MAPK pathway-driven metabolic-inflammatory axis in AL amyloidosis Free

Introduction Systemic light chain (AL) amyloidosis is a clonal plasma cell disorder characterized by the deposition of misfolded immunoglobulin light chains in vital organs, often resulting in irreversible organ damage. While plasma cell-directed therapies have improved clinical outcomes, the molecular mechanisms driving disease pathogenesis remain poorly understood. Our previous studies identified overactivation of the PI3K/AKT signaling pathway in AL amyloidosis (Zvida et al., Blood, 2024; Fishov et al., Cancer Med., 2023), a central regulator of cellular and lipid metabolism. Dysregulated lipid metabolism has been implicated in several hematologic malignancies, yet its role in AL amyloidosis remains largely unexplored.

Objectives To characterize the lipidomic landscape in AL amyloidosis compared to multiple myeloma (MM) and healthy controls (HC) in the context of inflammatory signaling. The ultimate goal of this work is to uncover novel metabolic-immunologic targets for therapeutic intervention.

Methods Lipidomic profiling was performed by liquid chromatography-mass spectrometry (LC-MS) on plasma samples from AL patients (n=30), MM (n=30), and HCs (n=15). Fatty acid synthase (FASN) expression was validated by qRT-PCR in CD138+ bone marrow (BM) samples. A lipogenesis index was calculated using the ratio of palmitoleic acid to linoleic acid as a surrogate marker of FASN activity. Additionally, RNA-seq was conducted on CD138⁺ BM cells from AL and HC samples (n=8). Cytokine profiling was performed on serum from AL, MM, and HC subjects (n=10 each). Functional assays and lipidomic analysis were conducted in ALMC1 cells using the FASN inhibitor TVB-2640 and the MEK inhibitor cobimetinib.

Results Lipidomic analysis of pre-treatment plasma samples revealed a significant increase in the lipogenesis index in AL patients, indicating elevated FASN activity. This was consistent with increased FASN mRNA expression in bone marrow CD138⁺ cells, suggesting both transcriptional upregulation and enzymatic activation. In ALMC1 cells, dose- and time-dependent FASN inhibition with TVB-2640 (0-2 μM, 24-72h) significantly reduced cell viability (IC50=1.3 μM), suggesting that FASN activity supports AL plasma cell survival. In addition, AL patients demonstrated a significant decrease in polyunsaturated fatty acids (PUFAs) levels, including docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and linoleic acid (LA), compared to MM and HC. As PUFAs are known suppressors of FASN expression and activity, their depletion may contribute to sustained FASN upregulation and a metabolic shift toward de novo lipogenesis. Pathway enrichment analysis of patient lipidomic data revealed significant enrichment of omega-3/6 fatty acid metabolism, ATP generation, and inflammation-related pathways. Notably, imbalances in omega-3 and omega-6 fatty acids ratio have been associated with heightened inflammatory responses. In parallel, RNA-seq analysis identified several upregulated pathways in AL amyloidosis patients compared to controls, including immune regulation, MAPK signaling, mitochondrial dysfunction, oxidative phosphorylation, and IL-13 signaling. Both IL-13 and MAPK are known to transcriptionally induce FASN and regulate immune responses, providing a possible mechanistic link between inflammation and lipid remodeling. Cytokine profiling revealed elevated levels of IL-1β, IL-13, IL-8, IFN-γ, MIP-1α (CCL3), G-CSF, MCP-1 (CCL2), and IP-10 (CXCL10) in AL serum samples, consistent with a systemic inflammatory phenotype. Pharmacologic inhibition of MAPK signaling (by cobimetinib) in ALMC1 cells led to restoration of PUFA levels and a concurrent reduction in cytokine secretion, suggesting that MAPK activity sustains both the inflammatory and lipogenic phenotype in AL.

ConclusionsOur findings identify metabolic-inflammatory axis in AL amyloidosis, in which IL-13 and MAPK signaling may promote fatty acid reprogramming through FASN activation and PUFA suppression. This axis sustains a pro-inflammatory environment that may contribute to disease pathogenesis. Thus, FASN and MAPK may represent promising metabolic-immunologic targets for therapeutic intervention in AL amyloidosis.