Biology subjects

O'Hagan, H. M.

Publications and source records attributed to O'Hagan, H. M..

4 recordsLinked to original sources

bioRxiv2021

Novel epigenetic-metabolic inhibitor combination treatment blocks platinum-induced ovarian cancer stem cell enrichment

High grade serous ovarian cancer (HGSOC) is the most common and aggressive type of ovarian cancer. Platinum resistance is a common occurrence in HGSOC and a main cause of tumor relapse resulting in high patient mortality rates. Recurrent OC is enriched in aldehyde dehydrogenase (ALDH)+ ovarian cancer stem cells (OCSCs), which are resistant to platinum agents. We demonstrated that acute platinum treatment induced a DNA damage-dependent decrease in BRCA1 levels. In a parallel response associated with G2/M arrest, platinum treatment also induced an increase in expression of NAMPT, the rate limiting regulator of NAD+ production from the salvage pathway, and levels of NAD+, the cofactor required for ALDH activity. Concurrent inhibition of DNA methyltransferases (DNMTs) and NAMPT synergistically abrogated the platinum-induced increase in OCSCs. Combining pharmacological inhibitors of DNMT and NAMPT with carboplatin reduced tumorigenesis and OCSC percentage in vivo. We conclude that both epigenetic and metabolic alterations lead to platinum induced OCSC enrichment, providing preclinical evidence that in the neoadjuvant setting, combining DNMT and NAMPT inhibitors with platinum has the potential to reduce OC recurrence and avert the development of platinum resistance.

cancer biology↗

bioRxiv2020

Consensus molecular subtyping of colorectal cancers is influenced by goblet cell content

A critical obstacle in the field of colorectal cancer (CRC) is the establishment of precise tumor subtypes to facilitate the development of targeted therapeutic regimens. While dysregulated mucin production is a histopathological feature of multiple CRC subtypes, it is not clear how well these pathologies are associated with the proportion of goblet cells in the tumor, or whether or not this proportion is variable across all CRC. This study demonstrates that consensus molecular subtype 3 (CMS3) CRC tumors and cell lines are enriched for the expression of goblet cell marker genes. Further, the proportion of goblet cells in the tumor is associated with the probability of CMS3 subtype assignment and these CMS3 subtype tumors are mutually exclusive from mucinous adenocarcinoma pathologies. This study provides proof of principle for the use of machine learning classification systems to subtype tumors based on cellular content, and provides further context regarding the features weighing CMS3 subtype assignment.

systems biology↗

bioRxiv2020

LSD1 promotes secretory cell specification to drive BRAF mutant colorectal cancer

Despite the connection to distinct mucus-containing colorectal cancer (CRC) histological subtypes, the role of secretory cells, including goblet and enteroendocrine (EEC) cells, in CRC progression has been underexplored. Analysis of TCGA and single cell RNA sequencing data demonstrates that multiple secretory progenitor populations are enriched in BRAF-mutant CRC patient tumors and cell lines. Enrichment of EEC progenitors in BRAF-mutant CRC is maintained by DNA methylation and silencing of NEUROD1, a key gene required for differentiation of EECs. Mechanistically, secretory cells and the factors they secrete, such as Trefoil factor 3, are shown to promote colony formation and activation of cell survival pathways in the entire cell population. We further identify LSD1 as a critical regulator of secretory cell specification in vitro and in a colon orthotopic xenograft model, where LSD1 loss reduces tumor growth and metastasis. This work establishes EEC progenitors, in addition to goblet cells, as targetable populations in BRAF-mutant CRC and identifies LSD1 as a therapeutic target in secretory lineage-containing CRC.

cancer biology↗

bioRxiv2020

Platinum-Induced Ubiquitination of Phosphorylated H2AX by RING1A is Mediated by Replication Protein A in Ovarian Cancer

Platinum resistance is a common occurrence in high grade serous ovarian cancer (HGSOC) and a major cause of OC deaths. Platinum agents form DNA crosslinks, which activate nucleotide excision repair (NER), fanconi anemia (FA) and homologous recombination repair (HRR) pathways. Chromatin modifications occur in the vicinity of DNA damage and play an integral role in the DNA damage response (DDR). Chromatin modifiers, including polycomb repressive complex 1 (PRC1) members, and chromatin structure are frequently dysregulated in OC and can potentially contribute to platinum resistance. However, the role of chromatin modifiers in the repair of platinum DNA damage in OC is not well understood. We demonstrate that the PRC1 complex member RING1A mediates monoubiquitination of lysine 119 of phosphorylated H2AX ({gamma}H2AXub1) at sites of platinum DNA damage in OC cells. After platinum treatment, our results reveal that NER and HRR both contribute to RING1A localization and {gamma}H2AX monoubiquitination. Importantly, replication protein A (RPA), involved in both NER and HRR, mediates RING1A localization to sites of damage. Furthermore, RING1A deficiency impaired the activation of the G2/M DNA damage checkpoint and reduced the ability of OC cells to repair platinum DNA damage. Elucidating the role of RING1A in the DDR to platinum agents will allow for the identification of therapeutic targets to improve the response of OC to standard chemotherapy regimens.

cancer biology↗