Abstract
Cachexia is strongly associated with a poor prognosis in cancer patients but the biological trigger is unknown and therefore no therapeutics exist. The loss of skeletal muscle is the most deleterious aspect of cachexia and it appears to depend on secretions from tumor cells. Models for studying wasting in cell culture consist of experiments where skeletal muscle cells are incubated with medium conditioned by tumor cells. This has led to candidates for cachectic factors but some of the features of cachexia in vivo are not yet well-modeled in cell culture experiments. Mouse myotube atrophy measured by myotube diameter in response to medium conditioned by mouse colon carcinoma cells (C26) is consistently less than what is seen in muscles of mice bearing C26 tumors with moderate to severe cachexia. One possible reason for this discrepancy is that in vivo the C26 tumor and skeletal muscle share a circulatory system exposing the muscle to tumor factors in a constant and increasing way. We have applied Transwell®-adapted cell culture conditions to more closely simulate conditions found in vivo where muscle is exposed to the ongoing kinetics of constant tumor secretion of active factors. C26 cells were incubated on a microporous membrane (a Transwell® insert) that constitutes the upper compartment of wells containing plated myotubes. In this model, myotubes are exposed to a constant supply of cancer cell secretions in the medium but without direct contact with the cancer cells, analogous to a shared circulation of muscle and cancer cells in tumor-bearing animals. The results for myotube diameter support the idea that the use of Transwell® inserts serves as a more physiological model of the muscle wasting associated with cancer cachexia than the bolus addition of cancer cell conditioned medium. The Transwell® model supports the notion that the dose and kinetics of cachectic factor delivery to muscle play a significant role in the extent of pathology.
Highlights
Cachexia is a devastating consequence of cancer in ∼50% of patients (Tisdale, 2009)
Myotubes cultured in a well that contains cancer cells seeded on a Transwell insert is shown schematically and photographically (Figures 1B,C)
A mouse specific ELISA was used to measure LIF levels in myotube cultures containing added cancer cell conditioned medium (CM) and in myotube cultures incubated with Transwell R inserts containing cancer cells
Summary
Cachexia is a devastating consequence of cancer in ∼50% of patients (Tisdale, 2009). It is characterized by elevated metabolism and whole body wasting that is not reversed by feeding (Fielitz, 2016). Among the many models for these studies are cell culture experiments in which cachexia target cells, such as skeletal muscle, are incubated with medium conditioned by tumor cells (Penna et al, 2016). Cancer cell conditioned medium (CM) treatment of target cells has been used as an in vitro approach to study the mechanism of wasting in muscle cells (Zhang et al, 2011; Puppa et al, 2014; Silva et al, 2015; Bohnert et al, 2016; Fukawa et al, 2016)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call