Loss of Imprinting of Insulin-Like Growth Factor 2 is Associated with Increased Risk of Primary Lung Cancer in the Central China Region

Background: To determine the imprinting status of the IGF2 in Chinese patients with primary lung cancerand to analyze the clinical significance of the loss of imprinting (LOI) of IGF2. Materials and
Methods: PCRRFLPand RT-PCR-RFLP were carried out to select heterozygous cases for the ApaI polymorphism within exon9 of the IGF2 gene and further analyze IGF2 LOI in 64 lung cancer patients, respectively.
Results: Of 64 lungcancer patients, 31 were heterozygous for IGF2. The positive rates of IGF2 LOI of lung cancer foci, matchedparacancer tissues, and normal lung tissues were 77.4% (24/31), 61.3% (19/31), and 29.0% (9/31), respectively.The LOI differences for IGF2 among the three groups were statistically significant (χ2=15.267, p=0.000), andthe LOI frequency of IGF2 in normal lung tissue was significantly lower than that in lung cancer foci andparacancer tissues (χ2=14.577, p=0.000; χ2=6.513, p=0.011). No statistical difference was observed between thelung tumor group and the matched paracancer group (χ2=1.897, p=0.168). The prevalence of advanced clinicalstages (χ2=2.379; p=0.017) and lymph node metastasis (χ2=5.552; p=0.018) was significantly higher for LOIpositiveparacancer tissues than for LOI-negative paracancer tissues.
Conclusions: IGF2 LOI is highly frequentin Chinese primary lung cancer patients, especially those with increased risk of lymph node metastasis andadvanced clinical stages. IGF2 LOI may be an early epigenetic event in human lung carcinogenesis.