Department of Physiology and Biophysics, University of Louisville, 505 South Hancock Street, CTRB 322, Louisville, KY 40202, USA.
BMC Cancer. 2012 Nov 20;12:532. doi: 10.1186/1471-2407-12-532.
Pituitary tumor-transforming gene (PTTG) is an oncogene that is overexpressed in variety of tumors and exhibits characteristics of a transforming gene. Previous transgenic mouse models to access the tumorigenic potential in the pituitary and ovary have resulted in dysplasia without formation of visible tumors, possibly due to the insufficient expression of PTTG. PTTG expression level is critical for ovarian tumorigenesis in a xenograft model. Therefore, the tumorigenic function of PTTG in vivo remains unclear. We generated a transgenic mouse that overexpresses PTTG driven by the CMV promoter to determine whether PTTG functions as a transforming oncogene that is capable of initiating tumorigenesis.
Transgenic animals were generated by microinjection of PTTG transgene into the male pronucleus of FVB 0.5 day old embryos. Expression levels of PTTG in tissues of transgenic animals were analyzed using an immunohistochemical analysis. H&E staining and immunohistostaining were performed to examine the type of tumor in transgenic and PTTG transgenic/p53+/- animals.
PTTG transgenic offspring (TgPTTG) were monitored for tumor development at various ages. H&E analysis was performed to identify the presence of cancer and hyperplastic conditions verified with the proliferation marker PCNA and the microvessel marker CD31. Immunohistochemistry was performed to determine transgene expression, revealing localization to the epithelium of the fallopian tube, with more generalized expression in the liver, lung, kidney, and spleen. At eight months of age, 2 out of 15 TgPTTG developed ovarian cancer, 2 out of 15 developed benign tumors, 2 out of 15 developed cervical dysplasia, and 3 out of 15 developed adenomyosis of the uterus. At ten months of age, 2 out of 10 TgPTTG developed adenocarcinoma of the ovary, 1 out of 10 developed a papillary serous adenocarcinoma, and 2 out of 10 presented with atypia of ovarian epithelial cells. Tumorigenesis is a multi-step process, often requiring multiple oncogenes and/or inactivation of tumor suppressor genes. Therefore, to understand the contribution of p53 to PTTG induced tumorigenesis, we crossbred TgPTTG to p53+/- mice and maintained those 8 to 10 months. TgPTTG/p53+/- animals developed sarcomas faster than p53+/- alone as well as different tumor types in addition to cervical carcinomas in situ in 10 out of 17 females.
We conclude that while PTTG is a functional transforming oncogene, it requires an additional partner to effectively promote tumorigenesis through the loss of p53 include or between function or modulation.
垂体肿瘤转化基因（PTTG）是一种在多种肿瘤中过度表达的癌基因，具有转化基因的特征。以前的转基因小鼠模型旨在研究垂体和卵巢中的致瘤潜能，但只导致了发育不良而没有形成可见的肿瘤，这可能是由于 PTTG 的表达不足。PTTG 的表达水平对异种移植模型中的卵巢肿瘤发生至关重要。因此，PTTG 在体内的致瘤功能仍不清楚。我们生成了一种过表达 PTTG 的转基因小鼠，该 PTTG 由 CMV 启动子驱动，以确定 PTTG 是否作为能够引发肿瘤发生的转化致癌基因发挥作用。
通过将 PTTG 转基因体微注射到 FVB 0.5 天龄胚胎的雄性原核中，生成转基因动物。使用免疫组织化学分析来分析转基因动物组织中的 PTTG 表达水平。对转基因和 PTTG 转基因/p53+/-动物进行 H&E 染色和免疫组织化学染色，以检查肿瘤类型。
监测各种年龄的 PTTG 转基因后代（TgPTTG）的肿瘤发展情况。进行 H&E 分析以确定癌症的存在，并通过增殖标志物 PCNA 和微血管标志物 CD31 验证增生情况。进行免疫组织化学分析以确定转基因表达，显示定位于输卵管的上皮，在肝脏、肺、肾脏和脾脏中有更广泛的表达。在 8 个月大时，15 只 TgPTTG 中有 2 只发展为卵巢癌，2 只发展为良性肿瘤，2 只发展为宫颈发育不良，3 只发展为子宫腺肌病。在 10 个月大时，10 只 TgPTTG 中有 2 只发展为卵巢腺癌，1 只发展为乳头状浆液性腺癌，2 只发展为卵巢上皮细胞异型性。肿瘤发生是一个多步骤的过程，通常需要多个癌基因和/或肿瘤抑制基因失活。因此，为了了解 p53 对 PTTG 诱导的肿瘤发生的贡献，我们将 TgPTTG 与 p53+/- 小鼠杂交，并将这些小鼠维持 8 至 10 个月。与 p53+/- 单独相比，TgPTTG/p53+/- 动物的肉瘤发展更快，除了 17 只雌性中有 10 只患有原位宫颈癌外，还出现了不同类型的肿瘤。
我们得出结论，虽然 PTTG 是一种功能性转化致癌基因，但它需要额外的合作伙伴，通过缺失 p53 或功能失活或调节，才能有效地促进肿瘤发生。
