Promoter methylation of the tumor suppressor gene Cyclin A1 could be associated with Human Papillomavirus 16 (HPV16) induced Head and Neck Squamous Cell Carcinoma (HNSCC) and Cervical Carcinoma. There is disagreement about the impact of this epigenetic event on protein expression of Cyclin A1 in malignant and non-malignant tissue and there hardly exists any information about possible relationships between Cyclin A1 expression and clinicopathological characteristics in HNSCC.
We analyzed protein expression of Cyclin A1 in 81 HNSCC and 74 benign tonsils by immunohistochemistry and correlated it to Cyclin A1 methylation status, presence of HPV16 infection and other clinicopathological characteristics.
Overexpression of Cyclin A1 was more present in HNSCC than in tonsils (p<0.001). In both entities, HNSCC and benign tonsils, expression of Cyclin A1 significantly correlated with the expression of Cyclin-dependent kinase-inhibitor p16 (p=0.000672 and 0.00495). In tonsils, expression of Cyclin A1 was inversely proportional to age (p=0.00000396), and further correlated with expression of tumor suppressor gene p53 (p=0.000228). In HNSCC Cyclin A1 expression was associated with the presence of HPV16 DNA (p=0.0014) and a lower recurrence rate in univariate and multivariate analysis (p=0.002 and 0.013). Neither in HNSCC nor in tonsils Cyclin A1 expression correlated with promoter methylation.
Cyclin A1 is an important cell cycle regulator with age-related increased expression in tonsils of children. HPV16 induces overexpression of Cyclin A1 in HNSCC despite promoter methylation. Overexpression of Cyclin A1 predicts a lower recurrence rate in HNSCC independently of HPV16.
Keywords: Head and neck squamous cell carcinoma, Cyclin A1, Promoter methylation, Human Papillomavirus 16.