Abstract: Odontogenic lesions have different and controversial behavior from same lesions in other sites of body. These controversies insist the need of further studies about the nature and behavior of these lesions. The aim of the present study was to investigate the stromal and epithelial expression of CD10 in different odontogenic lesions. In this study 80 odontogenic lesions were evaluated: 29 Unicystic Ameloblastoma (UA) (consists of 5 mural , 24 luminal and intraluminal type) , 11 solid ameloblastoma (SA) , 20 odontogenic keratocysts(OKC) and 20 dentigerous cysts were reviewed by IHC for CD10 staining. Ameloblastoma demonstrated higher number of epithelial CD10 positive cells (9.9±2.1) than UA (4.5±1.4) and dentigerous cysts (2.05±1.5). There was no significant difference in the CD10 expression between OKCs (8.7±2.2) and solid ameloblastomas but significant difference was seen between OKC and UA. Stromal expression of CD10 was seen in 90.9% of solid ameloblastoma and mean percentage of stromal CD10 expression was 14.8±5.5. Cd10 stromal expression showed a statistically significant difference between different groups except SA and OKCs. In conclusion the results of this study propose that high expression rate of CD10 might be one of the reasons for aggressive behavior of ameloblastoma and high recurrence rate of OKC and reinforce the classification of OKC as an odontogenic tumor.
INTRODUCTION
Different types of odontogenic cysts and tumors originate from remnants of dental lamina. The capacity for additional proliferation of these epithelial remnants during cyst formation is different and thus cause variations in their biological behavior and molecular expression, due to an unknown mechanism (De Vicente et al., 2010). Odontogenic lesions have different and controversial behavior from same lesions in other sites of body. Some cysts like odontogenic keratocysts have neoplastic nature and some tumors (neoplasms) such as ameloblastomas have aggressive behavior despite of benign histopathologic features. These controversies insist the need of further studies about the nature and behavior of these lesions.
CD10 is a zinc- dependent metallopeptidase which is essential for cleavage of neuropeptids and peptide hormones which splits biologically active peptides to hydrotrophic parts.
CD10 expressed on the surface of some normal and neoplastic hematopoietic, lymphoid and epithelial cells and has an significant role in the classification of B- lineage lymphomas (Murali and Delprado, 2005).
Recently, CD10 expression in tumor- associated stromal cells has been detected in some tumors such as invasive breast carcinoma, colorectal tumors, ameloblastoma, squamous cell carcinoma, malignant melanoma, nasopharyngeal carcinoma, prostate cancer and liver cancer and CD10 is thought to be involved in tumor-stromal interactions (Nishihara et al., 2009).
Deschamps et al. (2006) study, membranous expression of CD10 is correlated with poor differentiation and proliferation index in pancreatic endocrine tumors (Deschamps et al., 2006). It has a prognostic role in bladder cancer patients (Bahadir et al., 2009).
Zhang et al. (1990) in their recent study proposed that CD10 is involved in both proliferation and apoptosis when it express in cancer cells ,while its stromal expression may cause tumor progression (Shibata et al., 2004).
The aim of the present study was to investigate the stromal and epithelial expression of CD10 in different odontogenic lesions.
MATERIALS AND METHODS
Materials: In this study 80 odontogenic lesions consist of 29 unicystic ameloblastoma (UA) (5 mural type, 24 luminal and intraluminal type) , 11 solid ameloblastoma (SA) , 20 odontogenic keratocysts (OKC) and 20 dentigerous cysts were studied.
Firstly, H and E slides of available blocks were reviewed and then cases with definite diagnosis and adequate tissue were selected for Immunohistochemical Staining (IHC). Cases with severe inflammation were excluded from study.
IHC staining and analysis: IHC staining was performed by using Invasion Labeled Peroxides System (DAKO, Carpentaria, CA, USA). All the samples have been fixed in 10% buffered formalin and have been embedded in paraffin. Sections with 4μ thickness were prepared, deparaffinized in xylene, rehydrated in graded alcohol and were washed with distilled water. Antigen retrieval was performed by using DAKOcytomation target retrieral solution with PH = 9, for 20 min. Internal peroxidase activity was inhibited by 3% H2O2.
Tissue sections were then incubated for 30 minutes with the anti-CD10 antibody (Santa Cruz Biotechnology Inc., Sc-1993) at a 1/50 dilution.
Omission of primary antibody was employed as negative control, while tonsil tissue was used as positive control.
Brown membranous and cytoplasmic staining was considered as positive.
Immunohistochemical results were interpreted by two pathologists.
For each positive section ten microscopic fields which showed highest immunoreactivity in epithelial and stromal cells were identified by x40 magnification and the percentage of stained cells was calculated.
Statistical analysis: Mann-Whitney, Chi square and Kruskal Wallis tests were used to compare results. The level of significance was set at 0.05.
RESULTS
CD10 expression was seen in epithelial lining and tumor cells of all lesions examined in the present study. In all cases both cytoplasmic and membranous immunoreactivity was seen. In OKCs, nuclear staining was also seen.
In DCs, immunoreactivity was mainly seen in the superficial layers of epithelial lining.
Solid ameloblastomas demonstrated higher number of epithelial CD10 positive cells (9.9±2.1) than UAs (4.5±1.4) and DCs (2.05±1.5) (p<0.001, p<0.001, respectively). There was no significant difference in the CD10 expression between OKCs (8.7±2.2) and SAs but significant difference was seen between OKCs and UAs (Table 1). Stromal expression of CD10 was seen in 90.9% of SAs while only 5% of DCs express stromal CD10. Frequency of CD10 expression in UAs and OKCs was, respectively as 51.7 and 80% (Fig. 1-5).
Mean percentage of stromal CD10 expression was highest in SAs (14.8±5.5). Man Whitney test showed a statistically significant difference between different groups except SAs and OKCs (p = 0.86) (Table 1).
DISCUSSION
Ameloblastoma is the most common and slow growing odontogenic neoplasm which is locally aggressive and shows a high recurrence rate especially if not completely removed (Regezi, 2002; Pinheiro et al., 2004). Between odontogenic cysts, OKC shows aggressive behavior with higher rates of recurrence than other types of odontogenic cysts, as well as a tendency to invade adjacent tissue which was comparable to ameloblastoma (De Vicente et al., 2010).
| Table 1: | Epithelial and stromal expression of CD10 in different types of lesions |
| Fig. 1: | CD10 immunoreactivity in epithelial and stromal cells of plexiform ameloblastoma |
| Fig. 2: | CD10 immunoreactivity in epithelial cells of follicular ameloblastoma |
| Fig. 3: | CD10 immunoreactivity in epithelial and stromal cells of unicystic ameloblastoma |
| Fig. 4: | CD10 immunoreactivity in epithelial and stromal cells of odontogenic keratocyst. Nuclear staining of epithelial cells is also seen |
| Fig. 5: | CD10 immunoreactivity in superficial epithelial cells of dentigerous cyst |
So the term Keratocystic Odontogenic Tumor (KOT) was suggested by WHO , due to its aggressive nature (Barnes et al., 2005).
Most of investigators related the distinctive behavior of KOT to the features of its epithelial lining (Piattelli et al.,1998; Thosaporn et al.,2004; Tsuneki et al.,2008).
But, Browne (1975) who was first to propose that connective tissue wall also has a role in the pathogenesis of OKC.
CD10 antigen is a cell surface zinc- dependent metalloprotease which is expressed in different cell types. CD10 is also expressed in a variety of other lymphohematopoieitic and non- lymphohematopoietic neoplasm (Abdou, 2007).
CD10 may have a specific role in controlling of cell growth and differentiation of both hematopoietic and epithelial cell groups (Murali and Delprado, 2005) and stromal expression of CD10 is associated with malignant transformation of kerationcytes (Takahara et al., 2009).
Stromal CD10 expression has also been observed in colorectal adenomas and carcinomas and in invasive ductal carcinomas of the breast but not in normal tissues, a finding supporting the hypothesis that CD10 may facilitate invasion and matastasis. Therefore, it appears that CD10 may contribute to the neoplastic processes in different tissue types (Bahadir et al., 2009).
In a recent study Iezzi et al. (2008), suggested that stromal CD10 expression was associated with poor prognosis in oral squamous cell carcinoma.
In malignant melanoma, stromal CD10 expression was significantly higher in primary tumors with larger tumor thickness and Ki67 proliferation fraction (Kim et al., 2010).
In the present study CD10 expression in DC was seen mainly in the superficial layers of epithelial lining and only one case showed stromal immunoreactivity. This results in accordance with Masloub et al. (2011). They suggest that high CD10 expression in DC, might indicate the potential neoplastic activity of the epithelial lining of this cyst.
In our study stromal and epithelial CD10 positivity increased from DC to UA, OKC and SA. This increase in CD10 immunoreactivity might explain the variable behavior of these lesions and highly aggressive and invasive behavior of ameloblastoma and OKCs and supported the notion that OKC have a neoplastic nature. This result is similar to the results of Abdel-Aziz and Amin (2012) and Iezzi et al. (2008) who demonstrated that higher recurrence rate is seen in tumors with high stromal CD10 expression. The higher expression rate of CD10 in OKC than UA might be explained by the fact that, most of UA in our study were luminal and intraluminal which were non aggressive.
Unfortunately, how stromal CD10 positivity increases aggressiveness is remained unresolved. Interaction of CD10 positive stromal cells with cancer cells and acceleration of cell cycle and motility, is a probable theory.
Since CD10 is structurally similar to other MMPs and stromelysin, it may create a microenviroment that facilitate invasion and metastasis of the cancer cells (Kim et al., 2010).
As an additional finding, we also observed CD10 immunoreactivity in a proportion cases of OKCs. We think this observation should be further investigated in larger series.
CONCLUSION
The results of this study propose that high expression rate of CD10 might be one of the reasons for aggressive behavior of ameloblastoma and high recurrence rate of OKC and reinforce the classification of OKC as an odontogenic tumor.
We have also showed that connective tissue cells were as important as epithelial cells in the biological behavior of these lesions.
ACKNOWLEDGMENT
The authors thank the Vice-Chancellery of Shiraz University of Medical Sciences for supporting this research (Grant # 4296).