RESUMO
Despite the immense success of immune checkpoint blockade (ICB) in cancer treatment, many tumors, including melanoma, exhibit innate or adaptive resistance. Tumor-intrinsic T-cell deficiency and T-cell dysfunction have been identified as essential factors in the emergence of ICB resistance. Here, we found that protein arginine methyltransferase 1 (PRMT1) expression was inversely correlated with the number and activity of CD8+ T cells within melanoma specimen. PRMT1 deficiency or inhibition with DCPT1061 significantly restrained refractory melanoma growth and increased intratumoral CD8+ T cells in vivo. Moreover, PRMT1 deletion in melanoma cells facilitated formation of double-stranded RNA derived from endogenous retroviral elements (ERV) and stimulated an intracellular interferon response. Mechanistically, PRMT1 deficiency repressed the expression of DNA methyltransferase 1 (DNMT1) by attenuating modification of H4R3me2a and H3K27ac at enhancer regions of Dnmt1, and DNMT1 downregulation consequently activated ERV transcription and the interferon signaling. Importantly, PRMT1 inhibition with DCPT1061 synergized with PD-1 blockade to suppress tumor progression and increase the proportion of CD8+ T cells as well as IFNγ+CD8+ T cells in vivo. Together, these results reveal an unrecognized role and mechanism of PRMT1 in regulating antitumor T-cell immunity, suggesting PRMT1 inhibition as a potent strategy to increase the efficacy of ICB. SIGNIFICANCE: Targeting PRMT1 stimulates interferon signaling by increasing expression of endogenous retroviral elements and double-stranded RNA through repression of DNMT1, which induces antitumor immunity and synergizes with immunotherapy to suppress tumor progression.
Assuntos
Interferons , Melanoma , Humanos , Melanoma/metabolismo , RNA de Cadeia Dupla , Linfócitos T CD8-Positivos , Metiltransferases/metabolismo , Proteína-Arginina N-Metiltransferases/metabolismo , Proteínas Repressoras/genética , Proteínas Repressoras/metabolismoRESUMO
In castration-resistant prostate cancer (CRPC), clinical response to androgen receptor (AR) antagonists is limited mainly due to AR-variants expression and restored AR signaling. The metabolite spermine is most abundant in prostate and it decreases as prostate cancer progresses, but its functions remain poorly understood. Here, we show spermine inhibits full-length androgen receptor (AR-FL) and androgen receptor splice variant 7 (AR-V7) signaling and suppresses CRPC cell proliferation by directly binding and inhibiting protein arginine methyltransferase PRMT1. Spermine reduces H4R3me2a modification at the AR locus and suppresses AR binding as well as H3K27ac modification levels at AR target genes. Spermine supplementation restrains CRPC growth in vivo. PRMT1 inhibition also suppresses AR-FL and AR-V7 signaling and reduces CRPC growth. Collectively, we demonstrate spermine as an anticancer metabolite by inhibiting PRMT1 to transcriptionally inhibit AR-FL and AR-V7 signaling in CRPC, and we indicate spermine and PRMT1 inhibition as powerful strategies overcoming limitations of current AR-based therapies in CRPC.
Assuntos
Neoplasias de Próstata Resistentes à Castração , Receptores Androgênicos , Masculino , Humanos , Receptores Androgênicos/metabolismo , Neoplasias de Próstata Resistentes à Castração/tratamento farmacológico , Espermina/farmacologia , Transdução de Sinais , Antagonistas de Receptores de Andrógenos/uso terapêutico , Linhagem Celular Tumoral , Proteína-Arginina N-Metiltransferases/genética , Proteína-Arginina N-Metiltransferases/metabolismo , Proteínas Repressoras/metabolismoRESUMO
BACKGROUND: The repression or downregulation of programmed death-ligand 1 (PD-L1) can release its inhibition of T cells and activate antitumor immune responses. Although PD-1 and PD-L1 antibodies are promising treatments for diverse tumor types, their inherent disadvantages and immune-related adverse events remain significant issues. The development of small molecule inhibitors targeting the interaction surface of PD-1 and PD-L1 has been reviving, yet many challenges remain. To address these issues, we aimed to find small molecules with durable efficacy and favorable biosafety that alter PD-L1 surface expression and can be developed into a promising alternative and complementary therapy for existing anti-PD-1/PD-L1 therapies. METHODS: Cell-based screen of 200 metabolic molecules using a high-throughput flow cytometry assay of PD-L1 surface expression was conducted, and L-5-hydroxytryptophan (L-5-HTP) was found to suppress PD-L1 expression induced by interferon gamma (IFN-γ). Inhibition of PD-L1 induction and antitumor effect of L-5-HTP were evaluated in two syngeneic mouse tumor models. Flow cytometry was performed to investigate the change in the tumor microenvironment caused by L-5-HTP treatment. RESULTS: We discovered that L-5-HTP suppressed IFN-γ-induced PD-L1 expression in tumor cells transcriptionally, and this effect was directly due to itself. Mechanistically, L-5-HTP inhibited IFN-γ-induced expression of RTK ligands and thus suppressed phosphorylation-mediated activation of RTK receptors and the downstream MEK/ERK/c-JUN signaling cascade, leading to decreased PD-L1 induction. In syngeneic mouse tumor models, treatment with 100 mg/kg L-5-HTP (intraperitoneal) inhibited PD-L1 expression and exhibited antitumor effect. L-5-HTP upregulated the ratio of granzyme B+ CD8+ activated cytotoxic T cells. An intact immune system and PD-L1 expression was critical for L-5-HTP to exert its antitumor effects. Furthermore, L-5-HTP acted synergistically with PD-1 antibody to improve anticancer effect. CONCLUSION: Our study illustrated L-5-HTP's inhibitory effect on PD-L1 induction stimulated by IFN-γ in tumor cells and also provided insight into repurposing L-5-HTP for use in tumor immunotherapy.
Assuntos
5-Hidroxitriptofano , Antígeno B7-H1 , Receptor de Morte Celular Programada 1 , 5-Hidroxitriptofano/farmacologia , Animais , Antígeno B7-H1/imunologia , Linfócitos T CD8-Positivos/efeitos dos fármacos , Linfócitos T CD8-Positivos/imunologia , Humanos , Interferon gama/metabolismo , Camundongos , Receptor de Morte Celular Programada 1/antagonistas & inibidores , Receptor de Morte Celular Programada 1/biossíntese , Receptor de Morte Celular Programada 1/imunologiaRESUMO
Mantle cell lymphoma (MCL) is a lymphoproliferative disorder lacking reliable therapies. PI3K pathway contributes to the pathogenesis of MCL, serving as a potential target. However, idelalisib, an FDA-approved drug targeting PI3Kδ, has shown intrinsic resistance in MCL treatment. Here we report that a p300/CBP inhibitor, A-485, could overcome resistance to idelalisib in MCL cells in vitro and in vivo. A-485 was discovered in a combinational drug screening from an epigenetic compound library containing 45 small molecule modulators. We found that A-485, the highly selective catalytic inhibitor of p300 and CBP, was the most potent compound that enhanced the sensitivity of MCL cell line Z-138 to idelalisib. Combination of A-485 and idelalisib remarkably decreased the viability of three MCL cell lines tested. Co-treatment with A-485 and idelalisib in Maver-1 and Z-138 MCL cell xenograft mice for 3 weeks dramatically suppressed the tumor growth by reversing the unsustained inhibition in PI3K downstream signaling. We further demonstrated that p300/CBP inhibition decreased histone acetylation at RTKs gene promoters and reduced transcriptional upregulation of RTKs, thereby inhibiting the downstream persistent activation of MAPK/ERK signaling, which also contributed to the pathogenesis of MCL. Therefore, additional inhibition of p300/CBP blocked MAPK/ERK signaling, which rendered maintaining activation to PI3K-mTOR downstream signals p-S6 and p-4E-BP1, thus leading to suppression of cell growth and tumor progression and eliminating the intrinsic resistance to idelalisib ultimately. Our results provide a promising combination therapy for MCL and highlight the potential use of epigenetic inhibitors targeting p300/CBP to reverse drug resistance in tumor.
Assuntos
Classe Ia de Fosfatidilinositol 3-Quinase/efeitos dos fármacos , Linfoma de Célula do Manto/tratamento farmacológico , Purinas/uso terapêutico , Quinazolinonas/uso terapêutico , Fatores de Transcrição de p300-CBP/antagonistas & inibidores , Animais , Ciclo Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Classe Ia de Fosfatidilinositol 3-Quinase/metabolismo , Sinergismo Farmacológico , Feminino , Compostos Heterocíclicos de 4 ou mais Anéis/uso terapêutico , Humanos , Camundongos , Transplante de NeoplasiasRESUMO
The Rho family GTPases are crucial drivers of tumor growth and metastasis. However, it is difficult to develop GTPases inhibitors due to a lack of well-characterized binding pockets for compounds. Here, through molecular dynamics simulation of the RhoA protein, a groove around cysteine 107 (Cys107) that is relatively well-conserved within the Rho family is discovered. Using a combined strategy, the novel inhibitor DC-Rhoin is discovered, which disrupts interaction of Rho proteins with guanine nucleotide exchange factors (GEFs) and guanine nucleotide dissociation inhibitors (GDIs). Crystallographic studies reveal that the covalent binding of DC-Rhoin to the Cys107 residue stabilizes and captures a novel allosteric pocket. Moreover, the derivative compound DC-Rhoin04 inhibits the migration and invasion of cancer cells, through targeting this allosteric pocket of RhoA. The study reveals a novel allosteric regulatory site within the Rho family, which can be exploited for anti-metastasis drug development, and also provides a novel strategy for inhibitor discovery toward "undruggable" protein targets.
RESUMO
Bromodomain PHD finger transcription factor (BPTF), a bromodomain-containing protein, plays a crucial role in the regulation of downstream gene expression through the specific recognition of lysine acetylation on bulk histones. The dysfunction of BPTF is closely involved with the development and progression of many human diseases, especially cancer. Therefore, BPTF bromodomain has become a promising drug target for epigenetic cancer therapy. However, unlike BET family inhibitors, few BPTF bromodomain inhibitors have been reported. In this study, by integrating docking-based virtual screening with biochemical analysis, we identified a novel selective BPTF bromodomain inhibitor DCB29 with the IC50 value of 13.2⯱â¯1.6⯵M by homogenous time-resolved fluorescence resonance energy transfer (HTRF) assays. The binding between DCB29 and BPTF was confirmed by NMR and SPR. Molecular docking disclosed that DCB29 occupied the pocket of acetylated H4 peptide substrate and provided detailed SAR explanations for its derivatives. Collectively, DCB29 presented great potential as a powerful tool for BPTF-related biological research and further medicinal chemistry optimization.
Assuntos
Álcoois/farmacologia , Benzamidas/farmacologia , Descoberta de Drogas , Fatores de Transcrição/antagonistas & inibidores , Álcoois/síntese química , Álcoois/química , Benzamidas/síntese química , Benzamidas/química , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos , Transferência Ressonante de Energia de Fluorescência , Humanos , Simulação de Acoplamento Molecular , Estrutura Molecular , Domínios Proteicos/efeitos dos fármacos , Relação Estrutura-Atividade , Fatores de Transcrição/isolamento & purificação , Fatores de Transcrição/metabolismoRESUMO
The general control nonrepressed protein 5 (GCN5) is an important target for drug design and drug discovery largely owing to its pathogenic role in malignancies. Chemical probes that target GCN5 have been developed in recent decades, but their potencies are still unsatisfactory. In this study, through an in-house developed AlphaScreen-based high throughput screening platform, radioactive acetylation assays and 2D-similarity based analogue searching, we discovered DC_HG24-01 as the novel hGCN5 inhibitor with the IC50 value of 3.1 ± 0.2 µM. Further docking studies suggested that DC_HG24-01 could occupy the binding pocket of acetyl-CoA cofactor, which laid the foundation for the development of more potent hGCN5 inhibitors in the future. At the cellular level, DC_HG24-01 could retard cell proliferation and block the acetylation of H3K14 leading to cell apoptosis and cell cycle arrest at the G1 phase in MV4-11 cell lines. Taken together, the discovery of DC_HG24-01 may serve as a good starting point to accelerate the development of more potent hGCN5 inhibitors through further structural decoration and provide new insight into the pharmacological treatment of leukemia.
RESUMO
Cytokinesis is the last step of cell division and is concluded by the abscission of the intercellular bridge that connects two daughter cells. The tight regulation of cytokinesis completion is essential because cytokinesis failure is associated with various human diseases. Here, we report that iASPP, a member of the apoptosis-stimulating proteins of p53 (ASPP) family, is required for proper cell division. iASPP depletion results in abnormal midbody structure and failed cytokinesis. We used protein affinity purification methods to identify the functional partners of iASPP. We found that iASPP associates with centrosomal protein of 55 kDa (CEP55), an important cytokinetic abscission regulator. Mechanically, iASPP acts as a PP1-targeting subunit to facilitate the interaction between PP1 and CEP55 and to remove PLK1-mediated Ser436 phosphorylation in CEP55 during late mitosis. The latter step is critical for the timely recruitment of CEP55 to the midbody. The present observations revealed a previously unrecognized function of iASPP in cytokinesis. This function, in turn, likely contributes to the roles of iASPP in tumor development and genetic diseases.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Citocinese , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Complexos Multiproteicos/metabolismo , Proteínas de Neoplasias/metabolismo , Neoplasias/metabolismo , Proteínas Nucleares/metabolismo , Proteína Fosfatase 1/metabolismo , Proteínas Repressoras/metabolismo , Células A549 , Proteínas de Ciclo Celular/genética , Células HCT116 , Células HeLa , Humanos , Peptídeos e Proteínas de Sinalização Intracelular/genética , Mitose , Complexos Multiproteicos/genética , Proteínas de Neoplasias/genética , Neoplasias/genética , Neoplasias/patologia , Proteínas Nucleares/genética , Fosforilação/genética , Proteína Fosfatase 1/genética , Proteínas Repressoras/genéticaRESUMO
The BET family of bromodomain-containing proteins (BRDs) is believed to be a promising drug target for therapeutic intervention in a number of diseases including cancer, inflammation and cardiovascular diseases. Hence, there is a great demand for novel chemotypes of BET inhibitors. The drug repurposing strategy offers great benefits to find inhibitors with known safety and pharmacokinetic profiles, thus increasing medicinal chemists' interest in recent years. Using the drug repurposing strategy, a BRD4-specific score based virtual screening campaign on an in-house drug library was conducted followed by the ALPHA screen assay test. Nitroxoline, an FDA-approved antibiotic, was identified to effectively disrupt the interaction between the first bromodomain of BRD4 (bromodomain-containing protein 4) and acetylated H4 peptide with IC50 of 0.98 µM. Nitroxoline inhibited all BET family members with good selectivity against non-BET bromodomain-containing proteins, thus it is defined as a selective BET inhibitor. Based on the crystal structure of the nitroxoline-BRD4_BD1 complex, the mechanism of action as well as BET specificity of nitroxoline were determined. Since the anticancer activity of nitroxoline against MLL leukemia, one of the BET related diseases, has not been studied before, we tested whether nitroxoline might serve as a potential repurposing drug candidate for MLL leukemia. Nitroxoline effectively inhibited the proliferation of MLL leukemia cells by inducing cell cycle arrest and apoptosis. The profound efficacy is, at least in part, due to the inhibition of BET and downregulation of target gene transcription. Our discovery of nitroxoline as a BET inhibitor suggests potential application of nitroxoline and its derivatives for clinical translation in BET family related diseases.