nm23-H1 mRNA Expression Research Articles

Expression change of nm23-H1 in differentiation process of leukemia cells and its molecular mechanisms

Objective To detect the mechanisms of nm23-H1, c-Myc, granulocyte colony-stimulating factor (G-CSF) in differentiation of leukemia cells HL-60 and their correlation, and provide theory basis and treatment targets for clinical treatment. Methods We chose CCK-8 assay to detect the proliferation change of the HL-60 cells induced by optimal concentration of all-trans-retinoic acid (ATRA). Wright Giemsa staining was used to observe cell morphological changes. The gene or protein expressions of nm23-H1, c-Myc and G-CSF were detected by reverse transcription-polymerase chain reaction (RT-PCR) or Western blotting assay, and the G-CSF secretion level in supernatants of ATRA-inducing HL-60 cells was measured by enzyme linked immunosorbent assay (ELISA). Results The cell proliferation inhibition rates were respectively (43.00±0.08)%, (49.55±2.30)%, (58.90±6.70)%, (64.60±4.70)%, (72.70±3.20)%, after HL-60 cells were induced by ATRA with drug concentrations of 0.25, 0.50, 1.00, 2.00 and 4.00 μmol/L for 72 hours, with a significant difference (F=69.887, P=0.000). After induced by ATRA, cell morphology confirmed that HL-60 cells were differentiated into mature granulocytes. The mRNA expression of nm23-H1 decreased gradually from 0.79±0.03 to 0.52±0.09. The difference was statistically significant (F=9.679, P=0.002). The relative expression of protein decreased from 1.54±0.12 to 0.40±0.04. The difference was statistically significant (F=90.140, P=0.000). The relative expression of c-Myc mRNA decreased from 0.95±0.05 to 0.46±0.05. The difference was statistically significant (F=27.900, P=0.000). The relative expression of protein decreased from 1.12±0.11 to 0.14±0.03. The difference was statistically significant (F=115.500, P=0.000). Moreover, the mRNA expression of G-CSF increased gradually from 0.26±0.07 to 0.55±0.09. The difference was statistically significant (F=7.817, P=0.004). The level of cell secretion increased from (13.67±7.51)pg/ml to (128.30±25.77)pg/ml. The difference was statistically significant (F=28.020, P=0.000). Conclusion nm23-H1 probably plays an important role in inducing differentiation of HL-60 cells by interacting with the expressions of c-Myc and G-CSF. Key words: Leukemia; Cell differentiation; Granulocyte colony-stimulating factor

Effect of CO2 pneumoperitoneum on the proliferation of human ovarian cancer cell line SKOV-3 and the expression of NM23-H1 and MMP-2.

This study aims to investigate the impacts of CO2 pneumoperitoneum on the growth of ovarian cancer in nude mice and the expression of tumor metastasis suppressor gene (NM23-H1) and matrix metalloproteinase -2 (MMP-2) in SKOV-3 ovarian cancer cell line cancer tissue. Forty five nude mice were used to establish ovarian cancer xenograft models by intraperitoneal injection of human ovarian cancer cell line SKOV-3. Murine xenograft models were divided into four groups: control group (only anesthetized for 0.5 h), laparotomy group (laparotomy for 0.5 h), CO2 pneumoperitoneum of 0.5 h, and CO2 pneumoperitoneum of 1 h group. Mice were killed after 12 weeks to observe intraperitoneal tumor growth and detected mRNA expression of NM23-H1 and MMP-2 in tumor tissues by RT-PCR. Our data show that xenograft tumors grew faster in the CO2 pneumoperitoneum groups than that in control and laparotomy groups and even faster in the CO2 pneumoperitoneum of 1 h group. The mRNA expression of NM23-H1 in CO2 pneumoperitoneum groups was significantly lower than that in control group and laparotomy group (P < 0.01). Moreover, the longer duration of CO2 pneumoperitoneum negatively correlated with lower expression of NM23-H1 (P < 0.01). In contrast to NM23-H1, MMP-2 expression was significantly higher in CO2 pneumoperitoneum groups than that in the control group and laparotomy group (P < 0.01) and positively correlated with the duration of CO2 pneumoperitoneum (P < 0.01). In addition, there was a negative correlation between the expression of NM23-H1 and MMP-2 (r = -0.984, P < 0.05). The CO2 pneumoperitoneum could promote the proliferation and metastasis of human ovarian cancer in nude mice. This effect was positively correlated with the duration of CO2 pneumoperitoneum.

Pro-oncogenic potential ofNM23-H2in hepatocellular carcinoma

NM23 is a family of structurally and functionally conserved proteins known as nucleoside diphosphate kinases (NDPK). There is abundant mRNA expression of NM23-H1, NM23-H2, or a read through transcript (NM23-LV) in the primary sites of hepatocellular carcinoma (HCC). Although the NM23-H1 protein is implicated as a metastasis suppressor, the role of NM23-H2 appears to be less understood. Thus, the aim of this study was to examine whether NM23-H2 is associated with hepatocarcinogenesis. The level of NM23-H2 expression in tumor tissues and the surrounding matrix appeared to be independent of etiology and tumor differentiation. Its subcellular localization was confined to mainly the cytoplasm and to a lesser extent in the nucleus. Ectopic expression of NM23-H2 in NIH3T3 fibroblasts and HLK3 hepatocytes showed a transformed morphology, enhanced focus formation, and allowed anchorage-independent growth. Finally, NIH3T3 fibroblasts and HLK3 hepatocytes stably expressing NM23-H2 produced tumors in athymic mice and showed c-Myc over-expression. In addition, NF-κB and cyclin D1 expression were also increased by NM23-H2. Lentiviral delivery of NM23-H2 shRNA inhibited tumor growth of xenotransplanted tumors produced from HLK3 cells stably expressing NM23-H2. Collectively, these results indicate that NM23-H2 may be pro-oncogenic in hepatocarcinogenesis.

Inhibitory effects of γ-tocotrienol on invasion and metastasis of human gastric adenocarcinoma SGC-7901 cells

Natural vitamin E is a mixture of two classes of compounds, tocopherols and tocotrienols. Recent research has revealed that tocotrienols, especially γ-tocotrienol, exhibit not only the same antioxidant ability as tocopherols, but also remarkable anticancer capacity in cancer cell lines. In this study, the invasion and metastatic capacities of gastric adenocarcinoma SGC-7901 cells and the correlation with antimetastasis mechanisms induced by γ-tocotrienol were explored. The results showed the inhibitory effects of γ-tocotrienol at doses of 15, 30, 45 and 60 μmol/L for 48 h on cell migration and cell matrigel invasion; activities of matrix metalloproteinase (MMPs) increased in SGC-7901 cells when compared to the control group ( P<.05 or P<.01). An increasing trend in the chemotactic responses to fibronectin (FN) in SGC-7901 cells was found in the γ-tocotrienol treatments. SGC-7901 cell attachment decreased in the γ-tocotrienol-treated groups in comparison with the control group ( P<.01). The mRNA expressions of MMP-2 and MMP-9 showed that γ-tocotrienol significantly reduced the matrigel invasion capability through down-regulation of the mRNA expressions of MMP-2 and MMP-9 ( P<.01), and up-regulation of tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 in SGC-7901 cells by treatment with γ-tocotrienol for 48 h ( P<.05). γ-Tocotrienol also significantly increased the mRNA expression of nm23-H1 in SGC-7901 cells ( P<.01). These findings suggest a potential mechanism of γ-tocotrienol-mediated antitumor metastasis activity and indicate the role of vitamin E as potential chemopreventative agents against gastric cancer.

High expression of human nonmetastatic clone 23 type 1 in cancer of uterine cervix and its association with poor cell differentiation and worse overall survival

The role of human nonmetastatic clone 23 type 1 (nm23-H1), a metastasis-associated gene, is less clear-cut in cancer of uterine cervix; therefore, we investigate its expression in cancer tissues and its correlation with clinicopathologic variables and survival of patients. Thirty cervical cancer tissues and their normal counterparts were collected to evaluate quantitative nm23-H1 mRNA expression. From them, 16 cancer and 16 normal tissues were collected and added with another 64 cancer tissues to construct a 96-tissue core microarray for immunohistochemical study. We evaluated the relationships among nm23-H1 immunostaining using semi-quantitative H scores, clinicopathologic parameters, recurrence and survival in cervical cancer patients. Nm23-H1 mRNA expression and H score (median H scores: 2.0 vs. 0.3, P = 0.001) were higher in cervical cancer tissues than normal counterparts, respectively. Nm23-H1 expression was significantly associated with depth of stromal invasion (P = 0.003), tumor diameter (P = 0.044) and cell differentiation (P = 0.025). Other than stage II, poor cell differentiation as well as positive parametrium invasion and lymph node metastasis, positive nm23-H1 expression was significantly correlated with poor overall survival. High nm23-H1 expression is predictive of worse overall survival for cervical cancer patients.

Anti-tumor mechanism of norcantharidin for the implanted tumors of human gallbladder carcinoma in nude mice in vivo

To explore the anti-tumor mechanism of norcantharidin (NCTD) for the implanted tumors of human gallbladder carcinoma in nude mice in vivo. Animal model of implanted tumors of human gallbladder carcinoma in nude mice was established. Mice were randomly divided into control, 5-FU, NCTD and NCTD + 5-FU groups and were taken different treatment. The expressions of PCNA, Ki-67, cyclin D1, p27, Bcl-2, Bax, Survivin, nm23/nm23-H1, MMP2 and TIMP2 proteins or genes in each tissue section of every group were determined by immunohistochemistry and RT-PCR. (1) On proliferation-related gene proteins, the expression of PCNA, Ki-67, cyclin D1 was significantly decreased, with significantly increased expression of p27 protein, in paraffin sections of NCTD group when compared with control group (P < 0.05); The expression of PCNA mRNA, cyclin D1 mRNA was decreased, with significantly increased expression of p27 mRNA in NCTD group. (2) On apoptosis-related gene proteins, the expression of Bcl-2 was significantly decreased in paraffin sections of NCTD group when compared with control group (P < 0.05); The expression of Bcl-2 mRNA, Survivin mRNA was significantly decreased, with significantly increased expression of Bax mRNA in NCTD group. (3) There was significant difference on invasion around tumor and lung metastasis in NCTD group when compared with control group (P < 0.01). On metastasis-related gene proteins, the expression of nm23 and TIMP2 was significantly increased, with significantly decreased expression of MMP2 in paraffin sections of NCTD group when compared with control group (P < 0.05); The expression of nm23-H1 mRNA, TIMP2 mRNA was significantly increased, with significantly decreased expression of MMP2 mRNA in NCTD group. The anti-tumor mechanism of NCTD for human gallbladder carcinoma in nude mice might correlated with inhibition of cell proliferation, blockage of cell cycle, induction of cell apoptosis, reducing of cell motility and invasive capability, alteration of the expression of proliferation-, apoptosis- and metastasis-related gene proteins such as PCNA, Ki-67, cyclin D1, p27, Bcl-2, Bax, Survivin, nm23, MMP2 and TIMP2.

Nm23-H1 expression and loss of heterozygosity in colon adenocarcinoma

Background: The discovery that genetic alterations in oncogenes and tumour suppressor genes accompany tumour formation in many human tumours has encouraged the search for genes that promote or suppress tumour...

High frequency of concomitant nm23-H1 and E-cadherin transcriptional inactivation in primary non-inheriting colorectal carcinomas.

This study evaluated the added significance of nm23-H1 to that of E-cadherin in determining metastatic proclivity in primary sporadic colorectal carcinomas (SCRCs). A clinical cohort of 52 SCRCs was examined for the significance of nm23-H1 and E-cadherin mRNA levels and E-cadherin protein expression levels into the progression of colorectal tumor invasion, determined by their relevance compared with conventional biological markers. A more than twofold decreased expression of nm23-H1 mRNA was reported in 28/52 (54%) of the carcinomas and was positively associated with the presence of nodal metastases and Astler-Coller stages B1 and B2 in 29% and 35% of the SCRCs, respectively. Reduced expression of E-cadherin mRNA was reported in 38.5% of the carcinomas and was similarly associated with stages Astler-Coller B1 and B2 in 27% of the SCRCs. Decreased E-cadherin immunohistochemical expression (grades II and III) was observed in 67% of the samples. E-cadherin mRNA and protein expression were significantly related to each other. The nm23-H1 (+)/E-cadherin (+) coexpression profile was observed in 31% and was significantly related to the absence of lymph node metastases in 31% and stages Astler-Coller B1 and B2 in 29% of the carcinomas examined. Furthermore, the nm23-H1 (-)/E-cadherin (+) coexpression profile was coupled to decreased E-cadherin immunohistochemical protein detection (grade II) in 21% of the cases examined. These findings suggest that impairment of nm23-H1 expression is an early event into the progression of colorectal metastasis that precedes E-cadherin transcriptional silencing in the majority of SCRCs examined. Nm23-H1 may therefore play an important role in suppressing the early steps of metastasis in sporadic cases of colorectal carcinomas.

Schedule dependent toxicity and efficacy of combined gemcitabine/paclitaxel treatment in mouse adenocarcinoma

The effects of all-trans retinoic acid (ATRA) and epidermal growth factor (EGF) on the expression of nm23-H1, a metastasis suppressor gene, were studied in a human 7721 hepatocarcinoma cell line. It was discovered that the expression of nm23-H1 mRNA was up-regulated by ATRA. This was compatible with the observation that the metastasis-associated phenotypes, such as chemotaxic cell migration and invasion, were both reduced in the ATRA-treated and nm23-H1-cDNA-transferred 7721 cells. However, ability of cells to adhere to fibronectin and laminin was not altered identically in the ATRA-treated and nm23-H1-cDNA-transfected 7721 cells. In contrast, the expression of nm23-H1 mRNA in 7721 cells was down-regulated both by the treatment with EGF and by the transfection of c-erbB-2/neu cDNA, which codes a protein homologous to the EGF receptor. EGF is a compound with biological effects opposite to those of ATRA, and c-erbB-2/neu is known to be a metastasis-promoting gene. These results reveal that the metastasis-preventing effect of ATRA may partly result from the up-regulation of nm23-H1, and the metastasis-promoting effects of EGF and c-erbB-2/neu were probably mediated in part by the down-regulation of nm23-H1.

Increased activity of nm23-H1 gene in squamous cell carcinoma of the head and neck is associated with advanced disease and poor prognosis.

The present study was undertaken to determine whether the nm23-H1 gene is expressed in squamous cell carcinoma of the head and neck (SCCHN) and whether the level of nm23-H1 protein or mRNA in cells vary as they progress to a more malignant phenotype. Of the 120 SCCHN studied 54 (45%) stained positively for nm23-H1 protein. Protein expression was significantly higher in more advanced stages of disease. Expression of nm23-H1 was significantly higher in cancer tissues than in normal, adjacent tissue, dysplasia, or carcinoma in situ. The nm23-H1 rate increased with progression of synchronous lesions from dysplasia to carcinoma in situ and finally to carcinoma (P<0.05). Northern blot analyses of tissues with various clinicopathological characteristics also revealed differences in nm23-H1 mRNA expression. When levels of nm23-H1 mRNA were compared to tumor stage, intensity of expression was found to be higher in stages 3 and 4 than stages 1 and 2 (P<0.01). Malignant tumors had a higher level of mRNA nm23-H1 expression than normal or premalignant tissues. The nm23-H1 negative patients survived significantly longer than nm23-H1 positive ones (P<0.05). To study the possible relationship between nm23-H1 gene expression and cell growth rate in tumor cells, the mRNA level in each tumor was compared to proliferative activity. The nm23-H1 gene expression levels were directly related to the [3H]thymidine labeling index in tumor cells (R=0.6681). Our results strongly indicate that the nm23-H1 gene is involved in progression of SCCHN. Together with results obtained on lung cancer, our observations suggest that increased expression of nm23-H1 in cancers of the upper aerodigestive tract may have different implications than elsewhere in the body.

Northern blot analysis of nm23 gene expression in human lung cancer

To investigate the role of nm23 gene expression in lung cancer. Forty human lung cancer tissues and 19 non-cancerous pulmonary tissues were studied for their nm23-H1 and nm23-H2 mRNA expression with nonradioactive Northern blot hybridization. Correlation of nm23 mRNA expression with clinical features of lung cancer was analyzed. The mRNA expression of nm23-H2 gene in poorly differentiated squamous-cell carcinoma was significantly decreased compared to that in moderately differentiated squamous-cell carcinoma. The mRNA expression of nm23-H1 and nm23-H2 genes in small cell lung cancer was decreased compared to that in squamous-cell carcinoma. No significant difference in nm23 mRNA expression was observed in lung cancers with and without lymph node metastasis, nor was there significant difference in patients with lung cancers in different stages. The mRNA expression of nm23 gene is correlated with the degree of differentiation of lung cancer, but there is no evidence of metastasis suppression effect by nm23 gene.

Nm23-H1 expression in nasopharyngeal carcinoma: correlation with clinical outcome.

The expression levels of nm23-H1 mRNA and its protein in human nasopharyngeal carcinoma (NPC) were detected to clarify the relationship between nm23-H1 and metastasis and prognosis of patients with NPC. nm23-H1 mRNA expression in fresh tissues from 78 patients with NPC was investigated by in situ hybridization and RT-PCR. Routine labeling streptavidin-biotin immuno-histochemistry with the nm23-H1 murine monoclonal antibody was employed to study the expression of nm23-H1 protein in paraffin-embedded specimens from 231 patients with NPC treated in our hospital. The clinical pathologic data and results of follow-up were collected. Comparisons between expression of nm23-H1 protein or mRNA and clinical outcome were performed using the chi2 test. Multivariate prognostic analyses were performed by the Cox regression model. We found that nm23-H1-negative tumors were associated with a higher incidence of lymph-node metastasis (84.2%) than nm23-H1-positive ones (32.8%, p < 0.01). The distant metastasis and loco-regional recurrence rates in the nm23-H1-negative group were 55.8% and 31.68%, respectively but only 17.2% and 11.5%, respectively, in the nm23-H1-positive group (p < 0.01). A significant association was found between expression of nm23-H1 protein and prognosis (p < 0.01). Expression of nm23-H1 protein indicated favorable prognosis, suggesting that the absence of nm23-H1 protein expression was significantly associated with lymph-node metastasis, recurrence and distant metastasis in NPC. Expression of the nm23-H1 gene may be valuable for assessing the prognosis of NPC.

Relationship between expression of CD44v6 and nm23-H1 and tumor invasion and metastasis in hepatocellular carcinoma.

AIM:To detect the expression of CD44v6 mRNA and nm23-H1 mRNA in hepatocellular carcinoma (HCC) by in situ hybridization, and to evaluate the relationship between their expression and also relationship between their expressions and tumor invasion and metastasis.METHODS:CD44v6 cDNA probe was synthesized with PCR technique and the nm23-H1 cRNA probe by in vitro transcription. The expression of CD44v6 mRNA and nm23-H1 mRNA was detected by in situ hybridization. RESULTS:In group with high invasion and metastasis potential, the positive rates of CD44v6 mRNA and nm23-H1 mRNA were 80% (8/10) and 40% (4/10),in group with poor invasion and metastasis potential, they were 21.7% (5/23) and 91.3% (21/23).There was a positive correlation between the expression of CD44v6 mRNA and tumor invasion and metastasis potential in HCC (P < 0.01), and a reverse correlation between the expression of nm23-H1 mRNA and tumor invasion and metastasis potential (P < 0.01) and a reverse correlation in the expression between CD44v6 mRNA and nm23-H1 mRNA in HCC (P < 0.01).CONCLUSION: Detection of CD44v6 mRNA and nm23-H1 mRNA may be useful for tumor invasion and metastasis in HCC.

Role of the nm23-H1 gene in the metastasis of gastric cancer.

The nm23 gene is now generally accepted as one of the suppressor genes for metastasis in many types of human cancer. To investigate the role of the nm23 gene in gastric cancer, we examined the expression of nm23-H1 mRNA, mutations, and loss of heterozygosity (LOH) of the nm23-H1 gene in gastric cancers. The expression of nm23-H1 mRNA was examined by Northern blot analysis in eight paired sets of specimens. The expression was higher in primary cancer specimens and metastatic lymph nodes than their corresponding normal gastric mucosa in all eight sets of specimens examined, while it was similar between primary cancer specimens and metastatic lymph nodes. The mutations of the nm23-H1 gene were examined in an additional 11 sets of specimens, including eight sets of analysed by Northern blotting, by polymerase chain reaction single-strand conformation polymorphism analysis, no mutation being found in any of the 11 sets of specimens tested. LOH of the nm23-H1 gene was also examined in additional 12 sets of specimens, among which seven (58%) specimens were informative for LOH. LOH was identified in one (14%) out of these seven informative sets. These results suggest that nm23 may not be the metastasis suppressor gene and the alteration of this gene not play an important role in the process of metastasis of gastric cancer.

Regulation of NM23 gene expression in the normal and malignant trophoblast by growth factors

Summary nm23-H1 is a nucleoside diphosphate kinase with a functional role in the microtubular assembly and disassembly during cell proliferation and in G-protein dependent signal transduction. Gene expression for this kinase has been reported to be inversely correlated with metastatic ability of tumor cells. Normal trophoblast cells are highly invasive but non-metastatic. Numerous growth factors, e.g., TGF-α, EGF, TGF-β, and CSF-1, present at the fetomaternal interface, influence trophoblast functions such as proliferation, differentiation, and invasion. In this study, we investigated the influence of the above growth factors on nm23-H1 mRNA expression by first trimester normal trophoblast and two choriocarcinoma cell lines, JAr and JEG-3. The expression was found to be abundant in the normal trophoblast as well as choriocarcinomas, indicating that this expression was not suppressed in malignant trophoblast cells. We found that growth factors (e.g., TGFα, EGF, and CSF-1) which stirnulate normal trophoblast proliferation also stimulated nm23-H1 expression in the normal trophoblast indicating that the expression may be coupled with cell proliferation. A stimulatory effect noted with a neutralizing anti-TGF-β antibody can also be explained on the basis of stimulation of trophoblast proliferation due to removal of the anti-proliferative action of endogenous TGF-β. The expression of nm23H-1 in choriocarcinoma cells was unaltered by the growth factors except for some stimulation of JEG-3 cells noted with TGF-β. Since anti-TGF-β Ab also stimulated the expression in JEG-3 cells, we propose that TGF-β may have a dual influence in this case, one related to signal transduction, another to its anti-proliferation.

Nm23-H1 metastasis suppressor gene expression in primary breast cancer: associations with axillary lymph node status, tumour size, type and grade

The nm23-H1 gene has tumour suppressor functions and is a putative metastasis suppressor. Higher levels of expression of the gene in breast carcinoma have been associated with the absence of lymph node metastasis, and with longer relapse free intervals and overall survival.Expression levels of nm23-H1 in breast carcinoma were examined by Northern and slot blot in a consecutive series of 105 patients. The levels of nm23-H1 mRNA expression were examined for associations with axillary lymph node metastasis, and with tumour size, tumour type and grade, mitotic rate, nuclear size and pleomorphism and vascular invastion, in 97 cases of invasive cancer. No statistically significant differences in nm23 expression levels between axillary node negative and axillary node positive infiltrating duct carcinomas were observed. There was no correlation between nm23-H1 expression levels and other histopathologically determined prognostic factors. Higher levels of gene expression were demonstrated in pure ductal carcinoma in situ (DCIS) lesions when compared to invasive tumours; further analysis suggested that DCIS components within invasive tumours contributed to measurements of nm23 expression, possibly masking the lower expression levels of the invasive component in some cases. Further correlative studies, using in situ hybridization or gene product immunohistochemistry would be most suited to determining the contribution of different tissue components in breast cancer.

Inverse association of nm23-H1 expression by colorectal cancer with liver metastasis

The expression of nm23-H1 mRNA and protein was studied in colorectal cancers by Northern blotting and immunohistochemistry. All 21 colorectal cancers studied by Northern blotting had increased levels of nm23-H1 mRNA relative to the adjacent normal colonic mucosa. Increased nm23-H1 protein expression was also observed in all 36 colorectal cancer cases including those studied by Northern blotting. There was no significant correlation between nm23-H1 expression and tumour histology, serosal invasion, lymphatic invasion, venous invasion, or lymph node metastasis. However, the expression of both mRNA and protein was significantly lower in tumours associated with liver metastasis than in those without such metastasis. These observations indicate that the nm23 gene may play a role in the suppression of liver metastasis of colorectal cancer.

Increased nm23-H1 and nm23-H2 messenger RNA expression and absence of mutations in colon carcinomas of low and high metastatic potential.

The murine nm23 gene suppresses the metastatic behavior of malignant rodent tumor lines, and reduced nm23 expression correlates with increased likelihood of lymph node metastases in human breast cancers. More recent data have demonstrated the existence of two human nm23 gene homologues, nm23-H1 and nm23-H2, and have shown that deletion of nm23-H1 alleles occurs in some colon carcinomas associated with poor prognosis. These findings suggest that nm23-H1 encodes for suppression of colon carcinoma metastasis. In contrast, we have previously reported that total nm23 messenger RNA (mRNA) expression is increased to similar levels in colon tumors of both high and low metastatic potential. This study was designed to reconcile our previous findings with the recent report of nm23-H1 allelic deletion in human colon cancers associated with poor prognosis. Our purpose was to examine human colon cancers for inactivation of two candidate metastasis suppressor genes, nm23-H1 and nm23-H2, either by mutation or by loss of gene transcription. We used ribonuclease protection assays to analyze human colon tumors for the level of nm23-H1 (43 samples) and nm23-H2 (41 samples) transcript (mRNA) expression and the presence of mutations that could inactivate potential suppressor function. We detected only wild-type nm23-H1 and nm23-H2 mRNA. Expression of nm23-H1 mRNA increased in 33 of 41 colon tumors, and expression of nm23-H2 mRNA was elevated in 28 of 41 colon tumors relative to that in matched normal mucosa. Increases in these mRNA levels were similar in tumors of both low and high metastatic potential. These results suggest that, despite correlation of nm23-H1 allelic deletions with colon cancers associated with poor prognosis, nm23-H1 and nm23-H2 alleles do not directly mediate metastasis suppression in colon carcinoma. Our results leave unexplained the observation that nm23-H1 allelic deletion correlates with metastatic potential of colon carcinomas. These findings also contrast with the demonstration of nm23 metastasis suppressor activity in murine melanoma and with the correlation of loss of nm23 expression in breast cancer with poor prognosis. It may be that metastasis suppression by the nm23 gene is a tissue-specific phenomenon.