Another issue to be addressed is the putative relationship between parent HN and tumorigenesis/metastasis in various types of cancer, which is inconclusive at present [42]; interestingly, the discrepancies between different relevant reports have been attributed, among other factors, to the use of different peptides, e.g., HNG vs. parent HN, since specific HN analogues might interact differently with the receptors present in tumor cells [78]. Here, NRGN is linked to neoplasm.