Deregulated expression of p16INK4a and p53 pathway members in benign and malignant myoepithelial tumours of the salivary glands.
OBJECTIVE
Myoepithelial salivary gland tumours are uncommon and follow an unpredictable biological course. The aim was to examine their molecular background to acquire a better understanding of their clinical behaviour.


RESULTS
Expression of protein (E2F1, p16(INK4a), p53, cyclin D1, Ki67 and Polycomb group proteins BMI-1, MEL-18 and EZH2) was investigated in 49 benign and 30 primary malignant myoepithelial tumours and five histologically benign recurrences by immunohistochemistry and the findings correlated with histopathological characteristics. Benign tumours showed a higher percentage of cells with expression of p16(INK4a) pathway members [p16(INK4a) and E2F1 (both P < 0.001), and cyclin D1, P = 0.002] compared with normal salivary gland. Furthermore, malignant tumours expressed p53 (P = 0.003) and EZH2 (P = 0.09) in a higher percentage. Recurrences displayed more p53 + tumour cells (P = 0.02) than benign primaries. Amongst the benign tumours, the clear cell type had the highest proliferation fraction (P = 0.05) and a higher percentage of EZH2 was detected in the plasmacytoid cell type (P = 0.002).


CONCLUSIONS
This study is the first to demonstrate that deregulation of the p16(INK4a) senescence pathway is involved in the development of myoepithelial tumours. We propose that additional inactivation of p53 in malignant primaries and benign recurrences contributes to myoepithelial neoplastic transformation and aggressive tumour growth.
Vékony
H
H
Department of Oral and Maxillofacial Surgery/Oral Pathology, Academic Centre for Dentistry, VU University Medical Center, Amsterdam, The Netherlands.
Röser
K
K
Löning
T
T
Raaphorst
F M
FM
Leemans
C R
CR
Van der Waal
I
I
Bloemena
E
E
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D009208:Myoepithelioma / Q000378:metabolism* / Q000473:pathology; D012468:Salivary Gland Neoplasms / Q000378:metabolism* / Q000473:pathology; D012469:Salivary Glands / Q000473:pathology; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D055815:Young Adult
D019941:Cyclin-Dependent Kinase Inhibitor p16; D016159:Tumor Suppressor Protein p53