# Advanced Omics and Radiobiological Tissue Archives: The Future in the Past
## 4 Omics Analysis on FFPE Samples in Radiobiological Archives
### Proteomics
Comparing the proteomics data of their study to only a few available published data on frozen PC tissue confirmed identification of similar proteins including a high abundance cytoplasmic, cytoskeletal and nuclear histones. The analysis of FFPE proteomics data and further immunoblotting suggested that an alteration in the ANXA2 expression served as a predictive marker for the metastatic potential of prostate cancer [90]. To identify a predictive marker of chemotherapy and/or radiotherapy resistance in patients with oral squamous cell carcinoma (OSCC), [PERSON] et al. compared the proteome of FFPE samples obtained from patients who received preoperative chemotherapy and/or radiotherapy followed by surgery, using nano-flow high-performance liquid chromatography [91]. The FFPE samples of this study were provided from the different groups of resistant and sensitive patients treated daily by fractional radiation exposure. The proteome profiling and immunohistochemistry validation suggested galectin-7 as a predictive marker of tumour resistance in OSCC patients [91]. [PERSON] et al. used label-free proteomics to analyse the FFPE samples of nasopharyngeal carcinoma (NPC) patients who were treated by intensity-modulated radiotherapy (IMRT). The analysis identified that Epstein-Barr (EBV) and Herpes simplex (HSV) viruses-related proteins markedly present in early-stage of cancer [92]. The authors suggested that identified proteome signatures in their study is well-related to head and neck cancer onset and can serve as potential targets for therapy but need further validation [92]. In contrast to archival tumour samples, the normal FFPE tissue in radiobiological biobanks was not often analysed using proteomic approaches. To investigate the effect of total body irradiation on the heart, [PERSON] et al. used a label-free quantitative approach to compare the FFPE heart tissues of sham- and total body irradiated C57 BL/6 mice as a model system. The mice hearts were isolated and fixed in formalin 24 h after the irradiation and proteins were extracted and separated using an optimised protocol [47]. In good agreement with data observed from proteome analysis of fresh-frozen hearts [12], the study showed immediate alterations in cardiac metabolic enzymes and mitochondrial proteins [12]. The same group used recently sequential urea/SDS extraction and filter-aided sample preparation (FASP) digestion to analyse the late effects of chronic radiation exposure in human FFPE heart autopsies from Mayak workers by label-free proteomics. Here authors compared for the first time the proteome profiles of the fresh frozen and FFPE heart tissues after chronic irradiation [14]. The proteome profile of the FFPE samples confirmed the observations obtained from fresh-frozen cardiac tissue [93]. Although the experimental design, sample size, analytical approaches make a direct comparison of the two studies difficult, the main results of both studies were similar, indicating the changes in main functional clusters of proteins involved in the heart metabolism and structure following irradiation [14].