Increased expression of cyclin D1, cyclin E and p21(Cip1) associated with decreased expression of p27(Kip1) in chemically induced rat mammary carcinogenesis

Anti-Estrogenic and Anti-Cell Proliferative Effect of Allyl Isothiocyanate in Chemoprevention of Chemically Induced Mammary Carcinogenesis in Rats

The anti-estrogenic and anti-cell proliferative effect of allyl isothiocyanate (AITC) was carried out by analyzing the status of sex hormones and its receptors and cell proliferative markers in chemically induced mammary carcinogenesis in rats. Mammary tumor was induced by a single dose of DMBA (25 mg/rat) and MNU (50 mg/kg bw) injected subcutaneously near mammary gland. RT-PCR, western blotting and immunohistochemical analysis of mammary tissues show an upregulation of ER-α, PR, aromatase, PCNA, cyclin D1 and AgNORs staining and down regulation of p53 expression as well as plasma estradiol, prolactin and testosterone levels increased in DMBA and MNU-induced tumor bearing rats. Oral administration of AITC at a dose of 20 mg/kg bw restored the levels of sex hormones and its receptors, aromatase, cell proliferative markers and AgNORs staining near to normal levels. Molecular docking studies also supported these findings. The results suggest that anti-estrogenic and anti-proliferative effect of AITC prevent the development of DMBA and MNU-induced mammary carcinogenesis in rat.

Effect of Crocin on Cell Cycle Regulators in N-Nitroso-N-Methylurea-Induced Breast Cancer in Rats

We previously showed the anticancer effect of crocin, a saffron carotenoid, in both breast and gastric cancers in animal models, but its mechanism of action is not clearly known, yet. In this study, the effect of crocin on cell cycle regulators is investigated. Female Wistar Albino rats were divided into two groups, with or without N-nitroso-N-methylurea (NMU) injection. After tumor formation, each group of rats was divided into two subgroups, receiving crocin or vehicle only. After 5 weeks, the rats were sacrificed and the tumors were retained for pathologic investigation and determination of the parameters. Before crocin treatment, the tumor volumes were 13.27±3.77 and 12.37±1.88, but at the end of the experiment, they were 23.66±8.82 and 11.91±2.27 in the control and crocin-treated groups, respectively. Pathologic investigation indicated the adenocarcinoma induction by NMU. Reverse transcription-polymerase chain reaction and Western blot analysis showed overexpression of cyclin D1 and p21(Cip1) in the NMU-induced breast tumors; however, the expression of both of them suppressed by crocin treatment. The previous studies indicated that crocin induces apoptosis in tumor tissue. In this study, we show that it also suppresses tumor growth and induces cell cycle arrest by downregulation of cyclin D1. In addition, crocin suppressed p21(Cip1) in a p53-dependent manner.

Epigenetic regulation of embryonic stem cell marker miR302C in human chondrosarcoma as determinant of antiproliferative activity of proline-rich polypeptide 1

Metastatic chondrosarcoma of mesenchymal origin is the second most common bone malignancy and does not respond either to chemotherapy or radiation; therefore, the search for new therapies is relevant and urgent. We described recently that tumor growth inhibiting cytostatic proline-rich polypeptide 1, (PRP-1) significantly upregulated tumor suppressor miRNAs, downregulated onco-miRNAs in human chondrosarcoma JJ012 cell line, compared to chondrocytes culture. In this study we hypothesized the existence and regulation of a functional marker in cancer stem cells, correlated to peptides antiproliferative activity. Experimental results indicated that among significantly downregulated miRNA after PRP-1treatment was miRNAs 302c^*. This miRNA is a part of the cluster miR302-367, which is stemness regulator in human embryonic stem cells and in certain tumors, but is not expressed in adult hMSCs and normal tissues. PRP-1 had strong inhibitory effect on viability of chondrosarcoma and multilineage induced multipotent adult cells (embryonic primitive cell type). Unlike chondrosarcoma, in glioblastoma, PRP-1 does not have any inhibitory activity on cell proliferation, because in glioblastoma miR-302-367 cluster plays an opposite role, its expression is sufficient to suppress the stemness inducing properties. The observed correlation between the antiproliferative activity of PRP-1 and its action on downregulation of miR302c explains the peptides opposite effects on the upregulation of proliferation of adult mesenchymal stem cells, and the inhibition of the proliferation of human bone giant-cell tumor stromal cells, reported earlier. PRP-1 substantially downregulated the miR302c targets, the stemness markers Nanog, c-Myc and polycomb protein Bmi-1. miR302c expression is induced by JMJD2-mediated H3K9me2 demethylase activity in its promoter region. JMJD2 was reported to be a positive regulator for Nanog. Our experimental results proved that PRP-1 strongly inhibited H3K9 activity comprised of a pool of JMJD1 and JMJD2. We conclude that inhibition of H3K9 activity by PRP-1 leads to downregulation of miR302c and its targets, defining the PRP-1 antiproliferative role.

Trianthema portulacastrum Linn. exerts chemoprevention of 7,12-dimethylbenz(a)anthracene-induced mammary tumorigenesis in rats

Due to limited treatment options for advanced-stage metastatic breast cancer, a high priority should be given to develop non-toxic chemopreventive drugs. The value of various natural and dietary agents to reduce the risk of developing breast cancer is well established. Trianthema portulacastrum Linn. (Aizoaceae), a dietary and medicinal plant, has been found to exert antihepatotoxic and antihepatocarcinogenic properties in rodents. This study was initiated to investigate mechanism-based chemopreventive potential of an ethanolic extract of T. portulacastrum (TPE) against 7,12-dimethylbenz(a)anthracene (DMBA)-initiated rat mammary gland carcinogenesis, an experimental tumor model that closely resembles human breast cancer. Rats had access to a basal diet supplemented with TPE to yield three dietary doses of the extract, i.e., 50, 100 and 200 mg/kg body weight. Following two weeks of TPE treatment, mammary tumorigenesis was initiated by oral administration of DMBA (50 mg/kg body weight). At the end of the study (16 weeks after DMBA exposure), TPE exhibited a striking reduction of DMBA-induced mammary tumor incidence, total tumor burden and average tumor weight and reversed intratumor histopathological alterations. TPE dose-dependently suppressed proliferating cell nuclear antigen and cyclin D1 expression, induced apoptosis, upregulated proapoptotic protein Bax, downregulated antiapoptotic protein Bcl-2 and diminished the expression of nuclear and cytosolic β-catenin in mammary tumors. Our results clearly provide the first experimental evidence that TPE exerts chemopreventive effect in the classical DMBA model of breast cancer by suppressing abnormal cell proliferation and inducing apoptosis mediated through alteration of Bax/Bcl-2 ratio. Mechanistically, TPE is capable of diminishing activated canonical Wnt/β-catenin signaling to exhibit antiproliferative, proapoptotic and oncostatic effects during an early-stage breast cancer. These results may encourage further studies to explore full potential of T. portulacastrum phytoconstituents as breast cancer chemopreventive agents.

Simultaneous disruption of estrogen receptor and Wnt/β-catenin signaling is involved in methyl amooranin-mediated chemoprevention of mammary gland carcinogenesis in rats

Methyl-amoorain (methyl-25-hydroxy-3-oxoo-lean-12-en-28-oate, AMR-Me), a novel synthetic oleanane triterpenoid, exerts a striking chemopreventive effect against 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary tumorigenesis through antiproliferative and proapoptotic actions. Nevertheless, the underlying mechanisms of action remain to be established. As estrogen receptor (ER) and canonical Wnt/b-catenin signaling are involved in the development and progression of breast cancer, the current study was designed to investigate the effects of AMR-Me treatment on the expressions of ER-a, ER-b, b-catenin and cyclin D1 in rat mammary tumors induced by DMBA. Mammary tumor samples were harvested from an 18-week chemopreventive study in which AMR-Me (0.8–1.6 mg/kg) was shown to inhibit mammary carcinogenesis in a dose–response manner. The expressions of ER-a, ER-b, b-catenin, and cyclin D1 were determined by immunohistochemistry and reverse transcription-polymerase chain reaction. AMR-Me downregulated the expression of intratumor ER-a and ER-b and lowered the ratio of ER-a to ER-b. AMR-Me also reduced the expression, cytoplasmic accumulation, and nuclear translocation of b-catenin, the essential transcriptional cofactor for Wnt signaling. Furthermore, AMR-Me modulated the expression of cell growth regulatory gene cyclin D1, which is a downstream target for both ER and Wnt signaling. AMR-Me at 1.6 mg/kg for 18 weeks did not exhibit any hepatotoxicity or renotoxicity. The results of the present study coupled with our previous findings indicate that simultaneous disruption of ER and Wnt/b-catenin signaling possibly contributes to antiproliferative and apoptosis-inducing effects implicated in AMR-Me-mediated chemoprevention of DMBA-induced breast tumorigenesis in rats. Our results also suggest a possible crosstalk between two key regulatory pathways, namely ER and Wnt/b-catenin signaling, involved in mammary carcinogenesis and the value of simultaneously targeting these pathways to achieve breast cancer chemoprevention.

High Expression of Cyclin D1 and p21 in N-Nitroso-N-Methylurea-Induced Breast Cancer in Wistar Albino Female Rats

OBJECTIVE

N-nitroso-N-methylurea (NMU) induces breast cancer in rodents, particularly in rats. This model of breast cancer is very similar to human breast cancer. As a continuation of our recent work, we investigated the expressions of cyclin D1 and p21 in NMU-induced breast cancer of Wistar Albino rats.

MATERIALS AND METHODS

In this experimental study, mammary carcinoma was induced in female Wistar Albino rats by a new protocol which included the intraperitoneal injection of NMU (50 mg/kg) at 50, 65, and 80 days of the animal's age. The animals were weighed weekly and palpated in order to record the numbers, location, and size of tumors. Subsequently tumor incidence (TI), latency period (LP), and tumor multiplicity (TM) were reported. About four weeks after the tumor size reached 1.5 cm3, rats were sacrificed. Cyclin D1 and p21 expressions in tumors and normal mammary glands from normal rats were measured by reverse-transcription polymerase chain reaction (RT- PCR) and Western blot analysis. Statistical analysis of the data was performed using SPSS software version 16.0.

RESULTS

The efficiency of tumor induction was 65%, LP was 150 days, and a TM of 1.43 ± 0.53 per rat was noted. RT-PCR and Western blot data indicated significant (p<0.05) induction of both cyclin D1 and p21 expressions in rat mammary tumors compared with normal tissue from the control group.

CONCLUSION

These results indicate an efficient mammary tumor induction protocol for this type of rat, which is accompanied by an increase in cyclin D1 and p21 expressions.

Dual targeting of CDK and tropomyosin receptor kinase families by the oral inhibitor PHA-848125, an agent with broad-spectrum antitumor efficacy

Altered expression and activity of cyclin-dependent kinase (CDK) and tropomyosin receptor kinase (TRK) families are observed in a wide variety of tumors. In those malignancies with aberrant CDK activation, the retinoblastoma protein (pRb) pathway is deregulated, leading to uncontrolled cell proliferation. Constitutive activation of TRKs is instead linked to cancer cell survival and dissemination. Here, we show that the novel small-molecule PHA-848125, a potent dual inhibitor of CDKs and TRKs, possesses significant antitumor activity. The compound inhibits cell proliferation of a wide panel of tumoral cell lines with submicromolar IC(50). PHA-848125-treated cells show cell cycle arrest in G(1) and reduced DNA synthesis, accompanied by inhibition of pRb phosphorylation and modulation of other CDK-dependent markers. The compound additionally inhibits phosphorylation of TRKA and its substrates in cells, which functionally express this receptor. Following oral administration, PHA-848125 has significant antitumor activity in various human xenografts and carcinogen-induced tumors as well as in disseminated primary leukemia models, with plasma concentrations in rodents in the same range as those found active in inhibiting cancer cell proliferation. Mechanism of action was also confirmed in vivo as assessed in tumor biopsies from treated mice. These results show that the dual CDK-TRK inhibitor PHA-848125 has the potential for being a novel and efficacious targeted drug for cancer treatment.

Review of the etiology of breast cancer with special attention to organochlorines as potential endocrine disruptors

Breast cancer is the most frequently diagnosed cancer among Canadian women, accounting for about 30% of all new cancer cases each year. Although the incidence of breast cancer has increased over the past 50 years, the cause of this rise is unknown. Risk factors for breast cancer may be classified into four broad categories: (1) genetic/familial, (2) reproductive/hormonal, (3) lifestyle, and (4) environmental. Established risk factors for breast cancer include older age, later age at first full-term pregnancy, no full-term pregnancies, postmenopausal obesity, and genetic factors. However, these known risk factors cannot account for the majority of cases. In the early 1990s, it was suggested that exposure to some environmental chemicals such as organochlorine compounds may play a causal role in the etiology of breast cancer through estrogen-related pathways. The relationship between organochlorines and breast cancer risk has been studied extensively in the past decade and more, and at this point there is no clear evidence to support a causal role of most organochlorine pesticides in the etiology of human breast cancer, but more evidence is needed to assess risk associated with polychlorinated biphenyls (PCBs). Future studies need to consider the combined effects of exposures, concentrate on vulnerable groups such as those with higher levels of exposure, only consider exposures occurring during the most etiologically relevant time periods, and more thoroughly consider gene-environment interactions.

Comparative evaluation of antiproliferative, antiangiogenic and apoptosis inducing potential of black tea polyphenols in the hamster buccal pouch carcinogenesis model

BACKGROUND

To evaluate the relative chemopreventive efficacy of two black tea polyphenols, Polyphenon-B [P-B] and BTF-35 on 7,12-dimethylbenz [a]anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis.

METHODS

Hamsters were divided into 6 groups. The right buccal pouches of animals in groups 1-3 were painted with 0.5% of DMBA three times a week for 14 weeks. While hamsters in group 1 received no further treatment, animals in groups 2 and 3 received diet containing 0.05% P-B and BTF-35 respectively, four weeks before DMBA painting that was continued until the end of the experiments. Animals in groups 4 and 5 were given P-B and BTF-35 alone respectively as in groups 2 and 3. Group 6 animals served as the untreated control. All the animals were sacrificed after 18 weeks. The expression of p21, cyclin D1, glutathione S-transferase pi (GST-P), nuclear factor kappa B (NF-kappaB), Bcl-2, Bax, cytochrome C, caspase-3, caspase-9, poly(ADP-ribose) polymerase (PARP), cytokeratins and vascular endothelial growth factor (VEGF) was analysed by RT-PCR, immunohistochemical and Western blot analyses.

RESULTS

DMBA treated animals developed buccal pouch carcinomas that displayed increased expression of p21, cyclin D1, GST-P, NF-kappaB, cytokeratins, VEGF and Bcl-2 with decreased expression of Bax, cytochrome C, caspase-3, caspase-9, and PARP. Dietary administration of both P-B and BTF-35 reduced the incidence of DMBA-induced HBP carcinomas by modulating markers of cell proliferation, cell survival, tumour infiltration, angiogenesis, and apoptosis.

CONCLUSION

The results of the present study provide a mechanistic basis for the chemopreventive potential of black tea polyphenols. The greater efficacy of BTF-35 in inhibiting HBP carcinogenesis and modulating multiple molecular targets may have a potential role in the prevention of oral cancer.

Mice expressing a mammary gland-specific R270H mutation in the p53 tumor suppressor gene mimic human breast cancer development

The tumor suppressor gene p53 has an apparent role in breast tumor development in humans, as approximately 30% of sporadic tumors acquire p53 mutations and Li-Fraumeni syndrome patients carrying germ line p53 mutations frequently develop breast tumors at early age. In the present study, conditional expression of a targeted mutation is used to analyze the role of the human R273H tumor-associated hotspot mutation in p53 in mammary gland tumorigenesis. Heterozygous p53(R270H/+)WAPCre mice (with mammary gland-specific expression of the p53.R270H mutation, equivalent to human R273H, at physiologic levels) develop mammary tumors at high frequency, indicating that the R270H mutation predisposes for mammary gland tumor development and acts in a dominant-negative manner in early stages of tumorigenesis. Spontaneous tumor development in these mice is further accelerated by 7,12-dimethylbenz(a)anthracene (DMBA) treatment at young age. The majority of spontaneous and DMBA-induced carcinomas and sarcomas from p53(R270H/+)WAPCre mice is estrogen receptor alpha positive, and expression profiles of genes also implicated in human breast cancer appear similarly altered. As such, p53(R270H/+)WAPCre mice provide a well-suited model system to study the role of p53 in breast tumorigenesis and the responsiveness of mammary gland tumors to chemotherapeutics.

Increased expression of MDM2, cyclin D1, and p27Kip1 in carcinogen-induced rat mammary tumors

It is thought that environmental pollutants, such as polycyclic aromatic hydrocarbons (PAH), contribute to human breast tumorigenesis, yet their roles remain incompletely elucidated. The prototypical PAH 7,12-dimethylbenz(alpha)anthracene (DMBA) specifically and effectively induces mammary tumor formation in rodent models. In an attempt to explore the molecular mechanisms by which PAH initiates and promotes mammary tumorigenesis, we examined the expression of several cell cycle regulators in rat mammary tumors induced by DMBA. Expression of cyclin D1, murine double minute-2 (MDM2), and Akt was up-regulated in tumors in comparison to normal mammary glands, as indicated by RT-PCR, Western blot analysis, and immunohistochemical staining. Expression of p27Kip1 protein was also elevated in the tumors with increased cytoplasmic localization. However, RB protein remained hyperphosphorylated. To directly test the effects of DMBA, the MCF-7 human breast cancer cells were treated. DMBA induced MDM2 expression in a dose- and time-dependent fashion in the MCF-7 cells, and this activation appeared to be p53 dependent. These data suggest that activation of cyclin D1, MDM2, and AKT as well as increased expression and cytoplasmic localization of p27Kip1 may play a role in this model of environmental pollutant-induced mammary tumorigenesis.

Possible role of Stat5a in rat mammary gland carcinogenesis

Signal transducer and activator of transcription (Stat) 5a is a transcription factor mediating the action of specific cytokines, growth factors and hormones on gene expression. In the mammary gland, Stat5a is well recognized for its function in prolactin signaling, lobuloalveolar development, and milk protein expression during pregnancy and lactation. Latent cytoplasmic Stat5a is activated by tyrosine phosphorylation and following dimerization undergoes nuclear import. In the current study, Stat5a expression was examined immunohistochemically in carcinomas induced by the chemical carcinogens 7,12-dimethylbenz[a]anthracene and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. A high percentage of carcinomas showed nuclear labeling of Stat5a [44 of 68 (65%)] with Stat5a nuclear labeling index ranging from 18 to 77%. In contrast, control normal mammary gland tissue displayed cytosolic expression. Carcinomas with different Stat5a staining patterns (cytoplasmic or nuclear) showed a statistical difference for the proliferating cell nuclear antigen (PCNA) labeling, tumor differentiation, nuclear grade, mitotic activity, and tumor size. High Stat5a nuclear expression was closely correlated with the higher-grade carcinomas. Stat5a nuclear expression was also detected in intraductal proliferations (10 of 21 lesions) and in ductal carcinomas in situ (13 of 15 lesions). Immunohistochemical analysis was further carried out in human breast cancers. Stat5a nuclear expression was detected in ductal and lobular carcinomas and DCIS at a frequency of 48% (15/31), 33% (2/6), and 40% (2/5), respectively. Nuclear expression of Stat5a in human breast cancers also correlated with the PCNA nuclear labeling index. The findings implicate activated Stat5a in mammary gland cancer development in the rat and human.

Cyclin D1, p53, and p21Waf1/Cip1 expression is predictive of poor clinical outcome in serous epithelial ovarian cancer

PURPOSE

Dysregulation of cell cycle control, in particular G(1)-S-phase transition, is implicated in the pathogenesis of most human cancers, including epithelial ovarian cancer (EOC). However, the prognostic significance of aberrant cell cycle gene expression in EOC remains unclear.

EXPERIMENTAL DESIGN

The expression of selected genes from the pRb pathway that regulates G(1)-S-phase progression, including cyclin D1, p16(Ink4a), cyclin E, p27(Kip1), p21(Waf1/Cip1), and p53, was examined in a consecutive series of 134 serous EOC using immunohistochemistry and the results correlated to disease outcome.

RESULTS

Molecular markers predictive of reduced overall survival in univariate analysis were overexpression of cyclin D1 (P = 0.03) and p53 (P = 0.03) and reduced expression of p27(Kip1) (P = 0.05) and p21(Waf1/Cip1) (P = 0.02), with the latter three also being prognostic for a shorter progression-free interval. In addition, patients displaying overexpression of p53 with concurrent loss of p21(Waf1/Cip1) had a significantly shorter overall (P = 0.0008) and progression-free survival (P = 0.0001). On multivariate analysis, overexpression of cyclin D1 and combined loss of p21(Waf1/Cip1) in the presence of p53 overexpression were independent predictors of overall survival. Similarly, the combination of p21(Waf1/Cip1) loss and p53 overexpression was independently predictive of a shorter progression-free interval. Overexpression of p53 and cyclin E and reduced expression of p27(Kip1) and p21(Waf1/Cip1) were significantly associated with increasing tumor grade.

CONCLUSIONS

This study confirms that dysregulation of cell cycle genes is common in EOC, and that aberrant expression of critical cell cycle regulatory proteins can predict patient outcome in serous EOC.

Characterization of gene expression induced by RET with MEN2A or MEN2B mutation

Germ-line point mutations of the RET gene are responsible for multiple endocrine neoplasia (MEN) type 2A and 2B that develop medullary thyroid carcinoma and pheochromocytoma. We performed a differential display analysis of gene expression using NIH 3T3 cells expressing the RET-MEN2A or RET-MEN2B mutant proteins. As a consequence, we identified 10 genes induced by both mutant proteins and eight genes repressed by them. The inducible genes include cyclin D1, cathepsins B and L, and cofilin genes that are known to be involved in cell growth, tumor progression, and invasion. In contrast, the repressed genes include type I collagen, lysyl oxidase, annexin I, and tissue inhibitor of matrix metalloproteinase 3 (TIMP3) genes that have been implicated in tumor suppression. In addition, six RET-MEN2A- and five RET-MEN2B-inducible genes were identified. Among 21 genes induced by RET-MEN2A and/or RET-MEN2B, six genes including cyclin D1, cathepsin B, cofilin, ring finger protein 11 (RNF11), integrin-alpha6, and stanniocalcin 1 (STC1) genes were also induced in TGW human neuroblastoma cells in response to glial cell line-derived neurotrophic factor stimulation. Because the STC1 gene was found to be highly induced by both RET-MEN2B and glial cell line-derived neurotrophic factor stimulation, and the expression of its product was detected in medullary thyroid carcinoma with the MEN2B mutation by immunohistochemistry, this may suggest a possible role for STC1 in the development of MEN 2B phenotype.

Chemically induced rat mammary tumor treated with tamoxifen showed decreased expression of cyclin D1, cyclin E, and p21(Cip1)

We studied the effects of tamoxifen (TAM) on the growth of 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary tumor and the expression of cyclin D1, cyclin E, p21(Cip1), and estrogen receptors (ER) by performing immunohistochemistry and Western blot analysis. When tumor size reached between 10 and 15mm in the largest dimension, the rats were divided into a DMBA-control group and a DMBA-TAM group. The administration of TAM markedly decreased the tumor development and showed decreased expression of bromodeoxyuridine, cyclin D1, cyclin E, and p21(Cip1) when compared with those of the DMBA-control group; however, a few tumors showed progressive growth in spite of TAM treatment. These tumors had decreased expression of ER. This study suggests that TAM suppresses tumor development through the down-expression of cyclin D1 and cyclin E.