Finally, compound 12k and 12l were identified as the promising inhibitors of JAK2, which exhibited high inhibitory activity (IC<sub>50</sub> = 6 nM and 3 nM, respectively) and selectivity for JAK2 over JAK1 and JAK3, and showed potent antiproliferative activities toward HEL human erythroleukemia cells.
These results suggest that ZT55 is a highly-selective JAK2 inhibitor that can induce apoptosis of human erythroleukemia cells by inhibiting the JAK2-STAT signaling.
The multi-site docking protein Gab1 is constitutively phosphorylated independent from its recruitment to the plasma membrane in Jak2-V617F-positive cells and mediates proliferation of human erythroleukaemia cells.
The leukemic CD71<sup>+</sup> cells were more sensitive to INCB18424, a potent JAK inhibitor, than KSL cells. p53 restoration could ameliorate Jak2V617F-transduced p53-null erythroleukemia.
Specifically, five derivative compounds of G6 having structural similarity to the original lead compound were obtained and analyzed for their ability to (i) inhibit Jak2-V617F-mediated cell growth, (ii) inhibit the levels of phospho-Jak2, phospho-STAT3, and phospho-STAT5; (iii) induce apoptosis in human erythroleukemia cells; and (iv) suppress pathologic cell growth of Jak2-V617F-expressing human bone marrow cells ex vivo.
We investigated the activity of (E)-3(6-bromopyridin-2-yl)-2-cyano-N-(S0-1phenylethyl)acrylamide (WP1066), a novel analogue of the JAK2 inhibitor AG490, in JAK2V617F-positive erythroleukemia HEL cells and in blood cells from patients with polycythemia vera.
Using this assay and serial dilutions of an erythroleukemia cell line harboring the homozygous JAK2V617F mutation, we successfully detected the mutation within a background of wild type sequences at a sensitivity of 2.5%.
We hypothesized that the JAK2V617F mutation might also be present in samples from patients with acute myeloid leukemia (AML), especially erythroleukemia (AML-M6) or megakaryoblastic leukemia (AML-M7), where it might mimic erythropoietin or thrombopoietin signaling.