Abstract 634: Impact of tumor inoculation site on the development of cancer cachexia

Background and Aim The incidence of cancer cachexia varies greatly among tumor type. Although certain tumor types are more commonly associated with cachexia, even for the same tumor type, the degree to which patients exhibit cachexia varies. This is due to variations in tumor phenotype and host genotype that contributes to the development of cancer cachexia. The influence of the site of tumor growth on the development of cancer cachexia remains unclear. In this study, we evaluated if differences in tumor microenvironment would affect the development of cancer cachexia in a murine model. Methods The same number of colon26 cells (5×10⁁6 cells/mouse) was inoculated subcutaneously or intraperitoneally in 8-week-old male BALB/c mice. Body weight, food intake, and tumor size were monitored. On day 14 after the tumor inoculation, mice were anesthetized and blood collected, and the weight of peritesticular adipose tissue, gastrocnemius muscle and heart were measured. 23 plasma cytokines were determined by using the Bio-Plex array system and plasma Myostatin and Activin A levels were measured by ELISA. Expression of MuRF-1 and Antrogin-1, which are required for muscle atrophy, in gastrocnemius muscle or heart was assessed by RT-PCR. Results The body weight, adipose tissue and gastrocnemius muscle decreased in tumor-bearing mice. Interestingly, a reduction in heart weight was observed in the intraperitoneal tumor group but not in the subcutaneous group. The weight loss of the body, adipose tissue and gastrocnemius was more severe in the intraperitoneal group than in the subcutaneous group. Atrogin 1 and MuRF1 mRNA expressions in the gastrocnemius muscle increased significantly in both groups of tumor-bearing mice, however, in the myocardium, expression of these mRNAs increased in the intraperitoneal group but not in subcutaneous group. As for plasma cytokine levels, several cytokine levels including IL-6, TNF-α, and activing A of tumor-bearing mice were significantly higher than those of control mice. Eotaxin and G-CSF levels in the intraperitoneal tumor group were higher than in the subcutaneous group. Conclusion Based on these data, we believe that differences in microenvironment where tumor cells develop can affect the progression and phenotype of cancer cachexia through alterations in various circulating factors derived from the tumor microenvironment. Citation Format: Takashi Ando, Takeshi Ishikawa, Tastuzo Matsuyama, Tomoyo Yasuda, Toshifumi Doi, Tetsuya Okayama, Naoyuki Sakamoto, Satoshi Kokura, Yuji Naito, Yoshito Itoh. Impact of tumor inoculation site on the development of cancer cachexia. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 634.