Long noncoding RNA, CCDC26, controls myeloid leukemia cell growth through regulation of KIT expression.
BACKGROUND
Accumulating evidence suggests that some long noncoding RNAs (lncRNAs) are involved in certain diseases, such as cancer. The lncRNA, CCDC26, is related to childhood acute myeloid leukemia (AML) because its copy number is altered in AML patients.


RESULTS
We found that CCDC26 transcripts were abundant in the nuclear fraction of K562 human myeloid leukemia cells. To examine the function of CCDC26, gene knockdown (KD) was performed using short hairpin RNAs (shRNAs), and four KD clones, in which CCDC26 expression was suppressed to 1% of its normal level, were isolated. This down-regulation included suppression of CCDC26 intron-containing transcripts (the CCDC26 precursor mRNA), indicating that transcriptional gene suppression (TGS), not post-transcriptional suppression, was occurring. The shRNA targeting one of the two CCDC26 splice variants also suppressed the other splice variant, which is further evidence for TGS. Growth rates of KD clones were reduced compared with non-KD control cells in media containing normal or high serum concentrations. In contrast, enhanced growth rates in media containing much lower serum concentrations and increased survival periods after serum withdrawal were observed for KD clones. DNA microarray and quantitative polymerase chain reaction screening for differentially expressed genes between KD clones and non-KD control cells revealed significant up-regulation of the tyrosine kinase receptor, KIT, hyperactive mutations of which are often found in AML. Treatment of KD clones with ISCK03, a KIT-specific inhibitor, eliminated the increased survival of KD clones in the absence of serum.


CONCLUSIONS
We suggest that CCDC26 controls growth of myeloid leukemia cells through regulation of KIT expression. A KIT inhibitor might be an effective treatment against the forms of AML in which CCDC26 is altered.
Domain of Life Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashihiroshima, Hiroshima, 739-8521, Japan. thirano@hiroshima-u.ac.jp.
Tetsuo
T
Hirano
Domain of Life Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashihiroshima, Hiroshima, 739-8521, Japan. m142847@hiroshima-u.ac.jp.
Ryoko
R
Yoshikawa
Department of Hematology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan. hharada@juntendo.ac.jp.
Hironori
H
Harada
Department of Hematology, Juntendo University School of Medicine, 2-1-1 Hongo, Bunkyo-ku, Tokyo, 113-8421, Japan. ykharada@juntendo.ac.jp.
Yuka
Y
Harada
Domain of Life Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashihiroshima, Hiroshima, 739-8521, Japan. aishida@hiroshima-u.ac.jp.
Atsuhiko
A
Ishida
Domain of Life Sciences, Graduate School of Integrated Arts and Sciences, Hiroshima University, 1-7-1 Kagamiyama, Higashihiroshima, Hiroshima, 739-8521, Japan. takey@hiroshima-u.ac.jp.
Takeshi
T
Yamazaki
D001483:Base Sequence; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002999:Clone Cells; D016895:Culture Media, Serum-Free; D020869:Gene Expression Profiling; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D020868:Gene Silencing / Q000187:drug effects; D056426:Genetic Loci; D005822:Genetic Vectors / Q000378:metabolism; D018922:HL-60 Cells; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D020014:K562 Cells; D015470:Leukemia, Myeloid, Acute / Q000235:genetics* / Q000473:pathology*; D008969:Molecular Sequence Data; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019009:Proto-Oncogene Proteins c-kit / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D062085:RNA, Long Noncoding / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D044967:Serum; D013449:Sulfonamides / Q000494:pharmacology
C528178:4-t-butylphenyl-N-(4-imidazol-1-ylphenyl)sulfonamide; D016895:Culture Media, Serum-Free; D007093:Imidazoles; D047428:Protein Kinase Inhibitors; D062085:RNA, Long Noncoding; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013449:Sulfonamides; D019009:Proto-Oncogene Proteins c-kit