Spliceosome mutations in myeloid neoplasms

Mario CazzolaDepartment of Hematology Oncology, Fondazione

IRCCS Policlinico San MatteoDepartment of Molecular Medicine, University of Pavia

Pavia, Italy

WHO classification of myeloid neoplasms

• Myeloproliferative neoplasms

• Myelodysplastic syndromes

• Myelodysplastic/myeloproliferative neoplasms

• Acute myeloid leukemia

2008 WHO classification of MDS

Progression to AML (25-30%)

RCUD

RARS

RCMD

RAEB-1

RAEB-2

MDS del(5q)

Ineffective hematopoiesis

Peripheral blood cytopenia Cazzola M. File image 2013

Outcome of MDS according to WHO classification

Cazzola. Haematologica. 2011 Mar;96(3):349-52.

943 MDS pts

Diagnosis of MDS is currently reliant on bone marrow morphology and cytogenetics

• Peripheral cytopenia

• Dysplasia

• Clonal cytogenetic abnormality

Diagnosis of MDS is currently reliant on bone marrow morphology and cytogenetics

• Peripheral cytopenia

• Dysplasia

• Clonal cytogenetic abnormality

• lack of specificity• poor inter-observer reliability

Clinical relevance of the molecular basis of disease

• Philadelphia-negative MPN:- 2005: JAK2 (V617F)- 2008: WHO diagnostic criteria- 2010: safety & efficacy of ruxolitinib in PMF- 2012: FDA & EMA approval of ruxolitinib for

treatment of PMF

Chronic Myeloid Disorders Working Group of the International Cancer Genome Consortium

• Research project on the molecular basis of MDS started in 2010 with whole exome sequencing

RARSRARSCazzola et al. Blood. 2003 Mar 1;101(5):1996-2000 - Pellagatti et al. Blood. 2006 - Della Porta et al.

Leukemia. 2006 Apr;20(4):549-55 - Malcovati et al. J Clin Oncol. 2005 Oct 20;23(30):7594-603

RNA splicing machinery

RNA polymerase II

DNA

Spliceosome

Pre-mRNA

U1U2

Cazzola M. File image 2013

SF3B1 mutations are present in the dominant clone

Papaemmanuil et al. N Engl J Med. 2011 Oct 13;365(15):1384-95

Gene Frequency Gene FrequencySF3B1 ~25% STAG2 3%

TET2 ~20% JAK2 <5%

SRSF2 ~10% MPL <5%

RUNX1 ~10% ATRX <5%

TP53 <10% NPM1 <5%

ASXL1 <10% IDH1- IDH2 <5%

NRAS/KRAS <10% NADPH <5%

EZH2 <10% CEBPA <5%

CBL <10% CKIT <2%

U2AF1 6% CSF1R <2%

ZRSR2 3% PTPN11 <2%

BCOR 3% GNAS <1%

Mutant genes in MDS

Chronic Myeloid Disorders Working Group of the International Cancer Genome Consortium, 2013

Targeted pathways in MDS

Chronic Myeloid Disorders Working Group of the International Cancer Genome Consortium, 2013

Potential outcomes of spliceosome mutations

Normal splicing Exon 1 Exon 2 Exon 3

Decreased (or increased) transcription of normal pre-mRNA (co-transcriptional RNA splicing)

Exon skipping Exon 1 Exon 3

Exon 1 Exon 2 Exon 3IntronIntron retention

Cryptic splice site Exon 1 Exon 3Exon 2 (truncated exon)

Stem cells Hematopoietic precursors

Clinical significance of SF3B1 mutations in MDS

Malcovati et al. Blood. 2011 Dec 8;118(24):6239-46

Clinical significance of SRSF2 mutations in MDS

Thol et al. Blood. 2012 Apr 12;119(15):3578-84

Refractory anemia with ring sideroblasts associated with marked thrombocytosis (RARS-T)

as the paradigmatic example of MDS/MPN

Anemia & thrombocytosis

Ring sideroblasts (myelodysplastic

feature)

Abnormal megakaryocyte proliferation

(myeloproliferative feature)

RARS-T: molecular basis

Normal hematopoietic cell

Ring sideroblasts and ineffective erythropoiesis (myelodysplastic features

of RARS)

Ring sideroblasts and thrombocytosis (myelodysplastic & myeloproliferative features of RARS-T)

Somatic mutation of SF3B1 determining mitochondrial iron overload, ineffective

erythropoiesis and anemia

Somatic mutation of JAK2 or MPL determining gain

of signaling and thrombocytosis

Cazzola et al. Blood. 2013 Jan 10;121(2):260-9

TET2 +/- SRSF2&

ASXL1

Courtesy of R. Solary

International Cancer Genome ConsortiumChronic Myeloid Disorders Working Group

Elli PapaemmanuilPeter CampbellMike Stratton

Luca MalcovatiMatteo Della PortaAnna GallìIlaria AmbaglioCristiana PascuttoMario Cazzola

Eva Hellstrom-Lindberg

David Bowen

Jaqueline BoultwoodJames S WainscoatAndrea Pellagatti

Mike Groves

Anthony Green

Carlo Cambacorti-Passerini

Paresh Vyas

Nick Cross

AGIMM – AIRC-Gruppo Italiano Malattie Mieloproliferative