RELB Alters Proliferation of Human Pluripotent Stem Cells via IMP3- and LIN28-Mediated Modulation of the Expression of IGF2 and Other Cell-Cycle Regulators

Liver cancer initiation requires translational activation by an oncofetal regulon involving LIN28 proteins

It is unknown which posttranscriptional regulatory mechanisms are required for oncogenic competence. Here, we show that the LIN28 family of RNA-binding proteins (RBPs), which facilitate posttranscriptional RNA metabolism within ribonucleoprotein networks, is essential for the initiation of diverse oncotypes of hepatocellular carcinoma (HCC). In HCC models driven by NRASG12V/Tp53, CTNNB1/YAP/Tp53, or AKT/Tp53, mice without Lin28a and Lin28b were markedly impaired in cancer initiation. We biochemically defined an oncofetal regulon of 15 factors connected to LIN28 through direct mRNA and protein interactions. Interestingly, all were RBPs and only 1 of 15 was a Let-7 target. Polysome profiling and reporter assays showed that LIN28B directly increased the translation of 8 of these 15 RBPs. As expected, overexpression of LIN28B and IGFBP1-3 was able to genetically rescue cancer initiation. Using this platform to probe components downstream of LIN28, we found that 8 target RBPs were able to restore NRASG12V/Tp53 cancer formation in Lin28a/Lin28b-deficient mice. Furthermore, these LIN28B targets promote cancer initiation through an increase in protein synthesis. LIN28B, central to an RNP regulon that increases translation of RBPs, is important for tumor initiation in the liver.

BRD4/nuclear PD-L1/RelB circuit is involved in the stemness of breast cancer cells

BACKGROUND

Breast cancer (BC) is the most common cancer diagnosed in women worldwide. BC stem cells (BCSCs) have been known to be involved in the carcinogenesis of the breast and contribute to therapeutic resistance. The programmed death-ligand 1 (PD-L1) expression of BC correlated with a poor prognosis. Immunotherapies that target PD-L1 have great potential and have been successful when applied to cancer treatment. However, whether PD-L1 regulates BCSC formation is unknown.

METHODS

BCSCs were enriched by serum-free suspension culture. The properties of BCSCs were examined by mammosphere formation assay, CD44+/Cd24-, aldehyde dehydrogenase (ALDH) assay, CSC marker analysis, and mammosphere growth assay. To elucidate the functions of bromodomain-containing protein 4 (BRD4), nuclear PD-L1, and RelB proteins in the stemness of BCSCs, mammosphere formation was examined using BRD4 inhibitor and degrader, PD-L1 degrader, and RelB inhibitor. The antitumor function of 3',4',7,8-tetrahydroxyflavone (THF), a specific BRD4 inhibitor, was studied through in vivo tumor model and mouse studies, and the protein levels of c-Myc, PD-L1, and RelB were examined in tumor model under THF treatment.

RESULTS

BRD4 was upregulated in breast CSCs and regulates the stemness of BCs. The downregulation of BRD4 using BRD4 PROTAC, ARV-825, and BRD4 inhibitor, (+)-JQ1, inhibits mammosphere formation and reduces the levels of breast CSC markers (CD44+/CD24- and ALDH1), stem cell marker genes, and mammosphere growth. BRD4 inhibitor (JQ1) and degrader (ARV825) downregulate membrane and nuclear fractions of PD-L1 through the inhibition of PD-L1 transcript levels. The knockdown of PD-L1 inhibits mammosphere formation. Verteporfin, a PD-L1 degrader, inhibits the transcripts and protein levels of PD-L1 and downregulates the transcript and protein levels of RelB. Calcitriol, a RelB inhibitor, and the knockdown of RelB using si-RelB regulate mammosphere formation through interleukin-6 (IL-6) expression. THF is a natural product and a potent selective BRD4 inhibitor, inhibits mammosphere formation, and reduces the levels of CD44+/CD24- and mammosphere growth by downregulating c-Myc, PD-L1, and RelB. 3',4',7,8-THF shows tumoricidal activity and increased levels of CD3+CD4+ and CD3+CD8+ T-cells in the tumor and tumor-draining lymph nodes (TDLNs) in the murine tumor model using 4T1 and MC38 cells.

CONCLUSIONS

The results show the first evidence of the essential role of the BRD4/nuclear PD-L1/RelB axis in breast CSC formation. The nuclear PD-L1 regulates RelB, and the RelB/p65 complex induces IL6 and breast CSC formation. Targeting nuclear PD-L1 represents a potential and novel tool for immunotherapies of intractable BC. Video Abstract.

Ascorbic acid protects retinal pigment epithelial cells from high glucose by inhibiting the NF-κB signal pathway through MALAT1/IGF2BP3 axis

BACKGROUND

Diabetic retinopathy (DR) is a common complication of diabetes with nocuous effects on patients' eye health, typically accompanies by excessive inflammation and oxidative stress. Insulin-like growth factor-2 messenger RNA-binding protein 3 (IGF2BP3) was engaged with inflammation, whereas its precise role in the DR process was unclear. And enhanced lncRNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and decreased ascorbic acid (AA) were also found in DR. This study was to explore the regulatory role and mechanism of IGF2BP3, MALAT1 and AA in the high glucose (HG)-induced retinal pigment epithelial (RPE) cell injury.

METHODS

ARPE-19 cells were treated with HG to establish the in vitro RPE cell injury model. The mRNA and protein levels of the gene were evaluated by qRT-PCR or Western blot. Immunofluorescence detected the translocation condition of the p65 protein. Inflammatory factor levels were detected by ELISA assays. Apoptosis was detected by flow cytometry. The binding interaction of IGF2BP3 and MALAT1 was validated by RIP-qPCR assays.

RESULTS

In HG-induced RPE cell injury, IGF2BP3 expression, inflammatory response and apoptosis were enhanced. Next, the IGF2BP3 activated the NF-κB signalling to promote the RPE cell injury development. MALAT1 could directly bind with IGF2BP3 and up-regulate its expression. In addition, AA ameliorated the HG-induced RPE cell injury through the regulation of MALAT1.

CONCLUSION

Ascorbic acid ameliorated HG-induced RPE cell injury by repressing the NF-κB signalling pathway via modulating the MALAT1/IGF2BP3 axis.

LIN28A inhibits lysosome‑associated membrane glycoprotein 1 protein expression in embryonic stem and bladder cancer cells

Tumor cells and embryonic stem cells (ESCs) have similar transcription mechanisms. LIN28A is an important factor in tumor cells and ESCs, it is an inhibitor of intracellular endoplasmic reticulum (ER)‑related protein translation in ESCs. The present study aimed to examine the effects of LIN28A on an ER‑related protein, lysosome‑associated membrane glycoprotein 1 (LAMP1), in human bladder cancer cells and mouse (m)ESCs, using reverse transcription‑quantitative polymerase chain reaction and western blotting to detect the expression of LAMP1 mRNA and protein, respectively, following LIN28A knockdown. LIN28A was revealed to promote the proliferation, migration and invasion in human bladder cancer cells. These data suggested similarities between ESC cells and cancer cells and may provide novel ideas for the use of induced embryonic stem cell differentiation to treat tumors.

Transcriptome analysis and identification of significantly differentially expressed genes in Holstein calves subjected to severe thermal stress

RNA-Seq analysis was used to characterize transcriptome response of Holstein calves to thermal stress. A total of eight animals aged between 2 and 3 months were randomly selected and subjected to thermal stress corresponding to a temperature humidity index of 95 in an environmentally controlled house for 12 h consecutively for 3 days. A set of 15,787 unigenes were found to be expressed and after a threshold of threefold change, and a Q value <0.05; 502, 394, and 376 genes were found to be differentially expressed on days 1, 2, and 3 out of which 343, 261 and 256 genes were upregulated and 159, 133, and 120 genes were downregulated. Only 356 genes out of these were expressed on all 3 days, and only they were considered as significantly differentially expressed. KEGG pathway analysis revealed that ten pathways were significantly enriched; the top two among them were protein processing in endoplasmic reticulum and MAPK signaling pathways. These results suggest that thermal stress triggered a complex response in Holstein calves and the animals adjusted their physiological and metabolic processes to survive. Many of the genes identified in this study have not been previously reported to be involved in thermal stress response. The results of this study extend our understanding of the animal's response to thermal stress and some of the identified genes may prove useful in the efforts to breed Holstein cattle with superior thermotolerance, which might help in minimizing production loss due to thermal stress.

Effects of oxidative and thermal stresses on stress granule formation in human induced pluripotent stem cells

Stress Granules (SGs) are dynamic ribonucleoprotein aggregates, which have been observed in cells subjected to environmental stresses, such as oxidative stress and heat shock (HS). Although pluripotent stem cells (PSCs) are highly sensitive to oxidative stress, the role of SGs in regulating PSC self-renewal and differentiation has not been fully elucidated. Here we found that sodium arsenite (SA) and HS, but not hydrogen peroxide (H₂O₂), induce SG formation in human induced (hi) PSCs. Particularly, we found that these granules contain the well-known SG proteins (G3BP, TIAR, eIF4E, eIF4A, eIF3B, eIF4G, and PABP), were found in juxtaposition to processing bodies (PBs), and were disassembled after the removal of the stress. Moreover, we showed that SA and HS, but not H₂O₂, promote eIF2α phosphorylation in hiPSCs forming SGs. Analysis of pluripotent protein expression showed that HS significantly reduced all tested markers (OCT4, SOX2, NANOG, KLF4, L1TD1, and LIN28A), while SA selectively reduced the expression levels of NANOG and L1TD1. Finally, in addition to LIN28A and L1TD1, we identified DPPA5 (pluripotent protein marker) as a novel component of SGs. Collectively, these results provide new insights into the molecular cues of hiPSCs responses to environmental insults.

Lin28 and let-7: roles and regulation in liver diseases

The diagnosis and treatment of liver disease remain a major health concern worldwide because of the diverse etiologies of this disease. For this reason, new therapeutic targets are greatly needed to halt the progression of this damaging disease. Upon initiation of liver injury by viral infection, autoimmune disease or toxin, and/or hepatitis, chronic disease may develop, which can progress to cirrhosis, hepatocellular carcinoma (HCC), cholangiocarcinoma, liver failure, or death. The Lin28/lethal-7 (let-7) molecular switch has emerged as a central regulator of multiorgan injuries and cancer development. Lin28 is a stem cell marker vital to initiation or maintenance of a stem cell phenotype. Lin28 has not been extensively studied in the liver, despite its ability to induce tissue regeneration via reprogramming of oxidative enzymes in other tissues and its involvement with numerous upstream regulators and downstream targets in liver disease. Theoretically, overexpression of Lin28 in certain forms of liver disease could be a potential treatment that aids in liver regeneration. Alternatively, Lin28 has been implicated numerous times in the progression of diverse cancer types and is associated with increased severity of disease. In this case, Lin28 could be a potential inhibitory target to prevent malignant transformation in the liver. This review seeks to characterize the role of Lin28 in liver disease.