NAC1 attenuates BCL6 negative autoregulation and functions as a BCL6 coactivator of FOXQ1 transcription in cancer cells

An overview of the co-transcription factor NACC1: Beyond its pro-tumor effects

Nucleus accumbens-associated protein 1 (NACC1) is a member of the broad complex, tramtrack, bric-a-brac/poxvirus and zinc finger (BTB/POZ) protein families, mainly exerting its biological functions as a transcription co-regulator. NACC1 forms homo- or hetero-dimers through the BTB/POZ or BANP, E5R, and NACC1 (BEN) domain with other transcriptional regulators to regulate downstream signals. Recently, the overexpression of NACC1 has been observed in various tumors and is positively associated with tumor progression, high recurrence rate, indicating poor prognosis. NACC1 also regulates biological processes such as embryonic development, stem cell pluripotency, innate immunity, and related diseases. Our review combines recent research to summarize advancements in the structure, biological functions, and relative molecular mechanisms of NACC1. The future development of NACC1 clinical appliances is also discussed.

An intellectual-disability-associated mutation of the transcriptional regulator NACC1 impairs glutamatergic neurotransmission

Advances in genome sequencing technologies have favored the identification of rare de novo mutations linked to neurological disorders in humans. Recently, a de novo autosomal dominant mutation in NACC1 was identified (NM_052876.3: c.892C > T, NP_443108.1; p.Arg298Trp), associated with severe neurological symptoms including intellectual disability, microcephaly, and epilepsy. As NACC1 had never before been associated with neurological diseases, we investigated how this mutation might lead to altered brain function. We examined neurotransmission in autaptic glutamatergic mouse neurons expressing the murine homolog of the human mutant NACC1, i.e., Nacc1-R284W. We observed that expression of Nacc1-R284W impaired glutamatergic neurotransmission in a cell-autonomous manner, likely through a dominant negative mechanism. Furthermore, by screening for Nacc1 interaction targets in the brain, we identified SynGAP1, GluK2A, and several SUMO E3 ligases as novel Nacc1 interaction partners. At a biochemical level, Nacc1-R284W exhibited reduced binding to SynGAP1 and GluK2A, and also showed greatly increased SUMOylation. Ablating the SUMOylation of Nacc1-R284W partially restored its interaction with SynGAP1 but did not restore binding to GluK2A. Overall, these data indicate a role for Nacc1 in regulating glutamatergic neurotransmission, which is substantially impaired by the expression of a disease-associated Nacc1 mutant. This study provides the first functional insights into potential deficits in neuronal function in patients expressing the de novo mutant NACC1 protein.

miR-18a-5p derived from mesenchymal stem cells-extracellular vesicles inhibits ovarian cancer cell proliferation, migration, invasion, and chemotherapy resistance

OBJECTIVE

Ovarian cancer (OC) is a major threat to women's health. Mesenchymal stem cells (MSCs) are key regulators in cellular communication by secreting extracellular vesicles (EVs) that are involved in OC. This study probed into the mechanism of human MSCs derived-EVs (hMSC-EVs) in regulating OC cell growth and chemotherapy resistance.

METHODS

hMSCs and EVs were isolated and identified. After adding EVs, the uptake of EVs by OC CAOV3/ES2 cells (for in vitro studies), and cell proliferation, migration, and invasion were detected. Downregulated miRNAs in hMSC-EVs were screened and miR-18a-5p expression in OC patients was detected. The prognosis of OC patients was analyzed. Binding sites of miR-18a-5p and NACC1 were predicted and validated. NACC1 expression in OC tissues was measured by RT-qPCR, and its correlation with miR-18a-5p was analyzed by Pearson method. AKT/mTOR pathway activation was assessed by WB. The cisplatin sensitivity of EVs-treated CAOV3 cells was evaluated via MTT assay and tested by tumor formation assay in nude mice.

RESULTS

hMSC-EVs suppressed OC cell proliferation, migration, and invasion. miR-18a-5p was downregulated in OC and miR-18a-5p low expression was associated with a poor prognosis. EV-encapsulated miR-18a-5p targeted NACC1. NACC1 was upregulated in OC tissues. miR-18a-5p knockdown and NACC1 overexpression both annulled the inhibition of hMSC-EVs on OC cell growth. AKT and mTOR were elevated in OC and NACC1 activated the AKT/mTOR pathway in OC cells. hMSC-EVs promoted cisplatin sensitivity of OC cells by carrying miR-18a-5p.

CONCLUSION

hMSC-EVs-derived miR-18a-5p inhibits OC cell proliferation, migration, invasion, and chemotherapy resistance.

Transcriptional inhibition of miR-486-3p by BCL6 upregulates Snail and induces epithelial-mesenchymal transition during radiation-induced pulmonary fibrosis

Background

Ionizing radiation (IR) can induce pulmonary fibrosis by causing epithelial mesenchymal transition (EMT), but the exact mechanism has not been elucidated. To investigate the molecular mechanism of how radiation induces pulmonary fibrosis by altering miR-486-3p content and thus inducing EMT.

Methods

The changes of miR-486-3p in cells after irradiation were detected by RT-qPCR. Western blot was used to detect the changes of cellular epithelial marker protein E-cadherin, mesenchymal marker N-cadherin, Vimentin and other proteins. The target gene of miR-486-3p was predicted by bioinformatics method and the binding site was verified by dual luciferase reporter system. In vivo experiments, adeno-associated virus (AAV) was used to carry miR-486-3p mimic to lung. Radiation-induced pulmonary fibrosis (RIPF) model was constructed by 25Gy⁶⁰Co γ-rays. The structural changes of mouse lung were observed by HE and Masson staining. The expression of relevant proteins in mice was detected by immunohistochemistry.

Results

IR could decrease the miR-486-3p levels in vitro and in vivo, and that effect was closely correlated to the occurrence of RIPF. The expression of Snail, which induces EMT, was shown to be restrained by miR-486-3p. Therefore, knockdown of Snail blocked the EMT process induced by radiation or knockdown of miR-486-3p. In addition, the molecular mechanism underlying the IR-induced miRNA level reduction was explored. The increased in BCL6 could inhibit the formation of pri-miR-486-3p, thereby reducing the levels of miR-486-3p in the alveolar epithelial cells, which would otherwise promote EMT and contribute to RIPF by targeting Snail.

Conclusion

IR can exacerbate RIPF in mice by activating the transcription factor BCL6, which inhibits the transcription of miR-486-3p and decreases its content, which in turn increases the content of the target gene slug and triggers EMT.

Inhibition of CXCR2 plays a pivotal role in re-sensitizing ovarian cancer to cisplatin treatment

cDNA microarray data conducted by our group revealed overexpression of CXCL2 and CXCL8 in ovarian cancer (OC) microenvironment. Herein, we have proven that the chemokine receptor, CXCR2, is a pivotal molecule in re-sensitizing OC to cisplatin, and its inhibition decreases cell proliferation, viability, tumor size in cisplatin-resistant cells, as well as reversed the overexpression of mesenchymal epithelium transition markers. Altogether, our study indicates a central effect of CXCR2 in preventing tumor progression, due to acquisition of cisplatin chemoresistant phenotype by tumor cells, and patients' high lethality rate. We found that the overexpression of CXCR2 by OC cells is persistent and anomalously confined to the cellular nuclei, thus pointing to an urge in developing highly lipophilic molecules that promptly permeate cells, bind to and inhibit nuclear CXCR2 to fight OC, instead of relying on the high-cost genetic engineered cells.

ALOX5AP Predicts Poor Prognosis by Enhancing M2 Macrophages Polarization and Immunosuppression in Serous Ovarian Cancer Microenvironment

Background

Serous ovarian cancer (SOC) is a highly lethal gynecological malignancy with poor prognosis. Given the importance of the immune-related tumor microenvironment (TME) in ovarian cancer, investigating tumor-immune interactions and identifying novel prognostic and therapeutic targets in SOC is a promising avenue of research. ALOX5AP (Arachidonate 5-Lipoxygenase Activating Protein) is a key enzyme in converting arachidonic acid to leukotriene: a crucial immune-modulating lipid mediator. However, the role of ALOX5AP in SOC has yet to be studied.

Methods

ALOX5AP expression patterns across ovarian cancer and their normal tissue counterparts were cross-checked using public microarray and RNA-seq analyses and then validated in clinical samples by qRT-PCR. Kaplan-Meier survival analysis was performed in multiple independent SOC patient cohorts. Univariate and multivariate Cox regression analysis were then employed to identify clinical risk parameters associated with survival, and a genomic-clinicopathologic nomogram was built. Gene enrichment, immune infiltration, and immunosuppressor correlation analyses were then evaluated.

Results

ALOX5AP mRNA levels in SOC tissues were significantly upregulated compared to normal tissues. Elevated ALOX5AP was markedly associated with poor overall survival and progression-free survival in multiple SOC patient cohorts as well as with adverse clinicopathological features, including lymphatic invasion, unsatisfactory cytoreductive surgery, rapid relapse after primary treatment, and platinum non-responsiveness. A predictive nomogram, which integrated ALOX5AP expression and two independent prognosis factors (primary therapy outcome and tumor residual), was conducted to predict the 3-year and 5-year survival rate of SOC patients. Mechanistically, functional and pathway enrichment analyses revealed that ALOX5AP was primarily involved in immune response and regulation. Further exploration demonstrated that ALOX5AP was highly expressed in the immunoreactive subtype of ovarian cancer and closely related to immunocyte infiltration, especially M2 macrophage polarization. Additionally, ALOX5AP was enriched in the C4 (lymphocyte depleted) immune subtype of SOC and associated with crucial immune-repressive receptors in the tumor microenvironment at the genomic level.

Conclusions

ALOX5AP expression indicates a worse survival outcome and has the potential to be utilized as a prognostic predictor for SOC patients. Given the availability of well-studied ALOX5AP inhibitors, this study has immediate clinical implications for the exploitation of ALOX5AP as an immunotherapeutic target in SOC.