Resveratrol Promotes Proliferation, Antioxidant Properties, and Progesterone Production in Yak (Bos grunniens) Granulosa Cells

Resveratrol (RES) is a class of natural polyphenolic compounds known for its strong anti-apoptotic and antioxidant properties. Granulosa cells (GCs) are one of the important components of ovarian follicles and play crucial roles in follicular development of follicles in the ovary. Here, we explored the effects of RES on the proliferation and functions of yak GCs. Firstly, we evaluated the effect of RES dose and time in culture on the viability of GCs, and then the optimum treatment protocol (10 μM RES, 36 h) was selected to analyze the effects of RES on the proliferation, cell cycle, apoptosis, malondialdehyde (MDA), glutathione (GSH), reactive oxygen species (ROS) accumulation, lipid droplet content, ATP production, and steroidogenesis of GCs, as well as the expression of related genes. The results show that RES treatment significantly (1) increased cell viability and proliferation and inhibited cell apoptosis by upregulating BCL-2 and SIRT1 genes and downregulating BAX, CASP3, P53, and KU70 genes; (2) increased the proportion of GCs in the S phase and upregulated CCND1, PCNA, CDK4, and CDK5 genes; (3) reduced ROS accumulation and MDA content and increased GSH content, as well as upregulating the relative expression levels of CAT, SOD2, and GPX1 genes; (4) decreased lipid droplet content and increased ATP production; (5) promoted progesterone (P4) secretion and the expression of P4 synthesis-related genes (StAR, HSD3B1, and CYP11A1); and (6) inhibited E2 secretion and CYP19A1 expression. These findings suggest that RES at 10 μM increases the proliferation and antioxidant properties, inhibits apoptosis, and promotes ATP production, lipid droplet consumption, and P4 secretion of yak GCs.

TMT-based quantitative proteomics analysis reveals the differential proteins between fresh and frozen-thawed sperm of yak (Bos grunniens)

Sperm cryopreservation is one of the most effective methods for the conservation of germplasm resources and used of superior sires widely. However, the motility of yak (Bos grunniens) sperm was low after thawing and the proteomics changes in sperm cryopreservation remain unknown. Therefore, the aim of this study was to explore the differences between fresh sperm and frozen sperm of yak through the proteomic analysis and thus improve the understanding of sperm cryodamage. The Tandem Mass Tags (TMT) technology was used to screen differentially expressed proteins (DEPs) before and after freezing. Then, GO and KEGG analysis were conducted to analyze the DEPs enriched signaling pathways. Finally, the DEPs, including superoxide dismutase 1 (SOD1) and NADH ubiquinone oxidoreductase core subunit S8 (NDUFS8) were verified by the immunofluorescence technique. The results showed that there were 229 DEPs between fresh and frozen-thawed yak sperm. Compared with the fresh sperm, 120 proteins were up-regulated and 109 proteins were down-regulated in frozen-thawed sperm. The GO annotation showed that the up-regulated proteins enriched in metabolic and cytoskeleton-related processes, including lipoprotein metabolic process, lipid transport, extracellular region and intermediate filament cytoskeleton organization. In contrast, the down-regulated proteins enriched in biological processes including single fertilization, sperm capacitation and response to unfolded protein. KEGG pathway analysis indicated that freezing and thawing affected the oxidative phosphorylation pathway, the fructose and mannose metabolic pathway and the glycerolipid metabolic pathway of yak sperm. Immunofluorescence results showed that the protein expression level of SOD1 protein in the frozen group was significantly lower than that in the fresh group (P < 0.01), and the protein expression level of NDUFS8 protein was significantly higher in frozen group (P < 0.01). This study revealed the DEPs between fresh and frozen-thawed sperm and provides a theoretical basis to further explore the exertion of normal biological functions of yak sperm after freezing and thawing.

Histopathological features of antrochoanal polyps in Chinese patients

BACKGROUND

The pathogenesis and etiology of antrochoanal polyps (ACP) are unclear. The aim of this study is to characterize the features of inflammatory cellular infiltration, the epithelial remodeling patterns and their associations to clinical parameters in ACP.

METHODS

A detailed histological study employing classic immunohistochemistry was performed. 33 ACPs, 49 classic bilateral nasal polyps (BNP) and 50 controls were obtained. The histological patterns and inflammatory cells infiltration were evaluated and analyzed for associations with clinical characteristics.

RESULTS

Less severe epithelial hyperplasia and goblet cell hyperplasia were found in ACP compared to BNP. In ACP, 87.9% of cases demonstrated neutrophilia. Elevated proportions of macrophages and CD8+ T cells, and elevated infiltration of mast cells was observed. Eosinophil infiltration was found to be positively corelated with a history of asthma; macrophages proportion was analyzed to have a significantly negative correlation with epithelial hyperplasia and goblet cell hyperplasia; the infiltration of CD8+ T cell and squamous metaplasia were found to have a positive correlation.

CONCLUSION

Inflammation potentially has important roles in ACP. ACP may differ in its pathogenesis from classic bilateral nasal polyps.

Effects of Zinc Supplementation During In Vitro Maturation on Meiotic Maturation of Oocytes and Developmental Capacity in Yak

Zinc (Zn) is an essential trace element that is required during mammalian developmental processes. The objective of this study was to investigate the effects of Zn supplementation during in vitro maturation (IVM) on the developmental capacity of yak (Bos grunniens) oocytes. Cumulus expansion, nuclear maturation, intracellular glutathione (GSH), reactive oxygen species (ROS) levels, superoxide dismutase (SOD) activity, subsequent embryonic development, and the expression of Zn transporters (ZnTs) and Zrt and Irt-like proteins (ZiPs) were evaluated. The Zn concentrations in yak plasma and follicular fluid were 0.740 ± 0.012 and 0.382 ± 0.009 μg/mL, respectively. The cumulus expansion did not show significant differences in COCs after matured with or without Zn supplementation (P > 0.05). The intracellular GSH was higher in oocytes matured with 1 or 2 mg/L Zn than in control group (0 mg/L) (P < 0.05). However, ROS levels of oocytes matured with 1 or 2 mg/L Zn were reduced significantly compared with the control and 0.5 mg/L groups (P < 0.05). The SOD activity was increased significantly after Zn supplementation. The cleavage rate was not significantly different after Zn supplementation (P > 0.05). Percentages of matured oocytes that developed into the blastocyst stage after IVF were 47.9, 50.5, 60.4, and 58.9% for 0, 0.5, 1, and 2 mg/L Zn groups, respectively. Gene expression analysis revealed that the expression patterns associated with Zn were changed after Zn supplementation. In conclusion, Zn supplementation to IVM improved yak oocyte maturation and subsequent development by increasing GSH and SOD activity, decreasing ROS in oocytes.

Bladder Cancer Chemopreventive Agents: Current Knowledge and Concepts

Bladder cancer is the most prevalent malignancy of the urinary tract and is associated with significant morbidity and mortality. Preventative efforts to reduce the medical and financial burdens of bladder cancer are highly desirable. However, the utilization of natural and pharmaceutical products for the prevention and treatment of bladder cancer remains largely controversial. Herein, we review the current body of evidence surrounding a number of natural dietary substances and their roles in chemoprevention of bladder cancer. Possible chemopreventative properties of several pharmaceutical agents are also reviewed. Overall, the current body of evidence is insufficient to establish a clear link between these proposed chemopreventive agents and risk of bladder cancer.

Yak response to high-altitude hypoxic stress by altering mRNA expression and DNA methylation of hypoxia-inducible factors

Hypoxia-inducible factors (HIFs) are oxygen-dependent transcriptional activators, which play crucial roles in tumor angiogenesis and mammalian development, and regulate the transcription of genes involved in oxygen homeostasis in response to hypoxia. However, information on HIF-1α and HIF-2α in yak (Bos grunniens) is scarce. The complete coding region of yak HIF-2α was cloned, its mRNA expression in several tissues were determined, and the expression levels were compared with those of closely related low-altitude cattle (Bos taurus), and the methylation status of promoter regions were analyzed to better understand the roles of HIF-1α and HIF-2α in domesticated yak. The yak HIF-2α cDNA was cloned and sequenced in the present work reveals the evolutionary conservation through multiple sequence alignment, although 15 bases changed, resulting in 8 amino acid substitutions in the translated proteins in cattle. The tissue-specific expression results showed that HIF-1α is ubiquitously expressed, whereas HIF-2α expression is limited to endothelial tissues (kidney, heart, lung, spleen, and liver) and blood in yak. Both HIF-1α and HIF-2α expressions were higher in yak tissues than in cattle. The HIF-1α expression level is much higher in yak than cattle in these organs, except for the lung (P < 0.05), but the HIF-2α gene is significantly different in the heart, spleen, and kidney (P < 0.05). Furthermore, the methylation levels in the 5' flanking regulatory regions of HIF-1α and HIF-2α in yak kidney were significantly decreased than cattle counterparts (P < 0.05). Identifying these genes and the comparison of different expressions facilitates the understanding of the biological high-altitude hypoxic stress response mechanism and may assist current medical research to understand hypoxia-related diseases.

Zebularine and scriptaid significantly improve epigenetic reprogramming of yak fibroblasts and cloning efficiency

Abnormal epigenetic reprogramming of the donor nucleus after somatic cell nuclear transfer (SCNT) is thought to be the main cause of low cloning efficiency. Following SCNT, the donor nucleus often fails to express early embryonic genes and establish a normal embryonic pattern of chromatin modification. Therefore, in this study, we have attempted to improve epigenetic reprogramming of the donor nucleus and cloned embryos with Zebularine and Scriptaid. Yak fibroblasts were treated with 20 μM Zebularine alone or 20 μM Zebularine plus 0.5 μM Scriptaid for 24 h, whereas yak cloned embryos were treated exclusively with 0.5 μM Scriptaid for 12 h. There was no effect on cellular viability and proliferation after drug treatment. The treatment of fibroblasts with Zebularine or Zebularine plus Scriptaid increased histone acetylation of histone 3 lysine 9 (H3K9), but decreased the level of DNA methylation of Oct-4 and Sox-2 promoter regions. When donor cells were used after Zebularine plus Scriptaid treatment to reconstruct cloned embryos and then treated with Scriptaid, the developmental competence and cryosurvival of embryos were improved significantly. In addition, the relative expression of Oct-4 and Sox-2 were increased significantly. The expression levels of Dnmt-1 and Hdac-1 were significantly decreased when fibroblasts and cloned embryos were treated with Zebularine or Scriptaid. This work provides functional evidence that treatment with Zebularine and Scriptaid modifies the epigenetic status of yak fibroblasts, subsequently enhancing in vitro developmental potential and the quality of yak cloned embryos.

Insulin-like growth factor-binding protein-3 inhibition of prostate cancer growth involves suppression of angiogenesis

Insulin-like growth factor-binding protein-3 (IGFBP-3) is a multifunctional protein that induces apoptosis utilizing both insulin-like growth factor receptor (IGF)-dependent and -independent mechanisms. We investigated the effects of IGFBP-3 on tumor growth and angiogenesis utilizing a human CaP xenograft model in severe-combined immunodeficiency mice. A 16-day course of IGFBP-3 injections reduced tumor size and increased apoptosis and also led to a reduction in the number of vessels stained with CD31. In vitro, IGFBP-3 inhibited both vascular endothelial growth factor- and IGF-stimulated human umbilical vein endothelial cells vascular network formation in a matrigel assay. This action is primarily IGF independent as shown by studies utilizing the non-IGFBP-binding IGF-1 analog Long-R3. Additionally, we used a fibroblast growth factor-enriched matrigel-plug assay and chick allantoic membrane assays to show that IGFBP-3 has potent antiangiogenic actions in vivo. Finally, overexpression of IGFBP-3 or the non-IGF-binding GGG-IGFBP-3 mutant in Zebrafish embryos confirmed that both IGFBP-3 and the non-IGF-binding mutant inhibited vessel formation in vivo, indicating that the antiangiogenic effect of IGFBP-3 is an IGF-independent phenomenon. Together, these studies provide the first evidence that IGFBP-3 has direct, IGF-independent inhibitory effects on angiogenesis providing an additional mechanism by which it exerts its tumor suppressive effects and further supporting its development for clinical use in the therapy of patients with prostate cancer.

[Investigation on acute stroke patients being admitted to hospital]

One hundred and twelve patients with acute stroke were studied. The results revealed that about 42 percent of 112 patients could get to hospital within 6 hours after onset, in which included 60.4 percent of the hemorrhagic group and 28.1 percent of the infarction group. Comparatively, among 30.3 percent of 112 patients CT scan was carried out within 6 hours, which included 41.7 percent of the hemorrhagic group and 21.8 percent of the infarction group. Linear correlation analysis was studied between admission time(AT) and the assessment of neural function defect(ANFD). The results showed that there was significant negative correlation between AT and ANFD in stroke patients. After analysing the serial reasons of delaying hospitalization, the authors have found that the key factor is the ignorance of the importance of stroke in early stage.

[Apoptosis of CD4(+) T cells during experimental autoimmune neuritis in Wistar rats]

The present study describes apoptosis of T cells in the sciatic nerve in Wistar rats with experimental autoimmune neuritis(EAN). Morphological characterizations of apoptosis were found at the 18th day from onset, peaked at the 22nd day by immunocytochemical analysis. In situ end labeling(ISEL) techniques confirmed the presence of DNA fragmentation in CD4(+) T cells. It is suggested that apoptosis is an important clearance mechanism of infiltrated T cells in the peripheral nervous system(PNS) in EAN.

Insulin-like growth factor-I receptor signaling and resistance to trastuzumab (Herceptin)

BACKGROUND

Trastuzumab (Herceptin), an anti-HER2/neu receptor monoclonal antibody that inhibits growth of ErbB2-overexpressing breast cancer, is used to treat such cancers. Development of resistance to trastuzumab, however, is common. We investigated whether insulin-like growth factor-I (IGF-I), which activates cell survival signals, interferes with the growth-inhibitory action of trastuzumab.

METHODS

MCF-7/HER2-18 and SKBR3 human breast cancer models were used to assess cell proliferation, colony formation in soft agar, and cell cycle parameters. Throughout, we used trastuzumab at a dose of 10 microg/mL and IGF-I at a dose of 40 ng/mL. All statistical tests were two-sided.

RESULTS

Trastuzumab inhibited the growth of MCF-7/HER2-18 cells, which overexpress HER2/neu receptors and express IGF-I receptors (IGF-IRs), only when IGF-IR signaling was minimized. For example, in 1% fetal bovine serum (FBS), trastuzumab reduced cell proliferation by 42% (P =.002); however, in 10% FBS or IGF-I, trastuzumab had no effect on proliferation. In SKBR3 cells, which overexpress HER2/neu receptor but express few IGF-IRs, trastuzumab reduced proliferation by 42% (P =.008) regardless of IGF-I concentration. When SKBR3 cells were genetically altered to overexpress IGF-IRs and cultured with IGF-I, trastuzumab had no effect on proliferation. However, the addition of IGF-binding protein-3, which decreased IGF-IR signaling, restored trastuzumab-induced growth inhibition.

CONCLUSIONS

In breast cancer cell models that overexpress HER2/neu, an increased level of IGF-IR signaling appears to interfere with the action of trastuzumab. Thus, strategies that target IGF-IR signaling may prevent or delay development of resistance to trastuzumab.

[The relationship between cyanotoxin (microcystin, MC) in pond-ditch water and primary liver cancer in China]

OBJECTIVE

To explore the relationship between primary liver cancer (PLC) and MC in drinking pond-ditch water.

METHODS

Epidemiological and ecological assays, Meta-analysis and risk assessment were used in this study. Cyanotoxin (Microcystin, MC) in the water of different sources was detected by ELISA. The F344 and HBVx transgenic mice were used to confirm the promotion effect on PLC and the synthetically carcinogenic effect of HBV, aflatoxin and MC.

RESULTS

Using Meta-analysis the results of six case-control studies showed that the pooled odds ratio (OR) was 2.46 (95% CI 1.69-2.59), population attributable rick (PAR) was 30.39% (95% CI, 23.30%-37.47%), heterogeneity test P > 0.05. Eutrophication led to cyanobacterial bloom in the pond-ditch water. Cyanotoxin released from dead cyanobacteria was hepatotactic tumor promoter. In HBVx transgenic rats, hepatocellular carcinoma was induced by the joint administration of aflatoxin B1 and cyanotoxin. Epidemiological study showed that the recombined index of HBsAg, aflatoxin-albumin adducts and drinking of pond-ditch water correlated with PLC mortalities in 13 townships.

CONCLUSION

Microcystin in the pond-ditch water is a hepatotactic toxin which can induce hepatitis and promote development of hepatocellular carcinoma. The combined effect of microcystin, HBV and aflatoxin may be responsible for the endemicity of PLC.

Impairment of erbB1 receptor and fluid-phase endocytosis and associated mitogenic signaling by inositol hexaphosphate in human prostate carcinoma DU145 cells

Recently, we observed that epidermal growth factor receptor (EGFR or erbB1) endocytosis and associated mitogenic signaling occur in human prostate cancer (PCA) cells, suggesting that erbB1 endocytosis might be involved in advanced and androgen-independent PCA growth. Based on these findings, and the fact that aberrant expression of erbB family members is common in human prostatic intraepithelial neoplasia and invasive PCA, we reasoned that impairment of erbB1 endocytosis and associated mitogenic signaling might inhibit PCA growth. Inositol hexaphosphate (IP6) interacts with plasma membrane clathrin-associated protein complex 2 (AP2) and inhibits phosphatidylinositol 3-kinase (PI3K). As these are essential components of receptor-mediated and fluid-phase endocytosis, respectively, we reasoned that IP6 might impair erbB1 endocytosis and associated signaling in human PCA cells, leading to their growth inhibition. IP6 strongly to completely inhibited (26-100%; P < 0.05) transforming growth factor alpha-induced binding of activated erbB1 to AP2 in human PCA DU145 cells, demonstrating the impairment of the initial step in ligand-induced erbB1 endocytosis. IP6 treatment of cells resulted in a dose-dependent increase (1.8- to 7. 7-fold compared with cells treated with ligand alone; P < 0.05) in levels of activated erbB1. These two findings suggest that the inhibitory effect of IP6 on receptor endocytosis is independent of its lack of effect on ligand-induced erbB1 activation. These effects of IP6, however, were associated with strong inhibition of ligand-induced Shc phosphorylation (77-84% decrease; P < 0.05) and its binding to erbB1 (58-100% decrease; P < 0.05). IP6 also significantly and dose-dependently inhibited fluid-phase endocytosis (19-52%; P < 0.05). It inhibited PI3K-AKT signaling pathway as an upstream response in its effect on the inhibition of fluid-phase endocytosis. The inhibition of erbB1 receptor and fluid-phase endocytosis, and associated signaling by IP6, was corroborated by very strong to complete inhibition (70-100%; P < 0.05) of extracellular signal-regulated protein kinase 1/2 activation by IP6. IP6 significantly (P < 0.05) inhibited anchorage-dependent and -independent inhibition (50-100% and 30-75%, respectively) in DU145 cells. Targeting the impairment of erbB1 endocytosis and associated mitogenic signaling by IP6 in advanced and androgen-independent human PCA DU145 cells could be a useful approach for treating PCA.

Silibinin up-regulates insulin-like growth factor-binding protein 3 expression and inhibits proliferation of androgen-independent prostate cancer cells

Silibinin, a naturally occurring flavonoid antioxidant found in the milk thistle, has recently been shown to have potent antiproliferative effects against various malignant cell lines, but the underlying mechanism of action remains to be elucidated. We investigated the effect of silibinin on androgen-independent prostate cancer PC-3 cells. At pharmacologically achievable silibinin concentrations (0.02-20 microM), we observed increased insulin-like growth factor-binding protein 3 (IGFBP-3) accumulation in PC-3 cell conditioned medium and a dose-dependent increase of IGFBP-3 mRNA abundance with a 9-fold increase over baseline at 20 microM silibinin. An IGFBP-3 antisense oligodeoxynucleotide that attenuated silibinin-induced IGFBP-3 gene expression and protein accumulation reduced the antiproliferative action of silibinin. We also observed that silibinin reduced insulin receptor substrate 1 tyrosine phosphorylation, indicating an inhibitory effect on the insulin-like growth factor I receptor-mediated signaling pathway. These results suggest a novel mechanism by which silibinin acts as an antiproliferative agent and justify further work to investigate potential use of this compound or its derivatives in prostate cancer treatment and prevention.

Modulation of mitogen-activated protein kinase activation and cell cycle regulators by the potent skin cancer preventive agent silymarin

Recently we showed that the skin cancer preventive effect of silymarin involves inhibition of erbB1 activation. Here we assessed the effect of silymarin on cytoplasmic and nuclear signals employing human epidermoid carcinoma A431 cells. Silymarin treatment of cells resulted in a significant inhibition of mitogen-activated protein kinase (MAPK)/ERK1/2 activation only at lower doses, whereas higher doses activated MAPK/JNK1. These differential responses of silymarin were accompanied by its growth inhibitory and apoptotic cell death effects at low and high doses, respectively. Silymarin-caused growth inhibition was via both G2-M and G1 arrests due to a significant decrease in the kinase activity and protein levels of CDKs and cyclins. In other studies, only low doses of silymarin also showed an induction of Cip1/p21 and Kip1/p27. Together, these results identify distinct signaling pathways for the antiproliferative and apoptotic effects of silymarin and form a basis for developing strategies targeted to ERK and JNK pathways for the prevention and intervention of malignancies by silymarin.

Silibinin decreases prostate-specific antigen with cell growth inhibition via G1 arrest, leading to differentiation of prostate carcinoma cells: implications for prostate cancer intervention

Reduction in serum prostate-specific antigen (PSA) levels has been proposed as an endpoint biomarker for hormone-refractory human prostate cancer intervention. We examined whether a flavonoid antioxidant silibinin (an active constituent of milk thistle) decreases PSA levels in hormone-refractory human prostate carcinoma LNCaP cells and whether this effect has biological relevance. Silibinin treatment of cells grown in serum resulted in a significant decrease in both intracellular and secreted forms of PSA concomitant with a highly significant to complete inhibition of cell growth via a G1 arrest in cell cycle progression. Treatment of cells grown in charcoal-stripped serum and 5alpha-dihydrotestosterone showed that the observed effects of silibinin are those involving androgen-stimulated PSA expression and cell growth. Silibinin-induced G1 arrest was associated with a marked decrease in the kinase activity of cyclin-dependent kinases (CDKs) and associated cyclins because of a highly significant decrease in cyclin D1, CDK4, and CDK6 levels and an induction of Cip1/p21 and Kip1/p27 followed by their increased binding with CDK2. Silibinin treatment of cells did not result in apoptosis and changes in p53 and bcl2, suggesting that the observed increase in Cip1/p21 is a p53-independent effect that does not lead to an apoptotic cell death pathway. Conversely, silibinin treatment resulted in a significant neuroendocrine differentiation of LNCaP cells as an alternative pathway after Cip1/p21 induction and G1 arrest. Together, these results suggest that silibinin could be a useful agent for the intervention of hormone-refractory human prostate cancer.

[The significance of midline structure shifting in the patients of cerebral hemorrhage in basal ganglia by computerized tomography]

Thirty-six patients of cerebral hemorrhage in basal ganglia were studied between medline structure shifting on CT scan and assessment of clinic neurological function, defect (AND). The differences were significant between the following two groups: including in parameter A (the distance from center of hematoma to normal midline), 26.01 +/- 6.06 mm in survivor group, 21.53 +/- 5.03 mm in death group; in parameter B (the distance from the farthest point in shifted midline to the normal midline), 3.84 +/- 2.66 mm in survivor group, 10.32 +/- 4.24 mm in death group; in parameter C (ratio of the partial length of shifted midline to all length of the normal midline), 0.347 +/- 0.136 in survivor group; 0.582 +/- 0.082 in death group. Having analized these parameters, the authors found that the mortality rates were 0 and 100% if B was < or = 4.0 mm and > 10.0 mm respectively and the mortality rates were 0 and 90% if C was < or = 0.30 and > 0.50. The authors also found that there was closed correlation between the parameters B or C described midline shifting and AND.

A flavonoid antioxidant, silymarin, inhibits activation of erbB1 signaling and induces cyclin-dependent kinase inhibitors, G1 arrest, and anticarcinogenic effects in human prostate carcinoma DU145 cells

Prostate cancer (PCA) is the most common nonskin malignancy and the second leading cause of cancer deaths in United States males. One practical and translational approach to control PCA is to define a mechanism-based anticarcinogenic agent(s). Recently, we showed that silymarin, a flavonoid antioxidant isolated from milk thistle, possesses exceptionally high to complete protective effects against experimentally induced tumorigenesis. Because the epidermal growth factor receptor (erbB1) and other members of the erbB family have been shown to play important roles in human PCA, efforts should be directed to identify inhibitors of this pathway for PCA intervention. In this study, we assessed whether silymarin inhibits erbB1 activation and associated downstream events and modulates cell cycle regulatory proteins and progression, leading to growth inhibition of human prostate carcinoma DU145 cells. Treatment of serum-starved cells with silymarin resulted in a significant inhibition of transforming growth factor alpha-mediated activation of erbB1 but no change in its protein levels. Silymarin treatment of cells also resulted in a significant decrease in tyrosine phosphorylation of an immediate downstream target of erbB1, the adapter protein SHC, together with a decrease in its binding to erbB1. In the studies analyzing cell cycle regulatory molecules, silymarin treatment of cells also resulted in a significant induction of cyclin-dependent kinase inhibitors (CDKIs) Cip1/p21 and Kip1/p27, concomitant with a significant decrease in CDK4 expression, but no change in the levels of CDK2 and CDK6 and their associated cyclins E and D1, respectively. Cells treated with silymarin also showed an increased binding of CDKIs with CDKs, together with a marked decrease in the kinase activity of CDKs and associated cyclins. In additional studies, treatment of cells grown in 10% serum with anti-epidermal growth factor receptor monoclonal antibody clone 225 or different doses of silymarin also resulted in significant inhibition of constitutive tyrosine phosphorylation of both erbB1 and SHC but no change in their protein levels. Furthermore, whereas silymarin treatment resulted in a significant increase in the protein levels of both Cip1/p21 and Kip1/p27, monoclonal antibody 225 showed an increase only in Kip1/p27. These findings suggest that silymarin also inhibits constitutive activation of erbB1 and that the observed effect of silymarin on an increase in CDKI protein levels is mediated via inhibition of erbB1 activation only in the case of Kip1/p27; however, additional pathways independent of inhibition of erbB1 activation are possibly responsible for the silymarin-caused increase in Cip1/p21 in DU145 cells. In other studies, silymarin treatment also induced a G1 arrest in the cell cycle progression of DU145 cells and resulted in a highly significant to complete inhibition of both anchorage-dependent and anchorage-independent growth of DU145 cells in a dose- and time-dependent manner. Taken together, these results suggest that silymarin may exert a strong anticarcinogenic effect against PCA and that this effect is likely to involve impairment of erbB1-SHC-mediated signaling pathway, induction of CDKIs, and a resultant G1 arrest.

Anticarcinogenic effect of a flavonoid antioxidant, silymarin, in human breast cancer cells MDA-MB 468: induction of G1 arrest through an increase in Cip1/p21 concomitant with a decrease in kinase activity of cyclin-dependent kinases and associated cyclins

There is an increasing interest in identifying potent cancer preventive and therapeutic agents against breast cancer. Silymarin, a flavonoid antioxidant isolated from milk thistle, exerts exceptionally high to complete anticarcinogenic effects in tumorigenesis models of epithelial origin. In this study, we investigated the anticarcinogenic effect of silymarin and associated molecular mechanisms, using human breast carcinoma cells MDA-MB 468. Silymarin treatment resulted in a significantly high to complete inhibition of both anchorage-dependent and anchorage-independent cell growth in a dose- and time-dependent manner. The inhibitory effects of silymarin on cell growth and proliferation were associated with a G1 arrest in cell cycle progression concomitant with an induction of up to 19-fold in the protein expression of cyclin-dependent kinase (CDK) inhibitor Cip1/p21. Following silymarin treatment of cells, an incremental binding of Cip1/p21 with CDK2 and CDK6 paralleled a significant decrease in CDK2-, CDK6-, cyclin D1-, and cyclin E-associated kinase activity with no change in CDK2 and CDK6 expression but a decrease in G1 cyclins D1 and E. Taken together, these results suggest that silymarin may exert a strong anticarcinogenic effect against breast cancer and that this effect possibly involves an induction of Cip1/p21 by silymarin, which inhibits the threshold kinase activities of CDKs and associated cyclins, leading to a G1 arrest in cell cycle progression.

Novel cancer chemopreventive effects of a flavonoid antioxidant silymarin: inhibition of mRNA expression of an endogenous tumor promoter TNF alpha

In this study we describe exceptionally high protective effects of silymarin, a flavonoid antioxidant isolated from milk thistle, against 12-O-tetradecanoylphorbol 13-acetate (TPA)- and okadaic acid (OA)-caused tumor promotion in SENCAR mouse skin. Pre-application of silymarin to that of TPA in 7, 12-dimethylbenz(a)anthracene (DMBA)-initiated mouse skin resulted in almost complete protection in terms of tumor incidence (85%) as well as multiplicity (94%). In OA-caused tumor promotion studies, application of silymarin prior to that of OA in DMBA-initiated mouse skin resulted in a complete protection against tumorigenicity. We next assessed the effect of silymarin on TPA- and OA-caused induction of mRNA expression of tumor necrosis factor alpha (TNF alpha) which is an endogenous tumor promoter and a central mediator of tumor promotion in vivo in the case of both TPA and OA tumor promotion. Topical application of silymarin on mouse skin prior to that of TPA or OA resulted in a highly significant to complete inhibition in a dose-dependent manner against both TPA- and OA-caused induction of TNF alpha mRNA expression in mouse epidermis. These results indicate that silymarin exerts novel chemopreventive effects against tumorigenicity by inhibiting endogenous tumor promoter TNF alpha. Additional studies are warranted in other tumor models to further evaluate the cancer chemopreventive effect of silymarin and to define the involvement of TNF alpha as a molecular target for such an effect.