The impact of delay to fixation on PD-L1 expression in human tissue
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The effects of tissue preservation techniques are known to have meaningful impact on diagnostic and prognostic variables. This study aims to evaluate and improve the quality of biospecimens utilized in cancer research. Protein Death Ligand 1 (PD-L1) is a cell surface molecule with an important role for immune suppression. Its utility lies within providing a basis for limiting the immune response. We aimed to evaluate the expression levels of PD-L1 in tissues that had varying lengths of delay to fixation. 21 placenta, renal, and colon surgical specimens were collected and divided into delay to fixation cohorts. Samples were then evaluated through Hematoxylin and Eosin (H and E), PD-L1 Immunohistochemistry (IHC), and for the colon samples Microsatellite Instability (MSI) Status. A total of 75% of slides were positive for PD-L1 expression. In relation to Placenta all were positive for PD-L1 expression. While colon samples were 41.25% positive for PD-L1 expression. Finally 49.5% of renal samples were positive for PD-L1 expression. Of the three colon samples one was MSI Low status while the remaining were Microsatellite Stable (MSS). PD-L1’s status as a utile biomarker for prognostic and diagnostic reasons remains uncertain. The stability of PD-L1 expression across tissue type and sample delay shows the stability of the biomarker. Therefore our work shows that a delay while significant in affecting other biomarkers does not significantly alter PD-L1 expression.