Nm23 Gene Product Research Articles

Nuclear localization and intensity of staining of nm23 protein is useful marker for breast cancer progression

BackgroundBreast cancer is the most common cause of cancer death in the western world. The expression differences of many proteins are associated with breast cancer progression or suppression. The purpose of the study was to determine the expression of nm23 protein in the invasion status and metastatic potential of breast cancer by using tissue microarray and to determine its role in breast cancer based on the expression of nm23 gene product.Methodnm23 protein expression was examined by immunohistochemistry (IHC) using commercially available tissue microarray containing malignant and normal breast tissues from 216 patients.Resultsa similar percentage of cases showed positive cytoplasmic/nuclear staining for nm23 in normal breast tissue (85.7%), primary breast carcinoma node negative (97.5%) and carcinoma with lymph node metastasis (92.1%). Nuclear localization of staining for nm23 protein was higher in infiltrating ductal carcinoma (IDC) node positive (24.3%) and in matched lymph mode metastasis (18.9%) compared to IDC node negative (4.9%). Strong intensity of cytoplasmic/nucleus staining was observed in IDC node negative (42.6%), in IDC node positive (57.1%), and Infiltrating lobular carcinoma (ILC) node negative (44%) compared to normal breast tissue (16.7%).Conclusionnm23 protein expression appears widely expressed in normal breast, early and advanced breast cancer stages. Interestingly our study found that strong staining intensity and nuclear localization of nm23 protein may prove to be a useful marker of breast cancer progression.

Prognostic significance of nm23 gene product expression in patients with colorectal carcinoma treated with radical intent

Reports of the relationship between the putative metastasis suppressor NM23 and metastasis and/or survival in colorectal cancer patients are conflicting. This study aimed to investigate whether nm23 immunostaining is correlated with established prognostic variables (Dukes' stage, degree of tumour differentiation, T stage and nodal involvement) in colorectal carcinomas for the patients treated with radical intent using Kruskal chi(2) analysis. The rates of survival at five years were estimated with the use of the Kaplan-Meier product-limit method with 95% confidence intervals derived by Greenwood's formula and the curves were compared with the use of the log-rank test. Cox proportional-hazard regression model was used to identify multivariate predictors and the corresponding outcome. The staining was performed on 112 paraffin-embedded surgical specimens collected between 1989-1992 using a monoclonal anti-nm23 antibody. Follow-up of patients was until time of death or for at least 5 years. There was not a significant correlation between tumour staging, degree of tumour differentiation, nodal involvement and nm23 status. Furthermore, there was no significant association with overall 5-year survival, disease recurrence, tumour site, age or sex. Although nm23 may be involved in suppressing tumour metastasis, nm23 immunohistochemistry has no prognostic value in colorectal cancer. For these reasons nm23 does not contribute further to the prognostic information provided by established prognostic variables.

The relationship between expression of c-ras, c-erbB-2, nm23, and p53 gene products and development of trophoblastic tumor and their predictive significance for the malignant transformation of complete hydatidiform mole.

The aims of this retrospective study by means of immunohistochemical staining were (1) to study the expression of c-ras, c-erbB-2, p53, and nm23 gene products in complete hydatidiform moles that progress to gestational trophoblastic tumor and in those that remit spontaneously after evacuation, and (2) to estimate the predictive value of the expression of these four gene products in malignant transformation of complete hydatidiform mole. Clinical data of patients with complete hydatidiform mole were obtained by retrospective chart review. Formalin-fixed paraffin sections of 50 cases of complete mole that progressed to gestational tumor and 32 cases of complete mole that remitted spontaneously were studied immunohistochemically for c-ras, c-erbB-2, p53, and nm23 proteins. The prognostic value of the proteins for the malignant transformation of complete mole was analyzed by multiple logistic regression and stepwise logistic estimation. Sections of 30 cases of invasive mole and 19 cases of choriocarcinoma were also immunohistologically studied for expression of the proteins. Expression of c-erbB-2 and p53 gene products was significantly increased and expression of nm23 and c-ras products was remarkably decreased in complete hydatidiform moles that progressed into postmolar tumor compared with those that remitted spontaneously after evacuation. There was no significant difference in the expression of the four genes in invasive mole and in choriocarcinoma. A logistic estimation model for predicting malignant transformation of complete mole was established based on the expression of gene products. When the expression of four gene products was used, the predictive sensitivity of the regression model was 86.0%, and the specificity was 75.0%. The positive predictive value was 84.3%, the negative predictive value was 77.4%. Logistic stepwise regression analysis showed that the altered expression of c-erbB-2 and nm23 products had strong predictive value, while the expression of c-ras and p53 products had no significant predictive value for the malignant transformation of complete mole. The altered expression of c-ras, c-erbB-2, nm23, and p53 gene products may be important in the pathogenesis of gestational trophoblastic tumor. The decreased expression of nm23 protein and increased expression of c-erbB-2 protein are strong predictors for the malignant transformation of complete mole.

Nm23 Gene Product Expression in Invasive Breast Cancer

The nm23 gene/protein is a putative metastatic suppressor identified a decade ago in a melanoma cell line. A number of laboratory, clinical and pathological studies have been carried out to define its real biological and biochemical function as a step in a complex metastatic process. In our study we examined the significance of nm23 expression in 164 breast cancer patients, aged 35 to 74 years, in comparison to other parameters such as age, menopausal status, histological grade, tumor size, lymph node status, and hormone receptor status. Overall survival (OS) and disease-free survival (DFS) were analyzed. The median follow-up was 84 months. Significant changes in OS were found for tumor size, nodal involvement and histological grade but there was no convincing correlation with nm23 expression. When patients were stratified according to nm23 expression, it was shown that overall survival in nm23 -positive patients was no longer than that in nm23 negative patients. It was also shown that patients who were lymph node negative and older than 50 years had longer OS than nm23 -negative patients. A statistical analysis shows that there is a correlation between axillary node status and nm23 expression (p = 0.018) as well as between patients' ages and nm23 expression (p = 0.043). There was no statistically significant correlation between nm23 expression, lymph node status and their combination on DFS.

Expression of nm23 antimetastatic gene product in head and neck squamous cell carcinoma

The nm23 gene has been implicated as a suppressor gene involved in the control of the metastatic process of malignant cells. Reduced levels of nm23 gene product have been found in tumor cells with high metastatic potential such as several types of rodent tumors and human breast, colorectal, and lung carcinoma. This pilot study examines the expression of the nm23 gene product compared with nodal status in 70 consecutive patients with squamous cell carcinomas of the head and neck. Immunohistochemical staining was carried out on these tumor tissues with a monoclonal antibody to nm23-H1 peptide sequence. The tissues were scored from 0 to 2 by 2 independent observers. Reduced immunoreactivity, grades 0 and 1, was observed in 30 patients with positive nodal status (N = 34, 88%). Strong immunoreactivity, grade 2, was observed in 20 patients with negative nodal status (N = 36, 56%). Reduced expression of nm23 gene product was observed in patients with positive lymph node metastasis ( P = 0.0006, χ 2). However, no significant differences in survival of these groups based on nm23 expression could be shown with the Kaplan-Meier analysis. This initial finding in the difference of nm23 gene product expression in patients with differing lymph node status is exciting but must be further validated with future studies. (Otolaryngol Head Neck Surg 2000;122:96-9.)

Clinical significance of nm23 expression in renal cell carcinoma.

In many tumors an expression of nm23 gene products is associated with a lower metastatic potential. The aim was to evaluate whether nm23 gene expression in renal cell carcinoma was associated with clinicopathological findings and survival. In 41 patients, the expression of nm23 protein was analyzed in tumor and corresponding kidney cortex tissue by immunohistochemical analysis using a monoclonal nm23-H1 antibody. In all kidney cortex samples intense nm23 staining was found. Of 41 tumors, 15 had high, 12 intermediate, 5 low nm23 expression whereas 9 tumors showed none. There were no differences in nm23 staining between different stages, grades or size of tumor. No correlation between survival and nm23 expression was observed. However, diploid tumors had significantly less nm23 staining compared with aneuploid tumors, indicating that nm23 gene inactivation might be a favorable sign. The expression of nm23 gene products seems not to be correlated to tumor progression and metastatic ability in renal cell carcinoma.

Expression of nm23 in Normal, Hyperplastic and Neoplastic Endometrial Tissues

This study evaluated the expression of nm23 in curettage specimens from 63 cases of normal, hyperplastic and neoplastic endometrial tissues by immunohistochemistry. The histological diagnoses were as follows: normal proliferative (N = 5) or secretory (N = 5), simple hyperplasia (N = 11), complex hyperplasia (N = 9), atypical hyperplasia (N = 8) and adenocarcinoma (N = 25), consisting of endometrioid adenocarcinoma (N = 15), clear cell (N = 7) and serous papillary adenocarcinoma (N = 3). There was no immunostaining for nm23 protein in the 10 cases of normal endometria and in the 28 cases of endometrial hyperplasia. In contrast, 52% of the adenocarcinomas displayed a cytoplasmic staining pattern which was moderate to strong. This difference was statistically significant (p < 0.0001, chi-square test). nm23 expression in curettage specimens had no predictive value for determining the FIGO stage in the hysterectomy specimens (p = 0.2709, chi-square test). No significant difference for nm23 immunoreactivity was found between the histologic subtypes of endometrial adenocarcinoma (endometrioid versus serous papillary and clear cell, p = 0.1413, chi-square test). In this study, there was no immunostaining of normal endometria or of endometrial hyperplasia (including atypical endometrial hyperplasia) to support the hypothesis that expression of the nm23 gene product is related to the development of endometrial adenocarcinoma. In contrast, nm23 expression was upregulated in many cases of endometrial adenocarcinomas irrespective of the histologic subtype.

Heterogeneous expression of nm23 gene product as a predictor of lymph nodal status in human breast cancer.

The nm23 gene was originally identified by differential hybridization of metastatic murine melanoma cell lines. Some experimental studies demonstrated a significantly low metastatic potential of melanoma cell lines transfected with the nm23 gene. In this study, we clarified the relationship between intracellular nm23-immunoreactivity and lymph nodal status of human breast cancer. We analyzed 82 surgically removed breast tumors including 67 invasive carcinomas (ductal, lobular and mucinous carcinomas). The nm23 expression was diffusely positive in the benign tumors and non-invasive carcinomas. Of the invasive ductal carcinomas, lymph node metastasis was found in 67.7% (21/31) of the focally positive/negative cases and in 18.2% (4/22) of the diffusely positive cases (p<0.001). Immunohistochemically, advanced margins of invasive carcinomas with lymph node metastasis were shown to be negative for nm23 expression, while intraductal carcinoma components were positive. This observation suggested that focally positive/negative nm23 expression can be a predictor of lymph node metastasis of invasive ductal breast carcinoma.

NM23 gene product expression does not predict lymph node metastases or survival in young patients with colorectal cancer.

NM23 gene product is a putative metastases suppressor gene which has structural homology to a nucleoside diphosphate kinase. Previous studies examining the relationship between NM23 gene product expression and survival in patients with colorectal cancer have revealed conflicting results. However, no study has focused on young patients with colorectal cancer. This study was carried out to determine if expression of the NM23 gene product was correlated with metastatic potential and survival in young patients (45 years and under) with colorectal cancer. Eighty- one patients with colorectal cancer were studied and the presence of the NM23 gene product (H1) was detected using standard immunohistochemical techniques. NM23 gene product expression did not correlate with tumour stage, lymph node involvement by tumour, presence of distant metastases, extramural vascular invasion or degree of tumour differentiation. Independent risk factors for overall survival were: Dukes' stage (p=0.00001) and extramural vascular invasion (p=0.003). NM23 expression was not an independent prognostic indicator (p=0.55). Therefore, NM23 expression does not correlate with existing indicators of tumour aggressiveness and behaviour nor is it an independent predictor of survival in young patients with colorectal cancer.

C- erbB-2, p53, and nm23 gene product expression in breast cancer in young women: Immunohistochemical analysis and clinicopathologic correlation

We studied c- erbB-2, p53, and nm23 gene products in 112 primary breast carcinomas. Fifty patients were aged 35 years or younger, and 62 were aged 36 to 50. Clinicopathological criteria including clinical stage, hormone receptor status, histological types, histological grades, and lymph node status, were reviewed. Disease-free survival (DFS) and overall survival (OS) were analyzed. Immunohistochemical findings were assessed semiquantitatively. Correlation between clinicopathological criteria, survival data, and immunohistochemical findings have been made. Patients aged younger than 35 years with stage I to II disease had a shorter DFS ( P = .03) than older patients. However, no other clinicopathological finding was associated with age. Neither was there association between age and c-erbB-2, p53, or nm23 patterns of expression. p53 positivity was associated with high histological grade ( P = .003) and with progesterone receptor negativity ( P = .045). Nm23 nuclear positivity was associated with early clinical stages ( P = .011) and with absence of axillary lymph node metastasis ( P = .007). p53 and c-erbB-2 overexpression were associated with shorter OS while nm23 nuclear positivity was associated with longer OS in univariate and multivariate analyses. Univariate analyses showed that c-erbB-2 or nm23 were potentially important prognostic factors in women aged 35 years or younger while p53 was associated with prognosis in women aged 36 to 50. Cox model analysis indicated that c-erbB-2 alone was associated with prognosis in women 35 years and younger, whereas p53 alone was associated with prognosis in 36-to 50-year-old women. These results suggest that breast cancer in the youngest women has some biological specificity.

Evaluation of immunostaining for MIB1 and nm23 products in uterine cervical adenocarcinoma.

In this study, we evaluated whether proliferative activity and metastatic potential are prognostic factors in adenocarcinoma of the cervix. Formalin-fixed, paraffin-embedded sections from 34 patients with cervical adenocarcinoma or adenosquamous carcinoma were immunostained with monoclonal antibody MIB1, expressed in proliferating cells, and anti-nm23 antibody, reacts with metastasis suppression gene products. MIB1 positivity ranged from 0.2 approximately 54.7% with a mean of 21.4%. The level did not differ significantly between various clinicopathological categories. Although patient survival of high or low MIB1 expressing tumor was not significantly different, the disease-free interval of high (> or =25%) expressing tumor was significantly lower than that of low (<25%) expressing tumor. Strong and medium expression for nm23 were detected in 7 (21%) and 3 (9%) of patients. Tumor with strong nm23 expression tended to have a higher relapse rate. Although the survival of strong and weakly nm23 expressing tumor was not significantly different, the disease-free survival of strong nm23 expressing tumor was lower than that of weakly nm23 expressing tumor. MIB1 and nm23 immunostaining might be some of prognostic indicators of recurrence in cervical adenocarcinoma. In cervical adenocarcinoma, the nm23 gene products may not function as metastatic suppression but reflect proliferative activity.

Nm23/PuF Does Not Directly Stimulate Transcription through the CT Element in Vivo

Decreased levels of the nm23 gene product have been correlated with increased tumor metastatic potential in a variety of malignancies. At least a subset of the regulatory properties of Nm23 has been proposed to be due to transactivation of the human c-myc oncogene through binding to a homopyrimidine tract 140 base pairs upstream of the transcription start site (termed the CT element or the PuF site). Conventional transcription factors possess DNA binding and transactivation domains; Nm23 fusion proteins were used to address two questions. First, if provided with a well characterized DNA binding domain, does Nm23 possess a transactivation domain capable of stimulating transcription of an appropriate reporter? Second, if provided with a potent transactivation domain, is the DNA binding of Nm23 of sufficient specificity and affinity to direct the fusion protein to a CT-dependent reporter? Since reporter gene expression was not stimulated in either case, we conclude that Nm23 does not directly stimulate transcription through binding to the CT element and that its antimetastatic and other reported functions are likely due to other biochemical activities.

Immunohistochemical expression of nm23 gene product, nucleotide diphosphate kinase, in pancreatic neoplasms.

Our findings suggest that contrary to the proposed role for the nm23 protein as a tumor metastasis suppressor, in pancreatic tumors, the nm23 protein does not play an important role as a suppressor against tumor metastasis. The nm23 gene product, nucleotide diphosphate kinase, is believed to suppress tumor metastasis. Although a number of studies on many kinds of tumors have examined the relationship between nm23 expression and metastatic potential, the antimetastatic activity of nm23 remains controversial. The expression of the nm23 protein has not been examined in pancreatic tumors, except for a few reports on pancreatic duct cell carcinomas. We have investigated nm23 expression in pancreatic duct cell carcinomas, islet cell tumors, and ampullary carcinomas by immunohistochemical methods. In 73 cases of pancreatic duct cell carcinomas, the nm23 expression was increased when compared with the adjacent normal pancreatic ducts; diffuse immunostaining was detected in 21 (29%) cases, focally positive immunostaining in 47 (64%) cases, and negative immunostaining in 5 cases (7%). All five negative samples were obtained from distant metastatic regions. However, there was no significant difference in the nm23 expression between primary tumors and regional lymph node metastases. Furthermore, there was no significant correlation between nm23 expression and the prognosis of the 55 resected cases. In the 15 cases of ampullary carcinomas, all 15 tumors were positive for nm23 protein (6 diffuse and 9 focal), and the staining intensity was stronger than in normal pancreatic ducts. There was no significant difference in the nm23 expression in the primary regions between patients with and without lymph node metastasis (2 diffuse and 5 focal out of 7 patients with lymph node metastasis, and 4 diffuse and 4 focal out of 8 patients without lymph node metastasis). All 12 islet cell tumors showed strong and diffuse staining for the nm23 protein.

Expression of nm23/Nucleoside Diphosphate Kinase-A Protein in Endometrial Carcinoma

A metastatic tumor suppressor role for the nm23 gene product in breast carcinoma has been proposed. The biologic significance of nm23/NDP kinase-A (NDPK-A) expression in endometrial carcinoma remains undetermined. We sought to (1) characterize the pattern and intensity of nm23 protein expression in endometrial carcinoma and (2) assess the relationship between intensity/pattern of nm23 protein immunostaining and treatment response assessed by progression-free survival and survival to death. Formalin-fixed paraffin-embedded sections from 234 patients with endometrial cancer were immunostained with a mouse monoclonal IgG to nm23/NDPK-A protein. In most specimens of endometrial carcinoma (67.5%), nm23 expression was strongly upregulated. No association was found between either intensity (0 vs 1, 2, 3) or pattern (nuclear membrane vs cytoplasmic) of immunostaining and FIGO stage, ploidy status, histologic subtype, myometrial invasion, progression-free survival, or survival to death. Absence of nm23 staining (0 vs 1, 2, 3) was significantly associated with lower tumor grades (P= 0.02). For stage I patients, moderate to strong nm23 immunostaining intensity (2>, 3) was associated with a trend toward diminished progression-free survival (P= 0.08). Our data imply a heterogeneity of nm23 protein expression and possible distinct biologic roles for nm23 in endometrial compared with breast or ovarian carcinoma.

Immunohistochemical study on the nm23 gene product (NDP kinase) in oral squamous cell carcinoma

The nm23 gene is a potential metastasis suppressor gene originally identified using a murine melanoma cell line. Immunohistochemical investigation on the role of nm23 gene product (nucleoside diphosphate kinase: NDPK) in squamous cell carcinomas of the oral cavity was performed and compared to clinical and histopathological factors. The stainability of NDPK did not correlate to tumour extent, differentiation and mode of invasion. However, the NDPK positive group tended to have a lower frequency of lymph node metastasis, and a better prognosis than the NDPK negative group. Consequently, nm23/NDPK is suggested to be a metastasis suppressor factor that may be useful for predicting tumour metastasis and prognosis in oral squamous cell carcinoma.

An immunohistochemical analysis of nm23 gene product expression in uveal melanoma.

Uveal melanoma is characterized by an unpredictable clinical course, during which metastatic disease may occur after a prolonged and, at present, undefinable disease-free interval. Because of its relative rarity and the dispersion of cases, the possible genetic alterations implicated in the invasive and metastatic behaviour of this ocular neoplasm have not yet been characterized. The aim of this immunohistochemical retrospective study was to assess the expression of nm23 gene product, proposed to be a metastasis-suppressor gene, in uveal melanoma and to analyse its prognostic significance in relation to the various conventional histopathological parameters, currently considered the major prognostic indicators in this intra-ocular neoplasm. We analysed formalin-fixed paraffin-embedded samples excised from 33 patients with uveal melanoma. Of these, 22 (67%) were positive for monoclonal antibody nm23. This nm23 positivity was inversely associated with scleral invasion level (P = 0.001) and largest tumour diameter (P = 0.02), which represent the two most significant prognostic factors for metastasis. On the other hand, there was no correlation between nm23 expression and other prognostic markers such as cell type, intraocular location or clinical characteristics. These results may suggest a close relationship between nm23 gene expression and metastatic potential of uveal melanomas. In addition, analysis of nm23 gene expression on bioptic tissue may represent an extreme useful prognostic tool for metastatic progression of uveal melanomas.

Expression of the nm23 metastasis-suppressor gene product in skin tumors.

Nm23 is a gene with a putative metastasis-suppressor function, whose expression is inversely correlated with the metastatic potential of some solid malignancies. Because very few data exist concerning the role of nm23 in skin tumors, we studied the immunohistochemical expression of nm23 gene product in frozen sections of normal skin and of 104 cutaneous benign or malignant, epithelial and mesenchymal tumors. Nm23 was found expressed within basal cells of the epidermis and its appendages. All basal cell carcinomas showed diffuse immunoreactivity predominating within cells located at the periphery of tumor masses; in contrast, most squamous cell carcinomas, premalignant lesions and the benign epithelial lesions studied showed very weak, if any, immunoreactivity. Benign nevi and most malignant melanomas expressed nm23 immunoreactivity and the pattern observed was similar between primary and metastatic lesions. These results show that nm23 is differentially expressed in cutaneous tumors. It seems likely that the strong immunoreactivity of basal cell carcinomas, contrasting with the almost non-expression in squamous cell carcinomas, reflects the different metastatic potential of these two types of tumors. In melanomas, no direct correlation between the metastatic phenotype and nm23 expression could be detected. Our results suggest that the nm23 gene is involved in cutaneous carcinogenesis; its precise role deserves further study.

Expression of metastasis suppressor gene product, nm23 protein, is not inversely correlated with the tumour progression in human malignant melanomas.

An inverse correlation between the nm23 RNA level and tumour progression of melanocytes has been reported. To elucidate whether the expression of nm23 gene product in malignant melanoma is also inversely correlated with metastatic potential, conventional prognostic parameters or the tumour suppressor protein p53, immunohisto-chemical studies using a monoclonal antibody against nm23-H1 protein were performed on 138 benign and malignant melanocytic tumours. The expression of nm23 protein was compared with that of p53 protein and conventional clinicopathological prognostic factors. The nm23 protein level in benign melanocytes and metastatic melanoma cells was also studied by Western blot analysis. No significant difference regarding the protein was observed between naevi and melanomas, either at histological or protein levels. The expression correlated with local recurrence within 1 year after surgery, level of invasion and tumour thickness, but no parallels were observed between the nm23 and p53 proteins, suggesting that gene is regulated by independent mechanisms, although located on the same chromosome. There was no inverse correlation between the nm23 protein and melanoma metastasis which suggested that the nm23 protein does not appear to be lost during melanoma metastasis.

Immunohistochemical analysis of the nm23 gene product (NDP kinase) expression in astrocytic neoplasms.

The expression levels of nm23-H1 have been reported to correlate with the metastatic potential of some tumours. We have treated a child with a rare case of astrocytoma with diffuse osteoblastic metastases. We therefore decided to examine the expression of the nm23 gene product in 24 gliomas in order to clarify the association of its expression with the clinical features of the disease. A polyclonal antibody against a GST/nm23-H1 fusion protein was raised in rabbits. Twenty-four specimens, including 5 recurrent gliomas and one extraneural metastasis, were obtained from 19 patients treated surgically between 1990 and 1993 in our hospital. Immunohistochemical staining was performed on paraffin sections using an avidin-biotinyl peroxidase complex method. Of the 24 astrocytic neoplasms, 3 (12.5%) specimens from one patient with diffuse bony metastases stained intensely with nm23-H1. Two specimens obtained from glioblastoma multiforme patients stained weakly. The other 19 specimens were negative for nm23-H1 expression. Little or no nm23 expression was observed in adjacent nontumourous cerebral tissues. The results suggest that high levels of nm23 expression might correlate with extraneural metastatic potential in astrocytic neoplasms.

Immunohistochemical analysis of nm23 protein in transitional cell carcinoma of the bladder.

To elucidate the clinical significance of the nm23 gene product in transitional cell carcinoma (TCC) of the bladder. The immunoreactivity of nm23 protein and proliferating cell nuclear antigen (PCNA) were evaluated in paraffin-embedded tumour samples obtained from 74 patients with TCC of the bladder who underwent total cystectomy between 1981 and 1993 and compared with the histological findings and clinical outcome. The immunoreactivity of nm23 protein was positive near basement membrane in normal transitional epithelium and superficial TCCs; it could also be positive at the invasive front of TCCs. The immunoreactivity of nm23 protein in TCCs was significantly higher than that in normal transitional epithelium and correlated significantly with the expression of PCNA and with histological grade. Similarly, immunoreactivity was significantly higher in invasive TCCs than in superficial TCCs; however, there was no significant difference between superficial TCCs and normal transitional epithelium. Immunoreactivity of nm23 protein was not associated with the early development of metastasis after radical surgery or with a favorable clinical outcome. Immunoreactivity of nm23 protein appeared to be associated with the proliferation and progression of TCC of the bladder. The potential role of nm23 as a suppressor of the metastatic activity of tumours was less prominent, partly because of mutations of nm23 in TCCs of the bladder.