Biology subjects

Loo, P. V.

Publications and source records attributed to Loo, P. V..

3 recordsLinked to original sources

bioRxiv2024

Pan-cancer subclonal mutation analysis of 7,827 tumors predicts clinical outcome

Intra-tumor heterogeneity is characterized by a diverse population of tumor clones and subclones which are important drivers of tumor evolution and therapeutic response. However, accurate subclonal reconstruction at scale remains challenging. We developed a machine learning tool, CliPP, and surveyed 9,972 tumors from 32 cancer types. We found that high subclonal mutation load (sML), the fraction of subclonal single nucleotide variants (SNVs) to all SNVs in the coding region, was prognostic of survival (progression free survival or overall survival) in 18 cancer types. In 14 cancers with low to moderate tumor mutation burden (TMB), high sML was associated with better prognosis. In immunotherapy trials for 42 metastatic prostate cancer (mCRPC), high sML was predictive of favorable response to ipilimumab and associated with increased CD8+ T-cell infiltration and decreased macrophage population. A validation using 613 whole-genomes of esophageal adenocarcinoma confirms the favorable effect of high sML and the observed tumor-associated macrophage. Our study identifies sML as a key feature of cancer, suggesting a biphasic relationship between evolutionary dynamics and differential immune environments. Finally, sML may serve as an orthogonal approach to identify likely responders of immune checkpoint blockade in low to moderate TMB tumors.

genomics↗

bioRxiv2024

Focal Deletions of a Promoter Tether Activate the IRX3 Oncogene in T Cell Acute Lymphoblastic Leukemia

Oncogenes can be activated in cis through multiple mechanisms including enhancer hijacking events and noncoding mutations that create enhancers or promoters de novo. These paradigms have helped parse somatic variation of noncoding cancer genomes, thereby providing a rationale to identify noncanonical mechanisms of gene activation. Here we describe a novel mechanism of oncogene activation whereby focal copy number loss of an intronic element within the FTO gene leads to aberrant expression of IRX3, an oncogene in T cell acute lymphoblastic leukemia (T-ALL). Loss of this CTCF bound element downstream to IRX3 (+224 kb) leads to enhancer hijack of an upstream developmentally active super-enhancer of the CRNDE long noncoding RNA (-644 kb). Unexpectedly, the CRNDE super-enhancer interacts with the IRX3 promoter with no transcriptional output until it is untethered from the FTO intronic site. We propose that promoter tethering of oncogenes to inert regions of the genome is a previously unappreciated biological mechanism preventing tumorigenesis.

cancer biology↗

bioRxiv2023

Pan-cancer evolution signatures link clonal expansion to dynamic changes in the tumour immune microenvironment

Cancer is an evolutionary process characterised by profound intra-tumour heterogeneity. Intra-tumour heterogeneity can be quantified using in silico estimates of cancer cell fractions of tumour-specific somatic mutations. Here we demonstrate a data-driven approach that uses cancer cell fraction distributions to identify 4 robust pan-cancer evolutionary signatures from an analysis of 4,146 individual tumour samples (TCGA) representing 17 distinct cancer types. Evolutionary signatures defined a continuum of cancer cell fractions representing neutral evolution, clonal expansion and fixation. Correlation of evolutionary signatures with programs representing distinct mutational and biological processes demonstrated that individual tumours enriched for clonal expansions and fixations were associated with immune evasion and distinct changes in the tumour immune microenvironment. We observed a dynamic switch between adaptive and innate immune processes as tumours undergo clonal fixation and escape immune surveillance. We also identify mutational processes underpinning different modes of tumour evolution and demonstrate that switching between adaptive and innate immune cell populations is accompanied by the clonal expansion of driver genes that modulate tumour-stroma interactions1.

bioinformatics↗