SP8 Transcriptional Regulation of Cyclin D1 During Mouse Early Corticogenesis

The Prognostic Role of Cyclin D1 in Multiple Myeloma: A Systematic Review and Meta-Analysis

Purpose: Cyclin D1 has been identified as a proto-oncogene associated with the uncontrolled proliferation of tumor cells. This systematic review and meta-analysis aims to estimate the prognostic significance of cyclin D1 in multiple myeloma (MM) patients. Method: We searched for qualified data in PubMed, Embase, and Web of Science up to February 2020. Data quality was assessed by the Newcastle-Ottawa scale (NOS). Hazard ratios (HRs) and 95% confidence intervals (95% CIs) were used to evaluate the relationship between cyclin D1 expression and overall survival (OS), progression-free survival (PFS)/event-free survival (EFS) in patients with MM. Result: A total of 13 studies involving 961 patients were included. Overall, pooled analysis revealed significant heterogeneity between cyclin D1 expression and the prognosis of MM (OS, HR = 1.08, 95% CI: 0.71-1.64, I2 = 67.9%; PFS/EFS, HR = 0.97, 95% CI: 0.49-1.93, I2 = 85.8%). Subgroup analysis revealed that the prolongation of OS was relevant to increased expression of cyclin D1 in MM patients in the relapsed and refractory group (OS, HR = 0.46, 95% CI: 0.24-0.90). Another subgroup assessment of OS established that MM patients with CCND1 overexpression in the bortezomib group had longer survival time (HR = 0.30, 95% CI: 0.11-0.82), whereas, those overexpressing CCND1 in the conventional chemotherapy group had poor prognosis (HR = 2.19, 95% CI: 1.18-4.08). We also found that increased cyclin D1 expression correlated favorably with PFS in the autologous stem cell transplantation (ASCT) (HR = 0.45, 95% CI: 0.28-0.73) or reverse transcription-polymerase chain reaction (RT-PCR) group (HR = 0.41, 95% CI: 0.26-0.64). Conclusion: The result of this meta-analysis suggested that CCND1 overexpression might be a predictive biomarker for MM patients when treated with bortezomib, receiving ASCT, or in relapsed and refractory period.

Secondary loss of miR-3607 reduced cortical progenitor amplification during rodent evolution

The evolutionary expansion and folding of the mammalian cerebral cortex resulted from amplification of progenitor cells during embryonic development. This process was reversed in the rodent lineage after splitting from primates, leading to smaller and smooth brains. Genetic mechanisms underlying this secondary loss in rodent evolution remain unknown. We show that microRNA miR-3607 is expressed embryonically in the large cortex of primates and ferret, distant from the primate-rodent lineage, but not in mouse. Experimental expression of miR-3607 in embryonic mouse cortex led to increased Wnt/β-catenin signaling, amplification of radial glia cells (RGCs), and expansion of the ventricular zone (VZ), via blocking the β-catenin inhibitor APC (adenomatous polyposis coli). Accordingly, loss of endogenous miR-3607 in ferret reduced RGC proliferation, while overexpression in human cerebral organoids promoted VZ expansion. Our results identify a gene selected for secondary loss during mammalian evolution to limit RGC amplification and, potentially, cortex size in rodents.

PDK1 Regulates the Lengthening of G1 Phase to Balance RGC Proliferation and Differentiation during Cortical Neurogenesis

During cortical development, the balance between progenitor self-renewal and neurogenesis is critical for determining the size/morphology of the cortex. A fundamental feature of the developing cortex is an increase in the length of G1 phase in RGCs over the course of neurogenesis, which is a key determinant of progenitor fate choice. How the G1 length is temporally regulated remains unclear. Here, Pdk1, a member of the AGC kinase family, was conditionally disrupted by crossing an Emx1-Cre mouse line with a Pdk1fl/fl line. The loss of Pdk1 led to a shorter cell cycle accompanied by increased RGC proliferation specifically at late rather than early/middle neurogenic stages, which was attributed to impaired lengthening of G1 phase. Coincidently, apical-to-basal interkinetic nuclear migration was accelerated in Pdk1 cKO cortices. Consequently, we detected an increased neuronal output at P0. We further showed the significant upregulation of the cell cycle regulator cyclin D1 and its activator Myc in the cKO cortices relative to those of control animals. Overall, we have identified a novel role for PDK1 in cortical neurogenesis. PDK1 functions as an upstream regulator of the Myc-cyclin D1 pathway to control the lengthening of G1 phase and the balance between RGC proliferation and differentiation.

Regulation of Neural Stem Cell Competency and Commitment during Indirect Neurogenesis

Indirect neurogenesis, during which neural stem cells generate neurons through intermediate progenitors, drives the evolution of lissencephalic brains to gyrencephalic brains. The mechanisms that specify intermediate progenitor identity and that regulate stem cell competency to generate intermediate progenitors remain poorly understood despite their roles in indirect neurogenesis. Well-characterized lineage hierarchy and available powerful genetic tools for manipulating gene functions make fruit fly neural stem cell (neuroblast) lineages an excellent in vivo paradigm for investigating the mechanisms that regulate neurogenesis. Type II neuroblasts in fly larval brains repeatedly undergo asymmetric divisions to generate intermediate neural progenitors (INPs) that undergo limited proliferation to increase the number of neurons generated per stem cell division. Here, we review key regulatory genes and the mechanisms by which they promote the specification and generation of INPs, safeguarding the indirect generation of neurons during fly larval brain neurogenesis. Homologs of these regulators of INPs have been shown to play important roles in regulating brain development in vertebrates. Insight into the precise regulation of intermediate progenitors will likely improve our understanding of the control of indirect neurogenesis during brain development and brain evolution.

Effects of flavonoids from Rabdosia serra (Maxim.) Hara on proliferation, migration, and invasion of hepatocellular carcinoma cells

AIM

To investigate the effect of flavonoids from Rabdosia serra (Maxim.) Hara on the proliferation, migration, and invasion of human hepatoma HepG2 cells and explore the possible mechanisms involved.

METHODS

After HepG2 cells were treated with various concentrations of flavonoids from Rabdosia serra (Maxim.) Hara (0, 1, 5, 10, 20, or 40 μmol/L), cell viability was determined by CCK-8 assay, cell migration was examined by wound healing assay, and cell invasion was assessed by Transwell assay. Moreover, the protein expression of Notch-1, Cyclin D1, MMP-2, and MMP-9 was detected by Western blot.

RESULTS

CCK-8 assay showed that flavonoids from Rabdosia serra (Maxim.) Hara decreased HepG2 cell viability in a concentration-dependent manner, with the maximal effect observed at 20 μmol/L. Flavonoids from Rabdosia serra (Maxim.) significantly inhibited hepatoma cell migration and invasion. Furthermore, the protein expression of Notch-1, Cyclin D1, MMP-2, and MMP-9 was dramatically decreased after treatment with flavonoids from Rabdosia serra (Maxim.) Hara.

CONCLUSION

Our data demonstrate that the flavonoids from Rabdosia serra (Maxim.) Hara can effectively inhibit human hepatoma HepG2 cell proliferation, migration, and invasion possibly by inhibiting the Notch-1-MMP-2/-9 and Notch-1-Cyclin D1 signaling pathways.