Unresolved questions on the GADD45GIP1-RPL35 axis in osteosarcoma: mechanistic links to ER stress and therapeutic targeting.

In their recent study, Li et al. (2025) propose a novel signaling axis in which GADD45GIP1 promotes osteosarcoma progression by stabilizing RPL35, thereby alleviating endoplasmic reticulum (ER) stress through the PERK/eIF2α pathway. While this work identifies a potentially significant oncogenic mechanism, our analysis highlights several critical aspects that require further elucidation. The central claim-that stabilization of a single ribosomal protein, RPL35, directly and specifically alleviates ER stress-presents a conceptual paradox, as enhanced ribosome biogenesis would typically be expected to increase the proteotoxic load. We explore alternative explanations, including the potential for selective mRNA translation or non-ribosomal functions of RPL35. Furthermore, the therapeutic promise of targeting this pathway is tempered by the challenges of inhibiting protein-protein interactions and the risk of on-target toxicity given the pervasive role of the PERK pathway in normal secretory cells. The model also necessitates validation across the spectrum of osteosarcoma's genetic heterogeneity. This letter critically examines these mechanistic ambiguities and proposes essential experiments to validate the model, assess its therapeutic viability, and define its clinical relevance within the complex landscape of osteosarcoma biology.