The American Journal of Gastroenterology is published by Nature Publishing Group (NPG) on behalf of the American College of Gastroenterology (ACG). Ranked the #1 clinical journal covering gastroenterology and hepatology*, The American Journal of Gastroenterology (AJG) provides practical and professional support for clinicians dealing with the gastroenterological disorders seen most often in patients. Published with practicing clinicians in mind, the journal aims to be easily accessible, organizing its content by topic, both online and in print. www.amjgastro.com, *2007 Journal Citation Report (Thomson Reuters, 2008)

Human cyclin D1 is expressed as two isoforms derived by alternate RNA splicing, termed D1a and D1b, which differ for the inclusion of intron 4 in the D1b mRNA. Both isoforms are frequently upregulated in human cancers, but cyclin D1b displays relatively higher oncogenic potential. The splicing factors that regulate alternative splicing of cyclin D1b remain unknown despite the likelihood that they contribute to cyclin D1 oncogenicity. In this study, we report that Sam68, an RNA-binding protein frequently overexpressed in prostate cancer cells, enhances splicing of cyclin D1b and supports its expression in prostate cancer cells. Chromatin immunoprecipitation and RNA coimmunoprecipitation experiments showed that Sam68 is recruited to the human CCND1 gene encoding cyclin D1 and that it binds to cyclin D1 mRNA. Transient overexpression and RNAi knockdown experiments indicated that Sam68 acts to enhance endogenous expression of cyclin D1b. Minigene reporter assays showed that Sam68 directly affected alternative splicing of CCND1 message, with a preference for the A870 allele that is known to favor cyclin D1b splicing. Sam68 interacted with the proximal region of intron 4, and its binding correlated inversely with recruitment of the spliceosomal component U1-70K. Sam68-mediated splicing was modulated by signal transduction pathways that elicit phosphorylation of Sam68 and regulate its affinity for CCND1 intron 4. Notably, Sam68 expression positively correlates with levels of cyclin D1b, but not D1a, in human prostate carcinomas. Our results identify Sam68 as the first splicing factor to affect CCND1 alternative splicing in prostate cancer cells, and suggest that increased levels of Sam68 may stimulate cyclin D1b expression in human prostate cancers. Cancer Res; 70(1); 229–39

The American Journal of Gastroenterology is published by Nature Publishing Group (NPG) on behalf of the American College of Gastroenterology (ACG). Ranked the #1 clinical journal covering gastroenterology and hepatology*, The American Journal of Gastroenterology (AJG) provides practical and professional support for clinicians dealing with the gastroenterological disorders seen most often in patients. Published with practicing clinicians in mind, the journal aims to be easily accessible, organizing its content by topic, both online and in print. www.amjgastro.com, *2007 Journal Citation Report (Thomson Reuters, 2008)

Coexpression for c‐Kit receptor and its ligand stem cell factor (SCF) has been described in neuroblastoma (NB) cell lines and tumors, suggesting the existence of an autocrine loop modulating tumor growth. We evaluated c‐Kit and SCF expression by immunohistochemistry in a series of 75 primary newly diagnosed neuroblastic tumors. Immunostaining for c‐Kit was found in 10/75 and for SCF in 17/75, with 5/10 c‐Kit–positive tumors also expressing SCF. For both, c‐Kit and SCF staining were predominantly found in the most aggressive subset of tumors, i.e., those amplified for MYCN: c‐Kit was detected in 8/14 amplified vs. 2/61 single copy (p<0.001), and SCF in 9/14 amplified vs. 8/61 single copy tumors (p<0.001). Furthermore, the association of c‐Kit expression with advanced stage (3 or 4) (p=0.001) and of SCF expression with adrenal primary (p=0.03) was substantiated. The in vitro activity of the tyrosine kinase inhibitor STI‐571 (imatinib mesylate, Gleevec, Glivec) on NB cell lines positive or negative for c‐Kit was also assessed. When cells were grown in 10% fetal calf serum, the 4 c‐Kit‐positive cell lines tested were sensitive to STI‐571 growth inhibition to a different extent (ranging from 30 to 80%); also the c‐Kit‐negative cell line GI‐CA‐N was slightly affected, suggesting that other STI‐571 targets operate in regulating NB proliferation. In addition, c‐Kit‐positive cell lines SK‐N‐BE2(c) and HTLA230, grown in SCF only, remained sensitive (40 and 70% of growth inhibition, respectively), while, in the same conditions, proliferation of the c‐Kit‐negative cell line GI‐CA‐N was not affected. Immunoprecipitation of c‐Kit from cell lysates of SK‐N‐BE2(c) and HTLA230 cells grown in SCF and subsequent western blot analysis of the immunoprecipitates revealed a sharp decrease of c‐Kit phosphorylation after STI‐571 treatment. These data demonstrate that both c‐Kit and SCF are preferentially expressed in vivo in the most aggressive neuroblastic tumors and that their signaling is active in promoting in vitro NB cell proliferation that can be selectively inhibited by treatment with STI‐571.

Noninvasive biomarkers of high- and low-grade intestinal inflammation and of mucosal healing (MH) in patients with inflammatory bowel disease are currently lacking. We have recently shown that fecal high mobility group box 1 (HMGB1) protein is a novel biomarker of gut inflammation. We aimed at investigating in a mouse model if HMGB1 was able to foresee both a clinically evident and a subclinical gut inflammation and if its normalization indicated MH. We also aimed at confirming the results in patients with Crohn's disease (CD) and ulcerative colitis. C57BL6/J mice were treated with increasing doses of dextran sodium sulphate to induce colitis of different severity degrees; 28 with CD, 23 with ulcerative colitis, and 17 controls were also enrolled. Fecal HMGB1 was analyzed by enzyme-linked immunosorbent assay and immunoblotting. Fecal HMGB1 increased by 5-, 11-, 18-, and 24-folds with dextran sodium sulphate doses of 0.25%, 0.50%, 1%, and 4%, respectively, showing that the protein detected a high-grade and a subclinical inflammation. After a recovery time of 4-week posttreatment, HMGB1 returned to control levels, paralleling MH. In patients, fecal HMGB1 significantly correlated with endoscopic indexes (Simple Endoscopic Score for Crohn's Disease [SES-CD], endoscopic Mayo subscore), but not with the disease activity indexes (Crohn's disease Activity Index, partial Mayo score). Fecal HMGB1 is a robust noninvasive biomarker of clinically overt and subclinical gut inflammation; it can also be a surrogate marker of MH. We suggest the use of fecal HMGB1 to monitor the disease course and assess therapy outcomes in inflammatory bowel disease.