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Cancer Drug Resist 2018;1:266-302 I http://dx.doi.org/10.20517/cdr.2018.18 Page 285

lation status. Here we have investigated the hypothesis that, depending on the phosphorylation state, PEA-
15 can enhance cisplatin sensitivity in ovarian cancer cells. Two mutated versions of PEA-15 mimicking
the two phosphorylation statuses of the protein were overexpressed in SKOV-3 human ovarian carcinoma
cells by Lipofectamine-mediated transfection. PEA-15AA is a mutated non-phosphorylatable form of PEA-
15 capable of ERK1/2 binding in the cytoplasm, whereas PEA-15DD is a phosphomimetic variant stimulat-
ing ERK1/2 nuclear translocation. PEA-15AA overexpression resulted in a significant increase (P < 0.0001)
in cisplatin sensitivity (EC = 10.0 µmol/L) compared to the mock-transfected cells (EC = 14.9 µmol/L) as
50
50
determined by an MTT-assay. In PEA-15DD-transfected cells, cisplatin cytotoxicity (EC = 14.3 µmol/L)
50
was similar to that of the mock-transfected controls. The whole-transcriptome expression profiling with a
Clariom S microarray revealed the Nrf2/ARE signaling pathway as central to the PEA-15AA positive ef-
TM
fect on the sensitivity of SKOV-3 cells to cisplatin. The relevance of this pathway was successfully validated
using retinoic acid, which is a potent inhibitor of Nrf2/ARE. Co-treatment with 20 µmol/L retinoic acid
significantly (P < 0.0001) sensitized SKOV-3 cells to cisplatin as EC was reduced from 32.6 µmol/L for the
50
platinum complex alone to 14.0 µmol/L in the combination. Our results show that non-phosphorylatable
PEA-15 increases cisplatin sensitivity in SKOV-3 human ovarian carcinoma cells through interference with
the Nrf2/ARE signaling.

36. Identifying a potential role for TauT in conferring resistance to standard treatment in glio
blastoma

1
1
1
2
1
Nora Rippaus , Julie Higgins , Rhiannon Barrow , Alexander Bruns , Aruna Chakrabarty ,
4
Azzam Ismail , Jacquelyn Bond , Katherine Ashton , Khaja Syed , Michael Jenkinson , Andrew
3
1
4,5
2
1
Brodbelt , Susan Short , Lucy F. Stead 1
4
1 Faculty of Medicine and Health, St James’s University Hospital, University of Leeds, Leeds LS9 7TF, UK
2 Leeds Teaching Hospitals NHS Trust, St James’s University Hospital, Leeds LS9 7TF, UK
3 Lancashire Teaching Hospitals NHS Trust, Royal Preston Hospital, Preston PR2 9HT, UK
4 Walton Centre NHS Trust, Liverpool L9 7LJ, UK
5 Institute of Translational Medicine, University of Liverpool, Liverpool L9 7LJ, UK
Glioblastoma (GBM) is an incurable and fatal brain cancer; almost half of patients die within a year of di-
agnosis despite a standard, aggressive treatment regimen of surgery, radiotherapy and chemotherapy with
Temozolomide. All drugs designed to target molecular features of primary GBM tumours have failed to
prolong survival. This is likely because of inherently treatment-resistant cells within primary tumours that
evade current therapies, continuing to proliferate to form a recurrent tumour. We have sequenced RNA
from paired pre- and post-treatment GBM patient tumours to identify genes that are differentially ex-
pressed between primary and recurrent GBMs and investigate whether treatment resistance is driven at the
transcriptional rather than genomic level, as suggested from recent published work. In parallel, we isolated
cancer cells from a newly resected primary GBM and cultured them as polyclonal spheroids in stem-cell
permissive conditions. Half of these spheroids received the non-surgical components of standard treat-
ment and seven days later we sequenced RNA from single cells from both treated and untreated spheroids.
SLC6A6 was the most significantly upregulated gene in recurrent vs. matched primary patient tumours
and the only gene that was also significantly upregulated in treated vs. untreated single cells. One inter-
pretation of these data is that GBM cells expressing SLC6A6 are more resistant to standard treatment. This
is supported by: (1) the fact that patients with primary GBM tumours with low SLC6A6 expression have
significantly better prognosis; (2) work showing that SLC6A6 expression promotes multidrug resistance
in colorectal cancer; (3) preliminary data from functional screens that we have performed on established
GBM cell lines. SLC6A6 encodes a taurine transporter, TauT, with an important role in brain development