Loss of Rab25 promotes the development of intestinal neoplasia in mice and is associated with human colorectal adenocarcinomas.

Transformation of epithelial cells is associated with loss of cell polarity, which includes alterations in cell morphology as well as changes in the complement of plasma membrane proteins. Rab proteins regulate polarized trafficking to the cell membrane and therefore represent potential regulators of this neoplastic transition. Here we have demonstrated a tumor suppressor function for Rab25 in intestinal neoplasia in both mice and humans. Human colorectal adenocarcinomas exhibited reductions in Rab25 expression independent of stage, with lower Rab25 expression levels correlating with substantially shorter patient survival. In wild-type mice, Rab25 was strongly expressed in cells luminal to the proliferating cells of intestinal crypts. While Rab25-deficient mice did not exhibit gross pathology, ApcMin/+ mice crossed onto a Rab25-deficient background showed a 4-fold increase in intestinal polyps and a 2-fold increase in colonic tumors compared with parental ApcMin/+ mice. Rab25-deficient mice had decreased beta1 integrin staining in the lateral membranes of villus cells, and this pattern was accentuated in Rab25-deficient mice crossed onto the ApcMin/+ background. Additionally, Smad3+/- mice crossed onto a Rab25-deficient background demonstrated a marked increase in colonic tumor formation. Taken together, these results suggest that Rab25 may function as a tumor suppressor in intestinal epithelial cells through regulation of protein trafficking to the cell surface.

N2 disease in patients with head and neck squamous cell cancer treated with chemoradiotherapy: is there a role for posttreatment neck dissection?

OBJECTIVES: To determine whether nodal necrosis and node size of 3 cm or larger are risk factors for recurrent neck disease and whether negative computed tomography-positron emission tomography (CT-PET) results 8 weeks or more after therapy indicate complete response in the neck in patients with N2 disease. DESIGN: Retrospective study. SETTING: State university hospital. PATIENTS: Fifty-six patients with head and neck squamous cell cancer and N2 disease treated with chemoradiotherapy were evaluated for persistent or recurrent neck disease. Tumor characteristics analyzed were primary site, T category, nodal size (<3 cm or > or =3 cm), nodal necrosis based on hypodensity of one-third or more of the node, and type of N2 disease (N2a, N2b, or N2c). Forty-eight of the 56 patients underwent CT-PET to determine treatment response after chemoradiotherapy. Clinical examination, imaging, and pathologic specimens were used to confirm disease recurrence. MAIN OUTCOME MEASURES: The number of recurrence events, disease-free interval, and positive posttreatment CT-PET result in the neck. RESULTS: Most patients had oropharyngeal tumors (n = 37; 66%), T2 tumors (n = 21; 38%), nodes 3 cm or larger (n = 43; 77%), positive necrosis (n = 40; 71%), and N2c disease (n = 28; 50%). Multivariate analysis determined that no factors were significant predictors of recurrence, except for positive posttreatment PET results (P < .001). Comparison of CT-PET with nodal recurrence demonstrated a sensitivity of 82%, a specificity of 97%, a negative predictive value of 95%, and a positive predictive value of 90%. CONCLUSION: Posttreatment neck dissections may not be indicated for patients with N2 disease and a negative CT-PET result, even in patients with nodal necrosis and nodes 3 cm or larger.

CB1 cannabinoid receptor activity is modulated by the cannabinoid receptor interacting protein CRIP 1a.

The CB1 cannabinoid receptor is a G-protein coupled receptor that has important physiological roles in synaptic plasticity, analgesia, appetite, and neuroprotection. We report the discovery of two structurally related CB1 cannabinoid receptor interacting proteins (CRIP1a and CRIP1b) that bind to the distal C-terminal tail of CB1. CRIP1a and CRIP1b are generated by alternative splicing of a gene located on chromosome 2 in humans, and orthologs of CRIP1a occur throughout the vertebrates, whereas CRIP1b seems to be unique to primates. CRIP1a coimmunoprecipitates with CB1 receptors derived from rat brain homogenates, indicating that CRIP1a and CB1 interact in vivo. Furthermore, in superior cervical ganglion neurons coinjected with CB1 and CRIP1a or CRIP1b cDNA, CRIP1a, but not CRIP1b, suppresses CB1-mediated tonic inhibition of voltage-gated Ca2+ channels. Discovery of CRIP1a provides the basis for a new avenue of research on mechanisms of CB1 regulation in the nervous system and may lead to development of novel drugs to treat disorders where modulation of CB1 activity has therapeutic potential (e.g., chronic pain, obesity, and epilepsy).