CDK5在左旋多巴诱发异动症形成中作用的研究

目的研究纹状体区CDK5的表达变化在左旋多巴诱发的异动症（LID）形成中所起的作用。方法以Roscovitine（CDK5拮抗剂）治疗LID大鼠，观察大鼠行为学改变并用免疫印迹技术检测其纹状体区CDK5、Thr-34位点和Thr-75位点磷酸化的DARPP-32蛋白表达的变化。结果LID大鼠毁损侧纹状体区CDK5表达量和Thr-34位点磷酸化的DARPP-32水平均较非LID组显著增高，而Thr-75位点磷酸化的DARPP-32表达与非LID组相比无显著差异。经Roscovitine治疗后，前两者表达均显著下降，而后者较LID组显著增加，同时大鼠异常不自主运动明显减少。结论DARPP-32的Thr-34位点的磷酸化水平的增高与LID的形成关系密切。CDK5的表达增强与机体稳定内环境的代偿性反应有关。     

Cell Cycle Reentry and Cell Proliferation as Candidates for the Seizure Predispositions in the Hippocampus of EL Mouse Brain

Summary:  We have recently found that there was DNA fragmentation without cell loss in the hippocampus in EL mice, an epileptic mutant. Neurotrophic factors are also expressed at high levels during the early developmental stages. In the present study, we used EL mice to examine how altered cyclin and the corresponding cyclin dependent kinase (CDK) family are related to cell proliferation during development and during epileptogenesis. Developmental changes of cyclin family and corresponding CDK family (cyclin D/CDK-4, cyclin E/CDK-2, cyclin A/CDK-2, cyclin A/CDK-1, cyclin B/CDK-1) were examined by Western blotting in the hippocampus of EL mice and in nonepileptic control animals (DDY mice). In addition, we attempted to quantify cell proliferation during this period. The developmental changes in cell proliferation were determined by using systemic injections of Bromo-deoxyUridine (BrdU) to label dividing cells. As compared with the control DDY mice, EL mice show an upregulation of cell cycle specific Cyclins/CDKs during early developmental stages suggesting that reentry into the cell cycle is enhanced prior to the onset of seizure activity, possibly due to the abundance of neurotrophic factors. These results show that Cyclins/CDKs are activated during early stages of development in an epileptic animal, before the mouse exhibits seizures. These results suggest that reentry of cells into the cell cycle, with consequent cell proliferation in the hippocampus, contribute to the seizure predispositions of EL mice.     

Non-metabolic function of MTHFD2 activates CDK2 in bladder cancer

Bladder cancer is a common tumor with a high recurrence rate and high fatality rate, and its mechanism of occurrence and development remains unclear. Many proteins and metabolites reprogram at different stages of tumor development to support tumor cell growth. The moonlighting effect happens when a protein performs multiple functions simultaneously in a cell. In this study, we identified a metabolic protein, MTHFD2, which participates in the cell cycle by binding to CDK2 in bladder cancer. MTHFD2 has been shown to affect bladder cancer cell growth, which is independent of its metabolic function. We found that MTHFD2 was involved in cell cycle regulation and could encourage cell cycle progression by activating CDK2 and sequentially affecting E2F1 activation. In addition, moonlighting MTHFD2 might be regulated by the dynamics of the mitochondria. In conclusion, MTHFD2 localizes in the nucleus to perform a distinct function of catalyzing metabolic reactions. Moreover, the nuclear MTHFD2 activates CDK2 and promotes bladder cancer cell growth by modulating the cell cycle.     

Cyclin Pathway Genomic Alterations Across 190,247 Solid Tumors: Leveraging Large‐Scale Data to Inform Therapeutic Directions

BackgroundWe describe the landscape of cyclin and interactive gene pathway alterations in 190,247 solid tumors.MethodsUsing comprehensive genomic profiling (315 genes, >500× coverage), samples were analyzed for alterations in activating/sensitizing cyclin genes (CDK4 amplification, CDK6 amplification, CCND1, CCND2, CCND3, CDKN2B [loss], CDKN2A [loss], SMARCB1), hormone genes (estrogen receptor 1 [ESR1], androgen receptor [AR]), and co‐alterations in genes leading to cyclin inhibitor therapeutic resistance (RB1 and CCNE1).ResultsAlterations in at least one cyclin activating/sensitizing gene occurred in 24% of malignancies. Tumors that frequently harbored at least one cyclin alteration were brain gliomas (47.1%), esophageal (40.3%) and bladder cancer (37.9%), and mesotheliomas (37.9%). The most frequent alterations included CDKN2A (13.9%) and CDKN2B loss (12.5%). Examples of unique patterns of alterations included CCND1 amplification in breast cancer (17.3%); CDK4 alterations in sarcomas (12%); CCND2 in testicular cancer (23.4%), and SMARCB1 mutations in kidney cancer (3% overall, 90% in malignant rhabdoid tumors). Alterations in resistance genes RB1 and CCNE1 affected 7.2% and 3.6% of samples. Co‐occurrence analysis demonstrated a lower likelihood of concomitant versus isolated alterations in cyclin activating/sensitizing and resistance genes (odds ratio [OR], 0.35; p < .001), except in colorectal, cervical, and small intestine cancers. AR and cyclin activating/sensitizing alterations in prostate cancer co‐occurred more frequently (vs. AR alterations and wild‐type cyclin activating/sensitizing alterations) (OR, 1.79; p < .001) as did ESR1 and cyclin activating/sensitizing alterations in breast (OR, 1.62; p < .001) and cervical cancer (OR, 4.08; p = .04) (vs. ESR1 and cyclin wild‐type activating/sensitizing alterations).ConclusionCyclin pathway alterations vary according to tumor type/histology, informing opportunities for targeted therapy, including for rare cancers.Implications for PracticeCyclin pathway genomic abnormalities are frequent in human solid tumors, with substantial variation according to tumor site and histology. Opportunities for targeted therapy emerge with comprehensive profiling of this pathway.     

Proteins of the retinoblastoma pathway,FEN1 and MGMT are novel potential prognostic biomarkers in pancreatic adenocarcinoma

Background

We studied the expression of some major proteins involved in cell-cycle regulation and DNA repair, the roles of which are not well known in pancreatic ductal adenocarcinoma (PDAC), but which have a significant impact on carcinogenesis of many other cancers.

FBXO4 loss facilitates carcinogen induced papilloma development in mice

Cyclin D1 is frequently overexpressed in esophageal squamous cell carcinoma (ESCC) and is considered a key driver of this disease. Mutations in FBXO4, F-box specificity factor that directs SCF-mediated ubiquitylation of cyclin D1, occur in ESCC with concurrent overexpression of cyclin D1 suggesting a potential tumor suppressor role for FBXO4. To evaluate the contribution of FBXO4-dependent regulation cyclin D1 in esophageal squamous cell homeostasis, we exposed FBXO4 knockout mice to N-nitrosomethylbenzylamine (NMBA), an esophageal carcinogen. Our results revealed that loss of FBXO4 function facilitates NMBA induced papillomas in FBXO4 het (+/−) and null (−/−) mice both by numbers and sizes 11 months after single dose NMBA treatment at 2mg/kg by gavage when compared to that in wt (+/+) mice (P < 0.01). No significant difference was noted between heterozygous or nullizygous mice consistent with previous work. To assess cyclin D1/CDK4 dependence, mice were treated with the CDK4/6 specific inhibitor, PD0332991, for 4 weeks. PD0332991 treatment (150mg/kg daily), reduced tumor size and tumor number. Collectively, our data support a role for FBXO4 as a suppressor of esophageal tumorigenesis.     

Phospho-T356RB1 predicts survival in HPV-negative squamous cell carcinoma of the head and neck

Locally advanced squamous cell carcinoma of the head and neck (SCCHN) that is not associated with human papillomavirus (HPV) has a poor prognosis in contrast to HPV-positive disease. To better understand the importance of RB1 activity in HPV-negative SCCHN, we investigated the prognostic value of inhibitory CDK4/6 phosphorylation of RB1 on threonine 356 (T³⁵⁶) in archival HPV-negative tumor specimens from patients who underwent surgical resection and adjuvant radiation. We benchmarked p^T356RB1 to total RB1, Ki67, p^T202/Y204ERK1/2, and TP53, as quantified by automatic quantitative analysis (AQUA), and correlated protein expression with tumor stage and grade. High expression of p^T356RB1 but not total RB1 predicted reduced overall survival (OS; P = 0.0295), indicating the potential relevance of post-translational phosphorylation. Paired analysis of The Cancer Genome Atlas (TCGA) data for regulators of this RB1 phosphorylation identified loss or truncating mutation of negative regulator CDKN2A (p16) and elevated expression of the CDK4/6 activator CCND1 (cyclin D) as also predicting poor survival. Given that CDK4/6 inhibitors have been most effective in the context of functional RB1 and low expression or deletion of p16 in other tumor types, these data suggest such agents may merit evaluation in HPV-negative SCCHN, specifically in cases associated with high p^T356RB1.     

RB1 dual role in proliferation and apoptosis: Cell fate control and implications for cancer therapy

Inactivation of the retinoblastoma (RB1) tumor suppressor is one of the most frequent and early recognized molecular hallmarks of cancer. RB1, although mainly studied for its role in the regulation of cell cycle, emerged as a key regulator of many biological processes. Among these, RB1 has been implicated in the regulation of apoptosis, the alteration of which underlies both cancer development and resistance to therapy. RB1 role in apoptosis, however, is still controversial because, depending on the context, the apoptotic cues, and its own status, RB1 can act either by inhibiting or promoting apoptosis. Moreover, the mechanisms whereby RB1 controls both proliferation and apoptosis in a coordinated manner are only now beginning to be unraveled. Here, by reviewing the main studies assessing the effect of RB1 status and modulation on these processes, we provide an overview of the possible underlying molecular mechanisms whereby RB1, and its family members, dictate cell fate in various contexts. We also describe the current antitumoral strategies aimed at the use of RB1 as predictive, prognostic and therapeutic target in cancer. A thorough understanding of RB1 function in controlling cell fate determination is crucial for a successful translation of RB1 status assessment in the clinical setting.