Fig. 4: SRC kinases are client proteins of HSP90.

Flow cytometry on BM cells from PDX models of T-ALL (a) and B-ALL (b), demonstrates that ALL (hCD45⁺) cells express a high level of HSP90 and panSRC. The anti-panSRC antibody detects murine and human panSRC family kinases, and the anti-HSP90 antibody detects murine and human HSP90. c Western blot on ALL cells recovered from PDX mice, shows a high level of expression of LCK in T-ALL, while B-ALL expresses more LYN. d Immunoprecipitation shows that LCK binds to HSP90 in PDX T-ALL cells and LYN binds to HSP90 in PDX B-ALL cells. e Treatment of PDX T-ALL cells ex vivo for 18 h with NVP-BEP800 at 1 µM affects the stability of the phosphorylated LCK as well as total LCK. The treatment inhibits the transcription factor NFAT1 that becomes phosphorylated. Data are shown as mean ± SD; n = 4 biological replicates. P-value measured by two-tailed unpaired Student’s t test; ***P < 0.001. f Western blot shows that treating PDX B-ALL cells with NVP-BEP800 for 18 h, affects the stability of phosphorylated LYN and total LYN. The downstream BCR pathway involving phosphorylation of BLK, SYK, PLCγ2, and NFϰB is also affected. g Quantification of the western blot shows that among BLK and LYN kinases, only the total amount of LYN is affected following treatment. h Quantification of the western blot shows that phosphorylation of SYK, PLCγ2, and NFϰB is affected following treatment. Data are shown as mean ± SD; n = 3 biological replicates. P-value measured by two-tailed unpaired Student’s t test; **P < 0.01; ***P < 0.001; ns, non-significant.