Minsub Shim

Prostate derived factor in human prostate cancer cells: Gene induction by vitamin D via a p53‐dependent mechanism and inhibition of prostate cancer cell growth

The secosteroid hormone 1α, 25‐dihydroxyvitamin D3 (1,25D) has been shown to regulate the growth and differentiation of human prostate cancer (PCa) cells, although the precise molecular mechanisms mediating these effects have not been defined. Previous studies in our laboratory demonstrated that the antiproliferative effects of 1,25D on PCa cells are mediated through the nuclear vitamin D receptor (VDR). In the present study, we performed gene profiling of LNCaP human PCa cells following 1,25D treatment and identified the antitumorigenic gene, prostate derived factor (PDF), as being highly induced by 1,25D. PDF is a member of the TGF‐β superfamily and has been implicated in a variety of functions directly related to tumorigenicity including antiproliferative and pro‐apoptotic effects. Gene expression studies using 1,25D analogs and a VDR antagonist demonstrate that 1,25D‐mediated induction of PDF message and protein in PCa cells is dependent on VDR action. PDF is a transcriptional target of the tumor suppressor, p53. Here we show that the expression of PDF in nine PCa cell lines is dependent on functional p53. Additionally, transfection of p53‐null ALVA‐31 PCa cells with a p53 expression plasmid, and expression of dominant negative p53 in LNCaP PCa cells, show that the ability of VDR to induce PDF requires functional p53. Importantly, forced PDF expression in PC‐3 cells results in decreased cell proliferation, soft agar cloning, and xenograft tumor size. These data demonstrate that PDF exerts antitumorigenic properties on PCa cells and its regulation by 1,25D may provide insights into the action of 1,25D in PCa. J. Cell. Physiol. 208: 566–574, 2006.

Vitamin E succinate induces NAG-1 expression in a p38 kinase-dependent mechanism

NAG-1 (nonsteroidal anti-inflammatory drug-activated gene), a member of the transforming growth factor-β superfamily, is involved in many cellular processes, such as inflammation, apoptosis/survival, and tumorigenesis. Vitamin E succinate (VES) is the succinate derivative of α-tocopherol and has antitumorigenic activity in a variety of cell culture and animal models. In the current study, the regulation and role of NAG-1 expression in PC-3 human prostate carcinoma cells by VES was examined. VES treatment induced growth arrest and apoptosis as well as an increase in NAG-1 protein and mRNA levels in a time- and concentration-dependent manner. VES treatment induced nuclear translocation and activation of p38 kinase. Pretreatment with p38 kinase inhibitor blocked the VES-induced increase in NAG-1 protein and mRNA levels, whereas an inhibition of protein kinase C, Akt, c-Jun NH2-terminal kinase, or MEK activity had no effect on VES-induced NAG-1 levels. Forced expression of constitutively active MKK6, an upstream kinase for p38, induced an increase in NAG-1 promoter activity, whereas p38 kinase inhibitor blocked MKK6-induced increase in NAG-1 promoter activity. VES treatment resulted in >3-fold increase in the half-life of NAG-1 mRNA in a p38 kinase-dependent manner and transient transfection experiment showed that VES stabilizes NAG-1 mRNA through AU-rich elements in 3′-untranslated region of NAG-1 mRNA. The inhibition of NAG-1 expression by small interfering RNA significantly blocked VES-induced poly(ADP-ribose) polymerase cleavage, suggesting that NAG-1 may play an important role in VES-induced apoptosis. These results indicate that VES-induced expression of NAG-1 mRNA/protein is regulated by transcriptional/post-transcriptional mechanism in a p38 kinase-dependent manner and NAG-1 can be chemopreventive/therapeutic target in prostate cancer. [Mol Cancer Ther 2008;7(4):961–71]

The H6D variant of NAG-1/GDF15 inhibits prostate xenograft growth in vivo

Non‐steroidal anti‐inflammatory drug‐activated gene (NAG‐1), a divergent member of the transforming growth factor‐beta superfamily, has been implicated in many cellular processes, including inflammation, early bone formation, apoptosis, and tumorigenesis. Recent clinical studies suggests that a C to G single nucleotide polymorphism at position 6 (histidine to aspartic acid substitution, or H6D) of the NAG‐1 protein is associated with lower human prostate cancer incidence. The objective of the current study is to investigate the activity of NAG‐1 H6D variant in prostate cancer tumorigenesis in vivo.

Embryonic expression of cyclooxygenase-2 causes malformations in axial skeleton

Cyclooxygenases (COXs) have important functions in various physiological and pathological processes. COX-2 expression is highly induced by a variety of stimuli and is observed during certain periods of embryonic development. In this report, the direct effect of COX-2 expression on embryonic development is examined in a novel COX-2 transgenic mouse model that ubiquitously expresses human COX-2 from the early stages of embryonic development. COX-2 transgenic fetuses exhibit severe skeletal malformations and die shortly after birth. Skeletal malformations are localized along the entire vertebral column and rib cage and are linked to defective formation of cartilage anlagen. The cartilage anlagen of axial skeleton fail to properly develop in transgenic embryos because of impaired precartilaginous sclerotomal condensation, which results from the reduction of cell number in the sclerotome. Despite the ubiquitous expression of COX-2, the number of apoptotic cells is highly increased in the sclerotome of transgenic embryos but not in other tissues, suggesting that it is a tissue-specific response. Therefore, the loss of sclerotomal cells due to an increased apoptosis is probably responsible for axial skeletal malformations in transgenic fetuses. In addition, the sclerotomal accumulation of p53 protein is observed in transgenic embryos, suggesting that COX-2 may induce apoptosis via the up-regulation of p53. Our results demonstrate that the aberrant COX-2 signaling during embryonic development is teratogenic and suggest a possible association of COX-2 with fetal malformations of unknown etiology.

Microscopic Computed Tomography–Based Virtual Histology for Visualization and Morphometry of Atherosclerosis in Diabetic Apolipoprotein E Mutant Mice

Atherosclerosis is a progressive disease characterized by the accumulation of lipids and fibrous elements in the arteries and is a leading cause of heart disease and stroke in developed and developing countries.1 Animal models have become increasingly important tools for addressing key mechanistic and therapeutic questions that cannot be answered from human studies of atherosclerosis. However, the small-scale vascular structures in genetically engineered mice require labor-intensive histomorphometric techniques to quantify lesions. Recently, a new technique has emerged to image ex vivo blocks of soft tissue by staining tissue with metal solutions, then scanning with a microscopic computed tomography (microCT) instrument (Figure I in the online-only Data Supplement).2 This technique was originally applied to the study of the developing heart in embryos3 and fetuses (Figure II in the online-only Data Supplement) but can also be applied to the en bloc imaging of the heart, great vessels, and lesions thereof. By this method, tissues are left intact, but one can employ image analysis to create “virtual” histological …