Supervisors info:
Φώτιος Τζέρμπος, Αναπληρωτής Καθηγητής Στοματικής και Γναθοπροσωπικής
Χειρουργικής, Οδοντιατρική Σχολή, ΕΚΠΑ
Ιωάννης Ιατρού, Καθηγητής Στοματικής και Γναθοπροσωπικής Χειρουργικής,
Οδοντιατρική Σχολή, ΕΚΠΑ
Κωνσταντίνος Τόσιος, Επίκουρος Καθηγητής Στοματολογίας, Οδοντιατρική
Σχολή, ΕΚΠΑ
Summary:
Introduction: The formation of jaw cysts has unique characteristics in relation to their pathology as mechanisms of odontogenesis are associated with their formation. Odontogenic cysts are divided into two categories: a) developmental and b) inflammatory. Odontogenic
keratocysts and radicular cysts are detected clinically quite frequently.
Odontogenic keratocysts are characterized by a high rate of growth and tendency to invade in to adjacent anatomical structures. The term “keratocyst” was first introduced by Philipsen in 1956 in order to define every odontogenic cyst that shows keratinization of the epithelium.
The particular characteristics of keratocysts were then described by Shear in 1960. The World Health Organization (WHO) reclassified OKC in its 2005 edition of histological classification of odontogenic tumours and according to this reclassification, the OKC is now considered as a KCOT. It is defined as “a benign uni- or multicystic, intraosseous tumour of
odontogenic origin, with a characteristic lining of parakeratinized stratified squamous epithelium that bears the potential for aggressive, infiltrative behaviour”, a term that better reflects its neoplastic nature. Several factors form the basis of this decision: a) the clinical
behaviour of the lesion, since KCOT is locally destructive and highly recurrent, b) the histopathologic characteristics, considering that the basal layer of the KCOT budding into connective tissue, in addition to the mitotic figures that are frequently found in the suprabasal
layers, and finally c) genetic alterations (nevoid basal cell carcinoma syndrome “NBCCS” or Gorlin-Goltz), are the most important parameters.
The endoplasmic reticulum (ER) is an organelle with a major role in the synthesis of lipid and proteins and leads many cellular processes such as organogenesis, transcriptional activity, stress responses, and apoptosis. ER is responsible for the proper folding of the newly
synthesized proteins that is facilitated with the assistance of various ER chaperones. When the amount of unfolded protein exceeds the folding capacity of the ER, human cells activate a homeostatic defense mechanism designated as the UPR that follows ER stress. Among the
various consequences of UPR is also the upregulation of BiP/GRP78 and of other chaperones that is considered diagnostic for the induction of ER stress in a given tissue. Calnexin and calreticulin are ER chaperones specifically involved in the folding of glycoproteins. If the protein is folded properly, it is released from the enzyme and transported
to the Golgi apparatus. If it is not folded appropriately, UDP-glucose-glycoprotein glucosyltransferase attaches one glucose residue and returns it to calnexin and calreticulin.
Aim: Considering the neoplastic nature of KCOTs, in combination with their poorly defined aetiology we explored if ER stress is involved in disease development. Specifically, we evaluated the expression of the chaperones, BiP/GRP78 and calnexin in a panel of KCOTs as
compared to PACs and TFs. Both of these markers are considered to accurately reflect the induction of ER stress which has been associated with neoplastic development.
Materials and Methods: Paraffin-embedded tissue specimens of KCOTs, PACs and Traumatic Fibroma (TFs) were selected from the archives of the Department of Oral Pathology, of the National and Kapodistrian University of Athens, Dental School spanning the years 2006 - 2011 and were analyzed by immunohistochemistry. The selection of the
tissue specimens was based on the sufficiency of clinical characteristics, the relevance of the histopathologic characteristics and the abundance of tissue specimen for immunochemistry. The tissue specimens were obtained from patients that attended the Department of Oral
Pathology, of the National and Kapodistrian University of Athens, Dental School, and had given full informed consent. Immunohistochemistry was carried out in formalin fixed, paraffin embedded tissue
specimens. The antibodies used were monoclonal rabbit anti-BiP (C50B12), by Cell Signaling Technology; 1:100 and monoclonal mouse anti-calnexin (sc-46669), by Santa Cruiz Biotechnology, Santa Cruz, CA, USA; 1:75. Immunostaining was performed by using the
Superpicture Polymer (Dab) Kit (Novocastra), following the manufacturer’s instructions.
Before evaluation, a weak counterstaining with hematoxylin was performed in all immunostained specimens. Before evaluation, a weak counterstaining with hematoxylin was performed in all immunostained specimens. The samples were examined for the potential expression of BiP/GRP78 and calnexin.
Results: Analysis revealed a strong association between both BiP/GRP78 and calnexin expression and KCOTs: 18 out of 24 (75%) KCOTs expressed BiP/GRP78 as opposed to 1 out of 9 (13%) PACs and none of 5 TFs evaluated (P < 0.001, x2-test). Calnexin was expressed in 11 out of 24 KCOTs (46%) but only one out of 9 (13%) PACs and none of the 5
TFs analysed (P < 0.001, x2-test).
Conclusions: Study results entail that induction of endoplasmic reticulum stress maybe of diagnostic value in keratocystic odontogenic tumours characterisation. Additionally, recent findings suggesting that endoplasmic reticulum stress plays a causative role in keratinisation
of epithelia. Therefore, pharmacological interference with the execution of the unfolded protein response should be considered for the management of keratocystic odontogenic tumours.
