Helicase-like transcription factor (HLTF)-deleted CDX/TME model of colorectal cancer increased transcription of oxidative phosphorylation genes and diverted glycolysis to boost S-glutathionylation in intravascular metastatic niches [Spatial]
The tumor suppressor, helicase-like transcription factor (HLTF), is expressed in tumor cells but not in the tumor microenvironment (TME) in early stage colorectal cancer (CRC). With disease progression, epigenetic silencing of HLTF in primary CRC tumors coincides with negligible HLTF expression in the TME. Cell line-derived xenograft (CDX) models were developed to test the hypothesis that HLTF-deletion in cancer cells with resultant metabolic reprogramming—a hallmark of metastasis—is a prototypical example of cancer cells modifying their metabolic requirements in response to HLTF-deletion in the TME. The two metabolic pathways that derive energy from glucose—glycolysis and oxidative phosphorylation (OXPHOS)—are variously utilized by cancer cells depending upon the TME. HIF-1a, a master regulator of glycolysis, was eliminated from a role in reprogramming metabolism to satisfy CDX energetic requirements by RNAseq and spatial transcriptomics. Variability in the gut microbiome, with a putative role in altered metabolism, was also eliminated. In contrast, HLTF-deleted cancer cells recovered from DNA damage at a transcriptomic level induction of DNA repair and OXPHOS genes linked to an amoeboid-associated phenotype at the tumor border (confocal microscopy).  HLTF-deleted cancer and endothelial cells of the intravascular niche in the TME share a site-specific protein S-glutathionylation signature (2D DIGE, MALDI-TOF/TOF mass spectrometry) for three glycolytic enzymes (PGK1 Cys379/380, PGAM1 Cys55, ENOA1 Cys119) that diverted glycolysis in support of continued glutathione biosynthesis. The collective absence of HLTF/Hltf from tumor and TME maintained redox homeostasis throughout the CDX and promoted metastasis. Overall design: HLTF-/-CDX tumors (1 per ID Hltf KO mouse x 3 biological replicates) were flash frozen and sent to Genewiz, the next generation sequencing (NGS) division of Azenta Life Sciences (South Plainfield, NJ) RNA-sequencing. Briefly, total RNA was isolated, and evaluated for its integrity and purity with an Agilent Bioanalyzer. RNA was polyA selected prior to library preparation followed by Illumina HiSeq, 2x150 configuration, single index per lane with 350 million raw paired-end (PE) reads per lane, i.e. 40-60 million PE reads per sample (>80% of bases >Q30).