TREATMENT OF ACUTE LYMPHOBLASTIC LEUKEMIA USING
GENE THERAPY
BY:
GROUP THREE (3)
Department of Biomedical Sciences
UNIVERSITY OF HEALTH AND ALLIED SCIENCES
OUTLINE
OVERVIEW OF ACUTE LYMPHOBLASTIC LEUKAEMIA
TREATMENT OF ALL USING GENE THERAPY
• MECHANISM OF T CELL ACTIVATION FAILURE
• DEFECTIVE GENES IN ALL
• CAR T CELL PRINCIPLE
• CLONING OF CAR T CELL
• TARGET CELL FOR CAR T CELL GENE THERAPY
• INFUSION OF CAR T CELLS INTO A PATIENT
REFERENCES
2
OVERVIEW OF ACUTE LYMPHOBLASTIC
LEUKAEMIA (1/2)
ALL is a type of cancer of the blood and bone marrow that affects white
blood cells.
It is generally caused by a DNA mutation in the stem cells causing too
many white blood cells to be produced.
The white blood cells are also released from the bone marrow before they
are mature and able to fight infection like fully developed white blood
cells.
It develops in both children and adults, with a peak incidence between 1
year and 4 years.
3
OVERVIEW OF ACUTE LYMPHOBLASTIC
LEUKAEMIA (2/2)
Most ALL arises in healthy individuals, and predisposing factors such as
inherited genetic susceptibility or environmental exposure have been
identified in only a few patients.
It is characterised by chromosomal abnormalities and genetic alterations
involved in the differentiation and proliferation of lymphoid precursor
cells.
4
MECHANISM OF T CELL ACTIVATION FAILURE (1/3)
TCR recognises the presented peptide antigen of tumour cells as the
first signalling along with other co-stimulatory molecule pair bindings,
such as CD28 and B7 as the second signalling.
This double signalling pathway system leads to full activation of T cells
to kill tumour cells.
However, tumour cells also react, such as downregulating the
expression of specific peptide antigens and down-regulating the
expression of MHC and co-stimulatory molecules to inhibit T cell
recognition of Tumour cells to avoid immune attacks.
Therefore, the CD 19 antigenic molecule on the surface of the tumour
cells is downregulated to inhibit TCR recognition. Thus, incapacitating
the TCR.
5
MECHANISM OF T CELL ACTIVATION FAILURE (2/3)
6
DEFECTIVE GENES IN ALL
In children, 11q23-MLL chromosomal rearrangements of the human
MLL gene commonly causes ALL.
The Philadelphia chromosome (Ph) (i.e. t(9;22)(q34;q11)/BCRABL1) is the commonest genetic disorder associated with ALL in
adults.
Some other identified genes include KIT, FLT3, NPM1, CEBPA,
RAS, WTI, BAACL, ERG, MNI, DNMT, TET2, IDH, ASXL1,
PTPN11, and CBL.
7
CAR T CELL PRINCIPLE
The CD-19 specific Chimeric Antigen Receptor (CAR) T cell is the
cloned normal gene against the defective TCR.
It is accomplished by combining an antibody recognition domain with a
TCR signalling motif to form a more robust antigen receptor that has not
just higher tumour recognition ability but the ability to trigger T cell
cytotoxicity effect.
8
CLONING CAR T CELL (1/3)
1. Choose an ideal target tumour antigen for affinity screening to identify
the optimized antibody and obtain the gene sequence of the selected
antibody
2. CAR genes are synthesized and packaged into viral vectors (Lentiviral
vectors). Lentiviral vector is superior to other viral vectors for CAR
construction because (1) they can integrate into non-dividing cells (2)
they are less susceptible to silencing by host restriction factors and (3)
they can deliver relatively larger DNA sequences.
9
CLONING CAR T CELL (2/3)
3. Car genes are delivered into T cells through virus transfection
4. Culture transgenic T cells and select those T c3ells with stable CAR gene
expression
5. Finally, test the quality of these newly created CAR T cells in terms of
the proliferation ability, CAR receptor expression, cytotoxicity, cytokine
release, and anti-tumour functions (both in vitro and in vivo).
10
CLONING OF CAR T CELLS (3/3)
11
TARGET CELL FOR CAR T CELL GENE THERAPY
• The target cells for CAR T cell gene therapy are the lymphoid cells of the bone
marrow.
• During the process, defective lymphocytes are subjected to lymphodepletion either
by chemotherapy or radiation for a variable period before the planned infusion.
12
INFUSION OF CAR T CELLS INTO A PATIENT (1/3)
 Upon infusion into a patient, CAR T cells must traffic to the tumour site,
engage with their cognate antigen, proliferate, avoid inhibitory signals from
the tumour microenvironment, kill target cells, and persist long enough to
ensure that no residual tumour cells arise.
 After intravenous infusion, the CAR T cells circulate, traffic out of the
circulation into the tumour site, and accumulate locally where they
recognize their cognate ligand and are stimulated to proliferate further and
produce their effector functions.
13
INFUSION OF CAR T CELLS INTO A PATIENT (2/3)
 The T cells must avoid inhibitory signals and suppression from the
tumour and the tumour microenvironment and must persist until the
elimination of all malignant cells.
 Those are the components of successful adoptive cellular
immunotherapy. there is no clear dose-response relationship between
the number of CAR T cells infused and the likelihood of response.
14
Infusion of CAR T cells into a patient (3/3)
15
THANK YOU FOR YOUR TIME!!!
16
REFERENCES
Belete, T. M. (2021). The current status of gene therapy for the treatment of cancer.
Biologics: Targets and Therapy, 15, 67–77. https://doi.org/10.2147/BTT.S302095
Gill, S., Maus, M. V., & Porter, D. L. (2016). Chimeric antigen receptor T cell
therapy: 25 years in the making. Blood Reviews, 30(3), 157–167.
https://doi.org/10.1016/j.blre.2015.10.003
Girardi, T., Vicente, C., Cools, J., & De Keersmaecker, K. (2017). The genetics and
molecular
biology
of
T-ALL.
Blood,
129(9),
1113–1123.
https://doi.org/10.1182/blood-2016-10-706465
Society, A. C. (2021). About Acute Lymphocytic Leukemia What Is Acute
Lymphocytic Leukemia. Key Statistics for Acute Lymphocytic Leukemia (ALL), 1–11.
https://www.cancer.org/cancer/acute-lymphocytic-leukemia/about/keystatistics.html#references
17