The immunofluorescence staining of the subcellular distribution of RAD51 within the nucleus, endoplasmic reticulum (ER), and microtubules of A431 squamous carcinoma cells, U-2 OS osteosarcoma cells, and GBM cells showed that RAD51 is mostly expressed in nucleoli rim, which accounted for its association to the cell cycle (Figure 5E). This evidence concerns the gene RAD51 and squamous cell carcinoma.