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DNA damage-inducing agents are among the most effective treatment regimens in clinical chemotherapy. However, drug resistance and severe side effects caused by these agents greatly limit their efficacy. Sensitizing malignant cells to chemotherapeutic agents has long been a goal of chemotherapy. In the present study, suppression of STN1, a gene important for safeguarding genome stability, potentiated the anticancer effect of chemotherapeutic agents in tumor cells. Using multiple cancer cells from a variety of origins, it was observed that downregulation of STN1 resulted in a significant decrease in the half maximal inhibitory concentration values of several conventional anticancer agents. When cells are treated with anticancer agents, STN1 suppression leads to a decline in colony formation and diminished anchorage-independent growth. Furthermore, it was additionally observed that STN1 knockdown augmented the levels of DNA damage caused by damage-inducing agents. The present study concluded that suppression of STN1 enhances the cytotoxicity of damage-inducing chemotherapeutic agents by increasing DNA damage in cancer cells. [ABSTRACT FROM AUTHOR]

Epigallocatechin-3-gallate (EGCG) is an active and major constituent of green tea. As a non-nucleoside inhibitor of DNA methylation, EGCG is able to inhibit the hypermethylation of newly synthesised DNA, resulting in the reversal of hypermethylation and recovery in expression of the silenced genes. Reversion-inducing cysteine-rich protein with Kazal motifs (RECK) is a novel tumour suppressor gene, which negatively regulates matrix metalloproteinases, and inhibits tumour invasion, angiogenesis and metastasis. The present study aimed to examine the effects of EGCG on the methylation status of the RECK gene and tumour invasion in a salivary adenoid cystic carcinoma (SACC) cell line in vitro. Marked levels of methylated and weak levels of unmethylated RECK promoter were detected in the SACC83 cells, which was determined using methylation-specific polymerase chain reaction (PCR). In addition, the treatment of SACC83 cells with EGCG partially reversed the hypermethylation status of the RECK gene. Western blot analysis and reverse transcription-PCR demonstrated that EGCG significantly enhanced the protein and mRNA expression levels of RECK, and significantly reduced the invasive ability of the SACC83 cells, as determined using a Transwell assay. These results suggested that EGCG possesses novel anti-metastatic therapeutic potential for the treatment of SACC. [ABSTRACT FROM AUTHOR]

Melatonin is predominately produced and secreted by the pineal gland, and inhibits cell growth in various cancer cell lines such as colorectal cancer. However, the precise mechanisms involved have not been fully elucidated. In the present study, the potential molecular mechanism underlying the efficacy of melatonin on migration in RKO colon cancer cells was investigated. The effects of melatonin and H-1152, a selective inhibitor of Rho-associated protein kinase (ROCK), on the migration of RKO cells were analyzed by an in vitro wound healing assay. The localization of zonula occludens-1 (ZO-1) and occludin were observed by immunofluorescence. Reverse transcription-quantitative polymerase chain reaction (qPCR) was performed to analyze the relative mRNA levels of ROCK, ZO-1 and occludin. In addition, western blot analysis was implemented to examine the expression of ROCK, phospho (p)-myosin phosphatase targeting subunit 1 (MYPT1), p-myosin light chains (MLC) and p-p38. The results revealed that the expression levels of ROCK2, p-MYPT1 and p-MLC in RKO cells were decreased, and the membrane protein expression of ZO-1 and occludin increased when the cells were treated with melatonin. qPCR demonstrated that melatonin downregulated ROCK2 gene expression, and upregulated the expression of the ZO-1 and occludin genes. The levels of ZO-1 and occludin localized in the tight junctions were markedly increased in the immunofluorescence assay. In addition, the phosphorylation levels of p38 were reduced when the cells were treated with melatonin, and treatment with H-1152 downregulated p38 phosphorylation. The results indicated that melatonin may inhibit the migration of RKO colon cancer cells by downregulating ROCK expression via the p38/mitogen-activated protein kinase signaling pathway. [ABSTRACT FROM AUTHOR]