乳腺癌耐药蛋白的研究进展

乳腺癌耐药蛋白 (BCRP)是新近发现的一种肿瘤耐药相关蛋白 ,与P gp和多药耐药相关蛋白 (MRP)同属ABC转运蛋白超家族。本文对BCRP的发现、基因转染、结构特点、组织表达和临床意义等方面研究进展进行综述。     

p57^kip2与肿瘤

p57^kip2基因的编码产物是一种广泛的细胞周期蛋白依赖性激酶(CDK)的抑制蛋白。它通过调控细胞周期进程，参与肿瘤细胞的增殖、分化与凋亡。在多种肿瘤中均发现p57^kip2基因表达异常，且在某些肿瘤中是一种独立的预后因素，与肿瘤的发生、发展及预后有着密切关系。     

p57kip2与肿瘤

p57kip2基因的编码产物是一种广泛的细胞周期蛋白依赖性激酶(CDK)的抑制蛋白.它通过调控细胞周期进程,参与肿瘤细胞的增殖、分化与凋亡.在多种肿瘤中均发现p57kip2基因表达异常,且在某些肿瘤中是一种独立的预后因素,与肿瘤的发生、发展及预后有着密切关系.     

p53基因与大肠癌

自1979年Lane等SV40感染的小鼠细胞中发现p53基因以来,人们对p53基因的认识经历了：癌蛋白抗原、癌基因、抑癌基因三个阶段。近几年来,人们对p53基因在大肠癌的发生、转移及预后上的意义十分重视。现就p53基因的结构、D53蛋白功能的研究现状及其与大肠癌的关系作一简要综述：     

赖氨酰氧化酶样蛋白2与肿瘤的相关性及作用机制

 赖氨酰氧化酶样蛋白2（LOXL2）是赖氨酰氧化酶（LOX）家族成员之一。目前,大多数学者认为LOXL2是一种促进转移基因,也有一些认为是肿瘤抑制基因。研究发现LOXL2与多种基因联合协同作用,促进肿瘤侵袭、转移,且与不良预后相关,相关研究为判断肿瘤的转移和预后及寻找肿瘤治疗的新靶点提供了新思路。     

着丝粒蛋白F与恶性肿瘤的关系

着丝粒蛋白F（CENP-F）是细胞周期依赖性的着丝粒蛋白,其表达和定位具有严格的细胞周期性。CENP-F在肿瘤发生中起重要作用。CENP-F在多种肿瘤中表达上调,是重要的细胞增殖标志物,研究显示与肿瘤的发生、发展、侵袭、复发与预后等相关,是一个有价值的肿瘤预后指标和潜在治疗靶点。     

高迁移率蛋白A2在肿瘤中的表达及作用机制

高迁移率蛋白A2(HMGA2)是一种非组蛋白染色质相关蛋白,其AT-钩结构能够特异性结合特定的DNA序列,主要功能是作为致癌基因和结构转录因子.HMGA2几乎在所有类型的恶性肿瘤中表达,与肿瘤的形成、发展以及不良预后密切相关.HMGA2在各个生物过程,包括细胞增殖、细胞周期、干细胞自我更新、上皮间质转化及DNA损伤修复中都起到了重要作用.深入研究高迁移率蛋白A2对肿瘤的影响及其作用机制具有重大意义.     

多药耐药蛋白-P-gp的研究进展

多药耐药(MDR)表现为肿瘤细胞对多种结构不同、靶位元不同、作用方式不同的抗肿瘤药物，具有抵抗性。近年来研究发现，主要有两种基因表达与人类肿瘤细胞上的多药耐药表现有关，一种是多药耐药基因(Multidrug Resistance Gene 1 MDR1)，即编码分子量为170KD的跨膜糖蛋白P-gp(P-glycoprotein)；另一种是多药耐药相关蛋白(Multidrug Related     

survivin与肺癌关系的研究进展

细胞凋亡是一种基因控制的细胞程序性死亡现象，在细胞分化、生长和稳定正常内环境中起着重要的作用，与肿瘤的发生、发展也有着密不可分的关系。凋亡抑制蛋白（inhibitorofapoptosisprotein,IAP）是继Bcl-2家族后发现的又一类凋亡调控蛋白家族。survivin是该家族中分子量最小的一个成员。     

P53蛋白的结构、功能和作用机制

近年来的研究显示,P53基因与多种人体肿瘤有关。P53基因是一个单拷贝基因,其基因产物是一种核蛋白。半衰期较短。最初的研究发现,P53蛋白能与多种DNA病毒蛋白结合,在肿瘤和转化细胞中常有高表达;P53基因具有使原代大鼠细胞永生化,和ras癌基因一起使大鼠成纤维细胞转化的能力,认为P53基因是典型的癌基因。但近几年的研究发现,起癌基因作用的是P53基因突变体,     

Increased EGFR expression induced by a novel oncogene,CUG2, confers resistance to doxorubicin through Stat1-HDAC4 signaling

Background

Previously, it has been found that the cancer upregulated gene 2 (CUG2) and the epidermal growth factor receptor (EGFR) both contribute to drug resistance of cancer cells. Here, we explored whether CUG2 may exert its anticancer drug resistance by increasing the expression of EGFR.

Methods

EGFR expression was assessed using Western blotting, immunofluorescence and capacitance assays in A549 lung cancer and immortalized bronchial BEAS-2B cells, respectively, stably transfected with a CUG2 expression vector (A549-CUG2; BEAS-CUG2) or an empty control vector (A549-Vec; BEAS-Vec). After siRNA-mediated EGFR, Stat1 and HDAC4 silencing, antioxidant and multidrug resistance protein and mRNA levels were assessed using Western blotting and RT-PCR. In addition, the respective cells were treated with doxorubicin after which apoptosis and reactive oxygen species (ROS) levels were measured. Stat1 acetylation was assessed by immunoprecipitation.

Results

We found that exogenous CUG2 overexpression induced EGFR upregulation in A549 and BEAS-2B cells, whereas EGFR silencing sensitized these cells to doxorubicin-induced apoptosis. In addition, we found that exogenous CUG2 overexpression reduced the formation of ROS during doxorubicin treatment by enhancing the expression of antioxidant and multidrug resistant proteins such as MnSOD, Foxo1, Foxo4, MRP2 and BCRP, whereas EGFR silencing congruently increased the levels of ROS by decreasing the expression of these proteins. We also found that EGFR silencing and its concomitant Akt, ERK, JNK and p38 MAPK inhibition resulted in a decreased Stat1 phosphorylation and, thus, a decreased activation. Since also acetylation can affect Stat1 activation via a phospho-acetyl switch, HDAC inhibition may sensitize cells to doxorubicin-induced apoptosis. Interestingly, we found that exogenous CUG2 overexpression upregulated HDAC4, but not HDAC2 or HDAC3. Conversely, we found that HDAC4 silencing sensitized the cells to doxorubicin resistance by decreasing Stat1 phosphorylation and EGFR expression, thus indicating an interplay between HDAC4, Stat1 and EGFR.

Conclusion

Taken together, we conclude that CUG2-induced EGFR upregulation confers doxorubicin resistance to lung (cancer) cells through Stat1-HDAC4 signaling.

     

JMJD2B蛋白结构功能及在恶性肿瘤发生发展中的研究进展

JMJD家族是一类重要的组蛋白去甲基化酶,JMJD2B(Jumonji domain containing 2B)属于其成员之一,是含有JmjC结构域的JMJD。主要调节染色质结构、转录和细胞表观状态。近期国内外研究表明JMJD2B蛋白在人类恶性肿瘤组织中高表达,如肝癌、胃癌、乳腺癌、肾癌、皮肤癌等,而且在恶性肿瘤的发生、发展、迁移、浸润以及扩散等不同环节都展现出关键的影响。     

Cancer-associated alteration of pericentromeric heterochromatin may contribute to chromosome instability

Many tumors exhibit elevated chromosome mis-segregation termed chromosome instability (CIN), which is likely to be a potent driver of tumor progression and drug resistance. Causes of CIN are poorly understood but probably include prior genome tetraploidization, centrosome amplification and mitotic checkpoint defects. This study identifies epigenetic alteration of the centromere as a potential contributor to the CIN phenotype. The centromere controls chromosome segregation and consists of higher-order repeat (HOR) alpha-satellite DNA packaged into two chromatin domains: the kinetochore, harboring the centromere-specific H3 variant centromere protein A (CENP-A), and the pericentromeric heterochromatin, considered important for cohesion. Perturbation of centromeric chromatin in model systems causes CIN. As cancer cells exhibit widespread chromatin changes, we hypothesized that pericentromeric chromatin structure could also be affected, contributing to CIN. Cytological and chromatin immunoprecipitation and PCR (ChIP-PCR)-based analyses of HT1080 cancer cells showed that only one of the two HORs on chromosomes 5 and 7 incorporate CENP-A, an organization conserved in all normal and cancer-derived cells examined. Contrastingly, the heterochromatin marker H3K9me3 (trimethylation of H3 lysine 9) mapped to all four HORs and ChIP-PCR showed an altered pattern of H3K9me3 in cancer cell lines and breast tumors, consistent with a reduction on the kinetochore-forming HORs. The JMJD2B demethylase is overexpressed in breast tumors with a CIN phenotype, and overexpression of exogenous JMJD2B in cultured breast epithelial cells caused loss of centromere-associated H3K9me3 and increased CIN. These findings suggest that impaired maintenance of pericentromeric heterochromatin may contribute to CIN in cancer and be a novel therapeutic target.     

免疫电镜方法研究P-gp、p53蛋白、Bcl-2蛋白在肺癌组织中的表达

目的 从超微水平了解P－gp、p53蛋白、Bcl-2蛋白在肺癌组织中的表达，探讨它们与多药耐药（multidrug resistance,MDR)的关系和可能的作用机制。方法 8例非小细胞肺癌（NSCLC）手术标本和7例小细胞肺癌（SCLC）经支气管镜活检标本，用免疫电镜方法包埋后，以PAG标记抗体方法检测P－gp、p53蛋白、Bcl-2蛋白的表达。结果 P－gp主要位于胞膜和胞浆内质网附近；p53主要位于细胞核异染色质上，胞浆中也有存在；Bcl-2分布与线粒体和内质网有关。三者在15例肺癌中的表达率分别为33．3％（5／15）、60．0％（9／15）和26．7％（4／15）。8例手术获得的正常肺组织标本中，3种蛋白表达均为阴性。5例P－gp阳性的标本中，4例为NSCLC，仅1例为化疗后的SCLC。结论 用免疫电镜方法检测，P－gp、p53蛋白、Bcl-2蛋白在肺癌中有一定的表达。P－gp与p53、p53与Bcl-2的表达无相关性。P－gp主要位于胞膜，支持其膜上药物输出泵的功能，其表达在肺癌的MDR中起一定作用，但不是惟一因素。     

Periostin: A Novel Prognostic and Therapeutic Target For Genitourinary Cancer?

Many of the cellular abnormalities present in solid tumors are structural in nature and involve the proteins of the extracellular matrix (ECM). Periostin is a protein produced and secreted by the fibroblasts as a component of the ECM where it is involved in regulating intercellular adhesion. The expression of periostin has an important physiological role during embryogenesis and growth, namely at the level of bone, dental, and cardiac tissues. Many studies indicate that periostin plays an important role for tumor progression in various types of cancer, such as colon, lung, head and neck, breast, ovarian, and prostate. To the best of our knowledge, a limited number of studies have investigated periostin expression in urogenital cancer, such as prostate, bladder, penile, and renal cancer, and no studies were performed in testis cancer. In this review article, we summarize the most recent knowledge of periostin, its genetic and protein structure, and the role of the different isoforms identified and sequenced so far. In particular, we focus our attention on the role of this protein in genitourinary tumors, trying to emphasize the role not only as a possible prognostic marker, but also as a possible target for the development of future anticancer therapies.     

Prothymosin‐α enhances phosphatase and tensin homolog expression and binds with tripartite motif‐containing protein 21 to regulate Kelch‐like ECH‐associated protein 1/nuclear factor erythroid 2‐related factor 2 signaling in human bladder cancer

Prothymosin‐α (PTMA) is a small, acidic protein that is usually transported into the nucleus and involves many cellular and immunological functions. Previous studies demonstrated that aberrant location of PTMA expression exists in human bladder cancer, but the role of PTMA protein expression remains elusive. In this study, we created ectopic nuclear or cytoplasmic PTMA expression in human bladder cancer cells by infecting lentiviruses carrying wild type or deleted nuclear localization signal of the PTMA gene. The in vivo tumorigenesis assay showed PTMA protein with deleted nuclear localization signal promotes J82 xenograft tumor growth in mice and shortens their survival more so than the wild type. Chromatin immunoprecipitation showed that wild‐type PTMA protein binds to the PTEN promoter and enhances phosphatase and tensin homolog (PTEN) expression. Through immunoblot proteomics and in vivo ubiquitination studies, PTMA protein can bind with tripartite motif‐containing protein 21 (TRIM21) and block its ubiquitination. Also, TRIM21 can downregulate both forms of PTMA protein. In human bladder tumors, loss of nuclear PTMA expression was an unfavorable prognostic indicator for shorter disease‐free survival (hazard ratio, 1.54; P = 0.009). Our data support that nuclear PTMA protein serves as a tumor suppressor in bladder cancer through upregulating PTEN and orchestrating TRIM21 for the regulation of Nrf2 signaling.     

Low-level TOP2A amplification in prostate cancer is associated with HER2 duplication, androgen resistance, and decreased survival

HER2 and TOP2A genes, located on 17q, can be coamplified in cancer. Overexpression of both genes has been reported in high-grade, androgen-resistant prostate cancer. Both genes have not been compared in a single prostate cancer study and the frequency of TOP2A amplifications in prostate cancer is unknown. Using tissue microarrays, we did immunohistochemistry and fluorescence in situ hybridization for HER2 and TOP2A in 100 prostate cancers (41 localized and 59 advanced) and 42 cases of benign prostatic hyperplasia (BPH). Amplification was defined as a target/centromere signal ratio of > or =1.5. HER2 immunohistochemistry was scored from 0 to 3+. Percentage nuclei staining for topoisomerase IIalpha (topoIIalpha) was recorded; overexpression was defined as > or =5% cells staining. Eighteen (31%) advanced prostate cancers showed topoIIalpha overexpression; 12 (26%) showed TOP2A low-level amplification; 9 (16%) expressed HER2; and 6 (13%) showed HER2 low-level amplification. No high-level amplification of either gene (target/centromere signal ratio of > or =3.0) was detected. TOP2A coexpression and coamplification were seen in 75% and 66% of HER2-positive cases, respectively. Localized prostate cancer or BPH showed no gene amplification or topoIIalpha overexpression. Gene amplification or overexpression correlated with high stage and Gleason score. The presence of TOP2A amplification in advanced cancer was associated with androgen resistance and decreased survival by multivariate analysis. This is the first study to document low-level TOP2A amplification in prostate cancer and an association with reduced survival. TOP2A amplification may occur with or without HER2 duplication and is often associated with topoIIalpha expression. Therapies directed against topoIIalpha (and HER2) in such patients may improve survival.     

Activation of Ca(2+)-dependent proteolysis in skeletal muscle and heart in cancer cachexia

Cachexia is a syndrome characterized by profound tissue wasting that frequently complicates malignancies. In a cancer cachexia model we have shown that protein depletion in the skeletal muscle, which is a prominent feature of the syndrome, is mostly due to enhanced proteolysis. There is consensus on the views that the ubiquitin/proteasome pathway plays an important role in such metabolic response and that cytotoxic cytokines such as TNFalpha are involved in its triggering (Costelli and Baccino, 2000), yet the mechanisms by which the relevant extracellular signals are transduced into protein hypercatabolism are largely unknown. Moreover, little information is presently available as to the possible involvement in muscle protein waste of the Ca(2+)-dependent proteolysis, which may provide a rapidly activated system in response to the extracellular signals. In the present work we have evaluated the status of the Ca(2+)-dependent proteolytic system in the gastrocnemius muscle of AH-130 tumour-bearing rats by assaying the activity of calpain as well as the levels of calpastatin, the natural calpain inhibitor, and of the 130 kDa Ca(2+)-ATPase, both of which are known calpain substrates. After tumour transplantation, total calpastatin activity progressively declined, while total calpain activity remained unchanged, resulting in a progressively increasing unbalance in the calpain/calpastatin ratio. A decrease was also observed for the 130 kDa plasma membrane form of Ca(2+)-ATPase, while there was no change in the level of the 90 kDa sarcoplasmic Ca(2+)-ATPase, which is resistant to the action of calpain. Decreased levels of both calpastatin and 130 kDa Ca(2+)-ATPase have been also detected in the heart of the tumour-bearers. These observations strongly suggest that Ca(2+)-dependent proteolysis was activated in the skeletal muscle and heart of tumour-bearing animals and raise the possibility that such activation may play a role in sparking off the muscle protein hypercatabolic response that characterizes cancer cachexia.     

HER-2/neu oncogene amplification and chromosome 17 aneusomy in endometrial carcinoma: correlation with oncoprotein expression and conventional pathological parameters

The objective of the present study was to evaluate the correlation between HER-2 gene amplification and HER-2 protein overexpression in endometrial carcinoma using fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC). We also analyzed chromosome 17 aneusomy and the association between these biological parameters and conventional clinicopathological variables. FISH analysis was performed on 73 selected paraffin-embedded sections from endometrial carcinomas which previously had HER-2 status determined immunohistochemically using monoclonal antibodies (MoAb) 300G9 and CB11. Using a ratio of more than two oncogene signals/centromere to indicate amplification, a total of 42 out of the 73 endometrial tumors included in this study resulted positive by FISH where as protein overexpression was identified in 29 out of 73 with a concordance rate of 74.3%. However, when the mean signals/centromere per nucleus increased (ratio > 4 < or = 5) a higher concordance between the two assays was seen (p = 0.007). In addition, HER-2 amplification was significantly correlated with tumor stage (p = 0.021) and myometrial invasion (p = 0.010), whereas chromosome 17 polisomy showed a positive correlation only with myometrial invasion (p = 0.004) No significant correlation was found between HER-2 gene amplification, chromosome 17 aneusomy and patient outcome. Nevertheless, the probability of a 5 year overall survival decreased from 70% to 43%, respectively, for ratio > 2 < or = 4 and ratio > 4 < or = 5 when we grouped the amplified cases on the basis of HER-2:CEP17 ratio. In conclusion, molecular characteristics provide objective data that may be useful in predicting prognosis in patients with endometrial cancer.