The Stilbenoid Tyrosine Kinase Inhibitor, G6, Suppresses Jak2-V617F-mediated Human Pathological Cell Growth in Vitro and in Vivo

Abstract

Using structure-based virtual screening, we previously identified a novel stilbenoid inhibitor of Jak2 tyrosine kinase named G6. Here, we hypothesized that G6 suppresses Jak2-V617F-mediated human pathological cell growth in vitro and in vivo. We found that G6 inhibited proliferation of the Jak2-V617F expressing human erythroleukemia (HEL) cell line by promoting marked cell cycle arrest and inducing apoptosis. The G6-dependent increase in apoptosis levels was concomitant with increased caspase 3/7 activity and cleavage of PARP. G6 also selectively inhibited phosphorylation of STAT5, a downstream signaling target of Jak2. Using a mouse model of Jak2-V617F-mediated hyperplasia, we found that G6 significantly decreased the percentage of blast cells in the peripheral blood, reduced splenomegaly, and corrected a pathologically low myeloid to erythroid ratio in the bone marrow by eliminating HEL cell engraftment in this tissue. In addition, drug efficacy correlated with the presence of G6 in the plasma, marrow, and spleen. Collectively, these data demonstrate that the stilbenoid compound, G6, suppresses Jak2-V617F-mediated aberrant cell growth. As such, G6 may be a potential therapeutic lead candidate against Jak2-mediated, human disease.

The Jak2 Small Molecule Inhibitor, G6, Reduces the Tumorigenic Potential of T98G Glioblastoma Cells In Vitro and In Vivo

“…Interestingly, examination of the lungs, livers, and kidneys from these same animals found no fibrosis whatsoever, suggesting that the increased fibrosis in the G6 treated mice was a tumor-specific event. Consistent with this observation that G6 does not promote host organ fibrosis is a previous work where we reported that a 30 day administration of G6 into C57BL/6 mice did not produce any histological abnormalities, such as fibrosis, within the hearts, brains, kidneys, or lungs of the treated animals [14]. However, fibrosis within host tissues and tumor tissue is quite different and it is still unclear whether increased tumor fibrosis is advantageous or deleterious to the survival of the animal [31], [32].…”

Identification of myeloproliferative neoplasm drug agents via predictive simulation modeling: assessing responsiveness with micro-environment derived cytokines

“…G6 is a preclinical Jak kinase inhibitor with a Jak selectivity profile of Jak2>Jak3>>Jak1>>>Tyk2 [20]. The STAT selectivity profile for this compound is STAT5>STAT3>STAT1, and its principal mechanism of action is induction of apoptosis [21]. Figure 3A shows the ABT737 predictive simulation results indicting a dose-dependent decrease on HEL cell viability, while Figure 3B shows the validation of these results on cultured cells.…”

“…Moreover, the Jak2-V617F mutation activates multiple anti-apoptotic proteins, including MCL1. Inhibition of Jak2 by G6 inhibits MCL1 via downstream inhibition of its transcription factors [21] and therefore contributes further to enhancing induction of apoptosis and reducing tumor cell viability. This also addresses the possible resistance mechanism that can arise when MCL1 expression increases subsequent to BCL2 inhibition [32, 33].…”

Differences in gene expression and alterations in cell cycle of acute myeloid leukemia cell lines after treatment with JAK inhibitors

“…HEL92.1.7 cell line, deriving from acute erythroid leukemia (AML M6) is homozygous for the V617F mutation, which induces constitutive JAK2 phosphorylation and drives HEL92.1.7 cell proliferation (Kirabo et al, 2011;Quentmeier et al, 2006). SET-2 cells, deriving from essential thrombocythemia with AML transformation, were confirmed to be heterozygotic for the V617F mutation (NovotnyDiermayr et al, 2012).…”