MiR-221 controls CDKN1C/p57 and CDKN1B/p27 expression in human hepatocellular carcinoma.
The identification of target mRNAs is a key step for assessing the role of aberrantly expressed microRNAs in human cancer. MiR-221 is upregulated in human hepatocellular carcinoma (HCC) as well as in other malignancies. One proven target of miR-221 is CDKN1B/p27, whose downregulation affects HCC prognosis. Here, we proved that the cyclin-dependent kinase inhibitor (CDKI) CDKN1C/p57 is also a direct target of miR-221. Indeed, downregulation of both CDKN1B/p27 and CDKN1C/p57 occurs in response to miR-221 transfection into HCC-derived cells and a significant upregulation of both CDKN1B/p27 and CDKN1C/p57 occurs in response to antimiR-221 transfection. A direct interaction of miR-221 with a target site on the 3' UTR of CDKN1C/p57 mRNA was also demonstrated. By controlling these two CDKIs, upregulation of miR-221 can promote growth of HCC cells by increasing the number of cells in S-phase. To assess the relevance of these studies in primary tumors, matched HCC and cirrhosis samples were assayed for miR-221, for CDKN1B/p27 and CDKN1C/p57 expression. MiR-221 was upregulated in 71% of HCCs, whereas CDKN1B/p27 and CDKN1C/p57 proteins were downregulated in 77% of cases. A significant inverse correlation between miR-221 and both CDKN1B/p27 and CDKN1C/p57 was found in HCCs. In conclusion, we suggest that miR-221 has an oncogenic function in hepatocarcinogenesis by targeting CDKN1B/p27 and CDKN1C/p57, hence promoting proliferation by controlling cell-cycle inhibitors. These findings establish a basis toward the development of therapeutic strategies aimed at blocking miR-221 in HCC.
Fornari
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F
1Dipartimento di Medicina Interna e Gastroenterologia e Centro di Ricerca Biomedica Applicata, Università di Bologna, Policlinico S Orsola, Bologna, Italy.
Gramantieri
L
L
Ferracin
M
M
Veronese
A
A
Sabbioni
S
S
Calin
G A
GA
Grazi
G L
GL
Giovannini
C
C
Croce
C M
CM
Bolondi
L
L
Negrini
M
M
D020413:3' Untranslated Regions; D000368:Aged; D000369:Aged, 80 and over; D006528:Carcinoma, Hepatocellular / Q000378:metabolism* / Q000473:pathology; D002453:Cell Cycle; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D050760:Cyclin-Dependent Kinase Inhibitor p27; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000235:genetics*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D008113:Liver Neoplasms / Q000378:metabolism* / Q000473:pathology; D008297:Male; D035683:MicroRNAs / Q000502:physiology*; D008875:Middle Aged
D020413:3' Untranslated Regions; D050760:Cyclin-Dependent Kinase Inhibitor p27; D050761:Cyclin-Dependent Kinase Inhibitor p57; D047908:Intracellular Signaling Peptides and Proteins; D035683:MicroRNAs; C436291:CDKN1B protein, human; C493964:CDKN1C protein, human; C525709:MIR221, human