Pharmaceutical reversal of Dkk1-induced LRP6 endocytosis prevents cancer cachexia and prolongs survival

Cancer cachexia with profound weight loss and frailty impairs quality of life, limits cancer therapy and decreases survival, against which no effective therapy is available. Dkk1 is a secreted antagonist of Wnt/β-catenin pathway via interacting with Wnt co-receptors LRP5 and 6 (LRP5/6) and inducing their endocytosis1-4.  Although Dkk1 is critical for animal development3,5, its mRNA is undetectable in most adult organs6. Of note, elevated circulating Dkk1 leads to poor prognosis in patients with a variety of types of cancer by a completely unknown mechanism. Here, we show that administration of a recombinant Dkk1 protein accelerated cancer cachexia-related death through inducing LRP6 endocytosis but not β-catenin inhibition, whereas pharmacological blockade of Dkk1-induced membrane LRP6 downregulation completely prevented cancer cachexia and robustly prolonged survival in tumor-bearing mice. Pharmacological blockade of Dkk1-induced membrane LRP6 downregulation prevented alterations of a number of GPCR pathways and all main cancer cachexia-related pathways in skeletal muscle of mice bearing tumor as shown by a genome-wide transcriptional analysis. Furthermore, Dkk1 injection into hindlimb directly triggered activations of GPCR pathways and cachexia-related pathways. These findings establish a key role of the Dkk1-LRP6 axis in cancer cachexia development through affecting GPCR pathways and suggest a highly promising therapeutic approach for preventing cancer cachexia.