TFE3-SLC36A1 axis promotes resistance to glucose starvation in kidney cancer cells [ChIP-Seq]
"Starving cancer to death" is pursued for cancer therapy. An intriguing regime is to inhibit glucose transporter GLUT1 in cancer cells. But past attempts are challenged by that cancer cells can somehow tolerate starvation. In addition, during cancer progression, cancer cells may suffer from insufficient nutrient supply, for example due to insufficient angiogenesis. So uncovering mechanism of starvation resistance shall not only shed insight into cancer progression but also benefit cancer therapy. TFE3 is known as a transcription factor capable of activating autophagic genes. Physiological TFE3 activity is regulated by phosphorylation-triggered translocation, which is sensitive to nutrient status. We recently reported TFE3 constitutively localizes to cell nucleus in kidney cancer, promoting cell proliferation even under replete condition. But whether and how TFE3 affects kidney cancer cell sensitivity to starvation is unclear. In this study, we find TFE3 promotes kidney cancer cell resistance to glucose starvation. We show starvation triggers TFE3 protein stabilization through increasing its O-GlcNAcylation. Furthermore, through unbiased functional genomic study, we identify genes sensitive to TFE3 protein level, including SLC36A1, a lysosomal amino acid transporter. We find SLC36A1 is overexpressed in kidney cancer, promotes mTOR activity and kidney cancer cell proliferation. Importantly, SLC36A1 level is directly upregulated by TFE3 upon starvation, which enhances cellular resistance to starvation. Suppressing TFE3 or SLC36A1 significantly increased cellular sensitivity to GLUT1 inhibitor in kidney cancers. Collectively, we uncover a TFE3-SLC36A1 axis that responds to starvation and enhances starvation tolerance in kidney cancer. Overall design: To examine the effect on transcriptome by TFE3, we performed ChIP-Seq and RNA-Seq to identify TFE3 directly-regulated genes. For ChIP-Seq, we stably expressed HA-TFE3 in Caki-1 kidney cancer cells. HA antibody was used for Chromatin IP. ChIP DNA was analyzed with Next generation sequencing. For RNA-Seq, Caki-1 cells were transduced with lentiviruses expressing TFE3-shRNA or control sequences. Total RNA was extracted for RNA-Seq.