A bittersweet symphony: soluble mediator networks orchestrate melanoma plasticity and therapeutic adaptation.

Melanoma progression and therapeutic resistance are increasingly recognized as emergent properties of the dynamic interactions between tumor cells and their surrounding tumor microenvironment (TME). A central feature of this adaptability is melanoma cell plasticity, through which tumor cells reversibly transition between distinct transcriptional and functional states in response to microenvironmental and therapeutic pressures. Recent advances in single-cell RNA sequencing and spatial transcriptomics have revealed that these interactions are spatially organized, with distinct cellular compositions and signaling programs forming specialized microenvironmental niches. However, the mechanisms that coordinate these spatially and functionally heterogeneous states remain incompletely integrated. In this review, we propose that soluble mediator networks, including cytokines, chemokines, growth factors, metabolites, extracellular vesicle-associated signals, and stress-related mediators, provide a functional layer that links the different compartments of the melanoma TME. We organize this network into interconnected immunoregulatory, vascular and lymphatic, mechanotransductive/ECM, and metabolic/redox axes, and examine how their reciprocal interactions influence melanoma cell identity, immune surveillance, vascular function, tissue architecture, and metabolic adaptation. Particular attention is given to the context-dependent activity of soluble mediators, whose effects vary according to their cellular source, spatial distribution, disease stage, and therapeutic pressure. We further discuss how these signals converge within localized microenvironmental niches to promote melanoma plasticity, immune escape, metastatic dissemination, and therapeutic resistance. Emerging mechanisms, including metabolic rewiring, lactate signaling, oxidative stress, and transmissible endoplasmic reticulum stress, illustrate how adaptive information can propagate between the different compartments. Overall, we propose that therapeutic resistance should not be viewed solely as the consequence of tumor-intrinsic alterations or isolated resistance pathways, but as an emergent property of a continuously rewired tumor ecosystem. This perspective suggests that effective therapeutic strategies may require disruption of the adaptive communication networks that sustain resistant tumor states, rather than targeting individual molecular pathways in isolation.