The potential of gene therapy in the treatment of pancreatic cancer

Pancreatic cancer is known to be one of the most problematic forms of cancer. Researchers around the world are still trying to find an adequate treatment for this disease. While surgical operation has been the dominant procedure for treating pancreatic cancer, adjuvant therapies such as radiation or chemotherapy (although the survival rate is still poor) also exist. Pancreatic cancer is notoriously difficult to detect at its initial invasion, despite modern radiographic technology. This means that patients discover the cancer when it is already in an advanced stage, making surgical resection difficult. A new strategy for medical practice in pancreatic cancer is much needed. Gene therapy is currently in the spotlight as a promising new method for cancer cure. Many studies have revealed the potential of this therapy for the treatment of pancreatic cancer, and early clinical trials are taking place to evaluate the success of gene therapy regimes in humans. Here we discuss basic scientific principles and clinical experience with respect to these regimes, including antisense strategies, gene- directed prodrug activation therapy, promoter-gene strategies and oncolytic viral therapy.     

SPARC in cancer biology: Its role in cancer progression and potential for therapy

The ability to effectively target a tumor to achieve complete regression and cure is the ultimate goal that drives our need to better understand tumor biology. Recently, SPARC has generated considerable interest as a multi-faceted protein that belongs to a family of matricellular proteins. It functions not only to modulate cell–cell and cell–matrix interactions, but its de-adhesive and growth inhibitory properties in non-transformed cells have led to studies to assess its role in cancer. Its divergent actions reflect the complexity of this protein, because in certain types of cancers, such as melanomas and gliomas, SPARC is associated with a highly aggressive tumor phenotype, while in others, mainly ovarian, neuroblastomas and colorectal cancers, SPARC may function as a tumor suppressor. Recent studies have also demonstrated a role for SPARC in sensitizing therapy-resistant cancers. Here, the role of SPARC in cancer progression and its potential application in cancer therapy is discussed.     

Targeting inhibitor of apoptosis proteins (IAPs) for cancer therapy

Since cell death by apoptosis plays a key role in the regulation of tissue homeostasis, dysregulation of the cell's intrinsic death program may foster tumor formation and progression. "Inhibitor of apoptosis proteins" (IAPs) block apoptosis at the core of the apoptotic machinery by inhibiting effector caspases. Aberrant expression and/or function of IAPs are found in many human cancers and have been implied in resistance to current treatment approaches. Recent insights into the role of IAPs have provided the basis for various exciting discoveries that aim at modulating expression or function of IAPs. Thus, targeting IAPs, e.g. by antisense approaches or small molecule inhibitors, presents a promising novel approach for future drug development and may proof to be a successful strategy to overcome apoptosis resistance of human cancers.     

表皮生长因子受体酪氨酸激酶家族与肿瘤治疗

表皮生长因子受体(EGFR,ErbB)酪氨酸激酶家族在多种肿瘤中有表达或高表达.在特异性配体的诱导下能够发生家族成员的二聚化,从而激活细胞内下游信号转导途径,调控细胞的增殖、分化、迁移等生物效应.异常的ErbB受体信号与肿瘤的发生、发展有着密切的关系.随着EGFR的人源化单抗Erbitux和针对EGFR的小分子抑制剂Tarceva的成功上市,以ErbB受体为靶点的抗肿瘤药物成为了近年来肿瘤治疗研究中的热点领域.     

The potential of proteasome inhibitors in cancer therapy

Background: The ubiquitin-proteasome system has become a promising novel molecular target in cancer due to its critical role in cellular protein degradation, its interaction with cell cycle and apoptosis regulation and its unique mechanism of action. Objective: This review focuses both on preclinical results and on data from clinical trials with proteasome inhibitors in cancer. Methods: Results in hematological malignancies and solid tumors were included, and important data presented in abstract form were considered in this review. Results/conclusion: Bortezomib as first-in-class proteasome inhibitor has proven to be highly effective in some hematological malignancies, overcomes conventional chemoresistance, directly induces cell cycle arrest and apoptosis, and also targets the tumor microenvironment. It has been granted approval by the FDA for relapsed multiple myeloma, and recently for relapsed mantle cell lymphoma. Combination chemotherapy regimens have been developed providing high remission rates and remission quality in frontline treatment or in the relapsed setting in multiple myeloma. The combination of proteasome inhibition with novel targeted therapies is an emerging field in oncology. Moreover, novel proteasome inhibitors, such as NPI-0052 and carfilzomib, have been developed. This review summarizes our knowledge of the ubiquitin-proteasome system and recent data from cancer clinical trials.     

The corticotropin-releasing factor (CRF) family of neuropeptides in inflammation: potential therapeutic applications

Hypothalamic CRF plays a central role in the coordination of endocrine and behavioral responses to stress and it is also involved in the pathophysiology of several neuropsychiatric diseases including depression, anxiety and addiction. In the mammals, the CRF family of peptides includes CRF, urocortin (Ucn), Ucn I, and Ucn II while was enriched with new members, the urocortins. Their biological effects are mediated by the CRF1 and CRF2 receptors, which belong to the G-protein-coupled receptor super family. Multiple research groups have demonstrated during the last decade the expression of the CRF peptides and their receptors in several components of the immune system and their participation in the ad hoc regulation of inflammatory phenomena. Non-peptide CRF1 antagonists have been recently synthesized for the treatment of CNS related diseases, such as anxiety, depression and drug abuse. In the gastrointestinal tract, these compounds open new therapeutic options in the treatment of lower-GI inflammatory diseases associated to CRF, such as the chronic inflammatory bowel syndromes, irritable bowel disease and ulcerative colitis while Ucn, Ucn I, Ucn II or synthetic non-peptide CRF2 agonists may be useful in the treatment of upper-GI inflammatory diseases. In human endometrium, CRF1 antagonists may be used as abortive agents interfering with the inflammatory phenomena taking place during the implantation of the conceptus. They thus may represent a new class of nonsteroidal inhibitors of implantation. These two examples illustrate the potential therapeutic significance of the CRH in regulating inflammatory phenomena in an ad hoc approach without affecting the rest of the immune system.     

Exploiting the role of O6-methylguanine-DNA-methyltransferase (MGMT) in cancer therapy

Improving the efficacy of standard chemotherapy by targeting DNA repair mechanisms remains an important area of research. O6-methylguanine-DNA-methyltransferase (MGMT), which repairs alkylating agent damage, is one such target. Downregulation of the gene through epigenetic silencing has been shown to predict response to alkylating agent therapy in selected malignancies. Platinums have also been found to downregulate MGMT expression and this approach is currently under exploration. Another way to deplete O6-alkylguanine DNA alkyltransferase (AGT) levels is to modify methylating agent scheduling. Extended dosing has met with early favourable results. However, pseudosubstrates used to inhibit AGT activity have had limited success because of dose-limiting myelotoxicity. Topoisomerase I is 'trapped' on DNA by alteration of ligation kinetics following alkylating agent damage, leading to interest in combining AGT inhibitors or O6-alkylating agents with topoisomerase I inhibitors. DNA repair by AGT is an interesting target for cancer therapy that remains to be fully evaluated. The best results are likely to be achieved where its inhibition is part of treatment targeting multiple DNA damage processing pathways.     

The role of iron chelation in cancer therapy

This review focuses on advances and strategies in the use of iron chelators as anti-tumor therapies. Although the development of iron chelators for human disease has focused primarily on their use in the treatment of secondary iron overload, chelators may also be useful anti-tumor agents. They can deplete iron or cause oxidative stress in the tumor due to redox perturbations in its environment. Iron chelators have been tested for their anti-tumor activity in cell culture experiments, animal models and human clinical trials. Largely for pragmatic reasons, clinical studies of the anti-tumor activity of iron chelators have generally focused on desferrioxamine (DFO), a drug approved for the treatment of iron overload. These studies have shown that DFO can retard tumor growth in many different experimental contexts. However, the activity of DFO is modest, and advances in the use of chelators as anti-cancer agents will require the development of new chelators based on new paradigms. Examples of iron chelators that have shown promising anti-tumor activity (in various stages of development) include heterocyclic carboxaldehyde thiosemicarbazones, analogs of pyridoxal isonicotinoyl hydrazone, tachpyridine, O-trensox, desferrithiocin, and other natural and synthetic chelators. Apart from their use as single agents, chelators may also synergize with other anti-cancer therapies. The development of chelators as anticancer agents is largely an unexplored field, but one with extraordinary potential to impact human cancer.     

The potential role of nintedanib in treating colorectal cancer

Introduction: Angiogenesis leads to the growth, progression, and metastases of a variety of solid tumors, including metastatic colorectal cancer (mCRC), involving particularly the family of vascular endothelial growth factors (VEGF) and their receptors (VEGFR). Several anti-angiogenic inhibitors are already registered for mCRC therapy: bevacizumab, aflibercept, ramucirumab, regorafenib. Nintedanib is a new triple angiokinase oral inhibitor that potently blocks the proangiogenic pathways mediated by VEGFR, platelet-derived growth factor receptor (PDGFR), and fibroblast growth factor receptor (FGFR).

Areas covered: The current state-of-the-art of anti-angiogenic inhibitors employed in the treatment mCRC patients, and in particular the role of nintedanib in this setting, is reviewed and discussed here. A structured search of bibliographic databases for peer-reviewed research literature and of main meetings using a focused review question was undertaken.

Expert opinion: In first-line therapy, a phase II randomized trial showed that nintedanib plus chemotherapy was not inferior to the bevacizumab-based regimen. In heavily pretreated mCRC patients nintedanib improved some outcomes. During the natural history of mCRC resistances to anti-angiogenic therapies can set in and in this context, nintedanib, due to its triple inhibition, might play a role in compensatory angiogenesis overcoming the resistance developed due to VEGF directed therapy.     

The role of letrozole (Femara(R)) in breast cancer therapy: A clinical review

Letrozole is a third-generation aromatase inhibitor for use in postmenopausal women with hormonal-sensitive breast cancer. This drug was found to reduce or effectively shrink tumors in a significant number of such patients. It exhibits antitumor activity at a relatively low daily dose, and is highly potent and selective and well tolerated. Results from recent phase III clinical studies have confirmed the efficacy and the key role of this drug in the therapy of advanced breast cancer in postmenopausal women. Moreover, letrozole demonstrated higher activity and lower toxicity compared to tamoxifen in the first-line therapy of postmenopausal women affected with advanced breast cancer. However, it also represents a valid option in second-line therapy after tamoxifen failure. New data on this agent in adjuvant or neoadjuvant treatment also suggest efficacy in the treatment of early breast cancer. This article reviews the clinical data on letrozole in all settings and its future potential in chemoprevention. (c) 2001 Prous Science. All rights reserved.     

Functional role of T-type calcium channels in tumour growth and progression: prospective in cancer therapy

T-type Ca²⁺ channels represent a specific channel family overexpressed in different types of tumours. Their involvement in controlling the proliferation, angiogenesis and invasion of tumour cells, has been partially clarified. The article by Zhang et al. in this issue of BJP provides the first evidence of anti-tumoural effects of endostatin (ES) in U87 glioma cells. He demonstrated that ES or mibefradil (a L/T-type calcium channel blocker), reduces the proliferation and migration of U87 glioma cells in a T-type Ca²⁺ channel-dependent manner. However, the difference in the blocking effect of mibefradil on T-type calcium channel expression as compared with its ability to inhibit proliferation and migration, supports the idea of a broader T/L-type-independent effect of the mibefradil blocker. Overall, these findings provide new insights for the future development of a novel class of anti-T-type calcium channel blockers in the therapy of glioblastoma.

LINKED ARTICLE

This article is a commentary on Zhang et al., pp. 1247–1260 of this issue. To view this paper visit http://dx.doi.org/10.1111/j.1476-5381.2012.01852.x     

The role of protein kinase C-alpha (PKC-alpha) in cancer and its modulation by the novel PKC-alpha-specific inhibitor aprinocarsen

As our understanding of tumorigenesis increases, interference with the various signaling pathways of tumor cells has become an attractive approach to arresting tumor cell growth and overcoming chemoresistance. Among many intracellular signaling proteins, protein kinase C (PKC) isoenzymes have been identified as possible targets to render tumor cells more susceptible to apoptosis and growth arrest. We review the known biology of the alpha-isoenzyme of PKC in different cancers to provide a rational approach for developing targeted therapies using PKC modulators, including aprinocarsen, an antisense oligonucleotide (ASO) against PKC-alpha.     

肿瘤基因治疗的研究进展

癌症是基因治疗的主要对象,本文介绍了肿瘤基因治疗的方法,在基因治疗中存在的关键问题,近十几年来基因治疗的临床试验进展,并对基因治疗的安全性进行了阐述,同时分析了基因治疗的前景及未来的发展趋势。     

Possible role of epidermal growth factor receptors in the therapy of pancreatic cancer

Pancreatic cancer is considered an 'orphan' cancer because of its relative low incidence. Unfortunately, even with early diagnosis, mortality rates are high and it ranks eighth in the worldwide ranking of deaths due to cancer. The administration of chemotherapeutic agents for the treatment of advanced disease has failed, and current research focuses on the understanding of molecular pathways in order to investigate the role of targeted therapy. It has been known that the development and the progression of pancreatic cancer are caused by the activation of oncogenes, the inactivation of tumor suppressor genes, and the deregulation of many signaling pathways of various growth factors, among which the epidermal growth factor receptor (EGFR) plays an important role. Growth factor receptors and their ligands not only regulate normal cell processes, but have also been identified as key regulators of human cancer formation. EGFR has been found to be expressed and altered in pancreatic cancer and clearly plays a significant role in tumor development and progression, including cell proliferation, regulation of apoptotic cell death, angiogenesis, and metastatic spread. The amplitude and kinetics of growth factor signaling are determined mainly by a highly regulated endocytic process that sorts and directs activated receptors to degradation in lysosomes. Therefore, EGFR is a legitimate therapeutic target. The aim of this review is to outline the endocytic escape of EGFRs in cancer with special attention towards recent advances in various approaches adopted for EGFR targeting.     

Androgen receptor-blocking agents: potential role in pancreatic cancer

The growth of pancreatic adenocarcinoma may be under the control of the sex steroid hormone testosterone, besides other unknown stimuli. This premise was based on the discovery of androgen receptors, together with the enzymes aromatase and 5alpha-reductase, which use testosterone as a substrate, in malignant tissue. The additional support of low circulating serum testosterone and its stimulatory role in an animal model using human tumour xenografts further enhance this suggestion. Confirmatory evidence has now come from a double-blind, placebo-controlled trial in patients with pancreatic cancer in which flutamide, the pure androgen receptor blocker, doubled survival duration over control patients. Flutamide was administered in a dosage of 250mg 3 times daily. Support for this finding has recently been presented at a meeting of the Pancreatic Society of Great Britain. It is now important for further confirmatory studies to be carried out and to use flutamide in combination with other current adjuvant therapies in patients with pancreatic cancer.     

人端粒酶逆转录酶(hTERT)启动子在肿瘤基因治疗中的应用

目前肿瘤靶向基因治疗是肿瘤基因治疗领域中非常具有应用前景的疗法之一。大量研究表明肿瘤中端粒酶会异常表达。与常用启动子相比,人端粒酶逆转录酶(hTERT)启动子能够靶向端粒酶阳性细胞如肿瘤细胞等,而成为肿瘤治疗研究的热点。本文就hTERT启动子介导毒性基因、自杀基因、溶瘤病毒等进行肿瘤的基因治疗,以及hTERT启动子优化策略进行阐述。