Immunohisto(cyto)chemistry: an old time classic tool driving modern oncological therapies

Abstract

In the era of precision medicine immunohistochemistry (IHC) and immunocytochemistry (ICC) share some of the highlights in personalized treatment. Survival data obtained from clinical trials shape the cut-offs and IHC scoring that serve as recommendations for patient selection both for targeted and conventional therapies. Assessment of Estrogen and Progesterone Receptors along with HER2 status has been among the first approved immunostaining assays revolutionizing breast cancer treatment. Similarly, ALK positivity predicts the efficacy of ALK inhibitors in patients with non-small cell lung cancer (NSCLC). In recent years, Programmed Death Ligand 1 (PD-L1) IHC assays have been approved as companion or complimentary diagnostic tools predicting the response to checkpoint inhibitors. Anti-PD-L1 and anti-PD-1 monoclonal antibodies have inaugurated a new period in the treatment of advanced cancers, but the path to approval of these biomarkers is filled with immunohistochemical challenges. The latter brings to the fore the significance of molecular pathology as a hub between basic and clinical research. Besides, novel markers are translated into routine practice, suggesting that we are at the beginning of a new exciting period. Unraveling the molecular mechanisms involved in cellular homeostasis unfolds biomarkers with greater specificity and sensitivity. The introduction of GL13 (SenTraGor®) for the detection of senescent cells in archival material, the implementation of key players of stress response pathways and the development of compounds detecting common mutant P53 isoforms in dictating oncological treatments are paradigms for precision oncology.