Studies of the Cell Cycle Regulatory Proteins P16, Cyclin D1 and Retinoblastoma Protein in Laryngeal Carcinoma Tissue

Defects in the system controlling the cell cycle can lead to an increased proliferation of cancer cells. The aim of this study was to analyse the immunohistochemical expression of chosen cell cycle proteins (P16, cyclin D1 and retinoblastoma protein) and their connection with the clinical course of the disease in laryngeal squamous cell cancer (LSCC). Cancer tissue sections obtained from 58 patients after total laryngectomy served to determine the level of the proteins' expression using immunohistochemical staining and commercial antibodies. A decreased level of P16 expression in 47 per cent, of retinoblastoma protein in 12 per cent and strong cyclin D1 expression in 48 per cent of cases was revealed. Our results show significant correlation between decreased P16 expression and increased tumour dedifferentiation. Overexpression of cyclin D1 was statistically more common in locally advanced tumours (T(3) -T(4)). Low expression of retinoblastoma protein was significantly correlated with both positive P16 immunostaining and with strong cyclin D1 expression. Our study confirms that dysfunction of cell cycle regulation is a common event and may play a significant role in the development of squamous cell carcinoma of the larynx.