No abstract

Expression of the p16Ink4a tumor suppressor gene, a sensor of oncogenic stress, is up-regulated by a variety of potentially oncogenic stimuli in cultured primary cells. However, because p16Ink4a expression is also induced by tissue culture stress, physiological mechanisms regulating p16Ink4a expression remain unclear. To eliminate any potential problems arising from tissue culture–imposed stress, we used bioluminescence imaging for noninvasive and real-time analysis of p16Ink4a expression under various physiological conditions in living mice. In this study, we show that oncogenic insults such as ras activation provoke epigenetic derepression of p16Ink4a expression through reduction of DNMT1 (DNA methyl transferase 1) levels as a DNA damage response in vivo. This pathway is accelerated in the absence of p53, indicating that p53 normally holds the p16Ink4a response in check. These results unveil a backup tumor suppressor role for p16Ink4a in the event of p53 inactivation, expanding our understanding of how p16Ink4a expression is regulated in vivo.

The assembly of tight junctions (TJs) and adherens junctions (AJs) is regulated by the transport of integral TJ and AJ proteins to and/or from the plasma membrane (PM) and it is tightly coordinated in epithelial cells. We previously reported that Rab13 and a junctional Rab13-binding protein (JRAB)/molecule interacting with CasL-like 2 (MICAL-L2) mediated the endocytic recycling of an integral TJ protein occludin and the formation of functional TJs. Here, we investigated the role of Rab13 and JRAB/MICAL-L2 in the transport of other integral TJ and AJ proteins claudin-1 and E-cadherin to the PM by using a Ca2+-switch model. Although knockdown of Rab13 specifically suppressed claudin-1 and occludin but not E-cadherin transport, knockdown of JRAB/MICAL-L2 and expression of its Rab13-binding domain (JRAB/MICAL-L2-C) inhibited claudin-1, occludin, and E-cadherin transport. We then identified Rab8 as another JRAB/MICAL-L2-C-binding protein. Knockdown of Rab8 inhibited the Rab13-independent transport of E-cadherin to the PM. Rab8 and Rab13 competed with each other for the binding to JRAB/MICAL-L2 and functionally associated with JRAB/MICAL-L2 at the perinuclear recycling/storage compartments and PM, respectively. These results suggest that the interaction of JRAB/MICAL-L2 with Rab8 and Rab13 coordinates the assembly of AJs and TJs.

EI and MI images are reliable and useful for quantifying erythema and pigmentation, if obtained under constant and consistent conditions. Apart from financial benefits, this method has many advantages and greater clinical utility in comparison with reflectance instruments.

The rates of distant metastases and tumor death in sebaceous carcinoma (SC) have been reported to be higher than those of other cutaneous carcinomas, such as squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), regardless of whether they occur in ocular or extraocular regions. Therefore, strict differentiation of SC from SCC and BCC is required. In this article, we report immunohistochemical findings of SC and compare these data to those of SCC, BCC, and sebaceoma. An immunohistochemical study was performed using 7 antibodies [anti-carcinoembryonic antigen (CEA), anti-epithelial membrane antigen (EMA), anti-CA15-3, anti-CA19-9, anti-androgen receptor (AR), anti-epithelial antigen (Ber-EP4), and anti-adipophilin (ADP)] on 35 cases of SC (16 cases in ocular and 19 cases in extraocular regions) and 10 cases of each SCC (5 cases in ocular and 5 cases in extraocular regions), BCC (5 cases in ocular and 5 cases in extraocular regions), and sebaceoma (no cases arose on the eyelids). In summary, the typical immunophenotypes of SC were EMA+, CA15-3+, AR+, Ber-EP4-, and ADP+; those of sebaceoma were CEA-, EMA+, Ber-EP4-, and ADP+; those of SCC were CEA-, EMA+, CA19-9-, AR-, Ber-EP4-, and ADP-; and those of BCC were CEA-, EMA-, CA15-3-, Ber-EP4+, and ADP-. Other antibody tests for each neoplasm were positive in about half of the cases. The detection of AR and ADP was useful for differentiating SC from SCC, whereas the determination of EMA, CA15-3, Ber-EP4, and ADP was valuable in differentiating SC from BCC.

The class III histone deacetylase (HDAC), SIRT1, is a mammalian homologue of the Saccharomyces cerevisiae chromatin-silencing factor Sir2 that regulates longevity. SIRT1 regulates cell survival via deacetylation of p53 and forkhead transcription factors, and overexpression of SIRT1 is reported to be essential for cell growth and survival in some kinds of cancer. To elucidate the role of SIRT1 in human skin carcinogenesis, we have examined SIRT1 protein expression in 20 cases each of squamous cell carcinoma (SCC), basal cell carcinoma (BCC), Bowen's disease (BD), and actinic keratosis (AK) by immunohistochemical analysis. Overexpression of SIRT1 is frequently observed in all kinds of non-melanoma skin cancers included in this study. In particular, strong expression was observed in all cases of BD. In addition, no obvious difference between AK and SCC was observed in the expression of SIRT1, suggesting that overexpression of SIRT1 may have some relevance to the early stage of skin carcinogenesis. We suppose that SIRT1 could be one of the critical targets for future therapy with the aim of inhibiting cell proliferation and promoting apoptosis in non-melanoma skin cancers.

SummarySekiguchi lesion (sl)-mutant rice infected with Magnaporthe grisea showed increased light-dependent tryptophan decarboxylase (TDC) and monoamine oxidase (MAO) activities. TDC and MAO activities were observed before the penetration of M. grisea to rice cells and maintained high levels even after Sekiguchi lesion formation. Light-dependent expression of TDC gene was observed in leaves inoculated with M. grisea before Sekiguchi lesion formation. Spore germination¯uid (SGF) of M. grisea also induced Sekiguchi lesion formation accompanied by increased enzymes activities and tryptamine accumulation. Sekiguchi lesion was also induced by treatments with tryptamine and b-phenylethylamine, which are substrates for MAO, but was not induced by non-substrates such as indole-3-propionic acid, (AE)-phenylethylamine and tryptophan under light. Light-dependent induction of Sekiguchi lesion by tryptamine was signi®cantly inhibited in the presence of MAO inhibitors, metalaxyl and semicarbazide, and H 2 O 2 -scavengers, ascorbic acid and catalase. H 2 O 2 in M. grisea-infected leaves with and without Sekiguchi lesions was demonstrated directly in situ by strong 3,3 H -diaminobenzidine (DAB) staining. On the other hand, H 2 O 2 induced Sekiguchi lesions on leaves of cv. Sekiguchi-asahi under light, but not in darkness. This difference was associated with the decrease of catalase activity in infected leaves under light and the absence of decrease in darkness. We hypothesize that the H 2 O 2 -induced breakdown of cellular organelles such as chloroplasts and mitochondria in mesophyll cells may cause high TDC and MAO activities and the development of Sekiguchi lesion, and that the sl gene products in wild-type rice may function as a suppressor of organelle breakdown caused by chemical or environmental stress.

Although the role of p21 Waf1/Cip1 gene expression is well documented in various cell culture studies, its in vivo roles are poorly understood. To gain further insight into the role of p21 Waf1/Cip1 gene expression in vivo, we attempted to visualize the dynamics of p21 Waf1/Cip1 gene expression in living animals. In this study, we established a transgenic mice line (p21-p-luc) expressing the firefly luciferase under the control of the p21 Waf1/Cip1 gene promoter. In conjunction with a noninvasive bioluminescent imaging technique, p21-p-luc mice enabled us to monitor the endogenous p21 Waf1/Cip1 gene expression in vivo. By monitoring and quantifying the p21 Waf1/Cip1 gene expression repeatedly in the same mouse throughout its entire lifespan, we were able to unveil the dynamics of p21 Waf1/Cip1 gene expression in the aging process. We also applied this system to chemically induced skin carcinogenesis and found that the levels of p21 Waf1/Cip1 gene expression rise dramatically in benign skin papillomas, suggesting that p21 Waf1/Cip1 plays a preventative role(s) in skin tumor formation. Surprisingly, moreover, we found that the level of p21 Waf1/Cip1 expression strikingly increased in the hair bulb and oscillated with a 3-week period correlating with hair follicle cycle progression. Notably, this was accompanied by the expression of p63 but not p53. This approach, together with the analysis of p21 Waf1/Cip1 knockout mice, has uncovered a novel role for the p21 Waf1/Cip1 gene in hair development. These data illustrate the unique utility of bioluminescence imaging in advancing our understanding of the timing and, hence, likely roles of specific gene expression in higher eukaryotes.aging ͉ cell cycle ͉ hair cycle ͉ imaging