Aldehyde Dehydrogenase, more than a marker for cancer stem cells

• Aldehyde dehydrogenases (ALDH) are enzymes that catalyse the oxidation of aldehydes to their
consequent acids by a NAD(P)+-dependent irreversible reaction
• This enzyme oxidises and detoxifies aldehydes that can be harmful to the organism
• ALDH is considered a marker for CSCs, identifiable by the Aldefluor assay
CANCER STEM CELLS (CSCs)...
• Are a small tumour cell subpopulation that can initiate and drive tumourigenic growth
• Carry out an asymmetric division: they are able to renew themselves and they can also differentiate
• Can arise from mutations in normal stem cells, progenitor or mature differentiated cells
• Are responsible for therapy failure, recurrence and metastasis
• Give another perspective in the treatment against cancer  Aldehyde dehydrogenase as a candidate target
Aldehyde Dehydrogenase,
more than a marker for cancer stem cells
Marta Ferrer Fernández – Biochemistry Degree – Bahelors Thesis – June 2016
INTRODUCTION
Existence of
CSCs
Tumour
initiation and
growth
Conventional
therapies
failure
Tumour
recurrence Metastasis
Need for
targeted
therapies
against CSCs
1. CANCER STEM CELLS AND THEIR ORIGIN 2. ALDEHYDE DEHYDROGENASE
Acknowledgements | I would like to thank my supervisor, Jaume Farrés; Carlota Colomer for the interview; R. Weinberg, D. Pattabiraman and I. Skvortsova for answering my emails and being so helpful.
1. CSCs open new frontiers in the treatment against cancer
2. ALDH is a good marker for CSCs because its identification and isolation is easier thanks to the Aldefluor Assay
3. Resistance to conventional therapies and metastasis can be explained by CSCs, where ALDH plays a valuable
role on this matter
4. ATRA could be a novel cancer therapy by producing retinoic acid and causing differentiation, although non-
CSCs also have to be eliminated to eradicate all the bulk of the tumour by conventional therapies
5. CONCLUSIONS
Therapy
failure
(resistance)
•Chemotherapy
•Cooperation between
ALDH and multi-drug
resistance mechanism
•Oxidation and
inactivation of
chemotherapeutic agents
(cyclophosphamide)
•Radiotherapy
Metastasis
•ALDH+ cells have
demonstrated metastasic
potential
•This role may be due to the
ALDH1A3 isoform
ALDH is a CSC
marker
correlated with
3. RETINOIC ACID SIGNALLING PATHWAY 4. THERAPIES THAT TARGET CSCs
The interest of finding a CSC
target is focused on the retinoic
acid signalling pathway, in which
ALDH plays an essential role.
1. Allahverdiyev, A., Bagirova, M. & Oztel, O. in Dehydrogenases 3–28 (Intech, 2012).
2. Croker, A. K. The Role of ALDHhiCD44+ Cells in Breast Cancer Metastasis and Therapy Resistance.
Doctoral Thesis, The University of Western Ontario, Canada, 2012.
3. Dr. Robert Weinberg - "Cancer Stem Cells: A New Target in the Fight Against Cancer". [Online].
Whitehead Pulse, 14/11/2011. Available in: https://www.youtube.com/watch?v=Nou8VWpWba4
4. Januchowski, R., Wojtowicz, K. & Zabel, M. The role of aldehyde dehydrogenase (ALDH) in cancer drug
resistance. Biomed. Pharmacother. 67, 669–680 (2013).
5. Pattabiraman, D. R. & Weinberg, R. A. Tackling the cancer stem cells - what challenges do they pose?
Nat. Rev. Drug Discov. 13, 497–512 (2014).
RELEVANT REFERENCES
Targeting CSC-
dependent of
signalling pathways
Some specific
signalling pathways
(TGF-β, Wnt, Notch
and Hedgehog) are
involved in the
maintenance of the
cancer stem cell
state
PRI-724 is an
inhibitor of Wnt
signalling that
lokades the β-
catenin-CREB
binding protein
interaction
 proliferation
Targeting the tumour
microenvironment
Affecting the
microenvironment
of the tumour, the
maintenance of the
stem cell state is lost
and the EMT
programme is
altered
Elimination of
signals that permit
the stemness:
inhibition of
cytokines (such as
IL-6) and growth
factors
Immunotherapy
Activation of
immune response
against specific
antigens in CSCs
Cytotoxic T
lymphocytes,
natural killers and
antibodies
Differentiation
therapy
This therapy induces
the exit from the
CSC state into a
more differentiated
state
All-trans retinoic
acid (ATRA)
treatment inhibits
proliferation and
invasion by
activating retinoic
acid pathway
Retinol (vitamin A) Retinaldehyde Retinoic acid
(RA)
Figure was produced using Servier Medical Art (www.servier.com)
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Figure 2 | Aldefluor Assay. BODIPY-
aminoacetaldehyde can diffuse into the
cell to be converted to a negatively-
charged fluorescent product named
BODIPY-aminoacetate.
Figure 3 | Synthesis, degradation and mode of
action of retinoic acid. Retinol is oxidised to
retinaldehyde by a reversible reaction given by
alcohol dehydrogenase (ADH). Then, retinaldehyde
is oxidised to RA by ALDH in the cytosol, and free
RA goes into the nucleus attached to a chaperone
protein(CRABP2 or FABP5) in order to bind to RAR
or RXR. When RA binds to the heterodimer, histone
acetylation and activation of transcription is given.
This signalling pathway is stopped when the
degradation of RA is given by CYP26 enzymes.
Figure 1 | Origin of cancer stem cells. CSCs can renew themselves to preserve the stem cell population and they can also
differentiate to form various specialised cells in an asymmetric division. In fact, they can arise from mutations in normal
stem cells, progenitor cells or differentiated cells, and they are responsible for tumour formation and growth. For this
reason, CSC directed therapies would lead to tumour regression, whereas conventional therapies cause tumour relapse.
Cellular retinoic acid binding protein 2 (CRABP2); fatty acid binding protein
5 (FABP5); peroxisome proliferator-activated receptor (PPAR); response
element (RE); retinoic acid receptor (RAR); retinoid X receptor (RXR)
Molecules in Figure 2 are from: Stem Cell Technologies. Technical Bulletin - Identification of viable stem and
progenitor cells with Aldefluor [Online]. France; 2009. [Consultation 7/4/2016]. Available in:
https://www.stemcell.com/~/media/Technical%20Resources/0/0/28728_aldefluor_July%202009.pdf?la=en
ADH ALDH
RA
v
v
CRABP2
RA RA FABP5
CYP26
Oxidized
products
Nucleus
RAR PPAR
RARE PPRE
Co-activator
complex
RAR RXR
Differentiation Proliferation
Normal stem cell
Cancer stem cell
Normal progenitor cell
Mutated progenitor cell
Normal differentiated cell
Mutated differentiated cell
Mutation
ASYMMETRIC DIVISION
ASYMMETRIC DIVISION
HETEROGENOUS TUMOUR
FORMATION
De-differentiation
Conventional therapies CSC directed therapies
TUMOUR
RELAPSE
TUMOUR
REGRESSION
ALDH is not only a marker for cancer stem cells, and further studies are needed
to resolve more questions about cancer