The Tumor Microbiome Reacts to Hypoxia and Can Influence Response to Radiation Treatment in Colorectal Cancer.

Tumor hypoxia has been shown to predict poor patient outcomes in several cancer types, partially because it reduces radiation's ability to kill cells. We hypothesized that some of the clinical effects of hypoxia could also be due to its impact on the tumor microbiome. Therefore, we examined the RNA sequencing data from the Oncology Research Information Exchange Network database of patients with colorectal cancer treated with radiotherapy. We identified microbial RNAs for each tumor and related them to the hypoxic gene expression scores calculated from host mRNA. Our analysis showed that the hypoxia expression score predicted poor patient outcomes and identified tumors enriched with certain microbes such as Fusobacterium nucleatum. The presence of other microbes, such as Fusobacterium canifelinum, predicted poor patient outcomes, suggesting a potential interaction between hypoxia, the microbiome, and radiation response. To experimentally investigate this concept, we implanted CT26 colorectal cancer cells into immune-competent BALB/c and immune-deficient athymic nude mice. After growth, in which tumors passively acquired microbes from the gastrointestinal tract, we harvested tumors, extracted nucleic acids, and sequenced host and microbial RNAs. We stratified tumors based on their hypoxia score and performed a metatranscriptomic analysis of microbial gene expression. In addition to hypoxia-tropic and -phobic microbial populations, analysis of microbial gene expression at the strain level showed expression differences based on the hypoxia score. Thus, hypoxia gene expression scores seem to associate with different microbial populations and elicit an adaptive transcriptional response in intratumoral microbes, potentially influencing clinical outcomes. SIGNIFICANCE: Tumor hypoxia reduces radiotherapy efficacy. In this study, we explored whether some of the clinical effects of hypoxia could be due to interaction with the tumor microbiome. Hypoxic gene expression scores associated with certain microbes and elicited an adaptive transcriptional response in others that could contribute to poor clinical outcomes.

Redefining the PTEN promoter: identification of novel upstream transcription start regions.

Germline mutation of PTEN is causally observed in Cowden syndrome (CS) and is one of the most common, penetrant risk genes for autism spectrum disorder (ASD). However, the majority of individuals who present with CS-like clinical features are PTEN-mutation negative. Reassessment of PTEN promoter regulation may help explain abnormal PTEN dosage, as only the minimal promoter and coding regions are currently included in diagnostic PTEN mutation analysis. Therefore, we reanalyzed the architecture of the PTEN promoter using next-generation sequencing datasets. Specifically, run-on sequencing assays identified two additional transcription start regions (TSRs) at -2053 and -1906 basepairs from the canonical start of PTEN, thus extending the PTEN 5'UTR and redefining the PTEN promoter. We show that these novel upstream TSRs are active in cancer cell lines, human cancer and normal tissue. Furthermore, these TSRs can produce novel PTEN transcripts due to the introduction of new splice donors at -2041, -1826 and -1355, which may allow for splicing out of the PTEN 5'UTR or the first and second exon in upstream-initiated transcripts. Combining ENCODE ChIP-seq and pertinent literature, we also compile and analyze all transcription factors (TFs) binding at the redefined PTEN locus. Enrichment analyses suggest that TFs bind specifically to the upstream TSRs may be implicated in inflammatory processes. Altogether, these data redefine the architecture of the PTEN promoter, an important step toward a comprehensive model of PTEN transcription regulation, a basis for future investigations into the new promoters' role in disease pathogenesis.