Mass spectrometry imaging identifies metabolic patterns associated with malignant potential in pheochromocytoma and paraganglioma

Objective: Within the past decade, important genetic drivers of pheochrom ocytoma and paraganglioma (PPGLs) development have been identified. The pathophysiological mechanism that translates these alterations into functional autonomy and potentially malignant behavior has not been elucidated in detail. Here we used MALDI-mass spectrometry imaging (MALDI-MSI) of formalin-fixed paraffin-embedded tissue specimens to comprehensively characterize the metabolic profiles of PPGLs. Design and methods: MALDI-MSI was conducted in 344 PPGLs and results correlated wit h genetic and phenotypic information. We experimentally silenced genetic drivers by siRN A in PC12 cells to confirm their metabolic impact in vitro. Results: Tissue abundance of kynurenine pathway metabolites such as xan thurenic acid was significantly lower (P = 2.35E-09) in the pseudohypoxia pathway cluster 1 compared to PPGLs of the kinase-driven PPGLs cluster 2. Lower abundance of xanthurenic acid was associated with shorter metas tasis-free survival (log-rank tests P = 7.96E-06) and identified as a risk factor for metastasis independent of the ge netic status (hazard ratio, 32.6, P = 0.002). Knockdown of Sdhb and Vhl in an in vitro model demonstrated that inositol metabolism and sialic acids w ere similarly modulated as in tumors of the respective cluster. Conclusions: The present study has identified distinct tissue metabolomic pr ofiles of PPGLs in relation to tumor genotypes. In addition, we revealed significantly altered metabo lites in the kynurenine pathway in metastatic PPGLs, which can aid in the prediction of its malignant potential. How ever, further validation studies will be required to confirm our findings.