Calcium/Calmodulin-dependent protein kinase II and its endogenous inhibitor α in medullary thyroid cancer.
OBJECTIVE
Calcium/calmodulin-dependent kinase II (CaMKII) is involved in the regulation of cell proliferation. Its endogenous inhibitor (hCaKIINα) is expressed in some cell types. We determined the role of CaMKII in RET-stimulated proliferation and hCaMKIINα in medullary thyroid carcinoma (MTC).


METHODS
We analyzed the role of RET mutants on CaMKII activation in NIH3T3 and in MTC cell lines, and determined the effect of CaMKII inhibition on RET/ERK pathway and cell proliferation. Then the expression of hCaKIINα mRNA was determined by real-time PCR in primary MTC and it was correlated with some clinicopathologic parameters.


RESULTS
RET(C634Y) and RET(M918T) mutants expressed in NIH3T3 cells induced CaMKII activation. CaMKII was activated in unstimulated MTC cells carrying the same RET mutants and it was inhibited by RET inhibition. Inhibition of CaMKII in these cells induced a reduction of Raf-1, MEK, and ERK phosphorylation, cyclin D expression, and cell proliferation. hCaKIINα mRNA expression in primary MTC was very variable and did not correlate with gender and age at diagnosis. Serum calcitonin, (R(2) = 0.032; P = 0.017), tumor volume (P = 0.0079), lymph node metastasis (P = 0.033), and staging (P = 0.0652) were negatively correlated with the hCaKIINα mRNA expression.


CONCLUSIONS
CaMKII is activated by RET mutants and is activated at baseline in MTC cells where it mediates the oncogenic pathway leading to cell proliferation. The mRNA expression of its endogenous inhibitor hCaKIINα inversely correlates with the severity of MTC. CaMKII might represent a new target for MTC therapy and hCaKIINα is a marker of disease extension.
Authors' Affiliations: Dipartimento di Medicina Molecolare e Biotecnologie Mediche, Istituto di Endocrinologia e Oncologia Sperimentale del CNR Naples; Department of Neuroscience, Reproductive and Odontostomatological Sciences, University of Naples "Federico II", Naples; Department of Medicine-DIMED, Unit of Endocrinology, University of Padua, Padova; and Department of Medicine and Surgery, University of Salerno, Salerno, Italy.
Eleonora
E
Russo
Marcella
M
Salzano
Valentina
V
De Falco
Caterina
C
Mian
Susi
S
Barollo
Agnese
A
Secondo
Maurizio
M
Bifulco
Mario
M
Vitale
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D015153:Blotting, Western; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism*; D018278:Carcinoma, Neuroendocrine; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D009154:Mutation; D041681:NIH 3T3 Cells; D011506:Proteins / Q000378:metabolism*; D051096:Proto-Oncogene Proteins c-ret / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology*; D013964:Thyroid Neoplasms / Q000201:enzymology*
C529569:CAMK2N1 protein, human; D011506:Proteins; D051096:Proto-Oncogene Proteins c-ret; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2