Regulated Expression of Chromobox Homolog 5 Revealed in Tumors of ApcMin/+ ROSA11 Gene Trap Mice

The gene-trap lacZ reporter insertion, ROSA11, in the Cbx5 mouse gene illuminates the regulatory complexity of this locus in ApcMin/+ mice. The insertion site of the β-Geo gene-trap element lies in the 24-kb intron proximal to the coding region of Cbx5. Transcript analysis indicates that two promoters for Cbx5 flank this insertion site. Heterozygotes for the insertion express lacZ widely in fetal tissues but show limited expression in adult tissues. In the intestine, strong expression is limited to proliferative zones of crypts and tumors. Homozygotes for ROSA11, found at a lower than Mendelian frequency, express reduced levels of the coding region transcript in normal tissues, using a downstream promoter. Analysis via real-time polymerase chain reaction indicates that the upstream promoter is the dominant promoter in normal epithelium and tumors. Bioinformatic analysis of the Cbx5 locus indicates that WNT and its target transcription factor MYC can establish a feedback loop that may play a role in regulating the self-renewal of the normal intestinal epithelium and its tumors

Biometrics DOI: 10.1111/j.1541-0420.2006.00522.x A Statistical Test of the Hypothesis that Polyclonal Intestinal Tumors Arise by Random Collision of Initiated Clones

Summary. The random collision hypothesis is a mathematical idealization of intestinal tumor formation that can account for the polyclonal origin of tumors without requiring a mechanistic description of clonal interaction. Using data from recent polyclonality studies in mice, we develop a statistical procedure to test the random collision hypothesis. Elements from stochastic geometry and approximations due to Armitage (1949, Biometrika 36, 257–266) support a statistical model of tumor count data. Bayesian analysis yields the posterior distribution of the number of heterotypic tumors, from which p-values are computed to test random collision

Caveolae facilitate muscarinic receptor-mediated intracellular Ca2+ mobilization and contraction in airway smooth muscle

Contractile responses of airway smooth muscle ( ASM) determine airway resistance in health and disease. Caveolae microdomains in the plasma membrane are marked by caveolin proteins and are abundant in contractile smooth muscle in association with nanospaces involved in Ca2+ homeostasis. Caveolin-1 can modulate localization and activity of signaling proteins, including trimeric G proteins, via a scaffolding domain. We investigated the role of caveolae in contraction and intracellular Ca2+ ([Ca2+](i)) mobilization of ASM induced by the physiological muscarinic receptor agonist, acetylcholine ( ACh). Human and canine ASM tissues and cells predominantly express caveolin-1. Muscarinic M-3 receptors ( M3R) and G alpha(q)/11 cofractionate with caveolin-1-rich membranes of ASM tissue. Caveolae disruption with beta-cyclodextrin in canine tracheal strips reduced sensitivity but not maximum isometric force induced by ACh. In fura-2-loaded canine and human ASM cells, exposure to methyl-beta-cyclodextrin (m beta CD) reduced sensitivity but not maximum [Ca2+](i) induced by ACh. In contrast, both parameters were reduced for the partial muscarinic agonist, pilocarpine. Fluorescence microscopy revealed that m beta CD disrupted the colocalization of caveolae-1 and M3R, but [N-methyl-H-3] scopolamine receptor-binding assay revealed no effect on muscarinic receptor availability or affinity. To dissect the role of caveolin-1 in ACh-induced [Ca2+](i) flux, we disrupted its binding to signaling proteins using either a cell-permeable caveolin-1 scaffolding domain peptide mimetic or by small interfering RNA knockdown. Similar to the effects of m beta CD, direct targeting of caveolin-1 reduced sensitivity to ACh, but maximum [Ca2+](i) mobilization was unaffected. These results indicate caveolae and caveolin-1 facilitate [Ca2+](i) mobilization leading to ASM contraction induced by submaximal concentrations of ACh

Advanced Intestinal Cancers often Maintain a Multi-Ancestral Architecture.

A widely accepted paradigm in the field of cancer biology is that solid tumors are uni-ancestral being derived from a single founder and its descendants. However, data have been steadily accruing that indicate early tumors in mice and humans can have a multi-ancestral origin in which an initiated primogenitor facilitates the transformation of neighboring co-genitors. We developed a new mouse model that permits the determination of clonal architecture of intestinal tumors in vivo and ex vivo, have validated this model, and then used it to assess the clonal architecture of adenomas, intramucosal carcinomas, and invasive adenocarcinomas of the intestine. The percentage of multi-ancestral tumors did not significantly change as tumors progressed from adenomas with low-grade dysplasia [40/65 (62%)], to adenomas with high-grade dysplasia [21/37 (57%)], to intramucosal carcinomas [10/23 (43%]), to invasive adenocarcinomas [13/19 (68%)], indicating that the clone arising from the primogenitor continues to coexist with clones arising from co-genitors. Moreover, neoplastic cells from distinct clones within a multi-ancestral adenocarcinoma have even been observed to simultaneously invade into the underlying musculature [2/15 (13%)]. Thus, intratumoral heterogeneity arising early in tumor formation persists throughout tumorigenesis