Expression of the proenkephalin gene in human neuroblastoma cell lines

Several human tumour cell lines were screened for secretion of proenkephalin-derived peptides with an antiserum directed to its N-terminus, Met-enkephalin-Arg6,Phe7 and for proopiomelanocortin-derived peptides with an antiserum to beta-endorphin. The neuroblastoma SK-N-MC cell line secreted Met-enkephalin-Arg6,Phe7-immunoreactive peptides in relatively high amounts into the culture medium, although processing was not complete and there was no evidence for free Met-enkephalin-Arg6,Phe7. Gene expression was confirmed by the presence of proenkephalin mRNA and proenkephalin-derived polypeptides in extracts of the SK-N-MC cells and also in the neuroblastoma SH-SY5Y cell line. In the latter cells, however, the expression was approximately 3 times lower, there was less processing of proenkephalin and no evidence for secretion.