Simona Dinicola

Evidence for a biphasic apoptotic pathway induced by melatonin in MCF-7 breast cancer cells.

Abstract:  Previous investigations demonstrated that melatonin exerts an oncostatic action on estrogen‐responsive breast cancer, both in vitro and in vivo. Nevertheless, the pro‐apoptotic effect of melatonin is still a matter of debate. An experimental study was undertaken to focus on melatonin‐related apoptosis and to identify the apoptotic pathways involved. Whole cell‐count, flow‐cytometry analysis and proteins involved in apoptotic pathways [p53, p73, murine double minute 2 (MDM2), caspases‐9,‐7,‐6, cleaved‐poly ADP ribose polymerase (PARP), Bcl‐2, Bax and apoptotic inducing factor (AIF)] were investigated in human MCF‐7 breast cancer cells treated with physiological (1 nM) concentration of melatonin. Melatonin exerts a significant growth‐inhibitory effect on MCF‐7 cells, becoming evident after 72 hr and thereafter increasing linearly up to 144 hr. In this model, the growth‐inhibition is transforming growth factor beta 1 (TGFβ1)‐dependent and it might be reversed by adding an anti‐TGFβ1 antibody. Melatonin induces a significant rise in apoptotic rate, at both 24 and 96 hr. The anti‐TGFβ1 antibody almost completely suppresses melatonin‐related late apoptosis; however, early apoptosis is unaffected. Early programmed cell death is associated with a significant increase in the p53/MDM2 ratio and in AIF release, without modifications in caspase activity or cleaved‐PARP levels. Activated caspases‐9 and ‐7 and cleaved‐PARP increased significantly at 96 hr, concomitantly with a down‐regulation of the Bcl‐2/Bax ratio. These data suggest that two distinct apoptotic processes are triggered by melatonin in MCF‐7 cells: an early, TGFβ1 and caspase‐independent response, and a late apoptotic TGFβ1‐dependent process in which activated‐caspase‐7 is likely to be the terminal effector.

Melatonin and vitamin D3 synergistically down-regulate Akt and MDM2 leading to TGFβ-1-dependent growth inhibition of breast cancer cells.

Abstract:  Melatonin and vitamin D3 inhibit breast cancer cell growth and induce apoptosis, but they have never been combined as a breast cancer treatment. Therefore, we investigated whether their association could lead to an enhanced anticancer activity. In MCF‐7 breast cancer cells, melatonin together with vitamin D3, induced a synergistic proliferative inhibition, with an almost complete cell growth arrest at 144 hr. Cell growth blockade is associated to an activation of the TGFβ‐1 pathway, leading to increased TGFβ‐1, Smad4 and phosphorylated‐Smad3 levels. Concomitantly, melatonin and D3, alone or in combination, caused a significant reduction in Akt phosphorylation and MDM2 values, with a consequent increase of p53/MDM2 ratio. These effects were completely suppressed by adding a monoclonal anti‐TGFβ‐1 antibody to the culture medium. Taken together, these results indicate that cytostatic effects triggered by melatonin and D3 are likely related to a complex TGFβ‐1‐dependent mechanism, involving down‐regulation of both MDM2 and Akt‐phosphorylation.

Nicotine stimulates proliferation and inhibits apoptosis in colon cancer cell lines through activation of survival pathways

BACKGROUND Colorectal cancer is one of the leading causes of cancer-related death throughout the world, and the risk to develop this malignant disease seems to be associated with long-term cigarette smoking. Nicotine, one of the major components of cigarette smoking, can stimulate cell proliferation and suppress apoptosis both in normal cells and in several human cancer cell lines derived from various organs. However, although nicotine appears to have a role in stimulating cell proliferation of colon cancer cells, there is no information on its role in inhibiting apoptosis in these cells. MATERIALS AND METHODS Human colorectal cancer cell lines Caco-2 and HCT-8 were treated with 1 μM nicotine alone or in combination with 1 μM α-BTX in complete or in serum free medium. Cell proliferation and apoptosis were determined by cell count performed with a cell counter and by cytofluorimetric assay respectively. PI3K/Akt and PKC/ERK1/2 pathways, survivin, and P-Bcl2 (Ser70) were investigated by Western blot analysis. RESULTS Nicotine induced an increase in cell proliferation and a decrease of apoptosis in Caco-2 and HCT-8 cells. Both cell growth and apoptosis appear to be mediated by α7-nicotinic acetylcholine receptors, since treatment with α-Bungarotoxin inhibited these processes. Nicotine induced a statistically significant increase in the expression of PI3K and in P-Akt/Akt ratio as well as in the expression of PKC, ERK1/2, survivin, and P-Bcl2 (Ser70) in both cell lines. CONCLUSIONS Nicotine, contained in cigarette smoking, could participate in colon cancer development and progression by stimulating cell proliferation and suppressing physiological apoptosis.

Antiproliferative and apoptotic effects triggered by grape seed extract (GSE) versus epigallocatechin and procyanidins on colon cancer cell lines

Grape seed extract has been proven to exert anticancer effects on different tumors. These effects are mainly ascribed to catechin and procyanidin content. Analytical studies demonstrated that grape seed extract composition is complex and it is likely other components could exert biological activities. Using cell count and flow cytometry assays, we evaluated the cytostatic and apoptotic effects produced by three different grape seed extracts from Italia, Palieri and Red Globe cultivars, on Caco2 and HCT-8 colon cancer cells. These effects were compared to those induced by epigallocatechin and procyanidins, alone or in association, on the same cell lines. All the extracts induced growth inhibition and apoptosis in Caco2 and HCT-8 cells, along the intrinsic apoptotic pathway. On both cell lines, growth inhibition induced by Italia and Palieri grape seed extracts was significantly higher than that it has been recorded with epigallocatechin, procyanidins and their association. In Caco2 cells, the extract from Red Globe cultivar was less effective in inducing growth inhibition than procyanidins alone and in association with epigallocatechin, whereas, in HCT-8 cells, only the association of epigallocatechin and procyanidins triggers a significant proliferation decrease. On both cell lines, apoptosis induced by Italia, Palieri and Red Globe grape seed extracts was considerably higher than has been recorded with epigallocatechin, procyanidins and their association. These data support the hypothesis by which other compounds, present in the grape seed extracts, are likely to enhance the anticancer effects.

Melatonin down-regulates MDM2 gene expression and enhances p53 acetylation in MCF-7 cells.

Compelling evidence demonstrated that melatonin increases p53 activity in cancer cells. p53 undergoes acetylation to be stabilized and activated for driving cells destined for apoptosis/growth inhibition. Over‐expression of p300 induces p53 acetylation, leading to cell growth arrest by increasing p21 expression. In turn, p53 activation is mainly regulated in the nucleus by MDM2. MDM2 also acts as E3 ubiquitin ligase, promoting the proteasome‐dependent p53 degradation. MDM2 entry into the nucleus is finely tuned by two different modulations: the ribosomal protein L11, acts by sequestering MDM2 in the cytosol, whereas the PI3K‐AkT‐dependent MDM2 phosphorylation is mandatory for MDM2 translocation across the nuclear membrane. In addition, MDM2‐dependent targeting of p53 is regulated in a nonlinear fashion by MDM2/MDMX interplay. Melatonin induces both cell growth inhibition and apoptosis in MCF7 breast cancer cells. We previously reported that this effect is associated with reduced MDM2 levels and increased p53 activity. Herein, we demonstrated that melatonin drastically down‐regulates MDM2 gene expression and inhibits MDM2 shuttling into the nucleus, given that melatonin increases L11 and inhibits Akt‐PI3K‐dependent MDM2 phosphorylation. Melatonin induces a 3‐fold increase in both MDMX and p300 levels, decreasing simultaneously Sirt1, a specific inhibitor of p300 activity. Consequently, melatonin‐treated cells display significantly higher values of both p53 and acetylated p53. Thus, a 15‐fold increase in p21 levels was observed in melatonin‐treated cancer cells. Our results provide evidence that melatonin enhances p53 acetylation by modulating the MDM2/MDMX/p300 pathway, disclosing new insights for understanding its anticancer effect.

Apoptosis-inducing factor and caspase-dependent apoptotic pathways triggered by different grape seed extracts on human colon cancer cell line Caco-2

Consumption of grape seed extract (GSE) is widely marketed as a dietary supplement and is considered safe for human health. Nevertheless, the analytical composition of GSE from different grape cultivars, growing in special agronomic constraints, differs greatly in flavan-3-ols content. The major concern with GSE studies is a lack of availability of uniformly standardised preparations, which raises an important question whether different GSE samples have comparable activity and trigger the same mechanisms of action on a given biological system. Therefore, it is tempting to speculate that GSE, obtained from different cultivars, could exert differentiated anticancer effects. The focus of the present study is to determine the selective biological efficacy of GSE obtained from three different sources on the human colon cancer cell line Caco-2. Irrespective of its source, high doses of GSE induced a significant inhibition on Caco-2 cell growth. Moreover, apoptosis was enhanced through both caspase-dependent and caspase-independent mechanisms, leading to an early apoptosis-inducing factor release and, further, to a dramatic increase in caspase 7 and 3 activity. However, a significant difference in apoptotic rates induced by the three grape sources clearly emerged when treating cancer cells with low and intermediate GSE concentrations (25 and 50 microg/ml).

The rationale of the myo‐inositol and D‐chiro‐inositol combined treatment for polycystic ovary syndrome

PCOS is one of the most common endocrine disorders affecting women and it is characterized by a combination of hyper‐androgenism, chronic anovulation, and insulin resistance. While a significant progress has recently been made in the diagnosis for PCOS, the optimal infertility treatment remains to be determined. Two inositol isomers, myo‐inositol (MI) and D‐chiro‐inositol (DCI) have been proven to be effective in PCOS treatment, by improving insulin resistance, serum androgen levels and many features of the metabolic syndrome. However, DCI alone, mostly when it is administered at high dosage, negatively affects oocyte quality, whereas the association MI/DCI, in a combination reproducing the plasma physiological ratio (40:1), represents a promising alternative in achieving better clinical results, by counteracting PCOS at both systemic and ovary level.

Nicotine increases survival in human colon cancer cells treated with chemotherapeutic drugs.

Cigarette smoking is implicated in the development of colon cancer. Furthermore, nicotine increases cell proliferation and inhibits apoptosis through α7-nicotinic acetylcholine receptor (α7-nAChR) activation in human colon carcinoma cells. An open issue is whether nicotine interfere with colorectal cancer pharmacological treatment, by inhibiting drug-mediated apoptosis. To assess this hypothesis, we evaluated nicotine effect on Caco-2 and HCT-8 colon cancer cells, treated with 5-Fluorouracil (5-FU) and Camptothecin (CPT), chemotherapeutics commonly utilized as adjuvant treatment of colon cancer. Nicotine decreased anti-proliferative and pro-apoptotic effects exerted by chemotherapeutics on both cell lines. These effects partially reverted by exposure to α-bungarotoxin (α-BTX), an inhibitor of α7-nAChR. Nicotine addition to Caco-2 and HCT-8, treated with 5-FU or CPT, decreased the cleavage of substrate of caspase 3 and 7, poly-ADP-ribose polymerase (PARP). Moreover, P-ERK/ERK ratio was modified by nicotine addition to 5-FU and CPT treated cells in an opposite manner. However, when co-administrating PD98059, an ERK phosphorylation inhibitor, an increased apoptosis was observed. In Caco-2 and HCT-8 nicotine reverted 5-FU and CPT apoptotic effects through AKT phosphorylation, as demonstrated by apoptotic increase in presence of LY294002, an AKT phosphorylation inhibitor. Nicotine interfered with colorectal cancer pharmacological treatment in vitro by inhibiting apoptosis induced by chemotherapeutic drugs. Nicotine anti-apoptotic effects were exerted through ERK and AKT pathway activation.

Grape seed extract triggers apoptosis in Caco-2 human colon cancer cells through reactive oxygen species and calcium increase: extracellular signal-regulated kinase involvement

Grape seed extract (GSE) from Italia, Palieri and Red Globe cultivars inhibits cell growth and induces apoptosis in Caco-2 human colon cancer cells in a dose-dependent manner. In order to investigate the mechanism(s) supporting the apoptotic process, we analysed reactive oxygen species (ROS) production, intracellular Ca2+ handling and extracellular signal-regulated kinase (ERK) activation. Upon exposure to GSE, ROS and intracellular Ca2+ levels increased in Caco-2 cells, concomitantly with ERK inactivation. As ERK activity is thought to be essential for promoting survival pathways, inhibition of this kinase is likely to play a relevant role in GSE-mediated anticancer effects. Indeed, pretreatment with N-acetyl cysteine, a ROS scavenger, reversed GSE-induced apoptosis, and promoted ERK phosphorylation. This effect was strengthened by ethylene glycol tetraacetic acid-mediated inhibition of extracellular Ca2+ influx. ROS and Ca2+ influx inhibition, in turn, increased ERK phosphorylation, and hence almost entirely suppressed GSE-mediated apoptosis. These data suggested that GSE triggers a previously unrecognised ERK-based mechanism, involving both ROS production and intracellular Ca2+ increase, eventually leading to apoptosis in cancer cells.

Quantitative shape analysis of chemoresistant colon cancer cells: correlation between morphotype and phenotype.

Morphological, qualitative observations allow pathologists to correlate the shape the cells acquire with the progressive, underlying neoplastic transformation they are experienced. Cell morphology, indeed, roughly scales with malignancy. A quantitative parameter for characterizing complex irregular structures is the Normalized Bending Energy (NBE). NBE provides a global feature for shape characterization correspondent to the amount of energy needed to transform the specific shape under analysis into its lowest energy state. We hypothesized that a chemotherapy resistant cancer cell line would experience a significant change in its shape, and that such a modification might be quantified by means of NBE parameterization. We checked out the usefulness of a mathematical algorithm to distinguish wild and 5-fluorouracil (5-FU)-resistant colon cancer HCT-8 cells (HCT-8FUres). NBE values, as well as cellular and molecular parameters, were recorded in both cell populations. Results demonstrated that acquisition of drug resistance is accompanied by statistically significant morphological changes in cell membrane, as well as in biological parameters. Namely, NBE increased progressively meanwhile cells become more resistant to increasing 5-FU concentrations. These data indicate how tight the relationships between morphology and phenotype is, and they support the idea to follow a cell transition toward a drug-resistant phenotype by means of morphological monitoring.