Drilling for Oil: Tumor-Surrounding Adipocytes Fueling Cancer

The relationship between Stroma AReactive Invasion Front Areas (SARIFA), Warburg-subtype and survival: results from a large prospective series of colorectal cancer patients

BACKGROUND

Stroma AReactive Invasion Front Areas (SARIFA) is a recently identified haematoxylin & eosin (H&E)based histopathologic biomarker in gastrointestinal cancers, including colorectal cancer (CRC), defined as direct contact between tumour cells and adipocytes at the tumour invasion front. The current study aimed at validating the prognostic relevance of SARIFA in a large population-based CRC series as well as at investigating the relationship between SARIFA-status and previously established Warburg-subtypes, both surrogates of the metabolic state of the tumour cells.

METHODS

SARIFA-status (positive versus negative) was determined on H&E slides of 1,727 CRC specimens. Warburg-subtype (high versus moderate versus low) data was available from our previous study. The associations between SARIFA-status, Warburg-subtype, clinicopathological characteristics and CRC-specific as well as overall survival were investigated.

RESULTS

28.7% (n=496) CRC were SARIFA-positive. SARIFA-positivity was associated with more advanced disease stage, higher pT category, and more frequent lymph node involvement (all p<0.001). SARIFA-positivity was more common in Warburg-high CRC. 44.2% (n=219) of SARIFA-positive CRCs were Warburg-high compared to 22.8% (n=113) being Warburg-low and 33.1% (n=164) being Warburg-moderate (p<0.001). In multivariable-adjusted analysis, patients with SARIFA-positive CRCs had significantly poorer CRC-specific (HRCRC-specific 1.65; 95% CI 1.41-1.93) and overall survival (HRoverall survival 1.46; 95% CI 1.28-1.67) independent of clinically known risk factors and independent of Warburg-subtype. Combining the SARIFA-status and the Warburg-subtype to a combination score (SARIFA-negative/Warburg-high versus SARIFA-positive/Warburg-low versus SARIFA-positive/Warburg-high, and so on) did not improve the survival prediction compared to the use of SARIFA-status alone (SARIFA-negative + Warburg-high: HRCRC-specific 1.08; 95% CI 0.84-1.38; SARIFA-positive + Warburg-low: HRCRC-specific 1.79; 95% CI 1.32-2.41; SARIFA-positive + Warburg-high: HRCRC-specific 1.58; 95% CI 1.23-2.04).

CONCLUSIONS

Our current study is the by far largest external validation of SARIFA-positivity as a novel independent negative prognostic H&E-based biomarker in CRC. In addition, our study shows that SARIFA-positivity is associated with the Warburg-high subtype. Further research is warranted to provide a more mechanistic understanding of the underlying tumour biology. Based on our data, we conclude SARIFA-status should be implemented in pathologic routine practice to stratify CRC patients.

The Complex Tumor Microenvironment in Ovarian Cancer: Therapeutic Challenges and Opportunities

The tumor microenvironment (TME) in ovarian cancer (OC) has much greater complexity than previously understood. In response to aggressive pro-angiogenic stimulus, blood vessels form rapidly and are dysfunctional, resulting in poor perfusion, tissue hypoxia, and leakiness, which leads to increased interstitial fluid pressure (IFP). Decreased perfusion and high IFP significantly inhibit the uptake of therapies into the tumor. Within the TME, there are numerous inhibitor cells, such as myeloid-derived suppressor cells (MDSCs), tumor association macrophages (TAMs), regulatory T cells (Tregs), and cancer-associated fibroblasts (CAFs) that secrete high numbers of immunosuppressive cytokines. This immunosuppressive environment is thought to contribute to the lack of success of immunotherapies such as immune checkpoint inhibitor (ICI) treatment. This review discusses the components of the TME in OC, how these characteristics impede therapeutic efficacy, and some strategies to alleviate this inhibition.

Specificities of mammary and periprostatic adipose tissues: A perspective from cancer research

In addition to the major subcutaneous and visceral adipose tissues (AT), other adipose depots are dispersed throughout the body and are found in close interaction with proximal organs such as mammary and periprostatic AT (MAT and PPAT respectively). These ATs have an effect on proximal organ function during physiological processes and diseases such as cancer. We highlighted here some of their most distinctive features in terms of tissular organization and responses to external stimuli and discussed how obesity affects them based on our current knowledge.

Human Omental Mature Adipocytes used as Paclitaxel Reservoir for Cell-Based Therapy in Ovarian Cancer

Primary human omental adipocytes and ovarian cancer(OC) cells establish a bidirectional communication in which tumor driven lipolysis is induced in adipocytes and the resulting fatty acids are delivered to cancer cells within the tumor microenvironment. Despite meaningful improvement in the treatment of OC, its efficacy is still limited by hydrophobicity and untargeted effects related to chemotherapeutics. Herein, omental adipocytes are firstly used as a reservoir for paclitaxel, named Living Paclitaxel Bullets (LPB) and secondly benefit from the established dialogue between adipocytes and cancer cells to engineer a drug delivery process that target specifically cancer cells. These results show that mature omental adipocytes can successfully uptake paclitaxel and deliver it to OC cells in a transwell coculture based in vitro model. In addition, the efficacy of this proof-of-concept has been demonstrated in vivo and induces a significant inhibition of tumor growth on a xenograft tumor model. The use of mature adipocytes can be suitable for clinical prospection in a cell-based therapy system, due to their mature and differentiated state, to avoid risks related to uncontrolled cell de novo proliferation capacity after the delivery of the antineoplastic drug as observed with other cell types when employed as drug carriers.

Multifactoral immune modulation potentiates durable remission in multiple models of aggressive malignancy

Tumors typically lack canonical danger signals required to activate adaptive immunity and also frequently employ substantial immunomodulatory mechanisms that downregulate adaptive responses and contribute to escape from immune surveillance. Given the variety of mechanisms involved in shielding tumors from immune recognition, it is not surprising that single-agent immunomodulatory approaches have been largely unsuccessful in generating durable antitumor responses. Here we report a unique combination of immunomodulatory and cytostatic agents that recondition the tumor microenvironment and eliminate complex and/or poor-prognosis tumor types including the non-immunogenic 4T-1 model of TNBC, the aggressive MOC-2 model of HNSCC, and the high-risk MYCN-amplified model of neuroblastoma. A course of therapy optimized for TNBC cured a majority of tumors in both ectopic and orthotopic settings and eliminated metastatic spread in all animals tested at the highest doses. Immune responses were transferable between therapeutic donor and naïve recipient through adoptive transfer, and a sizeable abscopal effect on distant, untreated lesions could be demonstrated experimentally. Similar results were observed in HNSCC and neuroblastoma models, with characteristic remodeling of the tumor microenvironment documented in all model systems. scRNA-seq analysis implicated upregulation of innate immune responses and antigen presentation in tumor cells and the myeloid cell compartment as critical early events. This analysis also highlighted the potential importance of the autonomic nervous system in the governance of inflammatory processes. The data indicate that the targeting of multiple pathways and mechanisms of action can result in substantial synergistic antitumor effects and suggest follow-up in the neoadjuvant setting may be warranted.

Nf1 deficiency modulates the stromal environment in the pretumorigenic rat mammary gland

Background

Neurofibromin, coded by the NF1 tumor suppressor gene, is the main negative regulator of the RAS pathway and is frequently mutated in various cancers. Women with Neurofibromatosis Type I (NF1)-a tumor predisposition syndrome caused by a germline NF1 mutation-have an increased risk of developing aggressive breast cancer with poorer prognosis. The mechanism by which NF1 mutations lead to breast cancer tumorigenesis is not well understood. Therefore, the objective of this work was to identify stromal alterations before tumor formation that result in the increased risk and poorer outcome seen among NF1 patients with breast cancer.

Approach

To accurately model the germline monoallelic NF1 mutations in NF1 patients, we utilized an Nf1-deficient rat model with accelerated mammary development before presenting with highly penetrant breast cancer.

Results

We identified increased collagen content in Nf1-deficient rat mammary glands before tumor formation that correlated with age of tumor onset. Additionally, gene expression analysis revealed that Nf1-deficient mature adipocytes in the rat mammary gland have increased collagen expression and shifted to a fibroblast and preadipocyte expression profile. This alteration in lineage commitment was also observed with in vitro differentiation, however, flow cytometry analysis did not show a change in mammary adipose-derived mesenchymal stem cell abundance.

Conclusion

Collectively, this study uncovered the previously undescribed role of Nf1 in mammary collagen deposition and regulating adipocyte differentiation. In addition to unraveling the mechanism of tumor formation, further investigation of adipocytes and collagen modifications in preneoplastic mammary glands will create a foundation for developing early detection strategies of breast cancer among NF1 patients.

Acylcarnitines promote gallbladder cancer metastasis through lncBCL2L11-THOC5-JNK axis

BACKGROUND

The progression of gallbladder cancer (GBC) is accompanied by abnormal fatty acid β-oxidation (FAO) metabolism. Different types of lipids perform various biological functions. This study aimed to determine the role of acyl carnitines in the molecular mechanisms of GBC progression.

METHODS

Distribution of lipids in GBC was described by LC-MS-based lipidomics. Cellular localization, expression level and full-length of lncBCL2L11 were detected using fluorescence in situ hybridization (FISH) assays, subcellular fractionation assay and 5' and 3' rapid amplification of the cDNA ends (RACE), respectively. In vitro and in vivo experiments were used to verify the biological function of lncBCL2L11 in GBC cells. Methylated RNA Immunoprecipitation (MeRIP) was performed to detect the methylation levels of lncBCL2L11. RNA pull-down assay and RNA immunoprecipitation (RIP) assay were used to identify lncBCL2L11 interacting proteins. Co-Immunoprecipitation (Co-IP) and Western blot assay were performed to validate the regulatory mechanism of lncBCL2L11 and THO complex.

RESULTS

Acylcarnitines were significantly up-regulated in GBC tissues. High serum triglycerides correlated to decreased survival in GBC patients and promoted tumor migration. LncBCL2L11 was identified in the joint analysis of highly metastatic cells and RNA sequencing data. LncBCl2L11 prevented the binding of THOC6 and THOC5 and causes the degradation of THOC5, thus promoting the accumulation of acylcarnitines in GBC cells, leading to the malignant progression of cancer cells. In addition, highly expressed acylcarnitines stabilized the expression of lncBCL2L11 through N6-methyladenosine methylation (m6A), forming a positive feedback regulation in tumor dissemination.

CONCLUSIONS

LncBCL2L11 is involved in gallbladder cancer metastasis through FAO metabolism. High lipid intake is associated with poor prognosis of GBC. Therefore, targeting lncBCL2L11 and its pathway-related proteins or reducing lipid intake may be significant for the treatment of GBC patients.

PA suppresses antitumor immunity of T cells by disturbing mitochondrial activity through Akt/mTOR-mediated Ca2+ flux

Deciphering the mechanisms behind how T cells become exhausted and regulatory T cells (Tregs) differentiate in a tumor microenvironment (TME) will significantly benefit cancer immunotherapy. A common metabolic alteration feature in TME is lipid accumulation, associated with T cell exhaustion and Treg differentiation. However, the regulatory role of free fatty acids (FFA) on T cell antitumor immunity has yet to be clearly illustrated. Our study observed that palmitic acid (PA), the most abundant saturated FFA in mouse plasma, enhanced T cell exhaustion and Tregs population in TME and increased tumor growth. In contrast, oleic acid (OA), a monounsaturated FFA, rescued PA-induced T cell exhaustion, decreased Treg population, and ameliorated T cell antitumor immunity in an obese mouse model. Mechanistically, mitochondrial metabolic activity is critical in maintaining T cell function, which PA attenuated. PA-induced T cell exhaustion and Treg formation depended on CD36 and Akt/mTOR-mediated calcium signaling. The study described a new mechanism of PA-induced downregulation of antitumor immunity of T cells and the therapeutic potential behind its restoration by targeting PA.

p53 deficient breast cancer cells reprogram preadipocytes toward tumor-protective immunomodulatory cells

The TP53 gene is mutated in approximately 30% of all breast cancer cases. Adipocytes and preadipocytes, which constitute a substantial fraction of the stroma of normal mammary tissue and breast tumors, undergo transcriptional, metabolic, and phenotypic reprogramming during breast cancer development and play an important role in tumor progression. We report here that p53 loss in breast cancer cells facilitates the reprogramming of preadipocytes, inducing them to acquire a unique transcriptional and metabolic program that combines impaired adipocytic differentiation with augmented cytokine expression. This, in turn, promotes the establishment of an inflammatory tumor microenvironment, including increased abundance of Ly6C+ and Ly6G+ myeloid cells and elevated expression of the immune checkpoint ligand PD-L1. We also describe a potential gain-of-function effect of common p53 missense mutations on the inflammatory reprogramming of preadipocytes. Altogether, our study implicates p53 deregulation in breast cancer cells as a driver of tumor-supportive adipose tissue reprogramming, expanding the network of non-cell autonomous mechanisms whereby p53 dysfunction may promote cancer. Further elucidation of the interplay between p53 and adipocytes within the tumor microenvironment may suggest effective therapeutic targets for the treatment of breast cancer patients.

MALDI-MSI of lipids in a model of breast cancer brain metastasis provides a surrogate measure of ischemia/hypoxia

Breast cancer brain metastasis (BCBM) has an incidence of 10-30%. It is incurable and the biological mechanisms that promote its progression remain largely undefined. Consequently, to gain insights into BCBM processes, we have developed a spontaneous mouse model of BCBM and in this study found a 20% penetrance of macro-metastatic brain lesion formation. Considering that lipid metabolism is indispensable to metastatic progression, our goal was the mapping of lipid distributions throughout the metastatic regions of the brain. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) of lipids revealed that, relative to surrounding brain tissue, seven long-chain (13-21 carbons long) fatty acylcarnitines, as well as two phosphatidylcholines, two phosphatidylinositols two diacylglycerols, a long-chain phosphatidylethanolamine, and a long-chain sphingomyelin were highly concentrated in the metastatic brain lesion In broad terms, lipids known to be enriched in brain tissues, such as very long-chain (≥ 22 carbons in length) polyunsaturated fatty acid of phosphatidylcholines, phosphatidylethanolamine, sphingomyelins, sulfatides, phosphatidylinositol phosphates, and galactosylceramides, were not found or only found in trace amounts in the metastatic lesion and instead consistently detected in surrounding brain tissues. The data, from this mouse model, highlights an accumulation of fatty acylcarnitines as possible biological makers of a chaotic inefficient vasculature within the metastasis, resulting in relatively inadequate blood flow and disruption of fatty acid β-oxidation due to ischemia/hypoxia.

The Different Mechanisms of Lipid Accumulation in Hepatocytes Induced by Oleic Acid/Palmitic Acid and High-Fat Diet

Non-alcoholic fatty liver disease (NAFLD) is the primary chronic liver disease worldwide, mainly manifested by hepatic steatosis. Hepatic lipids may be derived from dietary intake, plasma free fatty acid (FFA) uptake, or hepatic de novo lipogenesis (DNL). Currently, cellular and animal models of hepatocellular steatosis are widely used to study the pathogenesis of NAFLD and to investigate therapeutic agents. However, whether there are differences between the in vivo and in vitro models of the mechanisms that cause lipid accumulation has not been reported. We used OA/PA-induced NCTC 1469 cells and high-fat-diet-fed C57BL/6J mice to simulate a hepatocyte steatosis model of NAFLD and to detect indicators related to FFA uptake and DNL. In addition, when serological indicators were analysed in the mouse model, it was found that serum FASN levels decreased. The results revealed that, in the cellular model, indicators related to DNL were decreased, FASN enzyme activity was unchanged, and indicators related to FFA uptake were increased, including the high expression of CD36; while, in the animal model, indicators related to both FFA uptake and de novo synthesis were increased, including the high expression of CD36 and the increased protein levels of FASN with enhanced enzyme activity. In addition, after an analysis of the serological indicators in the mouse model, it was found that the serum levels of FASN were reduced. In conclusion, the OA/PA-induced cellular model can be used to study the mechanism of FFA uptake, whereas the high-fat-diet-induced mouse model can be used to study the mechanism of FFA uptake and DNL. Combined treatment with CD36 and FASN may be more effective against NAFLD. FASN in the serum can be used as one of the indicators for the clinical diagnosis of NAFLD.

Lipid metabolic reprogramming in tumor microenvironment: from mechanisms to therapeutics

Lipid metabolic reprogramming is an emerging hallmark of cancer. In order to sustain uncontrolled proliferation and survive in unfavorable environments that lack oxygen and nutrients, tumor cells undergo metabolic transformations to exploit various ways of acquiring lipid and increasing lipid oxidation. In addition, stromal cells and immune cells in the tumor microenvironment also undergo lipid metabolic reprogramming, which further affects tumor functional phenotypes and immune responses. Given that lipid metabolism plays a critical role in supporting cancer progression and remodeling the tumor microenvironment, targeting the lipid metabolism pathway could provide a novel approach to cancer treatment. This review seeks to: (1) clarify the overall landscape and mechanisms of lipid metabolic reprogramming in cancer, (2) summarize the lipid metabolic landscapes within stromal cells and immune cells in the tumor microenvironment, and clarify their roles in tumor progression, and (3) summarize potential therapeutic targets for lipid metabolism, and highlight the potential for combining such approaches with other anti-tumor therapies to provide new therapeutic opportunities for cancer patients.

Acidosis-induced regulation of adipocyte G0S2 promotes crosstalk between adipocytes and breast cancer cells as well as tumor progression

Bidirectional interactions between cancer cells and their microenvironment govern tumor progression. Among the stromal cells in this microenvironment, adipocytes have been reported to upregulate cancer cell migration and invasion by producing fatty acids. Conversely, cancer cells alter adipocyte phenotype notably via increased lipolysis. We aimed to identify the mechanisms through which cancer cells trigger adipocyte lipolysis and evaluate the functional consequences on cancer progression. Here, we show that cancer cell-induced acidification of the extracellular medium strongly promotes preadipocyte lipolysis through a mechanism that does not involve lipophagy but requires adipose triglyceride lipase (ATGL) activity. This increased lipolysis is triggered mainly by attenuation of the G0/G1 switch gene 2 (G0S2)-induced inhibition of ATGL. G0S2-mediated regulation in preadipocytes affects their communication with breast cancer cells, modifying the phenotype of the cancer cells and increasing their resistance to chemotherapeutic agents in vitro. Furthermore, we demonstrate that the adipocyte-specific overexpression of G0S2 impairs mammary tumor growth and lung metastasis formation in vivo. Our results highlight the importance of acidosis in cancer cell-adipocyte crosstalk and identify G0S2 as the main regulator of cancer-induced lipolysis, regulating tumor establishment and spreading.

Mutual impact of adipocytes and colorectal cancer cells growing in co-culture conditions

BACKGROUND

Colorectal cancer (CRC) is the third most common malignancy worldwide. CRC cells are situated in an adipocyte-rich microenvironment, which leads to interactions between adipocytes and CRC cells. Upon exposure to cancer cells, adipocytes transform into cancer-associated adipocytes (CAAs), and as a result, they gain features that promote tumor progression. The aim of this research was to shed more light on the detailed role of interactions between adipocytes and CRC cells associated with cancer progression in the context of these alterations.

METHODS

To implement adipocyte-CRC cell interaction, a co-culture model was applied. The analyses mainly focused on the metabolic modifications within CAAs and CRC cells, as well as the proliferation and migration potential of CRC cells. The impact of CRC on adipocytes was investigated by qRT-PCR analysis and Oil Red O staining. Proliferation and migration of CRC cells upon co-culture were tested with videomicroscopy, XTT, and a wound healing assay. Metabolic changes within CAAs and CRC cells were investigated based on lipid droplet formation, cell cycle analysis, gene and protein expression by qRT-PCR, and western blotting techniques.

RESULTS

CRC cells induced reprogramming of adipocytes into CAAs, which was connected with downregulation of lipid droplet formation in CAAs and alteration in adipocyte features. CAAs showed decreased metabolism-related gene expression, phosphorylation of Akt, ERK kinases, STAT3, and lactate secretion in comparison to the control. CAAs also promoted the migration, proliferation, and lipid droplet accumulation of CRC cells. After co-culturing with adipocytes, there was a shift to the G2/M phase of the cell cycle according to the differences in cyclin expression.

CONCLUSION

There are complex bidirectional interactions between adipocytes and CRC cells that may be connected with the induction of CRC cell progression. Video Abstract.

Lipid metabolism reprogramming in tumor-associated macrophages and implications for therapy

The tumormicroenvironment (TME) plays a key role in tumor progression. Tumor-associated macrophages (TAMs), which are natural immune cells abundantin the TME, are mainly divided into the anti-tumor M1 subtype and pro-tumor M2 subtype. Due to the high plasticity of TAMs, the conversion of the M1 to M2 phenotype in hypoxic and hypoglycemic TME promotes cancer progression, which is closely related to lipid metabolism. Key factors of lipid metabolism in TAMs, including peroxisome proliferator-activated receptor and lipoxygenase, promote the formation of a tumor immunosuppressive microenvironment and facilitate immune escape. In addition, tumor cells promote lipid accumulation in TAMs, causing TAMs to polarize to the M2 phenotype. Moreover, other factors of lipid metabolism, such as abhydrolase domain containing 5 and fatty acid binding protein, have both promoting and inhibiting effects on tumor cells. Therefore, further research on lipid metabolism in tumors is still required. In addition, statins, as core drugs regulating cholesterol metabolism, can inhibit lipid rafts and adhesion of tumor cells, which can sensitize them to chemotherapeutic drugs. Clinical studies on simvastatin and lovastatin in a variety of tumors are underway. This article provides a comprehensive review of the role of lipid metabolism in TAMs in tumor progression, and provides new ideas for targeting lipid metabolism in tumor therapy.

A novel 3D culture model for human primary mammary adipocytes to study their metabolic crosstalk with breast cancer in lean and obese conditions

Obesity is a negative prognosis factor for breast cancer. Yet, the biological mechanisms underlying this effect are still largely unknown. An emerging hypothesis is that the transfer of free fatty acids (FFA) between adipocytes and tumor cells might be altered under obese conditions, contributing to tumor progression. Currently there is a paucity of models to study human mammary adipocytes (M-Ads)-cancer crosstalk. As for other types of isolated white adipocytes, herein, we showed that human M-Ads die within 2-3 days by necrosis when grown in 2D. As an alternative, M-Ads were grown in a fibrin matrix, a 3D model that preserve their distribution, integrity and metabolic function for up to 5 days at physiological glucose concentrations (5 mM). Higher glucose concentrations frequently used in in vitro models promote lipogenesis during M-Ads culture, impairing their lipolytic function. Using transwell inserts, the matrix embedded adipocytes were cocultured with breast cancer cells. FFA transfer between M-Ads and cancer cells was observed, and this event was amplified by obesity. Together these data show that our 3D model is a new tool for studying the effect of M-Ads on tumor cells and beyond with all the components of the tumor microenvironment including the immune cells.

Tumor microenvironment in ovarian cancer peritoneal metastasis

Ovarian cancer (OC) is one of the most common gynecological malignancies with high morbidity and mortality. The peritoneum is one of the most common metastatic sites in ovarian cancer, involving large amounts of ascites. However, its mechanism is unclear. The peritoneal microenvironment composed of peritoneal effusion and peritoneum creates favorable conditions for ovarian cancer progression and metastasis. Here, we reviewed the peritoneal metastasis patterns and molecular mechanisms of ovarian cancer, as well as major components of the peritoneal microenvironment, peritoneal effusion, and immune microenvironment, and investigated the relationship between the peritoneal microenvironment and ovarian cancer metastasis.

Emphasis on Adipocyte Transformation: Anti-Inflammatory Agents to Prevent the Development of Cancer-Associated Adipocytes

Of the various cell types in the tumor microenvironment (TME), adipocytes undergo a dynamic transformation when activated by neighboring cancer cells. Although these adipocytes, known as cancer-associated adipocytes (CAAs), have been reported to play a crucial role in tumor progression, the factors that mediate their transformation remain elusive. In this review, we discuss the hypothesis that inflammatory signals involving NF-ĸB activation can induce lipolysis and adipocyte dedifferentiation. This provides a mechanistic understanding of CAA formation and introduces the concept of preventing adipocyte transformation via anti-inflammatory agents. Indeed, epidemiological studies indicate a higher efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) in obese patients with cancer, suggesting that NSAIDs can modulate the TME. Inhibition of cyclooxygenase-2 (COX-2) and prostaglandin production leads to the suppression of inflammatory signals such as NF-ĸB. Thus, we suggest the use of NSAIDs in cancer patients with metabolic disorders to prevent the transformation of TME components. Moreover, throughout this review, we attempt to expand our knowledge of CAA transformation to improve the clinical feasibility of targeting CAAs.

Lipid Metabolism Heterogeneity and Crosstalk with Mitochondria Functions Drive Breast Cancer Progression and Drug Resistance

Breast cancer (BC) is a heterogeneous disease that can be triggered by genetic alterations in mammary epithelial cells, leading to diverse disease outcomes in individual patients. The metabolic heterogeneity of BC enhances its ability to adapt to changes in the tumor microenvironment and metabolic stress, but unfavorably affects the patient's therapy response, prognosis and clinical effect. Extrinsic factors from the tumor microenvironment and the intrinsic parameters of cancer cells influence their mitochondrial functions, which consequently alter their lipid metabolism and their ability to proliferate, migrate and survive in a harsh environment. The balanced interplay between mitochondria and fatty acid synthesis or fatty acid oxidation has been attributed to a combination of environmental factors and to the genetic makeup, oncogenic signaling and activities of different transcription factors. Hence, understanding the mechanisms underlying lipid metabolic heterogeneity and alterations in BC is gaining interest as a major target for drug resistance. Here we review the major recent reports on lipid metabolism heterogeneity and bring to light knowledge on the functional contribution of diverse lipid metabolic pathways to breast tumorigenesis and therapy resistance.

The crosstalk within the breast tumor microenvironment in type II diabetes: Implications for cancer disparities

Obesity-driven (type 2) diabetes (T2D), the most common metabolic disorder, both increases the incidence of all molecular subtypes of breast cancer and decreases survival in postmenopausal women. Despite this clear link, T2D and the associated dysfunction of diverse tissues is often not considered during the standard of care practices in oncology and, moreover, is treated as exclusion criteria for many emerging clinical trials. These guidelines have caused the biological mechanisms that associate T2D and breast cancer to be understudied. Recently, it has been illustrated that the breast tumor microenvironment (TME) composition and architecture, specifically the surrounding cellular and extracellular structures, dictate tumor progression and are directly relevant for clinical outcomes. In addition to the epithelial cancer cell fraction, the breast TME is predominantly made up of cancer-associated fibroblasts, adipocytes, and is often infiltrated by immune cells. During T2D, signal transduction among these cell types is aberrant, resulting in a dysfunctional breast TME that communicates with nearby cancer cells to promote oncogenic processes, cancer stem-like cell formation, pro-metastatic behavior and increase the risk of recurrence. As these cells are non-malignant, despite their signaling abnormalities, data concerning their function is never captured in DNA mutational databases, thus we have limited insight into mechanism from publicly available datasets. We suggest that abnormal adipocyte and immune cell exhaustion within the breast TME in patients with obesity and metabolic disease may elicit greater transcriptional plasticity and cellular heterogeneity within the expanding population of malignant epithelial cells, compared to the breast TME of a non-obese, metabolically normal patient. These challenges are particularly relevant to cancer disparities settings where the fraction of patients seen within the breast medical oncology practice also present with co-morbid obesity and metabolic disease. Within this review, we characterize the changes to the breast TME during T2D and raise urgent molecular, cellular and translational questions that warrant further study, considering the growing prevalence of T2D worldwide.

Molecular, cellular and systemic aspects of epithelial ovarian cancer and its tumor microenvironment

Ovarian cancer encompasses a heterogeneous group of malignancies that involve the ovaries, fallopian tubes and the peritoneal cavity. Despite major advances made within the field of cancer, the majority of patients with ovarian cancer are still being diagnosed at an advanced stage of the disease due to lack of effective screening tools. The overall survival of these patients has, therefore, not substantially improved over the past decades. Most patients undergo debulking surgery and treatment with chemotherapy, but often micrometastases remain and acquire resistance to the therapy, eventually leading to disease recurrence. Here, we summarize the current knowledge in epithelial ovarian cancer development and metastatic progression. For the most common subtypes, we focus further on the properties and functions of the immunosuppressive tumor microenvironment, including the extracellular matrix. Current and future treatment modalities are discussed and finally we provide an overview of the different experimental models used to develop novel therapies.

Activation of Drp1 promotes fatty acids-induced metabolic reprograming to potentiate Wnt signaling in colon cancer

Cancer cells are known for their ability to adapt variable metabolic programs depending on the availability of specific nutrients. Our previous studies have shown that uptake of fatty acids alters cellular metabolic pathways in colon cancer cells to favor fatty acid oxidation. Here, we show that fatty acids activate Drp1 to promote metabolic plasticity in cancer cells. Uptake of fatty acids (FAs) induces mitochondrial fragmentation by promoting ERK-dependent phosphorylation of Drp1 at the S616 site. This increased phosphorylation of Drp1 enhances its dimerization and interaction with Mitochondrial Fission Factor (MFF) at the mitochondria. Consequently, knockdown of Drp1 or MFF attenuates fatty acid-induced mitochondrial fission. In addition, uptake of fatty acids triggers mitophagy via a Drp1- and p62-dependent mechanism to protect mitochondrial integrity. Moreover, results from metabolic profiling analysis reveal that silencing Drp1 disrupts cellular metabolism and blocks fatty acid-induced metabolic reprograming by inhibiting fatty acid utilization. Functionally, knockdown of Drp1 decreases Wnt/β-catenin signaling by preventing fatty acid oxidation-dependent acetylation of β-catenin. As a result, Drp1 depletion inhibits the formation of tumor organoids in vitro and xenograft tumor growth in vivo. Taken together, our study identifies Drp1 as a key mediator that connects mitochondrial dynamics with fatty acid metabolism and cancer cell signaling.

Interplay between Prostate Cancer and Adipose Microenvironment: A Complex and Flexible Scenario

Adipose tissue is part of the prostate cancer (PCa) microenvironment not only in the periprostatic area, but also in the most frequent metastatic sites, such as bone marrow and pelvic lymph nodes. The involvement of periprostatic adipose tissue (PPAT) in the aggressiveness of PCa is strongly suggested by numerous studies. Many molecules play a role in the reciprocal interaction between adipocytes and PCa cells, including adipokines, hormones, lipids, and also lipophilic pollutants stored in adipocytes. The crosstalk has consequences not only on cancer cell growth and metastatic potential, but also on adipocytes. Although most of the molecules released by PPAT are likely to promote tumor growth and the migration of cancer cells, others, such as the adipokine adiponectin and the n-6 or n-3 polyunsaturated fatty acids (PUFAs), have been shown to have anti-tumor properties. The effects of PPAT on PCa cells might therefore depend on the balance between the pro- and anti-tumor components of PPAT. In addition, genetic and environmental factors involved in the risk and/or aggressiveness of PCa, including obesity and diet, are able to modulate the interactions between PPAT and cancer cells and their consequences on the growth and the metastatic potential of PCa.

Targeting Strategies for Aberrant Lipid Metabolism Reprogramming and the Immune Microenvironment in Esophageal Cancer: A Review

Esophageal cancer is of high importance to occurrence, development, and treatment resistance. As evidenced by recent studies, pathways (e.g., Wnt/β-catenin, AMPK, and Hippo) are critical to the proliferation, differentiation, and self-renewal of esophageal cancer. In addition, the above pathways play a certain role in regulating esophageal cancer and act as potential therapeutic targets. Over the past few years, the function of lipid metabolism in controlling tumor cells and immune cells has aroused extensive attention. It has been reported that there are intricate interactions between lipid metabolism reprogramming between immune and esophageal cancer cells, whereas molecular mechanisms should be studied in depth. Immune cells have been commonly recognized as a vital player in the esophageal cancer microenvironment, having complex crosstalk with cancer cells. It is increasingly evidenced that the function of immune cells in the tumor microenvironment (TME) is significantly correlated with abnormal lipid metabolism. In this review, the latest findings in lipid metabolism reprogramming in TME are summarized, and the above findings are linked to esophageal cancer progression. Aberrant lipid metabolism and associated signaling pathways are likely to serve as a novel strategy to treat esophageal cancer through lipid metabolism reprogramming.

Altered Adipokine Expression in Tumor Microenvironment Promotes Development of Triple Negative Breast Cancer

Obesity is a remarkably important factor for breast carcinogenesis and aggressiveness. The implication of increased BMI in triple negative breast cancer (TNBC) development is also well established. A malignancy-promoting role of the adipose tissue has been supposed, where the adipocytes that constitute the majority of stromal cells release pro-inflammatory cytokines and growth factors. Alterations in adipokines and their receptors play significant roles in breast cancer initiation, progression, metastasis, and drug response. Classic adipokines, such as leptin, adiponectin, and resistin, have been extensively studied in breast cancer and connected with breast cancer risk and progression. Notably, new molecules are constantly being discovered and the list is continuously growing. Additionally, substantial progress has been made concerning their differential expression in association with clinical and pathological parameters of tumors and the prognostic and predictive value of their dysregulation in breast cancer carcinogenesis. However, evidence regarding the mechanisms by which adipose tissue is involved in the development of TNBC is lacking. In the present article we comment on current data on the suggested involvement of these mediators in breast cancer development and progression, with particular emphasis on TNBC, to draw attention to the design of novel targeted therapies and biomarkers.

Lipids in cancer: a global view of the contribution of lipid pathways to metastatic formation and treatment resistance

Lipids are essential constituents for malignant tumors, as they are absolutely required for tumor growth and dissemination. Provided by the tumor microenvironment (TME) or by cancer cells themselves through activation of de novo synthesis pathways, they orchestrate a large variety of pro-tumorigenic functions. Importantly, TME cells, especially immune cells, cancer-associated fibroblasts (CAFs) and cancer-associated adipocytes (CAAs), are also prone to changes in their lipid content, which hinder or promote tumor aggressiveness. In this review, we address the significant findings for lipid contribution in tumor progression towards a metastatic disease and in the poor response to therapeutic treatments. We also highlight the benefits of targeting lipid pathways in preclinical models to slow down metastasis development and overcome chemo-and immunotherapy resistance.

Comprehensive Analysis Identifies and Validates the Tumor Microenvironment Subtypes to Predict Anti-Tumor Therapy Efficacy in Hepatocellular Carcinoma

Objective

The objective of this study was to explore and verify the subtypes in hepatocellular carcinoma based on the immune (lymphocyte and myeloid cells), stem, and stromal cells in the tumor microenvironment and analyze the biological characteristics and potential relevance of each cluster.

Methods

We used the xCell algorithm to calculate cell scores and got subtypes by k-means clustering. In the external validation sets, we verified the conclusion stability by a neural network model. Simultaneously, we speculated the inner connection between clusters by pseudotime trajectory analysis and confirmed it by pathway enrichment, TMB, CNV, etc., analysis.

Result

According to the results of the consensus cluster, we chose k = 4 as the optimal value and got four different subtypes (C1, C2, C3, and C4) with different biological characteristics based on infiltrating levels of 48 cells in TME. In univariable Cox regression, the hazard ratio (HR) value of C3 versus C1 was 2.881 (95% CI: 1.572–5.279); in multivariable Cox regression, we corrected the age and TNM stage, and the HR value of C3 versus C1 was 2.510 (95% CI: 1.339–4.706). C1 and C2 belonged to the immune-active type, C3 and C4 related to the immune-insensitive type and the potential conversion relationships between clusters. We established a neural network model, and the area under the curves of the neural network model was 0.949 in the testing cohort; the same survival results were also observed in the external validation set. We compared the differences in cell infiltration, immune function, pathway enrichment, TMB, and CNV of four clusters and speculated that C1 and C2 were more likely to benefit from immunotherapy and C3 may benefit from FGF inhibitors.

Discussion

Our analysis provides a new approach for the identification of four tumor microenvironment clusters in patients with liver cancer and identifies the biological differences and predicts the immunotherapy efficacy between the four subtypes.

The role of bone marrow adipocytes in cancer progression: the impact of obesity

Bone marrow adipose tissues (BMATs) and their main cellular component, bone marrow adipocytes (BMAds), are found within the bone marrow (BM), which is a niche for the development of hematological malignancies as well as bone metastasis from solid tumors such as breast and prostate cancers. In humans, BMAds are present within the hematopoietic or "red" BMAT and in the "yellow" BMAT where they are more densely packed. BMAds are emerging as new actors in tumor progression; however, there are many outstanding questions regarding their precise role. In this review, we summarized our current knowledge regarding the development, distribution, and regulation by external stimuli of the BMATs in mice and humans and addressed how obesity could affect these traits. We then discussed the specific metabolic phenotype of BMAds that appear to be different from "classical" white adipocytes, since they are devoid of lipolytic function. According to this characterization, we presented how tumor cells affect the in vitro and in vivo phenotype of BMAds and the signals emanating from BMAds that are susceptible to modulate tumor behavior with a specific emphasis on their metabolic crosstalk with cancer cells. Finally, we discussed how obesity could affect this crosstalk. Deciphering the role of BMAds in tumor progression would certainly lead to the identification of new targets in oncology in the near future.

Lipid metabolism-related lncRNA SLC25A21-AS1 promotes the progression of oesophageal squamous cell carcinoma by regulating the NPM1/c-Myc axis and SLC25A21 expression

BACKGROUND

Obesity alters metabolic microenvironment and is thus associated with several tumours. The aim of the present study was to investigate the role, molecular mechanism of action, and potential clinical value of lipid metabolism-related long non-coding RNA (lncRNA) SLC25A21-AS1 in oesophageal squamous cell carcinoma (ESCC).

METHODS

A high-fat diets (HFDs)-induced obesity nude mouse model was established, and targeted metabolomics analysis was used to identify critical medium-long chain fatty acids influencing the growth of ESCC cells. Transcriptomic analysis of public dataset GSE53625 confirmed that lncRNA SLC25A21-AS1 was a lipid metabolism-related lncRNA. The biological function of lncRNA SLC25A21-AS1 in ESCC was investigated both in vivo and in vitro. Chromatin immunoprecipitation(ChIP)assay, RNA-pull down, mass spectrometry, co-IP, and RNA IP(RIP) were performed to explore the molecular mechanism. Finally, an ESCC cDNA microarray was used to determine the clinical prognostic value of SLC25A21-AS1 by RT-qPCR.

RESULTS

Palmitic acid (PA) is an important fatty acid component of HFD and had an inhibitory effect on ESCC cell lines. LncRNA SLC25A21-AS1 expression was downregulated by PA and associated with the proliferation and migration of ESCC cells in vitro and in vivo. Mechanistically, SLC25A21-AS1 interacted with nucleophosmin-1 (NPM1) protein to promote the downstream gene transcription of the c-Myc in the nucleus. In the cytoplasm, SLC25A21-AS1 maintained the stability of SLC25A21 mRNA and reduced the intracellular NAD+ /NADH ratio by influencing tryptophan catabolism. Finally, we demonstrated that high expression of SLC25A21-AS1 promoted resistance to cisplatin-induced apoptosis and was correlated with poor tumour grade and overall survival.

CONCLUSIONS

HFD/PA has an inhibitory effect on ESCC cells and SLC25A21-AS1 expression. SLC25A21-AS1 promotes the proliferation and migration of ESCC cells by regulating the NPM1/c-Myc axis and SLC25A21 expression. In addition, lncRNA SLC25A21-AS1 may serve as a favourable prognostic biomarker and a potential therapeutic target for ESCC.

EGCG Prevents the Onset of an Inflammatory and Cancer-Associated Adipocyte-like Phenotype in Adipose-Derived Mesenchymal Stem/Stromal Cells in Response to the Triple-Negative Breast Cancer Secretome

Background: Triple-negative breast cancer (TNBC) cells secretome induces a pro-inflammatory microenvironment within the adipose tissue, which hosts both mature adipocytes and adipose-derived mesenchymal stem/stromal cells (ADMSC). The subsequent acquisition of a cancer-associated adipocyte (CAA)-like phenotype is, however, unknown in ADMSC. While epidemiological studies suggest that consuming a polyphenol-rich diet reduces the incidence of some obesity-related cancers, the chemopreventive impact of green tea-derived epigallocatechin-3-gallate (EGCG) against the cues that trigger the CAA phenotype remain undocumented in ADMSC. Methods: Human ADMSC were exposed to human TNBC-derived MDA-MB-231 conditioned media (TNBC cells secretome) supplemented or not with EGCG. Differential gene expression was assessed through RNA-Seq analysis and confirmed by RT-qPCR. Protein expression levels and the activation status of signal transduction pathways mediators were determined by Western blotting. ADMSC chemotaxis was assessed by a real-time cell migration assay. Results: The TNBC cells secretome induced in ADMSC the expression of the CAA cytokines CCL2, CCL5, IL-1β, and IL-6, and of immunomodulators COX2, HIF-1α, VEGFα, and PD-L1. The epithelial-to-mesenchymal biomarker Snail was found to control the CAA phenotype. EGCG inhibited the induction of CAA genes and the activation status of Smad2 and NF-κB. The induced chemotactic response was also inhibited by EGCG. Conclusion: The induction of an inflammatory and CAA-like phenotype in ADMSC can be triggered by the TNBC cells secretome, while still efficiently prevented by diet-derived polyphenols.

Metabolic dysregulation and emerging therapeutical targets for hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is an aggressive human cancer with increasing incidence worldwide. Multiple efforts have been made to explore pharmaceutical therapies to treat HCC, such as targeted tyrosine kinase inhibitors, immune based therapies and combination of chemotherapy. However, limitations exist in current strategies including chemoresistance for instance. Tumor initiation and progression is driven by reprogramming of metabolism, in particular during HCC development. Recently, metabolic associated fatty liver disease (MAFLD), a reappraisal of new nomenclature for non-alcoholic fatty liver disease (NAFLD), indicates growing appreciation of metabolism in the pathogenesis of liver disease, including HCC, thereby suggesting new strategies by targeting abnormal metabolism for HCC treatment. In this review, we introduce directions by highlighting the metabolic targets in glucose, fatty acid, amino acid and glutamine metabolism, which are suitable for HCC pharmaceutical intervention. We also summarize and discuss current pharmaceutical agents and studies targeting deregulated metabolism during HCC treatment. Furthermore, opportunities and challenges in the discovery and development of HCC therapy targeting metabolism are discussed.

Endocannabinoid System and Tumour Microenvironment: New Intertwined Connections for Anticancer Approaches

The tumour microenvironment (TME) is now recognised as a hallmark of cancer, since tumour:stroma crosstalk supports the key steps of tumour growth and progression. The dynamic co-evolution of the tumour and stromal compartments may alter the surrounding microenvironment, including the composition in metabolites and signalling mediators. A growing number of evidence reports the involvement of the endocannabinoid system (ECS) in cancer. ECS is composed by a complex network of ligands, receptors, and enzymes, which act in synergy and contribute to several physiological but also pathological processes. Several in vitro and in vivo evidence show that ECS deregulation in cancer cells affects proliferation, migration, invasion, apoptosis, and metastatic potential. Although it is still an evolving research, recent experimental evidence also suggests that ECS can modulate the functional behaviour of several components of the TME, above all the immune cells, endothelial cells and stromal components. However, the role of ECS in the tumour:stroma interplay remains unclear and research in this area is particularly intriguing. This review aims to shed light on the latest relevant findings of the tumour response to ECS modulation, encouraging a more in-depth analysis in this field. Novel discoveries could be promising for novel anti-tumour approaches, targeting the microenvironmental components and the supportive tumour:stroma crosstalk, thereby hindering tumour development.

Tumour fatty acid metabolism in the context of therapy resistance and obesity

Fatty acid metabolism is known to support tumorigenesis and disease progression as well as treatment resistance through enhanced lipid synthesis, storage and catabolism. More recently, the role of membrane fatty acid composition, for example, ratios of saturated, monounsaturated and polyunsaturated fatty acids, in promoting cell survival while limiting lipotoxicity and ferroptosis has been increasingly appreciated. Alongside these insights, it has become clear that tumour cells exhibit plasticity with respect to fatty acid metabolism, responding to extratumoural and systemic metabolic signals, such as obesity and cancer therapeutics, to promote the development of aggressive, treatment-resistant disease. Here, we describe cellular fatty acid metabolic changes that are connected to therapy resistance and contextualize obesity-associated changes in host fatty acid metabolism that likely influence the local tumour microenvironment to further modify cancer cell behaviour while simultaneously creating potential new vulnerabilities.

MCF-7 Drug Resistant Cell Lines Switch Their Lipid Metabolism to Triple Negative Breast Cancer Signature

Obesity and adipose tissue have been closely related to a poor cancer prognosis, especially in prostate and breast cancer patients. The ability of transferring lipids from the adipose tissue to the tumor cells is actively linked to tumor progression. However, different types of breast tumor seem to use these lipids in different ways and metabolize them in different pathways. In this study we have tracked by mass spectrometry how palmitic acid from the adipocytes is released to media being later incorporated in different breast cancer cell lines (MDA-MB-231, SKBR3, BT474, MCF-7 and its resistant MCF-7 EPI^R and MCF-7 TAX^R). We have observed that different lines metabolize the palmitic acid in a different way and use their carbons in the synthesis of different new lipid families. Furthermore, we have observed that the lipid synthesis pattern varied according to the cell line. Surprisingly, the metabolic pattern of the resistant cells was more related to the TNBC cell line compared to their sensitive cell line MCF-7. These results allow us to determine a specific lipid pattern in different cell lines that later might be used in breast cancer diagnosis and to find a better treatment according to the cancer molecular type.

Lipid droplet evolution gives insight into polyaneuploid cancer cell lipid droplet functions

Lipid droplets (LDs) are found throughout all phyla across the tree of life. Originating as pure energy stores in the most basic organisms, LDs have evolved to fill various roles as regulators of lipid metabolism, signaling, and trafficking. LDs have been noted in cancer cells and have shown to increase tumor aggressiveness and chemotherapy resistance. A certain transitory state of cancer cell, the polyaneuploid cancer cell (PACC), appears to have higher LD levels than the cancer cell from which they are derived. PACCs are postulated to be the mediators of metastasis and resistance in many different cancers. Utilizing the evolutionarily conserved roles of LDs to protect from cellular lipotoxicity allows PACCs to survive otherwise lethal stressors. By better understanding how LDs have evolved throughout different phyla we will identify opportunities to target LDs in PACCs to increase therapeutic efficiency in cancer cells.

Skeletal Muscle-Adipose Tissue-Tumor Axis: Molecular Mechanisms Linking Exercise Training in Prostate Cancer

Increased visceral adiposity may influence the development of prostate cancer (PCa) aggressive tumors and cancer mortality. White adipose tissue (WAT), usually referred to as periprostatic adipose tissue (PPAT), surrounds the prostatic gland and has emerged as a potential mediator of the tumor microenvironment. Exercise training (ET) induces several adaptations in both skeletal muscle and WAT. Some of these effects are mediated by ET-induced synthesis and secretion of several proteins, known as myo- and adipokines. Together, myokines and adipokines may act in an endocrine-like manner to favor communication between skeletal muscle and WAT, as they may work together to improve whole-body metabolic health. This crosstalk may constitute a potential mechanism by which ET exerts its beneficial role in the prevention and treatment of PCa-related disorders; however, this has not yet been explored. Therefore, we reviewed the current evidence on the effects of skeletal muscle–WAT–tumor crosstalk in PCa, and the potential mediators of this process to provide a better understanding of underlying ET-related mechanisms in cancer.

Cancer-Associated Adipocytes in Breast Cancer: Causes and Consequences

Breast cancer progression is highly dependent on the heterotypic interaction between tumor cells and stromal cells of the tumor microenvironment. Cancer-associated adipocytes (CAAs) are emerging as breast cancer cell partners favoring proliferation, invasion, and metastasis. This article discussed the intersection between extracellular signals and the transcriptional cascade that regulates adipocyte differentiation in order to appreciate the molecular pathways that have been described to drive adipocyte dedifferentiation. Moreover, recent studies on the mechanisms through which CAAs affect the progression of breast cancer were reviewed, including adipokine regulation, metabolic reprogramming, extracellular matrix remodeling, and immune cell modulation. An in-depth understanding of the complex vicious cycle between CAAs and breast cancer cells is crucial for designing novel strategies for new therapeutic interventions.

The Chemokine Receptor CCR3 Is Potentially Involved in the Homing of Prostate Cancer Cells to Bone: Implication of Bone-Marrow Adipocytes

Bone metastasis remains the most frequent and the deadliest complication of prostate cancer (PCa). Mechanisms leading to the homing of tumor cells to bone remain poorly characterized. Role of chemokines in providing navigational cues to migrating cancer cells bearing specific receptors is well established. Bone is an adipocyte-rich organ since 50 to 70% of the adult bone marrow (BM) volume comprise bone marrow adipocytes (BM-Ads), which are likely to produce chemokines within the bone microenvironment. Using in vitro migration assays, we demonstrated that soluble factors released by human primary BM-Ads are able to support the directed migration of PCa cells in a CCR3-dependent manner. In addition, we showed that CCL7, a chemokine previously involved in the CCR3-dependent migration of PCa cells outside of the prostate gland, is released by human BM-Ads. These effects are amplified by obesity and ageing, two clinical conditions known to promote aggressive and metastatic PCa. In human tumors, we found an enrichment of CCR3 in bone metastasis vs. primary tumors at mRNA levels using Oncomine microarray database. In addition, immunohistochemistry experiments demonstrated overexpression of CCR3 in bone versus visceral metastases. These results underline the potential importance of BM-Ads in the bone metastatic process and imply a CCR3/CCL7 axis whose pharmacological interest needs to be evaluated.

Deconstructing tumor heterogeneity: the stromal perspective

Significant advances have been made towards understanding the role of immune cell-tumor interplay in either suppressing or promoting tumor growth, progression, and recurrence, however, the roles of additional stromal elements, cell types and/or cell states remain ill-defined. The overarching goal of this NCI-sponsored workshop was to highlight and integrate the critical functions of non-immune stromal components in regulating tumor heterogeneity and its impact on tumor initiation, progression, and resistance to therapy. The workshop explored the opposing roles of tumor supportive versus suppressive stroma and how cellular composition and function may be altered during disease progression. It also highlighted microenvironment-centered mechanisms dictating indolence or aggressiveness of early lesions and how spatial geography impacts stromal attributes and function. The prognostic and therapeutic implications as well as potential vulnerabilities within the heterogeneous tumor microenvironment were also discussed. These broad topics were included in this workshop as an effort to identify current challenges and knowledge gaps in the field.

Microenvironmental Aspartate Preserves Leukemic Cells from Therapy-Induced Metabolic Collapse

Metabolic dialogue between tumors and their microenvironment emerges as a key regulator of chemoresistance, the major barrier for the treatment of several cancers. In this issue of Cell Metabolism, van Gastel et al. decipher the pivotal role of stromal glutamine-derived aspartate to sustain pyrimidine biosynthesis in chemoresistant acute myeloid leukemia (AML) and thus state it as a target for anti-cancer therapy.

Lipid Droplets in Cancer

Lipid droplets have a unique structure among organelles consisting of a dense hydrophobic core of neutral lipids surrounded by a single layer of phospholipids decorated with various proteins. Often labeled merely as passive fat storage repositories, they in fact have a remarkably dynamic life cycle. Being formed within the endoplasmic reticulum membrane, lipid droplets rapidly grow, shrink, traverse the cytosol, and engage in contacts with other organelles to exchange proteins and lipids. Their lipid and protein composition changes dynamically in response to cellular states and nutrient availability. Remarkably, their biogenesis is induced when cells experience various forms of nutrient, energy, and redox imbalances, including lipid excess and complete nutrient deprivation. Cancer cells are continuously exposed to nutrient and oxygen fluctuations and have the capacity to switch between alternative nutrient acquisition and metabolic pathways in order to strive even during severe stress. Their supply of lipids is ensured by a series of nutrient uptake and scavenging mechanisms, upregulation of de novo lipid synthesis, repurposing of their structural lipids via enzymatic remodeling, or lipid recycling through autophagy. Importantly, most of these pathways of lipid acquisition converge at lipid droplets, which combine different lipid fluxes and control their usage based on specific cellular needs. It is thus not surprising that lipid droplet breakdown is an elaborately regulated process that occurs via a complex interplay of neutral lipases and autophagic degradation. Cancer cells employ lipid droplets to ensure energy production and redox balance, modulate autophagy, drive membrane synthesis, and control its composition, thereby minimizing stress and fostering tumor progression. As regulators of (poly)unsaturated fatty acid trafficking, lipid droplets are also emerging as modulators of lipid peroxidation and sensitivity to ferroptosis. Clearly, dysregulated lipid droplet turnover may also be detrimental to cancer cells, which should provide potential therapeutic opportunities in the future. In this review, we explore how lipid droplets consolidate lipid acquisition and trafficking pathways in order to match lipid supply with the requirements for cancer cell survival, growth, and metastasis.