ABSTRACT: Cancer cachexia is a debilitating syndrome of involuntary body mass loss featuring profound muscle wasting and high mortality. Notably, cardiac wasting is prominent in cancer patients and cancer survivors. Progress in this field has been limited by the absence of experimental human models. To address this translational gap, we developed a robust human iPSC-derived cardiac myocyte (hiPSC-CM) platform to model cancer cachexia using conditioned media and transwell co-culture with C26 and HCT116 tumor cell lines. Cachectic hiPSC-CMs exhibited reduced contraction amplitude, prolonged relaxation time, and elevated oxygen consumption rate, reflecting both contractile dysfunction and metabolic dysregulation. Mechanistically, we identified suppression of the AKT-mTORC1-S6 translational signaling axis, evidenced by reduced total and phospho-AKT (Ser473), decreased phospho-S6 (Ser240/244) / total S6 ratio, and transcriptional downregulation of RPTOR. These changes were accompanied by significant FOXO1/3 activation, as demonstrated by reduced phospho/total FOXO ratios and nuclear translocation of FOXO1, promoting downstream atrophic remodeling. Interrogation of the Atrogin-1/Calcineurin A/NFAT axis identified this pathway as a central mediator of cachexia-induced cardiac atrophy. Cachectic cardiac myocytes exhibited significant upregulation of Atrogin-1, leading to a marked decrease in Calcineurin A protein levels. This, in turn, impaired nuclear translocation of NFAT, thereby suppressing its transcriptional activity and downstream cell growth signaling. These molecular changes were accompanied by increased autophagic flux, as indicated by elevated LC3BII/LC3BI ratios. The convergent suppression of anabolic and activation of catabolic pathways produced substantial cardiac atrophy. Following withdrawal of cachexia-inducing stimuli, Atrogin-1 and autophagy markers normalized within one week; however, contractile and metabolic impairments persisted, indicating delayed functional recovery. Collectively, these findings establish the FOXO/Atrogin-1/Calcineurin A/NFAT axis, operating within the broader context of AKT-mTORC1 suppression, as a central regulatory mechanism of cachexia-induced cardiac wasting and identify this pathway as a tractable therapeutic target.
