MNK2 governs the macrophage antiinflammatory phenotype.

Tumor-associated macrophages (TAMs) continuously fine tune their immune modulatory properties, but how gene expression programs coordinate this immune cell plasticity is largely unknown. Selective mRNA translation, controlled by MNK1/MNK2 and mTOR pathways impinging on eIF4E, facilitates reshaping of proteomes without changes in abundance of corresponding mRNAs. Using polysome profiling developed for small samples we show that, during tumor growth, gene expression in TAMs is predominately modulated via mRNA-selective changes in translational efficiencies. These alterations in gene expression paralleled accumulation of antiinflammatory macrophages with augmented phosphorylation of eIF4E, a target of the MNK1 and MNK2 kinases, known to selectively modulate mRNA translation. Furthermore, suppression of the MNK2, but not the mTOR signaling pathway, reprogrammed antiinflammatory macrophages toward a proinflammatory phenotype with the ability to activate CD8+ T cells. Thus, selective changes of mRNA translation depending on MNK2 signaling represents a key node regulating macrophage antiinflammatory functions.

A Non-Hazardous Deparaffinization Protocol Enables Quantitative Proteomics of Core Needle Biopsy-Sized Formalin-Fixed and Paraffin-Embedded (FFPE) Tissue Specimens.

Most human tumor tissues that are obtained for pathology and diagnostic purposes are formalin-fixed and paraffin-embedded (FFPE). To perform quantitative proteomics of FFPE samples, paraffin has to be removed and formalin-induced crosslinks have to be reversed prior to proteolytic digestion. A central component of almost all deparaffinization protocols is xylene, a toxic and highly flammable solvent that has been reported to negatively affect protein extraction and quantitative proteome analysis. Here, we present a 'green' xylene-free protocol for accelerated sample preparation of FFPE tissues based on paraffin-removal with hot water. Combined with tissue homogenization using disposable micropestles and a modified protein aggregation capture (PAC) digestion protocol, our workflow enables streamlined and reproducible quantitative proteomic profiling of FFPE tissue. Label-free quantitation of FFPE cores from human ductal breast carcinoma in situ (DCIS) xenografts with a volume of only 0.79 mm3 showed a high correlation between replicates (r2 = 0.992) with a median %CV of 16.9%. Importantly, this small volume is already compatible with tissue micro array (TMA) cores and core needle biopsies, while our results and its ease-of-use indicate that further downsizing is feasible. Finally, our FFPE workflow does not require costly equipment and can be established in every standard clinical laboratory.

Coordinate transcriptional and translational repression of p53 by TGF-ß1 impairs the stress response.

Cellular stress results in profound changes in RNA and protein synthesis. How cells integrate this intrinsic, p53-centered program with extracellular signals is largely unknown. We demonstrate that TGF-ß1 signaling interferes with the stress response through coordinate transcriptional and translational repression of p53 levels, which reduces p53-activated transcription, and apoptosis in precancerous cells. Mechanistically, E2F-4 binds constitutively to the TP53 gene and induces transcription. TGF-ß1-activated Smads are recruited to a composite Smad/E2F-4 element by an E2F-4/p107 complex that switches to a Smad corepressor, which represses TP53 transcription. TGF-ß1 also causes dissociation of ribosomal protein RPL26 and elongation factor eEF1A from p53 mRNA, thereby reducing p53 mRNA association with polyribosomes and p53 translation. TGF-ß1 signaling is dominant over stress-induced transcription and translation of p53 and prevents stress-imposed downregulation of Smad proteins. Thus, crosstalk between the TGF-ß and p53 pathways defines a major node of regulation in the cellular stress response, enhancing drug resistance.

Translational control in the tumor microenvironment promotes lung metastasis: Phosphorylation of eIF4E in neutrophils.

The translation of mRNAs into proteins serves as a critical regulatory event in gene expression. In the context of cancer, deregulated translation is a hallmark of transformation, promoting the proliferation, survival, and metastatic capabilities of cancer cells. The best-studied factor involved in the translational control of cancer is the eukaryotic translation initiation factor 4E (eIF4E). We and others have shown that eIF4E availability and phosphorylation promote metastasis in mouse models of breast cancer by selectively augmenting the translation of mRNAs involved in invasion and metastasis. However, the impact of translational control in cell types within the tumor microenvironment (TME) is unknown. Here, we demonstrate that regulatory events affecting translation in cells of the TME impact cancer progression. Mice bearing a mutation in the phosphorylation site of eIF4E (S209A) in cells comprising the TME are resistant to the formation of lung metastases in a syngeneic mammary tumor model. This is associated with reduced survival of prometastatic neutrophils due to decreased expression of the antiapoptotic proteins BCL2 and MCL1. Furthermore, we demonstrate that pharmacological inhibition of eIF4E phosphorylation prevents metastatic progression in vivo, supporting the development of phosphorylation inhibitors for clinical use.

The MNK1/2-eIF4E Axis as a Potential Therapeutic Target in Melanoma.

: Melanoma is a type of skin cancer that originates in the pigment-producing cells of the body known as melanocytes. Most genetic aberrations in melanoma result in hyperactivation of the mitogen activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K) pathways. We and others have shown that a specific protein synthesis pathway known as the MNK1/2-eIF4E axis is often dysregulated in cancer. The MNK1/2-eIF4E axis is a point of convergence for these signaling pathways that are commonly constitutively activated in melanoma. In this review we consider the functional implications of aberrant mRNA translation in melanoma and other malignancies. Moreover, we discuss the consequences of inhibiting the MNK1/2-eIF4E axis on the tumor and tumor-associated cells, and we provide important avenues for the utilization of this treatment modality in combination with other targeted and immune-based therapies. The past decade has seen the increased development of selective inhibitors to block the action of the MNK1/2-eIF4E pathway, which are predicted to be an effective therapy regardless of the melanoma subtype (e.g., cutaneous, acral, and mucosal).

Genome-wide targeting of the epigenetic regulatory protein CTCF to gene promoters by the transcription factor TFII-I.

CCCTC-binding factor (CTCF) is a key regulator of nuclear chromatin structure and gene regulation. The impact of CTCF on transcriptional output is highly varied, ranging from repression to transcriptional pausing and transactivation. The multifunctional nature of CTCF may be directed solely through remodeling chromatin architecture. However, another hypothesis is that the multifunctional nature of CTCF is mediated, in part, through differential association with protein partners having unique functions. Consistent with this hypothesis, our mass spectrometry analyses of CTCF interacting partners reveal a previously undefined association with the transcription factor general transcription factor II-I (TFII-I). Biochemical fractionation of CTCF indicates that a distinct CTCF complex incorporating TFII-I is assembled on DNA. Unexpectedly, we found that the interaction between CTCF and TFII-I is essential for directing CTCF to the promoter proximal regulatory regions of target genes across the genome, particularly at genes involved in metabolism. At genes coregulated by CTCF and TFII-I, we find knockdown of TFII-I results in diminished CTCF binding, lack of cyclin-dependent kinase 8 (CDK8) recruitment, and an attenuation of RNA polymerase II phosphorylation at serine 5. Phenotypically, knockdown of TFII-I alters the cellular response to metabolic stress. Our data indicate that TFII-I directs CTCF binding to target genes, and in turn the two proteins cooperate to recruit CDK8 and enhance transcription initiation.

The novel arsenical darinaparsin is transported by cystine importing systems.

Darinaparsin (Dar; ZIO-101; S-dimethylarsino-glutathione) is a promising novel organic arsenical currently undergoing clinical studies in various malignancies. Dar consists of dimethylarsenic conjugated to glutathione (GSH). Dar induces more intracellular arsenic accumulation and more cell death than the FDA-approved arsenic trioxide (ATO) in vitro, but exhibits less systemic toxicity. Here, we propose a mechanism for Dar import that might explain these characteristics. Structural analysis of Dar suggests a putative breakdown product: dimethylarsino-cysteine (DMAC). We show that DMAC is very similar to Dar in terms of intracellular accumulation of arsenic, cell cycle arrest, and cell death. We found that inhibition of γ-glutamyl-transpeptidase (γ-GT) protects human acute promyelocytic leukemia cells (NB4) from Dar, but not from DMAC, suggesting a role for γ-GT in the processing of Dar. Overall, our data support a model where Dar, a GSH S-conjugate, is processed at the cell surface by γ-GT, leading to formation of DMAC, which is imported via xCT, xAG, or potentially other cystine/cysteine importing systems. Further, we propose that Dar induces its own import via increased xCT expression. These mechanisms may explain the enhanced toxicity of Dar toward cancer cells compared with ATO.

A comparative study of CARE 2D and N2V 2D for tissue-specific denoising in second harmonic generation imaging.

This study explored the application of deep learning in second harmonic generation (SHG) microscopy, a rapidly growing area. This study focuses on the impact of glycerol concentration on image noise in SHG microscopy and compares two image restoration techniques: Noise-to-Void 2D (N2V 2D, no reference image restoration) and content-aware image restoration (CARE 2D, full reference image restoration). We demonstrated that N2V 2D effectively restored the images affected by high glycerol concentrations. To reduce sample exposure and damage, this study further addresses low-power SHG imaging by reducing the laser power by 70% using deep learning techniques. CARE 2D excels in preserving detailed structures, whereas N2V 2D maintains natural muscle structure. This study highlights the strengths and limitations of these models in specific SHG microscopy applications, offering valuable insights and potential advancements in the field .

Clinical variables associated with immune checkpoint inhibitor outcomes in patients with metastatic urothelial carcinoma: a multicentre retrospective cohort study.

OBJECTIVES: Immune checkpoint inhibitors (ICIs) are indicated for metastatic urothelial cancer (mUC), but predictive and prognostic factors are lacking. We investigated clinical variables associated with ICI outcomes. METHODS: We performed a multicentre retrospective cohort study of 135 patients who received ICI for mUC, 2016-2021, at three Canadian centres. Clinical characteristics, body mass index (BMI), metastatic sites, neutrophil-to-lymphocyte ratio (NLR), response and survival were abstracted from chart review. RESULTS: We identified 135 patients and 62% had received ICI as a second-line or later treatment for mUC. A BMI ≥25 was significantly correlated to a higher overall response rate (ORR) (45.4% vs 16.3%, p value=0.020). Patients with BMI ≥30 experienced longer median overall survival (OS) of 24.8 vs 14.4 for 25≤BMI<30 and 8.5 months for BMI <25 (p value=0.012). The ORR was lower in the presence of bone metastases (16% vs 41%, p value=0.006) and liver metastases (16% vs 39%, p value=0.013). Metastatic lymph nodes were correlated with higher ORR (40% vs 20%, p value=0.032). The median OS for bone metastases was 7.3 versus 18 months (p value <0.001). Patients with liver metastases had a median OS of 8.6 versus 15 months (p value=0.006). No difference for lymph nodes metastases (13.5 vs 12.7 months, p value=0.175) was found. NLR ≥4 had worse OS (8.2 vs 17.7 months, p value=0.0001). In multivariate analysis, BMI ≥30, bone metastases, NLR ≥4, performance status ≥2 and line of ICI ≥2 were independent factors for OS. CONCLUSIONS: Our data identified BMI and bone metastases as novel clinical biomarkers that were independently associated with ICI outcomes in mUC. External and prospective validation are warranted.

Tunable PhenoCycler imaging of the murine pre-clinical tumour microenvironments.

BACKGROUND: The tumour microenvironment (TME) consists of tumour-supportive immune cells, endothelial cells, and fibroblasts. PhenoCycler, a high-plex single cell spatial biology imaging platform, is used to characterize the complexity of the TME. Researchers worldwide harvest and bank tissues from mouse models which are employed to model a plethora of human disease. With the explosion of interest in spatial biology, these panoplies of archival tissues provide a valuable resource to answer new questions. Here, we describe our protocols for developing tunable PhenoCycler multiplexed imaging panels and describe our open-source data analysis pipeline. Using these protocols, we used PhenoCycler to spatially resolve the TME of 8 routinely employed pre-clinical models of lymphoma, breast cancer, and melanoma preserved as FFPE. RESULTS: Our data reveal distinct TMEs in the different cancer models that were imaged and show that cell-cell contacts differ depending on the tumour type examined. For instance, we found that the immune infiltration in a murine model of melanoma is altered in cellular organization in melanomas that become resistant to αPD-1 therapy, with depletions in a number of cell-cell interactions. CONCLUSIONS: This work presents a valuable resource study seamlessly adaptable to any field of research involving murine models. The methodology described allows researchers to address newly formed hypotheses using archival materials, bypassing the new to perform new mouse studies.

STAT6 mutations enriched at diffuse large B-cell lymphoma relapse reshape the tumor microenvironment.

Diffuse large B-cell lymphoma (DLBCL) relapses in approximately 40% of patients following frontline therapy. We reported that STAT6D419 mutations are enriched in relapsed/refractory DLBCL (rrDLBCL) samples, suggesting that JAK/STAT signaling plays a role in therapeutic resistance. We hypothesized that STAT6D419 mutations can improve DLBCL cell survival by reprogramming the microenvironment to sustain STAT6 activation. Thus, we investigated the role of STAT6D419 mutations on DLBCL cell growth and its microenvironment. We found that phospho-STAT6D419N was retained in the nucleus longer than phospho-STAT6WT following IL-4 stimulation, and STAT6D419N recognized a more restricted DNA-consensus sequence than STAT6WT. Upon IL-4 induction, STAT6D419N expression led to a higher magnitude of gene expression changes, but in a more selective list of gene targets compared with STATWT. The most significantly expressed genes induced by STAT6D419N were those implicated in survival, proliferation, migration, and chemotaxis, in particular CCL17. This chemokine, also known as TARC, attracts helper T-cells to the tumor microenvironment, especially in Hodgkin's lymphoma. To this end, in DLBCL, phospho-STAT6+ rrDLBCL cells had a greater proportion of infiltrating CD4+ T-cells than phospho-STAT6- tumors. Our findings suggest that STAT6D419 mutations in DLBCL lead to cell autonomous changes, enhanced signaling, and altered composition of the tumor microenvironment.

Blocking tumor-intrinsic MNK1 kinase restricts metabolic adaptation and diminishes liver metastasis.

Dysregulation of the mitogen-activated protein kinase interacting kinases 1/2 (MNK1/2)-eukaryotic initiation factor 4E (eIF4E) signaling axis promotes breast cancer progression. MNK1 is known to influence cancer stem cells (CSCs); self-renewing populations that support metastasis, recurrence, and chemotherapeutic resistance, making them a clinically relevant target. The precise function of MNK1 in regulating CSCs, however, remains unexplored. Here, we generated MNK1 knockout cancer cell lines, resulting in diminished CSC properties in vitro and slowed tumor growth in vivo. Using a multiomics approach, we functionally demonstrated that loss of MNK1 restricts tumor cell metabolic adaptation by reducing glycolysis and increasing dependence on oxidative phosphorylation. Furthermore, MNK1-null breast and pancreatic tumor cells demonstrated suppressed metastasis to the liver, but not the lung. Analysis of The Cancer Genome Atlas (TCGA) data from breast cancer patients validated the positive correlation between MNK1 and glycolytic enzyme protein expression. This study defines metabolic perturbations as a previously unknown consequence of targeting MNK1/2, which may be therapeutically exploited.

Fibroblast Isolation from Mammary Gland Tissue and Syngeneic Murine Breast Cancer Models.

Cancer-associated fibroblasts (CAFs) are vital within the tumor ecosystem, regulating tumor growth, dissemination, and response to therapy through crosstalk with tumor cells, infiltrating immune and vascular cells, as well as components of the extracellular matrix (ECM). CAFs have thus emerged as potential therapeutic targets to complement cancer cell-targeted therapies. To study CAF-tumor cell crosstalk ex vivo, robust isolation methods of primary CAFs are required. Here, we present protocols to isolate, expand, and culture two types of fibroblasts: (1) healthy murine mammary gland fibroblasts, a key source of the CAF population in breast tumor models and (2) CAFs derived from syngeneic murine breast tumors. Isolated mammary fibroblasts and CAFs are suitable for use in a variety of downstream cellular and molecular experiments. We expect these methods to be useful to scientists studying the properties of fibroblasts and CAFs and the interaction between CAFs and the various components of the tumor microenvironment (TME).

Analyzing the Tumor-Immune Microenvironment by Flow Cytometry.

Flow cytometry is an essential tool for studying the tumor-immune microenvironment. It allows us to quickly quantify and identify multiple cell types in a heterogeneous sample. This chapter provides an overview of the flow cytometry instrumentation and a discussion of the appropriate considerations and steps in building a reproducible flow cytometry staining panel. We present an updated lymphoid tissue and solid tumor-infiltrating leucocyte flow cytometry staining protocol and an example of flow cytometry data analysis.

The role of eIF4F-driven mRNA translation in regulating the tumour microenvironment.

Cells can rapidly adjust their proteomes in dynamic environments by regulating mRNA translation. There is mounting evidence that dysregulation of mRNA translation supports the survival and adaptation of cancer cells, which has stimulated clinical interest in targeting elements of the translation machinery and, in particular, components of the eukaryotic initiation factor 4F (eIF4F) complex such as eIF4E. However, the effect of targeting mRNA translation on infiltrating immune cells and stromal cells in the tumour microenvironment (TME) has, until recently, remained unexplored. In this Perspective article, we discuss how eIF4F-sensitive mRNA translation controls the phenotypes of key non-transformed cells in the TME, with an emphasis on the underlying therapeutic implications of targeting eIF4F in cancer. As eIF4F-targeting agents are in clinical trials, we propose that a broader understanding of their effect on gene expression in the TME will reveal unappreciated therapeutic vulnerabilities that could be used to improve the efficacy of existing cancer therapies.

Nonlinear microscopy and deep learning classification for mammary gland microenvironment studies.

Tumors, their microenvironment, and the mechanisms by which collagen morphology changes throughout cancer progression have recently been a topic of interest. Second harmonic generation (SHG) and polarization second harmonic (P-SHG) microscopy are label-free, hallmark methods that can highlight this alteration in the extracellular matrix (ECM). This article uses automated sample scanning SHG and P-SHG microscopy to investigate ECM deposition associated with tumors residing in the mammary gland. We show two different analysis approaches using the acquired images to distinguish collagen fibrillar orientation changes in the ECM. Lastly, we apply a supervised deep-learning model to classify naïve and tumor-bearing mammary gland SHG images. We benchmark the trained model using transfer learning with the well-known MobileNetV2 architecture. By fine-tuning the different parameters of these models, we show a trained deep-learning model that suits such a small dataset with 73% accuracy.

Proteomic Assessment of the Murine Mammary Gland Extracellular Matrix.

The extracellular matrix (ECM) is a molecular scaffold mainly comprising fibrous proteins, glycoproteins, proteoglycans, and polysaccharides. Aside from acting as a structural support, the ECM's composition dictates cell-matrix interactions at the biochemical and biophysical level. In the context of cancer, the ECM is a critical component of the tumor microenvironment (TME) and dysregulation of its deposition and remodelling has been shown to promote tumor onset, progression, and metastasis. Here, we describe a robust protocol for the isolation and subsequent proteomic analysis of the ECM of murine mammary glands, for downstream assays studying the role of the ECM in breast cancer. The protocol yields sufficient protein amounts to enable not only the global quantitation of protein expression but furthermore the enrichment and quantitative analysis of post-translationally modified peptides to study aberrant signalling.

Peroxisome disruption alters lipid metabolism and potentiates antitumor response with MAPK-targeted therapy in melanoma.

Melanomas reprogram their metabolism to rapidly adapt to therapy-induced stress conditions, allowing them to persist and ultimately develop resistance. We report that a subpopulation of melanoma cells tolerate MAPK pathway inhibitors (MAPKis) through a concerted metabolic reprogramming mediated by peroxisomes and UDP-glucose ceramide glycosyltransferase (UGCG). Compromising peroxisome biogenesis, by repressing PEX3 expression, potentiated the proapoptotic effects of MAPKis via an induction of ceramides, an effect limited by UGCG-mediated ceramide metabolism. Cotargeting PEX3 and UGCG selectively eliminated a subset of metabolically active, drug-tolerant CD36+ melanoma persister cells, thereby sensitizing melanoma to MAPKis and delaying resistance. Increased levels of peroxisomal genes and UGCG were found in patient-derived MAPKi-relapsed melanomas, and simultaneously inhibiting PEX3 and UGCG restored MAPKi sensitivity in multiple models of therapy resistance. Finally, combination therapy consisting of a newly identified inhibitor of the PEX3-PEX19 interaction, a UGCG inhibitor, and MAPKis demonstrated potent antitumor activity in preclinical melanoma models, thus representing a promising approach for melanoma treatment.

Inhibition of the MNK1/2-eIF4E Axis Augments Palbociclib-Mediated Antitumor Activity in Melanoma and Breast Cancer.

Aberrant cell-cycle progression is characteristic of melanoma, and CDK4/6 inhibitors, such as palbociclib, are currently being tested for efficacy in this disease. Despite the promising nature of CDK4/6 inhibitors, their use as single agents in melanoma has shown limited clinical benefit. Herein, we discovered that treatment of tumor cells with palbociclib induces the phosphorylation of the mRNA translation initiation factor eIF4E. When phosphorylated, eIF4E specifically engenders the translation of mRNAs that code for proteins involved in cell survival. We hypothesized that cancer cells treated with palbociclib use upregulated phosphorylated eIF4E (phospho-eIF4E) to escape the antitumor benefits of this drug. Indeed, we found that pharmacologic or genetic disruption of MNK1/2 activity, the only known kinases for eIF4E, enhanced the ability of palbociclib to decrease clonogenic outgrowth. Moreover, a quantitative proteomics analysis of melanoma cells treated with combined MNK1/2 and CDK4/6 inhibitors showed downregulation of proteins with critical roles in cell-cycle progression and mitosis, including AURKB, TPX2, and survivin. We also observed that palbociclib-resistant breast cancer cells have higher basal levels of phospho-eIF4E, and that treatment with MNK1/2 inhibitors sensitized these palbociclib-resistant cells to CDK4/6 inhibition. In vivo we demonstrate that the combination of MNK1/2 and CDK4/6 inhibition significantly increases the overall survival of mice compared with either monotherapy. Overall, our data support MNK1/2 inhibitors as promising drugs to potentiate the antineoplastic effects of palbociclib and overcome therapy-resistant disease.

PRMT7 ablation stimulates anti-tumor immunity and sensitizes melanoma to immune checkpoint blockade.

Despite the success of immune checkpoint inhibitor (ICI) therapy for cancer, resistance and relapse are frequent. Combination therapies are expected to enhance response rates and overcome this resistance. Herein, we report that combining PRMT7 inhibition with ICI therapy induces a strong anti-tumor T cell immunity and restrains tumor growth in vivo by increasing immune cell infiltration. PRMT7-deficient B16.F10 melanoma exhibits increased expression of genes in the interferon pathway, antigen presentation, and chemokine signaling. PRMT7 deficiency or inhibition with SGC3027 in B16.F10 melanoma results in reduced DNMT expression, loss of DNA methylation in the regulatory regions of endogenous retroviral elements (ERVs) causing their increased expression. PRMT7-deficient cells increase RIG-I and MDA5 expression with a reduction in the H4R3me2s repressive histone mark at their gene promoters. Our findings identify PRMT7 as a regulatory checkpoint for RIG-I, MDA5, and their ERV-double-stranded RNA (dsRNA) ligands, facilitating immune escape and anti-tumor T cell immunity to restrain tumor growth.