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OPEN ACCESS PLUS
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Contents
13(5): Pp. 681 - 688
Kenji Ina, Takae Kataoka and Takafumi Ando
[Open Access Plus] |
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Natural compounds containing fungal β-glucans have been used to improve general health for thousands of years in China and Japan. Lentinan, the backbone of β-(1, 3)-glucan with β-(1, 6) branches, is one of the active ingredients purified from Shiitake mushrooms and has been approved as a biological response modifier for the treatment of gastric cancer in Japan. Despite recent advances in chemotherapeutic agents, unresectable or recurrent gastric cancer remains an incurable disease, with survival rates being far from satisfactory. Recent clinical studies have shown that chemo-immunotherapy using lentinan prolongs the survival of patients with advanced gastric cancer, as compared to chemotherapy alone. In addition, trastuzumab, an antibody against HER2/neu growth factor receptor, has been used for the treatment of gastric cancer in combination with cytotoxic chemotherapeutic agents. Lentinan may exert a synergistic action with anti-cancer monoclonal antibodies to activate complement systems through the mechanism of antibody-dependent cellular cytotoxicity and complement dependent cytotoxicity. Because a better understanding of its biological activities should enable us to use lentinan more efficiently in the treatment of gastric cancer, immunological effects provided by β-glucans, a possible mode of action of lentinan, and its clinical application including future potential uses are discussed in the present review.
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12(2): Pp. 163 - 171
Tomoya Yokota
[Open Access Plus] |
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KRAS and BRAF mutations lead to the constitutive activation of EGFR signaling through the oncogenic Ras/Raf/Mek/Erk pathway. Currently, KRAS is the only potential biomarker for predicting the efficacy of anti-EGFR monoclonal antibodies (mAb) in colorectal cancer (CRC). However, a recent report suggested that the use of cetuximab was associated with survival benefit among patients with p.G13D-mutated tumors. Furthermore, although the presence of mutated BRAF is one of the most powerful prognostic factors for advanced and recurrent CRC, it remains unknown whether patients with BRAF-mutated tumors experience a survival benefit from treatment with anti-EGFR mAb. Thus, the prognostic or predictive relevance of the KRAS and BRAF genotype in CRC remains controversial despite several investigations. Routine KRAS/BRAF screening of pathological specimens is required to promote the appropriate clinical use of anti-EGFR mAb and to determine malignant phenotypes in CRC. The significance of KRAS/BRAF mutations as predictive or prognostic biomarkers should be taken into consideration when selecting a KRAS/BRAF screening assay. This article will review the spectrum of KRAS/BRAF genotype and the impact of KRAS/BRAF mutations on the clinicopathological features and prognosis of patients with CRC, particularly when differentiating between the mutations at KRAS codons 12 and 13. Furthermore, the predictive role of KRAS/BRAF mutations in treatments with anti-EGFR mAb will be verified, focusing on KRAS p.G13D and BRAF mutations.
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10(8): Pp. 617 - 624
Yu Toyoda and Toshihisa Ishikawa
[Open Access Plus] |
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Some genetic polymorphisms of human ABC transporter genes are reportedly related to the risk of certain diseases and patients responses to medication. Human ABCC11 functions as an ATP-dependent efflux pump for amphipathic anions. One nonsynonymous SNP 538G > A (Gly180Arg) has been found to greatly affect the function and stability of de novo synthesized ABCC11 (Arg180) variant protein. The SNP variant lacking N-linked glycosylation is recognized as a misfolded protein in the endoplasmic reticulum (ER) and readily undergoes proteasomal degradation. This ER-associated degradation of ABCC11 protein underlies the molecular mechanism of affecting the function of apocrine glands. On the other hand, the wild type (Gly180) of ABCC11 is associated with wettype earwax, axillary osmidrosis, colostrum secretion from the mammary gland, and the potential susceptibility of breast cancer. Furthermore, the wild type of ABCC11 reportedly has ability to efflux cyclic nucleotides and nucleoside-based anticancer drugs. The SNP (538G > A) of the ABCC11 gene is suggested to be a clinical biomarker for prediction of chemotherapeutic efficacy. Major obstacle to the successful chemotherapy of human cancer is development of resistance, and nucleoside-based chemotherapy is often characterized by inter- individual variability. This review provides an overview about the discovery and the genetic polymorphisms in human ABCC11. Furthermore, we focus on the impact of ABCC11 538G > A on the apocrine phenotype, patients response to nucleoside-based chemotherapy, and the potential risk of breast cancer.
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10(3): Pp. 250 - 269
Ola Nilsson, Yvonne Arvidsson, Viktor Johanson, Eva Forssell-Aronsson and Hakan Ahlman
[Open Access Plus] |
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Patients with well-differentiated neuroendocrine tumours of the gastrointestinal tract often present with metastases and hormonal symptoms. These patients can be palliated by interventional tumour reduction and medical treatment with somatostatin analogues; no effective chemotherapy is available. Radionuclide therapy via somatostatin receptors is one new therapeutic alternative. The recognition that neuroendocrine tumours express specific receptors for growth factors and chemokines, which are of importance for tumour growth, vascularization, and spread, may open the way for new therapeutic approaches. The signalling pathways in carcinoid tumours are incompletely explored. This review summarizes potential new treatment strategies from clinical and experimental studies, e.g. inhibition of angiogenesis, targeting of growth factors or their receptors by tyrosine kinase inhibitors, interference with specific cellular pathways (mTOR, PI3K, RAS/RAF, Notch), and also inhibition of the proteasome and histone deacetylation. Combining targeted therapy with chemotherapy, or using drugs to sensitize for radionuclide therapy, may enhance the treatment outcome.
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8(7): Pp. 710 - 716
Tam Luong Nguyen
[Open Access Plus] |
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Ribosomal S6 kinase (RSK) is a family of serine/threonine kinases that has been identified as a promising anti-cancer target. While a number of protein kinase inhibitors that have potent activity against other serine/threonine kinases were shown to also inactivate RSK, there is keen interest in the three different inhibitor chemotypes that were shown to be RSK specific, since these compounds have tremendous utility as chemical probes in elucidating the biochemistry of the RSK signaling cascade and unraveling the molecular basis of cancer. Because each compound may have therapeutic potential, the nonspecific kinase inhibitors as well as the RSK specific inhibitors will be discussed.
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8(7): Pp. 705 - 709
A. Bergner and R. M. Huber
[Open Access Plus] |
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Calcium is a ubiquitous second messenger and is involved in virtually all cellular functions. Cellular events being regulated by calcium include gene transcription, metabolism, proliferation and apoptosis. Cancer growth is based on increased proliferation, decreased differentiation and decreased apoptosis. Therefore, the intracellular Ca2+-homeostasis has become one of the focuses in current cancer research. Elevation of the cytoplasmic Ca2+-concentration can result from Ca2+-influx from the extracellular space or from Ca2+-release from intracellular stores. The main intracellular Ca2+-store is the endoplasmic reticulum (ER). The Ca2+-content of the ER is maintained by trans-membrane proteins involving the sarco/endoplasmic reticulum Ca2+-ATPase and the inositol-1,4,5-phosphat receptor. In this review, we summarize the current knowledge of the ER and its trans-membrane proteins as regulating structures of the intracellular Ca2+- homeostasis, what changes occur in malignant cells and how this promotes cancer. We further review possible pharmacological intervention and show future perspectives of the intracellular Ca2+-homeostasis as an anti-cancer target.
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8(6): Pp. 638 - 645
Vineet Pande, Maria J. Ramos and Federico Gago
[Open Access Plus] |
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Balanol, a fungal metabolite, is a potent ATP-competitive inhibitor of Protein Kinase C (PKC) and Protein Kinase A (PKA), important targets in oncology. Since its discovery in 1993, a number of studies have been performed in order to design selective and bioavailable balanol analogs. Several crystal structures of PKA in complex with balanol and a few analogs bound within the catalytic site have also been solved providing insight about the key interactions for binding. The PKA-balanol complex has also served as an interesting model system for structurebased ligand design and validation of a number of computational methodologies aimed at both understanding the physical basis for molecular recognition and addressing the important issue of protein flexibility in ligand binding. We provide an overview of the structure-activity relationships of balanol analogs and summarize the progress made in structural and computational studies involving balanol.
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8(4): Pp. 368 - 380
Ida Casorelli, Maria Teresa Russo and Margherita Bignami
[Open Access Plus] |
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Tumor resistance to cytotoxic chemotherapy drugs and their toxicity to normal cells are major clinical obstacles to anticancer therapy effectiveness. Alterations in various DNA repair pathways play a key role in the development of both mechanisms of drug resistance and toxicity. Since deregulation of the DNA damage response and alterations in DNA repair pathways are relatively common in human cancer, the knowledge of these alterations in cancer cells would be an important predictive factor for the clinical response to chemotherapy and a useful guide in designing an appropriate therapeutic strategy. This review is focused on the mismatch repair (MMR) pathway and the O6-methylguanine-DNA-methyltransferase (MGMT) repair protein. In particular, we examine how inactivation of these DNA repair mechanisms might affect the response of tumor cells to chemotherapy, with a special emphasis on agents inducing methylation and oxidative DNA damage and interstrand DNA cross-links (ICLs). In addition, we provide novel experimental evidence indicating that MMR is required for efficient repair of ICLs via stabilization of RAD51 containing repair intermediates. Finally, we discuss possible emerging therapeutical strategies for treating MMR-defective tumors.
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8(3): Pp. 342 - 349
Nadia Rucci, Maria Susa and Anna Teti
[Open Access Plus] |
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c-Src is a proto-oncogene involved in the genesis of and invasion by many cancers. This non-receptor tyrosine kinase also plays a crucial role in bone homeostasis, since inhibition or deletion of c-Src impairs the function of osteoclasts, the bone resorbing cells. It is thus conceivable that c-Src could be a suitable target for the pharmacological treatment of cancers, skeletal metastases and diseases of bone loss, such as osteoporosis. The pyrrolo-pyrimidines CGP77675 and CGP76030 proved to be effective in preventing bone loss in animal models, while the effect of AZD0530, a dually active inhibitor of c-Src and Bcr-ABL, on bone resorption, has been tested in a Phase I clinical trials with promising results. As far as the metastatic bone disease is concerned, c-Src inhibitors could potentially have inhibitory effects both on osteoclasts and on tumour cells, and could disrupt the vicious circle established between these cell types in the bone microenvironment. In accord with this idea, CGP76030 is able to reduce the incidence of osteolytic lesions and of visceral metastases, and to suppress morbidity and lethality in a bone metastasis mouse model without obvious adverse effects. The purine-based c-Src inhibitor AP23451 and the dual c-Src/Abl inhibitors AP22408 and AP23236 proved efficacious in reducing bone metastases in preclinical studies. These results open a new avenue for the development of innovative therapies for the treatment of bone metastatic disease.
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10(10): Pp. 753 - 768
Carlos Mas-Moruno, Florian Rechenmacher and Horst Kessler
[Open Access Plus] |
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Cilengitide, a cyclic RGD pentapeptide, is currently in clinical phase III for treatment of glioblastomas and in phase II for several other tumors. This drug is the first anti-angiogenic small molecule targeting the integrins αvβ3, αvβ5 and α5β1. It was developed by us in the early 90s by a novel procedure, the spatial screening. This strategy resulted in c(RGDfV), the first superactive αvβ3 inhibitor (100 to 1000 times increased activity over the linear reference peptides), which in addition exhibited high selectivity against the platelet receptor αIIbβ3. This cyclic peptide was later modified by N-methylation of one peptide bond to yield an even greater antagonistic activity in c(RGDf(NMe)V). This peptide was then dubbed Cilengitide and is currently developed as drug by the company Merck-Serono (Germany). This article describes the chemical development of Cilengitide, the biochemical background of its activity and a short review about the present clinical trials. The positive anti-angiogenic effects in cancer treatment can be further increased by combination with “classical” anti-cancer therapies. Several clinical trials in this direction are under investigation.
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