The Hierarchical Organization of Normal and Malignant Hematopoiesis NORMAL Hematopoie2c Stem Cell (HSC) Leukemia Stem Cells (LSC) MPP MLP CMP Leukemic Progenitors MEP GMP B/NK ETP Leukemic Blasts Erythrocytes Megakaryocytes/ Monocytes Platelets Granulocytes Dendri2c cells NK cells B cells T Cells
Human hematopoie2c stem cells iden2fied on the basis of xenotransplant repopula2on STABLE MULTILINEAGE! HEMATOPOIETIC GRAFT! Human hematopoietic! stem cells! Immune-deficient recipient! 20 yrs of assay op2miza2on - intrafemoral injec2on - T, B, NK, deficiency - macrophage impairment due to Nod allele of SIRP- α - female NSG recipients 10x more sensi2ve Quantitative repopulation assay permits study of human stem cell biology:! self-renewal! differentiation! Proliferation!
Elucida2on of the human hematopoie2c hierarchy at single cell resolu2on From: Doulatov et al Cell Stem Cell 2012
What is Cancer? Cannot differen2ate properly Uncontrolled prolifera2on Cannot die properly.etc Individual cancer cells vary in many cancer hallmarks True, but Hanahan and Weinberg Cell 2011 Is every tumour cell equal and able to maintain long term clonal growth?
Func2onal assay for leukemia- ini2a2ng cells PB or BM from leukemia patient! Immune-deficient recipient! LEUKEMIC GRAFT! Leukemia Initiating Cell (L-IC)! Rare-frequency in AML ~ 1 in 10 6 (varies from patient to patient)! Dormant-able to survive common anti-proliferative chemotherapy!
The Cancer Stem Cell Model apex of neoplastic hierarchy! CSCs possess 2 key stem cell properties:! self-renewal-long term clonal maintenance! ability to differentiate and regenerate tumour heterogeneity! Epigenetic or developmental program in operation! Tumors are caricatures of normal development! NO TUMOR NO TUMOR NO TUMOR NO TUMOR NO TUMOR NO TUMOR
The Hierarchical Organization of Normal and Malignant Hematopoiesis NORMAL Hematopoie2c Stem Cell (HSC) LEUKEMIC MPP MLP Leukemia Stem Cells (LSC) MEP CMP GMP B/NK ETP Hypothesis: If LSC are only cell type capable of sustaining clonal Leukemic Progenitors growth then their properties ultimately govern patient survival Erythrocytes Megakaryocytes/ Monocytes Platelets Granulocytes Dendri2c cells NK cells B cells T Cells Leukemic Blasts
Iden2fica2on of LSC genes Iden2fica2on of LSC specific gene signatures Sort cells HSC Progenitors Mature Patient blood sample (n=84) AML cells (LSC+) no AML cells (LSC-) 160 unique genes differentially expressed Gene expression measurement With Jean Wang and Mark Minden L1 regression analysis on training cohort (n=495) adapted from Eppert et al., Nat Med, 2011 18 gene LSC signature
LSC signature is prognos2c in 4 independent datasets HR = 3.1637, p = 8.24e- 08 median survival: NA (low risk), 223 (high risk) HR = 2.6595, p = 0.00268 median survival: NA (low risk), 301 (high risk) Overall Survival Metzeler primary GSE12417 n=156 HR = 2.6217, p = 1.5e- 07 median survival: 1029 (low risk), 303 (high risk) Metzeler Secondary GSE12417 n=70 HR = 2.0617, p = 0.00636 median survival: 723 (low risk), 314 (high risk) Ley- TCAG Full GSE10358 n=183 Ley- TCAG NK- AML GSE10358 n=83 Survival Time
LSC signature prognos2c across 1000 cancer genomes Low LSC signature High LSC signature Ø Stemness influences pa2ent survival Ø Many gene2c drivers must converge on stemness Ø Determinants of stemness represent a common therapeu2c target
Oien considered as mutually exclusive mechanisms of tumor heterogeneity Gene2c Diversity Epigene2cs and Developmental Pathways- > Hierarchies Tumour Micro- environment Ø Heterogeneity contributes to therapy failure and disease recurrence
Mechanisms of tumor heterogeneity impinge on stemness
Key Ques2ons in the genesis of AML What is the cell of origin: Stem cell or progenitor? What is the First Hit? Why will these cells progress to AML? What is the sequence of subsequent hits? Liran Shlush Sasan Zandi NORMAL HEMATOPOIETIC CELL PRELEUKEMIC CELL LEUKEMIC STEM CELL CSCC Disease Team Genomics Program Tom Hudson, John McPherson LSC Team Jean Wang, Mark Minden Shlush, Zandi et al Nature, 2014
Pre-leukemia: backtracking AML to it s origins Hematopoie2c Stem Cell (HSC) NORMAL Ini2a2ng muta2on Preleukemic Stem Cell (prelsc) ACUTE MYELOID LEUKEMIA Addi2onal muta2ons MPP MLP Clonal expansion Mul2lineage differen2a2on Leukemia Stem Cells (LSC) CMP MEP GMP B/NK ETP Leukemic Progenitors Erythrocytes Megakaryocytes/ Monocytes Platelets Granulocytes Dendri2c cells NK cells B cells T Cells Leukemic Blasts