Considering the separation of NLRR1-rich and ALK-rich cancer cell clusters in human NB tissue specimens, the intracellular short tail of NLRR1, and the proteolytic cleavage of NLRR3 at the transmembrane region40, we hypothesised that NLRR1 should also act as a soluble form of the extracellular domain after cleavage. Here, ALK is linked to cancer.