• BMB Reports
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• v.36 no.1
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• pp.43-48
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• 2003

Understanding the process of carcinogenesis will involve both the accumulation of many scientific facts derived from molecular, biochemical, cellular, physiological, whole animal experiments and epidemiological studies, as well as from conceptual understanding as to how to order and integrate those facts. From decades of cancer research, a number of the "hallmarks of cancer" have been identified, as well as their attendant concepts, including oncogenes, tumor suppressor genes, cell cycle biochemistry, hypotheses of metastasis, angiogenesis, etc. While all these "hallmarks" are well known, two important concepts, with their associated scientific observations, have been generally ignored by many in the cancer research field. The objective of the short review is to highlight the concept of the role of human adult pluri-potent stem cells as "target cells" for the carcinogenic process and the concept of the role of gap junctional intercellular communication in the multi-stage, multi-mechanism process of carcinogenesis. With these two concepts, an attempt has been made to integrate the other well-known concepts, such as the multi-stage, multi-mechanisn or the "initiation/promotion/progression" hypothesis; the stem cell theory of carcinogenesis; the oncogene/tumor suppression theory and the mutation/epigenetic theories of carcinogenesis. This new "integrative" theory tries to explain the well-known "hallmarks" of cancers, including the observation that cancer cells lack either heterologous or homologous gap junctional intercellular communication whereas normal human adult stem cells do not have expressed or functional gap junctional intercellular communication. On the other hand, their normal differentiated, non-stem cell derivatives do express connexins and express gap junctional intercellular communication during their differentiation. Examination of the roles of chemical tumor promoters, oncogenes, connexin knock-out mice and roles of genetically-engineered tumor and normal cells with connexin and anti-sense connexin genes, respectively, seems to provide evidence which is consistent with the roles of both stem cells and gap junctional communication playing a major role in carcinogenesis. The integrative hypothesis provides new strategies for chemoprevention and chemotherapy which focuses on modulating connexin gene expression or gap junctional intercellular communication in the premalignant and malignant cells, respectively.

• BMB Reports
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• v.45 no.9
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• pp.526-531
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• 2012

Many malignant tumors become resistant to tumor necrosis factor-alpha (TNF-${\alpha}$)-induced cell death during carcinogenesis. In the present study, we examined whether parkin acts as a tumor suppressor in HeLa cells, a human cervical cancer cell line resistant to TNF-${\alpha}$-induced cell death. TNF-${\alpha}$-treatment alone did not affect HeLa cell viability. However, expression of parkin restored TNF-${\alpha}$-induced apoptosis in HeLa cells. Increased cell death was due to the activation of the apoptotic pathway. Expression of parkin in TNF-${\alpha}$-treated HeLa cells stimulated cleavage of the pro-apoptotic proteins caspase-8, -9, -3, -7 and poly ADP ribose polymerase (PARP). In addition, parkin expression resulted in decreased expression of the caspase inhibitory protein, survivin. These results suggest that parkin acts as a tumor suppressor in human cervical cancer cells by modulating survivin expression and caspase activity. We propose that this pathway is a novel molecular mechanism by which parkin functions as a tumor suppressor.

• Korean Journal of Veterinary Research
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• v.49 no.4
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• pp.361-363
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• 2009

Rhabdoid tumor is an aggressive neoplasm of animals and human. It is similar with rhabdomyosarcoma histopathologically. But cellular origin of this neoplasm showed no striated muscle origin by immunohistological and ultrastructural studies. Castrated male Shit-tzu dog, 6 years old, had a mass in the left gluteal region near to the tail. The mass was examined histopathologically and immunohistologically. Histopathologically, the tumor was consisted of large polygonal cell with abundant eosinophilic cytoplasm. The nuclei in some cells were marked eccentrically located. Immunohistochemically, many neoplastic cells were positive for vimentin. These findings were similar to histopathological and immunohistological features of human rhabdoid tumor and few rhabdoid tumors in animals.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.32 no.3
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• pp.200-208
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• 2006

Amino acids are required for protein synthesis and energy sources in all living cells. The amino acid transport system L is a major nutrient transport system that is responsible for $Na^+$-independent transport of neutral amino acids including several essential amino acids. In malignant tumors, the L-type amino acid transporter 1 (LAT1), the first isoform of system L, is highly expressed to support tumor cell growth. In the present study, the expression and functional characterization of amino acid transport system L were, therefore, investigated in Saos2 human osteogenic sarcoma cells. RT-PCR and western blot analyses have revealed that the Saos2 cells expressed the LAT1 and the L-type amino acid transporter 2 (LAT2), the second isoform of system L, together with their associating protein heavy chain of 4F2 antigen (4F2hc) in the plasma membrane, but the expression of LAT2 was very weak. The uptakes of [${14}^C$]L-leucine by Saos2 cells were $Na^+$-independent and were completely inhibited by the system L selective inhibitor, 2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid (BCH). The affinity of [${14}^C$]L-leucine uptake and the inhibition profiles of [${14}^C$]L-leucine uptake by various amino acids in the Saos2 cells were comparable with those for the LAT1 expressed in Xenopus oocytes. The majority of [${14}^C$]L-leucine uptake is, therefore, mediated by LAT1 in the Saos2 cells. These results suggest that the transports of neutral amino acids including several essential amino acids into Saos2 human osteogenic sarcoma cells are for the most part mediated by LAT1. Therefore, the Saos2 human osteogenic sarcoma cells are excellent tools for examine the properties of LAT1. Moreover, the specific inhibition of LAT1 in tumor cells might be a new rationale for anti-tumor therapy.

• Proceedings of the Korean Society of Toxicology Conference
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• 2003.10b
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• pp.141-141
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• 2003

Ras expression has been suggested as a marker for tumor aggressiveness of breast cancer, including the degrees of invasion and tumor recurrence. We previously showed that p38 MAPK is a key signaling molecule differentially regulated by H-ras and N-ras, leading to H-ras-specific cell invasive and migrative phenotypes in human breast epithelial cells (Cancer Res.: 63, 5454-5461, 2003).(omitted)

• Proceedings of the PSK Conference
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• 2002.10a
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• pp.244.1-244.1
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• 2002

Cyclooxygenase-2 ( COX-2 ) is an inducible enzyme which produces prostanoids by various stimuli. Overexpression of COX-2 in many tumor types indicates its association with tumor progression, which has been a promising target for chemoprevention and chemomodulation. We studied conc- and time-dependency of COX-2 inhibition, growth inhibition, and cell cycle arrest induced by celecoxib, a selective COX-2 inhibitor, in human non-small cell lung cancer (NSCLC) A549 cells. (omitted)

• KSBB Journal
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• v.31 no.1
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• pp.52-57
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• 2016

Mutant p53 (R280K) is highly expressed in MDA-MB-231 triple-negative human breast cancer cells. Currently, we reported the role of mutant p53-R280K in mediating the survival of MDA-MB-231 cells in vitro. The present study was undertaken to determine whether mutant p53-R280K affects breast cancer cell growth in vivo. To this end, we used small interfering RNA to knockdown the level of mutant p53-R280K in MDA-MB-231 cells. Silencing of mutant p53-R280K in MDA-MB-231 cells causes substantial tumor regression of established xenografts in vivo. In xenograft model for breast cancer, silencing of mutant p53-R280K in MDA-MB-231 cells significantly inhibited the tumor growth. Moreover, TUNEL assay showed more occurrence of apoptotic cells in mutant p53-R280K silenced tumors compared to control. Our data indicate that mutant p53-R280K has an important role in mediating tumor growth of MDA-MB-231 cells in vivo. Taken together, this study suggests that endogenous mutant p53-R280K could be used as a therapeutic target for breast cancer cells harboring this TP53 missense mutation.

• Biomolecules & Therapeutics
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• v.20 no.6
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• pp.556-561
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• 2012

Steroid sulfatase (STS) is responsible for the conversion of estrone sulfate to estrone that can stimulate growth in endocrine-dependent tumors such as prostate cancer. Although STS is considered as a therapeutic target for the estrogen-dependent diseases, cellular function of STS are still not clear. Previously, we found that tumor necrosis factor (TNF)-${\alpha}$ significantly enhances steroid sulfatase expression in PC-3 human prostate cancer cells through PI3K/Akt-dependent pathways. Here, we studied whether bacterial lipopolysaccharides (LPS) which are known to induce TNF-${\alpha}$ may increase STS expression. Treatment with LPS in PC-3 cells induced STS mRNA and protein in concentration- and time-dependent manners. Using luciferase reporter assay, we found that LPS enhanced STS promoter activity. Moreover, STS expression induced by LPS increased PC-3 tumor cell migration determined by wound healing assay. We investigated that LPS induced IL-6 expression and IL-6 increased STS expression. Taken together, these data strongly suggest that LPS induces STS expression through IL-6 pathway in human prostate cancer cells.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.27 no.2
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• pp.110-122
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• 2005

Adenoid cystic carcinoma (ACC) of salivary glands has a protracted clinical course with perineural invasion, delayed onset of hematogenous metastasis, and poor responses to classical cytotoxic chemotherapic agents. Most deaths from salivary ACC are caused by lung metastases that are resistant to conventional therapy. Therefore, knowledge of cellular properties and tumor-host interactions that influence the dissemination of metastatic cells is important for the design of more effective therapy of salivary cancer. I determined in vitro expression of epidermal growth factor receptor (EGFR) and its downstream effectors and vascular endothelial growth factor receptor (VEGFR)-2 on a human salivary ACC cell line (ACC2). I also evaluated the expression of EGF and VEGF signaling molecules and metastasis-related proteins on human salivary ACC cells orthotopically growing in nude mice. In Western blot and immunohistochemical analyses, EGFR and VEGFR-2 were presented and phosphorylated in ACC2 cells. In human parotid cancer xenografts in nude mice, EGF and VEGF signaling molecules, IL-8, and MMP-9 were expressed at markedly higher levels than in normal parotid tissues. Moreover, tumor-associated endothelial cells of this orthotopic parotid tumor expressed phosphorylated VEGFR-2 and phosphorylated Akt, which is a cell-survival protein. These data show that those biomarkers can be molecular targets for therapy of salivary ACC, which has a propensity for delayed lung metastasis.

• YAKHAK HOEJI
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• v.55 no.1
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• pp.49-55
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• 2011

Tumor necrosis factor-related apoptosis inducing ligand (TRAIL) is one of the promising anti-cancer agent because of its ability to selectively induce apoptosis in tumor cell lines but not in normal cells. However, TRAIL resistance has been reported in some cancer cells including hepatocarcinoma cells. Therefore, studies of agents that sensitize TRAIL-resistant cancer cells could be a effective therapeutic approach in cancer management. In our study, we examined the effect of combination of TRAIL with apigenin in human hepatocellular carcinoma cells. As a result, the combined use of TRAIL and apigenin significantly enhanced the cytotoxicity in PLC-PRF5 cells. Flow cytometry analysis after annexin V-FITC/PI dual staining showed that this increase of cell cytotoxicity was related to enhanced apoptosis in combined treatment of TRAIL with apigenin. Furthermore, synergistic induction of apoptosis was also confirmed by observation of morphological changes and annexin V-FITC/PI fluorescence. Our findings suggests that apigenin has the potential to improve the efficiency of TRAIL-based therapies in human hepatocellular carcinoma cells. Further study is needed to reveal the molecular mechanisms of this combined therapy.