Abstract A6: The ES-2 ovarian cancer causes muscle wasting in vitro and in vivo: A novel experimental model of cancer cachexia
Authors: Bonetto Andrea , Puppa Melissa J. , Carson James A. , Zimmers Teresa A. 
Published: August 2014

Cancer cachexia is a devastating consequence of cancer. A multifactorial syndrome characterized by skeletal muscle and adipose tissue wasting, cachexia cannot be fully reversed by nutritional support. Cachexia occurs in up to one half of all cancer patients and correlates with poor performance status, reduced quality of life and high mortality. Cachexia results both from the tumor-host interaction, as well as from the anti-cancer therapies. The only cure for cachexia is definitive removal of the tumor. In ovarian cancer, cachexia is associated with malnutrition and a general inflammatory state, characterized by high levels of pro-inflammatory cytokines (such as IL-6, TNF) in ascites and blood. Due to the absence of proper experimental models, cachexia also represents a generally understudied aspect of ovarian cancer that deserves more attention. In order to establish novel experimental models for the study of ovarian cancer cachexia, we tested several human ovarian cancer cell lines with different degrees of differentiation for their capability to induce cachexia in vivo and muscle wasting in vitro.

In a xenograft model, female Nu/Nu athymic nude mice were injected i.p. with 10x106 OVCAR-3, SK-OV-3 and ES-2 human ovarian cancer cells to mimic disseminated abdominal disease. After 60 days, the OVCAR-3 and SK-OV-3 cell lines did not result in detectable tumors. In contrast, beginning 8 days after inoculation, ES-2 cells caused severe cachexia with marked loss of body weight and with massive ascites accumulation in the peritoneal cavity. Within the ascites, ES-2 cells were not shown to aggregate, but existed more as a single-cell suspension or very small cell clumps. Some ES-2 cells also disseminated and infiltrated the pancreas, diaphragm and other organs, forming multiple solid tumors of histology consistent with clear cell carcinoma, characterized by sheets of cells with irregularly shaped nuclei and abundant cytoplasm. Muscles, including tibialis, gastrocnemius, quadriceps and heart, of tumor-bearing mice appeared markedly smaller than normal controls (~-20% vs. control; p&lt;0.01). Muscle loss was due to fiber atrophy, as observed by reduced tibialis myofiber area. Fat pads and spleen were reduced in size, while the liver was unchanged. Piximus imaging revealed decreased bone mineral density (-16% vs. control; p&lt;0.05). Consistent with reports in human ovarian cancer cachexia, IL-6 levels were markedly elevated in both blood and ascites. In quadriceps muscle, cachexia was also associated with high levels of phosphorylated STAT3 (pSTAT3), whose causal role in tumor-associated muscle wasting was previously reported in our laboratory.

In order to understand whether tumor-derived factors were directly responsible for the wasting effects observed in vivo, differentiated C2C12 murine myotubes were exposed to conditioned medium from ES-2 cell cultures and evaluated for effects on myotube size. After 48 hours, the average diameter of C2C12 myofibers was severely reduced (-28% vs. control; p&lt;0.001). These effects were evident at a low concentration of supernatant and were associated with elevated pSTAT3 levels.

In conclusion, here we report that ES-2 tumor cells directly induce muscle atrophy, both in vitro and in vivo. Thus this is a new experimental model for the study of ovarian cancer cachexia. This model and future similar models will aid in identifying novel molecular mediators that could be effectively targeted in order to improve muscle wasting associated with ovarian cancer.

Citation Format: Andrea Bonetto, Melissa J. Puppa, James A. Carson, Teresa A. Zimmers. The ES-2 ovarian cancer causes muscle wasting in vitro and in vivo: A novel experimental model of cancer cachexia. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: From Concept to Clinic; Sep 18-21, 2013; Miami, FL. Philadelphia (PA): AACR; Clin Cancer Res 2013;19(19 Suppl):Abstract nr A6.