Gene expression analysis of murine normal mammary gland fibroblasts (mNFs) after perturbing the expression of ASPA (silencing and over-expression)

Metabolic reprogramming is a hallmark of cancer, and the field has predominantly focused on investigating metabolic alterations in tumour cells. However, the relevance, mechanism and consequences of metabolic adaptations in stromal cells remains largely unexplored. Here, we identify Aspartoacylase (ASPA) as a metabolic enzyme consistently repressed in tumour stroma and cancer-associated fibroblasts (CAFs). Loss of ASPA is associated with the accumulation of its substrate, N-acetylaspartate (NAA), and we corroborate the relevance of this metabolite in the control of macrophage polarization. Importantly, we report an unprecedented reciprocal crosstalk of ASPA with TGFβ signalling. TGFβ suppresses ASPA expression, whereas ASPA restrains TGFβ-dependent myofibroblast conversion and the generation of aggressive pro-tumoral responses in fibroblasts. Analyses of human specimens revealed a strong negative prognostic value for ASPA in different tumour types, associated with pro-tumoral macrophages and TGFβ signalling levels. Our findings unveil ASPA expression in fibroblasts as a previously unknown gatekeeper of TGFβ responses and activation in cancer, and shed light into the intratumoral metabolic crosstalk that governs the process of cancer progression.