Knockdown of NIR Suppresses Breast Cancer Cell Proliferation via Promoting FOXO3

Abstract

Background: Novel inhibitor of histone acetyltransferase repressor (NIR), a corepressor with a novel inhibitor of histone acetyltransferase (INHAT) activity, has been reported to be a negative modulator of p53 and a regulator of the cell cycle in cancer cells. However, the role of NIR in the progression of breast cancer remains elusive. Materials and Methods: Oncomine database was used to analyze the mRNA levels and prognosis value of NIR in breast cancer. We performed loss-of-function and gain-of-function studies using lentivirus expressing shRNA targeting NIR, enhancer of zeste homolog 2 (EZH2) and forkhead box O3 (FOXO3) or lentivirus expressing NIR or FOXO3, respectively. Cell proliferation and colony formation assays were performed. Coimmunoprecipitation (Co-IP) and immunoprecipitation (IP) were performed to identify the interaction between NIR and polycomb repressive complex 2 (PRC2) subunits. ChIP assay was used to identify the enrichment of NIR, EZH2, H3K27ac and H3K27me3 at the FOXO3 promoter region and the regulation of H3K27 modification at the FOXO3 promoter by NIR. Results: High levels of NIR expression were correlated with poor prognosis in breast cancer patients. Knockdown of NIR suppressed the proliferation of breast cancer cells. Mechanically, NIR was recruited by EZH2 to the promoter vicinity of FOXO3 via direct protein-protein interaction. Silencing NIR increased H3K27ac and decreased H3K27me3 levels at the FOXO3 promoter, resulting in enhancing FOXO3 expression. In accordance with this, growth inhibition of breast cancer cells caused by silencing of NIR could be reversed by FOXO3 knockdown. Conclusion: NIR knockdown inhibited proliferation by switching the H3K27me3 and H3K27ac marks at the FOXO3 promoter to promote FOXO3 transcription, and this effect depends on the physical interaction between NIR and PRC2 in breast cancer cells. Our results suggest that NIR might be a potential target for breast cancer treatment.

Unmasking the biological function and regulatory mechanism of NOC2L: a novel inhibitor of histone acetyltransferase

“…Based on the knowledge of the biological properties and function of NOC2L, further investigation was conducted to examine how NOC2L affects biological events. It has been proposed that NOC2L can participate in some key biological events, including the rRNA biogenesis [ 48 ], embryonic development [ 49 , 50 ], and cancer progression [ 9 , 51 ]. All these biological events affected by NOC2L can be contributed to its characteristic and function mentioned previously in this review.…”

“…As a negative regulator of tumor suppressor P53 [ 7 ], NOC2L may promote tumorigenesis by counteracting the tumor suppression function of P53 [ 7 ]. In addition to P53-dependent pro-cancer effect of NOC2L [ 9 , 51 ], other P53-independent mechanisms of NOC2L-mediated tumorigenesis remain to be further addressed. As we all know, uncontrolled proliferation is a typical characteristic of malignant tumor [ 64 ].…”

“…NOC2L was demonstrated to be upregulated in breast cancer patients [ 51 ]. Moreover, the high expression level of NOC2L was correlated with the poor outcome of breast cancer patients [ 51 ].…”

“…NOC2L was demonstrated to be upregulated in breast cancer patients [ 51 ]. Moreover, the high expression level of NOC2L was correlated with the poor outcome of breast cancer patients [ 51 ]. In breast cancer cells, cell proliferation and colony formation was suppressed upon NOC2L knockdown, indicating an important role of NOC2L in breast cancer progression [ 51 ].…”

“…NOC2L was found to be recruited by Enhancer of zeste homolog 2 (EZH2) and cooperate with EZH2 through physical interaction to promote the methylation of H3K27 in the vicinity of forkhead box O3 ( FOXO3 ) promoter region [ 51 ], leading to the downregulation of tumor suppressor FOXO3 in breast cancer cells [ 51 ]. As a consequence of FOXO3 downregulation, tumor progression was promoted [ 51 ]. Similar to the situation of CRC [ 9 ], NOC2L may also be a potential marker and target for breast cancer prediction and treatment [ 51 ].…”