Explore the vast range of titles available.

Background: Chemoresistance represented one of the challenges in the treatment of advanced gastric cancer (GC). Curcumol (CUR) was found to have a certain sensitizing effect on chemoresistance, although the mechanism was not yet fully understood. Purpose: To clarify the ability of CUR to intervene in the sensitivity of GC cells to Cisplatin (CDDP) by regulating the induction of ferroptosis through the P62/KEAP1/NRF2 pathway. Methods: An in vitro resistant cell line was established and treated with CUR for intervention. The synergy was evaluated using synergyfinder3.0 software. The impact of the combined use of CUR and CDDP on the proliferation, migration, and invasion of resistant GC cells was determined. The effect of CUR on ferroptosis in resistant GC cell lines was evaluated by measuring changes in reactive oxygen species (ROS) levels, malondialdehyde (MDA) levels, iron ion levels, and the ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG). Western blotting was used to verify the expression changes of the ferroptosis-related indicator GPX4 and the differential expression of the antioxidant-related pathway P62/KEAP1/NRF2, validating the mechanism by which CUR induces ferroptosis in resistant GC cells. In vivo validation was performed using a xenograft mouse model. Results: The evaluation by synergy3.0 revealed a synergistic effect between CUR and CDDP. After treatment with CUR and CDDP, resistant GC cell lines exhibited reduced proliferation, migration, and invasion capabilities. Furthermore, the resistant GC cell lines underwent ferroptosis, with significant changes observed in ferroptosis-related indicators such as ROS, MDA, iron ions, and GSH/GSSG. The ferroptosis-related targets Glutathione Peroxidase 4 (GPX4) and the antioxidant pathway P62/KEAP1/NRF2 signaling pathway also showed significant changes. In in vivo validation, the combination of CUR and CDDP inhibited the growth of subcutaneous tumors and was found to be associated with the inhibition of subcutaneous xenografts and the GPX4 and P62/KEAP1/NRF2 signaling pathways. Conclusion: This study first revealed that CUR enhanced the sensitivity of cisplatin-resistant GC cells to CDDP by inducing ferroptosis. The combination of CUR and CDDP induces ferroptosis in cisplatin-resistant GC through the P62/KEAP1/NRF2 pathway.

Activation of the NRF2 pathway through gain-of-function mutations or loss-of-function of its suppressor KEAP1 is a frequent finding in lung cancer. NRF2 activation has been reported to alter the tumor microenvironment. Here, we demonstrated that NRF2 alters tryptophan metabolism through the kynurenine pathway that is associated with a tumor-promoting, immune suppressed microenvironment. Specifically, proteomic profiles of 47 lung adenocarcinoma (LUAD) cell lines (11 KEAP1 mutant and 36 KEAP1 wild-type) revealed the tryptophan-kynurenine enzyme kynureninase (KYNU) as a top overexpressed protein associated with activated NRF2. The siRNA-mediated knockdown of NFE2L2, the gene encoding for NRF2, or activation of the NRF2 pathway through siRNA-mediated knockdown of KEAP1 or via chemical induction with the NRF2-activator CDDO-Me confirmed that NRF2 is a regulator of KYNU expression in LUAD. Metabolomic analyses confirmed KYNU to be enzymatically functional. Analysis of multiple independent gene expression datasets of LUAD, as well as a LUAD tumor microarray demonstrated that elevated KYNU was associated with immunosuppression, including potent induction of T-regulatory cells, increased levels of PD1 and PD-L1, and resulted in poorer survival. Our findings indicate a novel mechanism of NRF2 tumoral immunosuppression through upregulation of KYNU.

BackgroundCitrulline post-translational modification of proteins is mediated by protein arginine deiminase (PADI) family members and has been associated with autoimmune diseases. The role of PADI-citrullinome in immune response in cancer has not been evaluated. We hypothesized that PADI-mediated citrullinome is a source of neoantigens in cancer that induces immune response.MethodsProtein expression of PADI family members was evaluated in 196 cancer cell lines by means of indepth proteomic profiling. Gene expression was assessed using messenger RNA data sets from The Cancer Genome Atlas. Immunohistochemical analysis of PADI2 and peptidyl-citrulline was performed using breast cancer tissue sections. Citrullinated 12–34-mer peptides in the putative Major Histocompatibility Complex-II (MHC-II) binding range were profiled in breast cancer cell lines to investigate the relationship between protein citrullination and antigen presentation. We further evaluated immunoglobulin-bound citrullinome by mass spectrometry using 156 patients with breast cancer and 113 cancer-free controls.ResultsProteomic and gene expression analyses revealed PADI2 to be highly expressed in several cancer types including breast cancer. Immunohistochemical analysis of 422 breast tumor tissues revealed increased expression of PADI2 in ER− tumors (p<0.0001); PADI2 protein expression was positively correlated (p<0.0001) with peptidyl-citrulline staining. PADI2 expression exhibited strong positive correlations with a B cell immune signature and with MHC-II-bound citrullinated peptides. Increased circulating citrullinated antigen–antibody complexes occurred among newly diagnosed breast cancer cases relative to controls (p=0.0012).ConclusionsAn immune response associated with citrullinome is a rich source of neoantigens in breast cancer with a potential for diagnostic and therapeutic applications.

Mediator is a multisubunit transcriptional co-regulator that is involved in the regulation of an array of processes including plant metabolism. The pathways regulated by Mediator-dependent processes include those for the synthesis of phenylpropanoids (MED5), cellulose (MED16), lipids (MED15 and CDK8), and the regulation of iron homeostasis (MED16 and MED25). Traditional genetic and biochemical approaches laid the foundation for our understanding of Mediator function, but recent transcriptomic and metabolomic studies have provided deeper insights into how specific subunits cooperate in the regulation of plant metabolism. In this review, we highlight recent developments in the investigation of Mediator and plant metabolism, with particular emphasis on the large-scale biology studies of med mutants.

Mediator is a multisubunit transcriptional co-regulator that is involved in the regulation of an array of processes including plant metabolism. The pathways regulated by Mediator-dependent processes include those for the synthesis of phenylpropanoids (MED5), cellulose (MED16), lipids (MED15 and CDK8), and the regulation of iron homeostasis (MED16 and MED25). Traditional genetic and biochemical approaches laid the foundation for our understanding of Mediator function, but recent transcriptomic and metabolomic studies have provided deeper insights into how specific subunits cooperate in the regulation of plant metabolism. In this review, we highlight recent developments in the investigation of Mediator and plant metabolism, with particular emphasis on the large-scale biology studies of med mutants.

Abstract Mediator is a multisubunit transcriptional co-regulator that is involved in the regulation of an array of processes including plant metabolism. The pathways regulated by Mediator-dependent processes include those for the synthesis of phenylpropanoids (MED5), cellulose (MED16), lipids (MED15 and CDK8), and the regulation of iron homeostasis (MED16 and MED25). Traditional genetic and biochemical approaches laid the foundation for our understanding of Mediator function, but recent transcriptomic and metabolomic studies have provided deeper insights into how specific subunits cooperate in the regulation of plant metabolism. In this review, we highlight recent developments in the investigation of Mediator and plant metabolism, with particular emphasis on the large-scale biology studies of med mutants.

The Mediator complex functions as a hub for transcriptional regulation. MED5, an Arabidopsis Mediator tail subunit, is required for maintaining phenylpropanoid homeostasis. A semidominant mutation (ref4-3) that causes a single amino acid substitution in MED5b functions as a strong suppressor of the pathway, leading to decreased soluble phenylpropanoid accumulation, reduced lignin content and dwarfism. By contrast, loss of MED5 results in increased concentrations of phenylpropanoids. We used a reverse genetic approach to identify suppressors of ref4-3 and found that ref4-3 requires CDK8, a kinase module subunit of Mediator, to repress plant growth. The genetic interaction between MED5 and CDK8 was further characterized using mRNA-sequencing (RNA-seq) and metabolite analysis. Growth inhibition and suppression of phenylpropanoid metabolism can be genetically separated in ref4-3 by elimination of CDK8 kinase activity; however, the stunted growth of ref4-3 is not dependent on the phosphorylation event introduced by the G383S mutation. In addition, rather than perturbation of lignin biosynthesis, misregulation of DJC66, a gene encoding a DNAJ protein, is involved in the dwarfism of the med5 mutants. Together, our study reveals genetic interactions between Mediator tail and kinase module subunits and enhances our understanding of dwarfing in phenylpropanoid pathway mutants.

The Mediator complex functions as a hub for transcriptional regulation. MED 5, an Arabidopsis Mediator tail subunit, is required for maintaining phenylpropanoid homeostasis. A semidominant mutation ( ref4‐3 ) that causes a single amino acid substitution in MED 5b functions as a strong suppressor of the pathway, leading to decreased soluble phenylpropanoid accumulation, reduced lignin content and dwarfism. By contrast, loss of MED 5 results in increased concentrations of phenylpropanoids. We used a reverse genetic approach to identify suppressors of ref4‐3 and found that ref4‐3 requires CDK 8, a kinase module subunit of Mediator, to repress plant growth. The genetic interaction between MED 5 and CDK 8 was further characterized using m RNA ‐sequencing ( RNA ‐seq) and metabolite analysis. Growth inhibition and suppression of phenylpropanoid metabolism can be genetically separated in ref4‐3 by elimination of CDK 8 kinase activity; however, the stunted growth of ref4‐3 is not dependent on the phosphorylation event introduced by the G383S mutation. In addition, rather than perturbation of lignin biosynthesis, misregulation of DJC 66 , a gene encoding a DNAJ protein, is involved in the dwarfism of the med5 mutants. Together, our study reveals genetic interactions between Mediator tail and kinase module subunits and enhances our understanding of dwarfing in phenylpropanoid pathway mutants.

The Mediator complex functions as a hub for transcriptional regulation. MED5, an Arabidopsis Mediator tail subunit, is required for maintaining phenylpropanoid homeostasis. A semidominant mutation (ref4-3) that causes a single amino acid substitution in MED5b functions as a strong suppressor of the pathway, leading to decreased soluble phenylpropanoid accumulation, reduced lignin content and dwarfism. By contrast, loss of MED5 results in increased concentrations of phenylpropanoids. We used a reverse genetic approach to identify suppressors of ref4-3 and found that ref4-3 requires CDK8, a kinase module subunit of Mediator, to repress plant growth. The genetic interaction between MED5 and CDK8 was further characterized using mRNA-sequencing (RNA-seq) and metabolite analysis. Growth inhibition and suppression of phenylpropanoid metabolism can be genetically separated in ref4-3 by elimination of CDK8 kinase activity; however, the stunted growth of ref4-3 is not dependent on the phosphorylation event introduced by the G383S mutation. In addition, rather than perturbation of lignin biosynthesis, misregulation of DJC66, a gene encoding a DNAJ protein, is involved in the dwarfism of the med5 mutants. Together, our study reveals genetic interactions between Mediator tail and kinase module subunits and enhances our understanding of dwarfing in phenylpropanoid pathway mutants.

The Mediator (Med) complex comprises about 30 subunits and is a transcriptional coregulator in eukaryotic systems. The core Mediator complex, consisting of the head, middle and tail modules, functions as a bridge between transcription factors and basal transcription machinery, whereas the CDK8 kinase module can attenuate Mediator’s ability to function as either a coactivator or co-repressor. Many Arabidopsis Mediator subunit has been functionally characterized, which reveals critical roles of Mediator in many aspects of plant growth and development, responses to biotic and abiotic stimuli, and metabolic homeostasis. Traditional genetic and biochemical approaches laid the foundation for our understanding of Mediator function, but recent transcriptomic and metabolomic studies have provided deeper insights into how specific subunits cooperate in the regulation of plant metabolism. In Chapter 1, we highlight recent developments in the investigation of Mediator and plant metabolism, with emphasis on the large-scale biology studies of med mutants.We previously found that MED5, an Arabidopsis Mediator tail subunit, is required for maintaining phenylpropanoid homeostasis. A semi-dominant mutation (reduced epidermal fluorescence 4-3, ref4-3) that causes a single amino acid substitution in MED5b functions as a strong suppressor of the pathway, leading to decreased soluble phenylpropanoid accumulation, reduced lignin content and dwarfism. In contrast, loss of MED5a and MED5b (med5) results in increased levels of phenylpropanoids. In Chapter 2, we present our finding that ref4-3 requires CDK8, a Mediator kinase module subunit, to repress plant growth even though the repression of phenylpropanoid metabolism in ref4-3 is CDK8-independent. Transcriptome profiling revealed that salicylic acid (SA) biosynthesis genes are up-regulated in a CDK8-dependent manner in ref4- 3, resulting in hyper-accumulation of SA and up-regulation of SA response genes. Both growth repression and hyper-accumulation of SA in ref4-3 require CDK8 with intact kinase activity, but these SA phenotypes are not connected with dwarfing. In contrast, mRNA-sequencing (RNA-seq) analysis revealed the up-regulation of a DNA J protein-encoding gene in ref4-3, the elimination of which partially suppresses dwarfing. Together, our study reveals genetic interactions between Mediator tail and kinase module subunits and enhances our understanding of dwarfing in phenylpropanoid pathway mutants.In Chapter 3, we characterize other phenotypes of med5 and ref4-3, and find that in addition to the up-regulated phenylpropanoid metabolism, med5 show other interesting phenotypes including hypocotyl and petiole elongation as well as accelerated flowering, all of which are known collectively as the shade avoidance syndrome (SAS), suggesting that MED5 antagonize shade avoidance in wild-type plants. In contrast, the constitutive ref4-3 mutant protein inhibits the process, and the stunted growth of ref4-3 mutants is substantially alleviated by the light treatment that triggers SAS. Moreover, ref4-3 mimics the loss-of-function med5 mutants in maintaining abscisic acid (ABA) levels under both normal and drought growth conditions. The phenotypic characterization of med5 mutants extend our understanding of the role of Mediator in SAS and ABA signaling, providing further insight into the physiological and metabolic responses that require MED5.