PTEN suppresses SPARC-induced pMAPKAPK2 and inhibits SPARC-induced Ser78 HSP27 phosphorylation in glioma

Background

Secreted protein acidic and rich in cysteine (SPARC) is overexpressed in astrocytomas (World Health Organization grades II–IV). We previously demonstrated that SPARC promotes glioma migration and invasion—in part, by activating the P38 mitogen-activated protein kinase (MAPK)–heat shock protein (HSP)27 signaling pathway. The commonly lost tumor suppressor phosphatase and tensin homolog (PTEN) suppresses SPARC-induced migration, which is accompanied by suppression of Shc-Ras-Raf-MEK-ERK1/2 and Akt signaling. As PTEN completely suppresses SPARC-induced migration, we proposed that PTEN must also interfere with SPARC-induced HSP27 signaling. Therefore, this study determined the effects of PTEN expression on SPARC-induced expression and phosphorylation of HSP27.

Methods

Control and SPARC-expressing clones transfected with control- or PTEN-expression plasmids were plated on fibronectin-coated tissue culture plates for 3, 6, 24, and 48 h and then lysed. Equal amounts of protein were subjected to Western blot and densitometric analyses.

Results

The results show that SPARC enhances phosphorylated (p)P38 MAPK, phosphorylated MAPK-activated protein kinase 2 (pMAPKAPK2), and serine (Ser)78 HSP27 phosphorylation relative to total HSP27. PTEN suppresses pAkt and pMAPKAPK2, suggesting that PTEN effects are downstream of pP38 MAPK. PTEN suppressed SPARC-induced sustained phosphorylation at Ser78 HSP27. As the level of total HSP27 differed based on the presence of SPARC or PTEN, the ratios of phosphorylation-specific to total HSP27 were examined. The data demonstrate that SPARC-induced phosphorylation at Ser78 remains elevated despite increasing levels of total HSP27. In contrast, PTEN inhibits SPARC-induced increases in Ser78 HSP27 phosphorylation relative to total HSP27.

Conclusion

These data describe a novel mechanism whereby PTEN inhibits SPARC-induced migration through suppression and differential regulation of pAkt and the P38 MAPK-MAPKAPK2-HSP27 signaling pathway.     

T2-FLAIR失配征预测IDH突变-无1p/19q共缺失型胶质瘤的研究进展

病灶在T₂WI上呈完全或近乎完全均匀的高信号,在液体衰减反转恢复（FLAIR）序列上呈相对低信号,即为T₂-FLAIR失配征。其诊断IDH突变-无1p/19q共缺失型星形细胞瘤具有较高的特异性,可以术前预测成人星形细胞瘤的IDH基因表型。在临床制定手术计划、治疗策略和预测病人预后方面具有重要的指导意义。就T₂-FLAIR失配征诊断IDH突变-无1p/19q共缺失型星形细胞瘤的临床应用、验证研究及其应用原则、潜在的病理生理学机制予以综述,以最大程度地提高其在神经胶质瘤诊疗中的作用。     

IDH mutation, 1p19q codeletion and ATRX loss in WHO grade II gliomas

Background

Epigenetic, genetic, and molecular studies have identified several diagnostic and prognostic markers in diffuse gliomas. Their importance for evaluating WHO grade II gliomas has yet to be specifically delineated.

Methods

We analyzed markers, including IDH mutation(IDHmut), 1p19q codeletion(1p19qcodel), ATRX expression loss(ATRX loss) and p53 overexpression, and outcomes in 159 patients with WHO grade II oligodendroglioma, oligoastrocytoma, and astrocytoma (2003–2012).

Results

IDHmut was found in 141(91%) and ATRX loss in 64(87%) of IDHmut-noncodel tumors (p = 0.003). All codeleted tumors (n = 66) were IDHmut. Four subgroups were identified: IDHmut-codel, 66(43%); IDHmut-noncodel-ATRX loss, 60(39%); IDHmut-noncodel-ATRXwt, 9(6%); IDHwt, 14(9%). Median survival among 4 groups was significantly different (p = 0.038), particularly in IDHmut-codel (median survival 15.6 years) compared to the remaining 3 groups (p = 0.025). Survival by histology was not significant. Overall (OS), but not progression-free (PFS), survival was significantly longer with gross total resection vs. biopsy only (p = 0.042). Outcomes for patients with subtotal resection were not significantly different from those with biopsy only. Among these uniformly treated patients, OS far exceeds PFS, particularly in those with 1p/19q codeletion.

Conclusions

For WHO grade II diffuse glioma, molecular classification using 1p/19qcodel, IDHmut, and ATRX loss more accurately predicts outcome and should be incorporated in the neuropathologic evaluation.     

Knockdown of microRNA-127 reverses adriamycin resistance via cell cycle arrest and apoptosis sensitization in adriamycin-resistant human glioma cells

The aim of this study was to investigate signaling pathways for reversal of microRNA-127-mediated multi-drug resistance (MDR) in gliomas cells. Adriamycin-resistant glioma cell lines U251/adr and U87-MG/adr were established and we found that anti-microRNA-127 markedly reduced microRNA-127 expression levels in a time-dependent manner, leading to distinct inhibition of cell proliferation and increased apoptosis and the content of intracellular Rh123. Silencing of microRNA-127 significantly increased the sensitivity of U251/ADR and U87-MG/adr cells to adriamycin, compared to cells transfected with negative control siRNA. Silencing of microRNA-127 also significantly reduced the mRNA and protein expression levels of MDR1 and MRP1, which are major ATP-binding cassette (ABC) transporter linked to multi-drug resistance in cancer cells. And Runx2, p53, bcl-2 and survivin, which are important role in cell apoptosis, also markedly changed after microRNA-127 silencing. In addition, down-regulating microRNA-127 decreased the level of phosphorylated-Akt. Our data indicate that down-regulation of micorRNA-127 can trigger apoptosis and overcome drug resistance of gliomas cells. Therefore, this resistance of adriamycin in gliomas can be cancelled by silencing expression of microRNA-127.     

Mn3[Co (CN)6]2@SiO2对鼠C6脑胶质瘤模型3T MR成像及生长规律的研究

目的 利用Mn3[Co(CN)6]2@SiO2对大鼠C6脑胶质瘤模型进行3T MR成像,研究肿瘤的生长规律.方法 收集对数生长期鼠C6胶质瘤细胞,建立鼠C6脑胶质瘤模型,于细胞接种后第7 d行MR扫描,然后鼠尾静脉注射0.5 mL Mn3[Co(CN)6]2@SiO2,于注射后5 min、24 h再行MR扫描,扫描结束后取出肿瘤组织行HE染色.随机抽取脑内成功接种C6胶质瘤细胞的荷瘤鼠10只,接种后第7、9、11、13、15、17、19天行MR扫描,测量肿瘤体积,绘制出肿瘤生长曲线.结果 成功建立了鼠C6脑胶质瘤模型,并且鼠尾静脉注射Mn3[Co(CN)6]2@SiO2后5 min、24 h肿瘤均强化,24 h肿瘤强化较前明显;MRI检测出胶质瘤大小与时间呈正相关关系(rs=0.9944,P=0.000).结论 应用Mn3[Co(CN)6]2@SiO2对鼠C6脑胶质瘤活体示踪MR成像,可以反映肿瘤的生物学特性,适用于肿瘤生长规律的观测.     

p15和WIF－1在人脑胶质瘤中的表达及其临床意义

目的：探讨p15和WIF－1在人脑神经胶质瘤中的表达,及其与临床病理特征和生物学行为的关系。方法：应用免疫组化SP法检测53例神经胶质瘤和20例正常脑组织中p15和WIF－1蛋白的表达,结合病例随访资料分析其临床意义。结果：p15及WIF－1蛋白在神经胶质瘤中的阳性表达率明显低于正常脑组织,差异具有统计学意义（P＜0．05）;p15及WIF－1蛋白的阳性表达率与神经胶质瘤的病理学分级和瘤周脑水肿具有相关性（P＜0．05）,但与性别和年龄不相关（P＞0．05）。p15和WIF－1蛋白在神经胶质瘤中的阳性表达率复发组与无复发组有明显差异（P＜0．05）。p15与WIF－1蛋白的表达呈正相关（r＝－0．396,P＜0．01）。结论：p15、WIF－1的表达与人神经胶质瘤的发生及进展相关;p15、WIF －1低表达患者预后较差。联合检测p15、WIF－1蛋白的表达对神经胶质瘤的早期诊断、判断预后有参考价值。     

3D-CRT versus RapidArc in Deep Tempero-Parietal High Grade Gliomas: Do We Really Need Higher Technology?

Purpose: The aim of this study was to dosimetrically compare single arc RapidArc with conventional 3D-CRT plans for tempero-parietal high grade gliomas with respect to PTV coverage and doses perceived by surrounding critical organs at risk. Methods: Thirty patients with the pathological diagnosis of high grade gliomas (WHO grade III-IV) were selected to be enrolled in our study. Patients were referred to our center (center of Clinical Oncology and Radiotherapy, Cairo University) during the period March 2020 till June 2021 for post-operative irradiation using 3D-CRT technique. For all patients, the dose prescribed to the planning target volume (PTV) was 60 Gy in 30 fractions. A RA plan was performed for each patient and dosimetrically was compared to the 3D-CRT plan. Results: The PTV coverage in terms of V95% was significantly superior in the RA plans with values of 98.4 ± 1.7 compared to 94.4 ± 2.6 for the 3D-CRT plans (p-value of 0.004). The doses risk structures ( eyes, optic nerves and cochleae)  was lower with the RA plans as contrasted to the 3D-CRT plan with an exception for the  intraocular lens which received higher doses in the RA plan with a statistically significant p-value of 0.001 and 0.002 for the  Ipsilateral and contralateral lens, respectively. The average number of MUs ± SD was 358.6± 44.4 for the RA plans versus 247.6 ± 16.1 for 3D-CRT plans (p-value 0.001). The Dmean of healthy brain tissue was nearly equal for both plans (p-value of 0.071). Conclusion: The plans achieved by RA showed superior dose conformity, PTV coverage, more homogeneous dose distribution when contrasted to 3D-CRT plans. With the exception of both intraocular lenses, the RA plans showed better OAR sparing and utilized a higher number of MUs compared to the 3D-CRT.     

Lactate dehydrogenase A silencing in IDH mutant gliomas

Background

Mutations of the isocitrate dehydrogenase 1 and 2 gene (IDH1/2) were initially thought to enhance cancer cell survival and proliferation by promoting the Warburg effect. However, recent experimental data have shown that production of 2-hydroxyglutarate by IDH mutant cells promotes hypoxia-inducible factor (HIF)1α degradation and, by doing so, may have unexpected metabolic effects.

Methods

We used human glioma tissues and derived brain tumor stem cells (BTSCs) to study the expression of HIF1α target genes in IDH mutant (^mt) and IDH wild-type (^wt) tumors. Focusing thereafter on the major glycolytic enzyme, lactate dehydrogenase A (LDHA), we used standard molecular methods and pyrosequencing-based DNA methylation analysis to identify mechanisms by which LDHA expression was regulated in human gliomas.

Results

We found that HIF1α-responsive genes, including many essential for glycolysis (SLC2A1, PDK1, LDHA, SLC16A3), were underexpressed in IDH^mt gliomas and/or derived BTSCs. We then demonstrated that LDHA was silenced in IDH^mt derived BTSCs, including those that did not retain the mutant IDH1 allele (mIDH^wt), matched BTSC xenografts, and parental glioma tissues. Silencing of LDHA was associated with increased methylation of the LDHA promoter, as was ectopic expression of mutant IDH1 in immortalized human astrocytes. Furthermore, in a search of The Cancer Genome Atlas, we found low expression and high methylation of LDHA in IDH^mt glioblastomas.

Conclusion

To our knowledge, this is the first demonstration of downregulation of LDHA in cancer. Although unexpected findings, silencing of LDHA and downregulation of several other glycolysis essential genes raise the intriguing possibility that IDH^mt gliomas have limited glycolytic capacity, which may contribute to their slow growth and better prognosis.