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Tumor vessel co-option (VCO) is a non-angiogenic vascularization mechanism that is a possible cause of resistance to anti-angiogenic therapy (AAT). Multiple tumors are hypothesized to primarily rely on growth factor signaling-induced sprouting angiogenesis, which is often inhibited during AAT. During VCO however, tumors invade healthy tissues by hijacking pre-existing blood vessels of the host organ to secure their blood and nutrient supply. Although VCO has been described in the context of AAT resistance, the molecular mechanisms underlying this process and the profile and characteristics of co-opted vascular cell types (endothelial cells (ECs) and pericytes) remain poorly understood, resulting in the lack of therapeutic strategies to inhibit VCO (and to overcome AAT resistance). In the past few years, novel next-generation technologies (such as single-cell RNA sequencing) have emerged and revolutionized the way of analyzing and understanding cancer biology. While most studies utilizing single-cell RNA sequencing with focus on cancer vascularization have centered around ECs during sprouting angiogenesis, we propose that this and other novel technologies can be used in future investigations to shed light on tumor EC biology during VCO. In this review, we summarize the molecular mechanisms driving VCO known to date and introduce the models used to study this phenomenon to date. We highlight VCO studies that recently emerged using sequencing approaches and propose how these and other novel state-of-the-art methods can be used in the future to further explore ECs and other cell types in the VCO process and to identify potential vulnerabilities in tumors relying on VCO. A better understanding of VCO by using novel approaches could provide new answers to the many open questions, and thus pave the way to develop new strategies to control and target tumor vascularization. ispartof: FRONTIERS IN ONCOLOGY vol:12 ispartof: location:Switzerland status: published

Fluorouracil (5-FU) is the first-line chemotherapeutic drug for cholangiocarcinoma (CCA), but its efficacy has been compromised by the development of resistance. Development of 5-FU resistance is associated with elevated expression of its cellular target, thymidylate synthase (TYMS). E2F1 transcription factor has previously been shown to modulate the expression of FOXM1 and TYMS. Immunohistochemical (IHC) analysis revealed a strong correlated upregulation of FOXM1 (78%) and TYMS (48%) expression at the protein levels in CCA tissues. In agreement, RT-qPCR and western blot analyses of four human CCA cell lines at the baseline level and in response to high doses of 5-FU revealed good correlations between FOXM1 and TYMS expression in the CCA cell lines tested, except for the highly 5-FU-resistant HuCCA cells. Consistently, siRNA-mediated knockdown of FOXM1 reduced the clonogenicity and TYMS expression in the relatively sensitive KKU-D131 but not in the highly resistant HuCCA cells. Interestingly, silencing of TYMS sensitized both KKU-D131 and HuCCA to 5-FU treatment, suggesting that resistance to very high levels of 5-FU is due to the inability of the genotoxic sensor FOXM1 to modulate TYMS expression. Consistently, ChIP analysis revealed that FOXM1 binds efficiently to the TYMS promoter and modulates TYMS expression at the promoter level upon 5-FU treatment in KKU-D131 but not in HuCCA cells. In addition, E2F1 expression did not correlate with either FOXM1 or TYMS expression and E2F1 depletion has no effects on the clonogenicity and TYMS expression in the CCA cells. In conclusion, our data show that FOXM1 regulates TYMS expression to modulate 5-FU resistance in CCA and that severe 5-FU resistance can be caused by the uncoupling of the regulation of TYMS by FOXM1. Our findings suggest that the FOXM1–TYMS axis can be a novel diagnostic, predictive and prognostic marker as well as a therapeutic target for CCA.

Significance Cancer therapies often fail to cure patients because a proportion of tumor cells withstand the toxic effects of chemotherapy. How surviving cancer cells recover from sublethal drug-induced stress is not known, but given that cellular resources are finite, stress resolution may come at the expense of less essential systems. Here, we studied the global cellular events of stress buildup and resolution in the bone marrow cancer, multiple myeloma, after proteasome inhibition, a commonly used therapeutic approach. Using a temporal multiomics approach, we delineate the unexpectedly complex and protracted changes myeloma cells undergo during stress resolution and demonstrate that recovering cells are more vulnerable to specific insults than acutely stressed cells. Thus, the findings may provide avenues for optimizing cancer therapies., Cancer cells can survive chemotherapy-induced stress, but how they recover from it is not known. Using a temporal multiomics approach, we delineate the global mechanisms of proteotoxic stress resolution in multiple myeloma cells recovering from proteasome inhibition. Our observations define layered and protracted programs for stress resolution that encompass extensive changes across the transcriptome, proteome, and metabolome. Cellular recovery from proteasome inhibition involved protracted and dynamic changes of glucose and lipid metabolism and suppression of mitochondrial function. We demonstrate that recovering cells are more vulnerable to specific insults than acutely stressed cells and identify the general control nonderepressable 2 (GCN2)-driven cellular response to amino acid scarcity as a key recovery-associated vulnerability. Using a transcriptome analysis pipeline, we further show that GCN2 is also a stress-independent bona fide target in transcriptional signature-defined subsets of solid cancers that share molecular characteristics. Thus, identifying cellular trade-offs tied to the resolution of chemotherapy-induced stress in tumor cells may reveal new therapeutic targets and routes for cancer therapy optimization.

Cellular protein homeostasis (proteostasis) depends on the controlled degradation of proteins that are damaged or no longer required by the ubiquitin-proteasome system (UPS). The 26S proteasome is the principal executer of substrate-specific proteolysis in eukaryotic cells and regulates a myriad of cellular functions. Proteasome inhibitors were initially developed as chemical tools to study proteasomal function but rapidly became widely used anticancer drugs that are now used at all stages of treatment for the bone marrow cancer multiple myeloma (MM). Here, we review the mechanisms of action of proteasome inhibitors that underlie their preferential toxicity to MM cells, focusing on endoplasmic reticulum stress, depletion of amino acids, and effects on glucose and lipid metabolism. We also discuss mechanisms of resistance to proteasome inhibition such as autophagy and metabolic rewiring and what lessons we may learn from the success and failure of proteasome inhibition in MM for treating other cancers with proteostasis-targeting drugs.

FOXO3 is a tumor suppressor that orchestrates the expression of genes that regulate cell cycle progression, apoptosis, metabolism, oxidative stress, and other important cellular processes. Its inactivation is closely associated with tumorigenesis and cancer progression. On the other hand, sirtuin proteins have been demonstrated to be able to deacetylate, thus causing FOXO3 inactivation at the posttranslational level. Therefore, targeting sirtuin proteins renders new avenues for breast cancer treatment. Here, we describe three procedures for studying FOXO3 posttranslational modifications controlled by sirtuin proteins in cancer cells.

FOXO3 is a tumor suppressor that orchestrates the expression of genes that regulate cell cycle progression, apoptosis, metabolism, oxidative stress, and other important cellular processes. Its inactivation is closely associated with tumorigenesis and cancer progression. On the other hand, sirtuin proteins have been demonstrated to be able to deacetylate, thus causing FOXO3 inactivation at the posttranslational level. Therefore, targeting sirtuin proteins renders new avenues for breast cancer treatment. Here, we describe three procedures for studying FOXO3 posttranslational modifications controlled by sirtuin proteins in cancer cells.

Aims Fatty acid binding protein 4 (FABP4) inhibitors have been proposed as potential therapeutic approaches against insulin resistance-related inflammation and type 2 diabetes mellitus. However, the underlying molecular mechanisms by which these molecules drive these effects in skeletal muscle remain unknown. Here, we assessed whether the FABP4 inhibitor BMS309403 prevented lipid-induced endoplasmic reticulum (ER) stress-associated inflammation in skeletal muscle. Materials and methods The BMS309403 treatment was assessed both in the skeletal muscle of high-fat diet (HFD)-fed mice and in palmitate-stimulated C2C12 myotubes. Results HFD feeding promoted insulin resistance, which is characterized by increased plasma levels of glucose, insulin, non-esterified fatty acids, triglycerides, resistin, and leptin and reduced plasma levels of adiponectin compared with control mice fed a standard diet. Additionally, insulin-resistant animals showed increased FABP4 plasma levels. In line with this evidence, recombinant FABP4 attenuated the insulin-induced AKT phosphorylation in C2C12 myotubes. Treatment with BMS309403 reduced lipid-induced ER stress and inflammation in both mouse skeletal muscle and C2C12 myotubes. The effects of the FABP4 inhibitor reducing lipid-induced ER stress-associated inflammation were related to the reduction of fatty acid-induced intramyocellular lipid deposits, ROS and nuclear factor-kappaB (NF-κB) nuclear translocation. Accordingly, BMS309403 reduced lipid-induced p38 MAPK phosphorylation, which is upstream of NF-κB activation. Conclusion Overall, these findings indicate that BMS309403 reduces fatty acid-induced ER stress-associated inflammation in skeletal muscle by reducing p38 MAPK activation.

Obesity and cachexia represent divergent states of nutritional and metabolic imbalance but both are intimately linked to cancer. There is an extensive overlap in their signalling pathways and molecular components involved such as fatty acids (FAs), which likely play a crucial role in cancer. Forkhead box (FOX) proteins are responsible of a wide range of transcriptional programmes during normal development, and the FOXO3-FOXM1 axis is associated with cancer initiation, progression and drug resistance. Free fatty acids (FFAs), FA synthesis and β-oxidation are associated with cancer development and progression. Meanwhile, insulin and some adipokines, that are up-regulated by FAs, are also involved in cancer development and poor prognosis. In this review, we discuss the role of FA metabolism in cancer and how FA metabolism integrates with the FOXO3-FOXM1 axis. These new insights may provide leads to better cancer diagnostics as well as strategies for tackling cancer development, progression and drug resistance.

Proteasome inhibitors (PIs) form the backbone of multiple myeloma (MM) treatment regimens used at diagnosis and relapse, but their clinical benefit is limited by varying degrees of resistance. The mechanisms that protect MM cells (MMCs) from PI-induced cell death are only partly understood, and experimental resistance studies often rely on the prolonged exposure of MMCs to relatively low levels of PIs. However, patients receive PI doses that result in high but short plasma peaks. Given that each PI dose reduces a patient's MMC load until a plateau is reached, one can assume that each PI dose kills some MMCs by triggering overwhelming stress. This proposition implies that a proportion of MMCs not only survive but also resolve PI-induced stress. We hypothesised that the mechanisms of PI-induced stress recovery require a redistribution of cellular resources, and that this process triggers specific recovery-associated and potentially druggable vulnerabilities. To test this hypothesis, we obtained a global systems-level view of the cellular response to proteasome inhibition by performing a multi-omics 10-day time-course experiment. To mimic in vivo pharmacokinetics and anti-MM effects, RPMI-8226 MMCs were treated with a 1h pulse of carfilzomib (CFZ; 750nmol/L), which reduced the number of viable MMCs to a nadir of approximately 50% on day +2, followed by a return to pretreatment baseline levels of viable cells by day +6. Levels of ubiquitinated proteins as a readout of effective proteasome inhibition peaked on day +1 and returned to baseline levels on day +6. Samples for transcriptome analysis by RNA-seq, proteome analysis by a multiplexed tandem mass tag (TMT)-based approach, and global metabolomic profiling by ultrahigh performance liquid chromatography-tandem mass spectroscopy (LC-MS) were collected 2h prior to the CFZ pulse (day 0) and on days +1, +2, +4, +6, +8, and +10. The results demonstrate extensive and kinetically complex changes of the MMC transcriptome, proteome and metabolome that did not fully return to baseline by day +10. Conventional and advanced computational analyses of RNA-seq data (including biological homogeneity score-validated graph-based clustering of temporal patterns combined with gene enrichment and KEGG/GO pathway analysis) revealed different patterns of involvement of multiple and functionally diverse pathways. Perhaps most notably, RNA-seq data revealed extensive metabolic pathway responses while cells were dying and throughout recovery. Consistently, metabolomic profiling by LC-MS showed wide-ranging metabolite changes. These included rapid intracellular depletion of glucose, which was paralleled by the accumulation of lactate and pyruvate and lasted until day +8. Consistently, the major glucose uptake regulator TXNIP stood out as upregulated during recovery, which was accompanied by the predicted downregulation of the glucose transporter GLUT1. These findings were confirmed by real-time PCR and immunoblotting in RPMI-8226 and other MMC lines. Moreover, pharmacological inhibition of glucose and lactate metabolising enzymes and transmembrane transport enhanced MMC killing by CFZ, confirming profound and druggable changes in glucose and energy metabolism during PI stress recovery. We also observed prolonged depletion of a number of amino acids, including glutamine, which was paralleled by depletion of glutamate and TCA cycle intermediates. Moreover, we found RNA-seq and real-time PCR/immunoblot-based evidence for an amino acid response (AAR) during stress recovery that was driven by the amino acid sensing kinase GCN2 (EIF2AK4). The preclinical GCN2 inhibitor GCN2iB was effective at blocking the AAR and enhanced MMC killing in a panel of CFZ-treated MMC lines. This effect was particularly pronounced during the intermediate stages of recovery, in line with the kinetics of amino acid depletion and the AAR. Thus, our observations define the complex and prolonged cellular responses that characterise the recovery of MMCs from proteasome inhibition. They reveal wide-ranging metabolic changes that persist far beyond immediate stress survival and highlight the dependence of MMCs on the GCN2-driven AAR to overcome PI stress. The findings demonstrate that the mechanisms of PI recovery trigger druggable vulnerabilities, providing the basis for ongoing investigations into sequential therapeutic interventions to enhance responses to PIs. Disclosures Caputo: GSK: Research Funding. Kaiser:Abbvie, Celgene, Takeda, Janssen, Amgen, Abbvie, Karyopharm: Consultancy; Celgene, Janssen: Research Funding; Takeda, Janssen, Celgene, Amgen: Honoraria, Other: Travel Expenses. Auner:Karyopharm: Consultancy; Takeda: Consultancy; Amgen: Other: Consultancy and Research Funding.

Circulating FABP4 and FABP5 may be a biomarker for breast cancer. This article focuses on the association of FABP4 and FABP5 plasma levels with the presence of breast cancer., Background. Adipose tissue is an endocrine organ that could play a role in tumor progression via its secreted adipokines. The role of adipose‐derived fatty acid‐binding protein (FABP) 4 and FABP5 in breast cancer is presently under study, but their circulating levels in this pathology are poorly known. We analyzed the blood concentrations of FABP4 and FABP5 in breast cancer patients to determine whether there is an association between them and breast cancer. Materials and Methods. We studied 294 women in the oncology department with a family history of breast cancer; 198 of the women had breast cancer, and 96 were healthy controls. The levels of FABP4, FABP5, lipid profile, standard biochemical parameter, and high‐sensitivity C‐reactive protein (hsCRP) were determined. We analyzed the association of FABP4 and FABP5 with breast cancer, while adjusting for demographic, anthropometric, and biochemical parameters. Results. Breast cancer patients had a 24.8% (p