Functional characterisation of driver events in ovarian clear cell carcinoma
View / Open Files
Authors
Gounaris, Ioannis
Advisors
Brenton, James
Date
2014-11-11Awarding Institution
University of Cambridge
Author Affiliation
Cancer Research UK Cambridge Institute
Qualification
PhD
Language
English
Type
Thesis
Metadata
Show full item recordCitation
Gounaris, I. (2014). Functional characterisation of driver events in ovarian clear cell carcinoma (doctoral thesis). https://doi.org/10.17863/CAM.15891
Abstract
Ovarian clear cell carcinoma (OCCC) is a distinct subtype of epithelial ovarian cancer (EOC)
characterised by glycogen accumulation. Frequently arising within endometriotic cysts, it can
be conceived as an ectopic endometrial cancer. Putative driver genomic events include
HNF1B overexpression and inactivating ARID1A mutations. Importantly, these can also be
found in a significant proportion of adjacent non-malignant endometriotic lesions and,
therefore, are likely early events in OCCC pathogenesis. I hypothesised that the study of the
functional consequences of these driver genomic events and metabolic perturbations would
provide insights into potential therapeutic targets in this difficult to treat cancer.
Gene expression arrays in normal mouse uterus, embryonic fibroblasts and human
immortalised ovarian surface epithelium cells revealed that a core ARID1A-driven
transcriptional programme, conserved across normal tissues and species, centred on
regulation of mitosis and cell cycle progression-related genes, and involving potentially
targetable kinases, exists. Despite this, the effect of ARID1A knockdown on proliferation in
human cell lines and mouse cells and tissues was found to be context and tissue specific.
Interestingly, in vivo knockout in the uterine epithelium of Arid1afl/fl mice was accompanied by
a dramatic increase in proliferation, in support of its suggested driver-event role in uterinederived
cancers.
HNF1B overexpression has been previously reported to affect proliferation and metabolism in
a variety of cell lines but studies in well characterised OCCC cells are lacking. Here, HNF1B
was found to consistently drive proliferation in a panel of bona fide OCCC cell lines. Pathway
analysis of HNF1B-regulated genes suggested that HNF1B is involved in interactions with the
tumour microenvironment. Indeed, I observed that HNF1B negatively regulates migration and
invasion. Additionally, I found that HNF1B overexpression drives glycogen accumulation and
that its knockdown reverses the Warburg effect. These results point at trade-offs among
proliferation, metabolism and metastatic capability and suggest that HNF1B overexpression
may be one of the reasons that, in marked contrast to high-grade serous EOC, OCCC
frequently presents as early stage disease.
Little is known about the functional consequences of glycogen accumulation in OCCC. I report
that OCCC cell lines display increased expression of glycogen metabolism enzymes and that
inhibiting the rate limiting phosphorylase (PYGL) and synthase enzymes markedly decreased
proliferation, even in the presence of plentiful extracellular glucose. This observation suggests
a role for glycogen beyond that of a glucose store. Assays performed to elucidate how PYGL
knockdown affects proliferation suggest that this may be through G2/M phase arrest, possibly
caused by inhibition of lipid breakdown or altered PKA signalling. Furthermore, preliminary
evidence suggests that the effects of PYGL knockdown on proliferation are limited to
malignant cells only.
x
In conclusion, this project studied the functional consequences of three driver events in OCCC:
ARID1A mutations, HNF1B overexpression and glycogen accumulation. Targeting ARID1Aregulated
kinases and glycogen metabolism and perturbing HNF1B function require further
investigation as potential therapeutic strategies in OCCC.
Sponsorship
MRC
Identifiers
This record's DOI: https://doi.org/10.17863/CAM.15891
Rights
Attribution-NonCommercial-NoDerivs 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by-nc-nd/2.0/uk/
Recommended or similar items
The following licence files are associated with this item: