Molecular Pathogenesis of Diffuse Large B Cell Lymphoma
Marco Ciró, PhD
European Institute of Oncology, Milan
marco.ciro@ieo.eu
Diffuse Large B Cell Lymphoma is a disease of mature B cell
Lymphoma is the most common blood cancer.
Cancerous lymphocytes can travel to many parts of the body, including the lymph
nodes, spleen, bone marrow, blood or other organs, and can accumulate to form
tumors.
The two main forms of lymphoma are Hodgkin lymphoma (HL) and non-Hodgkin
lymphoma (NHL).
NHL is the most common
Two types of lymphocytes can develop into lymphomas: B-cells and T-cell
85% of NHLs are B cell NHL
Diffuse Large B Cell Lypmhoma (DLBCL) is the most COMMON and AGGRESSIVE
40% of B-NHL, mostly de novo
50% median survival at 5 years
B cells are precursors of the immunoglobulin-producing cells (plasma cells) and
of the immunological memory cells (memory B cells)
Blood smear
Il tessuto principale in cui le cellule
B si sviluppano e’ il midollo osseo
(organo linfoide primario)
Cellule B mature migrano negli
organi linfoidi secondari
Linfonodi, milza, tessuto linfoidi
intestinali.
Se attivate, B cell mature si
trasformano in plasma cellule o
cellule B della memoria
B cell DNA rearrangement
VDJ recombnation
Somatic Hyper Mutation
Class Switch recombination
risultato
Ab Primary sequence
High Affinity Ab
Different isotype classes
chi
Cellule B immature
Cellule B mature
Cellule B mature
dove
Midollo osseo
Organi linfoidi secondari
Organi linfoidi secondari
B cells are precursors of the immunoglobulin-producing cells (plasma cells) and
of the immunological memory cells (memory B cells)
HOW
-Proliferation and selection of high affinity B cells
-high affinity antibodies
via SHM = Somatic Hyper Mutation
-different isotype classes
via CSR = Class Switch Recombination
WHERE:
Germinal Center in secondary lymphoid
organs
constant DNA DAMAGE is the cause of SHM and CSR
The enzyme AID (Activation Induced cytdine Deaminase) is the source of DNA
damage
AID deaminates C to U in single-stranded (= transcribed) DNA
AID is expressed in activated B cells
Consequences:
DNA mutations
Double Strand Breaks
SHM: variability in Antibody variable regions
CSR: Antibody of different isotypes
lymph node
hematoxylin
Cellular composition of Germinal Center
blue=T cell
red=dendritic cells
Green=proliferation
Immunofluorescence
After encountering an Antigen, B cells are stimulated to both proliferate and mutate their DNA
A place of sustained cell proliferation and abundant DNA damage
BCL6 is the master regulator of Germinal Center B cell program
BCL6 master regulator of Germinal Center B cell program
BCL6 is a transcriptional repressor essential for GC:
Prevent differentiation of B cell - promote DNA remodelling
BCL6 in the germinal center
Dysregulation of BCL6 render BCL6 oncogenic DLBCL
A place of sustained cell proliferation and abundant DNA damage
Diffuse Large B-cell Lymphoma (DLBCL)
•Most common and aggressive subtype of B-NHL
in the adult (~40% of all diagnoses)
•Poor response to therapy; ~30% of patients not
cured by currently available therapeutic strategies
•Marked heterogeneity in morphologic, molecular,
and clinical features
•Phenotypic subgroups recognized by gene
expression profile studies
Gene expression profiling can classify DLBCL into at least two
distinct subtypes
GC B cell-like (GCB)-DLBCL exhibits a transcriptional
profile that resembles that of GC B cells:
-elevated expression of BCL6
-the presence of hypermutated immunoglobulin genes.
Activated B cell-like (ABC)-DLBCL shows several features
of activated B cells entering plasmablastic differentiation
-downregulate the GC-specific program
-upregulate genes required for plasma cell
differentiation.
Alizadeh A et al, Nature 2000; Staudt LM, N Engl J Med 2003
Gene expression profiling can classify DLBCL into at least two
distinct subtypes
Standard therapy is R-CHOP:
Rituximab (antiCD20) + combined chemotherapy
Alizadeh A et al, Nature 2000; Staudt LM, N Engl J Med 2003
DLBCL is a clinical challenge
The identification of genetic alterations that contribute to the malignant
transformation of a B cell into a DLBCL is helping to better understand the
biology of this disease and new emerging therapies.
cellular programs that had not been previously appreciated
new potential targets for improved diagnosis and therapy.
Experimental Strategy
~100 DLBCL primary biopsies
Copy Number Analysis
Whole Exome Sequencing
Bioinformatics analysis
Candidate gene resequencing
Functional
Readouts
Gene Expression
Profiling
IHC analysis
DLBCL is a clinical challenge
The identification of new genetic alterations in molecular
subtypes of DLBCL uncovered
New relevant cellular programs
new potential targets for improved diagnosis and therapy.
0
MLL2
CREBBP
TP53
MYOM2
MLL3
TNFAIP3
PIM1
CD36
B2M
CD79B
PRDM1
CARD11
BCL2
ITPKB
MEF2B
P2RY8
MYD88
ANKLE2
KDM2B
HNF1B
CD58
MYC
EZH2
ADAMTSL3
AKAP8
C12orf35
CCND3
DCHS1
DUSP27
MAGEC3
TLL2
TMEM30A
EP300
FBXO11
DPYD
DSC3
KLF2
MED12L
MTMR8
PMS1
TSC22D1
OFD1
TBL1XR1
TRAF3
BCL2L10
BRSK1
CAMTA1
CYTSB
DUSP9
FBXO31
GRB2
HMGB1
MYO1G
PPP2R5A
RASGEF1A
RGAG1
SERPINA1
SMARCA1
ZNF521
ZWILCH
NOTCH1
% of mutated cases
Recurrently mutated genes in DLBCL
35
30
25
20
15
10
5
Pasqualucci et al., Nature Genetics 2011
Recurrently mutated genes in DLBCL
35
25
20
15
10
MYD88
CARD11
0
CD79B
5
TNFAIP3
% of mutated cases
30
Constitutive activation of NF-kB pathway in ABC-DLBCL
Queste mutazioni si trovano soprattutto in ABC DLBCL
B cell singalling pathways
ABC DLBCL specific therapy
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