Loss of heterozygosity of imprinted genes in SV40 t/T antigen-induced hepatocellular carcinomas.
Expression of the chromosomally linked Insulin-like Growth Factor II (IGF-II) and H19 genes is regulated by parental imprinting during development, since the maternally inherited IGF-II and the paternally inherited H19 alleles are inactive in fetal tissues. Here we show that expression of IGF-II and H19 genes is activated in transgenic mice during SV40 Tag-induced hepatocarcinogenesis and that imprinting of both genes is conserved in the liver tumors. Allelic imbalances of IGF-II and H19 genes and other chromosome 7 markers were detected in one third (13/39) of the hepatocellular carcinomas analysed. A strong bias on the allele retained in the neoplasms was observed, since underrepresentation or complete loss of maternal chromosome 7 was recognised in 12/13 cases. High levels of IGF-II mRNA were expressed by all carcinomas with relative excess of paternal chromosome 7 alleles and suppressed H19 expression was found in the neoplasms lacking the maternal alleles. Overall the results indicate that expression of imprinted genes is involved in progression of experimental liver tumors and suggest that the murine chromosome 7, whose loss may possibly cause the inactivation of a growth-inhibitory gene, is preferentially retained as paternal copy in the liver tumors because of parental imprinting of IGF-II gene.
Casola
S
S
Centro di Endocrinologia ed Oncologia Sperimentale, CNR, Naples, Italy.
Ungaro
P
P
Pedone
P V
PV
Lazzaro
D
D
Fattori
E
E
Ciliberto
G
G
Zarrilli
R
R
Bruni
C B
CB
Riccio
A
A
D000483:Alleles; D000818:Animals; D000952:Antigens, Polyomavirus Transforming / Q000235:genetics*; D001483:Base Sequence; D002872:Chromosome Deletion; D002874:Chromosome Mapping; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D005260:Female; D005333:Fetus; D017353:Gene Deletion; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D005819:Genetic Markers; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis / Q000235:genetics*; D054461:Lim Kinases; D008114:Liver Neoplasms, Experimental / Q000235:genetics*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics*; D013539:Simian virus 40 / Q000235:genetics*
D000952:Antigens, Polyomavirus Transforming; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005819:Genetic Markers; D007335:Insulin-Like Growth Factor II; D011494:Protein Kinases; D054461:Lim Kinases; C515893:Limk1 protein, mouse; C095325:Limk2 protein, mouse; D017346:Protein Serine-Threonine Kinases