HAEM5:B lymphoblastic leukaemia/lymphoma with TCF3::PBX1 fusion: Difference between revisions

 

Linda D. Cooley, MD, MBA. Children's Mercy Kansas City, Kansas City, MO

|<span class="blue-text">EXAMPLE:</span> ''ABL1''||<span class="blue-text">EXAMPLE:</span> ''BCR::ABL1''||<span class="blue-text">EXAMPLE:</span> The pathogenic derivative is the der(22) resulting in fusion of 5’ BCR and 3’ABL1.||<span class="blue-text">EXAMPLE:</span> t(9;22)(q34;q11.2)

|<span class="blue-text">EXAMPLE:</span> Common (CML)

|<span class="blue-text">EXAMPLE:</span> D, P, T

|<span class="blue-text">EXAMPLE:</span> Yes (WHO, NCCN)

|<span class="blue-text">EXAMPLE:</span>

The t(9;22) is diagnostic of CML in the appropriate morphology and clinical context (add reference). This fusion is responsive to targeted therapy such as Imatinib (Gleevec) (add reference). BCR::ABL1 is generally favorable in CML (add reference).

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|<span class="blue-text">EXAMPLE:</span> ''CIC''

|<span class="blue-text">EXAMPLE:</span> ''CIC::DUX4''

|<span class="blue-text">EXAMPLE:</span> Typically, the last exon of ''CIC'' is fused to ''DUX4''. The fusion breakpoint in ''CIC'' is usually intra-exonic and removes an inhibitory sequence, upregulating ''PEA3'' genes downstream of ''CIC'' including ''ETV1'', ''ETV4'', and ''ETV5''.

|<span class="blue-text">EXAMPLE:</span> t(4;19)(q25;q13)

|<span class="blue-text">EXAMPLE:</span> Common (CIC-rearranged sarcoma)

|<span class="blue-text">EXAMPLE:</span> D

|

|<span class="blue-text">EXAMPLE:</span>

''DUX4'' has many homologous genes; an alternate translocation in a minority of cases is t(10;19), but this is usually indistinguishable from t(4;19) by short-read sequencing (add references).

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|<span class="blue-text">EXAMPLE:</span> ''ALK''

|<span class="blue-text">EXAMPLE:</span> ''ELM4::ALK''

 

 

|<span class="blue-text">EXAMPLE:</span> Fusions result in constitutive activation of the ''ALK'' tyrosine kinase. The most common ''ALK'' fusion is ''EML4::ALK'', with breakpoints in intron 19 of ''ALK''. At the transcript level, a variable (5’) partner gene is fused to 3’ ''ALK'' at exon 20. Rarely, ''ALK'' fusions contain exon 19 due to breakpoints in intron 18.

|<span class="blue-text">EXAMPLE:</span> N/A

|<span class="blue-text">EXAMPLE:</span> Rare (Lung adenocarcinoma)

|<span class="blue-text">EXAMPLE:</span> T

|

|<span class="blue-text">EXAMPLE:</span>

 

Both balanced and unbalanced forms are observed by FISH (add references).

|-

|<span class="blue-text">EXAMPLE:</span> ''ABL1''

|<span class="blue-text">EXAMPLE:</span> N/A

|<span class="blue-text">EXAMPLE:</span> Intragenic deletion of exons 2–7 in ''EGFR'' removes the ligand-binding domain, resulting in a constitutively active tyrosine kinase with downstream activation of multiple oncogenic pathways.

|<span class="blue-text">EXAMPLE:</span> N/A

|<span class="blue-text">EXAMPLE:</span> Recurrent (IDH-wildtype Glioblastoma)

|<span class="blue-text">EXAMPLE:</span> D, P, T

<center><span style="color:Maroon">'''End of V4 Section'''</span>

 

 

<blockquote class="blockedit">{{Box-round|title=v4:Clinical Significance (Diagnosis, Prognosis and Therapeutic Implications).|Please incorporate this section into the relevant tables found in:

* Gene Mutations (SNV/INDEL)}}</blockquote>

 

The t(1;19) diagnosis was associated with high risk and poor prognosis in earlier studies, however, modern intensive chemotherapy has changed this paradigm. A recent (2021) study showed that patients with ''TCF3-PBX1'' had intermediate rates of 5-year event-free survival (80-88.2%). Despite the favorable prognosis of this subtype of ALL, there is an increased relative risk of central nervous system relapse associated with this translocation.  <ref name=":1">Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J (Eds): WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues (Revised 4th edition). IARC: Lyon 2017</ref><ref name=":0" /><ref>{{Cite journal|last=Jeha|first=Sima|last2=Choi|first2=John|last3=Roberts|first3=Kathryn G.|last4=Pei|first4=Deqing|last5=Coustan-Smith|first5=Elaine|last6=Inaba|first6=Hiroto|last7=Rubnitz|first7=Jeffrey E.|last8=Ribeiro|first8=Raul C.|last9=Gruber|first9=Tanja A.|date=2021-07|title=Clinical significance of novel subtypes of acute lymphoblastic leukemia in the context of minimal residual disease-directed therapy|url=https://pubmed.ncbi.nlm.nih.gov/34250504|journal=Blood Cancer Discovery|volume=2|issue=4|pages=326–337|doi=10.1158/2643-3230.bcd-20-0229|issn=2643-3249|pmc=8265990|pmid=34250504}}</ref>

<center><span style="color:Maroon">'''End of V4 Section'''</span>

 

|<span class="blue-text">EXAMPLE:</span>''EGFR''

|<span class="blue-text">EXAMPLE:</span> Oncogene

|<span class="blue-text">EXAMPLE:</span> Common (lung cancer)

|<span class="blue-text">EXAMPLE:</span> T

|<span class="blue-text">EXAMPLE:</span> Yes (NCCN)

|<span class="blue-text">EXAMPLE:</span> Exons 18, 19, and 21 mutations are targetable for therapy. Exon 20 T790M variants cause resistance to first generation TKI therapy and are targetable by second and third generation TKIs (add references).

|<span class="blue-text">EXAMPLE:</span> ''TP53''; Variable LOF mutations

|<span class="blue-text">EXAMPLE:</span> Tumor Supressor Gene

''TCF3'' gene at 19p13.3 is important during early lymphocyte development, whereas ''PBX1'' at 1q23 is a component of a transcriptional complex that regulates embryogenesis and hematopoiesis. Fusion protein resulting from the TCF3-PBX1 translocation is a transcriptional activator which likely interferes with the normal function of these genes. Expression of this fusion protein is thought to interfere with key regulatory pathways such as WNT and apoptosis/cell cycle control pathways which may drive a leukemic process. The DNA-binding and protein dimerization domains of PBX1 replaces the TCF3 helix-loop-helix DNA-binding motif in ''TCF3-PBX1'' fusion. The remaining transcriptional activating domains of TCF3 leads to constitutive nuclear localization and transformation of PBX1 into an oncogenic transcriptional factor <ref>{{Cite journal|last=Diakos|first=Christofer|last2=Xiao|first2=Yuanyuan|last3=Zheng|first3=Shichun|last4=Kager|first4=Leo|last5=Dworzak|first5=Michael|last6=Wiemels|first6=Joseph L.|date=2014|title=Direct and indirect targets of the E2A-PBX1 leukemia-specific fusion protein|url=https://pubmed.ncbi.nlm.nih.gov/24503810|journal=PloS One|volume=9|issue=2|pages=e87602|doi=10.1371/journal.pone.0087602|issn=1932-6203|pmc=3913655|pmid=24503810}}</ref><ref name=":1" /><ref name=":0" />