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We searched for genes with expressions speci¢c to human monocyte-derived dendritic cells (DCs) using di¡erential display reverse transcription-polymerase chain reaction, and found that N-myc downstream regulated gene 2 (NDRG2), a member of a new family of di¡erentiation-related genes, was expressed in DCs. While DCs derived from CD34 + progenitor cells also showed strong NDRG2 expression, the corresponding mRNA expression was absent in other cell lines including monocytes, B cells, and NK cells. The inhibition of DC di¡erentiation by dexamethasone or vitamin D 3 treatment down-regulated the expression of the NDRG2 gene in DCs. In addition, gene expression was induced in a myelomonocytic leukemia cell line, which is capable of di¡erentiating into DCs in cytokine-conditioned culture. The level of NDRG2 gene expression in DCs was signi¢cantly higher than that of other members of the NDRG gene family. Finally, in contrast to the stable NDRG2 expression in CD40-stimulated DCs, the induction of DC maturation by lipopolysaccharide (LPS) resulted in the down-regulation of NDRG2 gene expression. This down-regulation is likely to be due to a modi¢cation and subsequent destabilization of NDRG2 mRNA, because co-treating with actinomycin D and LPS signi¢cantly blocked this LPS e¡ect. Taken together, our results indicate that NDRG2 is expressed during the di¡erentiation of DCs, and that NDRG2 gene expression is di¡erentially regulated by maturation-inducing stimuli. ß

BACKGROUND: Kallikrein-related peptidase 6 (KLK6) encodes a trypsin-like serine protease that is up-regulated in several cancers, although the putative functions of KLK6 in cancer have not been elucidated. In the current study, overexpression of KLK6 was identified in colon cancer, and the possibility that KLK6 may be a suitable candidate as a tumor marker was examined. METHODS: Messenger RNA (mRNA) transcript levels and protein up-regulation of KLK6 in colon cancer tissues was examined using reverse transcriptase-polymerase chain reaction, immunohistochemistry, and clinicopathologic analyses. Cell proliferation, invasiveness, and antiapoptotic activity were determined in colon cancer cells that were transfected with small-interfering RNA (siRNA) of KLK6. RESULTS: KLK6 mRNA was up-regulated significantly in tumor tissues compared with nontumor regions. KLK6 protein was strongly expressed in adenocarcinomas but was not expressed in normal mucosa or in premalignant dysplastic lesions. Sera from patients with colon cancer revealed an increase in KLK6 secretion (0.25 lg/mL; P ¼ .031) compared with noncancer cells (0.19 lg/mL). Clinicopathologic and immunohistochemical studies of 143 patients with colon cancer revealed a significant correlation between KLK6 expression and Dukes disease stage (P ¼ .005). High KLK6 expression was associated significantly with shorter overall (P ¼ .001) and recurrence-free survival (P ¼ .001). The rates of proliferation and invasiveness were decreased by 50% in cells that were transfected with KLK6 siRNA. The overexpression of KLK6 led to decreased activity of the E-cadherin promoter. CONCLUSIONS: KLK6 was up-regulated significantly in tissues and sera from patients with colon cancer and was associated closely with a poor prognosis, suggesting that KLK6 may be used as a potential biomarker and a therapeutic target for colon cancer.

NDRG (N-Myc downstream-regulated gene)-2 is a member of the NDRG family. Although it has been suggested that NDRG2 is involved in cellular differentiation and tumor suppression, its intracellular signal and regulatory mechanism are not well known. Here, we show the differential expression of NDRG2 in human colon carcinoma cell lines and tissues by reverse transcriptionpolymerase chain reaction and immunohistochemical analyses with monoclonal antibody against NDRG2. NDRG2 was strongly expressed in normal colonic mucosa and colonic adenomatous tissues (25 of 25) but not in all invasive cancer tissues [44 of 99 (44%)]. Most distinctive results indicated that the high expression level of NDRG2 has a positive correlation with tumor differentiation and inverse correlation with tumor invasion depth and Dukes' stage of colon adenocarcinoma. To investigate the roles of NDRG2 in tumorigenesis, we used in vitro cell culture system. SW620 colon cancer cell line with a low level of intrinsic NDRG2 protein was transfected with NDRG2-expressing plasmid. TOPflash luciferase reporter assay showed that the transcriptional activity of T-cell factor (TCF)/lymphoid enhancer factor (LEF) was reduced by NDRG2 introduction, but not by the introduction of mutant NDRG2 generated by deletion or sitedirected mutagenesis. Intracellular b-catenin levels were slightly reduced in the NDRG2-transfected SW620 cells and this regulation of b-catenin stability and TCF/LEF activity were mediated through the modulation of glycogen synthase kinase-3beta activity by NDRG2 function. Our results suggest that NDRG2 might play a pivotal role as a potent tumor suppressor by the attenuation of TCF/b-catenin signaling for the maintenance of healthy colon tissues.