Molecular Subtypes of Human Skeletal Muscle in Cancer Cachexia
Cancer-associated muscle wasting associates with poor clinical outcomes1, but its underlying biology is largely uncharted in humans2. Unbiased RNAome analysis (coding and non-coding RNAs) with unsupervised clustering using Integrative Non-negative Matrix Factorization (intNMF)3 provides an avenue to identify distinct molecular subtypes, here applied to muscle of patients with colorectal or pancreatic cancer. Rectus abdominis biopsies from 84 patients was profiled using high-throughput next generation sequencing. Here we show that intNMF with stringent quality metrics of clustering identifies 2 highly coherent molecular subtypes within muscle of patients with cancer. Patients in Subtype 1 (vs Subtype 2) showed clinical manifestations of cachexia: high-grade weight loss, low muscle mass, atrophy of Type IIA and Type IIX muscle fibres and reduced survival. Based on differential expression between the subtypes, our results indicate biological processes that may contribute to cancer-associated loss of muscle mass and function, including altered post-transcriptional regulation, and perturbation of neuronal systems, cytokine storm/cellular immune response, extracellular matrix, and metabolic abnormalities spanning xenobiotic metabolism, hemostasis, signal transduction, embryonic/pluripotent stem cells, and amino acid metabolism. Differential expression between subtypes indicates involvement of multiple, intertwined higher-order gene regulatory networks, suggesting potential for interacting (hub)lncRNA-miRNA-mRNA interaction networks as targets for future research. Overall design: Whole transcriptome profiling (small RNA and RNA seq) from muscle of patients with cancer was performed to decipher complex biological processes contributing to muscle loss.