Title : Discovery of an R-spondin–ALK–Wnt axis: Expanding the oncogenic landscape of anaplastic lymphoma kinase
Abstract:
Anaplastic lymphoma kinase (ALK), a receptor tyrosine kinase, has emerged as a critical driver of malignancy in diverse cancers such as anaplastic large cell lymphoma, non-small cell lung cancer, and neuroblastoma. Although ALK is normally activated by its ligands ALKAL1 and ALKAL2, cancer cells frequently exploit ligand-independent mechanisms, most notably by forming oncogenic fusions with other proteins that preserve the kinase activity of ALK. Aberrant ALK signaling stimulates well-characterized signaling cascades including Ras/Raf/MEK/ERK, JAK/STAT3, and PI3K/AKT. More recently, evidence has hinted at a possible connection between ALK and the Wnt pathway, though the molecular basis remains unclear. To study the role of ALK in modulating Wnt signaling, we employed a network-driven gene association approach with GeneMANIA, which identified R-spondins, the known amplifiers of Wnt signaling, as a putative ALK partners. Protein–protein interaction analysis predicted that R-spondins engage the TNF-like and EGF-like domains of ALK, analogous to the known ALKAL2 recognition regions. Docking and molecular dynamics simulations further supported the stable and energetically favourable binding of these complexes. We validated our in-silico results in neuroblastoma cell lines IMR32 and SH-SY5Y where full-length ALK is implicated in carcinogenesis. The results showed that when these cells are treated with a combination of Wnt3a and Rspo2, the Wnt pathway activity was enhanced. However, upon inhibition of ALK, the Wnt signaling activity reduced markedly. Our findings indicate the existence of R-spondin-ALK-Wnt signaling axis as an alternate to the already known Rspondin-LGR-Wnt signaling. This crosstalk broadens the biological scope of ALK beyond its canonical oncogenic role and suggests opportunities for therapeutic strategies that co-target ALK and Wnt signaling in ALK-driven tumors.
