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Verdugo-Sivianes EM, Carnero A. SPINOPHILIN: a multiplayer tumor suppressor. Genes Dis 2022; 10:187-198. [PMID: 37013033 PMCID: PMC10066247 DOI: 10.1016/j.gendis.2021.12.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/24/2021] [Indexed: 02/07/2023] Open
Abstract
SPINOPHILIN (SPN, PPP1R9B or NEURABIN-2) is a multifunctional protein that regulates protein-protein interactions in different cell signaling pathways. SPN is also one of the regulatory subunits of protein phosphatase 1 (PP1), implicated in the dephosphorylation of retinoblastoma protein (pRB) during cell cycle. The SPN gene has been described as a tumor suppressor in different human tumor contexts, in which low levels of SPN are correlated with a higher grade and worse prognosis. In addition, mutations of the SPN protein have been reported in human tumors. Recently, an oncogenic mutation of SPN, A566V, was described, which affects both the SPN-PP1 interaction and the phosphatase activity of the holoenzyme, and promotes p53-dependent tumorigenesis by increasing the cancer stem cell (CSC) pool in breast tumors. Thus, the loss or mutation of SPN could be late events that promotes tumor progression by increasing the CSC pool and, eventually, the malignant behavior of the tumor.
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Verdugo-Sivianes EM, Carnero A. Role of the Holoenzyme PP1-SPN in the Dephosphorylation of the RB Family of Tumor Suppressors During Cell Cycle. Cancers (Basel) 2021; 13:cancers13092226. [PMID: 34066428 PMCID: PMC8124259 DOI: 10.3390/cancers13092226] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 04/29/2021] [Accepted: 05/03/2021] [Indexed: 11/16/2022] Open
Abstract
Simple Summary Cell cycle progression is highly regulated by modulating the phosphorylation status of retinoblastoma (RB) family proteins. This process is controlled by a balance in the action of kinases, such as the complexes formed by cyclin-dependent kinases (CDKs) and cyclins, and phosphatases, mainly the protein phosphatase 1 (PP1). However, while the phosphorylation of the RB family has been largely studied, its dephosphorylation is less known. Recently, the PP1-Spinophilin (SPN) holoenzyme has been described as the main phosphatase responsible for the dephosphorylation of RB proteins during the G0/G1 transition and at the end of G1. Here, we describe the regulation of the phosphorylation status of RB family proteins, giving importance not only to their inactivation by phosphorylation but also to their dephosphorylation to restore the cell cycle. Abstract Cell cycle progression is highly regulated by modulating the phosphorylation status of the retinoblastoma protein (pRB) and the other two members of the RB family, p107 and p130. This process is controlled by a balance in the action of kinases, such as the complexes formed by cyclin-dependent kinases (CDKs) and cyclins, and phosphatases, mainly the protein phosphatase 1 (PP1). However, while the phosphorylation of the RB family has been largely studied, its dephosphorylation is less known. Phosphatases are holoenzymes formed by a catalytic subunit and a regulatory protein with substrate specificity. Recently, the PP1-Spinophilin (SPN) holoenzyme has been described as the main phosphatase responsible for the dephosphorylation of RB proteins during the G0/G1 transition and at the end of G1. Moreover, SPN has been described as a tumor suppressor dependent on PP1 in lung and breast tumors, where it promotes tumorigenesis by increasing the cancer stem cell pool. Therefore, a connection between the cell cycle and stem cell biology has also been proposed via SPN/PP1/RB proteins.
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Affiliation(s)
- Eva M. Verdugo-Sivianes
- 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
| | - Amancio Carnero
- 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
- Correspondence: ; Tel.: +34-955-92-31-11
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Verdugo-Sivianes EM, Rojas AM, Muñoz-Galván S, Otero-Albiol D, Carnero A. Mutation of SPINOPHILIN (PPP1R9B) found in human tumors promotes the tumorigenic and stemness properties of cells. Am J Cancer Res 2021; 11:3452-3471. [PMID: 33537097 PMCID: PMC7847670 DOI: 10.7150/thno.53572] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 12/20/2020] [Indexed: 12/17/2022] Open
Abstract
Rationale: 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). Methods: 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. Results: 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. Conclusions: 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.
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Verdugo-Sivianes EM, Navas L, Molina-Pinelo S, Ferrer I, Quintanal-Villalonga A, Peinado J, Garcia-Heredia JM, Felipe-Abrio B, Muñoz-Galvan S, Marin JJ, Montuenga L, Paz-Ares L, Carnero A. Coordinated downregulation of Spinophilin and the catalytic subunits of PP1, PPP1CA/B/C, contributes to a worse prognosis in lung cancer. Oncotarget 2017; 8:105196-105210. [PMID: 29285244 PMCID: PMC5739631 DOI: 10.18632/oncotarget.22111] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Accepted: 09/03/2017] [Indexed: 12/20/2022] Open
Abstract
The scaffold protein Spinophilin (Spinophilin, PPP1R9B) is one of the regulatory subunits of phosphatase-1 (PP1), directing it to distinct subcellular locations and targets. The loss of Spinophilin reduces PP1 targeting to pRb, thereby maintaining higher levels of phosphorylated pRb. Spinophilin is absent or reduced in approximately 40% of human lung tumors, correlating with the malignant grade. However, little is known about the relevance of the coordinated activity or presence of Spinophilin and its reported catalytic partners in the prognosis of lung cancer. In the present work, we show that the downregulation of Spinophilin, either by protein or mRNA, is related to a worse prognosis in lung tumors. This effect is more relevant in squamous cell carcinoma, SCC, than in adenocarcinoma. Downregulation of Spinophilin is related to a decrease in the levels of its partners PPP1CA/B/C, the catalytic subunits of PP1. A decrease in these subunits is also related to prognosis in SCC and, in combination with a decrease in Spinophilin, are markers of a poor prognosis in these tumors. The analysis of the genes that correlate to Spinophilin in lung tumors showed clear enrichment in ATP biosynthesis and protein degradation GO pathways. The analysis of the response to several common and pathway-related drugs indicates a direct correlation between the Spinophilin/PPP1Cs ratio and the response to oxaliplatin and bortezomib. This finding indicates that this ratio may be a good predictive biomarker for the activity of the drugs in these tumors with a poor prognosis.
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Affiliation(s)
- Eva M Verdugo-Sivianes
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain
| | - Lola Navas
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain
| | - Sonia Molina-Pinelo
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain
| | - Irene Ferrer
- CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain.,H120-CNIO Lung Cancer Clinical Research Unit, Instituto de Investigación Hospital 12 de Octubre and CNIO, Madrid, Spain
| | - Alvaro Quintanal-Villalonga
- H120-CNIO Lung Cancer Clinical Research Unit, Instituto de Investigación Hospital 12 de Octubre and CNIO, Madrid, Spain
| | - Javier Peinado
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,Radiation Oncology Department, Hospital Universitario Virgen del Rocío, Sevilla, Spain
| | - Jose M Garcia-Heredia
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain.,Department of Vegetal Biochemistry and Molecular Biology, University of Seville, Seville, Spain
| | - Blanca Felipe-Abrio
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain
| | - Sandra Muñoz-Galvan
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain
| | - Juan J Marin
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain.,Department of Predictive Medicine and Public Health, Universidad de Sevilla, Sevilla, Spain
| | - Luis Montuenga
- CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain.,Program in Solid Tumors and Biomarkers, Center for Applied Medical Research (CIMA), Pamplona, Spain
| | - Luis Paz-Ares
- CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain.,H120-CNIO Lung Cancer Clinical Research Unit, Instituto de Investigación Hospital 12 de Octubre and CNIO, Madrid, Spain
| | - Amancio Carnero
- Instituto de Biomedicina de Sevilla (IBIS), Hospital Universitario Virgen del Rocío, Universidad de Sevilla, Consejo Superior de Investigaciones Científicas, Sevilla, Spain.,CIBER de Cáncer, Instituto de Salud Carlos III, Pabellón 11, Planta 0, Madrid, Spain
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Schwarzenbacher D, Stiegelbauer V, Deutsch A, Ress AL, Aigelsreiter A, Schauer S, Wagner K, Langsenlehner T, Resel M, Gerger A, Ling H, Ivan C, Calin GA, Hoefler G, Rinner B, Pichler M. Low spinophilin expression enhances aggressive biological behavior of breast cancer. Oncotarget 2016; 6:11191-202. [PMID: 25857299 PMCID: PMC4484449 DOI: 10.18632/oncotarget.3586] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2015] [Accepted: 02/19/2015] [Indexed: 11/25/2022] Open
Abstract
Spinophilin, a putative tumor suppressor gene, has been shown to be involved in the pathogenesis of certain types of cancer, but its role has never been systematically explored in breast cancer. In this study, we determined for the first time the expression pattern of spinophilin in human breast cancer molecular subtypes (n = 489) and correlated it with survival (n = 921). We stably reduced spinophilin expression in breast cancer cells and measured effects on cellular growth, apoptosis, anchorage-independent growth, migration, invasion and self-renewal capacity in vitro and metastases formation in vivo. Microarray profiling was used to determine the most abundantly expressed genes in spinophilin-silenced breast cancer cells. Spinophilin expression was significantly lower in basal-like breast cancer (p<0.001) and an independent poor prognostic factor in breast cancer patients (hazard ratio = 1.93, 95% confidence interval: 1.24-3.03; p = 0.004) A reduction of spinophilin levels increased cellular growth in breast cancer cells (p<0.05), without influencing activation of apoptosis. Anchorage-independent growth, migration and self-renewal capacity in vitro and metastatic potential in vivo were also significantly increased in spinophilin-silenced cells (p<0.05). Finally, we identified several differentially expressed genes in spinophilin-silenced cells. According to our data, low levels of spinophilin are associated with aggressive behavior of breast cancer.
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Affiliation(s)
| | - Verena Stiegelbauer
- Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Alexander Deutsch
- Division of Hematology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Anna Lena Ress
- Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria
| | | | - Silvia Schauer
- Institute of Pathology, Medical University of Graz, Austria
| | - Karin Wagner
- Center for Medical Research, Medical University of Graz, Austria
| | - Tanja Langsenlehner
- Department of Therapeutic Radiology and Oncology, Medical University of Graz, Austria
| | - Margit Resel
- Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Armin Gerger
- Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria
| | - Hui Ling
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, TX, USA
| | - Cristina Ivan
- Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, TX, USA
| | - George Adrian Calin
- Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, TX, USA.,Center for RNA Interference and Non-Coding RNAs, The University of Texas MD Anderson Cancer Center, TX, USA
| | - Gerald Hoefler
- Institute of Pathology, Medical University of Graz, Austria
| | - Beate Rinner
- Center for Medical Research, Medical University of Graz, Austria
| | - Martin Pichler
- Division of Oncology, Department of Internal Medicine, Medical University of Graz, Austria.,Department of Experimental Therapeutics, The University of Texas MD Anderson Cancer Center, TX, USA
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Loss of the tumor suppressor spinophilin (PPP1R9B) increases the cancer stem cell population in breast tumors. Oncogene 2015; 35:2777-88. [DOI: 10.1038/onc.2015.341] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 08/06/2015] [Accepted: 08/07/2015] [Indexed: 12/14/2022]
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Estevez-Garcia P, Lopez-Calderero I, Molina-Pinelo S, Muñoz-Galvan S, Salinas A, Gomez-Izquierdo L, Lucena-Cacace A, Felipe-Abrio B, Paz-Ares L, Garcia-Carbonero R, Carnero A. Spinophilin loss correlates with poor patient prognosis in advanced stages of colon carcinoma. Clin Cancer Res 2013; 19:3925-35. [PMID: 23729363 DOI: 10.1158/1078-0432.ccr-13-0057] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE The genomic region 17q21 is frequently associated with microsatellite instability and LOH in cancer, including gastric and colorectal carcinomas. This region contains several putative tumor suppressor genes, including Brca1, NM23, prohibitin, and spinophilin (Spn, PPP1R9B, neurabin II). The scaffold protein Spn is one of the regulatory subunits of phosphatase-1 (PP1) that targets PP1 to distinct subcellular locations and couples PP1 to its target. Thus, Spn may alter cell-cycle progression via the regulation of the phosphorylation status of the retinoblastoma protein, a direct target of PP1. Therefore, we analyzed whether Spn levels were reduced in colorectal carcinomas and whether Spn levels correlated with prognosis or response to therapy. EXPERIMENTAL DESIGN By means of immunohistochemistry or quantitative PCR, we studied the levels of Spn in stages II, III, and IV colorectal carcinoma tumors and correlated to other clinicopathologic features as well as prognosis or response to therapy. RESULTS Spn was lost in a percentage of human gastric, small intestine, and colorectal carcinomas. In patients with colorectal carcinoma, tumoral Spn downregulation correlated with a more aggressive histologic phenotype (poorer tumor differentiation and higher proliferative Ki67 index). Consistent with this observation, lower Spn protein expression levels were associated with faster relapse and poorer survival in patients with stage III colorectal carcinoma, particularly among those receiving adjuvant fluoropyrimidine therapy. We validated this result in an independent cohort of patients with metastatic colorectal carcinoma treated with standard chemotherapy. Although patients that achieved an objective tumor response exhibited Spn levels similar to nontumoral tissue, nonresponding patients showed a significant reduction in Spn mRNA levels. CONCLUSIONS Our data suggest that Spn downregulation contributes to a more aggressive biologic behavior, induces chemoresistance, and is associated with a poorer survival in patients with advanced stages of colorectal carcinoma.
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Low expression of the putative tumour suppressor spinophilin is associated with higher proliferative activity and poor prognosis in patients with hepatocellular carcinoma. Br J Cancer 2013; 108:1830-7. [PMID: 23591196 PMCID: PMC3658515 DOI: 10.1038/bjc.2013.165] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Spinophilin, a multifunctional intracellular scaffold protein, is reduced in certain types of cancer and is regarded as a novel putative tumour suppressor protein. However, the role of spinophilin in hepatocellular carcinoma (HCC) has never been explored before. METHODS In this study, we determined for the first time the expression pattern of spinophilin in human HCC by immunohistochemistry and quantitative reverse transcriptase-PCR analysis. In addition, we performed immunohistochemical analysis of p53, p14(ARF) and the proliferation marker Ki-67. Kaplan-Meier curves and multivariate Cox proportional models were used to study the impact on clinical outcome. Small interfering RNA (siRNA) was used to silence spinophilin and to explore the effects of reduced spinophilin expression on cellular growth. RESULTS In our study, complete loss of spinophilin immunoreactivity was found in 44 of 104 HCCs (42.3%) and reduced levels were found in an additional 37 (35.6%) cases. After adjusting for other prognostic factors, multivariate Cox regression analysis identified low expression of spinophilin as an independent prognostic factor with respect to disease-free (hazard ratio (HR)=1.8; 95% confidence interval (CI)=1.04-3.40; P=0.043) and cancer-specific survival (HR=2.0; CI=1.1-3.8; P=0.025). Reduced spinophilin expression significantly correlated with higher Ki-67 index in HCC (P=0.014). Reducing spinophilin levels by siRNA induced a higher cellular growth rate and increased cyclin D2 expression in tumour cells (P<0.05). CONCLUSION This is the first study of the expression pattern and distribution of spinophilin in HCC. According to our data, the loss of spinophilin is associated with higher proliferation and might be useful as a prognostic marker in patients with HCC.
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Sarrouilhe D, Ladeveze V. [When the curtain goes up on spinophilin's tumor suppressor function]. Med Sci (Paris) 2012; 28:26-8. [PMID: 22289823 DOI: 10.1051/medsci/2012281009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Denis Sarrouilhe
- Institut de Physiologie et Biologie Cellulaires, Pôle Biologie Santé, Université de Poitiers, CNRS UMR 6187, 40, Avenue du Recteur Pineau, Poitiers, 86022, France.
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Affiliation(s)
- Aaron J Schetter
- National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
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Molina-Pinelo S, Ferrer I, Blanco-Aparicio C, Peregrino S, Pastor MD, Alvarez-Vega J, Suarez R, Verge M, Marin JJ, Hernandez-Losa J, Ramon y Cajal S, Paz-Ares L, Carnero A. Down-regulation of spinophilin in lung tumours contributes to tumourigenesis. J Pathol 2011; 225:73-82. [PMID: 21598252 DOI: 10.1002/path.2905] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2011] [Revised: 03/01/2011] [Accepted: 03/17/2011] [Indexed: 01/22/2023]
Abstract
The scaffold protein spinophilin (Spn, PPP1R9B) is one of the regulatory subunits of phosphatase-1a (PP1), targeting it to distinct subcellular locations and to its target. Loss of Spn reduces PPP1CA levels, thereby maintaining higher levels of phosphorylated pRb. This effect contributes to an increase in p53 activity. However, in the absence of p53, reduced levels of Spn increase the tumourigenic properties of cells. In addition, Spn knockout mice have a reduced lifespan, an increased number of tumours and increased cellular proliferation in some tissues, such as the mammary ducts. In addition, the combined loss of Spn and p53 activity leads to an increase in mammary carcinomas, confirming the functional relationship between p53 and Spn. In this paper, we report that Spn is absent in 20% and reduced in another 37% of human lung tumours. Spn reduction correlates with malignant grade. Furthermore, the loss of Spn also correlates with p53 mutations. Analysis of miRNAs in a series of lung tumours showed that miRNA106a* targeting Spn is over-expressed in some patients, correlating with decreased Spn levels. Proof-of-concept experiments over-expressing miRNA106a* or Spn shRNA in lung tumour cells showed increased tumourigenicity. In conclusion, our data showed that miRNA106a* over-expression found in lung tumours might contribute to tumourigenesis through Spn down-regulation in the absence of p53.
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