RABL6A is an essential driver of MPNSTs that negatively regulates the RB1 pathway and sensitizes tumor cells to CDK4/6 inhibitors.
RABL6A 是 MPNSTs 的重要驱动因子，负调控 RB1 通路，使肿瘤细胞对 CDK4/6 抑制剂敏感。
- 作者列表："Kohlmeyer JL","Kaemmer CA","Pulliam C","Maharjan CK","Moreno Samayoa A","Major HJ","Cornick KE","Knepper-Adrian V","Khanna R","Sieren JC","Leidinger M","Meyerholz DK","Zamba KD","Weimer J","Dodd RD","Darbro B","Tanas MR","Quelle DE
PURPOSE:Malignant peripheral nerve sheath tumors (MPNSTs) are deadly sarcomas that lack effective therapies. In most MPNSTs, the retinoblastoma (RB1) tumor suppressor is disabled by hyperactivation of cyclin dependent kinases (CDKs), commonly through loss of CDK inhibitory proteins such as p27(Kip1). RABL6A is an inhibitor of RB1 whose role in MPNSTs is unknown. To gain insight into MPNST development and establish new treatment options, we investigated RABL6A-RB1 signaling and CDK inhibitor-based therapy in MPNSTs. EXPERIMENTAL DESIGN:We examined patient-matched MPNSTs and precursor lesions by RNA-Seq and IHC. Molecular and biological effects of silencing RABL6A and/or p27 in MPNST lines and normal human Schwann cells were determined. Tumor suppressive effects of CDK inhibitors were measured in MPNST cells and orthotopic tumors. RESULTS:RABL6A was dramatically upregulated in human MPNSTs compared to precursor lesions, which correlated inversely with p27 levels. Silencing RABL6A caused MPNST cell death and G1 arrest that coincided with p27 upregulation, CDK downregulation and RB1 activation. The growth suppressive effects of RABL6A loss, and its regulation of RB1, were largely rescued by p27 depletion. Importantly, reactivation of RB1 using a CDK4/6 inhibitor (palbociclib) killed MPNST cells in vitro in a RABL6A-dependent manner and suppressed MPNST growth in vivo. Low-dose combination of drugs targeting multiple RB1 kinases (CDK4/6, CDK2) had enhanced anti-tumorigenic activity associated with potential MPNST cell re-differentiation. CONCLUSIONS:RABL6A is a new driver of MPNST pathogenesis that acts in part through p27-RB1 inactivation. Our results suggest RB1 targeted therapy with multiple pathway drugs may effectively treat MPNSTs.
目的: 恶性外周神经鞘瘤 (MPNSTs) 是一种致命的肉瘤，缺乏有效的治疗方法。在大多数 MPNSTs 中，视网膜母细胞瘤 (retinoblastoma，RB1) 肿瘤抑制因子因细胞周期蛋白依赖性激酶 (cyclin dependent kinases，CDK) 的过度激活而失活，通常通过 CDK 抑制蛋白如 p27 (Kip1) 的缺失。RABL6A 是 RB1 的抑制剂，其在 MPNSTs 中的作用未知。为了深入了解 MPNST 的发展并建立新的治疗方案，我们研究了基于 RABL6A-RB1 信号和 CDK 抑制剂的 MPNST 治疗。 实验设计: 我们通过 RNA-Seq 和 IHC 检查患者匹配的 MPNSTs 和前体病变。测定沉默 RABL6A 和/或 p27 在 MPNST 细胞系和正常人雪旺细胞中的分子和生物学效应。在 MPNST 细胞和原位肿瘤中测定 CDK 抑制剂的肿瘤抑制作用。 结果: 与前体病变相比，RABL6A 在人 MPNSTs 中显著上调，与 p27 水平呈负相关。沉默 RABL6A 引起 MPNST 细胞死亡和 G1 期阻滞，与 p27 上调、 CDK 下调和 RB1 活化一致。RABL6A 缺失的生长抑制作用及其对 RB1 的调节在很大程度上被 p27 缺失所挽救。重要的是，使用 CDK4/6 抑制剂 (palbociclib) 再激活 RB1 在体外以 RABL6A-dependent 的方式杀死 MPNST 细胞，并抑制体内 MPNST 生长。低剂量联合靶向多种 RB1 激酶 (CDK4/6，CDK2) 的药物具有增强的与潜在 MPNST 细胞再分化相关的抗肿瘤活性。 结论: RABL6A 是 MPNST 发病机制的新驱动因子，部分通过 p27-RB1 失活起作用。我们的结果表明，RB1 靶向治疗与多途径药物可能有效治疗 MPNSTs。
METHODS:PURPOSE:To generate a preclinical model of isocitrate dehydrogenase (IDH) mutant gliomas from glioma patients and design a MRS method to test the compatibility of 2-hydroxyglutarate (2HG) production between the preclinical model and patients. METHODS:Five patient-derived xenograft (PDX) mice were generated from two glioma patients with IDH1 R132H mutation. A PRESS sequence was tailored at 9.4 T, with computer simulation and phantom analyses, for improving 2HG detection in mice. 2HG and other metabolites in the PDX mice were measured using the optimized MRS at 9.4 T and compared with 3 T MRS measurements of the metabolites in the parental-tumor patients. Spectral fitting was performed with LCModel using in-house basis spectra. Metabolite levels were quantified with reference to water. RESULTS:The PRESS TE was optimized to be 96 ms, at which the 2HG 2.25 ppm signal was narrow and inverted, thereby leading to unequivocal separation of the 2HG resonance from adjacent signals from other metabolites. The optimized MRS provided precise detection of 2HG in mice compared to short-TE MRS at 9.4 T. The 2HG estimates in PDX mice were in excellent agreement with the 2HG measurements in the patients. CONCLUSION:The similarity of 2HG production between PDX models and parental-tumor patients indicates that PDX tumors retain the parental IDH metabolic fingerprint and can serve as a preclinical model for improving our understanding of the IDH-mutation associated metabolic reprogramming.
METHODS:BACKGROUND:Gliomas consist of a heterogeneous group of tumors. This study aimed to report the incidences of O6-methylguanine-DNA-methyltransferase (MGMT) promoter methylation, 1p19q co-deletion, isocitrate dehydrogenase (IDH) gene mutations, and inactivating mutations of alpha-thalassemia/mental retardation syndrome X-linked (ATRX) in high-grade gliomas in an ethnically diverse population. METHODS:Records of patients who underwent surgery for high-grade gliomas from January 2013 to March 2017 at our institution were obtained. The patients' age, gender, ethnicity, Karnofsky Performance Scale (KPS) score, ability to perform activities of daily living (ADLs), tumor location and biomarkers status were recorded. Data were analyzed using chi-square and Mann-Whitney U tests, Kaplan-Meier estimates and log-rank test. RESULTS:181 patients were selected (56 with grade III gliomas, 125 with grade IV gliomas). In the grade III group, 55% had MGMT promoter methylation, 41% had 1p19q co-deletion, 35% had IDH1 mutation and none had ATRX loss. In the grade IV group, 30% had MGMT promoter methylation, 2% had 1p19q co-deletion, 15% had IDH1 mutation and 8% had ATRX loss. After adjusting for effects of age, surgery and pre-operative ADL statuses, only MGMT promoter methylation was found to be significantly associated with longer overall survival time in grade III (p = 0.024) and IV patients (p = 0.006). CONCLUSIONS:The incidences of MGMT promoter methylation and IDH1 mutation were found to be comparable to globally reported rates, but those of 1p19q co-deletion and ATRX loss seemed to be lower in our cohort. MGMT promoter methylation was associated with increased overall survival in our cohort and might serve as favorable prognostic factor.
METHODS:BACKGROUND:Glioblastoma multiforme is a CNS cancer characterized by diffuse infiltrative growth, aggressive clinical behavior and very poor prognosis. The state-of-art clinical approach to this disease consists of surgical resection followed by radiotherapy plus concurrent and adjuvant chemotherapy with temozolomide. Tumor recurrence occurs in virtually all cases, therefore, despite any treatment, the median survival is very low (14.6 months), which makes the approach to these patients a challenging clinical issue. MAIN BODY:The escalating costs and times required for new medications to reach the bedside make repurposing or repositioning of old drugs, when scientific bases allow their use in other pathologies, an appealing strategy. Here, we analyze a number of literature data concerning the antipsychotic chlorpromazine, the founder of the phenothiazines class of drugs, a medication widely used in the clinics for approximately 60 years. The drug exerts its effects on psychiatric patients by interfering with the dopamine receptor D2, although more recent pharmacodynamics studies ascribe chlorpromazine a series of biological effects on cancer cells, all converging in hindering also glioblastoma survival capabilities. SHORT CONCLUSIONS:On these bases, and assisted by the information on the well-established chlorpromazine toxicity and dosage in humans, we designed a Phase II clinical trial involving the combination of chlorpromazine with the standard treatment, temozolomide, in the adjuvant phase of the therapeutic protocol. Patients displaying hypo-methylation of the MGMT gene, and thus intrinsically resistant to temozolomide, will be enrolled. The endpoints of this study are the analysis of toxicity and clinical activity, as evaluated in terms of Progression-Free Survival, of the association of chlorpromazine with the first-line treatment for this very serious form of cancer.