Loss of LKB1 is associated with increased metastasis and poor prognosis in lung cancer, but the development of targeted agents is in its infancy. Here we report that a glutaminolytic enzyme, ...glutamate dehydrogenase 1 (GDH1), upregulated upon detachment via pleomorphic adenoma gene 1 (PLAG1), provides anti-anoikis and pro-metastatic signals in LKB1-deficient lung cancer. Mechanistically, the GDH1 product α-KG activates CamKK2 by enhancing its substrate AMPK binding, which contributes to energy production that confers anoikis resistance. The effect of GDH1 on AMPK is evident in LKB1-deficient lung cancer, where AMPK activation predominantly depends on CamKK2. Targeting GDH1 with R162 attenuated tumor metastasis in patient-derived xenograft model and correlation studies in lung cancer patients further validated the clinical relevance of our finding. Our study provides insight into the molecular mechanism by which GDH1-mediated metabolic reprogramming of glutaminolysis mediates lung cancer metastasis and offers a therapeutic strategy for patients with LKB1-deficient lung cancer.
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•GDH1 contributes to anoikis resistance and tumor metastasis by activating CamKK2•α-KG binds to CamKK2 and recruits AMPK to CamKK2•In LKB1 null lung cancer, GDH1-induced CamKK2 substitutes for LKB1 to activate AMPK•PLAG1 induces GDH1 expression upon cell detachment from the matrix
Although elevated glutaminolysis has been demonstrated in cancer cells, the precise mechanism by which glutaminolysis promotes tumor metastasis remains unclear. In this article, Jin et al. demonstrate a mechanism by which GDH1 provides anti-anoikis and pro-metastatic signals through activating CamKK2 and AMPK that promotes tumor metastasis in LKB1-deficient lung cancer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Germline activating mutations of the protein tyrosine phosphatase SHP2 (encoded by PTPN11), a positive regulator of the RAS signalling pathway, are found in 50% of patients with Noonan syndrome. ...These patients have an increased risk of developing leukaemia, especially juvenile myelomonocytic leukaemia (JMML), a childhood myeloproliferative neoplasm (MPN). Previous studies have demonstrated that mutations in Ptpn11 induce a JMML-like MPN through cell-autonomous mechanisms that are dependent on Shp2 catalytic activity. However, the effect of these mutations in the bone marrow microenvironment remains unclear. Here we report that Ptpn11 activating mutations in the mouse bone marrow microenvironment promote the development and progression of MPN through profound detrimental effects on haematopoietic stem cells (HSCs). Ptpn11 mutations in mesenchymal stem/progenitor cells and osteoprogenitors, but not in differentiated osteoblasts or endothelial cells, cause excessive production of the CC chemokine CCL3 (also known as MIP-1α), which recruits monocytes to the area in which HSCs also reside. Consequently, HSCs are hyperactivated by interleukin-1β and possibly other proinflammatory cytokines produced by monocytes, leading to exacerbated MPN and to donor-cell-derived MPN following stem cell transplantation. Remarkably, administration of CCL3 receptor antagonists effectively reverses MPN development induced by the Ptpn11-mutated bone marrow microenvironment. This study reveals the critical contribution of Ptpn11 mutations in the bone marrow microenvironment to leukaemogenesis and identifies CCL3 as a potential therapeutic target for controlling leukaemic progression in Noonan syndrome and for improving stem cell transplantation therapy in Noonan-syndrome-associated leukaemias.
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IJS, KISLJ, NUK, SBMB, UL, UM, UPUK
The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is crucial in controlling cellular activities in response to extracellular cytokines. Dysfunctions of the ...JAK/STAT pathway result in various hematopoietic and immune disorders. The central events in regulating this pathway are tyrosine phosphorylation and dephosphorylation of the signaling components, which are carried out by protein tyrosine kinases and protein tyrosine phosphatases (PTP), respectively. Here, we review recent advances in the regulatory roles of PTPs, in particular, SHP2 phosphatase, in the JAK/STAT signaling pathway.
The regulation and coordination of mitochondrial metabolism with hematopoietic stem cell (HSC) self-renewal and differentiation is not fully understood. Here we report that depletion of PTPMT1, a ...PTEN-like mitochondrial phosphatase, in inducible or hematopoietic-cell-specific knockout mice resulted in hematopoietic failure due to changes in the cell cycle and a block in the differentiation of HSCs. Surprisingly, the HSC pool was increased by ∼40-fold in PTPMT1 knockout mice. Reintroduction of wild-type PTPMT1, but not catalytically deficient PTPMT1 or truncated PTPMT1 lacking mitochondrial localization, restored differentiation capabilities of PTPMT1 knockout HSCs. Further analyses demonstrated that PTPMT1 deficiency altered mitochondrial metabolism and that phosphatidylinositol phosphate substrates of PTPMT1 directly enhanced fatty-acid-induced activation of mitochondrial uncoupling protein 2. Intriguingly, depletion of PTPMT1 from myeloid, T lymphoid, or B lymphoid progenitors did not cause any defects in lineage-specific knockout mice. This study establishes a crucial role of PTPMT1 in the metabolic regulation of HSC function.
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► PTPMT1 depletion causes cell cycle delay and differentiation block in HSCs ► The HSC pool in PTPMT1 knockout mice is drastically (∼40-fold) expanded ► Mitochondrial metabolism is altered and AMPK is highly activated in knockout HSCs ► PTPMT1 PIP substrates directly enhance fatty-acid-induced activation of UCP2
Knockout of the mitochondrial PTEN-like phosphatase PTPM1 reveals a role for mitochondrial metabolism in regulating HSC differentiation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Platinum-based chemotherapeutics represent a mainstay of cancer therapy, but resistance limits their curative potential. Through a kinome RNAi screen, we identified microtubule-associated ...serine/threonine kinase 1 (MAST1) as a main driver of cisplatin resistance in human cancers. Mechanistically, cisplatin but no other DNA-damaging agents inhibit the MAPK pathway by dissociating cRaf from MEK1, while MAST1 replaces cRaf to reactivate the MAPK pathway in a cRaf-independent manner. We show clinical evidence that expression of MAST1, both initial and cisplatin-induced, contributes to platinum resistance and worse clinical outcome. Targeting MAST1 with lestaurtinib, a recently identified MAST1 inhibitor, restores cisplatin sensitivity, leading to the synergistic attenuation of cancer cell proliferation and tumor growth in human cancer cells and patient-derived xenograft models.
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•MAST1 is a synthetic lethal target for cisplatin therapy in cancer cells•Cisplatin binds to MEK1 and dissociates cRaf but not MAST1 from MEK1•MAST1 replaces cRaf to reactivate the MAPK pathway and confer cisplatin resistance•Lestaurtinib is a promising MAST1 inhibitor
Jin et al. show that cisplatin dissociates cRaf from MEK1 to inhibit the MAPK pathway and identify MAST1 as a main cisplatin resistance driver that replaces cRaf to reactivate the MAPK pathway. They further show that inhibition of MAST1 by the multi-kinase inhibitor lestaurtinib restores cisplatin sensitivity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
MDM2 and XIAP are mutually regulated. Binding of MDM2 RING protein to the IRES region on XIAP mRNA results in MDM2 protein stabilization and enhanced XIAP translation. In this study, we developed a ...protein-RNA fluorescence polarization (FP) assay for high-throughput screening (HTS) of chemical libraries. Our FP-HTS identified eight inhibitors that blocked the MDM2 protein-XIAP RNA interaction, leading to MDM2 degradation. The compound-induced MDM2 downregulation resulted not only in inhibition of XIAP expression, but also in activation of p53, which contributed to cancer cell apoptosis in vitro and inhibition of cancer cell proliferation in vivo. Importantly, one of the MDM2/XIAP inhibitors, MX69, showed minimal inhibitory effect on normal human hematopoiesis in vitro and was very well tolerated in animal models.
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•MDM2/XIAP inhibitors are selected by FP-HTS via blocking MDM2-XIAP IRES interaction•MDM2/XIAP inhibitors degrade MDM2, activate p53, and inhibit XIAP expression•MDM2/XIAP inhibitors exhibit anticancer activity in vitro and in animal models•One of the MDM2/XIAP inhibitors MX69 is very well tolerated in animals
Gu et al. use chemical screening to identify inhibitors of the MDM2 protein-XIAP mRNA interaction and show these inhibitors lead to apoptosis by reducing XIAP protein, decreasing MDM2 stability, and increasing p53 levels. Animal testing of one of these compounds shows antitumor efficacy and minimal toxicity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Amino acid-mediated metabolism is one of the key catabolic and anabolic processes involved in diverse cellular functions. However, the role of the semi-essential amino acid arginine in normal and ...malignant hematopoietic cell development is poorly understood. Here we report that a continuous supply of exogenous arginine is required for the maintenance/function of normal hematopoietic stem cells (HSCs). Surprisingly, knockout of Slc7a3 (CAT3), a major L-arginine transporter, does not affect HSCs in steady-state or under stress. Although Slc7a3 is highly expressed in naïve and activated CD8 T cells, neither T cell development nor activation/proliferation is impacted by Slc7a3 depletion. Furthermore, the Slc7a3 deletion does not attenuate leukemia development driven by Pten loss or the oncogenic Ptpn11
mutation. Arginine uptake assays reveal that L-arginine uptake is not disrupted in Slc7a3 knockout cells. These data suggest that extracellular arginine is critically important for HSCs, but CAT3 is dispensable for normal hematopoiesis and leukemogenesis.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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