Enhancing Fatty Acid Catabolism of Macrophages Within Aberrant Breast Cancer Tumor Microenvironment Can Re-establish Antitumor Function

Serine enrichment in tumors promotes regulatory T cell accumulation through sphinganine-mediated regulation of c-Fos

CD4+ regulatory T (Treg) cells accumulate in the tumor microenvironment (TME) and suppress the immune system. Whether and how metabolite availability in the TME influences Treg cell differentiation is not understood. Here, we measured 630 metabolites in the TME and found that serine and palmitic acid, substrates required for the synthesis of sphingolipids, were enriched. A serine-free diet or a deficiency in Sptlc2, the rate-limiting enzyme catalyzing sphingolipid synthesis, suppressed Treg cell accumulation and inhibited tumor growth. Sphinganine, an intermediate metabolite in sphingolipid synthesis, physically interacted with the transcription factor c-Fos. Sphinganine c-Fos interactions enhanced the genome-wide recruitment of c-Fos to regions near the transcription start sites of target genes including Pdcd1 (encoding PD-1), which promoted Pdcd1 transcription and increased inducible Treg cell differentiation in vitro in a PD-1-dependent manner. Thus, Sptlc2-mediated sphingolipid synthesis translates the extracellular information of metabolite availability into nuclear signals for Treg cell differentiation and limits antitumor immunity.

Targeting molecular cross-talk between tumor cells and tumor associated macrophage as therapeutic strategy in triple negative breast cancer

Triple-negative Breast cancer (TNBC) is a subtype of breast cancer (BC) that lacks expression for ER/PR/Her2 receptors and is associated with aggressive disease pathogenesis and the worst prognosis among other subtypes of BC. Accumulating evidence-based studies indicate the high immunogenic ability of TNBC tumors and the applicability of immunotherapeutic strategies to overcome therapy resistance and tumor recurrence in TNBC patients. However, not all TNBC patients respond equally well to current immunotherapies that mainly target the adaptive immune system for tumor rejection. Recent studies are contemplating the efficacy of tumor-associated macrophage (TAM) targeted therapies since these subpopulations of cells comprise one of the major components of tumor-infiltrating immune cells (TIIs) in the TNBC tumor microenvironment (TME) and play an essential role in priming the adaptive immune response mediators towards both antitumorigenic and pro-tumorigenic response facilitated by intercellular cross-talk between tumor cells and TAM populations present within TNBC-TME. The present review discusses these molecular mechanisms and their consequence on the progression of TNBC tumors. Also, the therapeutic strategies targeting candidate genes/pathways involved in molecular cross-talk between TAM-TNBC cells and their impact on the development and progression of TNBC tumors are also discussed.

The emerging role of PPAR-alpha in breast cancer

Breast cancer has been confirmed to have lipid disorders in the tumour microenvironment. Peroxisome proliferator-activated receptor alpha (PPARα) is a ligand-activated transcriptional factor that belongs to the family of nuclear receptors. PPARα regulates the expression of genes involved in fatty acid homeostasis and is a major regulator of lipid metabolism. Because of its effects on lipid metabolism, an increasing number of studies have investigated the relationship of PPARα with breast cancer. PPARα has been shown to impact the cell cycle and apoptosis in normal cells and tumoral cells through regulating genes of the lipogenic pathway, fatty acid oxidation, fatty acid activation, and uptake of exogenous fatty acids. Besides, PPARα is involved in the regulation of the tumour microenvironment (anti-inflammation and inhibition of angiogenesis) by modulating different signal pathways such as NF-κB and PI3K/AKT/mTOR. Some synthetic PPARα ligands are used in adjuvant therapy for breast cancer. PPARα agonists are reported to reduce the side effects of chemotherapy and endocrine therapy. In addition, PPARα agonists enhance the curative effects of targeted therapy and radiation therapy. Interestingly, with the emerging role of immunotherapy, attention has been focused on the tumour microenvironment. The dual functions of PPARα agonists in immunotherapy need further research. This review aims to consolidate the operations of PPARα in lipid-related and other ways, as well as discuss the current and potential applications of PPARα agonists in tackling breast cancer.

Fatty Acid Synthase Is the Key Regulator of Fatty Acid Metabolism and Is Related to Immunotherapy in Bladder Cancer

Fatty acid metabolism (FAM) genes are potentially useful for predicting prognosis and immunotherapy response in bladder cancer (BC). To examine this, we constructed a prognostic model and identified key FAM genes in BC. Using transcriptional expression profiles and clinical data of BC patients from public datasets and Changhai (CH) hospital, we built and validated a risk-score model based on 13 prognostic FAM genes. Differential gene expression identified fatty acid synthase (FASN) as central to fatty acid metabolism in BC. FASN was differentially expressed between normal and tumor tissue, and was related to survival. In the CH dataset, FASN independently predicted muscle-invasive BC. FASN differential expression was significantly related to immune-cell infiltration and patients with low FASN expression responded better to immune checkpoint inhibitor (ICI) treatment. SREBF1 was predicted as the most significant transcription factor for FASN. Competing endogenous RNA network analysis suggested that lncRNA AC107027.3 may upregulate FASN by competitively binding miR-27A-3p, thereby regulating the immunotherapy response in BC. Dasatinib and temsirolimus are potential FASN-targeting drugs. Our model efficiently predicted prognosis in BC. FASN is central to fatty acid metabolism, and a potential indicator and regulator of ICI treatment.

Network Pharmacology-Based Strategy to Investigate the Anti-Breast Cancer Mechanisms of Spatholobus suberectus Dunn

Spatholobus suberectus Dunn (SSD) possesses potential antitumor activity; however, the mechanism underlying its anti-proliferative effect on breast cancer is unclear. In this study, we explored potential SSD targets for breast cancer treatment through a network pharmacology approach. First, by integrating multiple databases, a total of 16 potential bioactive compounds and 252 targets were screened. Differentially expressed genes (DEGs) were screened by analyzing breast cancer gene chip data from The Cancer Genome Atlas and Gene Expression Omnibus databases. By overlapping drug targets and DEGs, 33 common targets were found; their functions were further analyzed with Gene Ontology and KEGG analysis. A network of 16 compounds and 33 common targets was constructed, from which 10 hub targets were identified using CytoHubba. Based on the KEGG result and network analysis, the 33 common targets were mainly enriched in the peroxisome proliferator-activated receptor (PPAR) signaling pathway and PPARγ was identified as the potential target of SSD. Moreover, the 10 hub targets were correlated with prognosis and immune infiltration in breast cancer via bioinformatic analysis. Finally, molecular docking and experiments in vitro further verified the targeting ability and anti-breast cancer activity of SSD. SSD is promising in the treatment of breast cancer; PPARγ may be its potential therapeutic target.