Effect of 3 years' free-air exposure to elevated ozone on mature Norway spruce (Picea abies (L.) Karst.) needle epicuticular wax physicochemical characteristics

We examined the effect of ozone (O(3)) on Norway spruce (Picea abies) needle epicuticular wax over three seasons at the Kranzberg Ozone Fumigation Experiment. Exposure to 2x ambient O(3) ranged from 64.5 to 74.2 microl O(3) l(-1) h AOT40, and 117.1 to 123.2 nl O(3) l(-1) 4th highest daily maximum 8-h average O(3) concentration. The proportion of current-year needle surface covered by wax tubes, tube aggregates, and plates decreased (P=0.011) under 2x O(3). Epistomatal chambers had increased deposits of amorphous wax. Proportion of secondary alcohols varied due to year (P=0.004) and O(3) treatment (P=0.029). Secondary alcohols were reduced by 9.1% under 2x O(3). Exposure to 2x O(3) increased (P=0.037) proportions of fatty acids by 29%. Opposing trends in secondary alcohols and fatty acids indicate a direct action of O(3) on wax biosynthesis. These results demonstrate O(3)-induced changes in biologically important needle surface characteristics of 50-year-old field-grown trees.

The VHL tumor suppressor inhibits expression of the IGF1R and its loss induces IGF1R upregulation in human clear cell renal carcinoma

Clear cell renal cell cancer (CC-RCC) is a highly chemoresistant tumor characterized by frequent inactivation of the von Hippel-Lindau (VHL) gene. The prognosis is reportedly worse in patients whose tumors express immunoreactive type I insulin-like growth factor receptor (IGF1R), a key mediator of tumor cell survival. We aimed to investigate how IGF1R expression is regulated, and found that IGF1R protein levels were unaffected by hypoxia, but were higher in CC-RCC cells harboring mutant inactive VHL than in isogenic cells expressing wild-type (WT) VHL. IGF1R mRNA and promoter activities were significantly lower in CC-RCC cells expressing WT VHL, consistent with a transcriptional effect. In Sp1-null Drosophila Schneider cells, IGF1R promoter activity was dependent on exogenous Sp1, and was suppressed by full-length VHL protein (pVHL) but only partially by truncated VHL lacking the Sp1-binding motif. pVHL also reduced the stability of IGF1R mRNA via sequestration of HuR protein. Finally, IGF1R mRNA levels were significantly higher in CC-RCC biopsies than benign kidney, confirming the clinical relevance of these findings. Thus, we have identified a new hypoxia-independent role for VHL in suppressing IGF1R transcription and mRNA stability. VHL inactivation leads to IGF1R upregulation, contributing to renal tumorigenesis and potentially also to chemoresistance.

Free-air exposure systems to scale up ozone research to mature trees

Because seedlings and mature trees do not necessarily respond similarly to O(3) stress, it is critically important that exposure systems be developed that allow exposure of seedlings through to mature trees. Here we describe three different O(3) Free-Air Exposure Systems that have been used successfully for exposure at all growth stages. These systems of spatially uniform O(3) release have been shown to provide reliable O(3) exposure with minimal, if any, impact on the microclimate. This methodology offers a welcome alternative to chamber studies which had severe space constraints precluding stand or community-level studies and substantial chamber effects on the microclimate and, hence physiological tree performance.

Insulin-like growth factor-I controls BRCA1 gene expression through activation of transcription factor Sp1

The insulin-like growth factors (IGFs) have a central role in mammary gland growth and differentiation as well as in breast cancer development. The BRCA1 gene encodes a pleiotropic protein that functions as a transcription factor. Germline BRCA1 mutations are associated with inherited predisposition to breast and ovarian cancer and confer a substantially increased risk for developing these neoplasms. Several lines of evidence led us to hypothesize that there is a functional interaction between the BRCA1 and IGF-I systems relevant to breast cancer biology. The present study tested the notion that BRCA1 gene expression is regulated by the IGF-I signaling pathway. Results of Western immunoblotting and RT-PCR analyses show that IGF-I stimulates BRCA1 protein and mRNA levels. Transient transfection experiments using BRCA1 promoter-luciferase reporter constructs reveal that IGF-I enhances BRCA1 promoter activity, suggesting that the effect of IGF-I is mediated at the transcriptional level. In addition, we provide evidence that the Sp1 zinc-finger protein is directly involved in BRCA1 gene transactivation. Combined, our data suggests that, at least part of the biological actions of IGF-I in mammary gland cells may be mediated through BRCA1. Dysregulated BRCA1 expression resulting from aberrant IGF signaling may have important consequences relevant to breast cancer pathogenesis.

Cancer risk among parents and siblings of patients with schizophrenia

BACKGROUND

A reduced risk of cancer has been noted among people with schizophrenia. Given that genetic causes have been proposed as an explanation of this finding, one would expect that the risk of cancer among first-degree relatives would be equally reduced.

AIMS

To investigate the risk of cancer among the biological parents and full siblings of people receiving in-patient care for schizophrenia.

METHOD

Linkage analysis was conducted between national population, psychiatric and cancer databases. Standardised incidence ratios for all cancer sites were calculated by comparing the incident rates among first-degree relatives with national incidence rates.

RESULTS

A reduced cancer risk was found across all groups examined. Among parents, whose numbers were adequately large, the findings reached statistical significance. For index cases and siblings--a markedly younger population--only a trend was elicited.

CONCLUSIONS

The genetic hypothesis--namely, the presence of a gene with the dual effect of reducing the cancer risk and disrupting neurodevelopment--is a plausible explanation for these findings.

Folic acid and its metabolites modulate IGF-I receptor gene expression in colon cancer cells in a p53-dependent manner

The insulin-like growth factor-I receptor (IGF-IR) has an important role in colorectal cancer development and progression. IGF-IR displays a potent anti-apoptotic activity and is overexpressed in primary tumors and colon cancer-derived cell lines. Folic acid, a member of the vitamin B family, is a chemopreventive agent whose deficiency has been linked to an enhanced colon cancer risk. The present study was aimed at testing the hypothesis that part of the modulatory effect of folic acid on malignant transformation may be attributed to its ability to regulate IGF-IR gene expression. Regulation of IGF-IR gene expression by folic acid was assessed using western blots, RT-PCR, transient transfections and chromatin immunoprecipitation assays. Activation of the IGF-IR signaling pathway was evaluated by measuring phosphorylation of ERK, and apoptosis was assayed using poly (ADP-ribose) polymerase cleavage and annexin V-FITC staining. Results obtained showed that folic acid induced a dose-dependent decrease in IGF-IR protein and mRNA levels in the HCT116 +/+ colon cancer cell line. This effect was associated with a significant reduction in IGF-IR promoter activity. Similar effects were elicited by the folic acid metabolites dihydrofolic acid and tetrahydrofolic acid. In addition, folic acid abrogated the IGF-I-stimulated phosphorylation of the downstream signaling molecule ERK1/2 and exhibited a pro-apoptotic activity. Moreover, folic acid induced a significant decrease in Sp1 binding to the IGF-IR promoter region. Finally, folic acid had no effect in wild-type p53-depleted HCT116 -/- and Caco-2 cells. In conclusion, the mechanism of action of folic acid involves regulation of IGF-IR gene expression. The ability of folic acid to downregulate the IGF-I signal transduction pathway may allow the micronutrient to function as a chemopreventive agent. Folic acid deficiency, on the other hand, may lead to increased IGF-IR gene expression, with ensuing pathological activation by endocrine and/or autocrine/paracrine IGF-I.