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P. Giannoni et al.
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Figure 7. Fully differentiated osteoclasts, as well as osteoclast precursors, support CLL-cell survival. A limited number of CLL cells further upregulate Ki-67 and reactivate cycling after osteoclast co-culture. (A) Apoptosis of CLL cells was prevented by co-culturing leukemic cells with fully mature osteoclasts for 24 h to 7 days (8 CLL cases at each time-point). (B) Apoptosis of CLL cells was also prevented after their co-culture with osteoclasts derived from healthy monocytes stimulated with MCSF+RANKL, with MCSF+RANKL+CLL-cm or with MCSF+CLL-cm only (putative osteoclast precursors). The percentage of apoptosis was evaluated by DiOC6 staining after 7 days of co-culture. (C) Bright field images show the viability of CLL cells co-cultured with fully differentiated osteoclasts derived in the presence of RANKL (with or without added CLL-cm) or with osteoclast precursors derived in the presence of MCSF+CLL-cm only. (D) Ki-67 was upregulated on CLL cells after their co-culture with mature osteoclasts (4 CLL cases examined). (E) Ki-67 appeared brightly expressed on a limited number of cells. Ki-67+ leukemic cells progres- sively increased from 72 h to 7 days (1%-15%). (F) A small population of CLL cells was stimulated to enter into S and G2M phases after their co-culture with osteo- clasts. CLL cells were stimulated with CpG as controls (4 cases analyzed), AVG: average.
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haematologica | 2021; 106(10)