抑癌基因的负转录调控

抑癌基因在正常细胞中适度表达,抑制细胞永生及转化,其转录下调见于某些肿瘤,而在衰老细胞中常见表达上调或活性增强。抑癌基因INK4a／ARF、p53和p21^Cipl的表达及其负调控与肿瘤及细胞衰老的关系十分密切。     

Detection of Mutations in Tumor Suppressor Genes

Defects in vital genes occur in a high percentage of human diseases, including cancer. Defects could be due to the accumulation of mutations in the genes leading to the production of faulty proteins. Although the biological significance of such mutant proteins still remains in question, recent experiments have demonstrated that genes overproducing faulty proteins are often associated with tumor cell growth. Thep53tumor suppressor gene is the most frequently mutated gene yet identified in human cancer. It is mutated in wide variety of human cancers. Missense mutations are common for thep53gene and are essential for the transforming ability of the oncogene. The wild-typep53gene may directly suppress cell growth or indirectly activate genes that are involved in growth suppression. Thus inactivation of wild-typep53by point mutation may contribute to transformation. Therefore, identification of such mutations have potential clinical implications. Recently, polymerase chain reaction-based advanced molecular techniques had a profound impact on the detection and identification of such mutations. These techniques are sensitive and quantitative tools for the study of the pathogenesis of neoplastic diseases at the single-cell level.     

Evergreen Foliage Contributions to the Spring Growth of Taxus

Taxus media cv. Hicksii plants were grown one season under a low and high level of nitrogen fertilization. Before growth in the spring the plants were divided into two groups, one of which was defoliated and the other left intact. The growth and spring utilization of the nitrogen and carbohydrate reserves of defoliated plants were compared to the intact plants 0, 2, 4 and 6 weeks after growth started in the spring. The plants were separated into buds (all new growth), roots and stems and analyzed for changes in total nitrogen, basic and non-basic amino acids, hemicelluloses, soluble sugars, organic acids and chlorophyll. The older evergreen needles from plants grown under low nitrogen levels contain 20 % of the carbohydrate and 24% of the nitrogen used in spring growth. The needles from plants grown under high nitrogen levels contained 56% of the carbohydrate and 49% of the nitrogen used in spring growth. Removal of the old needles before spring growth removed this nitrogen and carbohydrate reserve and reduced the total plant chlorophyll content after 6 weeks of growth to 50% of that found in intact plants, with the result that defoliated plants did not show a growth response to nitrogen. Amino acids accumulated in the stems and buds of defoliated plants as carbohydrates became limiting. The defoliated plants removed 25% more available carbohydrates from the roots and stems than intact plants and their buds contained 50% less available carbohydrates. Plants without old needles showed similar growth rates under low and high nitrogen regimes and produced 33% of the dry weight of intact plants grown under high nitrogen levels and 66% of the dry weight of intact plants grown under low nitrogen levels. The old needles of taxus plants contain substantial amounts of reserve nitrogen and carbohydrate and these needles greatly influence the extent and rapidness of growth in the spring. When the needles are removed, the other tissues can supply an adequate amount of nitrogen but the carbohydrate supply becomes limiting for spring growth.     

Fastest Time to Cancer by Loss of Tumor Suppressor Genes

Genetic instability promotes cancer progression (by increasing the probability of cancerous mutations) as well as hinders it (by imposing a higher cell death rate for cells susceptible to cancerous mutation). With the loss of tumor suppressor gene function known to be responsible for a high percentage of breast and colorectal cancer (and a good fraction of lung cancer and other types as well), it is important to understand how genetic instability can be orchestrated toward carcinogenesis. In this context, this paper gives a complete characterization of the optimal (time-varying) cell mutation rate for the fastest time to a target cancerous cell population through the loss of both copies of a tumor suppressor gene. Similar to the (one-step) oncogene activation model previously analyzed, the optimal mutation rate of the present two-step model changes qualitatively with the convexity of the (mutation rate-dependent) cell death rate. However, the structure of the Hamiltonian for the new model differs significantly and intrinsically from that of the one-step model, and a completely new approach is needed for the solution of the present two-step problem. Considerable insight into the biology of optimal switching (between corner controls) is extracted from numerical results for cases with nonconvex death rates.     

肝细胞癌中抑癌基因的发现与研究进展

肝细胞癌（HCC）的发病率高、治疗效果差。HCC的发病机制复杂,主要有2类：肝炎、酒精、黄曲霉素、代谢紊乱引起的肝损伤,进而导致的肝硬化;致癌基因和抑癌基因的突变或对应染色体区域的扩增或缺失。细胞内一些信号通路参与了HCC的发生发展,包括RAF／MEK／ERK、P13K／AKT／mTOR、WNT/β-catenin、胰岛素样生长因子、肝细胞生长因子／c-MET、生长因子调节的血管新生等6类信号通路。抑癌基因通过调节信号通路而调节细胞增殖、细胞周期、细胞凋亡等对肿瘤的发生、发展起重要作用的过程。我们简要概述HCC相关的肿瘤抑制分子及其所在的信号通路及作用的分子机制。     

A Comparison of Radiologic Tumor Volume and Pathologic Tumor Volume in Renal Cell Carcinoma (RCC)

Objective

To investigate the difference between preoperative radiologic tumor volume (RTV) and postoperative pathologic tumor volume (PTV) in patients who received nephrectomy for renal cell carcinoma (RCC).

Materials and Methods

We reviewed 482 patients who underwent preoperative computed tomography (CT) within 4 weeks before radical or partial nephrectomy for renal cell carcinoma. RTV measured by a three dimensional rendering program was compared with PTV (π/6ⅹheightⅹlengthⅹwidth) measured in surgical specimen according to pathologic tumor size and histologic subtype. Correlation of the inter-quartile range (IQR) of the RTV and Fuhrman nuclear grade was also investigated.

Results

There was a significant positive linear correlation between RTV and PTV (p<0.001, r = 0.911), and the mean RTV and mean PTV were not significantly different (79.0 vs 76.9cm³, p = 0.393). For pathologic tumor size (PTS) <4cm, the mean RTV was larger than the mean PTV (10.9 vs 7.1cm³, p<0.001). For a PTS of 4-7cm, the mean RTV was larger than the mean PTV (56.0 vs 44.7cm³, p<0.001). However, for a PTS ≥7cm, there was no statistical difference between RTV and PTV (p>0.05). Among patients with clear cell RCC, the mean RTV was significantly larger than the mean PTV (p = 0.042), not for non-clear cell group (p = 0.055). As the quartile of the RTV increased, the Fuhrman grade also increased (p<0.001).

Conclusions

RTV was correlated with PTV and pathologic grade. RTV was larger than the PTV for a tumor size 7 cm or less or in clear cell RCC. RTV may be useful to measure tumor burden preoperatively.     

PEDF在肿瘤生长和转移中的作用

色素上皮衍生因子(pigment epithelium-derived factor,PEDF)最早是由胎儿视网膜色素上皮细胞的培养液中分离出来的,属于丝氨酸蛋白酶抑制剂基因家族,但不具备抗蛋白酶活性,其在人体中广泛表达。PEDF是目前已知的人体最强的血管生长抑制因子,是最有希望成为治疗肿瘤和血管增生性疾病的候选基因。虽然PEDF最初被确认为神经细胞分化因子,现在研究发现它还具有营养和保护神经、抑制血管形成、促进肿瘤分化和凋亡等功能,但目前关注更多的却是其抑制新生血管生成的活性。此外,最近的研究表明,PEDF在人体中具有抗肿瘤作用,主要表现在抑制肿瘤的生长和转移,阐明其抑制肿瘤的作用机制对于抗肿瘤的研究具有重要意义。     

The Alteration of MiR-222 and Its Target Genes in Nickel-Induced Tumor

Nickel is an important kind of metal and a necessary trace element in people’s production and livelihood; it is also a well-confirmed human carcinogen. In the past few years, researchers did a large number of studies about the molecular mechanisms of nickel carcinogenesis, and they focused on activation of proto-oncogenes and inactivation of anti-oncogenes caused by gene point mutation, gene deletion, gene amplification, DNA methylation, chromosome condensation, and so on that were induced by nickel. However, the researches on tumorigenic molecular mechanisms regulated by microRNAs (miRNAs) are rare. In this study, we established nickel-induced tumor by injecting Ni₃S₂ compounds to Wistar Rattus. By establishing a cDNA library of miRNA from rat muscle tumor tissue induced by Ni₃S₂, we found that the expression of miR-222 was significantly upregulated in tumor tissue compared with the normal tissue. As we expected, the expression levels of target genes of miR-222, CDKN1B and CDKN1C, were downregulated in the nickel-induced tumor. The same alteration of miR-222 and its target genes was also found in malignant 16HBE cells induced with Ni₃S₂ compounds. We conclude that miR-222 may promote cell proliferation infinitely during nickel-induced tumorigenesis in part by regulating the expression of its target genes CDKN1B and CDKN1C. Our study elucidated a novel molecular mechanism of nickel-induced tumorigenesis.     

Polypeptide Growth Factors in Embryogenesis and Tumor Growth

Polypeptide growth factors belonging to different families (epidermal growth factors, insulin-like growth factors, fibroblast growth factors, transforming growth factors-, and some others), were characterized regarding their specific role in embryogenesis and tumor growth. Differences and parallels in the functioning of growth factors in these processes have been noted. The potential significance of the described characteristics of growth factors for directed modulation of embryogenesis and tumor growth is discussed.     

Contributions of Cell Growth and Biochemical Reactions to Nongenetic Variability of Cells

Cell-to-cell variability in the molecular composition of isogenic, steady-state growing cells arises spontaneously from the inherent stochasticity of intracellular biochemical reactions and cell growth. Here, we present a general decomposition of the total variance in the copy number per cell of a particular molecule. It quantifies the individual contributions made by processes associated with cell growth, biochemical reactions, and their control. We decompose the growth contribution further into variance contributions of random partitioning of molecules at cell division, mother-cell heterogeneity, and variation in cell-cycle progression. The contribution made by biochemical reactions is expressed in variance generated by molecule synthesis, degradation, and their regulation. We use this theory to study the influence of different growth and reaction-related processes, such as DNA replication, variable molecule-partitioning probability, and synthesis bursts, on stochastic cell-to-cell variability. Using simulations, we characterize the impact of noise in the generation-time on cell-to-cell variability. This article offers a widely-applicable theory on the influence of biochemical reactions and cellular growth on the phenotypic variability of growing, isogenic cells. The theory aids the design and interpretation of experiments involving single-molecule counting or real-time imaging of fluorescent reporter constructs.     

Contributions of Cell Growth and Biochemical Reactions to Nongenetic Variability of Cells

Cell-to-cell variability in the molecular composition of isogenic, steady-state growing cells arises spontaneously from the inherent stochasticity of intracellular biochemical reactions and cell growth. Here, we present a general decomposition of the total variance in the copy number per cell of a particular molecule. It quantifies the individual contributions made by processes associated with cell growth, biochemical reactions, and their control. We decompose the growth contribution further into variance contributions of random partitioning of molecules at cell division, mother-cell heterogeneity, and variation in cell-cycle progression. The contribution made by biochemical reactions is expressed in variance generated by molecule synthesis, degradation, and their regulation. We use this theory to study the influence of different growth and reaction-related processes, such as DNA replication, variable molecule-partitioning probability, and synthesis bursts, on stochastic cell-to-cell variability. Using simulations, we characterize the impact of noise in the generation-time on cell-to-cell variability. This article offers a widely-applicable theory on the influence of biochemical reactions and cellular growth on the phenotypic variability of growing, isogenic cells. The theory aids the design and interpretation of experiments involving single-molecule counting or real-time imaging of fluorescent reporter constructs.     

抑癌基因ING家族研究进展

ING家族是近些年才被发现一个侯选肿瘤抑制基因家族,因其家族成员广泛参与基因转录的调控、细胞增殖、凋亡、细胞衰老、接触抑制、DNA损伤修补及抑制血管形成等,和肿瘤的发生发展密切相关而受到关注.     

Analysis of Tumor Suppressor Genes Using Transgenic Mice

Identification and analysis of tumor suppressor genes has relied chiefly upon studies of human sporadic tumors and of tumors harvested from familial cancer syndrome patients. One methodology that is proving to be extremely useful both in analyzing the function of these genes and in identifying new tumor suppressor genes involves the creation of transgenic mice that contain targeted mutations that functionally inactivate tumor suppressor genes. Studies using such mice have provided insight into the role of tumor suppressor genes in cell growth and in embryonic development. The creation of mice that harbor mutations in one or both alleles of a targeted gene has permitted anin vivoanalysis of the tumor suppressing properties of the gene and facilitated investigation of cell cycle control and differentiation of multiple cell lineages within the organism. Sophistication of gene targeting techniques will likely result in the creation of more lines of mice bearing genetic modifications in tumor suppressor genes, permitting an even finer detailed analysis of tumor suppressor gene functions.     

Adenovirus as a System for Delivering and Expressing Tumor Suppressor Genes in Tumor Cells

The strategy for tumor suppressor gene therapy for cancer is to suppress the malignant phenotype of tumor cells by replacing the inactivated gene with a normal (wild-type) one to restore control of cell growth and differentiation. To effectively carry out this strategy, the therapeutic genes must be delivered efficiently and expressed at an adequate level in the tumor. Adenoviral vectors have rapidly developed into one of the major systems now in use to effect this delivery and expression, primarily because of their advantages over other viral vectors, such as their ease of manipulation, their wide host cell range with high infectivity, their relative stability with high obtainable titers (10¹⁰–10¹²plaque-forming units/ml), and their episomal expression with low genotoxicity. Adenoviral vectors are a good technical approach to delivering tumor suppressor genes for cancer therapy; they have demonstrated effectiveness in preclinical animal models. This chapter organizes and describes a series of methods for developing a preclinical model for adenovirus-mediated tumor suppressor gene therapy of cancer. The disadvantages of adenoviral vectors and the possibilities for improving this vector system to enhance tumor suppression efficacy are also discussed.     

转大麻哈鱼生长激素基因鲫鱼研究

通过显微注射方法得到了一批转大麻哈鱼生长激素基因的实验鲫鱼。斑点杂交和ＳｏｕｔｈｅｒｎＢｌｏｔ杂交证实部分实验鱼的基因组中已整合了外源生长激素基因,并有一尾鱼有比较明显的生长速度快的特征。     

肿瘤细胞外泌体中融合基因的检测

目的:探究肿瘤细胞分泌的外泌体中是否可以检测到来源于源细胞的融合基因m RNA。方法:培养人非小细胞肺癌NCI-H3122细胞,采用外泌体试剂盒提取细胞上清中的外泌体,并用Western Blot实验验证外泌体是否提取成功。分别提取外泌体以及H3122细胞中的总RNA,将RNA反转录为c DNA,通过PCR反应扩增v1型EML4-ALK融合基因片段,经琼脂糖凝胶电泳确定目的条带后,将两种PCR产物送公司进行基因测序,最后对测序结果进行比对分析。结果:从H3122细胞上清中成功提取了外泌体,并且在外泌体中检测到来源于H3122细胞的m RNA;从H3122细胞外泌体中检测到EML4-ALK融合基因,并发现外泌体中的EML4-ALK融合基因的融合形式为V1,与在H3122细胞中检测到的EML4-ALK融合基因的融合形式完全相同。结论:肿瘤细胞分泌的外泌体中可以检测到肿瘤细胞来源的m RNA,并且外泌体中的m RNA可以反映肿瘤细胞m RNA的基因融合情况等生物学特性。     

Neurohormonal Regulation of Tumor Growth

Neurohormones vasopressin and oxytocin are synthesized in the hypothalamus and are transported along the axons to the neurohypophysis as a part of equimolar complexes with hormone-specific neurophysins. The tumors of epithelial origin synthesize ectopic vasopressin and have an ability to express all types of receptors of neurohypophysis hormones. Vasopressin and oxytocin receptors provide the transduction of signals to protein kinases A, B, and C and activate intracellular cascades of the CREB, MDM2, and TORC1/2 proteins and mitogen-activated protein kinases. Central endocrine and autocrine neurohormonal contours are involved in the regulation of proliferative, migration, and angiogenic processes accompanied by tumor progression. Tumor growth and development occur in close cooperation with the supporting stroma. The interstitial tissue is involved in signal communication of tumor cells by integrins and integral CD44 glycoproteins formulating hyaluronic acid. Hyaluronic acid metabolites modulate the effect of neurohormones and peptide growth factors; intermediate hyaluronan fragments with molecular weight of approximately 20 kDa elicit the most significant angiogenic effect. Platelets expressing AVPR1 vasopressin receptors are an important source of hyaluronidase 2 hydrolyzing macromolecular hyaluronan to fragments of intermediate length. The AVPR2 receptors localized in endothelium and AVPR1-AVPR2 vasopressin receptors expressing themselves in the tumor cells are involved in the mechanisms controlling local hemostasis. Neurohormonal regulatory contours are involved in optimization of the balance of inducing and inhibiting signals generated by the tumor and stroma in the process of progressive growth.