1. Case 274 T lymphoblastic leukemia with t(5;14)(q35;q32) and lineage switch to acute myeloid leukemia
Rebecca L. King,
Gerald Wertheim, Michele E. Paessler
The Children’s Hospital of Philadelphia
Perelman School of Medicine at the University of Pennsylvania
Philadelphia, PA

2. Clinical History
13 year old boy
300
214
4.2
82% Blasts

3. Bone Marrow : April 2009

4. Flow Cytometry: April 2009 CD7+/CD4+ CD5+/CD2- CD14-/CD33- cCD3+/TdT+
MPO-

5. 46,XY,t(5;14)(q35;q32),del(9)(p21.3),del(13)(q14.11q21.1)[7].
ish t(5;14)(IGH+;IGH-), del(9)(p16-)
/46,idem,del(7)(p1?3p?21)[6].
/45,idem,dic(7;8)(p1?3;p11.2),del(10)(q22)[6].
ish dic(7;8)(7ptel-,7cen+,D7S486+,8cen+,MYC+)
del(9)(p21)

6. Diagnosis
T lymphoblastic leukemia
t(5;14)(q35;q32)
Del 9p

7. Clinical History 9.1 5.9 43 15% blasts
Day 30 of DI: Blasts seen on peripheral smear.
9.1
15% blasts
5.9 43

8. Bone Marrow: 6 months after Dx
MPO

9. Flow Cytometry: October 2009
CD14-/CD33+
CD15+
cCD3/TdT-
MPO+

10. April
2009
October
2009
MPO
MPO
CD3
CD3

11. Therapy-related AML or Lineage switch from T-ALL to AML
Diagnosis?
Therapy-related AML or Lineage switch from T-ALL to AML

12. 1. Cryptic t(5;14) detected by FISH with IGH probe
2. Del 9p
der(15)t(11;15)
del(7p)
der(4)
del(9)(p21)
67,XY,+Y,der(4)del(4)(q13.1)inv dup(4)(p12pter),del(7)(p11.2p14.1),+8,-9,del(9)(p21.3),-10,-11,-14,-15,der(15) t(11;15)(q13.1;q26),+19,+22[9].ish der(15)t(11;15)(MLL+,PML+)
nuc ish 11q23(MLLx3)[89/100] nuc ish 15q22(PMLx2),17q21.1(RARAx3)[94/100] nuc ish 9p21(p16x1),9cen(CEP9x2)[90/100]

13. FISH: TLX3-BCL11b t(5;14)(q35;q32) present in 84% of nuclei
Image courtesy of Rhett Ketterling, MD

14. Final Diagnosis
T lymphoblastic leukemia with t(5;14)(q35;q32) and lineage switch to acute myeloid leukemia.

15. TLX3-BCL11b t(5;14)(q35;q32) 25% of pediatric T-ALL 5-10% adult T-ALL
Single reported case of myeloid leukemia
Overexpression of the orphan homeobox (HOX) proteins TLX1
and TLX3 represents the most frequent oncogenic event due to
chromosomal translocation in human T-ALL
HOX proteins in general, and TLX in particular, exert a repressive
activity on transcriptional events during embryonic development
As mentioned, an alternative and non-mutually-
exclusive candidate for mediation of the maturation arrest
might be BCL11b, recently reported to be a direct target downregulated
by TLX1 (De Keersmaecker et al., 2010). Loss of
BCL11b, a transcriptional repressor required for T lymphoid
specification, leads, however, to a much earlier DN1/2 block
(Ikawa et al., 2010; Li et al., 2000, 2004).
knockdown of
TLX1/TLX3 led to apoptosis, concomitant TCRa transcription
and rearrangement, cell-maturation, and sTCRab+ expression
prospective studies.
Taken together, our results demonstrate that the maturation
block observed in TLX+ T-ALLs is in large part due to ETS1-mediated
TLX recruitment to the Ea core, leading to repression of Ea
and blocked Va-Ja rearrangement. Failure to express a TCRa
gene arrests development of ab-committed thymocytes around
b-selection, when a variety of cell-proliferation signals are likely
to be maintained, hence contributing to oncogenesis. This
blockage can be overcome by TLX1/3 abrogation or by downstream
TCRab expression within an appropriate cellular context.
These observations have fundamental consequences both for
targeted therapy in TLX+ T-ALLs and for the role of aberrant
TCR expression in T lymphoid oncogene

16. Coincidence or biological relationship?
Overexpression of the orphan homeobox (HOX) proteins TLX1
and TLX3 represents the most frequent oncogenic event due to
chromosomal translocation in human T-ALL
HOX proteins in general, and TLX in particular, exert a repressive
activity on transcriptional events during embryonic development
As mentioned, an alternative and non-mutually-
exclusive candidate for mediation of the maturation arrest
might be BCL11b, recently reported to be a direct target downregulated
by TLX1 (De Keersmaecker et al., 2010). Loss of
BCL11b, a transcriptional repressor required for T lymphoid
specification, leads, however, to a much earlier DN1/2 block
(Ikawa et al., 2010; Li et al., 2000, 2004).
knockdown of
TLX1/TLX3 led to apoptosis, concomitant TCRa transcription
and rearrangement, cell-maturation, and sTCRab+ expression
prospective studies.
Taken together, our results demonstrate that the maturation
block observed in TLX+ T-ALLs is in large part due to ETS1-mediated
TLX recruitment to the Ea core, leading to repression of Ea
and blocked Va-Ja rearrangement. Failure to express a TCRa
gene arrests development of ab-committed thymocytes around
b-selection, when a variety of cell-proliferation signals are likely
to be maintained, hence contributing to oncogenesis. This
blockage can be overcome by TLX1/3 abrogation or by downstream
TCRab expression within an appropriate cellular context.
These observations have fundamental consequences both for
targeted therapy in TLX+ T-ALLs and for the role of aberrant
TCR expression in T lymphoid oncogene

17. TLX3 Homeobox protein related to TLX1
Repressive activity on transcription during embryonic development
Dadi et al. Cancer Cell, 2012.
TLX1 and TLX3 suppress TCRα rearrangement via ETS1 accounting for the block in T-cell maturation seen in these T-ALLs.
Knockdown of TLX1/3 leads to apoptosis, TCRα rearrangement and cell maturation
Overexpression of the orphan homeobox (HOX) proteins TLX1
and TLX3 represents the most frequent oncogenic event due to
chromosomal translocation in human T-ALL
HOX proteins in general, and TLX in particular, exert a repressive
activity on transcriptional events during embryonic development
As mentioned, an alternative and non-mutually-
exclusive candidate for mediation of the maturation arrest
might be BCL11b, recently reported to be a direct target downregulated
by TLX1 (De Keersmaecker et al., 2010). Loss of
BCL11b, a transcriptional repressor required for T lymphoid
specification, leads, however, to a much earlier DN1/2 block
(Ikawa et al., 2010; Li et al., 2000, 2004).
knockdown of
TLX1/TLX3 led to apoptosis, concomitant TCRa transcription
and rearrangement, cell-maturation, and sTCRab+ expression
prospective studies.
Taken together, our results demonstrate that the maturation
block observed in TLX+ T-ALLs is in large part due to ETS1-mediated
TLX recruitment to the Ea core, leading to repression of Ea
and blocked Va-Ja rearrangement. Failure to express a TCRa
gene arrests development of ab-committed thymocytes around
b-selection, when a variety of cell-proliferation signals are likely
to be maintained, hence contributing to oncogenesis. This
blockage can be overcome by TLX1/3 abrogation or by downstream
TCRab expression within an appropriate cellular context.
These observations have fundamental consequences both for
targeted therapy in TLX+ T-ALLs and for the role of aberrant
TCR expression in T lymphoid oncogene

18. BCL11b Ikawa et al. Science, 2010. T cell Su et al. Blood, 2006.
Significance of this gene thought to lie in downstream T-cell-specific cis-activating elements juxtaposed to TLX3 (leads to TLX3 upregulation)
Ikawa et al. Science, 2010.
BCL11b is a key checkpoint protein in T-cell development
T/NK/
Myeloid
T cell
Multipotent
HSC
T/B/
NK/
Eryth/Meg
B-cell
BCL11b
BCL11b is a critical gene in T cell development. Studies identified T cell specific cis activating elements downstream of BCL11b that are juxtaposed to the TLX3 locus as a result of the translocation.
However, an intriguing finding about BCL11b was described in this 2010 study from Japan. IN this study they identified BCL11b as the critical protein at this checkpoint in T cell development in mice. It is likely that this is environmentally mediated, as decreased IL7 concentrations lead to upregulation of BCL11b which leads to downregulation of myeloid antigens. In addition, they describe the appearance of self renewing T cell progenitors in BCL11b-/- thymocytes in vitro suggests a mechanism for loss of function mutations as well as disruption of this gene to lead to leukemogenesis. In addition, it potentially provides a quite nice explanation for the interesting phenotype switch seen in this case.

19. Therapeutic Implications
Mixed lineage acute leukemias are difficult to treat and have poor overall survival
Aim therapy at myeloid or T component?
Potential for targeted therapy aimed at suppressing TLX3 to overcome the differentiation “block”
TLX3 is a good target bc it’s not expressed in most adult tissues.

20. Patient Follow-Up Switched from T-ALL to AML therapy
Did not achieve second remission
Died 2 months following AML diagnosis

21. Acknowledgements CHOP Gerald Wertheim Michele Paessler Jackie Biegel
Penn
Dale Frank
Mayo Clinic
Rhett Ketterling