Inhibition of SIRT1 deacetylase and p53 activation uncouples the anti-inflammatory and chemopreventive actions of NSAIDs.

BACKGROUND: Nonsteroidal anti-inflammatory drugs (NSAIDs) have been proposed as chemopreventive agents for many tumours; however, the mechanism responsible for their anti-neoplastic activity remains elusive and the side effects due to cyclooxygenase (COX) inhibition prevent this clinical application. METHODS: Molecular biology, in silico, cellular and in vivo tools, including innovative in vivo imaging and classical biochemical assays, were applied to identify and characterise the COX-independent anti-cancer mechanism of NSAIDs. RESULTS: Here, we show that tumour-protective functions of NSAIDs and exisulind (a sulindac metabolite lacking anti-inflammatory activity) occur through a COX-independent mechanism. We demonstrate these NSAIDs counteract carcinogen-induced proliferation by inhibiting the sirtuin 1 (SIRT1) deacetylase activity, augmenting acetylation and activity of the tumour suppressor p53 and increasing the expression of the antiproliferative gene p21. These properties are shared by all NSAIDs except for ketoprofen lacking anti-cancer properties. The clinical interest of the mechanism identified is underlined by our finding that p53 is activated in mastectomy patients undergoing intraoperative ketorolac, a treatment associated with decreased relapse risk and increased survival. CONCLUSION: Our study, for the first-time, links NSAID chemopreventive activity with direct SIRT1 inhibition and activation of the p53/p21 anti-oncogenic pathway, suggesting a novel strategy for the design of tumour-protective drugs.

Cell cycle dependent oscillatory expression of estrogen receptor-α links Pol II elongation to neoplastic transformation.

Decades of studies provided a detailed view of the mechanism of estrogen receptor-α (ERα) regulated gene transcription and the physio-pathological relevance of the genetic programs controlled by this receptor in a variety of tissues. However, still limited is our knowledge on the regulation of ERα synthesis. Preliminary observations showed that the expression of ERα is cell cycle regulated. Here, we have demonstrated that a well described polymorphic sequence in the first intron of ERα (PvuII and XbaI) has a key role in regulating the ERα content in cycling cells. We have shown that the RNA Pol II (Pol II) elongation is blocked at the polymorphic site and that the proto-oncogene c-MYB modulates the release of the pausing polymerase. It is well known that the two SNPs are associated to an increased risk, progression, survival and mortality of endocrine-related cancers, here we have demonstrated that the c-MYB-dependent release of Pol II at a specific phase of the cell cycle is facilitated by the px haplotype, thus leading to a higher ERα mitogenic signal. In breast cancer, this mechanism is disrupted when the hormone refractory phenotype is established; therefore, we propose this oscillator as a novel target for the development of therapies aimed at sensitizing breast cancer resistant to hormonal treatments. Because PvuII and XbaI were associated to a broad range physio-pathological conditions beside neoplastic transformation, we expect that the ERα oscillator contributes to the regulation of the estrogen signal in several tissues.

Bioluminescence imaging of estrogen receptor activity during breast cancer progression.

Estrogen receptors (ER) are known to play an important regulatory role in mammary gland development as well as in its neoplastic transformation. Although several studies highlighted the contribution of ER signaling in the breast transformation, little is known about the dynamics of ER state of activity during carcinogenesis due to the lack of appropriate models for measuring the extent of receptor signaling in time, in the same animal. To this aim, we have developed a reporter mouse model for the non-invasive in vivo imaging of ER activity: the ERE-Luc reporter mouse. ERE-Luc is a transgenic mouse generated with a firefly luciferase (Luc) reporter gene driven by a minimal promoter containing an estrogen responsive element (ERE). This model allows to measure receptor signaling in longitudinal studies by bioluminescence imaging (BLI). Here, we have induced sporadic mammary cancers by treating systemically ERE-Luc reporter mice with DMBA (9,10-dimethyl 1,2-benzanthracene) and measured receptor signaling by in vivo imaging in individual animals from early stage until a clinically palpable tumor appeared in the mouse breast. We showed that DMBA administration induces an increase of bioluminescence in the whole abdominal area 6 h after treatment, the signal rapidly disappears. Several weeks later, strong bioluminescence is observed in the area corresponding to the mammary glands. In vivo and ex vivo imaging analysis demonstrated that this bioluminescent signal is localized in the breast area undergoing neoplastic transformation. We conclude that this non-invasive assay is a novel relevant tool to identify the activation of the ER signaling prior the morphological detection of the neoplastic transformation.

In vivo imaging of cell proliferation for a dynamic, whole body, analysis of undesired drug effects.

Noninvasive in vivo imaging offers a novel approach to preclinical studies opening the possibility of investigating biological events in the spatiotemporal dimension (eg, in any district of the body in time). Toxicological analysis may benefit from this novel approach through precise identification of the time and the target organs of toxicity manifestations, and assessment of the reversibility of toxic insults. The current limitation for routine application of this technology is the lack of appropriate surrogate markers for imaging toxicological events. Here, we demonstrate that in vivo imaging of a proliferation marker is capable of measuring the reduction of cell proliferation due to genotoxic/apoptotic agents, γ rays or antineoplastic drugs, or the increased proliferation associated with the inflammatory and regenerative reactions occurring after a toxic insult. A number of tools are currently available for imaging proliferation in preclinical and clinical settings, however our data provide a novel way to translate the evidence of toxic effects obtained in preclinical animal studies, by the direct, noninvasive measure of dividing cells in humans.

Reporter mice for the study of long-term effects of drugs and toxic compounds.

Noninvasive, imaging-based methodologies provide for the first time the possibility to spatio-temporally investigate physiopathological events and long-term effects of drug administration of exposure to environmental and alimentary toxic compounds. Hence, this novel methodology could enable us to measure the dynamics of specific molecular pathways in live animals. In the last few years, animals, particularly mice, were genetically modified to respond to a specific stimulus with the production of proteins, named "reporters," that are easily detected and quantitated by in vivo and ex vivo imaging. These "reporter mice" are gradually being applied to the pharmaco-toxicological research. In the generation of a reporter mouse useful for pharmaco-toxicological studies several elements need to be considered in the selection of the reporter system: the half-life of proteins should be compatible with the necessities of the study to assess the onset and the termination of the stimulus of interest, in all tissues the response should be proportional to the given stimulus, and the imaging modalities requested for reporter measurements should be applicable to high-throughput screening. Bioluminescence-based imaging (BLI) in small animals has the advantage over other modalities that does not require too sophisticated equipment or specifically and highly trained personnel, and furthermore may be carried out at a relative rapidity and low cost; for these reasons several luciferases have been developed for in vivo imaging applications and used in the generation of reporter mice. We here describe a BLI-based reporter mouse created to respond to estrogenic stimuli, which has been applied to the study of female physiopathology as well as for the identification of the effects of selective drugs or toxic compounds present in the environment and in the alimentary chain.