Instituto de Biomedicina de Sevilla, IBIS, Hospital Universitario Virgen del Rocio, Consejo Superior de Investigaciones Científicas, Universidad de Sevilla, Avda. Manuel Siurot s/n, 41013 Seville, Spain.
CIBERONC, Instituto de Salud Carlos III, 28029 Madrid, Spain.
Theranostics. 2021 Jan 19;11(7):3452-3471. doi: 10.7150/thno.53572. eCollection 2021.
SPINOPHILIN (SPN, PPP1R9B) is an important tumor suppressor involved in the progression and malignancy of different tumors depending on its association with protein phosphatase 1 (PP1) and the ability of the PP1-SPN holoenzyme to dephosphorylate retinoblastoma (pRB). We performed a mutational analysis of SPN in human tumors, focusing on the region of interaction with PP1 and pRB. We explored the effect of the SPN-A566V mutation in an immortalized non-tumorigenic cell line of epithelial breast tissue, MCF10A, and in two different p53-mutated breast cancer cells lines, T47D and MDA-MB-468. We characterized an oncogenic mutation of SPN found in human tumor samples, SPN-A566V, that affects both the SPN-PP1 interaction and its phosphatase activity. The SPN-A566V mutation does not affect the interaction of the PP1-SPN holoenzyme with pocket proteins pRB, p107 and p130, but it affects its ability to dephosphorylate them during G0/G1 and G1, indicating that the PP1-SPN holoenzyme regulates cell cycle progression. SPN-A566V also promoted stemness, establishing a connection between the cell cycle and stem cell biology via pocket proteins and PP1-SPN regulation. However, only cells with both SPN-A566V and mutant p53 have increased tumorigenic and stemness properties. SPN-A566V, or other equivalent mutations, could be late events that promote tumor progression by increasing the CSC pool and, eventually, the malignant behavior of the tumor.
棘蛋白（SPN，PPP1R9B）是一种重要的肿瘤抑制因子，其在不同肿瘤中的进展和恶性程度取决于其与蛋白磷酸酶 1（PP1）的结合以及 PP1-SPN 全酶去磷酸化视网膜母细胞瘤（pRB）的能力。我们对人类肿瘤中的 SPN 进行了突变分析，重点关注与 PP1 和 pRB 相互作用的区域。我们探索了 SPN-A566V 突变在永生化非肿瘤上皮乳腺组织 MCF10A 细胞系和两种不同 p53 突变乳腺癌细胞系 T47D 和 MDA-MB-468 中的作用。我们鉴定了一种在人类肿瘤样本中发现的 SPN 致癌突变，SPN-A566V，它同时影响 SPN-PP1 相互作用及其磷酸酶活性。SPN-A566V 突变不影响 PP1-SPN 全酶与口袋蛋白 pRB、p107 和 p130 的相互作用，但影响其在 G0/G1 和 G1 期间去磷酸化它们的能力，表明 PP1-SPN 全酶调节细胞周期进程。SPN-A566V 还促进了干性，通过口袋蛋白和 PP1-SPN 调节建立了细胞周期与干细胞生物学之间的联系。然而，只有同时具有 SPN-A566V 和突变型 p53 的细胞才具有增加的致瘤性和干性特性。SPN-A566V 或其他等效突变可能是促进肿瘤进展的晚期事件，通过增加 CSC 池并最终增加肿瘤的恶性行为。
