TGF β1‐induced leucine limitation uncovered by differential ribosome codon reading

Abstract

Cancer cells modulate their metabolic networks to support cell proliferation and a higher demand of building blocks. These changes may restrict the availability of certain amino acids for protein synthesis, which can be utilized for cancer therapy. However, little is known about the amino acid demand changes occurring during aggressive and invasive stages of cancer. Recently, we developed diricore, an approach based on ribosome profiling that can uncover amino acid limitations. Here, we applied diricore to a cellular model in which epithelial breast cells respond rapidly to TGF β1, a cytokine essential for cancer progression and metastasis, and uncovered shortage of leucine. Further analyses indicated that TGF β1 treatment of human breast epithelial cells reduces the expression of SLC 3A2, a subunit of the leucine transporter, which diminishes leucine uptake and inhibits cell proliferation. Thus, we identified a specific amino acid limitation associated with the TGF β1 response, a vulnerability that might be associated with aggressiveness in cancer. image TGF β1 treatment of human breast epithelial cells reduces the expression of SLC 3A2, a subunit of the leucine transporter, which diminishes leucine uptake and inhibits cell proliferation. TGFβ1 induces pausing of ribosomes at leucine codons in MCF10A cells. MCF10A cells downregulate the leucine transporter SLC3A2 and reduce leucine uptake in response to TGFβ1. Exogenous leucine releases the codon‐specific stalling induced by TGFβ1. Reconstitution of the SLC3A2 transporter rescues the stalling of ribosomes at leucine codons as well as TGFβ1‐induced proliferation inhibition.