Oncogene

Despite continuous progress in diagnosis and therapy, breast carcinoma (BC) remains a major health problem. Triple-negative (Estrogen Receptor-/Progesterone Receptor-/HER2-) breast cancer (TNBC) is the most aggressive subtype due to its high metastatic potential and resistance to chemotherapy. The Y-box binding protein 1 (YB-1) transcription factor, a protein present in both cytoplasm and nucleus, is a driver of TNBC malignancy as it stimulates its cancer stem cell phenotype and disrupts cell cycle progression. Here, we hypothesized that YB-1-containing sEVs deliver YB-1 to the nuclear compartment of recipient cancer cells and play a major role in the activation of the metastatic process. We found a selective enrichment of YB-1 in sEVs from MDA and 4T1 cells, with [~]65% and 50% of all sEVs positive for YB-1 by d-STORM. Administration of sEVs from wild-type MDA and 4T1 to their YB-1 knockout counterparts resulted in nuclear translocation of sEV-associated YB-1 and increased tumorsphere formation. Pharmacological blockade of the nuclear transport machinery based on the inhibition of the formation of the "VOR" complex (VAP-A-ORP3-Rab7) by PRR851 impaired both nuclear translocation and the YB-1-induced increase in tumorsphere formation. YB-1 phosphorylation at S102 was required for nuclear localization. In fact, loss of YB-1 phosphorylation inhibited tumorsphere growth and stemness of cancer cells and YB-1-positive sEVs restored the oncogenic behavior of cancer cells expressing phospho-mutant YB-1. Moreover, PRR851 inhibited the nuclear translocation of the phosphorylated form of YB-1 and the oncogenic behavior of the TNBC cells. These data support the conclusion that the nuclear translocation of sEV-associated phosphorylated YB-1 is an important factor in the malignant behavior of TNBC and a potential therapeutic target.

Long non-coding RNAs (lncRNAs) have attracted increasing interest because of their roles as modulators of tumor progression, acting either as oncogenic drivers or tumor suppressors, depending on the cellular context. LINC01133 has been implicated in regulation of multiple tumor-related mechanisms; however, its role in breast cancer, particularly in the triple-negative subtype, remains poorly characterized. In this study, we investigated the impact of LINC01133 depletion on malignant phenotypes and on the expression of migration- and invasion-associated genes using the Hs578T triple-negative breast cancer (TNBC) cell line, through comparative analyses of parental, control, and LINC01133-knockout cell lines, namely Hs578T_wt, Hs578T_ctr, and Hs578T_ko. Functional characterization included morphological analysis, growth assays, anchorage-independent colony formation, migration, invasion, and quantitative biomolecular experiments. Depletion of LINC01133 led to reduction of cell diameter, a significant increase in colony-forming capacity, and marked enhancement of migratory and invasive potential. At the molecular level, LINC01133 loss induced the expression of genes associated with extracellular matrix remodeling and cellular plasticity, including fibronectin, vimentin, integrins, FOXC1, and TWIST1, concomitant with reduced expression of ZEB1, TWIST2, and N-cadherin. Collectively, these data indicate that LINC01133 acts as a potential fine regulator of in vitro migration and invasion processes in TNBC, with its expression favoring a more asymptomatic mode of tumor progression, whereas its loss markedly enhances tumor malignancy.

Api5 is elevated in a number of cancers and is associated with many hallmarks of cancer, including resistance to apoptosis, immune escape, stemness, chemotherapy resistance, high proliferation, and cell-cycle dysregulation. In this study, we identified the DNA and chromatin-binding activities of Api5 in tumorigenic cells, as well as its association with genomic instability and chemotherapy resistance. Knockdown of Api5 resulted in reduced nuclear volume, DNA content, and chromosome number, and increased sensitivity to DNA damage. The survival of Api5-knockdown cells decreased following UV and cisplatin treatments due to the accumulation of damaged DNA and inefficient nucleotide excision repair. Interestingly, Api5 knockdown cells also exhibited low pChk1 levels following UV damage. Further, we confirmed the chemotherapy resistance phenotype in cancers with elevated Api5 levels, demonstrating that xenograft tumours with Api5 knockdown responded better to cisplatin, with significant tumour regression. SummaryApoptosis inhibitor 5 (Api5) contributes to chemotherapy resistance by conferring a survival advantage and promoting efficient DNA repair following genotoxic stress through regulation of Chk1 activation.

Inflammatory breast cancer (IBC) is an aggressive breast cancer subtype characterized by tumor emboli, lymphovascular invasion (LVI), and early dissemination. Herein, we establish adaptive stress response (ASR) as a biologic feature linking stress adaptation to tumor emboli survival, lymphatic dissemination, therapeutic response, and disparities. Using a previously defined 226 ASR-related genes, complementary preclinical models of tumor emboli and lymphatic circulating cell clusters, and independent patient cohorts, we identified ASR genes enriched for XIAP-NF{kappa}B, oxidative stress response, inflammatory, and immune pathways. CXCL8 emerged as one of the most highly upregulated transcripts in tumor emboli and was shared across both models; however, CXCL8, IL6, and PTGS2 were downregulated in lymphatic circulating cell clusters and LVI-positive triple-negative IBC patients, suggesting dynamic remodeling of inflammatory signaling during dissemination. CYP4B1 was associated with ER status, LVI, and therapeutic response across multiple cohorts, implicating metabolic stress adaptation in dissemination. IL6 and PTGS2 were elevated in self-reported Black patients with triple-negative IBC compared to White patients. Pharmacologic inhibition of XIAP-NF{kappa}B and oxidative stress pathways suppressed tumor emboli formation. Collectively, these findings identify ASR signaling as a framework linking tumor emboli survival, dissemination, and therapeutic vulnerability in IBC.

Metastatic prostate cancer (PCa) continues to be a major cause of death in males, despite advances in treatment. Most treatment focuses on targeting the Androgen Receptor (AR), the main oncogene responsible for driving most prostate tumors. Despite these therapies targeting AR, the majority of patients still succumb to AR-driven disease. Therefore, there is a critical need for understanding how AR functions to promote prostate cancer growth and identify alternative therapeutic targets in AR-driven PCa. One avenue garnering attention is targeting epigenetic regulators that promote AR-activity; however, the importance of epitranscriptomic regulators, like those that modify mRNAs, is not well understood. Here, we identify a new role for the key catalytic subunit of the RNA N6-methyladenosine (m6A) transferase complex, METTL3, as an AR-coregulator. METTL3 is overexpressed in prostate tumors compared to normal tissue, and METTL3 protein is elevated in AR-expressing cell lines. Depletion of METTL3 significantly reduces proliferation of cancer cells and has no effect on the growth of non-transformed prostate epithelial cells, despite decreasing global m6A levels on mRNA. The catalytic activity of METTL3 is dispensable for the growth of both non-transformed and PCa cell lines, as pharmacologic inhibition of METTL3 does not inhibit proliferation, despite the reduction of global m6A on mRNA. Overexpression of both wild-type and catalytically inactive METTL3 mutants enhances cell viability and rescues cells in which METTL3 is knocked down. Finally, we report on direct interaction between AR and METTL3, their co-localization on chromatin, and reduced AR-cistromic occupancy within cells with METTL3 knockdown. Together, these findings identify a non-enzymatic role for METTL3 in supporting AR-driven transcriptional programs and PCa proliferation.

Deregulation of sphingolipid (SL) metabolism is well-established across many cancers, yet the underlying mechanisms that drive changes in SLs are poorly understood. We previously identified dihydroceramide desaturase 1 (DES1) as a downstream target of HER2 and implicated DES1 as a driver of anchorage-independent survival in breast cancer. In this study, we expand on these results to establish the oncogenic PI3K pathway as a driver of post-translational DES1 activity following cell detachment from the extracellular matrix. PI3K activation of DES1 required glucose uptake and metabolism through both glycolysis and the pentose phosphate pathway. However, it did not require glucose flux into the TCA cycle and was independent of antioxidant capacity of the cell. Moreover, Instead, results identify GAPDH - a point of convergence between glycolysis and PPP - as important for oncogene-driven DES1 activity. Overall, this study defines a novel pathway of DES1 regulation and establishes DES1 as a point of crosstalk between glucose and SL metabolic pathways.

TAOK3 is a lesser-studied MAPK family serine/threonine kinase our group has shown to be targeted by HPV integration, suggesting a potential role in driving invasive cervical cancer (ICC). Here, we profiled TAOK3 expression in patient tumors, metastases, and cervical cancer models and localized TAOK3 within a tumor epithelial subpopulation by integrating two single-cell RNA-seq datasets. Functional consequences of TAOK3 loss were assessed with siRNA and CRISPRi in cell lines and 3D spheroids. In vivo effects were evaluated in intracervical xenografts with species-specific RNA-seq to resolve tumor versus microenvironmental responses. TAOK3 mRNA/protein were elevated in primary and metastatic ICC and primarily localized to a keratin-positive epithelial subset (T3epi) enriched for cadherin/S100 binding, vesicle/endocytic pathways, and leading-edge programs. TAOK3 silencing reprogrammed transcriptomes and proteomes toward reduced WNT/cell-cycle and motility signaling, altered endocytosis and cytoskeleton organization, and reshaped phospho-networks linked to chromatin remodeling and ERBB2-ERBB3/cytoskeletal kinase activity. Functionally, TAOK3 inhibition prolonged G2/M, suppressed invasion, and enhanced sensitivity to low dose paclitaxel. Prolonged inactivation induced methuosis-like cell death with extracellular ATP release. In xenografts, TAOK3 knockdown reduced tumor burden, downregulated KRT14--a leader cell marker--within the human tumor compartment, and enriched microenvironmental pathways for immune activation, with a specific decrease in CD206+ M2 macrophages. TAOK3 delineates an invasion-competent epithelial state in ICC and coordinates cell-cycle control, cytoskeleton-membrane dynamics, and tumor-immune crosstalk. Genetic or pharmacologic TAOK3 inhibition constrains tumor growth, potentiates paclitaxel, and remodels the microenvironment toward anti-tumor immunity, supporting TAOK3 as a potential therapeutic target and biomarker in ICC. Statement of SignificanceTAOK3 marks an invasion-competent epithelial subpopulation in cervical cancer. TAOK3 inhibition slows tumor growth, enhances chemoresponse, and reduces M2 macrophages, revealing TAOK3 as a potential therapeutic target and biomarker for patient stratification.

IntroductionThe RAS(ON) multi-selective daraxonrasib (RMC-6236) inhibitor is effective in patients with NSCLC KRAS mutant cancers. Tolerance to daraxonrasib invariably develops by mechanisms that remain unclear. There is no known involvement of the M1C oncogenic protein in daraxonrasib resistance. MethodsNSCLC H358 KRAS(G12C), H2122 KRAS(G12C) and patient derived MGH1112 KRAS(G12C) cells with acquired daraxonrasib resistance were investigated for M1C dependence in studies of SHP2, STAT1/3 and NF-KB activation, clonogenicity, and self-renewal capacity. ResultsWe demonstrate that M1C is induced as a protective response in NSCLC KRAS(G12C) mutant cells treated with daraxonrasib. We report that M1C forms novel cell membrane-associated biomolecular condensates with the SHP2 protein tyrosine phosphatase in driving daraxonrasib resistance. M1C integrates SHP2 activation with induction of (i) oncostatin-m/gp130/STAT3 signaling, and (ii) the NF-{kappa}B-mediated epithelial-mesenchymal transition (EMT) pathway. The functional significance of this M1C-driven pathway is supported by the demonstration that targeting STAT3 and NF-{kappa}B reverses daraxonrasib resistance. Consistent with M1C dependence, we also show that targeting M1C is effective against daraxonrasib-resistant NSCLC KRAS mutant cell line and tumor models. In contrast, M1C drives sotorasib resistance by STAT1-mediated inflammatory signaling, demonstrating that M1C confers resistance to KRAS(G12C)-selective and RAS(ON) tri-complex inhibitors by noncongruent mechanisms. ConclusionsThese findings demonstrate that M1C is required for daraxonrasib tolerance and is a potential target for the treatment of patients with NSCLC KRAS(G12C) mutant tumors refractory to this agent.

Osteosarcoma (OS) and Ewing sarcoma (EWS) are the most common malignant bone tumors in children and adolescents, with survival rates around 25% in metastatic disease and few advances in treatment in decades. High DDX3 expression has been reported across various sarcoma subtypes. Depending on the context, DDX3 appears to have opposing roles in regulating the tumor immune microenvironment. Within macrophages, DDX3 promotes inflammatory cytokine expression and supports immune cell function. In contrast, in tumor cells DDX3 suppresses a pro-inflammatory state by unwinding dsRNAs, preventing a Type I interferon response. We show that inhibiting DDX3 with RK-33 leads to dsRNA accumulation, inducing a Type I interferon response and broader inflammatory gene expression changes across multiple sarcoma models, shifting macrophage polarization toward a pro-inflammatory M1-like phenotype. To evaluate whether this innate immune microenvironmental remodeling could translate into clinical benefit, we assessed the therapeutic efficacy of RK-33 alone or in combination with mifamurtide, an immunostimulant, in immune competent mouse models of osteosarcoma, with metastatic burden as the primary outcome. We found that in the absence of MYC over-expression, the combination treatment significantly reduced metastatic spread. These findings support targeting DDX3 as a novel innate immune based therapeutic strategy and highlight that the tumors molecular landscape critically influences therapeutic responsiveness.

SMAD4 is a central transcriptional effector of the TGF-{beta} signaling pathway and a frequently inactivated tumor suppressor gene in various cancers. Missense mutations in its MH2 domain are among the most prevalent somatic alterations in colorectal cancer (CRC). These mutations are associated with disease progression and poor prognosis, yet their precise mechanistic consequences have remained incompletely characterized. Here, we show that CRC-derived SMAD4 MH2 hotspot mutations (D351H, S357P, R361C, and R361H) selectively impair co-activator recruitment without disrupting chromatin occupancy. RNA-seq profiling demonstrated broad suppression of TGF-{beta} target gene expression across all mutants. Notably, the mutations confer distinct degrees of TGF-{beta} pathway unresponsiveness: R361H is completely refractory to TGF-{beta} stimulation, whereas R361C and S357P retain partial transcriptional responsiveness suggesting allele-specific differences in the severity of co-activator interface disruption. Genome-wide chromatin binding analysis by greenCUT&RUN confirmed that all mutants maintain wild-type-like genomic occupancy, as expected given that the MH1 DNA-binding domain is intact in each case. Proximity-dependent biotinylation mass spectrometry in COLO205 cells revealed that all four mutants exhibit markedly reduced interactions with the CREBBP/EP300 histone acetyltransferase complex and BRD4 relative to wild-type SMAD4 identifying disrupted co-activator engagement. Collectively, our findings establish that SMAD4 MH2 mutations impair TGF-{beta}-induced transcription by selectively reducing CREBBP/EP300 recruitment, which provides a molecular mechanism for the loss-of-function SMAD4 phenotype in CRC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=154 SRC="FIGDIR/small/735541v1_ufig1.gif" ALT="Figure 1000"> View larger version (24K): org.highwire.dtl.DTLVardef@14f542eorg.highwire.dtl.DTLVardef@11fd220org.highwire.dtl.DTLVardef@1c3aa1org.highwire.dtl.DTLVardef@14d5a8e_HPS_FORMAT_FIGEXP M_FIG C_FIG

Melanoma, one of the most metastatic and multidrug resistant cancer, is the first leading cause of death from skin cancer. This complex disease requires identification of additional cooperating events that contribute to progression, invasion and metastasis to reinforce therapeutics. RhoGTPases play key roles in cancer development and metastasis. Rhophilin-2 (RHPN2), a Rho effector, is amplified in various human cancers and its role in melanoma remains unexplored. Here, we combined knock-down experiments in human melanoma cells, with knock-out and overexpression experiments in zebrafish to uncover the roles of RHPN2 in melanoma development. We show that in human melanoma cells RHPN2 contributes to growth, and to clonogenic, migratory and invasive properties of the cells. Using NRASQ61L and BRAFV600E zebrafish models, we provide the first in vivo evidence that Rhpn2 promotes melanoma onset and development. Histological analysis of the Rhpn2 deficient tumors showed decreased cellular density and absence of primary cilia structures at the invasive tumor/stroma borders. Transcriptomic profiling of the Rhpn2-KO melanoma revealed increased expression of the IFN1-responsive genes and modulation of genes involved in lipid metabolism and cilia function. Together these findings position RHPN2 as a modulator of melanoma, offering new perspectives in considering it as a target to impair the development of the tumor.

Structural AbstractO_ST_ABSBackgroundC_ST_ABSTriple-negative breast cancer (TNBC) represents a major clinical challenge due to its aggressiveness, heterogeneity and limited availability of effective targeted therapy. We investigated whether LRP-1, a multifunctional cell-surface endocytic and signaling receptor, contributes to TNBC progression. MethodsUsing CRISPR-Cas9, LRP-1-deficient murine 4T1 and human HS578-T TNBC cells were used. Functional consequences were assessed through migration, invasion, and 3D spheroid assays, imaging of focal adhesions and actin organization, atomic force microscopy, and plasmin activity assays. Global molecular reprogramming was analyzed by label-free quantitative proteomics and secretomics. LRP-1-deficient or proficient 4T1 cells were implanted orthotopically in immunocompetent mice; tumor progression was monitored longitudinally while peritumoral collagen architecture and immune microenvironment composition were characterized by second harmonic generation imaging and immunohistochemistry. ResultsWe show that LRP-1 loss reduces TNBC aggressiveness, as reflected by decreased migration and invasive capacity, reduced spheroid evasion, and significant morphological changes in focal adhesion and actin structure. LRP-1-deficient cells became stiffer and showed lower LOXL-4 levels, while pericellular proteolytic activity remained unchanged, suggesting other proteases mechanism. Multi-omic analysis revealed alterations in extracellular matrix (ECM), epithelial-mesenchymal transition, and inflammatory pathways. In vivo, LRP-1-deficiency reduced tumor progression and peritumoral collagen deposition, while increasing CD8+ T and Natural Killer cell infiltration, together with a cytokine profiling compatible with a more immune-permissive microenvironment. ConclusionsLRP-1 act as a key contributor in TNBC progression through matrix remodeling, mechano-adaptation, and immune exclusion. Positioning it as a candidate biomarker for TNBC patients who are likely to benefit from stroma-targeting therapies. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/732906v2_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@1b595c2org.highwire.dtl.DTLVardef@7b208aorg.highwire.dtl.DTLVardef@1956e54org.highwire.dtl.DTLVardef@17e55d0_HPS_FORMAT_FIGEXP M_FIG C_FIG

Bone metastasis remains a major clinical challenge in advanced breast cancer. Downregulation of type I interferon signalling, a critical immunomodulatory pathway in anti-cancer immunity and disease progression, is a defining feature of this process. Here, we utilised an IFN-reporter system to perform unbiased epigenetic compound screens to identify agents that could restore type I IFN signalling. This screen identified Decitabine, a DNA hypomethylating agent, that enhanced tumor immunogenicity across a broad range of mouse and human breast cancer cell lines, including bone-derived lines. Mechanistically, suppression of interferon-stimulated genes is highly correlated with elevated DNMT1 expression in bone metastasis compared with primary tumor, in both mouse models and matched human samples. Decitabine treatment was sufficient to reactivate interferon stimulated genes in bone-derived 4T1.2 cell lines via hypomethylation of type I interferon pathway gene promoter regions. Correspondingly, in the syngeneic 4T1.2 metastasis mouse model, Decitabine treatment conferred a survival benefit and reduced metastatic potential, particularly in bone. Our findings reveal DNA methylation as a key regulator of the transcriptional programs underlying bone metastasis, providing mechanistic insight into how Decitabine reactivates type I interferon signalling and reduces metastatic potential, highlighting epigenetic reprogramming as a promising approach for targeting metastatic breast cancer. STATEMENT OF SIGNIFICANCEBone metastasis remains a major clinical challenge and a key mechanism of progression to bone is the suppression of tumor-inherent type I interferon signalling. We identified Decitabine, a DNA hypomethylating agent, as a promising therapeutic agent to enhance tumor immunogenicity across a broad range of breast cancer cell lines, including bone metastasis-derived lines. Our findings support DNA methylation as a key regulator of transcriptional programs associated with bone metastatic progression, and provide mechanistic insight into how Decitabine reactivates type I interferon signalling and reduces metastatic potential in vivo. These results highlight epigenetic reprogramming as a promising approach for targeting metastatic breast cancer.

Intracellular iron homeostasis is increasingly recognized as a regulator of cancer cell behavior, but how iron distribution influences extracellular matrix (ECM) organization and invasion remains poorly understood. Here, we show that loss of divalent metal transporter 1 (DMT1/SLC11A2) disrupts intracellular iron homeostasis and promotes cancer cell invasion through an iron-ER-ECM axis. In MDA-MB-231 cells, DMT1 knockout (KO) reduced total iron content but increased the labile iron pool (LIP) in both 2D and 3D culture models, indicating altered intracellular iron distribution. Across transcriptomic and phenotypic readouts, DMT1-dependent effects were more evident in 3D than in 2D models, with DMT1 KO inducing endoplasmic reticulum (ER) stress and impaired collagen/ECM organization. Functionally, the DMT1-loss phenotype was marked by reduced 2D motility, whereas in 3D spheroid models DMT1 KO cells displayed enhanced invasive outgrowth in both Matrigel and collagen matrices. Iron chelation further modulated this phenotype in a DMT1-dependent manner. Pharmacologic induction of ER stress phenocopied the loose spheroid architecture and invasive behavior, supporting ER stress as a mechanistic link between altered iron handling and ECM destabilization. Together, these findings identify intracellular iron distribution, rather than total iron abundance alone, as a determinant of ECM integrity and context-dependent cancer cell invasion. Significance StatementOur study identifies an iron-ER-ECM axis through which intracellular iron homeostasis regulates cancer cell invasion. Total cellular iron content alone is insufficient to predict invasive behavior without considering how iron is distributed within the cell. By preserving intracellular iron homeostasis and ER function, DMT1 supports collagen synthesis and maintains ECM integrity. In contrast, DMT1 loss disrupts these processes, promoting formation of loosely aggregated spheroids and enhanced invasion in 3D tumor models despite reduced total iron levels. These findings challenge the assumption that lowering bulk iron uniformly suppresses invasive phenotypes and instead highlight intracellular iron trafficking as a potential therapeutic target for limiting cancer cell invasion.

WNT11, a non-canonical WNT ligand, plays well-defined roles in development and tissue architecture; however, its function in cancer remains ambiguous. Here, we characterize WNT11 as a context-dependent suppressor of cancer stemness, invasion, and in vivo tumor formation in human epithelial cancer models. We show that WNT11 upregulation reduces the expression of stemness-promoting genes, suppresses epithelial-to-mesenchymal transition, and inhibits sphere formation and tumor growth. Conversely, downregulation of WNT11 enhances these aggressive malignant properties of cancer cells. Mechanistically, we found that the ability of WNT11 to inhibit RAC1 GTPase activation is essential for its regulation of invasion and self-renewal. In cells unresponsive to WNT11, the connectivity between WNT11 and RAC1 activity is disengaged. Direct manipulation of RAC1 activity in these cells recapitulates the phenotype and molecular signature of WNT11-responsive cells, establishing RAC1 as a critical effector of WNT11-mediated tumor suppression. Taken together, these findings identify the cellular context in which WNT11 suppresses RAC1 activation as a key determinant of its anti-tumor effects and provide a mechanistic framework for understanding the diverse, and sometimes opposing, roles of WNT11 reported in cancer.

Neuroendocrine prostate cancer (NEPC) persists in a profoundly hypoxic microenvironment, yet the mechanisms enabling tumor adaptation to this metabolically challenging niche remain undefined. Here, we identify the lipid kinase PIKfyve as overexpressed in NEPC, functioning as a central node in a stress-lipid kinase axis that drives adaptation to persistent endoplasmic reticulum (ER) stress. Mechanistically, NEPC requires PIKfyve-mediated lysosomal degradation and lipid recycling to maintain metabolic homeostasis under hypoxia. PIKfyve inhibition disrupts lysosomal function, leading to ER stress accumulation and activation of a compensatory, sterol regulatory element-binding protein (SREBP)-dependent de novo lipogenesis program essential for NEPC survival. This stress-lipid axis creates a synthetic vulnerability between PIKfyve and fatty acid synthase (FASN), where dual inhibition synergistically amplifies ER stress, triggers the terminal unfolded protein response, and induces tumor cell death. These findings reveal a metabolic adaptation in NEPC and provide preclinical evidence that co-targeting PIKfyve and FASN can overcome hypoxia-associated stress adaptation.

Cytotoxic T lymphocytes (CTLs) play a central role in antitumor immunity; however, metabolic reprogramming within the tumor microenvironment often compromises their effector function, making metabolic targeting crucial for the improvement of T cell function. Folate-dependent purine synthesis, a core pathway sustaining the nucleotide pool, is highly activated in tumors, yet its role in regulating tumor immune sensitivity remains unclear. Here, by establishing a co-culture system of melanoma cells and human T Cell Receptor (TCR)-engineered T cells, we systematically evaluated the effects of folate-dependent purine synthesis inhibitors on tumor cell response to CD8+ T cell cytotoxicity. We found that inhibition of key enzymes such as methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) and glycinamide ribonucleotide transformylase (GART) markedly enhanced tumor cell sensitivity to T cell killing, an effect also observed with exogenous nucleoside supplementation. Mechanistically, inhibition of folate-dependent purine synthesis suppresses glycolysis by downregulating critical glycolytic enzymes, thereby reducing lactate production. Reduction in lactate further weakens lactylation and stability of the immune checkpoint protein PD-L1. In parallel, impaired purine synthesis disrupts uridine metabolism, blocks ribose salvage, and distally influences glycolysis. Collectively, our study identified the folate-dependent purine synthesis-glycolysis axis as key regulator of tumor immune response and highlights metabolic targeting as a promising strategy to improve cancer immunotherapy.

Brain metastases (BrM) are associated with poor prognosis. A better understanding of anti-tumor immune responses in the context of immune specialized microenvironment of the brain is required to develop improved therapeutic strategies for this disease. We demonstrate that the conventional dendritic cells type 1 (cDC1) gene signature positively correlates with a prolonged BrM-dependent survival in melanoma and breast cancer patients. Furthermore, intracranial anti-tumor immune responses in preclinical BrM models consistently rely on cDC1s for tumor growth control, BrM-dependent survival and maintenance of the intra-tumoral CD8+ T cell pool, in contrast to variable, cancer type-dependent cDC1 roles in extracranial tumors. This is underpinned by tumor site-specific cDC1 molecular profiles with distinct Toll like receptor repertoires, upregulation of co-stimulatory molecules and IL-12, and enhanced type-I-IFN signaling in intracranial cDC1s, with the latter driving increased cDC1 activation. cDC1s also promote the conversion of progenitor exhausted CD8+ T cells to transient effectors, which is further enhanced by immune checkpoint blockade therapy. These findings pinpoint cDC1s as a major cell population of interest in the development of future immunotherapies for BrM.

Aberrant epigenetic reprogramming together with dysregulated mTOR signaling are hallmarks of cancer, where altered chromatin methylation and nutrient-sensing pathways cooperate to drive tumor progression. S-adenosylmethionine (SAM), the universal methyl donor, is essential for these processes, yet how tumors sustain elevated SAM availability to support oncogenic transmethylation reactions remains poorly defined. Here, using prostate cancer (PCa) as a model system, we identify nicotinamide N-methyltransferase (NNMT) as a critical metabolic-epigenetic regulator and tumor suppressor. Using a prostate-specific Nnmt knockout mouse model, we demonstrate that NNMT loss accelerates PCa progression, particularly in the context of Pten deletion, resulting in infiltrating carcinoma and reduced survival. Mechanistically, NNMT functions as a "SAM-sink," and its loss increases intracellular SAM abundance, thereby activating mTORC1 signaling through SAMTOR-dependent sensing and broadly enhancing chromatin methylation. In human PCa, recurrent genomic deletions of NNMT occur in up to 7% of cases, and NNMT protein expression is largely absent in primary tumors and metastases. NNMT-deficient PCa cells exhibit elevated SAM:SAH ratios, increased histone methylation, and heightened mTORC1 activity, enabling sustained tumor growth even under dietary methionine-restriction (MR). Notably, combined MR and pharmacologic mTORC1 inhibition synergistically suppresses the growth of NNMT-deficient tumors, revealing a previously unrecognized therapeutic vulnerability. Collectively, these findings establish NNMT as a key tumor suppressor that constrains SAM-driven epigenetic and signaling programs in PCa and suggest a rational, diet-based therapeutic strategy for advanced cancers with NNMT loss.

BackgroundDysregulated cell migration leading to metastasis remains the primary cause of cancer-related mortality. It has been challenging to understand how cells regulate migration. We have previously created the first selective inhibitor of cell migration, KBU2046. Here, we use it as a probe to identify regulatory processes. MethodsMetastatic and primary human prostate cancer cells were treated for different times and at different concentrations with KBU2046. Immunofluorescent microscopy examined protein localization in cells. Label-free mass spectrometry (MS) was performed on total cell proteins, Tandem Mass Tag (TMT) labeling MS was used on membrane fractions, and temporal phosphoproteomic profiling. Results were analyzed with a suite of bioinformatic tools. ResultsKBU2046-induced migrastasis is associated with the accumulation of activated integrin {beta}1 into focal adhesions. Whole-cell proteomics demonstrated suppression of processes that mediate intracellular protein trafficking and increases in mitochondrial energy-generation signatures. Evaluation of the membrane fraction identified increases in membrane repair and maintenance processes and decreases in those that drive motility. Temporal- and concentration-dependent phosphoproteomic profiling revealed that KBU2046 initiates a dynamic, cascading sequence of transient signaling waves rather than a static block. ConclusionsKBU2046-induced migrastasis appears to operate through spatial decoupling rather than structural degradation. By restricting the intracellular trafficking machinery required for receptor recycling, KBU2046 limits focal adhesion turnover, providing a correlative framework to inhibit metastatic dissemination independent of direct cytotoxicity. O_FIG O_LINKSMALLFIG WIDTH=122 HEIGHT=200 SRC="FIGDIR/small/736165v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@1cc69d3org.highwire.dtl.DTLVardef@137b843org.highwire.dtl.DTLVardef@1225e50org.highwire.dtl.DTLVardef@15dd8d2_HPS_FORMAT_FIGEXP M_FIG Graphic Abstract C_FIG