Frequent methylation of p16INK4A/p14ARF promoters in tumorigenesis of Epstein-Barr virus transformed lymphoblastoid cell lines.

BACKGROUND

The data that the p16INK4A gene is frequently inactivated in Burkitt lymphoma (BL) and that this event often accompanies the inactivation of p14ARF in several tumours prompted us to examine the genetic and methylation status of both genes in BL and B-lymphoblastoid cell lines (LCLs).

MATERIALS AND

METHODS

The existence of gene deletion, mutation and promoter methylation was investigated by single-strand conformational polymorphism, direct sequencing and methylation-specific PCR (MSP) analysis, respectively.

RESULTS

Sequencing of each exon of both tumour suppressor genes revealed p16INK4A mutation only in 3 out of 11 BL, but 1 of them also affected the p14ARF gene. MSP analysis of promoters showed p16INK4A to be methylated and p14ARF not to be methylated in each Epstein-Barr virus-positive BL cell line. Primary B-cells and de novo established LCLs had no genetic changes or methylated promoter of either gene. LCLs achieving the stage of immortalization usually showed methylation of both p16INK4A and p14ARF promoters.

CONCLUSION

Our results suggest that, in contrast to p161NK4A, inactivation of p14ARF by either genetic change or promoter methylation has no importance in the development of BL cell lines, while its methylation has a central role in the immortalization of LCLs.