Molecular and Cellular Pathobiology Detection of Pancreatic Cancer–Induced Cachexia Using a Fluorescent Myoblast Reporter System and Analysis of Metabolite Abundance Paul T. Winnard Jr 1 , Santosh K. Bharti 1 , Marie-France Penet 1,2 , Radharani Marik 1 , Yelena Mironchik 1 , Flonne Wildes 1 , Anirban Maitra 2,3 , and Zaver M. Bhujwalla 1,2 Abstract The dire effects of cancer-induced cachexia undermine treat- ment and contribute to decreased survival rates. Therapeutic options for this syndrome are limited, and therefore efforts to identify signs of precachexia in cancer patients are necessary for early intervention. The applications of molecular and func- tional imaging that would enable a whole-body "holistic" approach to this problem may lead to new insights and advances for diagnosis and treatment of this syndrome. Here we have developed a myoblast optical reporter system with the purpose of identifying early cachectic events. We generated a myoblast cell line expressing a dual tdTomato:GFP construct that was grafted onto the muscle of mice-bearing human pancreatic cancer xenografts to provide noninvasive live imag- ing of events associated with cancer-induced cachexia (i.e., weight loss). Real-time optical imaging detected a strong tdTo- mato fluorescent signal from skeletal muscle grafts in mice with weight losses of only 1.2% to 2.7% and tumor burdens of only approximately 79 to 170 mm 3 . Weight loss in cachectic animals was also associated with a depletion of lipid, choles- terol, valine, and alanine levels, which may provide informa- tive biomarkers of cachexia. Taken together, our findings dem- onstrate the utility of a reporter system that is capable of tracking tumor-induced weight loss, an early marker of cachex- ia. Future studies incorporating resected tissue from human pancreatic ductal adenocarcinoma into a reporter-carrying mouse may be able to provide a risk assessment of cachexia, with possible implications for therapeutic development. Cancer Res; 76(6); 1441–50. Ó2015 AACR. Introduction Cancer-induced cachexia occurs in several cancers and is a significant cause of morbidity and mortality (1–4). In pancreatic cancer, especially, the syndrome affects approximately 80% of patients (2). Cachexia compromises the effectiveness of cancer therapies, and contributes to decreased survival rates (1–6). An international effort has led to a more precise definition of cancer- associated cachexia and to objective measures of cachectic symp- toms with the purpose of early diagnosis of the syndrome to achieve effective treatments (4). Cachexia is currently defined as an unintentional weight loss of >5% over a 6-month period, or a body mass index (BMI) <20 kg/m 2 with ongoing weight loss of >2%, or sarcopenia and ongoing weight loss of >2% (4). Non- invasive biomarkers that identify precachectic patients who will progress to cachexia and refractory cachexia (4) are an urgent and unmet requirement. If the onset of cachexia is detected early, nutritional interventions appear to delay its progression (7). However, the systemic and molecular mechanisms initiating and driving cancer cachexia, as it presents in the clinic, have yet to be definitively identified and the syndrome remains an enigma even in the 21st century. Despite extensive preclinical and clinical investigations into therapies aimed at reversing cachectic progression (7–10), to date only complete eradication of the cancer has been effective (1, 11). This is problematic as cachexia is most often recognized at later stages that include metastatic disease, where complete surgical resection of all malignant tissue is not feasible (12). Under these conditions, and independent of cancer type, it has been repeatedly demonstrated that cachexia is closely associated with increased comorbidities, more complications during surgeries, less respon- siveness to chemo- and radiotherapies, and thus, lower survival rates (1–3, 5, 11–13). Transplantable tumor tissues or cell lines and carcinogen- induced cancers have been extensively studied (14–18), and have provided important data strongly implicating hormones, cytokines, and catabolic pathways as contributing factors to cancer-associated cachexia. However, mechanistic results with respect to causality of muscle-specific wasting have often not been confirmed in clinical studies (19–26). Few rodent models of pancreatic cancer cachexia have been available, resulting in a sparse dataset to draw conclusions from (15, 16). Moreover, currently there is no imaging reporter system for longitudinal monitoring to detect the early onset of this syndrome. The availability of such a reporter system in combination with noninvasive metabolic imaging would allow the holistic 1 Division of Cancer Imaging Research, The Russell H. Morgan Depart- ment of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland. 2 Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland. 3 The University of Texas MD Ander- son Cancer Center, Houston,Texas. Note: Supplementary data for this article are available at Cancer Research Online (http://cancerres.aacrjournals.org/). Corresponding Author: Zaver M. Bhujwalla, The Johns Hopkins University School of Medicine, Traylor Bldg., Room 208C, 720 Rutland Avenue, Baltimore, MD 21205. Phone: 410-955-9698; Fax: 410-614-1948; E-mail: zaver@mri.jhu.edu doi: 10.1158/0008-5472.CAN-15-1740 Ó2015 American Association for Cancer Research. Cancer Research www.aacrjournals.org 1441 Downloaded from http://aacrjournals.org/cancerres/article-pdf/76/6/1441/2748130/1441.pdf by guest on 19 June 2022