We describe here the main natural compounds used in cancer therapy and prevention, the historical aspects of their application and pharmacognosy. Two major applications of these compounds are described: as cancer therapeutics and as chemopreventive compounds. Both natural compounds, extracted from plants or animals or produced by microbes (antibiotics), and synthetic compounds, derived from natural prototype structures, are being used. We also focus on the molecular aspects of interactions with their recognized cellular targets, from DNA to microtubules. Some critical aspects of current cancer chemotherapy are also discussed, focusing on genetics and genomics, and the recent revolutionary theory of cancer: aneuploidy as the primum movens of cancer.

The permeability transition pore (PTP) is a mitochondrial channel whose opening causes the mitochondrial membrane potential (⌬ ) collapse that leads to apoptosis. Some ubiquinone analogues have been demonstrated previously to modulate the PTP open-closed transition in isolated mitochondria and thought to act through a common PTP-binding site rather than through oxidation-reduction reactions. We have demonstrated recently both in vitro and in vivo that the ubiquitous free radical scavenger and respiratory chain coenzyme Q 10 (CoQ 10 ) prevents keratocyte apoptosis induced by excimer laser irradiation more efficiently than other antioxidants. On this basis, we hypothesized that the antiapoptotic property of CoQ 10 could be independent of its free radical scavenging ability and related to direct inhibition of PTP opening. In this study, we have verified this hypothesis by evaluating the antiapoptotic effects of CoQ 10 in response to apoptotic stimuli, serum starvation, antimycin A, and ceramide, which do not generate free radicals, in comparison to control, free radical-generating UVC irradiation. As hypothesized, CoQ 10 dramatically reduced apoptotic cell death, attenuated ATP decrease, and hindered DNA fragmentation elicited by all apoptotic stimuli. This was accompanied by inhibition of mitochondrial depolarization, cytochrome c release, and caspase 9 activation. Because these events are consequent to mitochondrial PTP opening, we suggest that the antiapoptotic activity of CoQ 10 could be related to its ability to prevent this phenomenon.

Purpose: Cannabinoids have been recently proposed as a new family of potential antitumor agents. The present study was undertaken to investigate the expression of the two cannabinoid receptors, CB 1 and CB 2 , in colorectal cancer and to provide new insight into the molecular pathways underlying the apoptotic activity induced by their activation. Experimental Design: Cannabinoid receptor expression was investigated in both human cancer specimens and in the DLD-1 and HT29 colon cancer cell lines. The effects of the CB 1 agonist arachinodyl-2'-chloroethylamide and the CB 2 agonist N-cyclopentyl-7-methyl-1-(2-morpholin-4-ylethyl)-1,8-naphthyridin-4(1H)-on-3-carboxamide (CB13) on tumor cell apoptosis and ceramide and tumor necrosis factor (TNF)-a production were evaluated. The knockdown of TNF-a mRNA was obtained with the use of selective small interfering RNA. Results: We show that the CB 1 receptor was mainly expressed in human normal colonic epithelium whereas tumor tissue was strongly positive for the CB 2 receptor. The activation of the CB 1 and, more efficiently, of the CB 2 receptors induced apoptosis and increased ceramide levels in the DLD-1 and HT29 cells. Apoptosis was prevented by the pharmacologic inhibition of ceramide de novo synthesis. The CB 2 agonist CB13 also reduced the growth of DLD-1 cells in a mouse model of colon cancer. The knockdown of TNF-a mRNA abrogated the ceramide increase and, therefore, the apoptotic effect induced by cannabinoid receptor activation.Conclusions: The present study shows that either CB 1 or CB 2 receptor activation induces apoptosis through ceramide de novo synthesis in colon cancer cells. Our data unveiled, for the first time, thatTNF-a acts as a link between cannabinoid receptor activation and ceramide production.

We previously identified a conserved A ؉ U-rich element (ARE) in the 3-untranslated region of bcl-2 mRNA. We have also recently demonstrated that the bcl-2 ARE interacts with a number of ARE-binding proteins (AUBPs) whose pattern changes during apoptosis in association with bcl-2 mRNA half-life reduction. Here we show that the AUBP AUF1 binds in vitro to bcl-2 mRNA. The results obtained in a yeast RNA three-hybrid system have demonstrated that the 1-257-amino acid portion of p37 AUF1 (conserved in all isoforms), containing the two RNA recognition motifs, also binds to the bcl-2 ARE in vivo. UVC irradiation-induced apoptosis results in an increase of AUF1. Inhibition of apoptosis by a general caspase inhibitor reduces this increase by 2-3-fold. These results indicate involvement of AUF1 in the ARE/ AUBP-mediated modulation of bcl-2 mRNA decay during apoptosis.

The control of mRNA stability is becoming recognized as a crucial point of gene expression regulation. A common element responsible for mRNA decay modulation is the adenine- and uracil-rich element that is found in the 3' untranslated region of numerous mRNAs subjected to fast expression changes in response to various stimuli. Previously we identified a post-transcriptional regulation level for the antiapoptotic bcl-2 gene, which could be involved in t(14;18) lymphoma-associated bcl-2 overexpression. Here we demonstrate that bcl-2 mRNA is endowed with an adenine- and uracil-rich element (ARE) characterized by high evolutionary conservation not only among all chordates examined, but even between chordates and the nematode Caenorhabditis elegans (ced-9 gene). As for other well-established destabilizing AREs, the insertion of the bcl-2 ARE downstream from stable beta-globin mRNA causes an enhanced decay of the beta-globin transcript, which proves its functional role. This possibility is corroborated by the fact that the pathway leading to the modulating activity of bcl-2 ARE is influenced by PKC, since the addition of DAG and TPA markedly attenuated the bcl-2 ARE destabilizing potential. Conversely, it is noteworthy that when C(2)-ceramide is added to the culture medium as the apoptotic agent, the beta-globin transcript harboring the bcl-2 ARE undergoes a dramatic increase in decay. This observation clearly indicates that the destabilizing function of bcl-2 ARE is enhanced by apoptotic stimuli and suggests that this element could be involved in a post-transcriptional mechanism of bcl-2 down-regulation during apoptosis. The half-life of the mRNA of bcl-2 in Jurkat cells is prolonged by PKC stimulation and shortened by C(2)-ceramide addition, strongly supporting the view that bcl-2 mRNA stability plays a physiological role in modulating bcl-2 expression, particularly in its down-regulation during apoptosis. Thus, this element becomes a new candidate for mediating those bcl-2 gene expression changes-from apoptosis-associated down-regulation to tumor-associated overexpression-observed thus far that profoundly influence single cell fate and tissue homeostasis.

Proliferation and differentiation of osteoclasts are regulated by a cytokine system that includes RANKL, which binds 2 receptors: RANK, which activates osteoclast differentiation, and osteoprotegerin (OPG), a decoy receptor that limits RANKL action. We investigated the role of the OPG/ RANKL/RANK network in the pathogenesis of skeletal metastasis in neuroblastoma. Four different neuroblastoma cell lines (NB100, CHP212, SH-SY5Y, SJ-NK-P) showed a large amount of OPG and RANKL transcripts. Soluble RANKL was detectable in all cell lines, but poor release of OPG was observed. SH-SY5Y showed the lowest OPG-to-RANKL ratio and promoted osteoclastic differentiation of FLG29.1 and peripheral mononuclear cells, inducing expression of the osteoclast markers RANK, c-src, c-fos, cathepsin-K and TRAP. SJ-N-KP, which released both OPG and RANKL, did not show the same capability. OPG, neutralizing anti-RANKL antibody and antisense oligonucleotides were evaluated for their ability to inhibit RANKL activity. The neutralizing antibody hampered osteoclastic differentiation by blocking both the juxtacrine and the paracrine activity of RANKL. Our findings confirm that neuroblastoma cells induce osteoclastogenesis via RANKL and suggest that the RANKL expression associated with lack of the decoy receptor OPG could be a peculiarity of some tumors that makes them able to induce metastatic osteolysis. Moreover, our results suggest that RANKL could be a relevant target in the adjuvant therapy of bone metastatic neuroblastoma as proper neutralization revokes completely osteoclastic differentiation. © 2004 Wiley-Liss, Inc. Key words: neuroblastoma; bone metastasis; osteoclast; RANKL; osteoprotegerinMetastasis is the most relevant prognostic factor for survival in neuroblastoma patients, and bone is one of the target organs of metastasis in advanced neuroblastoma. Patients with bone metastasis are classified as stage IV, regardless of other clinical manifestations, since the presence of bone/bone marrow metastasis is responsible for poor prognosis despite high-dose chemotherapy and autologous hematopoietic stem cell transplantation. 1 One possible reason for this ominous prognosis is the difficulty in reaching cancer cells that have colonized the bone/bone marrow microenvironment. This suggests the need for effective therapeutic modalities for patients with skeletal metastases based on a precise understanding of the pathophysiology of bone colonization in neuroblastoma. Two classical theories are generally advocated to explain the invasion of tumor cells in bone, i.e., the soil hypothesis 2 and the circulation theory. 3 The first suggests that proper factors favor the implantation of metastatic cells, including nutrients, oxygen tension, hormonal environment and hydrogen ion concentrations. The second assumes that development of cancer metastases is dependent on the blood volume inside a target organ. This hemodynamic theory alone cannot explain the high frequency of skeletal metastasis from some neoplasms because blood flow in bone is very p...

The treatment of corneal keratocytes with relatively low concentrations of ubiquinone Q10 can prevent apoptosis after ArF excimer laser irradiation. If these findings are confirmed on human keratocytes this treatment could be usefully exploited in the PRK surgical procedure. That might lead to a reduction in the occurrence of haze and curvature regression triggered by programmed cell death.

Hypoxic and chemical hypoxia (antimycin A) commits cultured rat fibroblasts (Rat-1) towards apoptosis, necrosis or an intermediate form of cell death (aponecrosis) depending on the degree of hypoxia. Aponecrosis also occurs in vivo. Here, we demonstrate that c-myc and bcl-2, two proto-oncogenes known to lower or to enhance, respectively, the apoptotic threshold, also affect the type of cell death: apoptosis shifts to aponecrosis and aponecrosis to necrosis, depending on c-myc or bcl-2 expression and the antimycin A concentration (100-400 microM). In cells with basal gene expression, apoptosis shifts to aponecrosis/necrosis at 300 microM antimycin A (middle hypoxia). Overexpression of c-myc markedly increases cumulative cell death in response to antimycin A and lowers the antimycin A concentration required to shift apoptosis to aponecrosis/necrosis from 300 microM to 100 microM (low hypoxia). Overexpression of bcl-2 elicits the opposite effect, decreasing cumulative cell death in response to antimycin A and raising the drug concentration required to shift apoptosis to aponecrosis/necrosis to 400 microM (high hypoxia). The passage from one to the other form of cell death involves various aponecrotic features with observed intermediate aspects between apoptosis and necrosis, a progressive increase in necrotic features being correlated with an increase in antimycin A concentration. The mechanism underlying the various effects of c-myc and bcl-2 on cell-death type has been related to the ability of these genes to counteract, to various extents, the ATP decrease occurring in response to different degrees of chemical hypoxia.