Association of IHC p16INK4a expression and ELISA Plasma p16INK4a Protein in Squamous Cell Carcinoma of Uterine Cervix: A Concept of Liquid Biopsy
Professor and Head, Department of Pathology, Sri Devaraj Urs Medical College, Sri Devaraj Urs Academy of Higher Education and Research, Tamaka, Kolar, Karnataka, India.
Introduction: Cervical cancer is the 3rd most common cancer among women worldwide. p16 biomarker is the surrogate marker in cervical cancer and can be detected by Immunohistochemistry (IHC).
Aim: To evaluate the association of IHC p16INK4a expression in tissue sections and Enzyme-linked Immunosorbent Assay (ELISA) p16INK4a protein in plasma of paired samples in Squamous Cell Carcinoma (SCC) of uterine cervix.
Materials and Methods: This laboratory-based observational, pilot study was conducted at tertiary care centre of Sri Devaraj Urs Medical College in South India from June 2020 to May 2021. Total 17 new cases of SCC of cervix diagnosed by histopathology were considered for the study. The cases were staged as per International Federation of Gynaecology and Obstetrics (FIGO) staging system and classified by histopathology as keratinising and non keratinising types. IHC p16INK4a evaluation was done on tissue sections and classified as block positivity, ambiguity and negative. ELISA p16INK4a estimation was done using plasma from Dipotassium Ethylenediaminetetraacetic Acid (K2-EDTA) blood sample of same cases. Statistical analysis was done using Statistical Package for the Social Sciences (SPSS) version 22.0 software.
Results: The age ranged from 30-80 years with mean of 54.3±12.0 years. Plasma ELISA p16INK4a level ranged from 3.4-19.6 ng/mL with a mean of 7.2±2.35 ng/mL in SCC of cervix. The plasma p16INK4a ELISA levels of 5.1 to 6.2 ng/mL, 6.0 to 6.6 ng/mL and 5.5 to 9.7 ng/mL predicts negative, ambiguity and block positivity of IHC p16INK4a expression respectively in corresponding tissue biopsy. Plasma ELISA p16INK4a levels were maximum in Non Keratinising Squamous Cell Carcinoma (NKSCC) followed by Well Differentiated Squamous Cell Carcinoma (WDSCC), Moderately Differentiated Squamous Cell Carcinoma (MDSCC) and Poorly Differentiated Squamous Cell Carcinoma (PDSCC).
Conclusion: The plasma ELISA p16INK4a levels and IHC p16INK4a expression were maximum in higher disease stage compared to lower stage. This was a pilot study to evaluate the association between tissue IHC p16 expression and plasma ELISA p16 levels. Further study has to be done on larger study population with standardised procedure to prove the hypothesis.