Clonality analysis of multiple hepatocellular carcinomas by loss of heterozygosity pattern determined by chromosomes 16q and 13q.

BACKGROUND AND AIM

Loss of heterozygosity (LOH) on chromosomes 16q and 13q, associated with tumor development, is frequently found in hepatocellular carcinoma (HCC). In light of this, an attempt was made to use the LOH pattern determined by microsatellite markers on 16q and 13q to discriminate clonality.

METHODS

In an effort to locate the LOH region more precisely and select the appropriate markers, LOH studies on 88 HCC using a panel of 35 microsatellite markers on 16q were carried out. Nine independent regions of frequent LOH were defined. In combination with a previous study of deletion mapping of 13q by the same authors, 12 markers on 16q and 13q were selected and polymerase chain reaction amplification, from microdissection-extracted DNA, was used to allelotype microsatellite polymorphism as an indication of clonality.

RESULTS

Two patterns of LOH were observed. In pattern A, in 8 of 16 (50%) patients, the LOH pattern of the first tumor was preserved in the second sample, with some tumors also showing additional LOH. In these patients, the original and second tumors are presumed to arise from the same original clone with or without progressive accumulation of LOH. In pattern B (8 of 16, 50%), LOH seen in the first tumor was not preserved in the second or recurrent tumors, as evidenced by retention of heterozygosity compared with the first tumor.

CONCLUSION

The data suggest that the second tumor might have arisen from another independent clone. Moreover, this approach also provides a more sensitive and specific strategy to determine whether multiple or recurrent tumors are derived from the same or a different clone.