ANALYSIS OF A PROTEIN-KINASE C-ALPHA MUTATION IN HUMAN PITUITARY-TUMORS

It is generally accepted that protein kinase C-alpha (PKC-alpha) is an important enzyme in the cellular regulation of growth and differentia tion by phosphorylating proteins. Recent studies have described a poin t mutation of PKC-alpha (position 908 of the genetic sequence, codon G AC becoming GGC) in invasive human pituitary rumours which leads to an exchange of amino acids in the protein. We investigated 11 human pitu itary rumours to evaluate the data obtained previously. cDNA was subcl oned and up to ten individual clones were sequenced from each tumour, resulting in 85 clones analyzed in total. All of the pituitary adenoma s showed a normal wild-type sequence of PKC-alpha DNA. Even if the tum our was 'invasive' (infiltration of the dura mater) no mutation at pos ition 908 of the sequence was found. Moreover, using Western blot anal yses we did not observe any differences in PKC-alpha protein expressio n in invasive as compared with noninvasive pituitary adenomas. Until n ow we have been unable to confirm the data of other investigators, sug gesting that mutated PKC-alpha is an inconsistent feature of invasive pituitary tumours.