Salivary leptin as a candidate diagnostic marker in salivary gland tumors.
BACKGROUND
Since the discovery of autonomous leptin production in salivary glands, very few studies have reported on the physiological or pathological meaning of this particular cytokine in saliva. The aim of this study was to investigate the expression of leptin and its receptors Ob-Ra and Ob-Rb in parotid salivary gland tumors, with particular regard to a potential use of leptin as a tumor marker.


METHODS
Parotid tissue samples from healthy individuals (n = 31) and tumor patients (n = 97, including tissue samples from pleomorphic adenomas, adenolymphomas, basal cell adenomas, and diverse carcinomas) were analyzed by use of ApoTome-technique microscopy, immunohistochemistry, immunofluorescence, immunoblotting, and quantitative real-time PCR. Salivary and plasma leptin concentrations were measured by using ELISA. Ultrasound was used to determine tumor size before surgery.


RESULTS
In all salivary gland tumors leptin was expressed in much higher amounts than in healthy parotid tissues. The cytokine was not imported from the blood but actively produced by the tumors. Immunoblotting results indicated that leptin was present as oligomers in salivary glands. Furthermore, the examined tumors overexpressed the receptor isoforms Ob-Ra and Ob-Rb. Measured leptin concentrations in mixed saliva samples were significantly increased in patients with parotid tumors [mean (SD) 673 (484) pg/mL in pleomorphic adenomas, 679 (465) pg/mL in adenolymphomas, and 880 (618) pg/mL in carcinomas] vs controls [125 (36) pg/mL] (P < 0.001).


CONCLUSIONS
This is the first study to show that the analysis of salivary leptin in mixed saliva samples may allow preoperative differentiation between tumor patients and healthy individuals.
Schapher
Mirco
M
Department of Otorhinolaryngology, University of Erlangen-Nuremberg, Erlangen, Germany. mirco.schapher@med.stud.uni-erlangen.de
Wendler
Olaf
O
Gröschl
Michael
M
Schäfer
Renate
R
Iro
Heinrich
H
Zenk
Johannes
J
D000235:Adenolymphoma / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D008949:Adenoma, Pleomorphic / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology; D052242:Adiponectin / Q000096:biosynthesis / Q000235:genetics; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000096:biosynthesis* / Q000235:genetics; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007150:Immunohistochemistry; D020738:Leptin / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D008297:Male; D008875:Middle Aged; D010307:Parotid Neoplasms / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D054411:Receptors, Leptin / Q000096:biosynthesis / Q000235:genetics; D027544:Salvia / Q000378:metabolism*; D055815:Young Adult
C499918:ADIPOQ protein, human; D052242:Adiponectin; D014408:Biomarkers, Tumor; C515448:LEPR protein, human; D020738:Leptin; D012333:RNA, Messenger; D054411:Receptors, Leptin