Staging of metastatic pancreatic cancer in orthotopic mouse models by fluorescence laparoscopy is improved by an LED light source

SURGICAL ONCOLOGY I RON overexpression accelerates tumorigenesis and induces metastasis in a KRAS mutant mouse model of pancreatic cancer Michele L Babicky MD*, Evangeline Mose BSc, Karly Maruyama BSc, Meg Harper BSc, Dawn Jaquish BSc, Randall French PhD, Andrew M Lowy MD, FACS University of California-San Diego, San Diego, CA INTRODUCTION: The RON receptor is increasingly overexpressed during pancreatic cancer progression and has been implicated as a mediator of KRAS oncogene addiction. It remains unclear if RON promotes disease progression or simply represents an epiphenomenon. METHODS: To address this, we generated a transgenic mouse which over-expressed wt-RON in a pancreas-specific manner using Pdx-1, the identical promoter used to drive cre expression in the Kras-LSLGD12/Pdx-1-cre (KC) strain that develops pancreatic duct neoplasia. RON over-expression was verified via Western and IHC. Pdx-1/RON mice were crossed with LSL-KRASG12D mice to yield mice (RK), then bred to Pdx-1-Cre mice to combine RON overexpression in the presence of oncogenic KRAS (RCK). RCK mice were aged and sacrificed at various time points and histology compared to KC controls. RESULTS: Pdx-1-RON mice developed no pancreatic phenotype prior to 12 months. At 18 months, one of 4 animals developed primary pancreatic adenocarcinoma with lung metastasis. RON overexpression in KRAS mutant mice (RCK) led to accelerated PanIN progression compared to KC (p⬍0.05). In RCK, PanIN’s were visible at 6 weeks, with invasive carcinoma detectable at 6 months compared to KC mice (average latency ⬎1yr). Metastatic disease was visible in RCK mice at 9 months. CONCLUSIONS: RON overexpression alone results in pancreatic cancer at long latency. In the presence of KRAS mutation, RON overexpression markedly accelerates PanIN progression to primary and metastatic pancreatic duct cancer. This data supports a role for RON in pancreatic carcinogenesis and this model may prove useful for investigations regarding the role of the RON receptor in pancreatic cancer biology.

RESULTS: Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor in the peritoneal cavity. Improved detection of more and smaller lesions compared to standard xenon bright field laparoscopy was achieved. With adjustments to the LED light source, we could simultaneously detect tumor lesions of different fluorescent colors as well as surrounding structures with minimal autofluorescence. CONCLUSIONS: In conclusion, we have demonstrated that by using an LED light source with adjustments to the red, blue and green wavelengths, we can simultaneously identify tumor metastases expressing fluorescent proteins of different wavelengths without compromising background illumination. Further development of this technology for clinical use can improve the staging and treatment of pancreatic cancer.

Predictors of outcome in patients with recurrent gastrointestinal stromal tumors Jeremiah L Deneve DO, Colin M Parsons MD, Jongphil Kim PhD, Anthony P Conley MD, Jonathan S Zager MD, FACS, Douglas G Letson MD, Ricardo J Gonzalez MD H Lee Moffitt Cancer Center, Tampa, FL INTRODUCTION: Background: Recurrence after initial resection of advanced gastroinstestinal stromal tumors (GIST) is common despite tyrosine kinase inhibitor (TKI) therapy. Appropriate management of patients with recurrent GIST is not well defined. Our aim was to identify predictive factors associated with outcome in this population. METHODS: We identified patients (pts) with advanced/recurrent GIST who underwent resection from our institutional database from 1999-2009. Significant variables for recurrence and survival were analyzed.

Staging of metastatic pancreatic cancer in orthotopic mouse models by fluorescence laparoscopy is improved by an LED light source Cristina Angela Metildi MD, Sharmeela Kaushal PhD, Chanae Hardamon BSc, Hop Tran Cao MD, George A Luiken MD, Robert M Hoffman PhD, Michael Bouvet MD, FACS University of California-San Diego, San Diego, CA, OncoFluor, Inc, San Diego, CA and AntiCancer, Inc, San Diego, CA INTRODUCTION: The aim of this study was to improve fluorescence laparoscopy with the use of an LED light source. In addition, the optimal fluorophore was determined to improve accurate identification and localization of tumor deposits without loss of background illumination. METHODS: Human pancreatic cancer models were established with fluorescent FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, or BxPC-3

© 2011 by the American College of Surgeons Published by Elsevier Inc.

cancer cells implanted in 6-week-old female athymic mice. Two weeks post-implantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail vein injection of CEA and/or CA19-9 antibodies conjugated with Alexa 488- or Alexa 555. Cancer lesions were detected and localized under each light mode. Intravital images were obtained with the Maestro CRI Small Animal Imaging System, serving as a positive control. Tumors were collected for histologic review.

RESULTS: Of the 193 pts with GIST, 78 pts (46.4%) underwent treatment for recurrent/advanced GIST with a median follow up of 38 months (0.3-61). Final margin after initial primary resection was R0/R1 in 60 pts (77%) and R2 in 18 pts (23%). Thirty-eight pts (49%) received adjuvant TKI therapy. Age, gender, tumor size, mitotic rate or adjuvant TKI therapy were not associated with survival on univariate analysis, whereas stage at initial diagnosis (p⫽0.0015), initial resection margin (p⬍0.0001), presence of multifocal disease (p⫽0.002), ⬎2 procedures for recurrence (p⫽0.04), and TKI resistance (p⬍0.0001) were significant. Resistance to TKI therapy (p⫽0.04, 95% CI 1.0-5.6) and incomplete resection at the time of initial primary GIST resection (p⫽0.002, 95% CI 1.6-9.6) were

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ISSN 1072-7515/11/$36.00 doi:10.1016/j.jamcollsurg.2011.06.314