MicroRNA-125b transforms myeloid cell lines by repressing multiple mRNA.
BACKGROUND
We previously described a t(2;11)(p21;q23) chromosomal translocation found in patients with myelodysplasia or acute myeloid leukemia that leads to over-expression of the microRNA miR-125b, and we showed that transplantation of mice with murine stem/progenitor cells overexpressing miR-125b is able to induce leukemia. In this study, we investigated the mechanism of myeloid transformation by miR-125b.


METHODS
To investigate the consequences of miR-125b over-expression on myeloid differentiation, apoptosis and proliferation, we used the NB4 and HL60 human promyelocytic cell lines and the 32Dclone3 murine promyelocytic cell line. To test whether miR-125b is able to transform myeloid cells, we used the non-tumorigenic and interleukin-3-dependent 32Dclone3 cell line over-expressing miR-125b, in xenograft experiments in nude mice and in conditions of interleukin-3 deprivation. To identify new miR-125b targets, we compared, by RNA-sequencing, the transcriptome of cell lines that do or do not over-express miR-125b.


RESULTS
We showed that miR-125b over-expression blocks apoptosis and myeloid differentiation and enhances proliferation in both species. More importantly, we demonstrated that miR-125b is able to transform the 32Dclone3 cell line by conferring growth independence from interleukin-3; xenograft experiments showed that these cells form tumors in nude mice. Using RNA-sequencing and quantitative real-time polymerase chain reaction experiments, we identified multiple miR-125b targets. We demonstrated that ABTB1, an anti-proliferative factor, is a new direct target of miR-125b and we confirmed that CBFB, a transcription factor involved in hematopoiesis, is also targeted by miR-125b. MiR-125b controls apoptosis by down-regulating genes involved in the p53 pathway including BAK1 and TP53INP1.


CONCLUSIONS
This study demonstrates that in a myeloid context, miR-125b is an oncomiR able to transform cell lines. miR-125b blocks myeloid differentiation in part by targeting CBFB, blocks apoptosis through down-regulation of multiple genes involved in the p53 pathway, and confers a proliferative advantage to human and mouse myeloid cell lines in part by targeting ABTB1.
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, Nine Cambridge Center, Cambridge, MA 02142, USA. bousquetmarina@gmail.com
Marina
M
Bousquet
Diu
D
Nguyen
Cynthia
C
Chen
Lauren
L
Shields
Harvey F
HF
Lodish
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D018922:HL-60 Cells; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008819:Mice, Nude; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D009190:Myelodysplastic Syndromes / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D022423:Myeloid Cells / Q000378:metabolism* / Q000473:pathology; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D014411:Neoplastic Stem Cells / Q000378:metabolism* / Q000473:pathology; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism*; D033581:Stem Cell Transplantation; D014183:Transplantation, Heterologous
C531888:MIRN125 microRNA, human; D035683:MicroRNAs; C527468:Mirn125 microRNA, mouse; D009363:Neoplasm Proteins; D012334:RNA, Neoplasm