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Essential amino acids (EAA) and microRNAs (miRs) control biological activity of a cell. Whether EAA regulates the activity of miR has never been demonstrated. Here, as proof‐of‐concept, a tryptophan (Trp, an EAA) complex containing Argonaute 2 (Ago2) and miRs including miR‐193a (Trp/Ago2/miR‐193a) is identified. Trp binds miR‐193a‐3p and interacts with Ago2. Trp/Ago2/miR‐193a increases miR‐193a‐3p activity via enhancing Argonaute 2 (Ago2) RNase activity. Other miRs including miR‐103 and miR‐107 in the Trp complex enhance miR‐193a activity by targeting the same genes. Mechanistically, the Trp/Ago2/miR‐193a complex interacts with Trp‐binding pockets of the PIWI domain of Ago2 to enhance Ago2 mediated miR activity. This newly formed Ago2/Trp/miR‐193a‐3p complex is more efficient than miR‐193a‐3p alone in inhibiting the expression of targeted genes and inhibiting colon cancer liver metastasis. The findings show that Trp regulates miR activity through communication with the RNA‐induced silencing complexes (RISC), which provides the basis for tryptophan based miR therapy. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to explore the potential mechanism of circular RNA (circRNA) CirCHIPK3 on the malignant proliferation and metastasis of breast cancer (BC). Methods: Human BC samples and their matched normal adjacent tissues were obtained from 50 patients to assess the expression of CirCHIPK3 and its relationship with BC prognosis. A series of in vitro and in vivo functional experiments were carried out to elucidate the role of CirCHIPK3 in BC progression and its underlying molecular mechanisms. Moreover, the interaction of CirCHIPK3, miR‐193a, and HMGB1 was examined using bioinformatics, FISH, RIP, RNA‐pull down and luciferase reporter assays. Western blot analysis was performed to examine the expression of HMGB1, p‐PI3K, total PI3K, p‐AKT, and AKT after si‐CirCHIPK3 transfection. Results: Upregulation of CirCHIPK3 was identified in BC, which predicted a worse prognosis in BC patients. Furthermore, it was found that CirCHIPK3 facilitated cell proliferation, migration, and invasion in BC by regulating miR‐193a/HMGB1/PI3K/AKT signaling. CirCHIPK3 acted as a sponge for miR‐193a to facilitate HMGB1 expression. si‐CirCHIPK3 also inhibited tumor growth of BC in nude mice. si‐CircCHIPK3 decreased HMGB1/PI3K/AKT signal expression in MDA‐MB‐231 cells, whereas overexpression of CircCHIPK3 enhanced HMGB1/PI3K/AKT signal. Conclusions: CirCHIPK3 regulated miR‐193a/HMGB1/PI3K/AKT signaling to facilitate BC development and progression, providing a novel therapeutic target for BC. [ABSTRACT FROM AUTHOR]

AML1‐ETO, the most common fusion oncoprotein by t (8;21) in acute myeloid leukaemia (AML), enhances hematopoietic self‐renewal and leukemogenesis. However, currently no specific therapies have been reported for t (8;21) AML patients as AML1‐ETO is still intractable as a pharmacological target. For this purpose, leukaemia cells and AML1‐ETO‐induced murine leukaemia model were used to investigate the degradation of AML1‐ETO by melatonin (MLT), synthesized and secreted by the pineal gland. MLT remarkedly decreased AML1‐ETO protein in leukemic cells. Meanwhile, MLT induced apoptosis, decreased proliferation and reduced colony formation. Furthermore, MLT reduced the expansion of human leukemic cells and extended the overall survival in U937T‐AML1‐ETO‐xenografted NSG mice. Most importantly, MLT reduced the infiltration of leukaemia blasts, decreased the frequency of leukaemia stem cells (LSCs) and prolonged the overall survival in AML1‐ETO‐induced murine leukaemia. Mechanistically, MLT increased the expression of miR‐193a, which inhibited AML1‐ETO expression via targeting its putative binding sites. Furthermore, MLT decreased the expression of β‐catenin, which is required for the self‐renewal of LSC and is the downstream of AML1‐ETO. Thus, MLT presents anti‐self‐renewal of LSC through miR‐193a‐AML1‐ETO‐β‐catenin axis. In conclusion, MLT might be a potential treatment for t (8;21) leukaemia by targeting AML1‐ETO oncoprotein. [ABSTRACT FROM AUTHOR]

Ovarian cancer is the most lethal cancer of the female reproductive system. In that regard, several epidemiological studies suggest that long‐term exposure to estrogen could increase ovarian cancer risk, although its precise role remains controversial. To decipher a mechanism for this, we previously generated a mathematical model of how estrogen‐mediated upregulation of the transcription factor, E2F6, upregulates the ovarian cancer stem/initiating cell marker, c‐Kit, by epigenetic silencing the tumor suppressor miR‐193a, and a competing endogenous (ceRNA) mechanism. In this study, we tested that previous mathematical model, showing that estrogen treatment of immortalized ovarian surface epithelial cells upregulated both E2F6 and c‐KIT, but downregulated miR‐193a. Luciferase assays further confirmed that microRNA‐193a targets both E2F6 and c‐Kit. Interestingly, ChIP‐PCR and bisulphite pyrosequencing showed that E2F6 also epigenetically suppresses miR‐193a, through recruitment of EZH2, and by a complex ceRNA mechanism in ovarian cancer cell lines. Importantly, cell line and animal experiments both confirmed that E2F6 promotes ovarian cancer stemness, whereas E2F6 or EZH2 depletion derepressed miR‐193a, which opposes cancer stemness, by alleviating DNA methylation and repressive chromatin. Finally, 118 ovarian cancer patients with miR‐193a promoter hypermethylation had poorer survival than those without hypermethylation. These results suggest that an estrogen‐mediated E2F6 ceRNA network epigenetically and competitively inhibits microRNA‐193a activity, promoting ovarian cancer stemness and tumorigenesis. Estrogen‐mediated E2F6 competing endogenous network epigenetically and competitively inhibits microRNA‐193a activity, promoting ovarian cancer stemness and tumorigenesis. [ABSTRACT FROM AUTHOR]

Abstract: Although dexamethasone (DEX) remains a first‐line agent for multiple myeloma (MM) therapy, the development of DEX resistance has become an indicator of poor prognosis in MM patients. It is thus urgent to develop strategies to restore the vulnerability of MM to DEX. This study demonstrated long non‐coding RNA (lncRNA) nuclear paraspeckle assembly transcript 1 (NEAT1) was highly expressed in DEX‐resistant myeloma cell lines, and upregulation of NEAT1 was tightly linked to poor prognosis. The in‐depth study revealed that during the development of DEX resistance in these cells, the miR‐193a levels were decreased, which resulted in the increased expression of the target gene myeloid cell leukemia‐1 (MCL1). We also found knockdown of NEAT1, the DEX‐induced sensitivity was enhanced in the resistant cells. Meanwhile, overexpression of NEAT1 increased the DEX‐induced resistance in the sensitive cells. In conclusion, the NEAT1/miR‐193a/MCL1 pathway is closely associated with the development of DEX resistance in myeloma cells, and knockdown of NEAT1 can significantly improve DEX sensitivity in MM. [ABSTRACT FROM AUTHOR]

HOTAIR is significantly overexpressed in various cancers and facilitates tumor invasion and metastasis. However, whether HOTAIR plays oncogenic roles in acute myeloid leukemia (AML) is still unknown. Here, we report that HOTAIR expression was obviously increased in leukemic cell lines and primary AML blasts. Clinically, AML patients with higher HOTAIR predicted worse clinical outcome compared with those with lower HOTAIR. Importantly, HOTAIR knockdown by small hairpin RNA inhibited cell growth, induced apoptosis, and decreased number of colony formation. Finally, HOTAIR modulated c-KIT expression by competitively binding miR-193a. Collectively, our data suggest that HOTAIR plays an important oncogenic role in AML and might serve as a marker for AML prognosis and a potential target for therapeutic intervention. [ABSTRACT FROM AUTHOR]