Ross J A, Schmidt P T, Perentesis J P, Davies S M
Department of Pediatrics, University of Minnesota, Minneapolis 55455, USA.
Cancer. 1999 Mar 15;85(6):1389-94.
Insulin-like growth factor-2 (IGF2) and H19 are reciprocally imprinted genes on chromosome 11; IGF2 is expressed paternally and H19 is expressed maternally. Loss of imprinting (LOI) at both H19 and IGF2 has been reported in seven fully informative adult testicular germ cell tumors (GCTs) and may contribute to germ cell carcinogenesis.
Genomic DNA from 61 pediatric GCTs was amplified by polymerase chain reaction (PCR) and screened for heterozygosity at both IGF2 and H19 using either ApaI or RsaI, respectively. If heterozygous, polyadenylated RNA was isolated and reversed-transcribed into cDNA. cDNA then was amplified by PCR and the products were digested with restriction enzymes to evaluate GCT expression of IGF2 and H19.
Eleven pediatric GCTs were fully informative for H19 and IGF2, including 5 ovarian GCTs, 2 testicular GCTs, and 4 extragonadal GCTs. Consistent with prior studies, both testicular GCTs showed LOI at both H19 and IGF2. In contrast, three of the five ovarian GCTs had LOI at both IGF2 and H19; one had LOI at IGF2 only, and one retained imprinting at both loci. Only one of the four extragonadal GCTs had LOI at IGF2 whereas three of the four had LOI at H19.
These data suggest that LOI at H19 and IGF2 also may be common in pediatric testicular GCTs. However, ovarian and extragonadal pediatric GCTs showed variable patterns of LOI that may indicate differences in the timing of carcinogenesis in germ cells at these sites.
胰岛素样生长因子2（IGF2）和H19是位于11号染色体上的相互印记基因；IGF2由父系表达，H19由母系表达。据报道，在7例信息完全明确的成人睾丸生殖细胞肿瘤（GCTs）中，H19和IGF2均发生了印记丢失（LOI），这可能与生殖细胞癌变有关。
采用聚合酶链反应（PCR）扩增61例儿童GCTs的基因组DNA，分别使用ApaI或RsaI筛选IGF2和H19的杂合性。如果是杂合子，则分离多聚腺苷酸化RNA并逆转录为cDNA。然后通过PCR扩增cDNA，并用限制性内切酶消化产物，以评估GCTs中IGF2和H19的表达。
11例儿童GCTs的H19和IGF2信息完全明确，包括5例卵巢GCTs、2例睾丸GCTs和4例性腺外GCTs。与先前的研究一致，2例睾丸GCTs的H19和IGF2均显示印记丢失。相比之下，5例卵巢GCTs中有3例的IGF2和H19均发生印记丢失；1例仅IGF2发生印记丢失，1例在两个位点均保留印记。4例性腺外GCTs中只有1例IGF2发生印记丢失，而4例中有3例H19发生印记丢失。
这些数据表明，H19和IGF2的印记丢失在儿童睾丸GCTs中也可能很常见。然而，卵巢和性腺外儿童GCTs显示出不同的印记丢失模式，这可能表明这些部位生殖细胞癌变时间的差异。
