Vaccines and other immunological approaches for cancer immunoprevention

The immune system effectively prevents cancer, whereas severe immunodepression increases its incidence. Cancer immunoprevention is a strategy based on the concept that enhancement of tumor immunity in healthy individuals reduces cancer risk. It can be viewed as a kind of chemoprevention. For cancer immunoprevention, the cancer universe can be neatly divided between tumors caused - directly or indirectly - by infectious agents and all other tumors. Immunoprevention of tumors caused by infectious agents is already implemented at the population level for hepatitis B virus (HBV)-related hepatocellular carcinoma and for tumors caused by human papillomaviruses (HPV), like cervical carcinoma. Now the challenge is to develop immunological strategies to prevent the bulk ( > 80%) of human tumor burden, unrelated to infections. Both vaccines against tumor antigens and immune modulators can prevent tumor onset in cancerprone mice. These studies outlined the target antigens and the molecular and cellular mechanisms of cancer immunoprevention: a) the best target antigens are surface molecules controlling tumor growth and progression (oncoantigens); b) combinations of potent vaccines and nonspecific stimuli (adjuvants) yield the strongest protection; c) immunoprevention must start early in the natural history of tumors, before key progression events like the onset of carcinoma in situ; d) lifetime protection requires repeated boosts, to maintain a strong and steady immune response; e) antibodies and helper, rather than cytotoxic, T cells mediate long-term protection from tumor onset; f) immunoprevention can be combined with chemoprevention. The development of agents like tamoxifen, which went from cancer therapy to chemoprevention, could be a model for the translation of cancer immunoprevention from mice to humans.     

非小细胞肺癌靶向治疗新药——厄洛替尼

厄洛替尼是一种口服、高选择性、可逆的表皮生长因子受体(EGFR)酪氨酸激酶(TK)抑制剂,它通过抑制EGFR-TK的自磷酸化反应,抑制信号转导,从而达到抑制肿瘤生长作用。一项Ⅲ期安慰剂对照临床研究结果表明,厄洛替尼每日口服150 mg单药治疗,可显著延长晚期复发性非小细胞肺癌(NSCLC)病人的生存期、延缓疾病进展和症状恶化,且耐受性较好,最常见的不良反应为皮疹和腹泻。本文对厄洛替尼的药动学和药效学特性、临床疗效和药物相互作用以及难治性晚期NSCLC病人的耐受性等作一综述。     

New target therapies for brain metastases from breast cancer

Central nervous system (CNS) metastases from breast cancer (BC) represent an important cause of disease-related morbidity and mortality. For BC patients who develop CNS metastases, local control measures (both surgery and radiation) are essentially palliative and usually poorly effective, with systemic therapies often failing to achieve optimal control mainly due to the presence of the blood-brain barrier which hampers adequate penetration of therapeutic agents into the brain. However, recent evidence suggests that the status of the human epidermal growth factor receptor-2 (HER2) strongly influences the incidence of CNS metastases and the survival of BC patients from the time of development of CNS metastases, with HER2-positive (HER2+) patients generally experiencing higher rates of CNS metastases and prolonged overall survival compared to patients with HER2-negative disease. This phenomenon likely reflects the difficult CNS drug-penetration and improved control of extra-CNS disease following the clinical use of the anti-HER2 monoclonal antibody trastuzumab. Importantly, this HER2-based survival difference has important implications when planning the optimal treatment of BC patients with CNS metastases. To date, although no systemic therapy has been specifically approved for the treatment of CNS metastases from BC, several targeted agents are being clinically developed for this purpose. In the present review we will discuss the targeted therapies that are under investigation for the treatment of CNS metastases from BC, highlighting the different implications based on whether a given agent is being developed to target CNS metastases from HER2+ or HER2-negative breast cancer.     

MHC-bound antigens and proteomics for novel target discovery

The MHC molecules present normal as well as disease-related and pathogen-derived peptides to T cells as a way of alerting the immune system of the health status of a cell. Proteomic technologies involving immunoaffinity purification are now extensively used to separate MHC complexes from their peptide cargo, and then the peptides are sequenced by tandem mass spectrometry. The identified peptides are tested as vaccine candidates for viral diseases, immunostimulants for treating cancer, and immune-tolerance-inducing agents for autoimmune disorders. One of the challenges in devising novel HLA-peptide-based immunotherapies is to decipher whether a therapeutic window exists between the induction of tumor immunity and the onset of autoimmunity, which can have dangerous sequelae. This review will cover these topics with an overview of the vast possibilities emerging in the field of proteomic analyses of MHC-bound antigens as novel targets for immunotherapy.     

Tumor-targeted metabolic inhibitor prodrug labelled with cyanine dyes enhances immunoprevention of lung cancer

Recent progress in targeted metabolic therapy of cancer has been limited by the considerable toxicity associated with such drugs. To address this challenge, we developed a smart theranostic prodrug system that combines a fluorophore and an anticancer drug, specifically 6-diazo-5-oxo-L-norleucine(DON), using a thioketal linkage(TK). This system enables imaging, chemotherapy, photodynamic therapy, and on-demand drug release upon radiation exposure. The optimized prodrug, DON-TK-BM3, incorporating ...     

New inhibitors of the mammalian target of rapamycin signaling pathway for cancer

Importance of the field: Contrasting with the broad activation of the PI3K/AKT/mammalian target of rapamycin (mTOR) survival pathway in most cancer, activity of rapalogues appears to be restricted to a few tumor types.

Areas covered in this review: The analysis of molecular activity of the PI3K/AKT/mTOR pathway and resistance mechanisms of rapamycin and rapalogues led to the development of several inhibitory molecules.

What the reader will gain: New anticancer agents including PI3K inhibitors, dual PI3K/mTOR inhibitors, specific mTOR inhibitors, and AKT inhibitors may have direct inhibitory effects on targets by competing with ATP or may be non-ATP-competitive allosteric modulators of protein functions. In addition, another way of blocking the abnormal activation of the PI3K/AKT/mTOR pathway may be achieved by using HSP90 inhibitors. In this paper we review novel drugs inhibiting the mTOR signaling pathway.

Take home message: Several trials are ongoing with novel drugs targeting key kinases involved in the mTOR pathway. Benchmarking those agents with rapalogues in rationally designed preclinical models and conceiving clinical trials in everolimus/temsirolimus-sensitive tumor types may help to identify drugs with a real clinical potential. Understanding mechanisms associated with primary and acquired resistance to rapalogues may help to enlarge indications and provide a rationale for designing combinations that will minimize the risk of developing resistance to rapalogues.     

Livin——癌症治疗的新靶点

Livin是IAPs(inhibitorsofapoptosisproteins,IAPs)蛋白家族的新成员 ,有BIR和RING指结构域 ,能够与Caspas es蛋白结合 ,抑制其介导的细胞凋亡。它在大多数正常成人组织中不表达、在一些肿瘤细胞中的高表达 ,与肿瘤的关系为人们所关注 ,是肿瘤治疗的潜在靶点。     

New target agents in the treatment of colorectal cancer patients

Colorectal cancer (CRC) is the third most common cancer in the Western world. Approximately 60% of patients with CRC require systemic therapy for metastatic disease, either at diagnosis or at disease recurrence. Until recently, classic chemotherapeutic agents have been combined in the treatment of advanced CRC. Novel targeted agents, such as the anti-vascular endothelial growth factor monoclonal antibody bevacizumab or anti-human epidermal growth factor receptor-directed compounds (e.g., cetuximab), have demonstrated substantial efficacy in large clinical trials. Early evidence suggests potential synergism among these classes of compounds or with conventional chemotherapy. The relationships between growth factors, cell surface receptors and their second messengers in the development and progression of human malignancies are not new concepts. The use of therapeutic targeting of these molecular structures in colorectal cancer is enhancing the treatment of colorectal cancer. This review briefly overviews the clinical status of new drugs, after the antibodies cetuximab and bevacizumab, from various mechanistic groups, discussing their advancement in clinical development towards their use in CRC.     

Cripto as a target for cancer immunotherapy

One of the recent, significant advances in cancer immunotherapy is the identification of molecules as targets which regulate cell growth by induction of proliferation and survival signalling pathways. Among them, epidermal growth factor receptor and Her2 have been effectively targeted by monoclonal antibodies. Currently, the treatment of cancer has limitations and most cancer deaths result from the local invasion and distant metastasis of tumour cells. An important insight for the understanding of tumour invasion and metastasis came from the recent discovery that the phenotypic changes of increased motility and invasiveness of cancer cells are reminiscent of the epithelial-mesenchymal transition (EMT) that occurs during embryonic development. The human Cripto, a member of the epidermal growth factor-Cripto, Frl1, and Cryptic (EGF-CFC) protein family and a signalling protein during early embryonic development, plays an important role in cancers. Cripto is attached to the cell membrane through a glycosyl-phosphatidylinositol motif, and is upregulated in a wide range of epithelial cancers. In this paper the authors review the role of Cripto expression in tumourigenesis and in EMT to promote tumour invasion, with emphasis that the unique EGF-like region of Cripto plays a critical role in Cripto signalling-mediated tumour growth and EMT. Therefore, the region should be regarded as a therapeutic point for interruption of the oncogenic and metastatic potential of Cripto for cancer immunotherapy.     

Cripto as a target for cancer immunotherapy

One of the recent, significant advances in cancer immunotherapy is the identification of molecules as targets which regulate cell growth by induction of proliferation and survival signalling pathways. Among them, epidermal growth factor receptor and Her2 have been effectively targeted by monoclonal antibodies. Currently, the treatment of cancer has limitations and most cancer deaths result from the local invasion and distant metastasis of tumour cells. An important insight for the understanding of tumour invasion and metastasis came from the recent discovery that the phenotypic changes of increased motility and invasiveness of cancer cells are reminiscent of the epithelial–mesenchymal transition (EMT) that occurs during embryonic development. The human Cripto, a member of the epidermal growth factor-Cripto, Frl1, and Cryptic (EGF-CFC) protein family and a signalling protein during early embryonic development, plays an important role in cancers. Cripto is attached to the cell membrane through a glycosyl-phosphatidylinositol motif, and is upregulated in a wide range of epithelial cancers. In this paper the authors review the role of Cripto expression in tumourigenesis and in EMT to promote tumour invasion, with emphasis that the unique EGF-like region of Cripto plays a critical role in Cripto signalling-mediated tumour growth and EMT. Therefore, the region should be regarded as a therapeutic point for interruption of the oncogenic and metastatic potential of Cripto for cancer immunotherapy.     

Angiogenesis: a target for cancer therapy

The induction of neoangiogenesis is a critical step already present at the early stages of tumor development and dissemination. The progressive identification of molecules playing a relevant role in neoangiogenesis has fostered the development of a wide variety of new selective agents. Antiangiogenic drugs should be integrated with conventional therapies; however, the design of the best sequence and timing for such combined treatments are still under investigation. In this review will be discussed the signal transduction mechanisms of angiogenic molecules, the development of specific inhibitors and their translation into clinical studies and, finally, the new perspectives in antiangiogenic therapy.     

乙酰肝素酶——癌症转移治疗的靶点

近年来研究表明,乙酰肝素酶与癌症组织的转移有极为密切的相关性,通过抑制乙酰肝素酶可以阻止癌细胞的转移,提示乙酰肝素酶可成为癌症转移治疗的靶点。1乙酰肝素酶及其作用机制侵染性细胞尤其是转移性肿瘤细胞和白细胞可通过调节一系列降解酶从而通过胞外基质和基底膜两层屏障。起初,科学家认为这两层屏障的主要成分———结构蛋白的破坏是肿瘤细胞转移的决定性步骤,因此,过去的研究大多集中在底物为结构蛋白的丝氨酸蛋白酶、半胱氨酸蛋白酶类和基质金属蛋白酶(matrix metalloproteinases,MMPs)类上。事实上,作为胞外基质和基底膜的另一主…     

Mitochondria: a target for cancer therapy

Mitochondria, the cells powerhouses, are essential for maintaining cell life, and they also play a major role in regulating cell death, which occurs upon permeabilization of their membranes. Once mitochondrial membrane permeabilization (MMP) occurs, cells die either by apoptosis or necrosis. Key factors regulating MMP include calcium, the cellular redox status (including levels of reactive oxygen species) and the mobilization and targeting to mitochondria of Bcl-2 family members. Contemporary approaches to targeting mitochondria in cancer therapy use strategies that either modulate the action of Bcl-2 family members at the mitochondrial outer membrane or use specific agents that target the mitochondrial inner membrane and the mitochondrial permeability transition (PT) pore. The aim of this review is to describe the major mechanisms regulating MMP and to discuss, with examples, mitochondrial targeting strategies for potential use in cancer therapy.     

BRAF as a target for cancer therapy

Tumors with mutations in the gene encoding the serine-threonine protein kinase BRAF are dependent on the MAPK signaling pathway for their growth, what offers an opportunity to test oncogene-targeted therapy. Mutations at the position V600 of BRAF were described in approximately 8% of all solid tumors, including 50% of melanomas, 30 to 70% of papillary thyroid carcinomas and 5 to 8% of colorectal adenocarcinomas. Specific BRAF kinase inhibitors are undergoing rapid clinical development and promising data on efficacy have been demonstrated in activated mutant BRAF V600 melanomas. This review article will address: (a) preclinical data on the antitumor activity of BRAF inhibitors in cell lines/ in vivo models and their opposing functions as inhibitors or activators of the MAPK pathway, depending on the cellular context; (b) drug development from non-selective RAF inhibitors to selective BRAF inhibitors, such as PLX4032 and GSK2118436, with emphasis in the clinical efficacy and toxicity of these agents; and (c) possible mechanisms of resistance to BRAF inhibitors and strategies to overcome its development in BRAF mutant tumors.     

Osteopontin as a therapeutic target for cancer

Introduction: Cancer is a complex pathological disorder, established as a result of accumulation of genetic and epigenetic changes, which lead to adverse alterations in the cellular phenotype. Tumor progression involves intricate signaling mediated through crosstalk between various growth factors, cytokines and chemokines. Osteopontin (OPN), a chemokine-like protein, is involved in promotion of neoplastic cancer into higher grade malignancies by regulating various facets of tumor progression such as cell proliferation, angiogenesis and metastasis.

Areas covered: Tumors as well as stroma-derived OPN play key roles in various signaling pathways involved in tumor growth, angiogenesis and metastasis. OPN derived from tumor-activated macrophages modulates the tumor microenvironment and thereby regulate melanoma growth and angiogenesis. OPN also regulates hypoxia-inducible factor-1α-dependent VEGF expression leading to breast tumor growth and angiogenesis in response to hypoxia. Thus, a clear understanding of the molecular mechanism underlying OPN-mediated regulation will shed light on exciting avenues for further investigation of targeted therapies. Silencing of OPN using RNAi technology, blocking OPN activity using specific antibodies and small-molecule inhibitors might provide novel strategies, which would aid in developing effective therapeutics for the treatment of various types of cancer.

Expert opinion: This review focuses on new possibilities to exploit OPN as a tumor and stroma-derived therapeutic target to combat cancer.     

Telomerase as a target for cancer therapy

Normal human somatic cells undergo telomeric attrition and replicative senescence because of inadequate levels of telomerase; however, most immortal cancer cells cope with this by deregulating telomerase. Inhibiting telomerase causes renewed telomeric attrition and eventually highly specific death in cancer cells that express the enzyme. However, most cancer cells undergo many cell divisions before they die, opening the way for acquired drug resistance. Recent attempts to solve this problem include the development of drugs that are more potent catalytic inhibitors, that deny telomerase access to the telomere in situ, or affect telomere structure. Combinations of these approaches may ultimately produce the best clinical results.     

TrkB as a therapeutic target for ovarian cancer

Background: In many countries, ovarian cancer is the most lethal gynecological malignancy. Its poor prognosis is mainly due to the late stage of disease with metastasis at presentation. The significant failure rate of chemotherapy in patients with advanced stage disease is also a main concern. As such, developing novel therapeutic targets is essential to improve long-term survival. Overexpression of Tropomyosin-related kinase B (TrkB), a tyrosine kinase receptor, has been documented in ovarian cancer and is found to be correlated with poor prognosis. Objective/methods: We discuss the functional roles and the related downstream signaling pathways of TrkB and its ligand brain-derived neurotrophic factor (BDNF) in ovarian cancer. The possible crosstalk between TrkB/BDNF and other putative molecular targets in ovarian cancer is also discussed. Results/conclusions: All these latest findings shed light on the application of TrkB as a therapeutic target for ovarian cancer.