Expression of ret Proto‐oncogene in Human Neuroblastomas

We examined the expression of ret proto‐oncogene (proto‐ret) in surgically resected human neuroblastomas. Slot blot RNA hybridization revealed that all 29 neuroblastomas examined expressed the proto‐ret, the relative intensity of the hybridization ranging from 1 to 48. No correlation was found between the level of expression of proto‐ret and the clinical stage. The level of expression was also not correlated with N‐myc amplification, the patient's age or the histological type of the tumor. Based on the previous finding that proto‐ret expression is very rarely detected in tumor cell lines other than those of neuroblastoma, proto‐ret expression was suggested to be a characteristic of neuroblastomas, and possibly to be involved in the genesis of neuroblastomas.