Activation of the PI3K/AKT/mTOR pathway in diffuse large B cell lymphoma: clinical significance and inhibitory effect of rituximab

Diffuse large B cell lymphoma (DLBCL) represents the most common subtype of non-Hodgkin lymphoma and accounts for approximately 30 % of newly diagnosed lymphoid neoplasms in Western countries, and 40–50 % in China. A better understanding of the biology of DLBCL is needed for the development of potential therapeutic agents that target specific intracellular pathways. In this study, expression of the important components of the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway and their clinical significance were investigated in 73 DLBCL cases. The effect of rituximab alone or combined with the PI3K/AKT/mTOR pathway inhibitor rapamycin was further evaluated in the DLBCL cell lines. A total of 73 patients were identified, including 45 men and 28 women aged 18 to 78 years (median age 50 years). Of these patients, p-AKT was positive in 40 cases (54.8 %), p-p70S6K in 34 cases (46.6 %), and p-4E-BP1 in 33 cases (45.2 %). Activation of the PI3K/AKT/mTOR pathway was related to poor disease outcome in DLBCL patients treated with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) but not in those treated with rituximab-CHOP. Rituximab combined with rapamycin synergically downregulated the PI3K/AKT/mTOR signaling pathway. Western blot analysis revealed a baseline activation status of the PI3K/AKT/mTOR pathway in DLBCL cell lines, with high levels of p-AKT, p-mTOR, in addition to downstream molecules p-p70S6K and p-4E-BP1. The results indicate that the PI3K/AKT/mTOR pathway is a potentially important signaling route and an unfavorable prognostic factor for DLBCL. Patients with PI3K/AKT/mTOR activation experience a more rapidly deteriorating clinical course with poor treatment response and decreased survival time. Addition of rituximab could downregulate PI3K/AKT/mTOR activation, reversing its negative effect on chemotherapy-treated patients. In addition, our results indicate that the combination of rituximab and inhibition of the activated PI3K/AKT/mTOR pathway could be a promising target for DLBCL therapeutic intervention in the future.     

肾透明细胞癌组织中AKT／mTOR的表达变化及意义

目的观察磷酸化蛋白激酶B（p-AKT）和磷酸化哺乳动物雷帕霉素靶蛋白（p-mTOR）因子在肾透明细胞癌组织中的表达变化,为mTOR及AKT抑制剂应用于肾透明细胞癌的治疗提供依据。方法用免疫组化染色测定肾透明细胞癌和正常肾组织中p-AKT和p-mTOR的表达情况。结果p-AKT在肾透明细胞癌和正常肾组织中的阳性表达率分别为61．3％、26．1％（P〈0．01）,p-mTOR的阳性表达率分别为56．0％、28．3％（P〈0．05）。P—AKT表达与肿瘤临床分期明显相关,临床分期越高,其阳性表达率越高（P〈0．05）。p-mTOR蛋白表达与肿瘤临床分期也具有相关性（P〈0．05）。肾透明细胞癌组织中p-AKT与p-mTOR的表达呈正相关（r=0．953,P=0．000）。结论AKT／mTOR信号通路在肾透明细胞癌组织中被过度激活。理论上,应用mTOR及AKT抑制剂可治疗肾透明细胞癌。     

肝癌细胞转移与PI3K-Akt-PAK1通路的相关性研究

目的 研究肝细胞癌（HCC）组织PI3K/Akt/ p21活化蛋白激酶1（PAK1）信号通路的表达对于HCC发生及转移的重要性,以期为HCC的预防和预后提供一个有效的分子标志,并为HCC的治疗提供一定的理论基础。方法 自NCBI中GEO数据库中的GES364数据集提取数据,对PI3K/Akt/PAK1信号通路基因的表达量进行分析。结果 将数据库中HCC组织分为肝内扩散组（PS）、肝外转移组（PM）、无转移组（PN）和正常肝对照组（H）。分析发现PS组和PM组PAK1和MMP-9表达量明显高于H组和PN组（P<0.0001）;PS组、PM组和PN组AKT（1/2）和Girdin表达量明显高于H组（P<0.05）,PS组和PM组AKT2和Girdin表达量也明显高于PN组（P<0.05）;在PM组,AKT2与PAK1表达呈正相关（r=0.5679,P=0.0013）。结论 PAK1和MMP-9高表达可以促进HCC的扩散和转移,而AKT的表达和活性对于HCC的转移也是至关重要的,提示PI3K/AKT/PAK1信号通路与HCC转移密切相关。     

PI3K/Akt/mTOR信号转导通路在肝细胞癌发生发展中的作用

PI3K/Akt/mTOR信号转导通路可以通过调控基因表达,在肝细胞癌肿瘤细胞生成、增殖、转移和凋亡等过程中发挥重要作用。简述了PI3K/Akt/mTOR信号通路的组成及功能,对PI3K/Akt/mTOR通路在肝细胞癌进程中的作用机制及相关抑制剂的研究进展进行了综述,揭示阻断PI3K/Akt/mTOR通路可以成为肝细胞癌治疗新的靶点方向。     

Blockade of Rho/Rho-associated coiled coil-forming kinase signaling can prevent progression of hepatocellular carcinoma in matrix metalloproteinase-dependent manner

Aim:  There is growing evidence that the Rho/Rho-associated coiled coil-forming kinase (ROCK) signaling pathway is upregulated in tumors and plays a key role in cancer invasion and metastasis. Our aim was to test the anticancer effects of Rho/ROCK inhibitor, Y-27632, including possible mechanisms in a highly-metastasizing hepatocellular carcinoma (HCC) mouse model on its secretion of matrix metalloproteinase (MMP) and tumor progression.
Methods:  Following orthotopic implantation of CBO140C12 HCC tumor fragments into the liver of mice, the mice were randomly assigned to a Y-27632-treated group or control group. After treatment for 4 weeks, specimens were obtained to evaluate tumor size, metastases, and immunohistochemical findings. In vitro , we examined the effects of Y-27632 and RhoC siRNA on MMP-2 and -9 expressions, invasiveness, and apoptosis in cultured tumor cells.
Results:  Both RhoA and RhoC were upregulated in HCC-bearing livers, and Y-27632 significantly inhibited not only tumor growth and intrahepatic metastasis ( P  < 0.05), but also tumoral MMP-9 expression. Moreover, Y-27632 treatment resulted in large necrotic areas in tumors. In vitro , Y-27632 and RhoC siRNA reduced MMP-2 and -9 expressions, as well as the chemotactic migration of tumor cells dose-dependently, and increased apoptosis eight times.
Conclusion:  Y-27632 suppresses progression and limits the intrahepatic metastasis of established HCC. This could be linked to the decreased MMP expression and induction of apoptosis in tumor cells. Rho signaling may prove to be a productive target in anticancer therapy.     

Phosphatidylethanolamine-binding protein 4 promotes lung cancer cells proliferation and invasion via PI3K/Akt/mTOR axis

Background

While phosphatidylethanolamine-binding protein 4 (PEBP4) is a key factor in the malignant proliferation and metastasis of tumor cells, the exact regulatory network governing its roles remains unclear. This study was designed to investigate the effect of PEBP4 on PI3K/Akt/mTOR pathway and explore its molecular network that governs the proliferation and metastasis of tumor cells.

Methods

After the recombinant plasmid pcDNA3.1-PEBP4 was constructed, the recombinant plasmid pcDNA3.1-PEBP4 and PEBP4-targeting siRNA were transfected into lung cancer HCC827 cell line. The expressions of PI3K/Akt/mTOR pathway components in HCC827 cells in each group were determined using Western blotting. In the HCC827 cells, the effect of PI3K pathway inhibitor {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 on the expressions of PI3K/Akt/mTOR pathway components under the effect of PEBP4 was determined using Western blotting, and the effects of {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 on the cell viability, proliferation, and migration capabilities under the overexpression of PEBP4 were determined using MTT method, flow cytometry, and Transwell migration assay. Furthermore, the effect of mTOR inhibitor rapamycin (RAPA) on the expressions of PI3K/Akt/mTOR pathway components under the effect of PEBP4 was determined using Western blotting, and the effects of RAPA on the cell viability, proliferation, and migration capabilities under the overexpression of PEBP4 were determined using MTT method, flow cytometry, and Transwell migration assay.

Results

As shown by Western blotting, the protein expressions of p-Akt and phosphorylated mTOR (p-mTOR) were significantly higher in the pcDNA3.1-PEBP4-transfected group than in the normal control group and PEBP4 siRNA group (P<0.05); furthermore, the protein expressions of p-Akt and p-mTOR significantly decreased in the PEBP4 targeting siRNA-transfected group (P<0.05). Treatment with {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 significantly inhibited the protein expressions of p-Akt and p-mTOR in HCC827 cells (P<0.05). In contrast, treatment with RAPA only significantly inhibited the protein expression of p-mTOR (P<0.05). As shown by MTT, flow cytometry, and Transwell migration assay, both {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 and RAPA could significantly lower the viability of HCC827 cells and inhibit their proliferation and invasion (P<0.05); meanwhile, they could reverse the effect of PEBP4 in promoting the proliferation and migration of HCC827 cells (P<0.05).

Conclusions

The overexpression of PEBP4 increases the phosphorylation levels of Akt and mTOR in lung cancer cells. The PI3K/Akt/mTOR signaling axis may be a key molecular pathway via which PEBP4 promotes the proliferation and invasion of non-small cell lung cancer (NSCLC) cells; also, it may serve as a potential therapeutic target.     

PTEN/PI3K/AKT蛋白、miR-21在青海藏族及汉族胃癌患者癌组织中的表达差异

目的探讨PTEN/PI3K/AKT蛋白、miR-21在青海藏族及汉族胃癌患者癌组织中的表达差异。方法选取2016年12月至2018年12月我院胃肠外科进行手术的78例胃癌患者为研究对象(藏族38例,汉族40例)。采用实时荧光定量PCR法检测癌组织标本及癌旁组织中miR-21水平,采用免疫组化染色法检测PTEN/PI3K/AKT蛋白,分析不同民族胃癌患者不同组织PTEN/PI3K/AKT蛋白、miR-21表达情况,同时分析其与临床病理特征之间的关系。结果汉族、藏族胃癌患者癌组织中miR-21表达水平高于癌旁组织(P<0.05),且汉族癌组织中miR-21表达水平明显高于藏族(P<0.05)。汉族、藏族胃癌患者癌组织中PTEN、PI3K、AKT蛋白阳性率比较,差异均有统计学意义(P<0.05),其中汉族胃癌组织中PTEN蛋白阳性率低于藏族,但PI3K、AKT蛋白阳性率高于藏族(P<0.05)。两民族胃癌组织中的PTEN、AKT蛋白、miR-21表达与TNM分期、分化程度、淋巴转移相关(P<0.05),PI3K蛋白表达与TNM分期、淋巴转移相关(P<0.05)。在汉族、藏族胃癌患者中,miR-21与PTEN蛋白均呈负相关,与PI3K、AKT蛋白均呈正相关(P<0.05)。结论PTEN在藏族、汉族胃癌患者中表达水平降低,且汉族表达低于藏族,且PTEN与PI3K、AKT呈负相关,miR-21可能通过抑制PTEN,激活PI3K、AKT信号通路从而参与胃癌患者的发生、发展。     

肿瘤相关成纤维细胞外泌体调控PI3K/AKT/mTOR信号通路影响肺癌细胞的生长和转移

目的探究肿瘤相关成纤维细胞外泌体对肺癌细胞生长和转移的影响及机制。方法取肺癌患者的癌组织和癌旁组织分离肿瘤相关成纤维细胞(Cancer-associated fibroblasts,CAFs)和成纤维细胞(Normal Fibroblasts,NFs),免疫荧光和Western blot鉴定CAFs和NFs中α-SMA、FSP-1、FAP、Vimentin表达,差速离心法提取CAFs和NFs细胞外泌体,利用透射电镜和Western blot鉴定外泌体,将外泌体与肺癌细胞A549共孵育后检测细胞增殖、迁移、侵袭、细胞凋亡水平,Western blot检测PI3K/AKT/mTOR信号通路激活水平。结果α-SMA、FSP-1、FAP、Vimentin高表达于CAFs;透射电镜和Western blot鉴定外泌体符合其特征;与PBS组相比,与CAFs外泌体共孵育组A549细胞增殖、迁移、侵袭能力显著增加(P<0.001),细胞凋亡水平显著降低(P<0.001),PI3K、AKT、mTOR磷酸化水平显著增加,而与NFs外泌体共孵育后细胞增殖、迁移、侵袭以及凋亡水平无显著变化,PI3K、AKT、mTOR磷酸化水平无显著变化。结论肿瘤相关成纤维细胞外泌体能够通过激活PI3K/AKT/mTOR信号通路,而促进肺癌细胞的生长和转移。     

The role of PTEN/Akt/PI3K signaling in the maintenance and viability of prostate cancer stem-like cell populations

Characterization of the molecular pathways that are required for the viability and maintenance of self-renewing tumor-initiating cells may ultimately lead to improved therapies for cancer. In this study, we show that a CD133⁺/CD44⁺ population of cells enriched in prostate cancer progenitors (PCaPs) has tumor-initiating potential and that these progenitors can be expanded under nonadherent, serum-free, sphere-forming conditions. Cells grown under these conditions have increased in vitro clonogenic and in vivo tumorigenic potential. mRNA expression analysis of cells grown under sphere-forming conditions, compared with long-term monolayer cultures, revealed preferential activation of the PI3K/AKT signaling pathway. PI3K p110α and β-protein levels were higher in cells grown under sphere-forming conditions, and phosphatase and tensin homolog (PTEN) knockdown by shRNA led to an increase in sphere formation as well as increased clonogenic and tumorigenic potential. Similarly, shRNA knockdown of FoxO3a led to an increase in tumorigenic potential. Consistent with these results, inhibition of PI3K activity by the dual PI3K/mTOR inhibitor NVP-BEZ235 led to growth inhibition of PCaPs. Taken together, our data strongly suggest that the PTEN/PI3K/Akt pathways are critical for prostate cancer stem-like cell maintenance and that targeting PI3K signaling may be beneficial in prostate cancer treatment by eliminating prostate cancer stem-like cells.     

RNA干扰程序性细胞死亡因子4表达对缺氧/复氧H9C2心肌细胞凋亡的影响及其机制

目的 探讨RNA干扰程序性细胞死亡因子4（PDCD4）表达对缺氧/复氧（H/R）H9C2心肌细胞凋亡的影响及其机制。方法 将H9C2心肌细胞分为对照组、H/R组、H/R+NC组和H/R+siPDCD4组。采用逆转录-聚合酶链反应（RT-PCR）和蛋白质印迹法（Western blot）分别检测4组H9C2心肌细胞中PDCD4 mRNA和蛋白水平,流式细胞仪检测其凋亡率,酶联免疫吸附试验（ELISA）检测其上清液中丙二醛（MDA）、超氧化物歧化酶（SOD）、乳酸脱氢酶（LDH）水平,Western blot检测磷脂酰肌醇-3-激酶（PI3K）/蛋白激酶B（AKT）信号通路相关蛋白水平。结果H/R组H9C2心肌细胞PDCD4 mRNA和蛋白、活化的Caspase-3、Bcl-2相关X(Bax)蛋白、上清液中LDH、MDA水平及凋亡率均高于对照组,而上清液中SOD水平、H9C2心肌细胞Bcl-2和p-AKT蛋白水平均低于对照组（P<0.05）。H/R+siPDCD4组H9C2心肌细胞PDCD4 mRNA和蛋白、活化的Caspase-3、Bax蛋白、上清液中LDH、MDA水平及凋亡率均低于H/R组,而上清液中SOD、H9C2心肌细胞Bcl-2和p-AKT蛋白水平均高于H/R组（P<0.05）。结论 RNA干扰PDCD4表达可抑制H/R引起的H9C2心肌细胞凋亡,其作用机制可能与激活PI3K/AKT信号通路进而降低氧化应激反应有关。     

Inducible knockout of GRP78/BiP in the hematopoietic system suppresses Pten-null leukemogenesis and AKT oncogenic signaling

Traditionally, GRP78 is regarded as protective against hypoxia and nutrient starvation prevalent in the microenvironment of solid tumors; thus, its role in the development of hematologic malignancies remains to be determined. To directly elucidate the requirement of GRP78 in leukemogenesis, we created a biallelic conditional knockout mouse model of GRP78 and PTEN in the hematopoietic system. Strikingly, heterozygous knockdown of GRP78 in PTEN null mice is sufficient to restore the hematopoietic stem cell population back to the normal percentage and suppress leukemic blast cell expansion. AKT/mTOR activation in PTEN null BM cells is potently inhibited by Grp78 heterozygosity, corresponding with suppression of the PI3K/AKT pathway by GRP78 knockdown in leukemia cell lines. This is the first demonstration that GRP78 is a critical effector of leukemia progression, at least in part through regulation of oncogenic PI3K/AKT signaling. In agreement with PI3K/AKT as an effector for cytosine arabinoside resistance in acute myeloid leukemia, overexpression of GRP78 renders human leukemic cells more resistant to cytosine arabinoside-induced apoptosis, whereas knockdown of GRP78 sensitizes them. These, coupled with the emerging association of elevated GRP78 expression in leukemic blasts of adult patients and early relapse in childhood leukemia, suggest that GRP78 is a novel therapeutic target for leukemia.     

Pantoprazole Induces Apoptosis of Leukemic Cells by Inhibiting Expression of P-Glycoprotein/Multidrug Resistance-Associated Protein-1 Through PI3K/AKT/mTOR Signaling

This study aims to investigate the effects and mechanism of pantoprazole on multidrug resistant leukemia K562/A02 and K562/ADM cell lines. K562/A02 and K562/ADM cells at logarithmic growth phase were pre-treated with different concentration of pantoprazole (0, 50, 100, 200 μg/mL) for 24 h. Flow cytometry was used to measure the cell growth cycle and apoptosis. RT-PCR and Western blot were used to measure the expression of p-PI3K, p-AKT, p-mTOR, P-glycoprotein (P-gp) and multidrug resistance-associated protein-1 (MRP1). Pantoprazole pretreatment significantly increased the ratio of G0/G1 phase but decreased the S phase of K562/A02 and K562/ADM cells in dose-dependent manner (p < 0.05). Flow cytometry analysis indicated that pretreatment of leukemic cells with pantoprazole induced apoptosis in a dose-dependent manner. RT-PCR and Western blot analysis indicated that pantoprazole pretreatment inhibited the mRNA and protein expression of p-PI3K, p-Akt, p-mTOR, P-gp and MRP1 in K562/A02 and K562/ADM cells in a dose-dependent manner (p < 0.05). Pantoprazole arrested cell cycle and induced apoptosis of multidrug resistant leukemic cells by inhibiting the expression of P-gp and MRP1 through PI3K/Akt/mTOR signaling pathway.     

MicroRNA-7 inhibits tumor growth and metastasis by targeting the phosphoinositide 3-kinase/Akt pathway in hepatocellular carcinoma

MicroRNAs (miRNAs) are known to be involved in carcinogenesis and tumor progression in hepatocellular carcinoma (HCC). Recently, microRNA-7 (miR-7) has been proven to play a substantial role in glioblastoma and breast cancer, but its functions in the context of HCC remain unknown. Here, we demonstrate that miR-7 inhibits HCC cell growth and metastasis in vitro and in vivo. We first screened and identified a novel miR-7 target, phosphoinositide 3-kinase catalytic subunit delta (PIK3CD). Overexpression of miR-7 would specifically and markedly down-regulate its expression. miR-7-overexpressing subclones showed significant cell growth inhibition by G(0) /G(1) -phase cell-cycle arrest and significant impairment of cell migration in vitro. To identify the mechanisms, we investigated the phosphoinositide 3-kinase (PI3K)/Akt pathway and found that Akt, mammalian target of rapamycin (mTOR), and p70S6K were down-regulated, whereas 4EBP1 was up-regulated in miR-7-overexpressing subclones. We also identified two novel, putative miR-7 target genes, mTOR and p70S6K, which further suggests that miR-7 may be a key regulator of the PI3K/Akt pathway. In xenograft animal experiments, we found that overexpressed miR-7 effectively repressed tumor growth (3.5-fold decrease in mean tumor volume; n = 5) and abolished extrahepatic migration from liver to lung in a nude mouse model of metastasis (n = 5). The number of visible nodules on the lung surface was reduced by 32-fold. A correlation between miR-7 and PIK3CD expression was also confirmed in clinical samples of HCC. CONCLUSION: These findings indicate that miR-7 functions as a tumor suppressor and plays a substantial role in inhibiting the tumorigenesis and reversing the metastasis of HCC through the PI3K/Akt/mTOR-signaling pathway in vitro and in vivo. By targeting PIK3CD, mTOR, and p70S6K, miR-7 efficiently regulates the PI3K/Akt pathway. Given these results, miR-7 may be a potential therapeutic or diagnostic/prognostic target for treating HCC.     

mTOR inhibitor for the treatment of hepatocellular carcinoma

Mammalian target of rapamycin (mTOR) plays a central role in the regulation of cellular growth, proliferation, and survival via a cytoplasmic serine/threonine kinase. mTOR also works as a nutrition sensor to monitor cellular metabolism. mTOR is located downstream in the PI3K/Akt pathway, in which Akt and the tuberous sclerosis complex (TSC) 1/2 are involved, to form a signal transduction pathway. New anticancer agents that target mTOR in the PI3K/Akt pathway of the signal transduction pathways involved in cell proliferation control have recently been developed and are already commercially available. A phase III clinical trial of mTOR inhibitor for hepatocellular carcinoma (HCC) is now ongoing worldwide to expand indications. RAD001 is a signal-transduction inhibitor (STI) that targets mTOR (more specifically, mTORC1). mTORC1 signaling is intricately regulated by mitogens, growth factors, energy, and nutrients. mTORC1 is a regulator essential for general protein synthesis, located downstream of the PI3K/AKT/mTOR pathway, which is dysregulated in most human cancers. Inhibiting mTOR with molecules, such as RAD001, generates additive effects that accompany upstream and downstream target inhibition; alternatively, upstream receptor inhibition is compensated for by inhibiting the downstream pathway, even if some resistance develops against receptor inhibition regardless of initial or acquired resistance. In conclusion, RAD001 is a potential targeted agent for HCC and therefore final results of a phase III study are awaited.     

胡桃醌对胃癌细胞耐药性及细胞中ANXA2、ERCC1表达和AKT/mTOR信号通路的影响

目的研究胡桃醌对胃癌细胞顺铂耐药性及细胞中膜联蛋白A2(ANXA2)和切除修复交叉互补基因1(ERCC1)表达,及对AKT/mTOR信号通路的影响。方法将BGC-823/DDP细胞株随机分为5组:对照组、胡桃醌组、顺铂组、胡桃醌联合顺铂组、LY294002(AKT抑制剂)联合顺铂组。采用MTT法和流式细胞术检测细胞活性和凋亡率,Western blotting检测细胞中相关蛋白表达。结果与对照组比较,顺铂组细胞凋亡率及细胞中Caspase-3、Caspase-9蛋白表达水平升高(P<0.05),而ANXA2、ERCC1、p-AKT、p-mTOR蛋白表达水平降低(P<0.05);与顺铂组比较,胡桃醌不同浓度组细胞中P-gp、MRP1蛋白表达水平降低(P<0.05),细胞增殖抑制率、细胞凋亡率及细胞中Caspase-3、Caspase-9蛋白表达水平升高(P<0.05),ANXA2、ERCC1、p-AKT、p-mTOR蛋白表达水平降低(P<0.05);与顺铂组比较,LY294002处理后,细胞增殖抑制率和凋亡率升高(P<0.05)。结论胡桃醌增强胃癌细胞对顺铂的敏感性,抑制细胞中ANXA2和ERCC1表达,抑制AKT/mTOR信号通路。     

PTEN dosage is essential for neurofibroma development and malignant transformation

Patients with neurofibromatosis type 1 (NF1) carry approximately a 10% lifetime risk of developing a malignant peripheral nerve sheath tumor (MPNST). Although the molecular mechanisms underlying NF1 to MPNST malignant transformation remain unclear, alterations of both the RAS/RAF/MAPK and PI3K/AKT/mTOR signaling pathways have been implicated. In a series of genetically engineered murine models, we perturbed RAS/RAF/MAPK or/and PTEN/PI3K/AKT pathway, individually or simultaneously, via conditional activation of K-ras oncogene or deletion of Nf1 or Pten tumor suppressor genes. Only K-Ras activation in combination with a single Pten allele deletion led to 100% penetrable development of NF lesions and subsequent progression to MPNST. Importantly, loss or decrease in PTEN expression was found in all murine MPNSTs and a majority of human NF1-associated MPNST lesions, suggesting that PTEN dosage and its controlled signaling pathways are critical for transformation of NFs to MPNST. Using noninvasive in vivo PET-CT imaging, we demonstrated that FDG can be used to identify the malignant transformation in both murine and human MPNSTs. Our data suggest that combined inhibition of RAS/RAF/MAPK and PTEN/PI3K/AKT pathways may be beneficial for patients with MPNST.