The molecular codes underpinning the functions of plant NLR immune receptors are poorly understood. We used in vitro Mu transposition to generate a random truncation library and identify the minimal ...functional region of NLRs. We applied this method to NRC4-a helper NLR that functions with multiple sensor NLRs within a Solanaceae receptor network. This revealed that the NRC4 N-terminal 29 amino acids are sufficient to induce hypersensitive cell death. This region is defined by the consensus MADAxVSFxVxKLxxLLxxEx (MADA motif) that is conserved at the N-termini of NRC family proteins and ~20% of coiled-coil (CC)-type plant NLRs. The MADA motif matches the N-terminal α1 helix of Arabidopsis NLR protein ZAR1, which undergoes a conformational switch during resistosome activation. Immunoassays revealed that the MADA motif is functionally conserved across NLRs from distantly related plant species. NRC-dependent sensor NLRs lack MADA sequences indicating that this motif has degenerated in sensor NLRs over evolutionary time.
The MAPK pathway is one of the most important pathways for novel anticancer drug development. We performed high-throughput screening for compounds that induce expression of p15INK4b, and identified ...JTP-74057 (GSK1120212), which is being evaluated in ongoing phase I, II and III clinical trials. We characterized its antitumor activities in vitro and in vivo. JTP-74057 strongly inhibited MEK1/2 kinase activities, but did not inhibit another 98 kinase activities. Treatment by JTP-74057 resulted in growth inhibition accompanied with upregulation of p15INK4b and/or p27KIP1 in most of the colorectal cancer cell lines tested. Daily oral administration of JTP-74057 for 14 days suppressed tumor growth of HT-29 and COLO205 xenografts in nude mice. Notably, tumor regression was observed only in COLO205 xenografts, and COLO205 was much more sensitive to JTP-74057-induced apoptosis than HT-29 in vitro. Treatment with an Akt inhibitor enhanced the JTP-74057-induced apoptosis in HT-29 cells. Finally, JTP-74057 exhibited an additive or a synergistic effect in combination with the standard-of-care agents, 5-fluorouracil, oxaliplatin or SN-38. JTP-74057, a highly specific and potent MEK1/2 inhibitor, exerts favorable antitumor activities in vitro and in vivo. Sensitivity to JTP-74057-induced apoptosis may be an important factor for the estimation of in vivo efficacy, and sensitivity was enhanced by an Akt inhibitor. These results suggest the usefulness of JTP-74057 in therapeutic applications for colorectal cancer patients.
Abstract
Myostatin (Mstn) and GDF11 are critical factors that are involved in muscle atrophy in the young and sarcopenia in the elderly, respectively. These TGF-β superfamily proteins activate not ...only Smad signalling but also non-Smad signalling including the Ras-mediated ERK pathway (Raf–MEK–ERK phosphorylation cascade). Although Mstn and GDF11 have been shown to induce muscle atrophy or sarcopenia by Smad2/3-mediated Akt inhibition, participation of the non-Smad Ras–ERK pathway in atrophy and sarcopenia has not been well determined. We show here that both Mstn and GDF11 prevented skeletal myocyte differentiation but that the MEK inhibitor U0126 or trametinib restored differentiation in Mstn- or GDF11-treated myocytes. These MEK inhibitors induced the expression of DA-Raf1 (DA-Raf), which is a dominant-negative antagonist of the Ras–ERK pathway. Exogenous expression of DA-Raf in Mstn- or GDF11-treated myocytes restored differentiation. Furthermore, administration of trametinib to aged mice resulted in an increase in myofiber size or recovery from muscle atrophy. The trametinib administration downregulated ERK activity in these muscles. These results imply that the Mstn/GDF11-induced Ras–ERK pathway plays critical roles in the inhibition of myocyte differentiation and muscle regeneration, which leads to muscle atrophy. Trametinib and similar approved drugs might be applicable to the treatment of muscle atrophy in sarcopenia or cachexia.
Graphical Abstract
Graphical Abstract
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The NRC immune receptor network has evolved in asterid plants from a pair of linked genes into a genetically dispersed and phylogenetically structured network of sensor and helper NLR ...(nucleotide-binding domain and leucine-rich repeat-containing) proteins. In some species, such as the model plant Nicotiana benthamiana and other Solanaceae, the NRC (NLR-REQUIRED FOR CELL DEATH) network forms up to half of the NLRome, and NRCs are scattered throughout the genome in gene clusters of varying complexities. Here, we describe NRCX, an atypical member of the NRC family that lacks canonical features of these NLR helper proteins, such as a functional N-terminal MADA motif and the capacity to trigger autoimmunity. In contrast to other NRCs, systemic gene silencing of NRCX in N. benthamiana markedly impairs plant growth resulting in a dwarf phenotype. Remarkably, dwarfism of NRCX silenced plants is partially dependent on NRCX paralogs NRC2 and NRC3, but not NRC4. Despite its negative impact on plant growth when silenced systemically, spot gene silencing of NRCX in mature N. benthamiana leaves doesn't result in visible cell death phenotypes. However, alteration of NRCX expression modulates the hypersensitive response mediated by NRC2 and NRC3 in a manner consistent with a negative role for NRCX in the NRC network. We conclude that NRCX is an atypical member of the NRC network that has evolved to contribute to the homeostasis of this genetically unlinked NLR network.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The phosphatidylinositol 3-kinase (PI3K) signaling pathway is activated in a broad spectrum of human cancers, including colon cancer. The natural product brassinin is a type of indole compound ...derived from cruciferous vegetables, and has been shown to have anti-proliferative effects against cancer for both in vivo and in vitro models. Here, we show for the first time that brassinin inhibits cell growth in human colon cancer cells by arresting the cell cycle at the G1 phase via inhibition of the PI3K signaling pathway. Brassinin increased the expression of p21 and p27, resulting in hypophosphorylation of the retinoblastoma gene (RB). Knockdown of p21 or p27 by each siRNA significantly repressed G1 phase arrest induced by brassinin. The increase of p21 and p27 was associated with inhibition of the PI3K signaling pathway. In addition, exogenous expression of constitutively active Akt represses the cell cycle arrest at G1 phase induced by brassinin. These results suggest the possibility that brassinin inhibits the PI3K signaling pathway and upregulates the expression of p21 and p27, thereby inducing G1 phase arrest.
Genetic mutations in exons of oncogenes and tumor‐suppressor genes causing qualitative abnormalities result in activation of the oncogenes and inactivation of the tumor‐suppressor genes, thereby ...causing cancer. In contrast, we have previously demonstrated that decreases in the RB promoter activity by genetic or epigenetic abnormalities can also cause carcinogenesis. In addition, activation and inactivation of a variety of oncogenes and tumor‐suppressor genes finally cause quantitative abnormalities in gene expression. Interestingly, we discovered effective molecular‐targeting agents, such as a novel MEK inhibitor, trametinib, by screening for agents upregulating the expression of cyclin‐dependent kinase inhibitors. In the present review, we focused on the quantitative abnormalities in gene expression with carcinogenesis, and discuss the importance of normalizing the quantitative abnormalities in gene expression with several molecular‐targeting agents.
In this manuscript, we focused on the quantitative abnormalities in gene expression with carcinogenesis, and discussed the importance of normalizing the quantitative abnormalities in gene expression by molecular‐targeting agents.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Chemotherapy for colorectal cancer has become more complicated and diversified with the appearance of molecular‐targeting agents. 5‐Fluorouracil (5‐FU) has been a mainstay of chemotherapy for ...colorectal cancer, but it is still unknown whether the combining of 5‐FU with novel molecular‐targeting agents is effective. Thymidylate synthase (TS) is a direct target of 5‐FU, and the low TS level has been generally supposed to sensitize 5‐FU's efficacy. We therefore hypothesized that RB‐reactivating agents could enhance the efficacy of 5‐FU, because the RB‐reactivating agents could suppress the function of transcription factor E2F of TS gene promoter. We used three RB‐reactivating agents, trametinib/GSK1120212 (MEK inhibitor), fenofibrate (PPARα agonist), and LY294002 (PI3K inhibitor), with 5‐FU against human colon cancer HT‐29 and HCT15 cells. Trametinib induced p15 and p27 expression and reduced cyclin D1 levels in HT‐29 cells. Fenofibrate also dephosphorlated ERK1/2 and reduced cyclin D1 levels in HT‐29 cells. LY294002 induced p27 expression in HCT15 cells. All three agents caused dephosphorylation of RB protein and G1‐phase arrest with a reduction of TS expression. As a consequence, the combination of 5‐FU with each of the agents resulted in a significant decrease of colony numbers in HT‐29 or HCT15 cells. These results suggest “RB‐reactivation therapy” using molecular‐targeting agents to be a new strategy for 5‐FU‐based chemotherapy. In particular, we strongly expect trametinib, which was discovered in Japan and was recently submitted to FDA for approval, to be used together with established regimens for colorectal cancer.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Although many chemotherapeutic strategies against cancer have been developed, pancreatic cancer is one of the most aggressive and intractable types of malignancies. Therefore, new strategies and ...anti-cancer agents are necessary to treat this disease. Metformin is a widely used drug for type-2 diabetes, and is also known as a promising candidate anti-cancer agent from recent studies in vitro and in vivo. However, the mechanisms of metformin's anti-cancer effects have not been elucidated. We demonstrated that metformin suppressed the expression of miR-221, one of the most well-known oncogenic microRNAs, in human pancreatic cancer PANC-1 cells. Moreover, we showed that the down-regulation of miR-221 by metformin caused G1-phase arrest via the up-regulation of p27, one of the direct targets of miR-221. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is also a promising agent for cancer treatment. While recent studies showed that treatment with only TRAIL was not effective against pancreatic cancer cells, the present data showed that metformin sensitized p53-mutated pancreatic cancer cells to TRAIL. Metformin induced the expressions of death receptor 5 (DR5), a receptor for TRAIL, and Bim with a pro-apoptotic function in the downstream of TRAIL-DR5 pathway. We suggest that the up-regulation of these proteins may contribute to sensitization of TRAIL-induced apoptosis. The combination therapy of metformin and TRAIL could therefore be effective in the treatment of pancreatic cancer.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
KRAS mutation is frequently seen in a subtype of ovarian cancer categorized as type 1. The KRAS‐MAPK pathway, which is closely involved in type 1 cancer progression, is under the regulation of ...receptor tyrosine kinases (RTKs). AXL, one of the RTKs, has been reported to be overexpressed in ovarian cancer and contributes to the poor prognosis. However, there is no useful target‐based agent against such gene profiles. We examined the combined effect of the dual RAF/MEK inhibitor CH5126766 and AXL inhibitor R428 on the growth of ovarian cancer HEY‐T30 and OVCAR‐5 cell lines, both of which bear KRAS mutation and express AXL at a high level, using the WST‐8 assay and the colony formation assay. The synergistic effect of the combination was evaluated by the combination index. The apoptotic cells were analyzed by flow cytometry. The expression of apoptotic proteins and the phosphorylation of MAPK and AKT pathway proteins were investigated by western blotting. We found that CH5126766 and R428 suppressed the phosphorylation of ERK and AKT, respectively, and their combination synergistically inhibited the growth of both cell lines with enhancement of apoptosis accompanied by the Bim upregulation. Combined treatment with CH5126766 and R428 is expected as the novel therapeutic option for KRAS‐mutated ovarian cancer with high expression of AXL.
The combined treatment with a dual RAF/MEK inhibitor CH5126766 and AXL inhibitor R428 synergistically inhibited the growth of ovarian cancer HEY‐T30 and OVCAR‐5 cell lines, both of which bear KRAS mutation and express AXL at a high level, accompanied by inducing apoptosis.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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