Comparison of Tissue Preparations to Identify and Phenotype T Cells in Human Colorectal Tumor Tissue.

Archived patient samples (e.g., formalin-fixed paraffin embedded (FFPE) tissue blocks, cryoembedded tissue blocks, and frozen whole tissue samples) are a source of immune information for which corresponding patient data is often collected. These precious resources present a unique opportunity to garner clinically relevant immunological insights of disease. We optimized a technique to immunophenotype T cells from archived patient samples through spectral flow cytometry. We demonstrate that frozen whole tissue samples were feasible to immunophenotype using surface markers analyzed on a spectral flow cytometer. Similar to previous findings acquired from freshly collected tissue in our laboratory, in frozen tissue samples there was a higher frequency of inhibitory receptors: CTLA4, PD1, LAG3, and TIM3, in colorectal cancer (CRC) tumors compared to adjacent non-tumor bowel from the same patients. Developing the technique further would allow us to better understand how T cell heterogeneity affects CRC patient survival and prognosis.