Cancer stemness-modulating (CSM) proteins in pan-cancer chemoresistance: regulatory roles and mechanisms.

Cancer stemness is a property of cancer cells that plays critical roles in tumorigenesis and therapeutic resistance. We previously identified and categorized, based on literature evidence, a group of fourteen cancer stemness-modulating (CSM) circular RNAs (circRNAs) in colorectal cancer (CRC), which we termed CSM-circRNAs. In the present work, we show that the proteins regulated by these CRC CSM-circRNAs, with one exception for which information is currently unavailable, are bona fide modulators of cancer stemness across a wide range of cancer types. We, therefore, designate these proteins as CSM-proteins. As chemoresistance is a major trait of cancer stemness, we further investigated the molecular mechanisms through which CSM-proteins contribute to chemoresistance. Our analysis reveals that twelve CRC CSM-proteins are implicated in chemoresistance across fourteen cancer types and resistance to ten therapeutic agents. Nine distinct chemoresistance mechanisms are identified and organized into five broader functional axes: survival, drug processing, genome maintenance, plasticity and adaptation, leading us to propose an integrated mechanistic framework for CSM-protein-mediated chemoresistance. Most CSM-proteins operate across multiple functional axes in different cancer contexts, with survival-associated mechanisms, particularly apoptosis evasion, and epithelial-mesenchymal transition-associated plasticity emerging as the predominant modes of chemoresistance. Furthermore, transcriptional regulatory CSM-proteins exhibit broader mechanistic profiles than other molecular categories, although the strength and extent of evidence vary across proteins and cancer types. Taken together, the proposed CSM-protein pan-cancer chemoresistance framework offers a biologically and therapeutically relevant regulatory network for understanding the mechanisms underlying cancer chemoresistance based predominantly on preclinical evidence. Our findings may provide a preclinical conceptual foundation for the development of combinatorial therapeutic strategies targeting cancer stemness and chemoresistance through the CSM-circRNA-CSM-protein regulatory axis.