
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Molecular Oncology, Markers, Clinical Correlates |
Department of Tumor Biology, Institute for Cancer Research [G. M. M., Ø. F.] and Department of Pathology [R. H., J. M. N., V. A. F.], The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway
| ABSTRACT |
|---|
|
|
|---|
Experimental Design: Expression of ß-catenin was examined by immunohistochemistry in 106 superficial and 58 nodular spreading primary melanomas, as well as in 66 metastatic lesions.
Results: Membrane-associated staining was detected in nearly all of the cases, and no association to clinical parameters could be revealed. When cytoplasmic localization of the protein was recorded, a significant higher fraction of the superficial than the nodular spreading primary lesions expressed the protein in the majority of the cells (P < 0.0001). Interestingly, metastatic lesions from superficial melanomas demonstrated down-regulated expression of the protein, and in agreement with this a significant inverse correlation between protein expression and the vertical thickness of the primary lesion was detected (P = 0.012). Furthermore, a significant correlation between cytoplasmic localization and disease-free survival (P = 0.0006) was revealed, but ß-catenin did not have any significant impact on overall survival for this group of patients (P = 0.0824). No association was detected between ß-catenin expression and clinicopathological parameters in the nodular subgroup of melanomas, indicating that the protein may play different roles in the malignant progression of the two main types of melanomas.
Conclusion: In summary, we hypothesize that cytoplasmic ß-catenin has a protective role in early melanoma development.
| INTRODUCTION |
|---|
|
|
|---|
Molecular changes increasing the stability of ß-catenin in the cytoplasm can presumably enhance the Tcf/Lef transcriptional activity. Thus, deregulation of the Wnt pathway has been shown to occur by several different mutational mechanisms in human cancer (2 , 9) . Inactivating mutations in the APC tumor suppressor protein, and also mutations in AXIN 1 and 2 (10) , appear to inhibit formation of a functional GSK3ß/APC/AXIN/ß-catenin complex (9) . Hence, APC mutations have been found in 7080% of human colorectal carcinomas and also in a subset of other cancers (11 , 12) , including melanoma cell lines (13) . APC mutations have been observed in melanocytic lesions in vivo, but the frequency seems to be very low (14) . In addition, mutations in the NH2-terminal part of the ß-catenin gene, encoding the phosphorylation sites for GSK3ß, making the protein resistant for phosphorylation-induced proteasomal degradation, have been reported in several types of cancer (2, 3, 4) . Such mutations have also been found in melanoma cell lines but are rarely observed in melanocytic lesions (15 , 16) .
Expression of N-, P-, and E-cadherin, as well as ß- and
-catenin has been examined previously by immunohistochemistry in a small cohort of melanocytic nevi, and primary and metastatic malignant melanomas (17)
. The most striking finding was loss of membranous P-cadherin and ß-catenin in the metastatic compared with the primary lesions. In agreement with this, Kageshita et al. (18)
compared the protein expression of ß-catenin in melanocytic lesions and reported loss or down-regulation of the protein in the more advanced tumors. In both of these studies a change in the intracellular localization of ß-catenin was observed. In the former study, the subgroup of the included primary melanomas (n = 40) was not indicated, whereas the latter cohort mostly consisted of acral lentiginous melanomas (58%), a quite common skin disease in the Japanese population but rare in the white-skinned Caucasians. As stated by Osborne (19)
, it is, therefore, of great interest to examine whether the same association between ß-catenin expression and disease progression could be detected in other types of primary melanomas.
| MATERIALS AND METHODS |
|---|
|
|
|---|
Immunohistochemical Staining.
Sections of formalin-fixed, paraffin-embedded tissue were immunostained using the streptavidin-peroxidase method (Supersensitive Immunodetection System, LP000UL; Biogenex, San Ramon, CA) and the Optimax Plus Automated Cell Staining System (Biogenex). Deparaffinized sections were microwaved in 1 mM EDTA (pH 8.0) for 2 x 5 min at 800W to unmask epitopes. After treatment with 1% hydrogen peroxidase for 10 min to block endogenous peroxidase, the sections were incubated subsequently with a 1:2000 dilution of monoclonal ß-catenin antibody (Transduction Laboratories, Lexington, KY) for 1822 h at room temperature. The sections were thereafter incubated with biotin labeled secondary antibody (1:30) and streptavidin-peroxidase (1:30) for 20 min each. Tissue was stained for 5 min with 0.05% 3,3'-diaminobenzidine tetrachloride freshly prepared in 0.05 M Tris-HCl buffer (pH 7.6) containing 0.024% hydrogen peroxidase, and then counterstained with hematoxylin, dehydrated, and mounted in Diatex. All dilutions of antibody, biotin-labeled secondary antibody, and the streptavidin-peroxidase were made with PBS (pH 7.4). Positive and negative controls were included, the latter obtained by replacement of the monoclonal antibody with mouse myeloma protein of the same subclass and concentration as the monoclonal antibody. All the controls gave satisfactory results. Four semiquantitative categories were used to describe the number of positively stained cells: (-), none; (+), <5%; (++), 550%; and (+++), >50%. Membranous, cytoplasmic, and nuclear staining were recorded individually.
Statistical Analysis.
The relationship between tumor thickness and the expression of ß-catenin was evaluated nonparametrically using the Mann-Whitney test, whereas comparisons between ß-catenin and cell cycle factors were performed using Pearson
2 test. Kaplan-Meier survival estimates and log-rank test were used to evaluate the survival data. A value of P < 0.05 was considered as statistically significant. The Cox proportional hazards model was used to determine independent prognostic variables for disease-free survival. Tumor depth, type, and localization of the primary tumor, sex, and age, in addition to ß-catenin expression level, were included in the final Cox model. All of the statistical evaluations were performed according to the SPSS statistical package.
| RESULTS |
|---|
|
|
|---|
|
|
Seven melanocytic nevi were included in the analysis, and five of these demonstrated positive immunostaining both associated with the plasma membrane and also in the cytoplasm in the majority of the cells (Table 1)
. None of the examined cases expressed the protein in the nucleus.
Immunohistochemical Expression of ß-Catenin in Relation to Clinical Parameters.
The immunohistochemical staining of ß-catenin was examined in relation to clinical parameters of melanoma progression. A high percentage of the examined cells demonstrated extended positive immunostaining; thus, staining in >50% of the cells has been defined as cases demonstrating high protein expression. When relating the cytoplasmic localization of ß-catenin to the thickness of the primary lesion, a significant correlation between high protein expression and thin lesions was observed in the superficial spreading subgroup (Table 2
; P = 0.012). No such relationship was found for the nodular spreading melanoma subgroup. The membrane-associated localization of the marker did not show any correlation to the vertical growth of the primary lesions in either of the two subgroups (Table 2)
.
|
|
In the nodular spreading subgroup of the biopsies the only association observed was an inverse correlation between cyclin D3 and cytoplasmic ß-catenin (P = 0.034).
| DISCUSSION |
|---|
|
|
|---|
Our results are in agreement with previous studies demonstrating loss of ß-catenin expression associated with melanoma progression (17 , 18) . However, the three studies can not be compared directly, because the melanoma subgroups were not indicated in one of the investigations (17) , and the second study (18) was performed on a panel mostly consisting of acral lentiginous melanomas. In agreement with Sanders et al. (17) , we did not observe ß-catenin staining in the nucleus of the examined benign nevi, even when the sections demonstrated high expression of the protein in the cytoplasm. In contrast with our findings, both the previous studies reported changes in intracellular localization of ß-catenin in more advanced tumors, but the sites of expression were not consistent. Whereas in most primary acral lentiginous melanomas the protein was localized only in the cytoplasm (18) , the primary lesions examined by Sanders et al. (17) demonstrated positive immunostaining at the plasma membrane. In both studies a higher percentage of mixed cytoplasmic and membranous staining were reported in the metastatic lesions, meaning that acral lentiginous melanomas were reported to lose cytoplasmic expression, whereas the melanomas examined by Sanders et al. (17) were reported to lose membranous expression of the protein, concomitant with disease progression.
In sharp contrast with both of these previous studies, but in accordance with recent results from Reifenberger et al. (14) , nearly all of our examined cases, both benign nevi and malignant melanocytic lesions, showed variable ß-catenin staining associated with the plasma membrane. The differences in intracellular localization can be explained by the fact that different antibodies were used and also by differences in the category of melanocytic lesions examined. However, altogether the results indicate that down-regulation of cytoplasmic ß-catenin during disease progression is a common pattern in acral (18) and superficial spreading melanomas.
An association between accumulated ß-catenin protein expression and favorable prognosis has been reported also in ovarian (24) and hepatocellular carcinoma (25) . In both studies, elevated levels of mutated ß-catenin in the nucleus was shown to be a significant predictor of prolonged patient survival. Only a very small proportion of our melanomas demonstrated nuclear localization of the protein, and no attempt has been made to examine whether the CTNNB1 gene is mutated in the lesions with elevated protein levels. Nevertheless, together these studies argue for the possibility that extended expression of ß-catenin in early carcinogenesis might be a favorable parameter.
Highly relevant to our results, showing a link between high levels of ß-catenin staining and good prognosis, is a recent paper demonstrating induction of apoptosis following ß-catenin transfection into fibroblast, as well as melanoma and colorectal carcinoma cells (26)
. ß-Catenin-induced apoptosis in the transfected cells was independent of Tcf transcriptional activity and cell cycle/apoptosis regulators like p53, E2F1, and Rb, suggesting that overexpressed ß-catenin might bind other proteins through a potential death domain (26)
. Furthermore, it has been shown that overexpression of several members in the Frizzled-Dishevelled cascade, including ß-catenin, can induce apoptosis after transfection into COS7 and 293 cells (27)
. A link between GSK3ß activity, nuclear factor
B signaling, and cell survival has been published previously (28)
. Inhibition of GSK3ß activity, causing accumulation of cytoplasmic ß-catenin and simultaneous inhibition of nuclear factor
B survival signals, might, therefore, be an alternative hypothesis explaining the high expression of ß-catenin in early melanomas.
Our data indicate that ß-catenin is lost or down-regulated in more advanced tumors. Mutations and unusual splicing of ß-catenin mRNA, as well as mutations in the APC gene, has been reported in melanoma cell lines and taken as favorable for increased stability of the protein (13) . However, the possibility still exist that gene aberrations might have the opposite effect, causing a decrease or complete loss of the encoded protein. Furthermore, cytoplasmic localization of ß-catenin is regulated by proteasomal degradation. Thus, all molecular changes enhancing the activity of the GSK3ß/AXIN/APC complex, labeling ß-catenin for degradation and increasing the proteasomal activity, will subsequently cause a down-regulation of the protein. Finally, less Wnt-receptor activity, causing decreased downstream signaling, will accelerate ß-catenin degradation and cause lower expression of the protein in the cytoplasm. Whether the observed down-regulation of ß-catenin in the advanced superficial melanomas can be explained by any of these postulated mechanisms remains to be investigated.
One of the well-known transcriptional targets for Tcf/Lef is cyclin D1 (7) . Surprisingly, in the panel of superficial melanoma biopsies a significant inverse correlation between cytoplasmic localization of ß-catenin and cyclin D1 was observed. High expression of ß-catenin concomitant with low expression of cyclin D1 in early melanomas is indicative of low proliferative activity, which is also manifested by low level of the proliferation marker Ki-67. It has been reported that Tcf can be acetylated by CBP, thereby abolishing the ability to interact with ß-catenin and to activate transcription (29) . In addition, Tcf activity can be inhibited by the transcriptional repressor Groucho (30 , 31) . Whether CBP or Groucho activity is present in the melanomas, and, thus, may be responsible for the lack of a positive correlation between ß-catenin and cyclin D1 expression, is not known. Furthermore, in the nodular subtype of melanoma a significant inverse correlation between cytoplasmic localization of ß-catenin and cyclin D3 was revealed. To our knowledge this is the first time an association between these two proteins has been reported, and no attempt has been made to study this further.
An intriguing association is the significant inverse correlation between the membrane-associated localization of ß-catenin and the cell cycle inhibitor p27Kip1 (P = 0.0025) found in the superficial spreading melanomas. Interestingly, transfection of p27Kip1 was reported to cause cell-cycle arrest, cell scattering, and induction of cell migration in hepatocellular carcinoma cells (32) . The mechanisms by which p27Kip1 can induce such phenotypic changes is not known, but it was hypothesized that p27Kip1 might target a non-cyclin-dependent kinase complex. ß-Catenin plays a dual role in tumor development, both as a transcriptional regulator and also as a component of the adhesion apparatus. When achieving a metastatic and invasive phenotype, tumor cells are supposed to lose adhesive properties; thus, down-regulation of membranous ß-catenin are often observed (33) . Whether ß-catenin can be down-regulated by high expression of p27Kip1 in hepatocellular carcinomas, and, thus, responsible for the induced migration, remains to be investigated. The observed inverse correlation between the staining levels of these two proteins in superficial melanoma support such a speculation.
In conclusion, we have demonstrated that cytoplasmic localization of ß-catenin was associated with favorable prognosis for patients with superficial but not nodular spreading melanomas. The mechanisms behind this rather controversial and protective role of ß-catenin in superficial melanomas remains to be elucidated, but one explanation might be that ß-catenin participates in induction of apoptosis in early lesions and that the expression is lost or down-regulated in the more advanced tumors.
| ACKNOWLEDGMENTS |
|---|
| FOOTNOTES |
|---|
1 Supported by the Norwegian Cancer Society. ![]()
2 To whom requests for reprints should be addressed, at Department of Tumor Biology, The Norwegian Radium Hospital, Montebello, 0310 Oslo, Norway. Phone: 47-22935421; Fax: 47-22522421; E-mail: g.m.malandsmo{at}labmed.uio.no ![]()
3 The abbreviations used are: APC, adenomatous polyposis coli; GSK3ß, glycogen synthase kinase 3ß; CBP, CREB-binding protein; CREB, cAMP-response element binding protein; Lef, lymphoid enhancer factor; Tcf, T-cell factor. ![]()
Received 10/ 7/02; revised 2/25/03; accepted 2/27/03.
| REFERENCES |
|---|
|
|
|---|
B activation. Nature (Lond.), 406: 86-90, 2000.[CrossRef][Medline]
This article has been cited by other articles:
![]() |
B. E. G. Rothberg, M. B. Bracken, and D. L. Rimm Tissue Biomarkers for Prognosis in Cutaneous Melanoma: A Systematic Review and Meta-analysis J Natl Cancer Inst, April 1, 2009; 101(7): 452 - 474. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. J. Chien, E. C. Moore, A. S. Lonsdorf, R. M. Kulikauskas, B. G. Rothberg, A. J. Berger, M. B. Major, S. T. Hwang, D. L. Rimm, and R. T. Moon Activated Wnt/ss-catenin signaling in melanoma is associated with decreased proliferation in patient tumors and a murine melanoma model PNAS, January 27, 2009; 106(4): 1193 - 1198. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. M. Kreizenbeck, A. J. Berger, A. Subtil, D. L. Rimm, and B. E. Gould Rothberg Prognostic Significance of Cadherin-Based Adhesion Molecules in Cutaneous Malignant Melanoma Cancer Epidemiol. Biomarkers Prev., April 1, 2008; 17(4): 949 - 958. [Abstract] [Full Text] [PDF] |
||||
![]() |
I. M. Bachmann, O. Straume, H. E. Puntervoll, M. B. Kalvenes, and L. A. Akslen Importance of P-Cadherin, {beta}-Catenin, and Wnt5a/Frizzled for Progression of Melanocytic Tumors and Prognosis in Cutaneous Melanoma Clin. Cancer Res., December 15, 2005; 11(24): 8606 - 8614. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Boccellino, G. Camussi, A. Giovane, L. Ferro, V. Calderaro, C. Balestrieri, and L. Quagliuolo Platelet-Activating Factor Regulates Cadherin-Catenin Adhesion System Expression and {beta}-Catenin Phosphorylation during Kaposi's Sarcoma Cell Motility Am. J. Pathol., May 1, 2005; 166(5): 1515 - 1522. [Abstract] [Full Text] [PDF] |
||||
![]() |
Z. Yu, P. M. Weinberger, E. Provost, B. G. Haffty, C. Sasaki, J. Joe, R.L. Camp, D.L. Rimm, and A. Psyrri {beta}-Catenin Functions Mainly as an Adhesion Molecule in Patients with Squamous Cell Cancer of the Head and Neck Clin. Cancer Res., April 1, 2005; 11(7): 2471 - 2477. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |