Study On Retrotransposition Of Alu Elements In Hepatocellular Carcinoma

Involvement of TEs (transposable elements) has been implicated in the triggering of cancer and cancer-related diseases in human and other mammals. As the most abundant repetitive elements among retroelements, Alus are presented in the human genome at about 1,000,000 copies and have a remarkable impact on genomic structure. It was estimated that there is one new Alu insert in approximately every 200 new birth. Human Genetic Mutation Database suggests that Alu elements contribute to about 0.1% of human genetic diseases.Conditions of genomic instability are thought to be necessary for carcino-genesis or cancer progression. Among the principal factors that cause genetic instability are mobile genetic elements or TEs. Genetic instability resulting fro-m Alus plays an important role in carcinogenesis, e.g. Alus mediated unequal recombination resulting in recurrence of chromosomal abnormalities in some cancers.In the present study, we are to investigate the relation of hepatocarcinom-a and Alu as retrotransposoable elements. Fist we employed two methods (in situ hybridization and primer extension analysis) to determine the level of Alu RNA in hepatocarcinoma against adjacent liver tissues. Results suggest that Pol III directed Alu transcript increases dramatically in hepatocellular carcinoma tissue other than normal liver tissue. And then, we determined the activity of RT (reverse transcriptase) in hepatocellular carcinoma and adjacent liver tissue. Results suggest that activity of RT was slightly higher in hepatocellular carcinoma.Although details are unclear, we may also give a sketch map for retrotra-nsposition of Alu elements in human genome: transcription of Alu directed by Pol III, reverse transcription with assistance of other retrotransposons andrandom insertion or specific sequence dependent insertion in human genome. It cannot be concluded that retrotransposition of Alu elements in hepatocellu-lar carcinoma is activated. However, that level of Alu RNA increases in hepat-ocellular carcinoma is verified and that reverse transcription of Alu RNA into cDNA is possible.