No abstract

Long-term exposure to benzene or its metabolite, hydroquinone (HQ), can causally contribute to acute myeloid leukemia (AML). Long noncoding RNAs (LncRNAs) are essential epigenetic regulators with critical roles in tumor initiation and malignant progression; however, the mechanism by which aberrantly expressed LINC00173 regulates the pathogenesis of AML is not fully understood. Here, we found that the expression of LINC00173 decreased while the expression of DNMT1 increased, and the methylation of LINC00173 promoter was negatively correlated with LINC00173 expression in GEPIA, CCLE databases, benzene-exposed workers, B-cell non-Hodgkin's lymphoma (B-NHL), K562, U937 or HQ induced malignantly transformed TK6 (HQ-MT cells). Furthermore, in 5-AzaC (DNA methyltransferase inhibitor) or TSA (histone deacetylation inhibitor) treated HQ-MT cells, the expression of LINC00173 was restored by reduced DNA promoter methylation levels. HQ-MT cells with DNMT1 knockout by CRISPR/Cas9 restored the expression of LINC00173 and inhibited the DNA methylation of its promoter as well as enrichment of DNMT1 to promoter. Overexpression of LINC00173 inhibited the expression of DNMT1, cell proliferation, tumor growth, enhanced chemosensitivity to cisplatin and apoptosis in HQ-MT cells. LINC00173 interacts with DNMT1 to regulate the methylation of LINC00173 promoter. Overall, this study provides evidence that interaction between DNMT1 and LINC00173 regulates the expression of LINC00173 by regulating its promoter methylation level, thus regulating the function of HQ-MT cells in vitro and in vivo, providing a new therapeutic target for benzene induced tumor.

No abstract

Hydroquinone (HQ) is one of the major metabolites of benzene and can cause abnormal gene expression. It is a known carcinogen that alters cell cycle disruption and cell proliferation. However, its chemical mechanism remain a mystery. Circular RNAs (cir-cRNAs) are a subtype of noncoding RNAs (ncRNAs) that play a variety of roles in biological processes. Hsa_circ_001944 expression was upregulated in 30 leukemia patients and HQ-induced malignant transformed TK6 cells. Hsa_circ_001944 silencing inhibited the growth of HQ-TK6 cells and halted the cell cycle. The silencing of hsa_circ_0001944 led to increased cell accumulation in G1 versus S phase, increased apoptosis in the sh1944 versus the shNC group, and increased levels of DNA damage (γ-H2AX), leading to cell cycle arrest. In summary, inhibition of hsa_circ_001944 restricted cell growth by inhibiting cell cycle arrest and induced growth of HQ-TK6 cells by modulating PARP1 expression. Hsa_circ_0001944 targeted HuR, which is a kind of RNA-binding protein, to control PARP1 expression via RNAinter, RBPmap, and RBPdb. Fluorescence in situ hybridization combined with immunofluorescent labeling and western blotting experiments showed that hsa_circ_001944 was able to dissociate HuR and PARP1 binding in HQ-TK6 cells, control PARP1 production, and ultimately alter the PARP1/H-Ras pathway.

Hydroquinone (HQ), one of the most significant metabolic activation products of benzene in an organism, can cause hematological toxicity, such as acute myeloid leukemia. It is a clear carcinogen that can cause changes in the disorder of cell cycle and cell growth. However, its molecular mechanisms remain unclear. E4 transcription factor 1 (E4F1), an important transcription factor, participating in the regulation of cell cycle may be related to the occurrence of tumor. Here, we examined the HQ‐induced malignant transformed TK6 cells (TK6‐HT) to illustrate the role of E4F1 in carcinogenesis. The present study showed that both the expressions of E4F1 messenger RNA and protein increased obviously in TK6‐HT, preliminarily indicating that E4F1 is associated with HQ‐induced carcinogenesis. To further explore the role of E4F1, we established E4F1 silencing TK6‐HT (pLVX‐shE4F1) and its control cells (pLVX‐shNC) using lentiviral short hairpin RNA (shRNA) interference expression plasmid vector pLVX‐shRNA. Flow cytometry and cell counting kit‐8 assay were used to determine the effects of E4F1 silencing on cell cycle and cell growth, respectively. E4F1 silencing inhibited cell growth in TK6‐HT. The results from flow cytometry indicated that the inhibitory effect on cell growth may be the results of the E4F1 silencing–induced accumulation in G2/M compared with TK6‐HT‐shNC. Meanwhile, levels of DNA damage (γ‐H2AX), proteins of Rb and phosphorylated Rb, and reactive oxygen species were increased in TK6‐HT‐shRNA2 cells, which is the critical reason of cell‐cycle arrest. In conclusion, E4F1 silencing inhibits the cell growth through cell‐cycle arrest in malignant transformed cells induced by HQ.