Background Colorectal cancer (CRC) incidence is increasing in adults younger than 50 years. This study evaluated clinical and molecular features to identify those features unique to early‐onset CRC that differentiate these patients from patients 50 years old or older. Methods Baseline characteristics were evaluated according to the CRC onset age with 3 independent cohorts. A fourth cohort was used to describe the impact of age on the consensus molecular subtype (CMS) prevalence. Results This retrospective review of more than 36,000 patients with CRC showed that early‐onset patients were more likely to have microsatellite instability (P = .038), synchronous metastatic disease (P = .009), primary tumors in the distal colon or rectum (P < .0001), and fewer BRAF V600 mutations (P < .001) in comparison with patients 50 years old or older. Patients aged 18 to 29 years had fewer adenomatous polyposis coli (APC) mutations (odds ratio [OR], 0.56; 95% confidence interval [CI], 0.35‐0.90; P = .015) and an increased prevalence of signet ring histology (OR, 4.89; 95% CI, 3.23‐7.39; P < .0001) in comparison with other patients younger than 50 years. In patients younger than 40 years, CMS1 was the most common subtype, whereas CMS3 and CMS4 were uncommon (P = .003). CMS2 was relatively stable across age groups. Early‐onset patients with inflammatory bowel disease were more likely to have mucinous or signet ring histology (OR, 5.54; 95% CI, 2.24‐13.74; P = .0004) and less likely to have APC mutations (OR, 0.24; 95% CI, 0.07‐0.75; P = .019) in comparison with early‐onset patients without predisposing conditions. Conclusions Early‐onset CRC is not only distinct from traditional CRC: special consideration should be given to and further investigations should be performed for both very young patients with CRC (18‐29 years) and those with predisposing conditions. The etiology of the high rate of CMS1 in patients younger than 40 years deserves further exploration.

Colorectal cancers are classified as right/left-sided based on whether they occur before/after the splenic flexure, with established differences in molecular subtypes and outcomes. However, it is unclear if this division is optimal and whether precise tumor location provides further information. In 1,876 patients with colorectal cancer, we compared mutation prevalence and overall survival (OS) according to side and location. Consensus molecular subtype (CMS) was compared in a separate cohort of 608 patients. Mutation prevalence differed by side and location for , and Within left- and right-sided tumors, there remained substantial variations in mutation rates. For example, within right-sided tumors, mutations decreased from 70% for cecal, to 43% for hepatic flexure location ( = 0.0001), while V600 mutations increased from 10% to 22% between the same locations ( < 0.0001). Within left-sided tumors, the sigmoid and rectal region had more mutations ( = 0.027), less ( = 0.0009), ( = 0.0033), or mutations ( < 0.0001), and less MSI ( < 0.0001) than other left-sided locations. Despite this, a left/right division preceding the transverse colon maximized prognostic differences by side and transverse colon tumors had K-modes mutation clustering that appeared more left than right sided. CMS profiles showed a decline in CMS1 and CMS3 and rise in CMS2 prevalence moving distally. Current right/left classifications may not fully recapitulate regional variations in tumor biology. Specifically, the sigmoid-rectal region appears unique and the transverse colon is distinct from other right-sided locations. .

Tissue transglutaminase (tTG) is a multifunctional enzyme with transglutaminase crosslinking (TGase), GTP binding, and hydrolysis activities that play a role in many different disorders. We identified, characterized, and investigated the function and stability of two alternatively spliced forms of tTG using biochemical, cellular, and molecular biological approaches. Using a human aortic vascular smooth muscle cells (VSMC) cDNA library, we identified two cDNAs encoding C-terminal truncated forms, tTG V1 and tTG V2 . tTG V1,2 mRNAs were synthesized by a rare splicing event using alternate splice sites within exons 12 and 13 of the tTG gene, respectively. Quantitative PCR and immunoblotting demonstrated that there was unique expression and localization of tTG V1,2 compared with tTG in human umbilical vein endothelial cells (HUVECs), VSMC, and leukocytes. The loss of C-terminal 52 amino acid residues (AAs) in tTG V1,2 altered GTP binding, enhanced GTP hydrolysis, rendered the variants insensitive to GTP inhibition, and resulted in <10% residual Ca +2 -dependent TGase activity. Transfection in HEK293 demonstrated a 28-and 5-fold reduction in the expression of tTG V1 and tTG V2 , respectively, demonstrating that the C-terminal GTP-binding domain is important in stabilizing and promoting the half-life of tTG. The altered affinity for GTP allowed tTG V1,2 to exhibit enhanced TGase activity when there is a transient increase in Ca +2 levels. The abundance of tTG V1,2 and its distinct intracellular expression patterns in human vascular cells and leukocytes indicate these isoforms likely have unique physiological functions.-Lai, T. S., Liu, Y., Li, W., Greenberg, C. S. Identification of two GTP-independent alternatively spliced forms of tissue transglutaminase in human leukocytes, vascular smooth muscle and endothelial cells.Keywords neurodegenerative disease; aging; cell differentiation; extracellular matrix; vascular disease TISSUE TRANSGLUTAMINASE (tTG) is a unique member of the transglutaminase gene family (TG, E.C. 2.3.2.13, protein-glutamine γ-glutamyltransferase) because it exhibits multiple enzymatic properties. Established first as a Ca +2 -dependent transglutaminase enzyme (TGase) catalyzing an isopeptide bond between a specific γ-glutamyl (Q) containing peptide substrate and an ε-amine group from a peptide-bound lysine (K) residue or a free primary amine (1), it was later found to have G protein signaling and kinase activities (2-5). Moreover, tTG has a wide variety of functions independent of its enzymatic activities (6). tTG is known to function as a cellsurface adhesion molecule, to bind nitric oxide (NO), to serve as a coreceptor for integrins and the G-protein coupled receptors (GPCRs), and to be involved in signaling functions (6)(7)(8)(9)(10)(11). tTG also has roles in promoting cell death and survival and inflammation and has been NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript identified as the therapeutic target in neurodegenerative, fibrotic, autoimmune, and cardiova...

Serotonin-1B (5-HT1B) autoreceptors are located in serotonin (5-HT) terminals along with serotonin transporters (SERT), and play a critical role in autoregulation of serotonergic neurotransmission, and are implicated in disorders of serotonergic function, particularly emotional regulation. SERT modulates serotonergic neurotransmission by high-affinity reuptake of 5-HT. Alterations in SERT activity are associated with increased risk for depression and anxiety. Several neurotransmitter receptors are known to regulate SERT Km and Vmax, and previous work suggests that 5-HT1B autoreceptors may regulate 5-HT reuptake, in addition to modulating 5-HT release and synthesis. We used rotating disk electrode voltammetry to investigate 5-HT1B autoreceptor regulation of SERT-mediated 5-HT uptake into synaptosomes. The selective 5-HT1B antagonist SB224289 decreased SERT activity in synaptosomes prepared from wild-type but not 5-HT1B knockout mice, whereas SERT uptake was enhanced after pre-treatment with the selective 5-HT1B agonist CP94253. Furthermore, SERT activity varies as a function of 5-HT1B receptor expression—specifically, genetic deletion of 5-HT1B decreased SERT function, while viral-mediated overexpression of 5-HT1B autoreceptors in rat raphe neurons increased SERT activity in rat hippocampal synaptosomes. Considered collectively, these results provide evidence that 5-HT1B autoreceptors regulate SERT activity. Since SERT clearance rate varies as a function of 5-HT1B autoreceptor expression levels and is modulated by both activation and inhibition of 5-HT1B autoreceptors, this dynamic interaction may be an important mechanism of serotonin autoregulation with therapeutic implications.

Human tissue transglutaminase (TGM2) is a calcium-dependent crosslinking enzyme involved in the post-translational modification of intra- and extra-cellular proteins and involved in several neurodegenerative diseases. To find specific inhibitors to TGM2, two structurally diverse chemical libraries (Lopac and Prestwick) were screened. We found that ZM39923, a Janus kinase inhibitor and its metabolite ZM449829 were the most potent inhibitors with IC50 of 10 and 5 nM, respectively. In addition, two other inhibitors including Tyrphostin 47 and Vitamin K3 were found to have an IC50 in the µM range. These agents utilized in part a thiol-dependent mechanism to inhibit TGM2, consistent with the activation of TGM2 by reduction of an intra-molecular disulfide bond. These inhibitors were tested in a polyglutamine-expressing Drosophila model of neurodegeneration and found to improve survival. The TGM2 inhibitors we discovered may serve as valuable lead compounds for the development of orally active TGM2 inhibitors to treat human diseases.