Figure 2. Blocking α4β1 and αLβ2 integrins in CLL-stromal cell co-cultures sensitizes CLL cells to ATO and fludarabine.

2 × 10⁵ CLL cells, with or without previous incubation for 1 h with the indicated antibodies, were co-cultured with HS-5 (A) or HS-27A (B) stromal cells. After 2 h at 37°C, 2 μM ATO was added and viability was determined after 48 h by flow cytometry. (C) HS-5, HS-27A, and primary BMSC cells were treated or not with TNFα for 16–20 h and VCAM-1 and ICAM-1 expression analyzed by Western blotting. (D) HS-5 and HS-27A stromal cells were incubated for 48 h with the indicated antibodies, in the absence or presence of 2 μM ATO. Cell viability was determined as above. (E–F) CLL cells were treated as in (A, B) with the indicated antibodies and added to HS-27A cells. After 2 h at 37°C, 5 μM fludarabine was added and viability determined after 48 h. *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001.