Ras

这是一篇关于Ras的思维导图：Ras-GTP传递信号给Raf-P；Raf-p结合在KSR-PP2A处，传递信号给同在KSR上的MEK-2P+ERK-2P。

Ras-human disease

• 简单介绍
  • Benign Tumors
    • Generally localized and small
    • Fairly common (warts疣, colon polyps, etc.)
    • Do not break out of originating organ
    • Function very much like cells of origin
    • Generally are easily removed by surgery外科手术
  • Malignant Tumors
    • Remain localized for a time but thin invade surrounding tissue
    • Spread by forming metastases
      • Cells travel through circulation
      • Can invade any other body tissues
    • Produce few markers of original tissue
    • Very difficult to treat
  • Cancer metastasis
    • • primary tumor invasion
      • EMT上皮间质转化
      • minimal极小的 residual disease
      • local recurrence复发
      • intravasation
      • circulating tumor cells
      • extravasation
      • micrometastasis
      • metastasis in secondary sites
      • autocrine
      • paracrine
    • 肿瘤转移的常用检测方法 （不考）
• Cancer
  • 产生原因
    • Loss of cell-cycle control
      • Cloned cells divide unchecked
    • Results from multiple genetic mutations
      • Cell cycle genes
      • DNA repair genes
      • Apoptosis genes
      • Growth regulation genes
      • Metabolism
    • Epigenetic regulation
      • DNA methylation, non-coding RNAs, histone modification
  • 是基因活动
    • Activation of oncogenes (continuous "go" signal)
      • 癌基因（oncogene）
        • 其编码区或调节区遗传性状发生改变，增加癌源性或转化潜能的基因
    • Inactivation of tumor suppressor genes (removes "stop" signal)
      • 抑癌基因（Tumor-suppressor gene）
        • 这类因功能丧失后引起肿瘤发生的基因称抑癌基因
        • p53
          • Senescence and tumour clearance is triggered by p53 restoration in murine liver carcinomas 小鼠肝癌的衰老和肿瘤清除是由p53恢复触发的
          • In addition to p53 loss, mutation of p53 was also detected in tumor samples
            • 不同的蛋白在一起会有空间构象，p53的抗原表位可能会被遮盖掉
          • p53 Mutation Frequency in Various Cancers
          • Li–Fraumeni syndrome综合征
            • 1969发现
            • the wide range of cancers found in affected families, the inherited higher risk of developing cancer among generations, and the relatively early age of the cancer diagnosis with nearly half of affected individuals having a cancer diagnosis before age 30.
              • 癌症种类广泛
              • 遗传风险高
              • 诊断出癌症的年龄小
            • Approximately 70% of families with LFS will have a mutation (alteration) in the TP53 gene
  • Ras signaling
    • • Ras
        • NRAS, HRAS, KRAS4A and KRAS4B
      • Raf
        • (ARAF, BRAF, RAF-1)
      • MEK
        • MEK1, MEK2
      • ERK
        • ERK1/2, ERK3/4, ERK5
    • Evolutionary Conservation of the MAPK Signaling pathway
      • 具体的传递链条
        • EC Signal刺激到受体；受体得出adaptor proteins&exchange factors；因此Ras蛋白启动；分其他途径和MAPK途径
        • MAPK途径：Ras--MKKKs--MKKs--MAPKs（ERK）
          • nuclear Txn factors
          • kinases
          • structral proteins
          • other signaling proteins
    • Signaling pathway
    • 三种Ras
      • Harvey sarcoma virus-associated oncogene : Ha-ras (H-ras in mammals)
      • Kirsten sarcoma virus : Ki-ras (K-ras in mammals)
      • N-ras: cloned from neuroblastoma成神经细胞瘤 and leukaemia cell lines
      • KRas, NRas, HRas share 90% homology, the C-terminus region -- hypervariable变异度高的
    • Ras and human cancers
      • Activating Ras mutations occur in 30% of human cancers.
        • pancreatic, colorectal, endometrial, lung and cervical cancers
          • KRAS
        • melanoma
          • NRAS
        • bladder cancer
          • HRAS
      • Ras与人体中不同部位的癌变息息相关，具体看ppt22，23
        • G12,Q61
      • Somatic activation of the K-ras oncogene causes early onset lung cancer in mice
        • K-ras exon 1 with an activating glycine to aspartic acid mutation at codon 12 (G12D) G12D出的甘氨酸突变成了天冬氨酸
      • somatic missense Ras mutations : amino-acid substitutions替换 at G12, G13 and Q61.
        • impair the intrinsic GTPase activity 损害内在酶活性
        • confer resistance to GAPs (GTPase activating protein)给GAPs抗性
        • causing cancer-associated mutant Ras proteins to accumulate in the active, GTP-bound conformation造成癌变相关的Ras积累
      • 三个癌症的例子
        • Cardio-facio-cutaneous syndrome 心脏－脸－皮肤征候群
          • 有问题的地方：KRAS, BRAF, MEK1, MEK2
          • 特征
            • growth failure
            • distinctive facial appearance面容异常
            • Ectodermal abnormalities外胚层畸形
            • congenital heart defects 先天性心脏缺损
            • Not cancer-prone非癌变
        • Costello syndrome科斯特洛综合征
          • 有问题的地方：HRAS
          • 特征
            • delayed development and mental retardation 发育延迟精神迟滞
            • Typical facial appearance
            • loose skin
            • increased creases皱纹 of the hands
            • Rhabdomyosarcoma横纹肌肉瘤, neuroblastoma, ganglioneuroblastoma成神经节细胞瘤, bladder cancer
        • Noonan syndrome努南综合征
          • autosomal dominant disorder, 常染色体显性无序
          • 比例：1/1000-1/2500
          • Mutations in the KRAS and PTPN11 genes cause Noonan syndrome
          • 特征
            • unusual facial characteristics
            • short stature身高
            • heart defects
            • bleeding problems出血
            • skeletal malformations骨骼畸形
            • Eye abnormalities ( 95 % of patients)
            • Problems with language and speech are common
      • B-Raf mutations in human cancer
        • • 路径A
            • EGF与TK-4P结合，刺激结合在TK磷酸基团上的Grb2&SOS传递信号给Ras-GTP
            • Ras-GTP传递信号给Raf-P；Raf-p结合在KSR-PP2A处，传递信号给同在KSR上的MEK-2P+ERK-2P
            • ERK-2P接受信号后去磷酸化，产生四个ERK，进入细胞核中，传递信号给ELK-1+2P+SRF复合物；该复合物作用于DNA上调节基因转录
            • 最终影响细胞增殖，生存，衰老，分化（proliferation,suvival,senescence,differentiation）
          • 路径B
            • 无EGF的情况下，这个时候TK上没有4个P；Grb2和SOS没有结合在一起，Ras-GDP（无能量）
            • V600E结合BRAF，刺激在KSR上的MEK-2P+ERK-2P
            • ERK去磷酸化进核，传递信号给ELK-1+2P+SRF复合物；该复合物作用于DNA上调节基因转录
            • 最终使细胞转化tranformation
        • a valine (V) to a glutamic acid (E)缬氨酸变谷氨酸
        • 看看ppt32对FDG PET的介绍
    • Ras-induced Transformed phenotypes 必考！！
      • Morphology 形态学（上的变化）
        • Loss of contact inhibition
        • 注意这个时候还算不上是癌细胞 eg：NIH3T3 +H-Ras R12 是个可以无限增殖的细胞，但是不是肿瘤细胞
      • Adhesion
        • Anchorage-independent Growth 锚点非依赖
        • 细胞不贴壁也能活
      • Growth
        • Tumor induction肿瘤产生 (nu/nu)
• Cellular Senescence
  • 什么是细胞衰老
    • 定义：Response of normal cells to potentially cancer-causing events：
      • 正常组织受到的影响变成initiated cell
        • telomere shortening端粒缩短
        • chromosomal perturbation染色体微扰
        • actvation of oncogenes
      • initiated cell走两条路
        • 1.p53 pathway、p16/pRB pathway在起效用
          • 细胞衰老，衰老的细胞
            • in the young: cancer prevention
            • in the elderly: organismal aging
        • 2.上面两个路径失效，且有additional oncogenic stress
          • bypass绕过 of senscence
            • malignant transformation
    • 首次描述：the Hayflick limit
      • • 没有虚线的部分是正常细胞系
        • 虚线以后的无限增值是意外
          • Germ line 生殖细胞系
          • Early embryonic cells (stem cells)
          • Many tumor cells
          • 看一下ppt37、38关于WI-38的介绍
            • 第一个无限增殖的正常人类细胞
    • when cells exhaust their replicative life span，it will happen：
      • replicative senescence
        • Irreversible arrest不可逆终止 of cell proliferation (universal)
        • Resistance to apoptosis (stem cells)
        • Altered function功能改变 (universal but cell type specific)
    • Cellular Senescence： An important tumor suppressor mechanism
      • Induced by potentially oncogenic events
      • Most tumor cells are immortal
      • Many oncogenes act by allowing cells to bypassthe senescence response
      • Senescence is controlled by the two most important tumor suppressor genes -- p53 and pRB
    • Ras and senescence
      • Oncogene-induced senescence
      • 细胞老化的特征
        • 老化的细胞在型态上比正常的细胞大
        • 包内空泡状结构增多
        • 细胞停止复制DNA
        • 细胞內的SA-β-galactosidase活性上升，若以beta-gal染色，细胞呈现蓝色 senescence-associated heterochromatic foci (SAHF) 阳性
      • Ras（V12） induce premature提前 senescence in primary fibroblasts
        • 两种可能
          • Ras（V12）
            • 在primary fibroblast中：p16,p19ARF,p53,p21---premature senescence
            • 在immortal fibroblast中：deficiency缺乏 for INK4a,p19ARF or p53;or expressig E1A, c-Myc---eacape from senescence&oncogenic transformation
        • Oncogenic ras Provokes激起 Premature Cell Senescence Associated with Accumulation of p53 and p16INK4a
          • 染色方法：β-gal staining
            • 发现IMR90、MEF、REF52也跟这条路径有关系
        • 两条路径
          • The p16-cyclin D-pRb-E2F pathway.
          • The p53 pathway.
          • Both pathways are frequently deregulated in human cancer and regulate the cell cycle machinery机制 directly.
    • The mammalian cell cycle
      • The retinoblastastoma gene
        • 定义：A tumor suppressor gene located on chromosome 13q14 that is mutated in many forms of cancer
        • Encodes a growth-inhibitory phosphoprotein:pRb
          • 清除掉ppt49的疑问
        • Cell cycle regulated phosphorylation of the retinoblastoma protein
      • Cell Cycle Problems
        • • 正常状态：p16与CycD-CDK4结合，使得该激酶没有活性；p16离去后，CycD-CDK4有活性，使得Rb-E2F分离，Rb被磷酸化为Rb-3P
          • Rb-E2F：Repressor of transcription of proteins required for DNA synthesis
          • E2F:Activator of transcription of proteins needed for DNA synthesis
        • 问题
          • Over expression of Cyclin D
          • Loss of p16 function
          • Loss of Rb function
    • 重要路径（必考）
      • • 一些外界激活因素：tumor suppressors inactivation/oncogenes activation/ telomere dysfunction端粒功能紊乱/radiation辐射/chemotherapy/other factors
          • p19ARF抑制Mdm2，Mdm2抑制p53；但是p53会反过来促进Mdm2
            • p53导致衰老
            • p53激活p21，p21抑制Cyclin E/cdk2；Cyclin E/cdk2会抑制Rb
          • p16Ink4a抑制Cyclin D/cdk4,6；Cyclin D/cdk4,6抑制Rb
            • Rb抑制E2F
            • Rb促进衰老
    • Functional screen for rescue of Ras-induced senescence
    • 休眠：进化上保守的抗死亡机制
      • 线虫应对饥饿高温等应激时发生休眠
      • 肿瘤转移中的休眠现象
      • 细菌、真菌在遭遇应激刺激时进入休眠
• 间充质上皮转化蛋白（MET）是一种受体酪氨酸激酶
• 根源：肿瘤抗细胞死亡
• 癌症三大谜团
  • 药物耐受
  • 肿瘤转移
  • 非肿瘤组织作用