DUSP29 does not regulate melanoma–myoblast interactions in a skeletal muscle co-culture model

Skeletal muscle, despite constituting nearly half of human body mass, is rarely affected by metastatic spread. The biological mechanisms underlying this relative resistance remain poorly understood. Dual-specificity phosphatases (DUSPs) have emerged as important regulators in tumor biology; however, the role of DUSP29 (also known as DUPD1), a phosphatase highly enriched in skeletal muscle, remains uninvestigated in the context of tumor-muscle interactions. We hypothesized that myoblasts may exert tumor-suppressive effects through muscle-specific signaling pathways and that DUSP29 could contribute to this interaction. A co-culture model of murine myoblasts (C2C12) and melanoma cells (B16F10) was established to evaluate tumor-muscle interactions under direct-contact and paracrine conditions. DUSP29 expression in myoblasts was selectively silenced using small interfering RNA (siRNA). Tumor cell responses were assessed by measuring cell viability and apoptosis across multiple co-culture ratios and time points using MTT assays and flow cytometry. Co-culture with myoblasts did not significantly alter melanoma cell viability or apoptosis compared with monoculture controls. Similarly, siRNA-mediated knockdown of DUSP29 in myoblasts did not affect tumor cell viability under co-culture conditions. Transfection reagents and control siRNAs alone showed no cytotoxic effects, confirming that the observed outcomes were not attributable to experimental artifacts. Under the experimental conditions tested, skeletal muscle myoblasts do not exert direct tumor-suppressive effects on melanoma cells, and inhibition of the muscle-enriched phosphatase DUSP29 is insufficient to modify tumor cell behavior. Although negative, these findings provide valuable quantitative insights into tumor-muscle interactions and suggest that skeletal muscle resistance to metastatic colonization is likely mediated by mechanisms beyond direct myoblast-tumor cross-talk or DUSP29-dependent signaling.