Long and short noncoding RNAs in the control of cancer stem cell traits
File(s)
Author(s)
de Giorgio, Alexander James Robert
Type
Thesis
Abstract
Noncoding RNAs (ncRNAs) are now viewed as integral components of gene expression
networks in human cells, including cancerous ones. Investigating the precise roles they
play in varied cellular contexts has become a separate field within cancer research. In
pancreatic adenocarcinoma (PDAC), TGFβ signalling induces EMT and stemness, yet
the involvement of specific ncRNAs remains unknown. We identified two miRNAs,
miR-100 and -125b, to be substantially elevated following TGFβ stimulation, noting that
they derive from the same primary transcript. Modulating levels of miR-100 and -125b
decreases migration and pancsphere formation. Unexpectedly, miR-100 and -125b
appear to use different rules of miRNA-target base pairing, with an enrichment of
non-canonical miR-100 seed matches occurring in the CDS. Clinically, both miR-100
and -125b were elevated in a large PDAC dataset compared to normal tissue, with high
expression associated with lower patient survival.
In stark contrast to the persistently poor prognosis for PDAC patients, breast
cancer survival has improved markedly. Lethal properties of this disease, such as
chemoresistance and metastasis, have been linked to insufficiently characterised
minority breast cancer stem cell (BCSC) populations that may survive available
treatments to regenerate tumours, and can be migratory and invasive. Whether
ncRNAs play prominent roles in BCSC generation and behaviour is also largely
unresolved. Generating mammospheres to enrich for BCSCs, we found several long
noncoding RNAs (lncRNAs) to be differentially expressed compared to adherent cells.
Silencing three of these lncRNAs produced significant impacts on mammsphere
formation efficiency. We focused on Candidate 1, strongly upregulated in
mammospheres, yet unexpectedly increasing mammsphere formation when silenced.
Candidate 1 was chromatin-associated, correlated with chromatin-regulators in TCGA
data, and positively associated with survival. Candidate 1 silencing produced marked
transcriptomic changes when silenced, and bound strongly to the polyfunctional protein
HNRNP L, enabling us to speculate as to its potential mechanism of action.
networks in human cells, including cancerous ones. Investigating the precise roles they
play in varied cellular contexts has become a separate field within cancer research. In
pancreatic adenocarcinoma (PDAC), TGFβ signalling induces EMT and stemness, yet
the involvement of specific ncRNAs remains unknown. We identified two miRNAs,
miR-100 and -125b, to be substantially elevated following TGFβ stimulation, noting that
they derive from the same primary transcript. Modulating levels of miR-100 and -125b
decreases migration and pancsphere formation. Unexpectedly, miR-100 and -125b
appear to use different rules of miRNA-target base pairing, with an enrichment of
non-canonical miR-100 seed matches occurring in the CDS. Clinically, both miR-100
and -125b were elevated in a large PDAC dataset compared to normal tissue, with high
expression associated with lower patient survival.
In stark contrast to the persistently poor prognosis for PDAC patients, breast
cancer survival has improved markedly. Lethal properties of this disease, such as
chemoresistance and metastasis, have been linked to insufficiently characterised
minority breast cancer stem cell (BCSC) populations that may survive available
treatments to regenerate tumours, and can be migratory and invasive. Whether
ncRNAs play prominent roles in BCSC generation and behaviour is also largely
unresolved. Generating mammospheres to enrich for BCSCs, we found several long
noncoding RNAs (lncRNAs) to be differentially expressed compared to adherent cells.
Silencing three of these lncRNAs produced significant impacts on mammsphere
formation efficiency. We focused on Candidate 1, strongly upregulated in
mammospheres, yet unexpectedly increasing mammsphere formation when silenced.
Candidate 1 was chromatin-associated, correlated with chromatin-regulators in TCGA
data, and positively associated with survival. Candidate 1 silencing produced marked
transcriptomic changes when silenced, and bound strongly to the polyfunctional protein
HNRNP L, enabling us to speculate as to its potential mechanism of action.
Version
Open Access
Date Issued
2017-01
Date Awarded
2019-03
Advisor
Stebbing, Justin
Castellano, Leandro
Publisher Department
Surgery & Cancer
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)