• Journal of Life Science
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• v.16 no.6
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• pp.904-910
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• 2006

Dendritic cells (DCs) are the only antigen presenting cells (APCs) capable of initiating immune responses, which is crucial for priming the specific cytotoxic T lymphocyte (CTL) response and tumor immunity. Upon activation by DCs, CD4+ helper T cells can cross-prime CD8+ CTLs via IL-12. However, recently activated DCs were described to prime in vitro strong T helper cell type 1 $(Th_1)$ responses, whereas at later time points, they preferentially prime $Th_2$ cells. Therfore, we examined in this study the optimum kinetic state of DCs activation impacted on in vivo priming of tumor-specific CTLs by using ovalbumin (OVA) tumor antigen model. Bone-marrow-derived DCs showed an appropriate expression of surface MHC and costimulatory molecules after 6 or 7-day differentiation. The 6-day differentiated DCs pulsed with OVA antigen for 8 h (8-h DC) and followed by restimulation with LPS for 24 h maintained high interleukin (IL)-12 production potential, accompanying the decreased level in their secretion by delayed re-exposure time to LPS. Furthermore, immunization with 8-h DC induced higher intracellular $interferon(IFN)-{\gamma}+/CD8+T$ cells and elicited more powerful cytotoxicity of splenocytes to EG7 cells, a clone of EL4 cells transfected with an OVA cDNA, than immunization with 24-h DC. In the animal study for the evaluation of therapeutic or protective antitumor immunity, immunization with 8-h DC induced an effective antitumor immunity against tumor of EG7 cells and completely protected mice from tumor formation and prolonged survival, respectively. The most commonly used and clinically applied DC-based vaccine is based on in vitro antigen loading for 24 h. However, our data indicated that antigen stimulation over 8 h decreased antitumor immunity with functional exhaustion of DCs, and that the 8-h DC would be an optimum activation state impacted on in vivo priming of tumor-specific CTLs and subsequently lead to induction of strong antitumor immunity.

• Journal of Life Science
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• v.29 no.6
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• pp.679-687
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• 2019

Litsea populifolia, a plant species of the Lauraceae family, is widely distributed in the tropical and subtropical areas of Asia. The phylogenetic relationships and botanical characteristics of L. populifolia have been reported; however, its anti-oxidative and anti-cancer activities remain unclear. In this study, we evaluated the anti-oxidative and anti-cancer effects of ethanol extracts of L. populifolia (EELP) together with the molecular mechanism of its anti-cancer activity in human lung adenocarcinoma A549 cells. EELP showed significant anti-oxidative effects with a 50% inhibitory concentration at $11.71{\mu}g/ml$, which was measured by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay. EELP exhibited cytotoxic activity and induced cell cycle arrest at the G1 phase in A549 cells in a dose-dependent manner, whereas EELP did not have the cytotoxic effect on the normal human lung cell line IMR90. Treatment with EELP also resulted in a decreased expression of G1/S transition-related molecules-including cyclin-dependent kinase (CDK) 2, CDK6, cyclin D1, and cyclin E-both for the transcription and translation levels. EELP-induced G1 arrest was associated with the phosphorylation of checkpoint kinase 2 (CHK2), p53, cell division cycle 25 homolog A (CDC25A), and the reduction of CDC25A expression in A549 cells. Collectively, these results suggest that EELP may exert an anti-cancer effect by cell cycle arrest at the G1 phase through both p53-dependent and p53-independent (ATM/CHK2/CDC25A/CDK2) pathways in A549 cells.

• Korean Journal of Clinical Laboratory Science
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• v.51 no.1
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• pp.71-77
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• 2019

Menadione is known as an anti-tumor factor. Many studies have reported the potential anti-cancer role of menadione against a range of cancer cell lines. In this study, the anti-cancer effects of menadione and the underlying molecular signaling involved in apoptosis was investigated in gastric cancer cell lines. The menadione treatment decreased the cell viability of MKN45 gastric cancer cells. The decreased cell viability was attributed to the induction of apoptosis, which was confirmed by the results indicating the activation of caspase-3 and -7 and the cleavage of PARP in Western blotting. The upstream regulatory molecules involved in apoptosis were investigated further and it was discovered that menadione reduced the expression of survivin, an inhibitor of upstream apoptosis proteins. In addition, a transcription factor ${\beta}$-catenin, which is known to regulate survivin expression, was down-regulated by menadione. A previous report showed that menadione inhibited XIAP expression to induce apoptosis and induced G2/M cell cycle arrest in AGS cells. This study elucidated another inhibitory mechanism of menadione against gastric cancer cells in a different cell line. Although further studies will be needed, the inhibitory mechanism demonstrated in this study will help better understand the anti-cancer effects of menadione.