Different expression of protein kinase A (PKA) regulatory subunits in cortisol-secreting adrenocortical tumors: relationship with cell proliferation.
The four regulatory subunits (R1A, R1B, R2A, R2B) of protein kinase A (PKA) are differentially expressed in several cancer cell lines and exert distinct roles in growth control. Mutations of the R1A gene have been found in patients with Carney complex and in a minority of sporadic primary pigmented nodular adrenocortical disease (PPNAD). The aim of this study was to evaluate the expression of PKA regulatory subunits in non-PPNAD adrenocortical tumors causing ACTH-independent Cushing's syndrome and to test the impact of differential expression of these subunits on cell growth. Immunohistochemistry demonstrated a defective expression of R2B in all cortisol-secreting adenomas (n=16) compared with the normal counterpart, while both R1A and R2A were expressed at high levels in the same tissues. Conversely, carcinomas (n=5) showed high levels of all subunits. Sequencing of R1A and R2B genes revealed a wild type sequence in all tissues. The effect of R1/R2 ratio on proliferation was assessed in mouse adrenocortical Y-1 cells. The R2-selective cAMP analogue 8-Cl-cAMP dose-dependently inhibited Y-1 cell proliferation and induced apoptosis, while the R1-selective cAMP analogue 8-HA-cAMP stimulated cell proliferation. Finally, R2B gene silencing induced up-regulation of R1A protein, associated with an increase in cell proliferation. In conclusion, we propose that a high R1/R2 ratio favors the proliferation of well differentiated and hormone producing adrenocortical cells, while unbalanced expression of these subunits is not required for malignant transformation.
Mantovani
G
G
Department of Medical Sciences, University of Milan, Fondazione Policlinico IRCCS, Milan, Italy.
Lania
A G
AG
Bondioni
S
S
Peverelli
E
E
Pedroni
C
C
Ferrero
S
S
Pellegrini
C
C
Vicentini
L
L
Arnaldi
G
G
Bosari
S
S
Beck-Peccoz
P
P
Spada
A
A
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000306:Adrenal Cortex Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D018246:Adrenocortical Adenoma / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence / Q000235:genetics; D002277:Carcinoma / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit / Q000235:genetics / Q000378:metabolism; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015971:Gene Expression Regulation, Enzymologic / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000235:genetics; D020868:Gene Silencing / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D015854:Up-Regulation / Q000235:genetics
D054757:Cyclic AMP-Dependent Protein Kinase RIIbeta Subunit; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D015124:8-Bromo Cyclic Adenosine Monophosphate; C044258:8-chloro-cyclic adenosine monophosphate; D017868:Cyclic AMP-Dependent Protein Kinases; D006854:Hydrocortisone