[Further study on cyclin D1 expression and function in human nasopharyngeal carcinoma cell line]

In the present study, we tried to further elucidate the expression and function of cyclin D1 in human nasopharyngeal carcinoma (NPC) cell line.

Western blot was used in the analysis of D-type cyclin expression profile. The distribution of this protein was determined in the double parameter flow cytometry (FCM). The function of cyclin D1 in nasopharyngeal carcinoma cell line was determined in the antisense-oligonucleotied-cyclin D1 and antibody mediated knock-out experiments.

The immunoblot analysis of two NPC cell lines showed that the spectra of D-type in NPC cell lines founded their expressions in D1, D2, and D3. It also suggested that the overexpression of cyclin D1 could lead to deregulation of G1/S control. An additional double parameter FCM showed a characteristic variation in HNE1 which was consistent with the cell-cycle oscillation and the peak level expressed in G0/G1 phase and the lowest level in the S-phase. Two experimental approaches aimed at specific functional knock-out of cyclin D1 were employed; the cyclin D1-ASPODN experiment showed an inhibition of cyclin D1 expression at mRNA level and a down-regulated cyclin D1 partial inhibition of progression into S phase, resulting in cell growth arrest while the electroporation of neutralizing antibodies demonstrated a specific delay of S-phase entry in HNE1 and the requirement for the cyclin D1 in cell cycle progression of HNE1 cell line in regulation of G1/S.

These data reveal that the cell-cycle regulatory function of cyclin D1 is essential for cell cycle progression in the G1 of nasopharyngeal carcinoma cell line and suggest that cyclin D1 play an important role in NPC carcinogenesis.