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Molecular Oncology, Markers, Clinical Correlates |
1 Departments of Pathology and 2 Surgery, Rhode Island Hospital and Brown University School of Medicine, Providence, Rhode Island, and 3 Department of Pathology, Carmel Medical Center, Haifa, Israel
| ABSTRACT |
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Experimental Design: In this study, we retrospectively analyzed, resected, and otherwise untreated paraffin-embedded specimens from 134 consecutive patients with Tumor-Node-Metastasis stage II colonic carcinomas for EGFR, c-MET, ß-catenin, and p53 protein expression by immunohistochemistry.
Results: Thirty-five percent, 77, and 65% of tumors exhibited strong (+2 and +3 immunopositivity) expression of EGFR, c-MET, and ß-catenin, respectively. Fifty-four percent exhibited nuclear staining for p53 in >10% of the tumor cells. Univariate analysis revealed that increased nuclear p53 expression (P = 0.001), strong membranous EGFR expression (P = 0.04), and lymphovascular invasion (P = 0.01) were significantly related to disease recurrence and that p53 (P = 0.02) and EGFR (P = 0.05) expression were associated with decreased survival. Increased nuclear p53 expression also correlated with the presence of distal metastasis (P = 0.027). No significant association was seen between c-MET expression and prognosis, whereas a strong trend was detected between loss of ß-catenin (P = 0.065) expression and poor outcome. Multivariate analysis indicated that p53 (P = 0.04), EGFR (P = 0.05), and lymphovascular invasion (P = 0.03) were independent predictors of recurrence and that p53 (P = 0.02) and EGFR (P = 0.01) expression were both associated with poor survival.
Conclusions: This retrospective tumor microarray study, restricted to Tumor-Node-Metastasis stage II colon cancer patients who did not undergo adjuvant therapy, supports the use of EGFR and p53 as biological markers, which may assist in predicting disease recurrence and survival.
| INTRODUCTION |
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A significant amount of research in the past several years suggests that a number of prognostic molecular markers might be useful in defining individual colonic cancer patients risk after surgery and determining which patients might benefit most from adjuvant chemotherapy (2, 3, 4) . Although many particular markers have been studied extensively, data for most markers remains inconclusive. In this study, we have chosen to examine the expression of several putative biological markers [epidermal growth factor receptor (EGFR), c-MET, ß-catenin, and p53] that are strongly suspected to play a significant role in colonic tumor proliferation and invasion using tissue microarray (TMA) technology. TMAs are especially suitable for the immunohistochemical examination of multiple markers (5) . The simultaneous evaluation of multiple cases on each slide virtually eliminates slide-to-slide variation, which is an important factor contributing to variability in immunohistochemical studies.
The EGFR, a Mr 170,000 transmembrane glycoprotein encoded by the c-erbB-1 proto-oncogene, was the first member of the tyrosine kinase receptor family to be identified (6) . On binding of ligand, EGFR dimerization occurs, and the cytoplasmic catalytic function of tyrosine kinase is activated, which in turn promotes autophosphorylation (7) . Activation of EGFR is the critical initiating event that results in the stimulation of an intracellular signal transduction cascade, which regulates cell adhesion, proliferation, differentiation, apoptosis, and metastasis (8) . Overexpression of EGFR has been found to correlate with poor prognosis in several cancers, including colorectal cancers (9) .
The c-MET proto-oncogene, which encodes a protein for hepatocyte growth factor receptor, is another tyrosine kinase associated with cancer progression (10) . It also contains a tyrosine kinase domain that activates signaling pathways involved in cell proliferation, motility, adhesion, and invasion (10) . Overexpression of c-MET has been correlated with poor prognosis in cancers such as breast, stomach, liver, endometrium, and nasopharynx (11, 12, 13, 14, 15) . More recently, the c-MET expression level in primary colon cancer has been shown to be an important predictive marker for early-stage invasion and regional disease metastasis (16) .
Deregulation of ß-catenin levels occurring through mutation of the adenomatous polyposis gene is an important mechanism for colorectal tumorigenesis (17, 18, 19) . ß-Catenin activity is controlled by a large number of binding partners that affect its stability and localization and is, thereby, able to participate in processes such as gene expression and cell adhesion (20) . Variations in the level and pattern of ß-catenin expression have been shown to correlate with outcome in colorectal cancer (21, 22, 23, 24, 25) .
p53 is a well-characterized tumor suppressor gene encoding a protein involved in cell cycle regulation, DNA replication, and apoptosis (26) . The p53 mutational and expression status of stage II colonic cancers has been studied extensively; however, no definitive conclusion has been reached as to its prognostic or predictive use (2, 3) .
We hypothesized that overexpression of one or more of the aforementioned molecular markers may prove to be a useful prognostic indicator in stage II colon cancer.
| MATERIALS AND METHODS |
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Tissue samples were formalin fixed and paraffin embedded. All corresponding H&E slides were reviewed for confirmation of diagnosis and adequacy of material by M. Resnick. Each case was classified by the pathologist (M. Resnick) according to grade (high or low), mucinous differentiation (>50% of the tumor cells), and presence or absence of lymphovascular invasion.
TMA Construction.
Paraffin blocks containing areas consisting of pure invasive carcinoma were identified on corresponding H&E-stained sections. Areas of interest that represented the invasive front of the tumor, rich in nonnecrotic tumoral glands, were identified and marked on the source block. The source block was cored and a 1-mm core transferred to the recipient master block using the Beecher Tissue Microarrayer (Beecher Instruments, Silver Spring, MD). Three to six cores were arrayed/specimen. Representative sections of normal colon were taken from
30% of the cases.
Immunohistochemistry (IHC).
IHC for each antigen (EGFR, c-MET, ß-catenin, and p53) was performed on 5-µm paraffin sections of each colon cancer TMA section described above. Slides were stained for ß-catenin (polyclonal rabbit 1:200; Cell Signaling Technology, Beverly, MA), c-MET (polyclonal rabbit 1:250; Zymed Laboratories, South San Francisco, CA), and p53 (monoclonal mouse clone DO-7, 1:5000; Dako, Copenhagen, Denmark) using the Ventana Discovery automated staining system with the DAB Map kit (Ventana, Tucson, AZ). Slides were stained for EGFR with the Dako pharmDx kit (Dako) as per manufacturers instructions. All slides were counterstained with hematoxylin, dehydrated, cleared, and mounted. Negative controls included replacement of the primary antibody with nonreacting antibodies of the same species. A multitumor array consisting of a wide array of solid tumors was used as a positive control for all antibodies.
IHC Assessment.
EGFR- and ß-catenin-positive cells stained primarily at the cell membrane and occasionally in the cytoplasm, whereas c-MET-staining cells exhibited a combined membranous and cytoplasmic pattern. For EGFR and ß-catenin, staining intensity was classified as the following: negative 0; +1 if the circumferential membrane pattern was incomplete; +2 circumferential staining with a weak or intermediate intensity; and +3 complete strong circumferential staining. c-MET staining was scored as negative 0, weak +1, moderate +2, or strong +3. For p53, arrays were scored as negative if <10% of nuclei were stained and positive if >10% of nuclei were stained. Similar criteria were used for determining nuclear positivity for ß-catenin. The extent of staining (percentage of cells staining) was, for the most part, homogeneous within each 1-mm core and, therefore, was not included as a variable.
At least three cores were scored/case. The analysis of three cores/case has been shown to be comparable with the analysis of the whole section in a recent study (28) and in a pilot validation study in our lab (unpublished results). The vast majority of cases exhibited a uniform degree of staining between all cores, and in those that did not, an average score was determined. All sections were scored independently by J. Routhier and M. Resnick without knowledge of the clinicopathological features or clinical outcome. There was a high level of correlation between the two scorers, and in the few discrepant cases, a consensus was reached after joint review.
Statistical Analysis.
Associations between categorical groups were evaluated using the
2 or the Fishers exact test when appropriate. The influence of prognostic factors on tumor-related recurrence as well as survival was assessed by Kaplan-Meier estimates, and subgroups were compared by the log-rank test for univariate analysis. The multivariate Coxs proportional hazard model was applied using a stepwise forward method to detect independent predictors of recurrence/survival. Two-tailed Ps of
0.05 were considered to be statistically significant.
| RESULTS |
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The vital status of the patients and incidence of recurrent disease is also described in Table 1
. Twenty-four patients had recurrent disease (8 local and 16 distal metastases). Ninety-two patients died during the follow-up period, 22 died of colon cancer, and 56 of unrelated causes, whereas the cause of death for 14 patients was unclear.
Frequency of Expression of EGFR, c-MET, ß-catenin, and p53 in Colonic Tumors.
Normal colonic epithelium showed weak membranous staining with EGFR and ß-catenin and a negative to weak staining pattern for c-MET. No p53 staining was observed in normal colonic mucosa.
The frequency of expression of the biological markers evaluated is described in Table 2
. Fig. 1
AD illustrates examples of TMA immunostains for these markers. When stratifying the frequency of expression into two groupslow (0 and +1 immunopositivity) and high (+2 and +3 immunopositivity)35, 77, and 65% of the tumors exhibited high expression levels of EGFR, c-MET, and ß-catenin, respectively. Fifty-four percent exhibited nuclear staining for p53 in >10% of the tumor cells, and 21% of the tumors exhibited >10% nuclear positivity for ß-catenin.
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| DISCUSSION |
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In this study, increased EGFR expression was found to be a significant uni- and multivariate indicator of disease recurrence and patient survival, although it was not significantly associated with the presence of distal metastasis. EGFR has been shown to be a strong prognostic indicator in certain cancer types (9) ; however, its role as an independent prognostic marker in colonic cancer has not been clearly defined yet. In certain studies, increased EGFR expression in colon cancer was associated with tumor stage, metastatic potential, relapse-free, and overall survival (29, 30, 31, 32, 33) , although other studies have shown no such correlation (34, 35, 36, 37, 38) . This study made use of an important conclusion reached by Goldstein et al. (39) in a recent study, which proposed a standardized scoring system for EGFR in colon cancer. Care was taken to include tissue cores only from the invasive front of the tumor, which appeared to show the highest percentage of strongly staining EGFR-positive cells (39) . In Goldsteins study, analysis of this area showed that strong EGFR staining correlated with length of survival. Determination of EGFR status may also have implications for therapeutic interventions because EGFR is currently the focus of many anticancer agents under investigation some with promising results (40) , although the correlation between EGFR expression and response to therapy remains unclear (41) .
Overexpression of c-MET has been shown to be associated with poor prognosis in a number of solid tumors (11, 12, 13, 14, 15) . More recently, c-MET expression levels as determined by reverse transcription-PCR and IHC were found to correlate directly with colon cancer stage (16) ; however, correlation of c-MET expression with recurrent disease or patient survival in colon cancer has not been reported. In this study, moderate to strong c-MET expression was present in 77% of the tumors studied; however, no correlation was found with disease recurrence or patient survival. This study, as well as the others described above, provides additional evidence for the importance of c-MET expression in the early stages of carcinoma progression and suggests that c-MET may be a viable target for preventative treatment of early-stage disease.
In many, but not all, studies, the pattern of ß-catenin expression in colorectal cancer has been shown to correlate with disease stage and prognosis (21, 22, 23, 24) . Loss of membranous and increased nuclear ß-catenin expression has been associated with short survival in colorectal tumors (22) . In this study, a strong trend was detected between loss of membranous ß-catenin expression and patient prognosis, and a weaker correlation was found between loss of membranous ß-catenin expression and the presence of distal metastasis. In contrast to the study by Hugh et al. (22) , no association was found between loss of membranous ß-catenin expression and increased nuclear expression or between increased nuclear staining and patient outcome. Finally, in this study, high-grade tumors exhibited decreased membranous ß-catenin expression. A similar trend was also described by Hugh et al. (22) .
One of the most extensively studied molecular prognostic markers for stage II colonic cancers is p53. As summarized in recent review articles, the prognostic use of a tumors p53 status is still somewhat controversial (2, 3, 4) . Indeed, conflicting results were obtained in the two largest recent studies that included 291 and 293 patients, respectively, and explored the role of p53 in stage II colon cancers (1 , 42) . This may be related in part to the different technical approach used for p53 analysis because Soong et al. (42) performed a mutational analysis, whereas Allegra et al. (1) used IHC to detect abnormal nuclear accumulation. In our study, p53 was a strong uni- and multivariate predictor of disease recurrence, distal metastasis, and patient survival. Albeit, the cohort we studied was somewhat smaller than the groups studied by Allegra et al. (1) and Soong et al. (42) , our cohort was more homogeneous in that none of the patients received perioperative chemo- or radiotherapy, and no rectal carcinomas were included.
In conclusion, in this cohort of untreated stage II colon cancer patients, immunohistochemical staining on a TMA revealed that expression of EGFR and p53 are both prognostic indicators of disease recurrence and survival. Additional larger studies will be needed to determine whether EGFR and p53 expression also predict response to adjuvant chemotherapy or targeted anti-EGFR therapy.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Requests for reprints: Murray B. Resnick, Department of Pathology, Rhode Island Hospital, 593 Eddy Street, Providence, RI 02903. Phone: (401) 444-4380; Fax: (401) 444-8514; E-mail: mresnick{at}lifespan.org
Received 10/24/03; revised 1/ 7/04; accepted 1/20/04.
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, epidermal growth factor receptor, p53 and Ki67 in colorectal liver metastasis and corresponding primary tumors. Hepatology, 284: 971-9, 1998.[CrossRef]
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