INK4 locus is located on human chromosome 9p21 region and encodes three tumor suppressor genes, p15, p16 and ARF. So far, we revealed that a long non-coding RNA (lncRNA), ANRIL, transcribed from INK4 locus represses the transcription of p15 and p16 genes. ANRIL associates with polycomb protein complexes and recruits them on INK4 locus, leading to the transcriptional repression. The depletion of ANRIL inhibits the proliferation of cancer cells such as non-small cell lung cancer and colorectal cancer, indicating that ANRIL functions to promote cancer cells proliferation. Recently, we found a novel lncRNA induced by oncogenic Ras signal (named LION: lncRNA induced by oncogenic Ras signal). In this study, we showed that LION is involved in the transcriptional regulation of INK4 locus and cell proliferation.
Human non-small cell lung cancer cell H1299 and colorectal cancer cell HCT116 were transfected with siRNA oligonucleotides against LION. The expression analysis of INK4 locus genes was performed by quantitative reverse transcription-polymerase chain reaction (Q-RT-PCR). Cell cycle analysis was performed by using Muse cell analyzer.
RT-PCR analysis showed that LION is highly expressed in several cancer cells such as non-small cell lung cancer, cervical cancer and colorectal cancer compared with normal lung fibroblasts. Silencing LION by siRNA oligonucleotides inhibits the proliferation of H1299, HCT116 and HeLa cells. Q-RT-PCR analysis showed that silencing LION increases the p15 and p16 mRNA, suggesting that LION is involved in the transcriptional repression of INK4 locus. Cell cycle analysis showed that silencing LION causes G2/M phase arrest in cell cycle, suggesting that LION functions to promote G2/M transition.
LION is involved in the promotion of cancer cells proliferation such as H1299 and HCT116 cells via regulating p15, p16 and other genes related to G2/M phase control.
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All authors have declared no conflicts of interest.