The effect of altered Toll-like receptor 4 signaling on cancer cachexia

Objective To determine whether mice unable to mount an intact inflammatory response because of a Toll-like receptor (TLR) pathway defect will develop less severe cancer cachexia. Design Prospective animal study. Setting Academic research center. Subjects Six- to eight-week-old, female C3H/HeJ mice (17-18 g) and age-, weight-, and sex-matched wild-type C3H/HeN mice, differing in that the HeJ mice have nonfunctional TLR4 due to a TLR4 double mutation (TLR4 d/d ). Intervention The mice were inoculated with equal numbers of SCCF-VII cells and housed in individual cages. Main Outcome Measures Food intake, body weight, pretumor and posttumor body composition, circulating cytokines, and levels of a marker of muscle atrophy were analyzed. Results The wild-type HeN mice weighed less on average than the TLR4 d/d mice (2.6 g vs 4.9 g) ( P = .01). They consumed more food, had smaller tumors, and had less lean body mass and fat mass than the TLR4 d/d mice. Interleukin 1β level was significantly elevated in the tumor-bearing HeN mice (mean gain of 259 pg/mL) but not in the TLR4 d/d mice ( P = .03). Both mouse strains had evidence of muscle atrophy. Conclusions In spite of increased food intake and smaller tumors, the wild-type HeN mice had more severe cachexia than the TLR4 d/d mice. The impaired ability to secrete proinflammatory cytokines such as interleukin 1β may protect these animals from developing severe cancer cachexia. This animal model represents a novel system in which the host contributions to cachexia may be further studied.