Figure 3

Ablative γ-irradiation induces the release of low molecular weight, apyrase-sensitive factors, which stimulate THP-1 cell migration. (A) THP-1 cell transwell migration. Breast cancer cells were left untreated or γ-irradiated as in Figure 2. Cell-free supernatants were collected 1–4 days after irradiation and applied to transwell migration assays with THP-1 cells. Means ± s.d. of quadruplicates are given. Asterisks indicate p < 0.05 as determined by unpaired Student’s t-test analysis (20 Gy vs. daily 2 Gy). (B) The transmigration stimulating factors are of low molecular weight and sensitive to apyrase treatment. Supernatants of HCC1937 cells irradiated at 20 Gy were collected on day 4 after irradiation and subjected to ultrafiltration with Vivaspin 2 columns (Molecular weight cut-off 10 kDa) or apyrase treatment (33.3 milliunits active or heat-inactivated apyrase/ml, 30 min at 37°C). Culture medium supplemented with ATP (200 nM) or SDF-1α (200 ng/ml) was treated in parallel. Afterwards, transwell migration assays with THP-1 cells were performed and the percentage of transmigrated cells was normalized on the corresponding untreated control. Means ± s.d. of quadruplicates are shown.