B7-H6/NKp30 Axis in Melanoma: Translational Rationale, Evidence Gaps, and Therapeutic Considerations

Melanoma treatment has been transformed by immune checkpoint blockade, yet many patients still experience primary resistance, limited durability of response, or acquired resistance. These limitations underscore the need for additional targets that reflect melanoma biology while enabling new therapeutic strategies, particularly in biologically defined settings of immune escape such as checkpoint-resistant, HLA-low, dedifferentiated, or stress-adapted melanoma. The B7-H6/NKp30 axis has gained attention as a link between tumor cell stress, immune recognition, and therapy-related adaptation. B7-H6 (NCR3LG1), an inducible ligand for NKp30, has been detected in melanoma cell lines and tumor specimens, and soluble B7-H6 has been identified in a subset of patients. Membrane-bound B7-H6 may support NK-cell activation, whereas ligand shedding and accumulation of soluble B7-H6 may reduce effective antitumor recognition and promote immune evasion. Emerging evidence further suggests that B7-H6 expression may be linked to tumor-intrinsic programs relevant to melanoma cell survival, migration, and adaptation to therapeutic stress. However, B7-H6 is not yet a validated predictive biomarker or an established therapeutic target in melanoma, and current evidence remains limited by small melanoma-specific datasets, incomplete information on spatial and temporal heterogeneity, and the absence of melanoma-focused clinical validation. In this review, we examine the role of the B7-H6/NKp30 axis in immune surveillance, tumor escape, biomarker development, and therapeutic targeting, and discuss its translational potential in melanoma as an emerging but incompletely validated pathway that warrants focused investigation in melanoma states where conventional immune control is limited.