Alternative splicing of pre-messenger RNA is a key feature of transcriptome expansion in eukaryotic cells, yet its regulation is poorly understood. Spliceosome assembly occurs co-transcriptionally, raising the possibility that DNA structure may directly influence alternative splicing. Supporting such an association, recent reports have identified distinct histone methylation patterns, elevated nucleosome occupancy and enriched DNA methylation at exons relative to introns. Moreover, the rate of transcription elongation has been linked to alternative splicing. Here we provide the first evidence that a DNA-binding protein, CCCTC-binding factor (CTCF), can promote inclusion of weak upstream exons by mediating local RNA polymerase II pausing both in a mammalian model system for alternative splicing, CD45, and genome-wide. We further show that CTCF binding to CD45 exon 5 is inhibited by DNA methylation, leading to reciprocal effects on exon 5 inclusion. These findings provide a mechanistic basis for developmental regulation of splicing outcome through heritable epigenetic marks.

Apigenin, a naturally occurring plant flavone, abundantly present in common fruits and vegetables is recognized as a bioactive flavonoid shown to possess anti-inflammatory, antioxidant and anticancer properties. Epidemiologic studies suggest that a diet rich in flavones is related to a decreased risk of certain cancers, particularly cancers of the breast, digestive tract, skin, prostate and certain hematological malignancies. It has been suggested that apigenin may be protective in other diseases that are affected by oxidative process such as cardiovascular and neurological disorders, although more research needs to be conducted in this regard. Human clinical trials examining the effect of supplementation of apigenin on disease prevention have not been conducted although there is considerable potential for apigenin to be developed as a cancer chemopreventive agent.

Abstract. Cancer is one of the major public health burdens in the United States and in other developed countries, causing approximately 7 million deaths every year worldwide. Cancer rates vary dramatically in different regions and populations around the globe, especially between developing and developed nations. Changes in cancer prevalence patterns occur within regions as their populations age or become progressively urbanized. Migration has also contributed to such variations as changes in dietary habits influence cancer rates. These epidemiologic findings strongly suggest that cancer rates are influenced by environmental factors including diet, which is largely preventable. Approaches to prevent cancer include overlapping strategies viz. chemoprevention or dietary cancer prevention. Chemoprevention aims at prevention or reversal of the initiation phase of carcinogenesis or arrest at progression of carcinogenesis through the administration of naturally occurring constituents or pharmacological agents. Cancer prevention through diet may be largely achievable by increased consumption of fruits and vegetables. Considerable attention has been devoted to identifying plant-derived dietary agents which could be developed as promising chemopreventives. One such agent is apigenin. A naturally occurring plant flavone (4', 5, 7,-trihydroxyflavone) abundantly present in common fruits and vegetables including parsley, onions, oranges, tea, chamomile, wheat sprouts and some seasonings. Apigenin has been shown to possess remarkable anti-inflammatory, antioxidant and anti-carcinogenic properties. In the last few years, significant progress has been made in studying the biological effects of apigenin at cellular and molecular levels. This review examines the cancer chemopreventive effects of apigenin in an organ-specificity format, evaluating its limitations and its considerable potential for development as a cancer chemopreventive agent.

Activated phosphoinositide 3-kinase (PI3K) and its downstream target Akt/PKB are important signaling molecules and key survival factors involved in the control of cell proliferation, apoptosis and oncogenesis. We investigated the role of the PI3K-Akt signaling pathway in the invasion of prostate cancer cell lines and activation of this pathway in primary human prostate tumors. Treatment of human prostate cancer cells viz. LNCaP, PC-3 and DU145 with PI3K pharmacological inhibitor, LY294002, potentially suppressed the invasive properties in each of these cell lines. Restoration of the PTEN gene to highly invasive prostate cancer PC-3 cells or expression of a dominant negative version of the PI3K target, Akt also significantly inhibited invasion and downregulated protein expression of urokinase-type plasminogen activator (uPA) and matrix metalloproteinase (MMP)-9, markers for cell invasion, indicating a central role of the PI3K-Akt pathway in this process. Immunoblot analysis of PI3K and total/activated levels of Akt showed increased protein levels of catalytic (p110a/b) and regulatory (p85) subunits of PI3K and constitutive Akt activation in high-grade tumors compared to low-grade tumor and benign tissue. Immunohistochemical analyses further confirmed a progressive increase in p-Akt (p-Ser473) levels but not of total-Akt (Akt1/ 2) in cancer tissues compared to benign specimens. A successive increase in p-Akt expression was further noted in specimens serially obtained from individuals with time-course disease progression. Taken together, these results suggest that aberrant activation of PI3K-Akt pathway may contribute to increased cell invasiveness and facilitate prostate cancer progression. ' 2007 Wiley-Liss, Inc.