Figure 5. Human samples and methods used for the γ-H2AX assay.

While tumor sampling is the most appropriate biospecimen for γ-H2AX detection to follow cancer treatments, such biopsies are often poorly accessible, particularly for repetitive sampling. For this reason, clinicians have to rely on other sources of biospecimen that can be obtained non-invasively (blood samples, circulating tumor cells (CTCs), buccal cells, plucked hairs) or invasively (skin biopsies). It should be noted that some of these samples can be used for the detection of other histone PTMs (see Table 4). M: microscopy; MF: Microscopy (i.e. immunohistochemistry or immunocytochemistry) and FACS; Red star: human samples used for radiation biodosimetry; Blue star: human samples used for drug development.