A pilot study using immunohistochemistry (IHC) on 32 archival formalin-fixed, paraffin-embedded (FFPE) tumor samples (from colon, lung, breast, and stomach cancers) analyzed the expression patterns of five proteins: Ki-67, Cyclin E, POLD3, γH2AX, and FANCD2, concluding that markers widely used in cell line studies require very careful evaluation before being utilized as useful biomarkers in clinical biopsy samples [154]. This evidence concerns the gene CCNE1 and neoplasm.