Reduced Expression Of nm23-H1 Research Articles

Spontaneous Cell Detachment and Reattachment in Cancer Cell Lines: An In Vitro Model of Metastasis and Malignancy.

There is an unmet need for simplified in vitro models of malignancy and metastasis that facilitate fast, affordable and scalable gene and compound analysis. “Adherent” cancer cell lines frequently release “free-floating” cells into suspension that are viable and can reattach. This, in a simplistic way, mimics the metastatic process. We compared the gene expression profiles of naturally co-existing populations of floating and adherent cells in SW620 (colon), C33a (cervix) and HeLa (cervix) cancer cells. We found that 1227, 1367 and 1333 genes were at least 2-fold differentially expressed in the respective cell lines, of which 122 were shared among the three cell lines. As proof of principle, we focused on the anti-metastatic gene NM23-H1, which was downregulated both at the RNA and protein level in the floating cell populations of all three cell lines. Knockdown of NM23-H1 significantly increased the number of floating (and viable) cells, whereas overexpression of NM23-H1 significantly reduced the proportion of floating cells. Other potential regulators of these cellular states were identified through pathway analysis, including hypoxia, mTOR (mechanistic target of rapamycin), cell adhesion and cell polarity signal transduction pathways. Hypoxia, a condition linked to malignancy and metastasis, reduced NM23-H1 expression and significantly increased the number of free-floating cells. Inhibition of mTOR or Rho-associated protein kinase (ROCK) significantly increased cell death specifically in the floating and not the adherent cell population. In conclusion, our study suggests that dynamic subpopulations of free-floating and adherent cells is a useful model to screen and identify genes, drugs and pathways that regulate the process of cancer metastasis, such as cell detachment and anoikis.

Nm23H1 mediates tumor invasion in esophageal squamous cell carcinoma by regulation of CLDN1 through the AKT signaling.

Esophageal cancer is a lethal malignancy worldwide. Previously, low expression of metastasis suppressor Nm23H1 and tight junction (TJ) protein claudin-1 (CLDN1) have been known to correlate with poor prognosis in esophageal squamous cell carcinoma (ESCC). However, the molecular interaction between them has not been clarified. In the present study, we first examined the expression of Nm23H1 and CLDN1 in 74 surgical ESCC samples by immunohistochemistry (IHC) to verify their clinicopathologic significance. The biologic effects of Nm23H1 gene silencing or overexpression in ESCC cell lines were then studied by migration and invasion studies, and its regulation on CLDN1 expression was also investigated by western blot analysis. Moreover, the expression of Nm23H1 and CLDN1 at the same invasion front of ESCC tumors was verified by immunofluorescence. The results showed a significantly positive correlation between the expression of Nm23H1 and CLDN1 (γ=0.296, P=0.011) in surgical specimens, especially for the 34 tumors with lymph-node metastasis (γ=0.455, P=0.007). In ESCC cell lines, silencing of Nm23H1 expression markedly enhanced cell invasiveness, accompanied by increased Akt phosphorylation and decreased CLDN1 expression. Conversely, Nm23H1-expressed transfectants exhibited reduced invasiveness, decreased Akt phosphorylation and correspondingly increased CLDN1 expression. Regain of CLDN1 expression in ESCC cells significantly suppressed invasiveness, but did not influence the Akt phosphorylation. Moreover, treating Nm23H1-depleted cells with the AKT inhibitor MK2206 recovered CLDN1 expression, and diminished the invasiveness of ESCC cells. Finally, decreased expressions of both CLDN1 and E-cadherin were observed at the invasive front of the Nm23H1-negative tumors. Overall, our current study documented that reduced Nm23H1 expression activates the AKT signaling pathway, results in diminished CLDN1 expression and potentiates invasiveness of ESCC cells. Enhancement of Nm23H1 expression, inhibition of the AKT signaling pathway, or combined, might be a potential treatment strategy in selective ESCC patients.

Nm23-H1 regulates the proliferation and differentiation of the human chronic myeloid leukemia K562 cell line: A functional proteomics study

Aims Nm23-H1 is a suppressor of metastasis that has been implicated in the regulation of proliferation and differentiation of hematopoietic cells, although specific mechanisms for Nm23-H1 have not been well-characterized. Our study is designed to further elucidate the role of Nm23-H1 in the human chronic myeloid leukemia K562 cell line. Main methods In this study we generated and selected two cell clone pools of human chronic myeloid leukemia K562 cells with up-regulated and down-regulated Nm23-H1 expression. Key findings Our data show that knockdown of Nm23-H1 decreased proliferation and increased the percentage of cells arrested in the G0/G1 phase of the cell cycle. Correspondingly, K562 cells overexpressing Nm23-H1 were more proliferative. After treatment of these two cell types with phorbol 12-myristate 13-acetate (PMA) for 48 h, cells with reduced Nm23-H1 expression had a higher percentage of 8N ploidy and higher expression of CD41 than K562 cells overexpressing Nm23-H1. A functional proteomics analysis identified ten proteins, including ANP32A, Cdc42GAP, and the isoform 2 of SET, whose expression levels were significantly altered by down-regulation of Nm23-H1. In addition, cells with decreased levels of Nm23-H1 had significantly reduced expression of Cdc42 independent of treatment with PMA. The interaction of the endogenous Nm23-H1 and Cdc42 proteins has been further validated by reciprocal immunoprecipitations. Significance We provide data that complement functional studies of Nm23-H1 in regulating hematopoietic cells, and address action mechanisms of Nm23-H1 that have not previously been reported.

Expression of nm23-H1 in uveal melanoma

Uveal melanoma (UM) is the most common malignant intraocular tumor in adults. Despite the high accuracy of clinical diagnosis and advances in local treatment, more than 50% of UM patients develop metastasis within 10 years of initial diagnosis. NM23 is one of the human metastasis suppressor genes. Reduced nm23-H1 expression is correlated with high metastatic potential in many different cancers. The purpose of this study is to investigate the expression of nm23-H1 in UM and its potential value as a prognostic marker. Immunostaining of nm23-H1 was verified in five human UM cell lines with different metastatic potentials. The expression level of nm23-H1 mRNA was evaluated with one-step quantitative real-time PCR. The invasion ability of the cell lines was assessed before and after silencing nm23-H1 with small interference RNA. Thirty-two cases of paraffin-embedded specimens of human UM were immunostained with nm23-H1 monoclonal antibody. The immunostaining was evaluated in a semiquantitative fashion based on extent and intensity. The real-time PCR results of five human UM cell lines showed that expression of nm23-H1 was higher in cell lines with low metastatic potential compared with those with high metastatic potential (P<0.05). The invasive ability of the UM cell lines increased after silencing nm23-H1 expression with small interference RNA (P<0.05). The immunostaining of nm23-H1 was cytoplasmic in all cell lines and UM patients samples. The increased immunostaining intensity of nm23-H1 in patients' samples was associated with better survival rate (Kaplan-Meier test P=0.0097). The expression of nm23-H1 was not correlated with other prognostic factors. It can be concluded that nm23-H1 may be a prognostic marker to predict the survival rate of UM patients and it has the potential to identify high-risk patients.

Prognostic implication of nm23-H1 expression in colorectal carcinomas

Expression of nm23 has been identified as a potential metastatic suppressor. In this study, nm23-H1 expression, clinicopathological parameters and influences on clinical outcomes were investigated in colorectal carcinoma patients. Immunostaining was performed on 185 colorectal carcinomas using a polyclonal anti-nm23-H1 antibody. The nm23-H1 immunoreactivity was weak in 31 (17%), moderate in 48 (26%) and strong in 106 (57%) cases. The well differentiated adenocarcinomas showed significantly strong staining for nm23-H1 compared with the moderately and poorly differentiated adenocarcinomas (chi2 test, P<0.001). Advanced tumour stages were associated with reduced nm23-H1 expression (P<0.001). There was an inverse correlation with angiolymphatic invasion, nodal metastasis and liver metastasis (univariate logistic regression analysis, P<0.001). In univariate analysis, patients with reduced expression of nm23-H1 had significantly shorter overall and disease-free survival than the strong expression group (log-rank test for trend, P=0.002 and P=0.003, respectively). Our results indicated that reduced nm23-H1 expression showed poor prognosis in colorectal carcinomas. As a result, nm23-H1 expression might be a useful marker to predict outcome while planning treatment.

Nm23-H1 immunoreactivity as a prognostic factor in differentiated thyroid carcinoma.

Several prognostic factors have been proposed to identify the patients at risk to develop metastases in differentiated thyroid carcinoma. Reduced nm23-H1 expression (a metastatic suppressor gene) has been correlated with high tumor metastatic potential in various human carcinomas, but the results obtained in differentiated thyroid carcinoma remain controversial. To elucidate the usefulness of nm23-H1 as a differentiated thyroid carcinoma prognosis factor, we evaluate the relationship between nm23-H1 immunoreactivity as well as both clinical status and patient outcome. For this purpose, thyroid resected specimens obtained from 94 differentiated thyroid carcinoma consecutive patients (64 papillary and 30 follicular) with at least 5 yr of follow-up were stained using monoclonal antibody to nm23-H1. We did not observe any relationship between nm23-H1 immunoreactivity and age, gender, initial differentiated thyroid carcinoma stage, local recurrence, or distant metastases in patients with papillary carcinoma. However, in patients with follicular carcinoma, a significant inverse association between metastatic disease and the expression of nm23-H1 product was obtained (P < 0.05). In addition, significant differences were found in the survival curves according to nm23-H1 immunoreactivity (log-rank P < 0.01). Finally, nm-23-H1 immunoreactivity was more specific but less sensitive than AMES score to predict metastases. In conclusion, our results suggest that nm23-H1 immunostaining could be added to the classic prognostic factors currently used to predict the outcome of patients with follicular thyroid carcinoma.

Nm23-H1 Suppresses Invasion of Oral Squamous Cell Carcinoma-Derived Cell Lines without Modifying Matrix Metalloproteinase-2 and Matrix Metalloproteinase-9 Expression

nm23-H1 is a candidate gene for the suppression of cancer metastasis. Several studies on human breast, hepatocellular, gastric, ovarian, and colon carcinomas and melanomas have shown that reduced nm23-H1 expression was closely related to metastatic progression with poor prognosis. However, the biochemical mechanism by which nm23-H1 suppresses the metastasis has yet to be elucidated. In this study, we analyzed the correlation between nm23 expression, cell motility, and the invasive abilities of six different oral squamous cell carcinoma cell lines (HSC2, HSC3, HSC4, KB, OSC19, and OSC20). Reduced mRNA/protein expression of the nm23-H1 was observed in three cell lines (HSC2, HSC3, and HSC4). These cell lines exhibited increased cell motility and an invasive character on organotypic raft culture. On the other hand, the cell lines (KB, OSC19, and OSC20) that showed a higher expression of nm23-H1 exhibited a threefold to fivefold reduced motility and also reflected fewer invasions compared to the former three cell lines. Because the HSC3 cells demonstrated the lowest nm23-H1 expression with the highest cell motility and invasive character, we established nm23-H1-transfected HSC3 cell lines to investigate whether exogenous nm23-H1 protein could inhibit cell migration and invasive activity. These transfectants showed a significant reduction in cell motility with exogenous nm23-H1 in a dose-dependent manner, and exhibited a noninvasive character. An immunofluorescence study demonstrated a distinct stress-fiber distribution at peripheral region of these transfectants. However, no significant difference of matrix metalloproteinase (MMP)-2 and MMP-9 expression was observed between mock transfectant and nm23-H1-transfected cells. These findings suggest that nm23-H1 inhibits the invasive activity of oral squamous cell carcinoma by suppression of cell motility without altering the MMP-2 and MMP-9 status.

Estrogen and progestin regulate metastasis through the PI3K/AKT pathway in human ovarian cancer

Estrogen and progestin are involved in ovarian carcinogenesis. Change in nm23-H1 expression and the PIK3/AKT pathway are involved in carcinogenesis, development, invasion and metastasis of ovarian cancers. Therefore, it is critical to understand the signaling pathways that regulate hormone-induced cell migration and invasion in ovarian cancer. We investigated nm23-H1, AKT and pAKT expression by using immunohistochemical staining in ovarian clear cell adenocarcinoma, ovarian benign, borderline and malignant serous tumors and analyzed their relationship with prognostic factors. Using ES-2 and SKOV-3 ovarian cancer cell lines, we studied the modulation of estrogen and progestin on cell migration and invasion as well as their effect on AKT, pAKT and nm23-H1 expression. Furthermore, the signaling pathways were examined using pharmacological inhibitors (LY294002 and PD98059) or AKT siRNA combined with estrogen or progestin in the two cell lines. Weak nm23-H1 and high AKT and pAKT expression was observed in ovarian serous adeno-carcinoma and ovarian clear cell adenocarcinoma. Our data demonstrated that the expression of nm23-H1 was negatively correlated with tumor stage and grade and lymph node metastasis, whereas the expression of AKT/pAKT was positively correlated with these clinic factors. Estrogen up-regulated pAKT expression and reduced nm23-H1 expression, which ultimately resulted in increased cell migration and invasion. In contrast, progestin reduced pAKT expression and increased nm23-H1 expression, which inhibited cell migration. PIK3 kinase inhibitor LY294002 antagonized the effect of estrogen. On the other hand, it reinforced the effect of progestin. Our data suggest that AKT and pAKT are unfavorable prognostic factors for ovarian serous adenocarcinoma and clear cell carcinomas whereas nm23-H1 expression predicates favorable patient prognosis. Estrogen down-regulates nm23-H1 expression and promotes cell migration and invasion by activating the PIK3/AKT pathway. Progestin has an opposing effect.