Df. Jarrard et al., REGIONAL LOSS OF IMPRINTING OF THE INSULIN-LIKE GROWTH-FACTOR-II GENEOCCURS IN HUMAN PROSTATE TISSUES, Clinical cancer research, 1(12), 1995, pp. 1471-1478
In most tissues, the insulin-like growth factor II gene (IGF-II) demon
strates imprinting, being expressed exclusively from the paternal alle
le, Recently, a loss of IGF-II imprinting (i.e., biallelic expression)
has been found in sporadic Wilm's tumors and lung carcinomas, and thi
s molecular event may contribute to the pathogenesis of these tumors,
Here, we report that in prostates removed at radical surgery for local
ized adenocarcinoma, both the cancer and the associated normal periphe
ral zone tissue have a pronounced biallelic expression of the IGF-II g
ene, However, this pattern of gene expression is uncommon in periureth
ral samples of benign prostatic hyperplasia (BPH) from the same specim
ens, We analyzed the status of genomic imprinting at the IGF-II locus
in prostate specimens removed for carcinoma using an ApaI polymorphism
in the 3' untranslated exon of the IGF-II gene, First-strand cDNA syn
thesis and subsequent PCR amplification were performed on 13 of 35 rad
ical prostatectomy specimens found to be informative for analysis of a
llele-specific expression, Biallelic expression for IGF-II RNA was dem
onstrated in 10 (83%) of 12 tumor samples and 8 (73%) of 11 matched pe
ripheral zone prostate samples but in only 2 (18%) of 11 BPH samples,
RNA transcripts were readily demonstrated by Northern blot analysis, a
nd differences in expression were not noted among normal, BPH, and tum
or prostate tissues, In situ hybridization revealed production of IGF-
II by both the epithelium and stroma, The finding of a frequent bialle
lic expression of IGF-II in peripheral prostate specimens suggests a r
egional pattern of IGF-II gene regulation exists in prostate tissue, W
e hypothesize that this tissue-specific pattern of gene expression may
participate in the marked predilection of peripheral prostatic tissue
for the development of carcinogenesis.