HPV infection and the alterations of the pRB pathway in oral carcinogenesis.
Inactivation of the retinoblastoma (pRB) pathway is a common event in oral squamous cell carcinoma particularly through the aberrant expression of the components within this pathway. This study examines the alterations of molecules within the pRB pathway by looking at the presence of homozygous deletions in p16(INK4A) and the expression patterns of pRB, cyclin D1 and CDK4, as well as the presence of human papillomavirus (HPV) in our samples. In our study, 5/20 samples demonstrated deletions of p16(INK4A) exon 1alpha. pRB overexpression was found in 20/20 samples, the expression was mainly observed in all layers of the epithelia, particularly in the basal layer where cells are actively dividing and aberrant pRB expression was found in 12/20 samples. Cyclin D1 and CDK4 overexpression was detected in 6/20 and 2/20 samples respectively in comparison to hyperplasias where both proteins were either not expressed or expressed at minimal levels (<10%). Strikingly, HPV was found to be present in all of our samples, suggesting that HPV plays a significant role in driving oral carcinogenesis. Notably, 17/20 of our samples showed more than one alteration in the pRB pathway, however, we did not find any significant relationship between the presence of HPV, homozygous deletion of p16(INK4A) and overexpression of pRB, cyclin D1 and CDK4. Collectively, this data demonstrates that alterations in the pRB pathway are a common event and involve the aberration of more than one molecule within the pathway. Furthermore, the involvement of HPV in all our samples suggests that HPV infection may play an important role in oral carcinogenesis.
Lim
Kue Peng
KP
Cancer Research Initiatives Foundation, 2nd Floor Outpatient Centre, Subang Jaya Medical Centre, 47500 Subang Jaya, Selangor, Malaysia.
Hamid
Sharifah
S
Lau
Shin-Hin
SH
Teo
Soo-Hwang
SH
Cheong
Sok Ching
SC
D002294:Carcinoma, Squamous Cell / Q000209:etiology* / Q000378:metabolism / Q000821:virology; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism*; D019938:Cyclin D1 / Q000032:analysis / Q000378:metabolism; D051358:Cyclin-Dependent Kinase 4 / Q000032:analysis / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis / Q000235:genetics; D005091:Exons; D005260:Female; D017353:Gene Deletion; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D008296:Malaysia; D008297:Male; D009062:Mouth Neoplasms / Q000209:etiology* / Q000378:metabolism / Q000821:virology; D027383:Papillomaviridae / Q000302:isolation & purification; D030361:Papillomavirus Infections / Q000150:complications*; D016160:Retinoblastoma Protein / Q000032:analysis / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000032:analysis / Q000378:metabolism*
D019941:Cyclin-Dependent Kinase Inhibitor p16; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D019938:Cyclin D1; D051358:Cyclin-Dependent Kinase 4