H2AX and neoplasm: Histological staining of actin, alpha2, smooth muscle (SMA), a marker of activated fibroblast upregulated by persistent oxidative stress (Martinez‐Outschoorn et al, 2010; Toullec et al, 2010; Balliet et al, 2011; Artaud‐Macari et al, 2013) accumulated in CAF from HER2 and TN tumours compared to LumA tumours (Fig 4D and E) and was negatively correlated with H2AX protein levels (Fig 4F).