Knockdown of HSPA9 induces TP53-dependent apoptosis in human hematopoietic progenitor cells.
Myelodysplastic syndromes (MDS) are the most common adult myeloid blood cancers in the US. Patients have increased apoptosis in their bone marrow cells leading to low peripheral blood counts. The full complement of gene mutations that contribute to increased apoptosis in MDS remains unknown. Up to 25% of MDS patients harbor and acquired interstitial deletion on the long arm of chromosome 5 [del(5q)], creating haploinsufficiency for a large set of genes including HSPA9. Knockdown of HSPA9 in primary human CD34+ hematopoietic progenitor cells significantly inhibits growth and increases apoptosis. We show here that HSPA9 knockdown is associated with increased TP53 expression and activity, resulting in increased expression of target genes BAX and p21. HSPA9 protein interacts with TP53 in CD34+ cells and knockdown of HSPA9 increases nuclear TP53 levels, providing a possible mechanism for regulation of TP53 by HSPA9 haploinsufficiency in hematopoietic cells. Concurrent knockdown of TP53 and HSPA9 rescued the increased apoptosis observed in CD34+ cells following knockdown of HSPA9. Reduction of HSPA9 below 50% results in severe inhibition of cell growth, suggesting that del(5q) cells may be preferentially sensitive to further reductions of HSPA9 below 50%, thus providing a genetic vulnerability to del(5q) cells. Treatment of bone marrow cells with MKT-077, an HSPA9 inhibitor, induced apoptosis in a higher percentage of cells from MDS patients with del(5q) compared to non-del(5q) MDS patients and normal donor cells. Collectively, these findings indicate that reduced levels of HSPA9 may contribute to TP53 activation and increased apoptosis observed in del(5q)-associated MDS.
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Tuoen
T
Liu
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Kilannin
K
Krysiak
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Cara Lunn
CL
Shirai
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Sanghyun
S
Kim
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Jin
J
Shao
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Matthew
M
Ndonwi
Department of Medicine, Division of Oncology, Washington University School of Medicine, St. Louis, Missouri, United States of America.|Siteman Cancer Center, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Matthew J
MJ
Walter
D017209:Apoptosis / Q000187:drug effects / Q000235:genetics*; D015415:Biomarkers; D004351:Drug Resistance / Q000235:genetics; D015870:Gene Expression; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D018840:HSP70 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D024101:Mitochondrial Proteins / Q000037:antagonists & inhibitors / Q000172:deficiency* / Q000235:genetics*; D009190:Myelodysplastic Syndromes / Q000235:genetics; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics* / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000235:genetics / Q000378:metabolism
D015415:Biomarkers; D018840:HSP70 Heat-Shock Proteins; C492001:HSPA9 protein, human; D024101:Mitochondrial Proteins; D011725:Pyridines; D012333:RNA, Messenger; D013844:Thiazoles; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; C097880:MKT 077