Genetic factors predisposing to the development of papillary thyroid cancer

According to classic theory of neogenesis, cancer arises from well-differentiated cell that in response to variety of factors de-differentiates, becomes able to proliferate without control and/or loses its ability to undergo apoptosis. According to another theory, cancers (at least cancers of some organs) originate from stem cells, which "by definition" are poorly differentiated and able to proliferate indefinitely. Therefore a lower number of abnormal events is necessary for these cells to escape proliferation-controlling mechanisms. With regard to papillary thyroid cancers it is still thought that it arises from well-differentiated thyreocyte. One of the characteristic features of cancer cell is chromosomal instability. Lowest number of such abnormalities is observed in well-differentiated thyroid cancers (including papillary cancer), intermediate - in poorly-differentiated cancers, while highest - in anaplastic cancers. Microarray analysis shows that despite of clinical heterogeneity, gene expression profiles of papillary cancers are very similar. Genetic anomalies predisposing to the development of papillary cancer most commonly regard proteins that possess kinase activity. Kinases phosphorylate other proteins, and play an extremely important role in signal transduction from outside the cell as well as inside the cell. Constitutive activation of some kinases may lead to the excessive and/or permanent activation of some transduction pathways specific for mitogens or growth factors. This results in excessive proliferation. The best known protein of such type which function is altered in papillary thyroid cancers is RET - a membrane-located growth factor-receptor with kinase activity. RET gene undergoes different rearrangements in this type of cancer. There are approximately 10 RET rearrangements known, with RET/PTC3 and RET/PTC1 being most common. In this anomaly kinase domain-encoding 3' end of RET gene is aberrantly bound to 5' end of another gene. Fusion protein synthesized on such hybrid template is not present in the cell membrane but in the cytoplasm, where it permanently activates transduction pathway specific for RET. NTRK1 gene encoding a member of family of neuronal growth factor receptors containing thyrosine kinase domain is also rearranged in papillary cancers. However, genes fused to its kinase domain-encoding sequence are different from the ones fused to RET. MET, a gene encoding another membrane protein with thyrosine kinase activity, which acts as a growth factor-receptor, is overexpressed in 70%-90% of papillary thyroid cancers. BRAF gene encoding another yet kinase transducing signals from RAS and RAF to the cell is mutated at position 1796 (T/A, amino acid substitution V599E) in 38-69% of papillary cancers. The presence of this activatory mutation is associated with higher degree of clinical advancement of the disease. In addition, in majority of papillary cancers tested, mutations of the genes encoding nuclear triiodothyronine receptors were found. Transgenic mice with both TRB allele replaced with dominant-negative TRB mutants develop aggressive thyroid cancers. Progression from papillary to anaplastic cancer is most possibly caused by the occurrence of additional anomalies within P53, RAS, NM23,b-catenin gene and other genes.     

Differential gene expression profiling of human epidermal growth factor receptor 2-overexpressing mammary tumor

Human epidermal growth factor receptor 2 (HER2) is highly expressed in approximately 30% of breast cancer patients, and substantial evidence supports the relationship between HER2 overexpression and poor overall survival. However, the biological function of HER2 signal transduction pathways is not entirely clear. To investigate gene activation within the pathways, we screened differentially expressed genes in HER2-positive mouse mammary tumor using two-directional suppression subtractive hybridization combined with reverse dot-blotting analysis. Forty genes and expressed sequence tags related to transduction, cell proliferation/growth/apoptosis and secreted/extracellular matrix proteins were differentially expressed in HER2-positive mammary tumor tissue. Among these, 19 were already reported to be differentially expressed in mammary tumor, 11 were first identified to be differentially expressed in mammary tumor in this study but were already reported in other tumors, and 10 correlated with other cancers. These genes can facilitate the understanding of the role of HER2 signaling in breast cancer.     

Targeting the FLICE Inhibitory Protein (FLIP) in cancer therapy

In some cases, treatment of ovarian cancer cells with tumor necrosis factor-alpha can induce an apoptotic signal leading to the death of these cells; however, many ovarian malignancies are resistant to the effects of TNF-alpha. A new publication describes how these ovarian tumors may evade death receptor-mediated apoptosis. Apparently, the extracellular signals transduced by death receptors (e.g., TNF receptors) are extinguished before the cascade of caspases, which proteolytically cleave other proteins, can be activated. Overexpression of FLIP, a protein that blocks the caspase activity of FLICE, mediates the observed resistance. Thus, FLIP, which normally prevents inappropriate apoptosis, may become a tumor progression factor. Strategies to overcome this FLIP-mediated blockade of programmed cell death in tumors might become useful for positive prognoses.     

Role of cell-cycle regulators in lung cancer

Lung cancer is the leading cause of cancer death worldwide. Histologically, 80% of lung cancers are classified as non-small-cell lung cancer (NSCLC), and the remaining 20% as small-cell lung cancer (SCLC). Lung carcinoma is the result of molecular changes in the cell, resulting in the deregulation of pathways controlling normal cellular growth, differentiation, and apoptosis. This review summarizes some of the most recent findings about the role of cell-cycle proteins in lung cancer pathogenesis and progression.     

Apoptosis in the development of the immune system

Apoptosis is a conserved genetic program critical for the development and homeostasis of the immune system. During the early stages of lymphopoiesis, growth factor signaling is an essential regulator of homeostasis by regulating the survival of lymphocyte progenitors. During differentiation, apoptosis ensures that lymphocytes express functional antigen receptors and is essential for eliminating lymphocytes with dangerous self-reactive specificities. Many of these critical cell death checkpoints during immune development are regulated by the BCL-2 family of proteins, which is comprised of both pro- and antiapoptotic members, and members of the tumor necrosis factor death receptor family. Aberrations in the expression or function of these cell death modulators can result in pathological conditions including immune deficiency, autoimmunity, and cancer. This review will describe how apoptosis regulates these critical control points during immune development.     

植物多酚的防癌抗癌作用

植物多酚是植物中广泛存在的一大类多酚化合物的总称,包括多酚（如单宁）、黄酮、酚酸等。体外实验研究表明植物多酚对多种人癌细胞具有增殖抑制作用,抑制动物体内肿瘤生长。其作用机理与抗氧化、调控细胞周期、诱导肿瘤细胞凋亡和分化、影响血管生成和肿瘤细胞信号传导等有关。对植物多酚的防癌抗癌作用,值得进一步深入研究。     

Detection of altered retinoic acid receptor expression in tissue sections using in situ hybridization

Nuclear retinoid receptors mediate retinoid effects in controlling cell growth, differentiation, apoptosis, and carcinogenesis. Altered expression or activity of these receptors could abolish the retinoid signal transduction pathway and be associated with human carcinogenesis. In situ hybridization is a powerful tool for analyzing gene expression in formalin-fixed, paraffin-embedded tissue sections, especially for newly cloned genes or when no antibodies are available. Detection of altered retinoid receptor expression using in situ hybridization in premalignant and malignant tissues has provided important information about the roles of these receptors in cancer development and the response of these tissues to retinoid treatment. Among these receptors, altered expression of retinoic acid receptor-beta (RAR-beta) has been mostly detected in human cancers, including those of the head and neck, lung, esophagus, mammary gland, pancreas, and cervix. RAR-beta is thus currently used as a surrogate endpoint biomarker in different clinical prevention trials of various cancers.     

p63 and p73: roles in development and tumor formation

The tumor suppressor p53 is critically important in the cellular damage response and is the founding member of a family of proteins. All three genes regulate cell cycle and apoptosis after DNA damage. However, despite a remarkable structural and partly functional similarity among p53, p63, and p73, mouse knockout studies revealed an unexpected functional diversity among them. p63 and p73 knockouts exhibit severe developmental abnormalities but no increased cancer susceptibility, whereas this picture is reversed for p53 knockouts. Neither p63 nor p73 is the target of inactivating mutations in human cancers. Genomic organization is more complex in p63 and p73, largely the result of an alternative internal promoter generating NH2-terminally deleted dominant-negative proteins that engage in inhibitory circuits within the family. Deregulated dominant-negative p73 isoforms might play an active oncogenic role in some human cancers. Moreover, COOH-terminal extensions specific for p63 and p73 enable further unique protein-protein interactions with regulatory pathways involved in development, differentiation, proliferation, and damage response. Thus, p53 family proteins take on functions within a wide biological spectrum stretching from development (p63 and p73), DNA damage response via apoptosis and cell cycle arrest (p53, TAp63, and TAp73), chemosensitivity of tumors (p53 and TAp73), and immortalization and oncogenesis (DeltaNp73).     

Molecular Validation of PACE4 as a Target in Prostate Cancer

Prostate cancer remains the single most prevalent cancer in men. Standard therapies are still limited and include androgen ablation that initially causes tumor regression. However, tumor cells eventually relapse and develop into a hormone-refractory prostate cancer. One of the current challenges in this disease is to define new therapeutic targets, which have been virtually unchanged in the past 30 years. Recent studies have suggested that the family of enzymes known as the proprotein convertases (PCs) is involved in various types of cancers and their progression. The present study examined PC expression in prostate cancer and validates one PC, namely PACE4, as a target. The evidence includes the observed high expression of PACE4 in all different clinical stages of human prostate tumor tissues. Gene silencing studies targeting PACE4 in the DU145 prostate cancer cell line produced cells (cell line 4-2) with slower proliferation rates, reduced clonogenic activity, and inability to grow as xenografts in nude mice. Gene expression and proteomic profiling of the 4-2 cell line reveals an increased expression of known cancer-related genes (e.g., GJA1, CD44, IGFBP6) that are downregulated in prostate cancer. Similarly, cancer genes whose expression is decreased in the 4-2 cell line were upregulated in prostate cancer (e.g., MUC1, IL6). The direct role of PACE4 in prostate cancer is most likely through the upregulated processing of growth factors or through the aberrant processing of growth factors leading to sustained cancer progression, suggesting that PACE4 holds a central role in prostate cancer.     

支架蛋白Gab2信号调控与乳腺癌

Gab2是支架蛋白Gabs家族中的重要成员.该家族蛋白通过介导膜受体与信号转运蛋白间的偶联及各信号分子间的整合参与信号传导.作为支架蛋白,Gab2可被酪氨酸激酶磷酸化激活,接受胞外多种因子刺激,招募富含SH2结构域的信号转运分子,活化下游SHP2/Ras/ERK和PI3K/AKT等一系列信号传导途径,在细胞增殖、分化、...     

Epidermal growth factor induced apoptosis

Apoptosis, or programmed cell death, plays an important role in the pathogenesis of a number of human diseases, including cancers, autoimmune diseases, and neurodegenerative disorders. Recent evidence suggests that EGF induced signal transduction pathways which govern cell proliferation and cell cycle progression also mediate antiproliferative effects leading to increased apoptosis in cells that express high levels of epidermal growth factor receptors. Treatments designed to increase apoptosis have potential to change the natural progression of cancer and eventually lead to its successful control.