Interleukin-1 alpha regulates G(1) cell cycle progression and arrest in thyroid carcinoma cell lines NIM1 and NPA

This study provides the first report that the same cytokine (interleukin-1 (IL-1)) can induce opposite effects on cyclin-dependent kinases (Cdks) and Cdk inhibitors (Cd-kis) in the G(1) phase even in the same type of cancer c ells (papillary thyroid carcinoma cells). Cell cycle analysis revealed an i ncrease in NIM1 cells and a decrease in NPA cells in the S and G(2)+M phase s after treatment with IL-1 alpha. The addition of IL-1 alpha to NIM1 cells reduced the expression of p16 and p21 protein and induced the expression o f Cdk2 and Cdk4 protein, which leads to the phosphorylation of retinoblasto ma protein. The addition of IL-1 alpha to NPA cells induced the expression of p27 protein and reduced the expression of Cdk2 protein, which leads to i nduction of p107 protein expression. It is of interest that p21 protein exp ression was not observed in NPA cells. These results suggest that several C dks and Cdkis play a regulatory role in the G(1) cell cycle progression and arrest induced by IL-1 alpha in thyroid carcinoma cell lines.