Oncogenic Signaling Pathways Activated in DMBA-Induced Mouse Mammary Tumors

Only about 5% of human breast cancers can be attributed to inheritance of breast cancer susceptibility genes, while the balance are considered to be sporadic in origin. Breast cancer incidence varies with diet and other environmental influences, including carcinogen exposure. However, the effects of environmental carcinogens on cell growth control pathways are poorly understood. Here we have examined oncogenic signaling pathways that are activated in mammary tumors in mice treated with the prototypical polycyclic aromatic hydrocarbon (PAH) 7,12-dimethylbenz[ a]anthracene (DMBA). In female FVB mice given 6 doses of 1 mg of DMBA by weekly gavage beginning at 5 weeks of age, all of the mice developed tumors by 34 weeks of age (median 20 weeks after beginning DMBA); 75% of the mice had mammary tumors. DMBA-induced mammary tumors exhibited elevated expression of the aryl hydrocarbon receptor (AhR), c- myc, cyclin D1, and hyperphosphorylated retinoblastoma (Rb) protein. Because of this, the activation of upstream regulatory pathways was assessed, and elements of the Wnt signaling pathway, the NF-κB pathway, and the prolyl isomerase Pin-1 were found to be frequently up-regulated in the tumors when compared to normal mammary gland controls. These data suggest that environmental carcinogens can produce long-lasting alterations in growth and anti-apoptotic pathways, leading to mammary tumorigenesis.

NFκB-Independent Signaling to the Cyclin D1 Gene by Rac

In this report we characterize the mechanism of Rac-mediated cyclin D1 gene expression in mouse embryonic fibroblasts. Activated Rac strongly stimulated cyclin D1 gene transcription but did not alter the half-life of cyclin D1 mRNA. Inhibition of NFkappaB signaling with the IkappaB super-repressor blocked the Rac-dependent expression of cyclin D1 mRNA, and this effect was selective since ERK-dependent cyclin D1 mRNA induction was minimally affected by super-repressor expression. However, we found that p65 activity in this system was induced by serum and not by activated Rac. Moreover, mouse cyclin D1 promoter-luciferase assays showed that Rac stimulated cyclin D1 gene expression without activating NFkappaB and that an essential Rac-regulated promoter element is located far upstream or downstream of the cyclin D1 transcription start site. We conclude that, in MEFs, Rac-mediated induction of cyclin D1 mRNA requires activation of a parallel NFkappaB pathway whereas ERK induces cyclin D1 transcription independent of NFkappaB.

CD5 negative mantle cell lymphoma: a different clinical entity?

We report herein a 77-year-old patient with CD5 negative mantle cell lymphoma (MCL). We further review the existing literature on clinicolaboratory features of this rare MCL subtype. Although most of the patients in the literature (including ours) had advanced stage at diagnosis, splenomegaly, and bone marrow involvement, they displayed prompt and durable responses to conventional treatment. We postulate that CD5 surface antigen expression could have prognostic implications in MCL. Further research and a larger number of patients are necessary in order to validate these findings.

Inverse correlation of miRNA and cell cycle-associated genes suggests influence of miRNA on benign thyroid nodule tumorigenesis

CONTEXT

The molecular etiology of cold and benign thyroid nodules (CBTNs) is largely unknown. Increased thyroid epithelial cell proliferation is a hallmark of CBTNs. MicroRNAs (miRNAs) are prominent regulators of cell proliferation.

OBJECTIVE

Our objective was to assess the influence of miRNAs on the increased proliferation and thus the molecular etiology of CBTNs.

DESIGN

By using microarrays, we defined the molecular pattern of increased proliferation of CBTNs as a differential expression of cell-cycle-associated genes and miRNAs. In silico integration of differentially expressed miRNAs and mRNAs showed an inverse correlation between the expression of 59 miRNAs and 133 mRNAs. Inverse correlations between cell-cycle-associated genes such as CDKN1C and miR-221, CCND1 and miR-31, GADD45A and miR-130b, or CDKN1A and let-7f suggest a modulation of proliferation in CBTNs by miRNAs. Their expression was validated using quantitative RT-PCR and functionally characterized in cell line models.

RESULTS

Comparative quantitative RT-PCR of 20 samples of CBTNs and their surrounding tissue revealed an 11-fold down-regulation of miR-31 with a 2.6-fold up-regulation of CCND1, and a 2.6-fold up-regulation of miR-130b with a 2.3-fold down-regulation of its target GADD45A. Using HTori and FTC-133 cell lines, we analyzed proliferation, cell cycle, and apoptosis after transfection of miRNA-31 and miRNA-130b mimic and inhibitors. Overexpression of miR-31 and the resultant down-regulation of CCND1 led to an arrest in the cell cycle phase G1. Overexpression of miR-130b led to an increase of apoptosis and necrosis within 72 h.

CONCLUSION

miR-31 and miR-130b may have an effect on tumorigenesis of CBTNs by regulating proliferation and apoptosis and the cell cycle through cyclin D1.

Krüppel-like factor 4 mediates anti-proliferative effects of progesterone with G₀/G₁ arrest in human endometrial epithelial cells

Activation of the progesterone receptor (PR) inhibits cell proliferation in various reproductive tissues. However, the molecular mechanisms underlying the regulation of cell proliferation by PR remain poorly understood. It is well established that Krüppel-like factor 4 (KLF4), a family of zinc fingercontaining transcription factors, induces cell cycle arrest in epithelial cells. In this study, we investigated whether KLF4 served as a target of PR activation during cell proliferation using human endometrial epithelial cells. PR agonists, progesterone and dienogest, were found to produce a lasting increase in the expression of KLF4 mRNA, followed by a decrease in cyclin D1 mRNA, and inhibit cell proliferation with G₀/G₁ arrest. KLF4 knockdown using KLF4 small interferingRNA abrogated the inhibition of cell proliferation by PR agonists. In addition, forced expression of KLF4 inhibited cyclin D1 promoter transactivation. These results suggest that PR agonists induce KLF4 expression and then inhibit cyclin D1 expression, and consequently inhibit cell proliferation in human endometrial epithelial cells. In terms of human reproductive tissue, KLF4 may be a factor concerning cell cycle, directly responsive to PR activation.

Neuroprotective strategies to avert seizure-induced neurodegeneration in epilepsy

Neurodegeneration in limbic circuits is a hallmark feature of chronic temporal lobe epilepsy (TLE). Studies in experimental animal models and human patients indicate that seizure-induced neuronal injury involves some active, as well as passive cell death processes. Experimental approaches that inhibit active steps in cell death programs have been shown to reduce neuronal cell death and sclerosis, but not to prevent epileptogenesis in animal models of TLE. These findings suggest that we need additional research using both animal models and brain slices from human patients to understand the pathological mechanisms underlying seizure generation. Such comparative studies will also aid in evaluating the potential therapeutic value of inhibiting cell death in seizure disorders.

Effect of a Vascular Endothelial Growth Factor (VEGF) Inhibitory Treatment on the Folliculogenesis and Ovarian Apoptosis in Gonadotropin-Treated Prepubertal Rats1

In the present study, we investigated whether vascular endothelial growth factor A (VEGFA) plays a critical intraovarian survival role in gonadotropin-dependent folliculogenesis. The effect of an intrabursal administration of a VEGFA antagonist on follicular development, apoptosis, and levels of pro- and antiapoptotic proteins of BCL2 family members (BAX, BCL2, and BCL2L1), as well as of TNFRSF6 (also known as FAS) and FAS ligand (FASLG), was examined. To inhibit VEGFA, a soluble FLT1/Fc Chimera (Trap) was administered to prepubertal eCG-treated rats. Injection of 0.5 mug of Trap per ovary did not change the number of preantral follicles (PFs) or early antral follicles (EAFs); however, it significantly decreased the number of periovulatory follicles 48 h after surgery and significantly increased the number of atretic follicles. No significant differences were found in any stage of the follicles either 12 or 24 h after injection. Cells undergoing DNA fragmentation were quantified by performing TUNEL on ovarian sections. Trap treatment caused a twofold increase in the number of apoptotic cells in EAFs. DNA isolated from antral follicles incubated for 24 h exhibited the typical apoptotic DNA pattern. Follicles obtained from Trap-treated ovaries showed a significant increase in the spontaneous onset of apoptotic DNA fragmentation. The injection of Trap significantly increased the levels of BAX and decreased the levels of BCL2 protein. The ratio of BCL2L1L:BCL2L1s was significantly diminished in follicles obtained from ovaries treated with Trap. No changes in the levels of TNFRSF6 or FASLG were observed after treatment. We concluded that the local inhibition of VEGFA activity appears to produce an increase in ovarian apoptosis through an imbalance among the BCL2 family members, thus leading a larger number of follicles to atresia.

Enhanced cell transplantation: preventing apoptosis increases cell survival and ventricular function

Cell transplantation prevents cardiac dysfunction after myocardial infarction. However, because most implanted cells are lost to ischemia and apoptosis, the benefits of cell transplantation on heart function could be improved by increasing cell survival. To examine this possibility, male Lewis rat aortic smooth muscle cells (SMCs; 4 x 10(6)) were pretreated with antiapoptotic Bcl-2 gene transfection or heat shock and then implanted into the infarcted myocardium of anesthetized, syngenic female rats (n = 23 per group). On the first day after transplantation, apoptotic SMCs were quantified by using transferase-mediated dUTP nick-end labeling staining. On days 7 and 28, grafted cell survival was quantified by using real-time PCR, and heart function was assessed with the use of echocardiography and the Langendorff apparatus. SMCs given antiapoptotic pretreatments exhibited improvements in each measure relative to controls. Apoptosis was reduced in Bcl-2-treated cells relative to all other groups (P < 0.05), whereas survival (P < 0.01) was increased. Heat shock also significantly decreased apoptosis and increased survival relative to control groups (P < 0.05 for group effect), although these effects were less pronounced than in the Bcl-2-treated group. Further, scar areas were reduced in both Bcl-2- and heat shock-treated groups relative to controls (P < 0.05), and fractional area change and cardiac function were greater (P < 0.05 for both measures). These results indicate that antiapoptosis pretreatments reduced grafted SMC loss after transplantation and enhanced grafted cell survival and ventricular function, which was directly related (r = 0.72; P = 0.002) to the number of surviving engrafted cells.

The role of apoptosis in the pathogenesis of dermatitis herpetiformis

Apoptosis is a form of cell death that is claimed to be involved in a number of chronic inflammatory and malignant skin diseases. The aim of this study was to investigate whether apoptosis may contribute to the pathogenesis of epidermal changes in dermatitis herpetiformis (DH) and, in particular, whether certain apoptosis-related markers such as Bax, Bcl-2, Fas and Fas ligand (FasL) take part in this process. For the detection of apoptotic nuclei, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling technique (TUNEL) was employed on cryostat sections. Skin lesions from six and perilesional skin from four DH patients were stained with monoclonal antibodies to Bax, Bcl-2, Fas and FasL. The same evaluation was also performed on three patients affected by bullous pemphigoid (BP) and in two healthy donors. Using TUNEL technique, a remarkable increase in the apoptotic rate within the epidermal compartment was observed in DH and BP patients in comparison with normal controls. In our immunohistochemical analysis, Bax/Bcl-2 ratio was almost the same in the epidermis of perilesional/lesional DH, BP and healthy skin specimens. In DH and BP specimens both Bax and Bcl-2 proteins were increased in the dermal perivascular compartment. Fas showed a prevalently epidermal staining, both in DH and BP lesions, while FasL was distributed in perivascular and subjunctional dermis; some FasL+ cells infiltrated the DEJ and the basal layer of epidermis. This study allowed us to highlight conspicuous apoptotic phenomena in basal and suprabasal keratinocytes within lesional and perilesional skin of DH. We conclude that in DH, as well as in BP, apoptosis plays a role in the pathogenesis of cutaneous lesions in concert with other pathogenetic mechanisms.

Microarray analysis of altered gene expression in murine fibroblasts transformed by nickel(II) to nickel(II)-resistant malignant phenotype

B200 cells are Ni(II)-transformed mouse BALB/c-3T3 fibroblasts displaying a malignant phenotype and increased resistance to Ni(II) toxicity. In an attempt to find genes whose expression has been altered by the transformation, the Atlas Mouse Stress/Toxicology cDNA Expression Array (Clontech Laboratories, Inc., Palo Alto, CA) was used to analyze the levels of gene expression in both parental and Ni(II)-transformed cells. Comparison of the results revealed a significant up- or downregulation of the expression of 62 of the 588 genes present in the array (approximately 10.5%) in B200 cells. These genes were assigned to different functional groups, including transcription factors and oncogenes (9/14; fractions in parentheses denote the number of up-regulated versus the total number of genes assigned to this group), stress and DNA damage response genes (11/12), growth factors and hormone receptors (6/9), metabolism (7/7), cell adhesion (2/7), cell cycle (3/6), apoptosis (3/4), and cell proliferation (2/3). Among those genes, overexpression of beta-catenin and its downstream targets c-myc and cyclin D1, together with upregulated cyclin G, points at the malignant character of B200 cells. While the increased expression of glutathione (GSH) synthetase, glutathione-S-transferase A4 (GSTA4), and glutathione-S-transferase theta (GSTT), together with high level of several genes responding to oxidative stress, suggests the enforcement of antioxidant defenses in Ni-transformed cells.

Diagnostic role and prognostic significance of a simplified immunophenotypic classification of mature B cell chronic lymphoid leukemias

We verified the diagnostic and prognostic role of a simplified immunophenotypic classification (IC) in a series of 258 patients (M/F: 1.4; median age: 64 years; median follow-up: 64 months; 75 deaths) with mature B cell lymphoid leukemias (MBC-LL) for whom no histopathological diagnosis was available because of minimal or no lymph node involvement. The IC was based on the reactivity of three pivotal immunophenotypic markers: CD5, CD23 and SIg intensity. On the basis of different expression patterns, we identified four diagnostic clusters (C) characterized by distinct clinico-biological features and different prognoses: C1 (149 patients) identified most classical B cell chronic lymphocytic leukemias (CLL-type cluster; SIg(dim)/CD5+/CD23+); C2, 38 patients whose clinico-hematological characteristics were intermediate between C1 and C3 (CLL-variant cluster; SIg(bright)/CD5+/CD23+/-or SIg(dim)/CD5-/-/CD23 indifferent); C3 (16 patients) most situations consistent with mantle cell lymphoma in leukemic phase (MCL-type cluster; SIg(bright)/CD5+/CD23-); and C4, 55 cases, most of whom were consistent with leukemic phase lymphoplasmacytic/splenic marginal zone lymphomas (LP/S-type cluster; SIg(bright)/CD5-/+/CD23 indifferent). At univariate survival analysis, prognosis worsened from C1 to C4, C2 and C3 (P = 0.0001), and this was maintained at multivariate analysis (P = 0.006), together with CD11c expression (P = 0.0043), age at diagnosis (cut-off 70 years; P = 0.0008) and platelet count (cut-off 140 x 10(9)/l; P = 0.0034). Besides recognising the two well-known situations of classic B-CLL and MCL, our IC identified situations with distinct prognostic and/or clinical behaviors.

Involvement of bcl-family expression in the spatial memory impairment induced by repeated ischemia

In the present study, we examined the effects of repeated ischemia (10 min x 2, 1 hr interval) on spatial memory in rats in an 8-arm radial maze test compared with single ischemia (10 min x 1). Repeated ischemia produced more severe impairment of spatial memory and stronger TUNEL-positive immunoreactivity in the hippocampal CA1 region than single ischemia at 7 days after reperfusion. Moreover, repeated ischemia altered bcl-family expression, which is related to apoptosis, while this was not affected by single ischemia. These results suggest that spatial memory impairment at 7 days after repeated ischemia may be related to apoptosis in hippocampal CA1 cells.

AIB1 enhances estrogen-dependent induction of cyclin D1 expression

AIB1 was isolated as a gene amplified in breast cancer and encodes a protein that acts as a steroid receptor coactivator. The role of steroid receptor coactivators such as AIB1 in breast cancer development is not clear. It is possible that AIB1 cooperates with estrogen receptor alpha in regulating estrogen-dependent cell proliferation. Ectopic expression of the estrogen receptor alpha in different cell lines does not confer estrogen-induced proliferation. This inability of the estrogen receptor to drive proliferation has been recently correlated with a lack of estrogen-dependent cyclin D1 expression in cells engineered to express the estrogen receptor. In this study, we evaluated whether high levels of AIB1 enable the estrogen receptor to direct the transcription of cyclin D1. We show here that AIB1 and other steroid receptor coactivators can enhance the functional interaction of the estrogen receptor with the cyclin D1 promoter. Increases of AIB1 levels in breast cancer cells by amplification and/or overexpression may represent one way to confer estrogen-dependent mitogenic stimulation to breast cancer cells.