Branched-chain ketoacids derived from cancer cells modulate macrophage polarization and metabolic reprogramming

Abstract

Macrophages are prominent immune cells in the tumor microenvironment that can be educated into pro-tumoral phenotype by tumor cells to favor tumor growth and metastasis. The mechanisms that mediate a mutualistic relationship between tumor cells and macrophages remain poorly characterized. Here, we have shown in vitro that different human and murine cancer cell lines release branched-chain α-ketoacids (BCKAs) into the extracellular milieu, which influence macrophage polarization in an monocarboxylate transporter 1 (MCT1)-dependent manner. We found that α-ketoisocaproate (KIC) and α-keto-β-methylvalerate (KMV) induced a pro-tumoral macrophage state, whereas α-ketoisovalerate (KIV) exerted a pro-inflammatory effect on macrophages. This process was further investigated by a combined metabolomics/proteomics platform. Uptake of KMV and KIC fueled macrophage tricarboxylic acid (TCA) cycle intermediates and increased polyamine metabolism. Proteomic and pathway analyses revealed that the three BCKAs, especially KMV, exhibited divergent effects on the inflammatory signal pathways, phagocytosis, apoptosis and redox balance. These findings uncover cancer-derived BCKAs as novel determinants for macrophage polarization with potential to be selectively exploited for optimizing antitumor immune responses.

Metabolic Reprogramming of Breast Tumor-Educated Macrophages Revealed by NMR Metabolomics

“…In our study, however, CM from MCF-7 cells, which contained higher BCKA levels than CM from MDA-MB-231 cells, did not enhance VEGF production, suggesting the possible relationship between this pro-tumoral factor and BCKA exposure to be indirect or non-linear. On the other hand, Stage II MCF N/H -TEM decreased the secretion of the inflammatory factor TNF-α, also reported by Cai et al upon incubation with CM from LC cells [58].…”

“…BCKA can be further catabolized through an essentially irreversible reaction catalyzed by branched-chain ketoacid dehydrogenase (BCKDH), ultimately forming acetyl-CoA and succinyl-CoA, which can enter the TCA cycle for energy production [55] and/or lipid synthesis [56], as well as affect epigenetic regulation [52]. On the other hand, incomplete BCKA degradation can lead to their extracellular release, as recently observed for different cancer cell types [57][58][59]. The present study newly shows that MCF-7 cells excrete significantly more BCKA (and HIB, an intermediary in the KIV degradation pathway) than MDA-MB-231 cells.…”

“…It was also shown that BCKA-exposed macrophages possessed decreased phagocytic capacity, potentially contributing to immune suppression in the TME [57]. Very recently, CM from lung cancer (LC) cells (enriched in BCKA), as well as exogenous BCKA, were further reported to influence the polarization of bone marrow-derived macrophages (BMDM) from mice [58]. Among other changes, they increased macrophage production of VEGF, similar to the results we obtained here for MDA N/H -TEM.…”

Coumarin-Based Fluorescent Inhibitors for Photocontrollable Bioactivation

“…We further treated M0-, M1-, or M2-type macrophages with RF-7 and found that CD86 was upregulated in all types of RAW264.7 cells (Figure E and Figure S16). To investigate the global response of M2-TAM repolarization induced by RF-7 , we performed an untargeted MS-based proteomic analysis on M2-type RAW264.7 cells treated with RF-7 . ,− Overall, 6797 protein groups were quantified and 29 differentially expressed proteins were found when comparing RF-7 -treated cells to the untreated M2-type RAW264.7 cells (Figure F). Functional analysis indicated that the most enriched categories of RF-7 upregulated proteins included DNA-templated transcription, regulation of JNK cascade, and stress-activated MAPK cascade (Figure S17).…”

Targeting PHGDH reverses the immunosuppressive phenotype of tumor-associated macrophages through α-ketoglutarate and mTORC1 signaling

“…BMDMs were generated as previously described [ 53 ]. Briefly, bone marrow cells were obtained by flushing the femurs and tibias of wild-type (WT), Phgdh fl/fl or Phgdh fl/fl Cx3cr1 -Cre mice aged 6 to 8 weeks.…”