The RON receptor tyrosine kinase (RTK) is overexpressed in the majority of pancreatic cancers, yet its role in pancreatic cancer cell biology remains to be clarified. Recent work in childhood sarcoma identified RON as a mediator of resistance to insulin-like growth factor receptor (IGF1-R)-directed therapy. To better understand RON function in pancreatic cancer cells, we sought to identify novel RON interactants. Using multidimensional protein identification analysis, IGF-1R was identified and confirmed to interact with RON in pancreatic cancer cell lines. IGF-1 induces rapid phosphorylation of RON, but RON signaling did not activate IGF-1R indicating unidirectional signaling between these RTKs. We next demonstrate that IGF-1 induces pancreatic cancer cell migration that is RON dependent, as inhibition of RON signaling by either shRNA-mediated RON knockdown or by a RON kinase inhibitor abrogated IGF-1 induced wound closure in a scratch assay. In pancreatic cancer cells, unlike childhood sarcoma, STAT-3, rather than RPS6, is activated in response to IGF-1, in a RON-dependent manner. The current study defines a novel interaction between RON and IGF-1R and taken together, these two studies demonstrate that RON is an important mediator of IGF1-R signaling and that this finding is consistent in both human epithelial and mesenchymal cancers. These findings demand additional investigation to determine if IGF-1R independent RON activation is associated with resistance to IGF-1R-directed therapies in vivo and to identify suitable biomarkers of activated RON signaling.

No abstract

No abstract

Various animal models of pain are dependent on activation of different glutamate receptor subtypes. First-degree burn of the paw elicits a secondary hyperalgesia that is dependent on Ca 2++ permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), but not N-methyl-D-aspartate (NMDA) receptors. The present study takes advantage of that specificity by examining the effects of spinal pretreatments of agents on this secondary hyperalgesia. Rats with indwelling intrathecal catheters were pretreated with agents prior to paw injury. Mechanical withdrawal thresholds were measured before, and for three h after the injury.Spinal pretreatment with cyclooxygenase (10 and 30 μg (S)-(+)-ibuprofen; and 3 and 30 μg ketorolac) and nitric oxide synthase (33 and 100 μg N G Nitro-L-arginine methyl ester hydrochloride (L-NAME) and 10 μg thiocitrulline) inhibitors resulted in no specific anti-allodynia. In contrast, ziconotide (0.3, 1.0 and 3 μg), the N-type voltage gated calcium channel antagonist was very effective in blocking burn-induced sensitivity at all doses used. L-type (Diltiazam 230 μg) and P-type (Agatoxin IVA 0.3 μg) calcium channel blockers produced intermediate effects. Thus, cyclooxygenase and nitric oxide synthase are assumed not to be downstream of Ca 2++ permeable AMPA receptors. Voltage gated calcium channels blockers could exert their effects either pre-or post-synaptically.

202 Background: GIST treatment with imatinib has served as the prototype for targeted molecular therapy. However, patients frequently acquire drug resistance to imatinib and this has prompted the development of additional multi-kinase inhibitors. To date, preclinical testing of novel agents has predominantly been performed using cell line based subcutaneous xenografts that may overestimate drug activity in the clinic. This suggests that novel in vivo models are needed to improve prediction of clinical efficacy. We hypothesized that human GISTs could be intra-peritoneally xenografted into immunodeficient mice in order to better recapitulate the microenvironment and biology of GIST. Methods: Tumor acquisition was performed under an IRB-approved protocol. Following tumor resection, we anesthetized NOD-scid (NS) or NS gamma (NSG) mice and performed a midline laparotomy. 2′2 mm tumor fragments were sutured into the abdominal viscera of NS (N=10) or NSG (N=15) mice. Tumors were imaged every 3-4 wks with ultrasound (US). 2 mice were also evaluated with PET scan. Results: We have xenografted GISTs from 3 patients into 25 mice with an 80% success rate and 4% perioperative mortality. We observed tumor progression in the liver (9/10), renal capsule (8/10), lesser sac (2/3), or gastric wall (1/2) of mice. This included 14 primary xenografts and 11 passaged xenografts. At 21-196 d (median 46 d), tumor size averaged 473±736 mm3 (median 104 mm3, range 2.2-2683 mm3) by US. In addition, 30% (6/20) of mice developed metastatic disease based upon US, necropsy, histology and/or KIT immunostaining. We also determined that 2/2 tumors were FDG-avid on PET. Conclusions: To our knowledge, we report the first intra-peritoneal xenograft model of human GIST using patient-derived tumor tissue. This novel in vivo approach is a reproducible model of human GIST that replicates the tumor microenvironment, heterogeneity, and metastatic potential of a human GI sarcoma. As compared to current research tools/models, this approach may allow researchers to better predict chemotherapeutic responses, further understand the tumor biology of GIST, and serve as a means to propagate additional tumor tissue for subsequent experimental analyses.