No abstract

Abstract. During conjugation, haploid S. cerevisiae cells find one another by polarizing their growth toward each other along gradients of pheromone (chemotropism). We demonstrate that yeast cells exhibit a second mating behavior: when their receptors are saturated with pheromone, wild-type a cells execute a default pathway and select a mate at random. These matings are less efficient than chemotropic matings, are induced by the same dose of pheromone that induces shmoo formation, and appear to use a site near the incipient bud site for polarization. We show that the SPA2 gene is specifically required for the default pathway: spa2A mutants cannot mate if pheromone concentrations are high and gradients are absent, but can mate if gradients are present, ste2A, sst2A, and farlA mutants are chemotropism-defective and therefore must choose a mate by using a default pathway; consistent with this deduction, these strains require SPA2 to mate. In addition, our results suggest that farl mutants are chemotropism-defective because their mating polarity is fixed at the incipient bud site, suggesting that the FAR1 gene is required for inhibiting the use of the incipient bud site during chemotropic mating. These observations reveal a molecular relationship between the mating and budding polarity pathways.

No abstract

Alpha-methylacyl-CoA racemase (AMACR) catalyzes the racemization of alpha-methyl, branched carboxylic coenzyme A thioesters, and is overexpressed in a variety of neoplasms, such as prostate and colon cancer. The aim of this study was to evaluate AMACR expression in the metaplasia-dysplasia-carcinoma sequence in Barrett's esophagus (BE), ulcerative colitis (UC), and Crohn's disease (CD) and to determine whether its expression can be used to detect dysplastic epithelium in these conditions. One hundred thirty-four routinely processed biopsy and/or resection specimens from 134 patients with BE [M/F ratio: 5.7, mean age: 67 y (36 negative (intestinal metaplasia only), 14 indefinite for dysplasia (IND), 16 low-grade dysplasia (LGD), 32 high-grade dysplasia (HGD), and 36 invasive adenocarcinoma (ACA)] and 74 specimens from 74 patients with inflammatory bowel disease (IBD) [56 with ulcerative colitis, 18 with Crohn's disease, M/F ratio: 1.8, mean age: 55 y (17 negative, 7 IND, 26 LGD, 10 HGD, and 14 ACA)] were immunostained with a monoclonal AMACR antibody (p504S). The degree of cytoplasmic staining in all cases was evaluated in a blinded fashion according to the following grading system: 0, negative (0% cells positive); 1+, 1% to 10% cells positive; 2+, 10% to 50% cells positive; or 3+, >50% cells positive. In patients with BE, AMACR was not expressed in any negative foci (0%) but was significantly increased (P<0.0001) in foci of LGD (38%), HGD (81%), and ACA (72%). Three of 14 (21%) IND foci from 3 BE patients were only focally positive (grade 1: 7%, 2: 14%). However, 1 of these 3 patients had follow-up information available and had developed ACA subsequently. Similarly, in patients with IBD, AMACR was not expressed in any foci considered negative for dysplasia, but was significantly increased (P<0.0001) in foci of LGD (96%), HGD (80%), and ACA (71%). Only 1/7 (14%) IND focus from 1 patient was focally positive (grade 1). The sensitivity for the detection of LGD and HGD in BE and IBD was 38% and 81%, and 96% and 80%, respectively, for the 2 types of disorders. The specificity was 100% for both BE and IBD. AMACR is involved in the neoplastic progression in BE and IBD. The high degree of specificity of AMACR for dysplasia/carcinoma in BE and IBD suggests that it may be useful to detect neoplastic epithelium in these conditions.

The spindle checkpoint prevents chromosome loss by preventing chromosome segregation in cells with improperly attached chromosomes [1, 2 and 3]. The checkpoint senses defects in the attachment of chromosomes to the mitotic spindle [4] and the tension exerted on chromosomes by spindle forces in mitosis [5, 6 and 7]. Because many cancers have defects in chromosome segregation, this checkpoint may be required for survival of tumor cells and may be a target for chemotherapy. We performed a phenotype-based chemical-genetic screen in budding yeast and identified an inhibitor of the spindle checkpoint, called cincreasin. We used a genome-wide collection of yeast gene-deletion strains and traditional genetic and biochemical analysis to show that the target of cincreasin is Mps1, a protein kinase required for checkpoint function [8]. Despite the requirement for Mps1 for sensing both the lack of microtubule attachment and tension at kinetochores, we find concentrations of cincreasin that selectively inhibit the tension-sensitive branch of the spindle checkpoint. At these concentrations, cincreasin causes lethal chromosome missegregation in mutants that display chromosomal instability. Our results demonstrate that Mps1 can be exploited as a target and that inhibiting the tension-sensitive branch of the spindle checkpoint may be a way of selectively killing cancer cells that display chromosomal instability.

Positive circumferential resection margins are prognostically important and the CAP criteria provide a more clinically meaningful assessment. Universal adoption of the CAP system can improve interpretation of international clinical trials and allow more accurate comparisons of outcomes.

Lymphomas with 2 translocations involving c-MYC and BCL2 or BCL6 are a subset of biologically aggressive mature B-cell lymphomas now frequently categorized under the entity of B-cell lymphoma, unclassifiable, with features intermediate between Burkitt lymphoma and diffuse large B-cell lymphoma. We identified a cohort of these lymphomas in our databases and retrospectively reviewed corresponding in-house flow cytometric data to determine whether a common immunophenotype might be present. Herein we report on our findings on 10 lymphomas, each with translocations involving c-MYC and BCL2 or BCL6 and show that these cases frequently showed a common immunophenotype that includes decreased expression of CD20. Because these lymphomas often show aggressive biologic behavior and poor clinical outcome, recognition of this relatively common immunophenotype may be useful for identifying cases for confirmatory cytogenetic studies, as often, flow cytometry provides the first assessment of these clinical specimens.

No abstract