Leukemia inhibitory factor via the toll-like receptor 5 signaling pathway involves aggravation of cachexia induced by human gastric cancer-derived 85As2 cells in rats

Cancer cachexia is highly prevalent in gastric cancer patients and is characterized by decreased food consumption and body weight. We previously created a rat model of cancer cachexia using MKN45cl85 and 85As2 cells derived from human gastric cancer. The 85As2 cells induced cachexia more potently than MKN45cl85 cells did. To clarify the mechanism underlying the difference in the cachexia-inducing ability of these cells, we conducted a DNA microarray analysis, with a focus on cell proliferation and the production of leukemia inhibitory factor (LIF), a cachexia-inducing factor. The plasma human LIF levels of 85As2-induced cachexic rats increased in parallel with the worsening of symptoms whereas the plasma levels of MKNcl85 were low. 85As2 cells displayed more genetic changes than MKN45cl85 cells did, which were related to Toll-like receptor (TLR) 4//5 signaling. Stimulation of both the cells with TLR4 (lipopolysaccharide) or TLR5 (flagellin) agonists did not affect proliferation. However, in 82As2 cells, LIF production was significantly increased by stimulation with TLR5, which was suppressed by an inhibitor of interleukin-1 receptor-associated kinase-1/4, which are important factors in the TLR5 signaling pathway. In conclusion, it is possible that the increase in LIF production through the activation of the TLR5 signaling pathway contributes to the cachexia-inducing ability of 85As2 cells. Gene expression in MKN45cl85 and 85As2 cells was measured. MKN45cl85 cells were orthotopically grafted into mice, and peritoneal cavity cells were collected from specimens exhibiting peritoneal metastasis. These cells were then cultured and xenografted repeatedly. This established another cell line was 85As2. MKN45cl85 and 85As2 cells were cultured in a 10 cm dish until they were semi-confluent. Total RNA was extracted for DNA microarray analysis. Three RNA samples from cells cultured on different days were prepared.