New concepts on BARD1: Regulator of BRCA pathways and beyond

For nearly two decades most research on BARD1 was closely linked to research on BRCA1, the breast cancer predisposition gene. The co-expression of BARD1 and BRCA1 genes in most tissues, the nearly identical phenotype of Bard1 and Brca1 knock-out mice, and the fact that BRCA1 and BARD1 proteins form a stable complex, led to the general assumption that BARD1 acts as an accessory to BRCA1. More recent research on both proteins showed that BRCA1 and BARD1 might have common as well as separate functions. This review is an overview of how BARD1 functions and controls BRCA1. It highlights also experimental evidence for dominant negative, tumor promoting, functions of aberrant isoforms of BARD1 that are associated with and drivers of various types of cancer.     

Apoptosis pathways in cancer and cancer therapy

Activation of apoptosis pathways is a key mechanism by which cytotoxic drugs kill tumor cells. Also immunotherapy of tumors requires an apoptosis sensitive phenotype of target cells. Defects in apoptosis signalling contribute to resistance of tumors. Activation of apoptosis signalling following treatment with cytotoxic drugs has been shown to lead to activation of the mitochondrial (intrinsic) pathway of apoptosis. In addition, signalling through the death receptor (extrinsic) pathways, contributes to sensitivity of tumor cells towards cytotoxic treatment. Both pathways converge finally at the level of activation of caspases, the effector molecules in most forms of cell death. In addition to classical apoptosis, non-apoptotic modes of cell death have recently been identified. Mechanisms to overcome apoptosis resistance include direct targeting of antiapoptotic molecules expressed in tumors as well as re-sensitization of previously resistant tumor cells by re-expression of caspases and counteracting apoptotis inhibitory molecules such as Bcl-2 and molecules of the IAP family of endogenous caspase inhibitors. Molecular insights into regulation of apoptosis and defects in apoptosis signalling in tumor cells will provide novel approaches to define sensitivity or resistance of tumor cells towards antitumor therapy and provide new targets for rational therapeutic interventions for future therapeutic strategies.This work was presented at the first Cancer Immunology and Immunotherapy Summer School, 8–13 September 2003, Ionian Village, Bartholomeio, Peloponnese, Greece.     

Detection and measurement of alternative splicing using splicing-sensitive microarrays

Splicing and alternative splicing are major processes in the interpretation and expression of genetic information for metazoan organisms. The study of splicing is moving from focused attention on the regulatory mechanisms of a selected set of paradigmatic alternative splicing events to questions of global integration of splicing regulation with genome and cell function. For this reason, parallel methods for detecting and measuring alternative splicing are necessary. We have adapted the splicing-sensitive oligonucleotide microarrays used to estimate splicing efficiency in yeast to the study of alternative splicing in vertebrate cells and tissues. We use gene models incorporating knowledge about splicing to design oligonucleotides specific for discriminating alternatively spliced mRNAs from each other. Here we present the main strategies for design, application, and analysis of spotted oligonucleotide arrays for detection and measurement of alternative splicing. We demonstrate these strategies using a two-intron yeast gene that has been altered to produce different amounts of alternatively spliced RNAs, as well as by profiling alternative splicing in NCI 60 cancer cell lines.     

癌症中lncRNA调控可变剪接的生物信息学研究进展

可变剪接是指基因在不同剪接模式下生成RNA异构体的过程,是基因转录后表达调控的重要机制。可变剪接已被证实在癌症发生发展中扮演着重要角色,而异常剪接被认为是肿瘤发生的重要标志。长链非编码RNA(lncRNA)是基因可变剪接过程中的重要参与者和调节者,并且诸多证据表明lncRNA可通过调控可变剪接进而影响癌症的发生发展。本文对癌症中lncRNA调控的可变剪接相关研究进行了综述,并对相关生物信息学工具及数据库进行了总结。     

Cancer hallmarks and malignancy features: Gateway for improved targeted drug delivery

Cancer chemotherapy is mainly based on the use of cytotoxic compounds that often affect other tissues, generating serious side effects which deteriorate the quality of life of patients. Recent advancements in targeted drug delivery systems offer opportunities to improve the efficiency of chemotherapy, by the use of smaller drug doses with reduced side effects. In the gene therapy approach, this consists in improving the transformation potential of the gene delivery system. Interestingly, these systems further provide good platforms for the delivery of hydrophobic and low-bioavailability compounds, while facilitating the penetration of the blood-brain barrier. The present report provides an overview of biologically relevant cancer hallmarks that can be exploited to design effective delivery vehicles that release cytotoxic compounds specifically in cancer tissues, in a targeted manner. The relevance of each cancer marker is presented, with particular emphasis on the generation of these hallmarks and their importance in cancer cell biology.     

盐霉素抗肿瘤作用研究进展

盐霉素(salinomycin)特异性杀伤肿瘤干细胞(cancer stem cell,CSC)作用的发现,引起了国内外学者的广泛关注.最近的研究表明,盐霉素能高选择性杀死小鼠身上的人乳腺癌CSC并且其效力比紫杉醇高100倍.盐霉素这种靶向作用于CSC的能力及较好的成药性,使其具有研发为一种新型的抗癌药物的潜能.通过手术及术后化疗抗癌的传统方法已经难以对抗肿瘤的复发或转移.然而,利用离子型载体抗生素即盐霉素杀伤肿瘤干细胞这一特性,消除肿瘤复发与转移的”根源”,从而达到治愈”癌症”这一顽疾的目的在理论上是可行的.多项研究已证实盐霉素能对抗多种肿瘤干细胞,因此我们认为盐霉素是一种广谱抗肿瘤药物,这些结论将推动临床抗肿瘤研究进入一个崭新的阶段,为防癌治癌工作提供实验依据和新的思路.本文将系统阐述盐霉素抗肿瘤药效学及其作用机制的研究进展,以期为后续临床研发抗癌新化合物提供参考.     

Role of PRMTs in cancer: Could minor isoforms be leaving a mark?

Protein arginine methyltransferases(PRMTs) catalyze the methylation of a variety of protein substrates, many of which have been linked to the development, progression and aggressiveness of different types of cancer. Moreover, aberrant expression of PRMTs has been observed in several cancer types. While the link between PRMTs and cancer is a relatively new area of interest, the functional implications documented thus far warrant further investigations into its therapeutic potential. However, the expression of these enzymes and the regulation of their activity in cancer are still significantly understudied. Currently there are nine main members of the PRMT family. Further, the existence of alternatively spliced isoforms for several of these family members provides an additional layer of complexity. Specifically, PRMT1, PRMT2, CARM1 and PRMT7 have been shown to have alternative isoforms and others may be currently unrealized. Our knowledge with respect to the relative expression and the specific functions of these isoforms is largely lacking and needs attention. Here we present a review of the current knowledge of theknown alternative PRMT isoforms and provide a rationale for how they may impact on cancer and represent potentially useful targets for the development of novel therapeutic strategies.     

Cancer immunogene therapy: A review

Although immunotherapy has long held out promise as a specific, potent approach to cancer therapy, clinical applications have been unrewarding to date. However, advances in gene transfer technology and basic immunology have opened new avenues to stimulate antitumor immune responses including immunogene therapy. Many different approaches to immunogene therapy have been identified. These include transferring genes encoding proinflammatory proteins to tumor cells, suppressing immunosuppressive gene expression, and transferring proinflammatory genes and/or tumor antigen genes to professional antigen-presenting cells. In some cases, genes are transferred to tumor or antigen-presenting cells in situ. In others, gene transfer is performed ex vivo as part of preparing an anticancer vaccine. We discuss the underlying approach, relative success, and clinical application of various cancer immunogene therapy strategies, paying particular attention to immunogene therapy vaccines. Large numbers of preclinical studies have been reported, but only scattered clinical trial results have appeared in the literature. Although very successful preclinically, the ideal cancer immunogene therapy approach remains to be determined and will likely vary with tumor type. Clinical impact may be improved in the future as treatment protocols are refined.     

三阴型乳腺癌的化学治疗和靶向治疗进展

三阴型乳腺癌(Triple negative Breast cancer,TNBC)占乳腺癌总数的15%,是一种免疫组织化学亚型。通常发生于青年女性,有很高的复发率,内脏和中枢神经系统转移早,病程短、死亡率高。对大多数TNBC患者,常规化疗是主要的治疗方式。20%患者有很好的化疗敏感性,对化疗耐药的TNBC患者靶向治疗为当前研究的热点,寻找乳腺癌新的治疗靶点,提出TNBC新的治疗策略,有望去改善TNBC患者的预后。     

Evolution of resistance to anti-cancer therapy during general dosing schedules

Anti-cancer drugs targeted to specific oncogenic pathways have shown promising therapeutic results in the past few years; however, drug resistance remains an important obstacle for these therapies. Resistance to these drugs can emerge due to a variety of reasons including genetic or epigenetic changes which alter the binding site of the drug target, cellular metabolism or export mechanisms. Obtaining a better understanding of the evolution of resistant populations during therapy may enable the design of more effective therapeutic regimens which prevent or delay progression of disease due to resistance. In this paper, we use stochastic mathematical models to study the evolutionary dynamics of resistance under time-varying dosing schedules and pharmacokinetic effects. The populations of sensitive and resistant cells are modeled as multi-type non-homogeneous birth-death processes in which the drug concentration affects the birth and death rates of both the sensitive and resistant cell populations in continuous time. This flexible model allows us to consider the effects of generalized treatment strategies as well as detailed pharmacokinetic phenomena such as drug elimination and accumulation over multiple doses. We develop estimates for the probability of developing resistance and moments of the size of the resistant cell population. With these estimates, we optimize treatment schedules over a subspace of tolerated schedules to minimize the risk of disease progression due to resistance as well as locate ideal schedules for controlling the population size of resistant clones in situations where resistance is inevitable. Our methodology can be used to describe dynamics of resistance arising due to a single (epi)genetic alteration in any tumor type.     

Accelerated ageing: from mechanism to therapy through animal models

Ageing research benefits from the study of accelerated ageing syndromes such as Hutchinson-Gilford progeria syndrome (HGPS), characterized by the early appearance of symptoms normally associated with advanced age. Most HGPS cases are caused by a mutation in the gene LMNA, which leads to the synthesis of a truncated precursor of lamin A known as progerin that lacks the target sequence for the metallopotease FACE-1/ZMPSTE24 and remains constitutively farnesylated. The use of Face-1/Zmpste24-deficient mice allowed us to demonstrate that accumulation of farnesylated prelamin A causes severe abnormalities of the nuclear envelope, hyper-activation of p53 signalling, cellular senescence, stem cell dysfunction and the development of a progeroid phenotype. The reduction of prenylated prelamin A levels in genetically modified mice leads to a complete reversal of the progeroid phenotype, suggesting that inhibition of protein farnesylation could represent a therapeutic option for the treatment of progeria. However, we found that both prelamin A and its truncated form progerin can undergo either farnesylation or geranylgeranylation, revealing the need of targeting both activities for an efficient treatment of HGPS. Using Face-1/Zmpste24-deficient mice as model, we found that a combination of statins and aminobisphosphonates inhibits both types of modifications of prelamin A and progerin, improves the ageing-like symptoms of these mice and extends substantially their longevity, opening a new therapeutic possibility for human progeroid syndromes associated with nuclear-envelope defects. We discuss here the use of this and other animal models to investigate the molecular mechanisms underlying accelerated ageing and to test strategies for its treatment.     

Pre- and post-translational regulation of osteopontin in cancer

Osteopontin (OPN) is a matricellular protein that binds to a number of cell surface receptors including integrins and CD44. It is expressed in many tissues and secreted into body fluids including blood, milk and urine. OPN plays important physiological roles in bone remodeling, immune response and inflammation. It is also a tumour-associated protein, and elevated OPN levels are associated with tumour formation, progression and metastasis. Research has revealed a promising role for OPN as a cancer biomarker. OPN is subject to alternative splicing, as well as post-translational modifications such as phosphorylation, glycosylation and proteolytic cleavage. Functional differences have been revealed for different isoforms and post-translational modifications. The pattern of isoform expression and post-translational modification is cell-type specific and may influence the potential role of OPN in malignancy and as a cancer biomarker.     

Engineered drug-resistant immunocompetent cells enhance tumor cell killing during a chemotherapy challenge

Establishment of immunocompetent cell mediated anti-tumor immunity is often mitigated by the myelosuppressive effects during administration of chemotherapy. We hypothesized that protecting these immune cells from drug induced toxicities may allow for the combined administration of immunotherapy and chemotherapy. Using a SIV-based lentiviral gene transfer system we delivered the drug-resistant variant P140KMGMT into the immunocompetent cell lines NK-92 and TALL-104, and the myelogenous leukemia cell line, K562, which is a target for both NK-92 and TALL-104 cells. Genetically engineered immunocompetent cells developed significant resistance to temozolomide compared to non-modified cells, and genetic modification of these cells did not affect their ability to kill K562 cells. We then evaluated the effectiveness of drug-resistant immunocompetent cell mediated killing of tumor cells in the presence and absence of chemotherapy. During a chemotherapy challenge the cytotoxic activity of non-modified immunocompetent cells was dramatically impaired. However, when combined with chemotherapy, genetically-modified immune cells retained their cytotoxic activities and efficiently killed non-modified target cells. These results show that engineering immunocompetent cells to withstand chemotherapy challenges can enhance tumor cell killing when chemotherapy is applied in conjunction with cell-based immunotherapy.