P16 AND TOP2A IMMUNOHISTOCHEMICAL EXPRESSION FOR DETECTION OF CERVICAL INTRAEPITHELIAL AND EARLY MALIGNANT LESIONS

Abstract

Cervical Cancer (CC) is the fourth most common type of cancer worldwide. In vast majority of cases, it is caused by Human Papillomavirus (HPV) - a Sexually Transmitted Disease (STD). In Pakistan, the incidence of cervical cancer is 4.9% while its morbidity and mortality rates are considerably higher due to ignorance in terms of screening, prevention and vaccination. As a result more than 70% women with CC are diagnosed at very advanced stage of malignancy. In this time of vaccines, systematic screening for CC may be considered as one of the most valuable tools for reducing the disease burden and death rates. Despite the characteristic advantages of Liquid Based Cytology (LBC) in cervical screening, LBC has low sensitivity (40-50%) which usually leads to under diagnosis. While HPV testing in cervical screening has been proven effective to some extent but its low specificity may result in unnecessary treatment and high-risk HPV testing alone cannot differentiate between transient and persistent infections. Hence, applying different markers in CC screening is necessary for its control, early-diagnosis and prevention. P16 is a cyclin-dependant kinase inhibitor and plays a crucial role as a cell cycle regulator by decelerating cell progression from G1 to S phase. While Topoisomerase IIA is an enzyme responsible for DNA strands uncoupling during its replication and expressed only in cycling cells. The primary objective of this study was to assess immunohistochemical expression of P16 and TOP2A in normal, pre cancerous and cancerous cervical cytology cell blocks and to correlate their expression level with cytological and various clinicopathological parameters. It was a cross-sectional study conducted at PNS Shifa Hospital Karachi and Dr. Ruth K. M. Pfau, Civil Hospital, Karachi over a time period of eight months. A total of 60 cervical cytology samples were analyzed for immunohistochemical staining using CDKN2A/P16-INK4a Mouse (IgG) and Topoisomerase II alpha Rabbit (IgG) Monoclonal antibodies. Demographic data and various clinicopathological parameters were recorded using the designed Performa and the results of immunostaining were analyzed and correlated with the documented parameters. The results revealed that there is a significant association of P16 immunohistochemical expression with age group, ethnicity, menopausal status, cytological diagnosis, and cancer status. While TOP2A was only associated with menopausal status, cytological diagnosis, and cancer status of the patients. P16 ix immunostaining was directly related with the increasing severity of cervical cytological abnormalities. The sensitivity and specificity of P16 for detecting pre-cancerous and cancerous lesion was significantly higher, whereas TOP2A demonstrated higher specificity for detecting cancerous lesions. Therefore, P16 can be a reliable immunohistochemical marker for diagnosing early as well as late cancerous lesion while TOP2A is highly specific marker for ruling out non-cancerous lesion