Evaluation of bioluminescent imaging for noninvasive monitoring of colorectal cancer progression in the liver and its response to immunogene therapy

Molecular Cancer BioMed Central Research Open Access Evaluation of bioluminescent imaging for noninvasive monitoring of colorectal cancer progression in the liver and its response to immunogene therapy Maider Zabala1,4, Pilar Alzuguren1, Carolina Benavides2, Julien Crettaz1, Gloria Gonzalez-Aseguinolaza1, Carlos Ortiz de Solorzano2, Manuela Gonzalez-Aparicio1, Maria Gabriela Kramer1,5, Jesus Prieto3 and Ruben Hernandez-Alcoceba*1 Address: 1Division of Gene Therapy and Hepatology. CIMA, University of Navarra. Foundation for Applied Medical Research. Av. Pio XII. Pamplona, Spain, 2Morphology and Imaging Unit. CIMA, University of Navarra. Foundation for Applied Medical Research. Av. Pio XII. Pamplona, Spain, 3CIBERehd. University Clinic of Navarra. Pamplona, Spain, 4Institute for Stem Cell Biology and Regenerative Medicine, University of Stanford, 1050 Arastradero Road, Palo Alto, CA, USA and 5Peter MacCallum Cancer Research Institute, Cancer Immunology Program, St Andrews Place, East Melbourne, 3001 Australia Email: Maider Zabala - ; Pilar Alzuguren - ; Carolina Benavides - ; Julien Crettaz - ; Gloria Gonzalez-Aseguinolaza - ; Carlos Ortiz de Solorzano - ; Manuela Gonzalez-Aparicio - ; Maria Gabriela Kramer - ; Jesus Prieto - ; Ruben Hernandez-Alcoceba* - * Corresponding author Published: 7 January 2009 Molecular Cancer 2009, 8:2 doi:10.1186/1476-4598-8-2 Received: 22 September 2008 Accepted: 7 January 2009 This article is available from: http://www.molecular-cancer.com/content/8/1/2 © 2009 Zabala et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract Background: Bioluminescent imaging (BLI) is based on the detection of light emitted by living cells expressing a luciferase gene. Stable transfection of luciferase in cancer cells and their inoculation into permissive animals allows the noninvasive monitorization of tumor progression inside internal organs. We have applied this technology for the development of a murine model of colorectal cancer involving the liver, with the aim of improving the pre-clinical evaluation of new anticancer therapies. Results: A murine colon cancer cell line stably transfected with the luciferase gene (MC38Luc1) retains tumorigenicity in immunocompetent C57BL/6 animals. Intrahepatic inoculation of MC38Luc1 causes progressive liver infiltration that can be monitored by BLI. Compared with ultrasonography (US), BLI is more sensitive, but accurate estimation of tumor mass is impaired in advanced stages. We applied BLI to evaluate the efficacy of an immunogene therapy approach based on the liver-specific expression of the proinflammatory cytokine interleukin-12 (IL-12). Individualized quantification of light emission was able to determine the extent and duration of antitumor responses and to predict long-term disease-free survival. Conclusion: We show that BLI is a rapid, convenient and safe technique for the individual monitorization of tumor progression in the liver. Evaluation of experimental treatments with complex mechanisms of action such as immunotherapy is possible using this technology. Page 1 of 13 (page number not for citation purposes) Molecular Cancer 2009, 8:2 Background The liver is the most frequent site for metastases from colorectal cancer. Approximately 10–25% of colon cancer patients present one or multiple liver metastases at the time of diagnose [1]. At least in 30% of these cases the liver is the only organ affected, apart from the tumor in the gastrointestinal tract. Moreover, recurrence after surgical removal of the primary lesion occurs mainly in the liver, with a 20–25% rate of metachronous liver metastases. Potentially curative resection of hepatic tumors is not feasible in more than 75% of the cases due to large size, elevated number and/or unfavourable localization of lesions, or poor liver function. Nonsurgical approaches including systemic chemotherapy and regional treatments are the only options for these patients. Local control is often achieved and these techniques are rapidly improving [2,3], but a significant increase in long-term survival is not guaranteed. Therefore, hepatic metastases from colon cancer are frequently observed in the clinic and they are the most frequent cause of death in these patients. Advances in the management of this disease will probably require the combination of standard care and new therapies that are still in the experimental stage. Immunotherapy is one of these alternatives [4]. Systemic or local administration of vectors driving expression of immunostimulatory cytokines such as interleukin-12 (IL12) has demonstrated potent antitumor effects in preclinical studies [5-8]. However, further optimization of this approach is required, and improvement in animal models is needed so that research in this area can generate more clinically relevant results [9,10]. In a previous study [11], we described a High-Capacity (gutless) adenoviral vector carrying a liver-specific inducible system for the expression of murine IL-12 (GL-Ad/RUmIL-12). Intravenous administration of this vector eliminated intrahepatic colon cancer in a murine model when intense production of IL-12 was induced at early stages of the disease. If more restrictive conditions are used (larger tumors and lower dose of vector that leads to moderate IL-12 concentration) the antitumor response was heterogeneous (manuscript in preparation), as observed with many other experimental approaches [12]. In these cases, a more detailed characterization of the partial responses would be desirable, and longitudinal monitoring of individual subjects could identify transient antitumor effects. Implantation of certain colon cancer cell lines in the liver of syngeneic mice constitutes one kind of intrahepatic cancer model [13]. Although each model has its own limitations, progressive growth and extra hepatic dissemination of these tumors often leads to the death of the animal, recapitulating some aspects of the natural history found in humans. However, monitoring progression in these internal tumors by direct measure- http://www.molecular-cancer.com/content/8/1/2 ment requires repeated laparotomy or large groups of animals to be sacrificed at different time points, thus precluding an individualized follow-up. Different noninvasive imaging techniques have been developed to overcome these limitations. Some of them such as ultrasonography (US) [14], computerized tomography (CT) [15], positron emission tomography (PET) [16], single photon emission computed tomography (SPECT) [17] and magnetic resonance imaging (MRI) [18,19] are adaptations of clinical imaging devices to the use in small animals. Others such as fluorescence imaging (FLI) [20] and bioluminescent imaging (BLI) (...truncated)