Genetic Manipulation of FBP1 Expression in Breast Cancer Cells Reveals the Potential of FBP1 to Disrupt The Warburg Effect, and Nutrient Mediated Adaptive Post-Translational Regulation of FBP1 Protein Levels.

The key gluconeogenic enzyme Fructose 1,6 bisphosphatase has emerged as a potential metabolic tumour suppressor in recent years. Ablation of FBP1 expression in various tumours fosters metabolic rewiring towards an increased reliance on aerobic glycolysis. While FBP1 is completely repressed in many cancers, breast tumours display distinct FBP1 expression based on their subtype, hence making breast cancer a suitable model for discerning the effects of FBP1 in contexts of cancer initiation and progression. We used ectopic over-expression and CRISPR-Cas9 disruption to establish cell lineages with stable alterations in their FBP1 levels. Complete knock-outs of FBP1 on gene level confirm the major impact of FBP1 on cancer cell metabolism and proliferation. Moreover, our results reveal cancer subtype-specific peculiarities in response to ectopic FBP1 expression including a clear demonstration of an adaptive proteasomal degradation of FBP1 in breast cancer cells, which is regulated by glucose and nutrient availability. In addition to validating the suggested tumour suppressor role of FBP1, our findings demonstrate an efficient adaptive complex regulation of FBP1 expression and its impact on the adaptation of cancer cells to nutrient conditions. Our results highlight the importance of FBP1 ablation on the protein level and its potential relevance to cancer and beyond.