Prostate cancer gene therapy-what have we learned and where are we going?

With recent advances in genetic engineering, tumor biology, and immunology, gene therapy has been recognized as a promising new treatment option for various cancers, including prostate cancer. Several clinical trials of prostate cancer gene therapy, using therapeutic genes which include suicide genes, immunomodulatory genes, tumor suppressor genes, and anti-oncogenes, are under way and preliminary reports have emerged. Although gene therapy for prostate cancer is still at an early stage and requires additional technological breakthroughs, new insights obtained from recent clinical trials indicate a promising potential for prostate cancer gene therapy. In this report, general concepts, current progress, and future prospects in prostate cancer gene therapy are summarized.     

Gene therapy for lung cancer

Lung cancer continues to be the largest killer of Americans due to cancer. Although progress has been made, with advances in chemotherapy, the majority of patients diagnosed with lung cancer ultimately succumb to the disease. A better understanding of the molecular pathogenesis of lung cancer is demonstrating how alterations in oncogenes and tumor suppressor genes control lung cancer initiation, growth, and survival. In this article, attempts to target molecular alterations in lung cancer using gene therapy techniques are reviewed. These include introducing suicide genes into tumor cells, replacement of defective tumor suppressor genes, inactivating oncogenes, and immunotherapy-based approaches using gene therapy technology. The major barrier for these techniques continues to be the inability to specifically target tumor cells while sparing normal cells. Nonetheless, these approaches are likely to yield important biologic and clinical data which will further the progress of lung cancer treatment.     

“Topological Significance” Analysis of Gene Expression and Proteomic Profiles from Prostate Cancer Cells Reveals Key Mechanisms of Androgen Response

Background

The problem of prostate cancer progression to androgen independence has been extensively studied. Several studies systematically analyzed gene expression profiles in the context of biological networks and pathways, uncovering novel aspects of prostate cancer. Despite significant research efforts, the mechanisms underlying tumor progression are poorly understood. We applied a novel approach to reconstruct system-wide molecular events following stimulation of LNCaP prostate cancer cells with synthetic androgen and to identify potential mechanisms of androgen-independent progression of prostate cancer.

Methodology/Principal Findings

We have performed concurrent measurements of gene expression and protein levels following the treatment using microarrays and iTRAQ proteomics. Sets of up-regulated genes and proteins were analyzed using our novel concept of “topological significance”. This method combines high-throughput molecular data with the global network of protein interactions to identify nodes which occupy significant network positions with respect to differentially expressed genes or proteins. Our analysis identified the network of growth factor regulation of cell cycle as the main response module for androgen treatment in LNCap cells. We show that the majority of signaling nodes in this network occupy significant positions with respect to the observed gene expression and proteomic profiles elicited by androgen stimulus. Our results further indicate that growth factor signaling probably represents a “second phase” response, not directly dependent on the initial androgen stimulus.

Conclusions/Significance

We conclude that in prostate cancer cells the proliferative signals are likely to be transmitted from multiple growth factor receptors by a multitude of signaling pathways converging on several key regulators of cell proliferation such as c-Myc, Cyclin D and CREB1. Moreover, these pathways are not isolated but constitute an interconnected network module containing many alternative routes from inputs to outputs. If the whole network is involved, a precisely formulated combination therapy may be required to fight the tumor growth effectively.     

Clinical experience with gene therapy for the treatment of prostate cancer

Localized prostate cancer can be treated effectively with radical prostatectomy or radiation therapy. The treatment options for metastatic prostate cancer are limited to hormonal therapy; hormone-refractory cancer is treated with taxane-based chemotherapy, which provides only a modest survival benefit. New treatments are needed. The gene for the initiation of prostate cancer has not been identified; however, gene therapy can involve tumor injection of a gene to kill cells, systemic gene delivery to target and kill metastases, or local gene expression intended to generate a systemic response. This review will provide an overview of the various strategies of cancer gene therapy, focusing on those that have gone to clinical trial, detailing clinical experience in prostate cancer patients.     

Epigenetic regulation of prostate cancer

Prostate cancer is a commonly diagnosed cancer in men and a leading cause of cancer deaths. Whilst the underlying mechanisms leading to prostate cancer are still to be determined, it is evident that both genetic and epigenetic changes contribute to the development and progression of this disease. Epigenetic changes involving DNA hypo- and hypermethylation, altered histone modifications and more recently changes in microRNA expression have been detected at a range of genes associated with prostate cancer. Furthermore, there is evidence that particular epigenetic changes are associated with different stages of the disease. Whilst early detection can lead to effective treatment, and androgen deprivation therapy has a high response rate, many tumours develop towards hormone-refractory prostate cancer, for which there is no successful treatment. Reliable markers for early detection and more effective treatment strategies are, therefore, needed. Consequently, there is a considerable interest in the potential of epigenetic changes as markers or targets for therapy in prostate cancer. Epigenetic modifiers that demethylate DNA and inhibit histone deacetylases have recently been explored to reactivate silenced gene expression in cancer. However, further understanding of the mechanisms and the effects of chromatin modulation in prostate cancer are required. In this review, we examine the current literature on epigenetic changes associated with prostate cancer and discuss the potential use of epigenetic modifiers for treatment of this disease.     

Housekeeping genes in cancer: normalization of array data

Biological maintenance of cells under variable conditions should affect gene expression of only certain genes while leaving the rest unchanged. The latter, termed "housekeeping genes," by definition must reflect no change in their expression levels during cell development, treatment, or disease state anomalies. However, deviations from this rule have been observed. Using DNA microarray technology, we report here variations in expression levels of certain housekeeping genes in prostate cancer and a colorectal cancer gene therapy model system. To highlight, differential expression was observed for ribosomal protein genes in the prostate cancer cells and beta-actin in treated colorectal cells. High-throughput differential gene expression analysis via microarray technology and quantitative PCR has become a common platform for classifying variations in similar types of cancers, response to chemotherapy, identifying disease markers, etc. Therefore, normalization of the system based on housekeeping genes, such as those reported here in cancer, must be approached with caution.     

磁性纳米技术在癌症基因治疗中的应用

癌症基因组的最新进展使直接针对癌症基因进行治疗具有极大的可能性。然而,需要新的基因传递方法使这种潜力向临床应用转化,为治疗病人服务。磁性纳米技术是通过外部磁场选择性地高效传递治疗基因,还能同时用影像监测体内的传递过程。相比传统的基因传递方法,这种技术能明显提高人类移植肿瘤和不同的内脏器官如肝、肾及中枢神经系统的基因传递效率。因此,磁性纳米技术使活体内癌症的基因治疗进入到新的前沿领域。     

Androgen receptor: a key molecule in the progression of prostate cancer to hormone independence

Despite earlier detection and recent advances in surgery and radiation, prostate cancer is second only to lung cancer in male cancer deaths in the United States. Hormone therapy in the form of medical or surgical castration remains the mainstay of systemic treatment in prostate cancer. Over the last 15 years with the clinical use of prostate specific antigen (PSA), there has been a shift to using hormone therapy earlier in the disease course and for longer duration. Despite initial favorable response to hormone therapy, over a period of time these tumors will develop androgen‐independence that results in death. The androgen receptor (AR) is central to the initiation and growth of prostate cancer and to its response to hormone therapy. Analyses have shown that AR continues to be expressed in androgen‐independent tumors and AR signaling remains intact as demonstrated by the expression of the AR regulated gene, PSA. Androgen‐independent prostate cancers have demonstrated a variety of AR alterations that are either not found in hormone naïve tumors or found at lower frequency. These changes include AR amplification, AR point mutation, and changes in expression of AR co‐regulatory proteins. These AR changes result in a “super AR” that can respond to lower concentrations of androgens or to a wider variety of agonistic ligands. There is also mounting evidence that AR can be activated in a ligand independent fashion by compounds such as growth factors or cytokines working independently or in combination. These growth factors working through receptor tyrosine kinase pathways may promote AR activation and growth in low androgen environments. The clinical significance of these AR alterations in the development and progression of androgen‐independent prostate cancer remains to be determined. Understanding the changes in AR signaling in the evolution of androgen‐independent prostate cancer will be key to the development of more effective hormone therapy. © 2003 Wiley‐Liss, Inc.     

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.     

Multidimensional approaches in dealing with prostate cancer

Prostate cancer is one of the most prevalent malignancies worldwide affecting the human male population. Different case-control, cohort or twin studies and segregation analyses point towards the presence of prostate cancer-susceptibility genes in the population. The studies have shown linkage of prostate susceptibility genes to multiple loci on chromosome 1 and single locus each on chromosomes 4, 8, 16, 17, 19, 20 and X chromosome. However, differences right from the mode of inheritance (autosomal dominant or X-linked recessive) to the target genes exist. There have been reports supporting no or weak linkage to these loci as well. Also, region (environmental factors), age and dietary habits have implications in different aspects of the disease. The important targets for treating prostate cancer are androgens and estrogen (synthesized from androgens by the action of enzyme aromatase) owing to their involvement in development and progression of prostate cancer. Further, prostate gland needs androgens (male hormones) for its normal maintenance and functioning. Besides, radiation therapy and surgical methods have also been used. The emerging areas include identifying and preparing successful vaccines from candidate peptides and gene therapy in several forms. This review deals with the paradox of linkage analyses and the various approaches in practice for treatment and management of prostate cancer.     

Novel system uses probasin-based promoter,transcriptional silencers and amplification loop to induce high-level prostate expression

Background  

Despite several effective treatment options available for prostate cancer, it remains the second leading cause of cancer death in American men. Thus, there is a great need for new treatments to improve outcomes. One such strategy is to eliminate cancer through the expression of cytotoxic genes specifically in prostate cells by gene therapy vectored delivery. To prevent systemic toxicity, tissue- and/or cancer-specific gene expression is required. However, the use of tissue- or cancer-specific promoters to target transgene expression has been hampered by their weak activity.     

基于节点-模块置信度及局部模块度双重约束挖掘前列腺癌候选疾病模块

前列腺癌病因及发病机理研究有助于前列腺癌预防和治疗.目前,前列腺癌生化试验研究方法成本高、耗时,而基于网络计算方法容易受基因表达谱数据不完整、噪声高及实验样本数量少等约束.为此,本文提出一种基于节点-模块置信度及局部模块度的双重约束算法(命名为NMCOM),挖掘前列腺癌候选疾病模块.NMCOM算法不依赖基因表达谱数据,采用候选基因与致病表型之间一致性得分,候选基因与致病基因之间语义相似性得分融合排序策略,选取起始节点,并基于节点-模块置信度及局部模块度双重约束挖掘前列腺癌候选疾病模块.通过对挖掘出的模块进行富集分析,最终得到18个有显著意义的候选疾病基因模块.与单一打分排序方法及随机游走重开始方法相比,NMCOM融合排序策略的平均排名比小、AUC值大,且挖掘出结果明显优于其他模块挖掘算法,模块生物学意义显著.NMCOM算法不仅能准确有效地挖掘前列腺癌候选疾病模块,且可扩展挖掘其他疾病候选模块.     

Adenovirus-mediated delivery of human IFNgamma gene inhibits prostate cancer growth

Interferon gamma (IFNgamma) is regarded as a potent antitumor agent, but therapy with IFNgamma is hampered by its short half-life and significant side effects. We developed a replication defective adenovirus carrying the human IFNgamma gene and evaluated the effects of adenovirus-mediated IFNgamma (Ad-IFNgamma) gene transfer on human prostate cancer cell lines in vitro and on xenografts in vivo. Our results showed infection of prostate cancer cells with Ad-IFNgamma led to production of an active cytokine and resulted in an antiproliferative effect on the prostate cancer cells. Intratumoral injection of Ad-IFNgamma significantly inhibited the growth of DU-145 cell xenografts in vivo, while no significant toxicity effect was observed. RT-PCR analysis indicated transgene expression mainly enriched in tumors in vivo, and slightly distributed in livers. These findings suggest adenovirus-mediated IFNgamma gene transfer is a promising approach in the treatment of advanced prostate cancer.     

Tagging SNPs in the kallikrein genes 3 and 2 on 19q13 and their associations with prostate cancer in men of European origin

Two of the classical kallikrein genes KLK3 and KLK2 on 19q13.4 are plausible candidates in prostate cancer susceptibility. They are expressed almost exclusively in prostate tissue. We have performed a comprehensive analysis of association of variants in these two genes with prostate cancer among men of European descent using a tagging SNP approach. Thirteen SNPs selected from the HapMap database were analyzed in a sample of 596 histologically verified prostate cancer cases and 567 ethnically matched controls. Five SNPs showed significant association at single marker level. Linkage disequilibrium (LD) analysis revealed four LD blocks. We performed a haplotype analysis within each LD block. A major haplotype in block 1 that contains the first two significantly associated SNPs was significantly underrepresented in the prostate cancer cases; a second haplotype in block 3 also showed significant frequency differences between cases and controls. Four of the studied SNPs show positive associations with serum PSA levels. A structure analysis revealed no population stratification in our samples that could have confounded the association results. These findings suggest a plausible role of kallikrein gene variants in the etiology of prostate cancer among men of European ancestry.     

Recent advances in gene therapy and future prospects

Gene therapy, which is treatment of diseases by introducing normal genes into the body, is becoming feasible as the result of advances in genetic engineering. The hematopoietic stem cells have been considered as the appropriate target for gene transfer in many genetic diseases for which allogeneic bone marrow transplantation has been employed successfully. However, there are still many problems to be solved. In particular, expression from retrovirally transduced genes in bone marrow cells has been transient and unstable. On the other hand, an alternative approach to somatic cell gene therapy using nonhematopoietic cells, including skin fibroblasts, endothelial cells, keratinocytes, and lymphocytes, has been shown to possess several advantages. This kind of approach is usually applied to supplementation therapy in not only hereditary disorders but also various acquired diseases, such as cancer or infectious diseases. Recently, clinical application of gene transfer into lymphocytes to treat cancer and immunodeficiency have been approved at NIH (USA). The trial could represent the start of a new era in molecular medicine.