PRKAR1A and neoplasm: In addition, it was shown that RIα, the most abundant regulatory subunit of cAMP-dependent PKA [91], in thyroid cells, possibly exhibits a tumor-suppressor function, as indicated by decreased expression of the RIα subunit in carcinomas and by the losses of PRKAR1A 17q22–24 locus in about 50% of all informative cancers.