Developments with targeted enzymes in cancer therapy.

Cancer therapy based on the delivery of enzymes to tumour sites has advanced in several directions since antibody-directed enzyme/prodrug therapy was first described. It has been shown that methoxypolyethylene glycol (MPEG) can be used to deliver enzyme to a variety of solid tumours. MPEG-enzyme conjugates show reduced immunogenicity and may allow repeated treatment with enzymes of bacterial origin. Enzyme delivery to tumours by polymers can be used to convert a low toxicity prodrug to a potent cytotoxic agent. An example of such a prodrug is CB1954, which can be activated by a human enzyme in the presence of a cosubstrate. Tumour-located enzymes can also be used in conjunction with a combination of antimetabolites and rescue agents. The rescue agent protects normal tissue but is degraded at cancer sites by the enzyme, thus deprotecting the tumour and allowing prolonged antimetabolite action.     

Enzymes to die for: exploiting nucleotide metabolizing enzymes for cancer gene therapy

Suicide gene therapy is an attractive strategy to selectively destroy cancer cells while minimizing unnecessary toxicity to normal cells. Since this idea was first introduced more than two decades ago, numerous studies have been conducted and significant developments have been made to further its application for mainstream cancer therapy. Major limitations of the suicide gene therapy strategy that have hindered its clinical application include inefficient directed delivery to cancer cells and the poor prodrug activation capacity of suicide enzymes. This review is focused on efforts that have been and are currently being pursued to improve the activity of individual suicide enzymes towards their respective prodrugs with particular attention to the application of nucleotide metabolizing enzymes in suicide cancer gene therapy. A number of protein engineering strategies have been employed and our discussion here will center on the use of mutagenesis approaches to create and evaluate nucleotide metabolizing enzymes with enhanced prodrug activation capacity and increased thermostability. Several of these studies have yielded clinically important enzyme variants that are relevant for cancer gene therapy applications because their utilization can serve to maximize cancer cell killing while minimizing the prodrug dose, thereby limiting undesirable side effects.     

Methotrexate reduces antibody responses to recombinant human alpha-galactosidase A therapy in a mouse model of Fabry disease

Therapeutic enzymes are often recognized as foreign by the immune system of patients undergoing enzyme replacement therapy. The antibodies that develop may alter pharmacokinetics and biodistribution of the therapeutic protein, may be able to neutralize the activity of the enzyme, or may cause immune reactions in certain patients. We have explored treatment regimens to reduce the antibody response to human alpha-galactosidase A (r-halphaGAL) in Fabry (alphaGAL knock-out) and normal BALB/c mice. A wide variety of treatment modalities were tested, including high dose tolerance induction, increased frequency of therapeutic doses and immunosuppressive drugs in combination with administration of enzyme. The most substantial effects were observed in mice injected intravenously with r-halphaGAL in combination with methotrexate (MTX), which significantly lowered r-halphaGAL-specific serum antibody levels. A short course of treatment with MTX was able to reduce antibody and spleen cell proliferative responses to long-term r-halphaGAL treatment. MTX was able to suppress the development of r-halphaGAL-specific IgG in antigen-primed mice. However, MTX was not effective in dampening robust ongoing antibody responses. These experiments provide a framework for the design of clinical protocols to prevent the drug-specific antibody responses of patients undergoing enzyme replacement therapy.     

ADAM metallopeptidase domain 17 (ADAM17) is naturally processed through major histocompatibility complex (MHC) class I molecules and is a potential immunotherapeutic target in breast, ovarian and prostate cancers

Selection of suitable antigens is critical for the development of cancer vaccines. Most desirable are over-expressed cell surface proteins that may serve as targets for both antibodies and T cells, thus maximizing a concerted immune response. Towards this goal, we characterized the relevance of tumour necrosis factor-α-converting enzyme (ADAM17) for such targeted therapeutics. ADAM17 is one of the several metalloproteinases that play a key role in epidermal growth factor receptor (EGFR) signalling and has recently emerged as a new therapeutic target in several tumour types. In the present study, we analysed the expression profile of ADAM17 in a variety of normal and cancer cells of human origin and found that this protein is over-expressed on the surface of several types of cancer cells compared to the normal counterparts. Furthermore, we analysed the presentation of a human leucocyte antigen (HLA)-A2-restricted epitope from ADAM17 protein to specific T cells established from normal donors as well as ovarian cancer patients. Our analysis revealed that the HLA-A2-restricted epitope is processed efficiently and presented by various cancer cells and not by normal cells. Tumour-specific T cell activation results in the secretion of both interferon-γ and granzyme B that can be blocked by HLA-A2 specific antibodies. Collectively, our data present evidence that ADAM17 can be a potential target antigen to devise novel immunotherapeutic strategies against ovarian, breast and prostate cancer.     

Cell and gene-based therapies for the lysosomal storage diseases

Lysosomal storage disorders (LSD) are a group of approximately 40 genetic diseases that are caused by the deficiency of one or more lysosomal enzymes. The incidence of LSD is estimated to be approximately 1 in 7500 live births, which makes this one of the more prevalent groups of genetic diseases in humans. The loss in enzymatic activity leads to the accumulation of undegraded substrates within lysosomes, resulting in distension of the organelle and subsequent cellular malfunction. Although palliative treatments such as enzyme replacement therapy (ERT) or substrate reduction therapy (SRT) have been shown to be effective for some of the LSD such as Gaucher, Fabry and MPS I, they are not available as yet, or ineffective, for a large number of other LSD patients. To fulfill this unmet medical need, gene therapy is being considered as an alternate or adjunctive therapy for this group of disorders. A goal of gene therapy for LSD is to introduce a normal copy of the DNA for the lysosomal enzyme into a depot organ such as the liver or muscle with the intent that this will lead to the sustained production and re-constitution of therapeutic levels of the enzyme in the affected tissues. Here, we review the utility of various gene therapy strategies under consideration for the treatment of the LSD, including viral and non-viral gene transfer approaches, as well as stem cell transplantation.     

Helicobacter pylori vs immune system or antibiotics

Helicobacter pylori (H. pylori) infection has often no clinical signs and is one of the most common bacterial infections. All infected subjects have histology of active chronic gastritis. In some cases patients develop peptic ulcer and minority of them develop gastric cancer. Gastric cancer is multifactorial disease, thus various progressions of H. pylori infection and disease are dependent on the host genetic factors, the characteristics of the individual’s immune response, environmental factors, and different bacterial virulence factors of the individual bacterial strains. Eradication of the bacteria plays a crucial role in the treatment of these cases however antibiotic therapy does not always help. Bacteria often develop resistance to antibiotics so we recommend that not only screening for H. pylori also the strain determination should have some diagnostic value, especially in the patients who already developed gastritis. Furthermore, for such patients assessment of disease progression (atrophic or metaplastic gastritis) could be followed by polymorphism determination. Until now we cannot predict the disease based only on single polymorphism. Bacteria successfully neutralize the responses of the immune systems using different enzymes or even components of the host immune response. However, the influence of immune system and its components could represent new ways of treatments and could help to eradicate the infection.     

Twelve immunotherapy drugs that could cure cancers

Summary: Immune T cells can kill cancer cells. Cancer vaccines function by increasing the number of immune T cells. There are exceedingly strict biologic limits imposed on the immune system to prevent excessive T-cell activation and expansion. The same biological restrictions limit cancer vaccines. Immunotherapeutic agents that circumvent the biological restrictions have been invented and formulated, including (i) dendritic cell activators and growth factors, (ii) vaccine adjuvants, (iii) T-cell stimulators and growth factors, (iv) immune checkpoint inhibitors, and (v) agents to neutralize or inhibit suppressive cells, cytokines, and enzymes. Few of these agents are broadly available for the development of effective multiple component regimens. The major problem facing immunotherapy today is a lack of broad availability of agents already in existence. The National Cancer Institute has developed a well-vetted ranked list of agents with high potential to serve as immunotherapeutic drugs. This review focuses on 12 of the agents, all with proven ability to augment T-cell responses. Alone, each has little chance of making substantial inroads into cancer therapy. In combinations dictated by biology, the agents are overwhelmingly likely to have an impact. Future availability of these agents for development of innovative combination cancer therapy regimens will provide a benchmark for the resolve of the national cancer therapy translational research enterprise.     

Treatment of lysosomal storage disorders: focus on the neuronal ceroid-lipofuscinoses

Recent advances in our understanding of lysosomal storage disorders (LSDs) may lead to new therapies to treat the neuronal ceroid-lipofuscinoses (NCLs). In this review, enzyme replacement therapy, gene therapy, cell-mediated therapy and pharmaceutical treatments are considered across the LSDs and extended to therapies for the NCLs. It is likely that a combination of approaches will produce the most beneficial clinical outcome for treatment of pathologies displayed by the NCLs.     

肿瘤化疗协同光动力疗法联合免疫治疗的研究进展

近几十年来,恶性肿瘤的发病率越来越高,其发病年龄逐渐低龄化,严重威胁着人类的生命健康.目前,临床上有多种抗肿瘤治疗方法,但单一治疗方法往往达不到最佳治疗效果,因此常采用联合治疗的方法.联合治疗在增强治疗效果的同时还能减少药物的毒副作用,且可减轻患者痛苦.化学治疗(化疗)是临床上常用的治疗方法,但其副作用较大,对肿瘤细胞造成损伤的同时也会对人体正常细胞造成不可逆损伤.光动力疗法是利用特定波长的光激发富集在肿瘤局部的光敏剂,光敏剂被活化,在组织内氧的存在下可发生光动力反应直接或间接杀伤肿瘤细胞.化疗或光动力治疗肿瘤后会产生肿瘤相关抗原,免疫系统识别肿瘤相关抗原后会刺激机体产生特异性抗肿瘤免疫反应,在化疗协同光动力疗法的同时联合免疫治疗,能够有效地提高化疗药物的治疗效果、减少药物毒副作用,同时能抑制肿瘤转移,并可诱导机体产生长期抗肿瘤免疫反应,实现最大化的治疗效果.对近年来化疗、光动力疗法以及免疫治疗的研究现状作一综述.     

Viral vectors for gene-directed enzyme prodrug therapy

Conventional cancer treatments are often hampered by a lack of tumour selectivity, resulting in toxicity to healthy tissue. Gene-directed enzyme prodrug therapy (GDEPT) is a suicide gene therapy approach that aims to improve the selectivity of chemotherapy by enabling cancer cells to convert non-cytotoxic prodrugs to cytotoxic drugs. Many enzyme/prodrug systems have been described, some of which have already been tested in clinical trials. A key component of GDEPT is a foreign enzyme that is expressed selectively at the tumour site where it converts the prodrug into the cytotoxic agent. The gene encoding the prodrug-activating enzyme needs to be expressed selectively and efficiently in tumour cells in order to spare normal tissue from damage. Substantial efforts have been made to develop gene therapy vectors that are capable of targeting cancer cells. A large number of gene delivery systems have been described for GDEPT: Viral vectors are the most advanced. They include replication-deficient and replication-selective (oncolytic) viruses. Recent advances in engineering viruses for GDEPT are reviewed in this article and data from both preclinical studies and clinical trials are discussed.     

Immunogenicity of protein therapeutics

Protein therapeutics, such as monoclonal antibodies, enzymes and toxins, hold significant promise for improving human health. However, repeated administration of protein therapeutics, whether natural or recombinant, often leads to the induction of undesirable anti-drug antibodies (ADAs), which interfere with or neutralize the effect of the drug. Although an immune response to foreign proteins can be expected and is well understood, the basis for the development of responses to therapeutic autologous proteins is the subject of some debate. Inflammatory components of the drug delivery vehicle, T cell responses, T and B cell epitopes in the protein drug, and the associated B cell response are all targets for interventions aimed at reducing ADA responses. Here, we review some theories put forward to explain the immunogenicity of therapeutic proteins and describe some emerging protein-engineering approaches that might prevent the development of anti-drug antibodies.     

死亡受体介导的凋亡与肿瘤化疗

凋亡是细胞胞内在程序性死亡,是调节组织稳态的中心环节.肿瘤的发生以及其化疗与细胞凋亡密切相关.肿瘤化疗药物的作用机制与死亡受体(DR)介导的凋亡在不同层次存在着多重交叉点,因而探索参与DR凋亡途径的蛋白信号分子与化疗药物作用位点的潜在联系将为人类肿瘤治疗提供新的靶点和思路.     

Can conception of prostate cancer stem cells influence treatment dedicated to patients with disseminated disease?

No survival profit has been achieved for patients with disseminated prostate cancer since hormonal therapy was introduced. It is proposed that dissemination of rare prostatic cancer stem cells may lead to metastatic disease and that resistance of these cells to androgen ablation makes them responsible for failure of current treatments. In this paper, we will discuss the significance of the stem cell model for understanding prostate cancer pathogenesis. The concept of prostate cancer as a stem cell disease has the potential to change our view of its treatment in the particular case of disseminated disease. The major cellular target of prostate cancer therapy has to be directed against neoplastic stem cells. The combination of molecular-targeted therapy with the concept of the cancer stem cells should be introduced for the treatment of disseminated prostate cancer. Disseminated prostate cancer must be treated with agents directed toward stem cells, while hormone-therapy must be only an additional treatment leading to the decrease of tumor burden.     

死亡受体介导的凋亡与肿瘤化疗

凋亡是细胞胞内在程序性死亡,是调节组织稳态的中心环节。肿瘤的发生以及其化疗与细胞凋亡密切相关。肿瘤化疗药物的作用机制与死亡受体（DR）介导的凋亡在不同层次存在着多重交叉点,因而探索参与DR凋亡途径的蛋白信号分子与化疗药物作用位点的潜在联系将为人类肿瘤治疗提供新的靶点和思路。     

死亡受体介导的凋亡与肿瘤化疗

凋亡是细胞胞内在程序性死亡,是调节组织稳态的中心环节.肿瘤的发生以及其化疗与细胞凋亡密切相关.肿瘤化疗药物的作用机制与死亡受体(DR)介导的凋亡在不同层次存在着多重交叉点,因而探索参与DR凋亡途径的蛋白信号分子与化疗药物作用位点的潜在联系将为人类肿瘤治疗提供新的靶点和思路.     

Plasmid-mediated muscle-targeted gene therapy for circulating therapeutic protein replacement: a tale of the tortoise and the hare?

There is now conclusive evidence that gene therapy can lead to real clinical benefit. Initial enthusiasm has been muted by set-backs related to viral vectors including retroviral oncogenesis and adenoviral inflammatory response. Plasmid-mediated muscle-targeted gene transfer offers the potential of a cost-effective pharmaceutical grade therapy delivered by simple intramuscular injection without the need for anaesthetic, cell culture, transplantation or immunosuppression. This approach is particularly appropriate for long-term circulating therapeutic protein replacement currently requiring repeated injection therapy. Wide-ranging clinical applications include haemophilia, chronic anaemia, growth hormone deficiency and diabetes. Inadequate transgene expression, unregulated protein delivery and immune response have been major limiting factors. Recent innovations including in situ electroporation enabling sustained systemic protein delivery within the therapeutic range are reviewed. Pharmacological and physiological approaches to regulation are discussed in addition to the role of innate and humoral immunity. Translation of advances in all of these areas to clinical success will enable muscle-targeted gene therapy to capitalise on its inherent strengths and realise its long-standing promise.     

Injection of plasmin in local area: A new treatment option for nasal polypsis

Nasal polypsis(NP), is one of the most difficult challenges in otorhinolaryngology, as the aetiology and pathophysiology are largely unknown unfortunately, medical treatment is unsatisfactory, and, because of frequent recurrences, repeated surgical interventions are often necessary. Now in clinic, the therapy for NP involves a combination of observation, medical, and surgical treatments. But with both treatments of medical and surgical, recurrences are still common. In nasal polypsis, although fibrotic changes do not dominate, myofibroblasts are significantly more abundant in the pedicle where the polyps can be thought to “grow” than in the central or tip areas. But in the “health” nasal mucosa, myofibroblasts can not been observed. Under normal conditions, when the injury is recovery, myofibroblats subsequent disappear from the injured site due to apoptosis. It is very interesting that myofibroblasts can survival in nasal polyps. We hypothesize here that, in nasal polyps, myofibroblasts adopt strategies to avoid apoptosis and consequent clearance by the immune system. In the “grow” area where the conditions are unchecked, deranged or repeated tissue repair, myofibroblasts, as the key factors, push about the formation or growth of the nasal polyps. So we try injecting plasmin in the pedicle of nasal polypsis to promote myofibroblast apoptosis, which may lead to a new treatment option for this incapacitating disease.     

Treatment effects in the prostate including those associated with traditional and emerging therapies

Classic treatment options for prostate cancer consist of radical prostatectomy, antiandrogen (or hormonal) therapy, and radiation therapy. Hormonal and radiation therapy, in particular, have well known, often profound effects on the histologic appearance of benign prostate tissue and prostatic carcinoma. The tissue changes induced by these treatments have been comprehensively described in several sources. Novel therapies ranging from focal ablative treatments to highly targeted molecular therapies are beginning to emerge and pathologists will play a central role in documenting the effects of these treatments on normal and malignant prostate tissue. It is therefore important that pathologists have access to basic treatment information and a solid working knowledge of the morphologic changes induced by these therapies. This will ensure accurate interpretation and reporting of posttreatment prostate specimens. This review is based on a presentation given by Dr A. Evans at the International Society of Urological Pathology Companion Society Meeting (Hot Topics in Urological Pathology) at The United States Canadian Academy of Pathology Meeting in Washington DC on March 20, 2010. This review will cover the histopathologic features seen in benign prostate tissue and prostatic carcinoma seen following: hormonal therapy, radiation therapy, ablative therapies such as vascular-targeted photodynamic therapy, interstitial laser thermotherapy, and high-intensity focussed ultrasound. An emphasis is placed on these specific modalities as they are currently in use as primary, salvage, or investigational therapy in the treatment of prostate cancer.