DCLK1 is Overexpressed and Associated with Immune Cell Infiltration in Hepatocellular Carcinoma.

Recent research has shown that Doublecortin-like kinase 1 (DCLK1) is overexpressed in different types of cancer. It has recently been described as a cancer stem cells (CSCs) marker, is associated with carcinogenesis, and positively correlates with infiltration of multiple immune cell types in some cancers. However, studies focused on assessing DCLK1 expression in HCC are limited, and the role of DCLK1 in HCC tumor immunity remains to be determined. In this study, we used a modified model of the resistant hepatocyte (MRHM) to evaluate DCLK1 expression in HCC. Furthermore, DCLK1 expression in HCC was analyzed using TIMER 2.0, UALCAN, GEPIA, GEO, and HPA web-based tools. Correlations between DCLK1 expression and clinicopathological factors in patients were analyzed using the UALCAN web-based tool. Finally, correlations between DCLK1 and immune infiltrates were investigated using the TIMER 2.0 and TISIDB web-based tools. The results showed that DCLK1 is significantly overexpressed during progression of the HCC carcinogenic process in the MRHM. DCLK1 is overexpressed in HCC according to multiple publics web-based tools, and its overexpression is associated with cancer stage. Furthermore, DCLK1 expression was correlated with infiltration levels of multiple immune cells, immunomodulatory factors, immunoinhibitors, MHC molecules, chemokines, receptors, and immune cell-specific markers. These results suggest that DCLK1 is a potential prognostic biomarker that determines cancer progression and correlates with immune cell infiltration in HCC.

Regulation of 4E-BP1 activity in the mammalian oocyte.

Fully grown mammalian oocytes utilize transcripts synthetized and stored during earlier development. RNA localization followed by a local translation is a mechanism responsible for the regulation of spatial and temporal gene expression. Here we show that the mouse oocyte contains 3 forms of cap-dependent translational repressor expressed on the mRNA level: 4E-BP1, 4E-BP2 and 4E-BP3. However, only 4E-BP1 is present as a protein in oocytes, it becomes inactivated by phosphorylation after nuclear envelope breakdown and as such it promotes cap-dependent translation after NEBD. Phosphorylation of 4E-BP1 can be seen in the oocytes after resumption of meiosis but it is not detected in the surrounding cumulus cells, indicating that 4E-BP1 promotes translation at a specific cell cycle stage. Our immunofluorescence analyses of 4E-BP1 in oocytes during meiosis I showed an even localization of global 4E-BP1, as well as of its 4E-BP1 (Thr37/46) phosphorylated form. On the other hand, 4E-BP1 phosphorylated on Ser65 is localized at the spindle poles, and 4E-BP1 phosphorylated on Thr70 localizes on the spindle. We further show that the main positive regulators of 4E-BP1 phosphorylation after NEBD are mTOR and CDK1 kinases, but not PLK1 kinase. CDK1 exerts its activity toward 4E-BP1 phosphorylation via phosphorylation and activation of mTOR. Moreover, both CDK1 and phosphorylated mTOR co-localize with 4E-BP1 phosphorylated on Thr70 on the spindle at the onset of meiotic resumption. Expression of the dominant negative 4E-BP1 mutant adversely affects translation and results in spindle abnormality. Taken together, our results show that the phosphorylation of 4E-BP1 promotes translation at the onset of meiosis to support the spindle assembly and suggest an important role of CDK1 and mTOR kinases in this process. We also show that the mTOR regulatory pathway is present in human oocytes and is likely to function in a similar way as in mouse oocytes.

Temporal and spatial regulation of translation in the mammalian oocyte via the mTOR-eIF4F pathway.

The fully grown mammalian oocyte is transcriptionally quiescent and utilizes only transcripts synthesized and stored during early development. However, we find that an abundant RNA population is retained in the oocyte nucleus and contains specific mRNAs important for meiotic progression. Here we show that during the first meiotic division, shortly after nuclear envelope breakdown, translational hotspots develop in the chromosomal area and in a region that was previously surrounded the nucleus. These distinct translational hotspots are separated by endoplasmic reticulum and Lamin, and disappear following polar body extrusion. Chromosomal translational hotspots are controlled by the activity of the mTOR-eIF4F pathway. Here we reveal a mechanism that-following the resumption of meiosis-controls the temporal and spatial translation of a specific set of transcripts required for normal spindle assembly, chromosome alignment and segregation.