Filtz Emma A, Emery Ann, Lu Huarui, Forster Colleen L, Karasch Chris, Hallstrom Timothy C
Department of Pediatrics, University of Minnesota, Minneapolis, MN, United States of America.
Diagnostic and Biological Sciences, School of Dentistry, University of Minnesota, Minneapolis, MN, United States of America.
PLoS One. 2015 Aug 28;10(8):e0136729. doi: 10.1371/journal.pone.0136729. eCollection 2015.
The Rb and Pten tumor suppressor genes are important regulators of bone development and both are frequently mutated in the bone cancer osteosarcoma (OS). To determine if Rb1 and Pten synergize as tumor suppressor genes for osteosarcoma, we co-deleted them in osteoprogenitor cells. Surprisingly, we observed rapid development of adipogenic but not osteosarcoma tumors in the ΔRb1/Pten mice. ΔPten solo deleted mice also developed lipoma tumors but at a much reduced frequency and later onset than those co-deleted for Rb1. Pten deletion also led to a marked increase in adipocytes in the bone marrow. To better understand the function of Pten in bone development in vivo, we conditionally deleted Pten in OSX(+) osteoprogenitor cells using OSX-Cre mice. μCT analysis revealed a significant thickening of the calvaria and an increase in trabeculae volume and number in the femur, consistent with increased bone formation in these mice. To determine if Pten and Rb1 deletion actively promotes adipogenic differentiation, we isolated calvarial cells from Pten(fl/fl) and Pten(fl/fl); Rb1(fl/fl) mice, infected them with CRE or GFP expressing adenovirus, treated with differentiation media. We observed slightly increased adipogenic, and osteogenic differentiation in the ΔPten cells. Both phenotypes were greatly increased upon Rb1/Pten co-deletion. This was accompanied by an increase in expression of genes required for adipogenesis. These data indicate that Pten deletion in osteoblast precursors is sufficient to promote frequent adipogenic, but only rare osteogenic tumors. Rb1 hetero- or homo-zygous co-deletion greatly increases the incidence and the rapidity of onset of adipogenic tumors, again, with only rare osteosarcoma tumors.
视网膜母细胞瘤（Rb）和磷酸酶及张力蛋白同源物（Pten）肿瘤抑制基因是骨骼发育的重要调节因子，二者在骨癌骨肉瘤（OS）中均频繁发生突变。为了确定Rb1和Pten作为骨肉瘤肿瘤抑制基因是否具有协同作用，我们在骨祖细胞中共同敲除了它们。令人惊讶的是，我们在ΔRb1/Pten小鼠中观察到脂肪生成性肿瘤迅速发展，但未观察到骨肉瘤肿瘤。单独敲除Pten的小鼠也会发生脂肪瘤肿瘤，但频率比共同敲除Rb1的小鼠低得多，且发病时间更晚。敲除Pten还导致骨髓中脂肪细胞显著增加。为了更好地了解Pten在体内骨骼发育中的功能，我们使用OSX-Cre小鼠在OSX(+)骨祖细胞中条件性敲除Pten。微计算机断层扫描（μCT）分析显示，颅骨显著增厚，股骨小梁体积和数量增加，这与这些小鼠骨形成增加一致。为了确定敲除Pten和Rb1是否会积极促进脂肪生成分化，我们从Pten(fl/fl)和Pten(fl/fl);Rb1(fl/fl)小鼠中分离颅盖细胞，用表达CRE或绿色荧光蛋白（GFP）的腺病毒感染它们，并用分化培养基处理。我们观察到ΔPten细胞中脂肪生成和成骨分化略有增加。Rb1/Pten共同敲除后，这两种表型均显著增加。这伴随着脂肪生成所需基因表达的增加。这些数据表明，成骨细胞前体中Pten的缺失足以促进频繁的脂肪生成性肿瘤，但仅偶尔促进成骨性肿瘤。Rb1杂合或纯合共同敲除极大地增加了脂肪生成性肿瘤的发生率和发病速度，同样，骨肉瘤肿瘤也仅偶尔发生。
