Resveratrol- induced apoptosis is mediated by p53-dependent pathway in Hep G2 cells

Resveratrol, a phytoalexin found in many plants, has been reported to possess a wide range of pharmacological properties and is one of the promising chemopreventive agents for cancer. Here, we examined the antiproliferation effect of resveratrol in two human liver cancer cell lines, Hep G2 and Hep 3B. Our results showed that resveratrol inhibited cell growth in p53-positive Hep G2 cells only. This anticancer effect was a result of cellular apoptotic death induced by resveratrol via the p53-dependent pathway. Here we demonstrated that the resveratrol-treated cells were arrested in G1 phase and were associated with the increase of p21 expression. In addition, we also illustrated that the resveratrol-treated cells had enhanced Bax expression but they were not involved in Fas/APO-1 apoptotic signal pathway. In contrast, the p53-negative Hep 3B cells treated with resveratrol did not show the antiproliferation effect neither did they show significant changes in p21 nor Fas/APO-1 levels. In summary, our study demonstrated that the resveratrol effectively inhibited cell growth and induced programmed cell death in Hepatoma cells on a molecular basis. Furthermore, these results implied that resveratrol might also be a new potent chemopreventive drug candidate for liver cancer as it played an important role to trigger p53-mediated molecules involved in the mechanism of p53-dependent apoptotic signal pathway.     

Identification and purification of resveratrol targeting proteins using immobilized resveratrol affinity chromatography

The phytochemical resveratrol (trans-3,4′,5-trihydroxystilbene) is a naturally occurring polyphenol with a plethora of health-beneficial properties, including a preventive role in cancer. We surmise that resveratrol may exert its diverse biological effects by interacting with specific target proteins, denoted RTPs. To test this possibility, resveratrol was immobilized on epoxy-activated agarose forming a resveratrol affinity column (RAC), which was used to detect and isolate RTPs. Distinct RTPs can be resolved on RAC by fractionation with increasing NaCl, followed by 1 mM ATP, and finally, with 1-2 mM resveratrol. A 22-kDa polypeptide, RTP-22, eluted with resveratrol was identified by MALDI-TOF MS and cloning/expression in Escherichia coli, as dihydronicotinamide riboside quinone reductase 2 (NQO2). The utility of RAC was additionally explored with extracts derived from different staging prostate cancer cells. NQO2 was most abundant in CWR22Rv1, a model for prostate cancer transition from androgen-dependent to the hormone-refractory state, but was marginally expressed in JCA-1 cells as representing more advanced stage prostate cancer. These results provide evidence for the existence of distinctive RTPs in mammalian cells and that RAC is a facile approach to identify and purify RTPs.     

Profound negative regulatory effects by resveratrol on vascular smooth muscle cells: a role of p53-p21(WAF1/CIP1) pathway

We investigated the role of resveratrol, a polyphenol rich in red wine, in cell cycle progression and apoptosis of vascular smooth muscle cells (VSMCs). Resveratrol inhibited the growth of human aortic VSMCs at concentrations as low as 1 microM. This was due to the profound dose-dependent inhibition of DNA synthesis by resveratrol. DNA synthesis was more effectively inhibited when cells were pretreated with resveratrol. Resveratrol caused a dose-dependent increase in intracellular p53 and p21(WAF1/CIP1) levels. At lower concentrations (6.25-12.5 microM), resveratrol effectively blocked cell cycle progression of serum-stimulated VSMCs without inducing apoptosis, while the higher concentration of resveratrol (25 microM) selectively induced apoptosis in the same VSMCs. Intriguingly, however, the same high concentration of resveratrol could not induce apoptosis in quiescent VSMCs. These differential biological effects of resveratrol on quiescent and proliferating VSMCs suggest that resveratrol may be capable of selectively eliminating abnormally proliferating VSMCs of the arterial walls in vivo.     

The NAD(P)H:Quinone Oxidoreductase 1 induces cell cycle progression and proliferation of melanoma cells

The oxidoreductase NQO1 plays a prominent role in maintaining the cellular homeostasis. NQO1 is mainly a cytosolic enzyme which catalyzes the metabolism of quinones and is present in almost all tissue types providing protection against different stresses including xenobiotics, oxidants, UV light, and ionizing radiation. This enzyme is overexpressed in many cancerous tissues and its function in carcinogenesis remains unclear. Due to the relative lack of information on the role of NQO1 in melanoma pathogenesis, we attempted to determine the expression and basic function of NQO1 in melanoma cell proliferation. We found that NQO1 is overexpressed in most melanoma cell lines with respect to melanocytes. Furthermore, the expression of this oxidoreductase significantly induces cell cycle progression by upregulating the expression of cyclins A2, B1 and D1, leading to the proliferation of melanoma cells. Our results also indicate that NQO1 is an upstream regulator of NF-κB p50, a factor linked to melanoma progression and poor patient prognosis. Interestingly, we found that NQO1 stabilizes the transactivator BCL3, which in turn upregulates NF-κB p50. More importantly, our results also indicate that NF-κB p50 correlates with the expression of NQO1 and mediates its role in the proliferation of melanoma cells.     

Thyroid hormone is a MAPK-dependent growth factor for thyroid cancer cells and is anti-apoptotic

Thyroid hormone (l-thyroxine, T(4), or 3,5,3'-triiodo-l-thyronine, T(3)) treatment of human papillary and follicular thyroid cancer cell lines resulted in enhanced cell proliferation, measured by proliferating cell nuclear antigen (PCNA). Thyroid hormone also induced activation of the Ras/MAPK (ERK1/2) signal transduction pathway. ERK1/2 activation and cell proliferation caused by thyroid hormone were blocked by an iodothyronine analogue, tetraiodothyroacetic acid (tetrac), that inhibits binding of iodothyronines to the cell surface receptor for thyroid hormone on integrin alphaVbeta3. A MAPK cascade inhibitor at MEK, PD 98059, also blocked hormone-induced cell proliferation. We then assessed the possibility that thyroid hormone is anti-apoptotic. We first established that resveratrol (10 microM), a pro-apoptotic agent in other cancer cells, induced p53-dependent apoptosis and c-fos, c-jun and p21 gene expression in both papillary and follicular thyroid cancer cells. Induction of apoptosis by the stilbene required Ser-15 phosphorylation of p53. Resveratrol-induced gene expression and apoptosis were inhibited more than 50% by physiological concentrations of T(4). T(4) activated MAPK in the absence of resveratrol, caused minimal Ser-15 phosphorylation of p53 and did not affect c-fos, c-jun and p21 mRNA abundance. Thus, plasma membrane-initiated activation of the MAPK cascade by thyroid hormone promotes papillary and follicular thyroid cancer cell proliferation in vitro.     

白藜芦醇对人子宫内膜癌细胞系AN3CA增殖和凋亡效应及其机制探讨

目的：探讨白藜芦醇（resveratrol,Res）对人子宫内膜癌细胞AN3CA的增殖抑制和凋亡诱导效应及可能存在的机制。方法：应用噻唑蓝（MTT）法检测Res对AN3CA的增殖影响;流式细胞术检测Res对细胞周期分布和凋亡影响：荧光实时定量PCR检测Res对细胞Bcl-2、Bax和MMP-9mRNA表达水平的影响;WesternBlot方法检测Res对PCNA、Bcl-2、Bax及ERK1／2、P—ERK1／2蛋白表达水平的影响。结果：Res对子宫内膜癌细胞AN3CA具有显著的生长抑制作用（P〈0．01）,呈时间-剂量依赖性;不同浓度Res处理细胞G0／G1期比例显著增加伴随S期细胞数的减少;细胞凋亡率明显增高,200Dmol／lRes处理48h凋亡率可达30．96％±2．041％（P〈0．01）。与对照组相比,Res能抑制PCNA的蛋白表达量,增加Bax和降低Bcl-2转录和蛋白水平的表达量。Res在短时间内（0．5—1h）激活ERK1／2的磷酸化表达但随着作用时间延长（4—48h）其表现为抑制效应。结论：Res具有抑制AN3CA细胞增殖,诱导细胞G0／G1期阻滞和凋亡的效应。Res诱导凋亡可能是通过上调Bax,下调Bcl-2发挥作用,其抗癌作用机制可能与ERK1／2通路失调相关。     

Nutlin-3a, an MDM2 antagonist and p53 activator, helps to preserve the replicative potential of cancer cells treated with a genotoxic dose of resveratrol

Resveratrol is a natural compound that has been intensely studied due to its role in cancer prevention and potential as an anti-cancer therapy. Its effects include induction of apoptosis and senescence-like growth inhibition. Here, we report that two cancer cell lines (U-2 OS and A549) differ significantly in their molecular responses to resveratrol. Specifically, in U-2 OS cells, the activation of the p53 pathway is attenuated when compared to the activation in A549 cells. This attenuation is accompanied by a point mutation (458: CGA→TGA) in the PPM1D gene and overexpression of the encoded protein, which is a negative regulator of p53. Experimentally induced knockdown of PPM1D in U-2 OS cells resulted in slightly increased activation of the p53 pathway, most clearly visible as stronger phosphorylation of p53 Ser³⁷. When treated with nutlin-3a, a non-genotoxic activator of p53, U-2 OS and A549 cells both responded with substantial activation of the p53 pathway. Nutlin-3a improved the clonogenic survival of both cell lines treated with resveratrol. This improvement was associated with lower activation of DNA-damage signaling (phosphorylation of ATM, CHK2, and histone H2AX) and higher accumulation of cells in the G1 phase of the cell cycle. Thus, the hyperactivation of p53 by nutlin-3a helps to preserve the replicative potential of cells exposed to resveratrol.     

Resveratrol prevents endothelial cells injury in high-dose interleukin-2 therapy against melanoma

Immunotherapy with high-dose interleukin-2 (HDIL-2) is an effective treatment for patients with metastatic melanoma and renal cell carcinoma. However, it is accompanied by severe toxicity involving endothelial cell injury and induction of vascular leak syndrome (VLS). In this study, we found that resveratrol, a plant polyphenol with anti-inflammatory and anti-cancer properties, was able to prevent the endothelial cell injury and inhibit the development of VLS while improving the efficacy of HDIL-2 therapy in the killing of metastasized melanoma. Specifically, C57BL/6 mice were injected with B16F10 cells followed by resveratrol by gavage the next day and continued treatment with resveratrol once a day. On day 9, mice received HDIL-2. On day 12, mice were evaluated for VLS and tumor metastasis. We found that resveratrol significantly inhibited the development of VLS in lung and liver by protecting endothelial cell integrity and preventing endothelial cells from undergoing apoptosis. The metastasis and growth of the tumor in lung were significantly inhibited by HDIL-2 and HDIL-2 + resveratrol treatment. Notably, HDIL-2 + resveratrol co-treatment was more effective in inhibiting tumor metastasis and growth than HDIL-2 treatment alone. We also analyzed the immune status of Gr-1(+)CD11b(+) myeloid-derived suppressor cells (MDSC) and FoxP3(+)CD4(+) regulatory T cells (Treg). We found that resveratrol induced expansion and suppressive function of MDSC which inhibited the development of VLS after adoptive transfer. However, resveratrol suppressed the HDIL-2-induced expansion of Treg cells. We also found that resveratrol enhanced the susceptibility of melanoma to the cytotoxicity of IL-2-activated killer cells, and induced the expression of the tumor suppressor gene FoxO1. Our results suggested the potential use of resveratrol in HDIL-2 treatment against melanoma. We also demonstrated, for the first time, that MDSC is the dominant suppressor cell than regulatory T cell in the development of VLS.     

Skp2 regulates G2/M progression in a p53-dependent manner

Targeted proteasomal degradation mediated by E3 ubiquitin ligases controls cell cycle progression, and alterations in their activities likely contribute to malignant cell proliferation. S phase kinase-associated protein 2 (Skp2) is the F-box component of an E3 ubiquitin ligase complex that targets p27^Kip1 and cyclin E1 to the proteasome. In human melanoma, Skp2 is highly expressed, regulated by mutant B-RAF, and required for cell growth. We show that Skp2 depletion in melanoma cells resulted in a tetraploid cell cycle arrest. Surprisingly, co-knockdown of p27^Kip1 or cyclin E1 failed to prevent the tetraploid arrest induced by Skp2 knockdown. Enhanced Aurora A phosphorylation and repression of G2/M regulators cyclin B1, cyclin-dependent kinase 1, and cyclin A indicated a G2/early M phase arrest in Skp2-depleted cells. Furthermore, expression of nuclear localized cyclin B1 prevented tetraploid accumulation after Skp2 knockdown. The p53 status is most frequently wild type in melanoma, and the tetraploid arrest and down-regulation of G2/M regulatory genes were strongly dependent on wild-type p53 expression. In mutant p53 melanoma lines, Skp2 depletion did not induce cell cycle arrest despite up-regulation of p27^Kip1. These data indicate that elevated Skp2 expression may overcome p53-dependent cell cycle checkpoints in melanoma cells and highlight Skp2 actions that are independent of p27^Kip1 degradation.     

Modulation of antioxidant enzymes p21WAF1 and p53 expression during proliferation and differentiation of human melanoma cell lines

The activities of antioxidant enzymes, and the expression of p21(WAF1) and p53 proteins were studied at different times after subculture during proliferation and differentiation phases. Two human melanoma cell lines were used: IPC182, which is a non-differentiating cell line, and IGR221, which spontaneously differentiates at the end of the exponential growth phase, as evidenced by a marked increase of melanin content and tyrosinase activity. In the two cell lines, the slowing of proliferation coincided with an increase in the activity and amount of immunoreactive superoxide dismutases (SOD1 and SOD2), and a decrease of catalase and glutathione peroxidase activities, and of the glutathione content. The levels of p21WAF1 and p53 proteins were found to be lower in confluent than in proliferative cells. Several parameters were modified only during the differentiation phase of IGR221 cells; in these cells the increase of tyrosinase activity was highly correlated with the increase in SOD2, GST, glutathione reductase, and G6PD activities. The level of glutathione was found to be lower in differentiated IGR221 than in non-differentiated IPC182 cells. These results suggest that p21WAF1 and p53 proteins are not involved in the spontaneous differentiation process of melanoma cells, and that abnormal regulation of the cell cycle inhibition pathway occurred in these cells. The results sustain the hypothesis that alterations of antioxidant enzyme expression are involved in the control of proliferation and differentiation of melanoma cells. Alterations of SOD2 activity may be of particular importance, since variations are observed with both cell growth and cell differentiation.     

Resveratrol induces cell‐cycle disruption and apoptosis in chemoresistant B16 melanoma

Resveratrol, a naturally occurring polyphenol, has been shown to possess chemopreventive activities. In this study, we show that resveratrol (0–500 µM) inhibits the growth of a doxorubicin‐resistant B16 melanoma cell subline (B16/DOX) (IC₅₀ = 25 µM after 72 h, P < 0.05). This was accomplished by imposing an artificial checkpoint at the G₁–S phase transition, as demonstrated by cell‐cycle analysis and down‐regulation of cyclin D1/cdk4 and increased of p53 expression level. The G₁‐phase arrest of cell cycle in resveratrol‐treated (10–100 µM) B16/DOX cells was followed by the induction of apoptosis, which was revealed by pyknotic nuclei and fragmented DNA. Resveratrol also potentiated at subtoxic dose (25 µM for 24 h) doxorubicin cytotoxicity in the chemoresistant B16 melanoma (P < 0.01). When administered to mice, resveratrol (12.5 mg/kg) reduced the growth of an established B16/DOX melanoma and prolonged survival (32% compared to untreated mice). All these data support a potential use of resveratrol alone or in combination with other chemotherapeutic agents in the management of chemoresistant tumors. J. Cell. Biochem. 110: 893–902, 2010. © 2010 Wiley‐Liss, Inc.     

High expression of Wee1 is associated with poor disease-free survival in malignant melanoma: potential for targeted therapy

Notoriously resistant malignant melanoma is one of the most increasing forms of cancer worldwide; there is thus a precarious need for new treatment options. The Wee1 kinase is a major regulator of the G(2)/M checkpoint, and halts the cell cycle by adding a negative phosphorylation on CDK1 (Tyr15). Additionally, Wee1 has a function in safeguarding the genome integrity during DNA synthesis. To assess the role of Wee1 in development and progression of malignant melanoma we examined its expression in a panel of paraffin-embedded patient derived tissue of benign nevi and primary- and metastatic melanomas, as well as in agarose-embedded cultured melanocytes. We found that Wee1 expression increased in the direction of malignancy, and showed a strong, positive correlation with known biomarkers involved in cell cycle regulation: Cyclin A (p<0.0001), Ki67 (p<0.0001), Cyclin D3 (p = 0.001), p21(Cip1/WAF1) (p = 0.003), p53 (p = 0.025). Furthermore, high Wee1 expression was associated with thicker primary tumors (p = 0.001), ulceration (p = 0.005) and poor disease-free survival (p = 0.008). Transfections using siWee1 in metastatic melanoma cell lines; WM239(WTp53), WM45.1(MUTp53) and LOX(WTp53), further support our hypothesis of a tumor promoting role of Wee1 in melanomas. Whereas no effect was observed in LOX cells, transfection with siWee1 led to accumulation of cells in G(1)/S and S phase of the cell cycle in WM239 and WM45.1 cells, respectively. Both latter cell lines displayed DNA damage and induction of apoptosis, in the absence of Wee1, indicating that the effect of silencing Wee1 may not be solely dependent of the p53 status of the cells. Together these results reveal the importance of Wee1 as a prognostic biomarker in melanomas, and indicate a potential role for targeted therapy, alone or in combination with other agents.     

Methoxylation of resveratrol: effects on induction of NAD(P)H quinone-oxidoreductase 1 (NQO1) activity and growth inhibitory properties

A series of methoxystilbenes (E and Z isomers) related to resveratrol were investigated for their effects on NQO1 induction in murine hepatoma cells and growth inhibitory effects on human cancer cell lines. Both activities were enhanced in compounds with methoxy groups on rings A and B of resveratrol but methoxylation of the di-meta (3,5) hydroxyl groups on ring A of resveratrol was found to be more critical for improving activity. Strikingly different structure-activity trends were observed, namely the association of E isomers with potent NQO1 induction activity and Z isomers with growth inhibitory properties. The introduction of ortho-methoxy groups on ring A greatly benefited NQO1 induction activity while meta/para methoxy groups on ring A were preferred for potent growth inhibitory effects. These results serve to highlight the contrasting effects on different activities brought about by methoxylation, which is widely employed as a structural modification approach to improve potency and bioavailability of resveratrol. It serves as a timely reminder that in the course of structural modification, a balance between optimizing desired outcomes against unwanted effects is necessary and the most potent analog need not always be the most desirable.     

MiR-21 Enhances Melanoma Invasiveness via Inhibition of Tissue Inhibitor of Metalloproteinases 3 Expression: In Vivo Effects of MiR-21 Inhibitor

Metastatic melanoma is the most aggressive form of this cancer. It is important to understand factors that increase or decrease metastatic activity in order to more effectively research and implement treatments for melanoma. Increased cell invasion through the extracellular matrix is required for metastasis and is enhanced by matrix metalloproteinases (MMPs). Tissue inhibitor of metalloproteinases 3 (TIMP3) inhibits MMP activity. It was previously shown by our group that miR-21, a potential regulator of TIMP3, is over-expressed in cutaneous melanoma. It was therefore hypothesized that increased levels of miR-21 expression would lead to decreased expression of TIMP3 and thereby enhance the invasiveness of melanoma cells. miR-21 over-expression in the melanoma cell lines WM1552c, WM793b, A375 and MEL 39 was accomplished via transfection with pre-miR-21. Immunoblot analysis of miR-21-overexpressing cell lines revealed reduced expression of TIMP3 as compared to controls. This in turn led to a significant increase in the invasiveness of the radial growth phase cell line WM1552c and the vertical growth phase cell line WM793b (p < 0.05), but not in the metastatic cell lines A375 or MEL 39. The proliferation and migration of miR-21 over-expressing cell lines was not affected. Reduced expression of TIMP3 was achieved by siRNA knockdown and significantly enhanced invasion of melanoma cell lines, mimicking the effects of miR-21 over-expression. Treatment of tumor cells with a linked nucleic acid antagomir to miR-21 inhibited tumor growth and increased tumor expression of TIMP3 in vivo in 01B74 Athymic NCr-nu/nu mice. Intra-tumoral injections of anti-miR-21 produced similar effects. This data shows that increased expression of miR-21 enhanced the invasive potential of melanoma cell lines through TIMP3 inhibition. Therefore, inhibition of miR-21 in melanoma may reduce melanoma invasiveness.     

Calpain-3 Impairs Cell Proliferation and Stimulates Oxidative Stress-Mediated Cell Death in Melanoma Cells

Calpain-3 is an intracellular cysteine protease, belonging to Calpain superfamily and predominantly expressed in skeletal muscle. In human melanoma cell lines and biopsies, we previously identified two novel splicing variants (hMp78 and hMp84) of Calpain-3 gene (CAPN3), which have a significant lower expression in vertical growth phase melanomas and, even lower, in metastases, compared to benign nevi. In the present study, in order to investigate the pathophysiological role played by the longer Calpain-3 variant, hMp84, in melanoma cells, we over-expressed it in A375 and HT-144 cells. In A375 cells, the enforced expression of hMp84 induces p53 stabilization, and modulates the expression of a few p53- and oxidative stress-related genes. Consistently, hMp84 increases the intracellular production of ROS (Reactive Oxygen Species), which lead to oxidative modification of phospholipids (formation of F₂-isoprostanes) and DNA damage. Such events culminate in an adverse cell fate, as indicated by the decrease of cell proliferation and by cell death. To a different extent, either the antioxidant N-acetyl-cysteine or the p53 inhibitor, Pifithrin-α, recover cell viability and decrease ROS formation. Similarly to A375 cells, hMp84 over-expression causes inhibition of cell proliferation, cell death, and increase of both ROS levels and F₂-isoprostanes also in HT-144 cells. However, in these cells no p53 accumulation occurs. In both cell lines, no significant change of cell proliferation and cell damage is observed in cells over-expressing the mutant hMp84^C42S devoid of its enzymatic activity, suggesting that the catalytic activity of hMp84 is required for its detrimental effects. Since a more aggressive phenotype is expected to benefit from down-regulation of mechanisms impairing cell growth and survival, we envisage that Calpain-3 down-regulation can be regarded as a novel mechanism contributing to melanoma progression.     

p53 gene expression and activation of p53-dependent transcription in melanoma cell lines

Malignant melanoma has poor prognosis because of its high metastatic potential and resistance to chemotherapy. A possible approach to more effective therapy is induction of p53-dependent apoptosis. This approach is promising, since the wild-type p53 is expressed in most melanomas. An attempt was made to estimate the functional activity of p53 in several malignant melanoma cell lines. Most lines were characterized by a high protein level and nuclear localization of p53. All cell lines expressing the wild-type p53 showed stabilization of p53, its translocation into the nucleus, and activation of several target genes in response to DNA-damaging agents, suggesting that p53 was functionally active. A high-molecular-weight protein localized in the cytoplasm and mimicking a p53 epitope was found in several cell lines. It was shown that the DO-1 epitope of this protein does not derive from p53, ruling out cytoplasmic retention of p53 in melanoma cell lines. A mechanism of camptothecin-induced stabilization of p53 by decreasing the level of the HDM2 mRNA was described for melanoma cells but not for normal melanocytes, which suggested a differential effect of camptothecin on tumor-derived and primary cells.