Alterations of rb pathway components are frequent events in patients with oral epithelial dysplasia and predict clinical outcome in patients with squamous cell carcinoma.
OBJECTIVE
This study was designed to test the hypothesis that alterations in expression of G1/S modulators cyclin D1, p16 and pRb occur in patients with oral epithelial dysplasia, considered to be at increased risk for malignant transformation. In addition, the analysis of expression of all three markers in the same set of oral cancer patients would provide a unique opportunity to determine whether these alterations have cooperative or synergistic effects on oral cancer development and prognosis.


METHODS
A prospective study was undertaken to carry out immunohistochemical analysis of cyclin D1, p16 and pRb proteins in serial paraffin-embedded tissue sections of 220 oral squamous cell carcinomas (OSCCs), 90 potentially malignant lesions (52 oral hyperplastic lesions, 38 dysplasias) and 81 matched histologically normal oral tissues and correlated them with clinicopathological parameters. Ninety-eight OSCC patients were followed up for a maximum period of 94 months with overall median survival of 21 months.


RESULTS
Seventy-five of 90 (83%) potentially malignant lesions and 198 of 220 (90%) OSCCs showed altered expression of at least one of the proteins in the pRb pathway, while 10 of 90 (11%) patients with potentially malignant lesions and 40 (18%) of 220 OSCC patients showed all three alterations. Loss of p16 was the earliest event in oral tumorigenesis. In a multivariate model, loss of pRb was associated with transition from hyperplasia to dysplasia (OR = 3.727, p = 0.005). The transition of potentially malignant lesions to malignant stage was associated with pRb-/cyclin D1+ phenotype (OR = 2.294, p = 0.001) and p53+ phenotype (OR = 2.230, p = 0.002). Loss of pRb and accumulation of p53 (pRb-/p53+) phenotype was associated with histologic progression of the tumors and acquisition of invasive potential. Multivariate analysis using Cox's proportional hazards model revealed that pRb-/p53+ phenotype was the most significant adverse prognosticator for disease-free survival (hazards ratio, (HR) = 2.642, p = 0.004).


CONCLUSIONS
Deregulation of the p16/pRb/cyclin D1 pathway is an early event in acquisition of dysplasia, but deregulation of both pRb and p53 pathways is associated with malignant transformation and adverse prognosis in oral tumorigenesis.
Soni
Shilpi
S
Department of Biochemistry, Institute Rotary Cancer Hospital (IRCH), All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
Kaur
Jatinder
J
Kumar
Anupam
A
Chakravarti
Nitin
N
Mathur
Meera
M
Bahadur
Sudhir
S
Shukla
Nootan Kumar
NK
Deo
Suryanaryana V S
SV
Ralhan
Ranju
R
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D002294:Carcinoma, Squamous Cell / Q000378:metabolism* / Q000473:pathology; D016022:Case-Control Studies; D019938:Cyclin D1 / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D005260:Female; D006801:Humans; D007972:Leukoplakia, Oral / Q000378:metabolism / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009061:Mouth Mucosa / Q000378:metabolism / Q000473:pathology; D009062:Mouth Neoplasms / Q000378:metabolism* / Q000473:pathology; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011379:Prognosis; D011446:Prospective Studies; D016160:Retinoblastoma Protein / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D019938:Cyclin D1