首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 0 毫秒
1.
Apoptosis plays an essential role in the control of erythropoiesis under normal and pathological conditions. However, the contribution of individual proteins within cell death signalling pathways remains poorly defined. Here, we investigated the role of the pro-apoptotic Bcl-2 family member Noxa in the regulation of erythropoiesis. We found that expression of Noxa is induced during erythroid differentiation of human and murine precursor cells. Using in vitro model systems for erythroid progenitors, we observed rapid induction of Noxa upon cytokine deprivation. Knockdown or deletion of Noxa conferred significant protection against apoptosis upon cytokine withdrawal. In vivo, Noxa deficiency did not affect hematological blood parameters or erythroid progenitor composition of bone marrow and spleen under steady-state conditions. In contrast, in a model of acute haemolytic anemia, Noxa-deficiency enhanced hematocrit recovery. Moreover, in a model of chronic inflammation-induced anemia, Noxa-ablation resulted in a dramatic increase of erythroblast expansion. Our data indicate that induction of Noxa in erythroid progenitors sets a survival threshold that limits expansion beyond the number of cells that can be sustained by the available cytokines, which becomes apparent under conditions of induced anemia.  相似文献   

2.
3.
Mitochondria form reticular networks comprised of filamentous tubules and continuously move and change shape. Bcl-2 family proteins actively participate in the regulation of mitochondria fragmentation. Here, we show that human Noxa, which belongs to the BH3-only pro-apoptotic Bcl-2 family, causes mitochondrial fragmentation. We found that while the Bcl-2 homology 3 (BH3) domain of Noxa is not associated with mitochondrial fragmentation, the mitochondrial targeting domain (MTD) of Noxa is the region responsible for inducing fragmentation. Two leucine residues in MTD play a key role in the process. Furthermore, the lack of Noxa causes a significant reduction of Velcade-induced mitochondrial fragmentation. Together, these results provide novel insight into the role of Noxa in mitochondrial dynamics and cell death.  相似文献   

4.
Hepatocellular carcinoma (HCC) represents a global health challenge with limited therapeutic options. Anti-angiogenic immune checkpoint inhibitor-based combination therapy has been introduced for progressed HCC, but improves survival only in a subset of HCC patients. Tyrosine-kinase inhibitors (TKI) such as sorafenib represent an alternative treatment option but have only modest efficacy. Using different HCC cell lines and HCC tissues from various patients reflecting HCC heterogeneity, we investigated whether the sorafenib response could be enhanced by combination with pro-apoptotic agents, such as TNF-related apoptosis-inducing ligand (TRAIL) or the BH3-mimetic ABT-737, which target the death receptor and mitochondrial pathway of apoptosis, respectively. We found that both agents could enhance sorafenib-induced cell death which was, however, dependent on specific BH3-only proteins. TRAIL augmented sorafenib-induced cell death only in NOXA-expressing HCC cells, whereas ABT-737 enhanced the sorafenib response also in NOXA-deficient cells. ABT-737, however, failed to augment sorafenib cytotoxicity in the absence of BIM, even when NOXA was strongly expressed. In the presence of NOXA, BIM-deficient HCC cells could be in turn strongly sensitized for cell death induction by the combination of sorafenib with TRAIL. Accordingly, HCC tissues sensitive to apoptosis induction by sorafenib and TRAIL revealed enhanced NOXA expression compared to HCC tissues resistant to this treatment combination. Thus, our results suggest that BH3-only protein expression determines the treatment response of HCC to different sorafenib-based drug combinations. Individual profiling of BH3-only protein expression might therefore assist patient stratification to certain TKI-based HCC therapies.Subject terms: Cancer, Diseases  相似文献   

5.
Previous studies proposed that myosin-Va regulates apoptosis by sequestering pro-apoptotic Bmf to the actin cytoskeleton through dynein light chain-2 (DLC2). Adhesion loss or other cytoskeletal perturbations would unleash Bmf, allowing it to bind and inhibit pro-survival Bcl2 proteins. Here, we demonstrated that overexpression of a myosin-Va medial tail fragment (MVaf) harboring the binding site for DLC2 dramatically decreased melanoma cell viability. Morphological and molecular changes, including surface blebbing, mitochondrial outer membrane permeabilization, cytochrome-c and Smac release, as well as caspase-9/-3 activation and DNA fragmentation indicated that melanoma cells died of apoptosis. Immobilized MVaf interacted directly with DLCs, but complexed MVaf/DLCs did not interact with Bmf. Overexpression of DLC2 attenuated MVaf-induced apoptosis. Thus, we suggest that, MVaf induces apoptosis by sequestering DLC2 and DLC1, thereby unleashing the pair of sensitizer and activator BH3-only proteins Bmf and Bim. Murine embryonic fibroblasts (MEFs) lacking Bim and Bmf or Bax and Bak were less sensitive to apoptosis caused by MVaf expression than wild-type MEFs, strengthening the putative role of the intrinsic apoptotic pathway in this response. Finally, MVaf expression attenuated B16-F10 solid tumor growth in mice, suggesting that this peptide may be useful as an apoptosis-inducing tool for basic and translational studies.  相似文献   

6.
Documented sensitivity of melanoma cells to PLX4720, a selective BRAFV600E inhibitor, is based on the presence of mutant BRAF(V600E) alone, while wt-BRAF or mutated KRAS result in cell proliferation. In colon cancer appearance of oncogenic alterations is complex , since BRAF, like KRAS mutations, tend to co-exist with those in PIK3CA and mutated PI3K has been shown to interfere with the successful application of MEK inhibitors. When PLX4720 was used to treat colon tumours, results were not encouraging and herein we attempt to understand the cause of this recorded resistance and discover rational therapeutic combinations to resensitize oncogene driven tumours to apoptosis. Treatment of two genetically different BRAF(V600E) mutant colon cancer cell lines with PLX4720 conferred complete resistance to cell death. Even though p-MAPK/ ERK kinase (MEK) suppression was achieved, TRAIL, an apoptosis inducing agent, was used synergistically in order to achieve cell death by apoptosis in RKO(BRAFV600E/PIK3CAH1047) cells. In contrast, for the same level of apoptosis in HT29(BRAFV600E/PIK3CAP449T) cells, TRAIL was combined with 17-AAG, an Hsp90 inhibitor. For cells where PLX4720 was completely ineffective, 17-AAG was alternatively used to target mutant BRAF(V600E). TRAIL dependence on the constitutive activation of BRAF(V600E) is emphasised through the overexpression of BRAF(V600E) in the permissive genetic background of colon adenocarcinoma Caco-2 cells. Pharmacological suppression of the PI3K pathway further enhances the synergistic effect between TRAIL and PLX4720 in RKO cells, indicating the presence of PIK3CA(MT) as the inhibitory factor. Another rational combination includes 17-AAG synergism with TRAIL in a BRAF(V600E) mutant dependent manner to commit cells to apoptosis, through DR5 and the amplification of the apoptotic pathway. We have successfully utilised combinations of two chemically unrelated BRAF(V600E) inhibitors in combination with TRAIL in a BRAF(V600E) mutated background and provided insight for new anti-cancer strategies where the activated PI3KCA mutation oncogene should be suppressed.  相似文献   

7.
Activation of the c‐Kit receptor tyrosine kinase is rare in melanoma, but occurs in 20‐40% of melanoma arising on mucosal membranes, acral skin and skin with chronic sun‐induced damage. Many activating c‐Kit mutations have been shown to be highly sensitive to imatinib mesylate, although the majority of patients with c‐Kit mutant melanoma eventually progress on this inhibitor. We examined acquired resistance to imatinib and the newer generation inhibitor nilotinib in resistant c‐kit mutant melanoma sublines. Four imatinib‐resistant and six nilotinib‐resistant sublines had acquired additional, secondary c‐Kit mutations. The secondary A829P c‐Kit mutation rendered cells resistant to imatinib, but did not suppress the activity of the tyrosine kinase inhibitors nilotinib and dasatinib. Sublines with an additional T670I c‐Kit mutation showed resistance to imatinib, nilotinib and dasatinib, but responded to sunitinib. The concurrent inhibition of the MAPK and PI3K pathways was also effective at promoting apoptosis in the parent and derived resistant sublines. Our data provide a rationale for treating patients with melanoma progressing on imatinib or nilotinib with alternative RTK inhibitors or inhibitors targeting the MAPK and PI3K signalling cascades.  相似文献   

8.
Valproic acid (VPA, 2-propylpentanoic acid) is an established drug in the long-term therapy of epilepsy. Recently, VPA was demonstrated to inhibit histone deacetylases (HDACs) class I enzyme at therapeutically relevant concentrations, thereby, mimicking the prototypical histone deacetylase inhibitors, tricostatin A (TSA) or suberoylanilide hydroxamic acid (SAHA). In the present study, we investigated the cellular effects of VPA, TSA and SAHA on four human melanoma cell lines (WM115, WM266, A375, SK-Mel28) with particular reference to the modulation of regulators of apoptosis, including Bcl-2, BclXL, Mcl-1, Apaf-1, BclXs, NOXA, TRAIL-R1, TRAIL-R2, caspase 8, and survivin). Firstly, we found that VPA induced apoptosis in two of the four human melanoma cell lines, while both TSA and SAHA exhibited an antiproliferative and apoptotic effects in all four cell lines, a different expression of Bcl-2 and BclX(L/S) occurred. On the other hand, SAHA and VPA modulated differently pro- and anti-apoptotic factors. In particular, the treatment with VPA enhanced the level of expression of survivin only in VPA-resistant cell lines, whereas down-regulation of survivin was induced by VPA and SAHA in VPA-sensitive cells. In the latter, since activation of caspase 8 was documented, a receptor-mediated apoptosis was suggested. Taken together, our results suggest that HDAC inhibitors may represent a promising therapeutic strategy to treat melanoma.  相似文献   

9.
10.
赵小平  钱关祥 《生命科学》2005,17(5):411-413
Bcl-2家族蛋白质在细胞凋亡的调控机制中起着重要的作用,该家族包括唯BH3结构域的蛋白质(only BH3 domain protein),如Bid、Bik、Puma、Nova、Bmf等。随着凋亡研究的深入,在哺乳动物中现已发现10多种唯BH3结构域的蛋白质,并且在凋亡中发挥重要的作用。本文主要论述唯BH3域蛋白的作用机制及其应用的研究进展。  相似文献   

11.
An activating BRAF (V600E) kinase mutation occurs in approximately half of melanomas. Recent clinical studies have demonstrated that vemurafenib (PLX4032) and dabrafenib, potent and selective inhibitors of mutant v-raf murine sarcoma viral oncogene homolog B1 (BRAF), exhibit remarkable activities in patients with V600 BRAF mutant melanomas. However, acquired drug resistance invariably develops after the initial treatment. Identification of acquired resistance mechanisms may inform the development of new therapies that elicit long-term responses of melanomas to BRAF inhibitors. Here we report that increased expression of AEBP1 (adipocyte enhancer-binding protein 1) confers acquired resistance to BRAF inhibition in melanoma. AEBP1 is shown to be highly upregulated in PLX4032-resistant melanoma cells because of the hyperactivation of the PI3K/Akt-cAMP response element-binding protein (CREB) signaling pathway. This upregulates AEBP1 expression and thus leads to the activation of NF-κB via accelerating IκBa degradation. In addition, inhibition of the PI3K/Akt-CREB-AEBP1-NF-κB pathway greatly reverses the PLX4032-resistant phenotype of melanoma cells. Furthermore, increased expression of AEBP1 is validated in post-treatment tumors in patients with acquired resistance to BRAF inhibitor. Therefore, these results reveal a novel PI3K/Akt-CREB-AEBP1-NF-κB pathway whose activation contributes to acquired resistance to BRAF inhibition, and suggest that this pathway, particularly AEBP1, may represent a novel therapeutic target for treating BRAF inhibitor-resistant melanoma.  相似文献   

12.
Mitochondrial outer membrane permeabilization is a watershed event in the process of apoptosis, which is tightly regulated by a series of pro- and anti-apoptotic proteins belonging to the BCL-2 family, each characteristically possessing a BCL-2 homology domain 3 (BH3). Here, we identify a yeast protein (Ybh3p) that interacts with BCL-X(L) and harbours a functional BH3 domain. Upon lethal insult, Ybh3p translocates to mitochondria and triggers BH3 domain-dependent apoptosis. Ybh3p induces cell death and disruption of the mitochondrial transmembrane potential via the mitochondrial phosphate carrier Mir1p. Deletion of Mir1p and depletion of its human orthologue (SLC25A3/PHC) abolish stress-induced mitochondrial targeting of Ybh3p in yeast and that of BAX in human cells, respectively. Yeast cells lacking YBH3 display prolonged chronological and replicative lifespans and resistance to apoptosis induction. Thus, the yeast genome encodes a functional BH3 domain that induces cell death through phylogenetically conserved mechanisms.  相似文献   

13.
The proapoptotic Bcl2 homology domain 3(BH3)-only protein Bim is controlled by stringent post-translational regulation, predominantly through alterations in phosphorylation status. To identify new kinases involved in its regulation, we carried out a yeast two-hybrid screen using a non-spliceable variant of the predominant isoform--Bim(EL)--as the bait and identified the regulatory subunit of cyclic-AMP-dependent protein kinase A--PRKAR1A--as an interacting partner. We also show that protein kinase A (PKA) is a Bim(EL) isoform-specific kinase that promotes its stabilization. Inhibition of PKA or mutation of the PKA phosphorylation site within Bim(EL) resulted in its accelerated proteasome-dependent degradation. These results might have implications for human diseases that are characterized by abnormally increased PKA activity, such as the Carney complex and dilated cardiomyopathy.  相似文献   

14.
Resistance to drug treatment is a common observation in malignant melanoma. In order to analyze alterations in mRNA expression profiles associated with drug resistance in melanoma cells we previously established a panel of various drug-resistant cell variants derived from the human melanoma line MeWo and compared the mRNA expression profiles by a differential display technique. By that approach it could be demonstrated that the expression level of a mRNA encoded by a gene found to be mutated in non-syndromic hearing impairment, DFNA5 (ICERE-1), was distinctly decreased in the 33-fold etoposide-resistant melanoma cell line MeWo ETO 1. To evaluate the hypothesis that a decrease in DFNA5 mRNA expression level contributes to the acquired etoposide resistance phenotype exhibited by MeWo ETO 1 cells, this drug-resistant line was stably transfected with the DFNA5-encoding cDNA. Transfected clones showed a 30-35% reduced etoposide susceptibility by comparing the IC(25), IC(50) and IC(75) values of these clones with those displayed by the non-transfected, etoposide-resistant melanoma cell line MeWo ETO 1 and controls. Furthermore, etoposide exposure of stable DFNA5 transfectants resulted in an increase of caspase-3-mediated apoptotic events in DFNA5-transfected clones in comparison to MeWo ETO 1 cells and controls. The data therefore demonstrate that a decrease in DNFA5 mRNA expression level is associated with an increased etoposide resistance in melanoma cells due to an elevated cellular susceptibility to trigger a caspase-3-depending signal pathway leading to programmed cell death.  相似文献   

15.
16.
Apolipoproteins of the L family are lipid-binding proteins whose function is largely unknown. Apolipoprotein L1 and apolipoprotein L6 have been recently described as novel pro-death BH3-only proteins that are also capable of regulating autophagy. In an in-silico screening to discover novel putative BH3-only proteins, we identified yet another member of the apolipoprotein L family, apolipoprotein L2 (ApoL2), as a BH3 motif-containing protein. ApoL2 has been suggested to behave as a BH3-only protein and mediate cell death induced by interferon-gamma or viral infection. As previously described, we observed that ApoL2 protein was induced by interferon-gamma. However, knocking down its expression in HeLa cells did not regulate cell death induced by interferon-gamma. Overexpression of ApoL2 did not induce cell death on its own. ApoL2 did not sensitize or protect cells from overexpression of the BH3-only proteins Bmf or Noxa. Furthermore, siRNA against ApoL2 did not alter sensitivity to a variety of death stimuli. We could, however, detect a weak interaction between ApoL2 and Bcl-2 by immunoprecipitation of the former, suggesting a role of ApoL2 in a Bcl-2-regulated process like autophagy. However, in contrast to what has been described about its homologs ApoL1 and ApoL6, ApoL2 did not regulate autophagy. Thus, the role, if any, of ApoL2 in cell death remains to be clarified.  相似文献   

17.
This review will focus on the role of the tumor microenvironment (TME) in the development of drug resistance in melanoma. Resistance to mitogen‐activated protein kinase inhibitors (MAPKi) in melanoma is observed months after treatment, a phenomenon that is often attributed to the incredible plasticity of melanoma cells but may also depend on the TME. The TME is unique in its cellular composition—it contains fibroblasts, immune cells, endothelial cells, adipocytes, and among others. In addition, the TME provides “non‐homeostatic” levels of oxygen, nutrients (hypoxia and metabolic stress), and extracellular matrix proteins, creating a pro‐tumorigenic niche that drives resistance to MAPKi treatment. In this review, we will focus on how changes in the tumor microenvironment regulate MAPKi resistance.  相似文献   

18.
The vascular endothelial growth factor receptor‐1 (VEGFR‐1) is a tyrosine kinase receptor frequently expressed in melanoma. Its activation by VEGF‐A or placental growth factor (PlGF) promotes tumour cell survival, migration and invasiveness. Moreover, VEGFR‐1 stimulation contributes to pathological angiogenesis and induces recruitment of tumour‐associated macrophages. Since melanoma acquired resistance to BRAF inhibitors (BRAFi) has been associated with activation of pro‐angiogenic pathways, we have investigated VEGFR‐1 involvement in vemurafenib resistance. Results indicate that human melanoma cells rendered resistant to vemurafenib secrete greater amounts of VEGF‐A and express higher VEGFR‐1 levels compared with their BRAFi‐sensitive counterparts. Transient VEGFR‐1 silencing in susceptible melanoma cells delays resistance development, whereas in resistant cells it increases sensitivity to the BRAFi. Consistently, enforced VEGFR‐1 expression, by stable gene transfection in receptor‐negative melanoma cells, markedly reduces sensitivity to vemurafenib. Moreover, melanoma cells expressing VEGFR‐1 are more invasive than VEGFR‐1 deficient cells and receptor blockade by a specific monoclonal antibody (D16F7 mAb) reduces extracellular matrix invasion triggered by VEGF‐A and PlGF. These data suggest that VEGFR‐1 up‐regulation might contribute to melanoma progression and spreading after acquisition of a drug‐resistant phenotype. Thus, VEGFR‐1 inhibition with D16F7 mAb might be a suitable adjunct therapy for VEGFR‐1 positive tumours with acquired resistance to vemurafenib.  相似文献   

19.
20.
One group of Bcl-2 protein family, which shares only the BH3 domain (BH3-only), is critically involved in the regulation of programmed cell death. Herein we demonstrated a novel human BH3-only protein (designated as Bop) which could induce apoptosis in a BH3 domain-dependent manner. Further analysis indicated that Bop mainly localized to mitochondria and used its BH3 domain to contact the loop regions of voltage dependent anion channel 1 (VDAC1) in the outer mitochondrial membrane. In addition, purified Bop protein induced the loss of mitochondrial transmembrane potential (ΔΨm) and the release of cytochrome c. Furthermore, Bop used its BH3 domain to contact pro-survival Bcl-2 family members (Bcl-2, Bcl-XL, Mcl-1, A1 and Bcl-w), which could inhibit Bop-induced apoptosis. Bop would be constrained by pro-survival Bcl-2 proteins in resting cells, because Bop became released from phosphorylated Bcl-2 induced by microtubule-interfering agent like vincristine (VCR). Indeed, knockdown experiments indicated that Bop was partially required for VCR induced cell death. Finally, Bop might need to function through Bak and Bax, likely by releasing Bak from Bcl-XL sequestration. In conclusion, Bop may be a novel BH3-only factor that can engage with the regulatory network of Bcl-2 family members to process intrinsic apoptotic signaling.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号