■胰岛素样生长因子-1受体(IGF-1R)的过表达与细胞增殖增加有关,分化,改造,和致瘤性。此外,参与癌细胞对放射疗法的抗性的信号来自IGF-1R。目的探讨IGF-1系统在辐射反应中的作用,进一步评价其对DNA修复途径基因表达的影响。
■为了抑制IGF-1系统,我们稳定转染Caco-2细胞系以表达缺乏激酶的IGF-1R突变体。然后我们研究了这种突变对细胞生长的影响,对辐射的反应,和克隆生存,以及使用细胞活力测定法来检查DNA损伤和修复。最后,我们对γ-H2AX进行了免疫荧光,以检测双链DNA断裂,并使用实时PCR阵列评估了84个参与DNA修复的关键基因的表达.
■突变IGF-1R细胞表现出明显的生长和活力减弱,与野生型细胞相比,以及γ照射后克隆存活率降低。然而,突变的IGF-1R细胞在辐射诱导的DNA双链断裂的修复中没有显示任何明显的延迟。此外,突变IGF-1R的表达显着下调BRCA2的mRNA水平,BRCA2是参与同源重组DNA修复的主要蛋白。
■这些结果表明阻断IGF-1R介导的信号级联,通过表达缺乏激酶的IGF-1R突变体,减少细胞生长并使癌细胞对电离辐射敏感。因此,IGF-1R系统可能是增强放射敏感性和癌症治疗效果的潜在靶点.
UNASSIGNED: Overexpression of the insulin-like growth factor-1 receptor (IGF-1R) is associated with increased cell proliferation, differentiation, transformation, and tumorigenicity. Additionally, signaling involved in the resistance of cancer cells to radiotherapy originates from IGF-1R. The purpose of this
study was to investigate the role of the IGF-1 system in the radiation response and further evaluate its effect on the expression of DNA repair pathway genes.
UNASSIGNED: To inhibit the IGF-1 system, we stably transfected the Caco-2 cell line to express a kinase-deficient IGF-1R mutant. We then studied the effects of this mutation on cell growth, the response to radiation, and clonogenic survival, as well as using a cell viability assay to examine DNA damage and repair. Finally, we performed immunofluorescence for γ-H2AX to examine double-strand DNA breaks and evaluated the expression of 84 key genes involved in DNA repair with a real-time PCR array.
UNASSIGNED: Mutant IGF-1R cells exhibited significantly blunted cell growth and viability, compared to wild-type cells, as well as reduced clonogenic survival after γ-irradiation. However, mutant IGF-1R cells did not show any significant delays in the repair of radiation-induced DNA double-strand breaks. Furthermore, expression of mutant IGF-1R significantly down-regulated the mRNA levels of BRCA2, a major protein involved in homologous recombination DNA repair.
UNASSIGNED: These results indicate that blocking the IGF-1R-mediated signaling cascade, through the expression of a kinase-deficient IGF-1R mutant, reduces cell growth and sensitizes cancer cells to ionizing radiation. Therefore, the IGF-1R system could be a potential target to enhance radio-sensitivity and the efficacy of cancer treatments.