Project Funding Details

One third of cancer deaths are due to cachexia, a multi-factorial metabolic syndrome, characterized by an excessive fat and lean mass loss. Prevention of muscle mass loss in presence of cancer has been shown to be beneficial for lifespan in preclinical model of cancer cachexia. Muscle mass loss is regulated by transcriptional programs that induce the expression of atrogenes, such as Trim63/MuRF1, a muscle specific E3 ubiquitin ligases responsible for sarcomeric proteins' proteolysis. We reported that tumor growth induces a transcriptomic reprogramming in myofibers leading to muscle wasting. Specifically, we demonstrated that perturbation of BMP pathway underlies lean mass loss in cachexia; besides, several antagonists of the pathway are expressed by different cell populations in muscle. Single nuclei multiome experiment showed that cancer growth alters the cellular landscape in muscle of C26 tumor bearing mice, also affecting gene expression profile of cell populations, contributing to the onset of the cachectic phenotype. Recently, it has been demonstrated that catabolic conditions (e.g. denervation), trigger myonuclei heterogeneity and desynchronization, so we decided to investigate this feature for the first time also in cachexia. From our preliminary results, we hypothesize that myonuclei desynchronization may happen also in cachexia. Specifically, only in the presence of the tumor, a distinct subset of myonuclei expressing Trim63 is emerging. However, we don't know if its expression is activated homogeneously in a single myofiber or by nuclei subdomains inside myofibers. The aim of this fellowship is to understand the spatial dynamics of myonuclear desynchronization and which are the signals that influence muscle heterogeneity, and from which cell populations are coming from, destabilizing myofibers and leading to cachexia. In this fellowship I will investigate skeletal muscle cellular heterogeneity and the role of myonuclei Trim63 appearance in cachexia, both in preclinical model of cachexia and in cancer patients. First, I will dissect where (in which nuclei) Trim63 transcriptional program is activated in skeletal muscle sections of C26 tumor bearing mice, using RNAscope. To verify if what is happening in the cachectic mouse model is recapitulated in humans, I will check with RNAscope Trim63 gene expression pattern in muscles biopsies of colon cancer patients. Finally, to gain more insights on the mechanisms and neighboring signals responsible for the desynchronization of myonuclei Trim63, we will exploit the use of single-cell high resolution spatial transcriptomic technology, both on muscles of C26 tumor bearing animals and muscle biopsies of oncological patients. From this experimental plan, we would expect an heterogenous gene expression pattern of Trim63 signal, whether it's localized in specific domains of the myofiber or homogeneously expressed by whole single fibers within skeletal muscle. Additionally, spatial transcriptomics will provide us hypotheses about the mechanistic insights on cell-cell interaction in muscle that may be responsible for myonuclei heterogeneity in the presence of cancer, consequentially causing myofibers destabilization and detrimental atrophy. Dissecting the mechanisms underlying the exchange of signals of cellular crosstalk with cancer growth in skeletal muscle, provides a foundation for novel pathogenetic hypothesis and potentially innovative therapeutic approaches to counteract cancer cachexia.