Cell Lines

“…Inhibition of caspase 3 prevents osteoclast apoptosis. In keeping with previous reports in breast cancer lines, we found clear evidence that only ZOL was capable of caspase 3 activation.in our cell line (27).…”

“…After ZOL exposure however, the distribution of MSH2 protein changed markedly and adopted a peri-nuclear and cytoplasmic distribution, figure 7. Similarly, for PARP-1, its fulllength form p116 exhibited an 81% decrease in the ZOL-treated sample and more than 400% increase in the PAM-treated sample, indicating a higher degree of (27), prostate cancer (28) and multiple myeloma (33), pancreas (24). We found evidence of significant antiproliferative effects in a range 10-100 mol, consistent with previous studies.…”

“…There are reports of synergy with chemotherapy and biological therapies (25) (26) A number of studies have reported on the effects of BP directly on growth and survival of cancer cell lines derived from solid malignancies. ZOL induces a reduction in cell viability, increased apoptotic death and downregulation of bcl-2, p21ras delocalization from the cell membrane and proteolytic cleavage of PARP, indicating direct antitumour effects in breast cancer cell lines (27). In prostate cancer, ZOL inhibited cell proliferation by induction of cell death and /or cytostasis in vitro (28).…”

Mevalonate pathway intermediates downregulate zoledronic acid-induced isopentenyl pyrophosphate and ATP analog formation in human breast cancer cells

“…IPP is further metabolized endogenously into an ATP analogue ApppI, which is able to induce apoptosis in cells by inhibiting mitochondrial adenine nucleotide translocase (ANT), causing also a loss of the mitochondrial membrane potential [17,20]. Several studies have demonstrated that the interruption of the protein prenylation is a major contributor to the anticancer action of N-BPs [7,36,37], whereas the role and the significance of the additional mechanism of action, accumulation of IPP/ApppI, is less clear.…”

Advances in the use of bisphosphonates in the prostate cancer setting

“…[33][34][35][36][37] Work in our centre with breast cancer cells provided early evidence that inhibition of the mevalonate pathway was again central to the Bisphosphonates in the prostate cancer setting JP Coxon et al observed apoptotic effects. 38 We recently published similar results for various prostate cancer cell lines, 35 and provided evidence that the resultant apoptosis was dependent on the activation of caspases. Unpublished work in our laboratory has confirmed an apoptotic effect on prostate cancer cells at concentrations that are likely to be physiologically relevant.…”