Molecular and Cellular Biology最新文献

Pancreatic ductal adenocarcinoma (PDAC) remains largely refractory to therapy, due in part to the complex interplay between tumor cells and their microenvironment. Human antigen R (HuR/ELAVL1), a ubiquitously expressed RNA-binding protein, is emerging as an important regulator both of tumor-intrinsic and tumor-extrinsic pathways that govern PDAC progression. While the role of HuR in promoting cancer cell survival under stress is well established, recent studies reveal its broader role in shaping the tumor microenvironment (TME), including metabolic rewiring, stromal activation, angiogenesis, and immune modulation. In this review, we examine how tumor-intrinsic HuR drives epithelial-mesenchymal transition, stabilizes key transcripts involved in metabolic adaptation, and alters the tumor secretome to influence extracellular matrix deposition and fibroblast behavior. We further explore the role of HuR in regulating immune cell function and the immune landscape of PDAC. Notably, HuR-driven TME remodeling reinforces environmental stressors that further activate HuR, establishing a feed-forward loop that drives disease progression. These findings underscore HuR as a central regulator of the PDAC TME and therapeutic resistance, and thus, highlight its potential as a target in PDAC.

Chromosomal instability (CIN), a major hallmark of cancer, can be driven by defects in the integrity of centromere or kinetochore structure. Coordinated control of phosphorylation and dephosphorylation activities during cell division is critical to ensure chromosomal stability. Overexpression of the centromeric histone H3 variant CENP-A is observed in many cancers, and its mislocalization to noncentromeric regions promotes CIN. We identified protein phosphatase 1 (PP1) nuclear targeting subunit (PNUTS) as a top candidate in a genome-wide siRNA screen for gene depletions that lead to increased nuclear CENP-A levels. Here, we define a role for PNUTS in preventing CENP-A mislocalization and CIN. Depletion of PNUTS resulted in high nuclear CENP-A levels throughout the cell cycle in a PP1-dependent manner. Consistent with these results, mislocalization of CENP-A and its interacting partner CENP-C were observed on mitotic chromosomes from PNUTS-depleted cells. Defects in kinetochore integrity and CIN phenotypes were also observed in PNUTS-depleted cells. Mechanistically, we show that depletion of the histone H3.3 chaperone DAXX suppresses the mislocalization of CENP-A and micronuclei incidence in PNUTS-depleted cells. In summary, our studies highlight the importance of phospho-regulation mediated by PNUTS in preventing CENP-A mislocalization and CIN.

Here, we report a novel role for the yeast lysine acetyltransferase NuA4 in regulating phospholipid availability for organelle morphology. Disruption of the NuA4 complex results in 70% of cells displaying nuclear deformations and nearly 50% of cells exhibiting vacuolar fragmentation. Cells deficient in NuA4 also show severe defects in the formation of nuclear-vacuole junctions (NJV), as well as a decrease in piecemeal microautophagy of the nucleus (PMN). To determine the cause of these defects we focused on Pah1, an enzyme that converts phosphatidic acid into diacylglycerol, favoring accumulation of lipid droplets over phospholipids that are used for membrane expansion. NuA4 subunit Eaf1 was required for Pah1 localization to the inner nuclear membrane and artificially tethering of Pah1 to the nuclear membrane rescued nuclear deformation and vacuole fragmentation defects, but not defects related to the formation of NVJs. Mutation of a NuA4-dependent acetylation site on Pah1 also resulted in aberrant Pah1 localization and defects in nuclear morphology and NVJ. Our work suggests a critical role for NuA4 in organelle morphology that is partially mediated through the regulation of Pah1 subcellular localization.

Osteoarthritis (OA) is a chronic degenerative disease characterized by subchondral osteosclerosis, mainly due to osteoblast activity. This research investigates the function of Sik1, a member of the AMP-activated protein kinase family, in OA. Proteomic analysis was conducted on clinical samples from 30 OA patients, revealing a negative correlation between Sik1 expression and OA. In vitro experiments utilized BMSCs to examine the effect of Sik1 on osteogenic differentiation. BMSCs were cultured and induced toward osteogenesis with specific media. Sik1 overexpression was achieved through lentiviral transfection, followed by analysis of osteogenesis-associated proteins using Western blotting, RT-qPCR, and alkaline phosphate staining. In vivo experiments involved destabilizing the medial meniscus in mice to establish an OA model, assessing the therapeutic potential of Sik1. The CT scans and histological staining were used to analyze subchondral bone alterations and cartilage damage. The findings show that Sik1 downregulation correlates with advanced OA and heightened osteogenic differentiation in BMSCs. Sik1 overexpression inhibits osteogenesis-related markers in vitro and reduces cartilage damage and subchondral osteosclerosis in vivo. Mechanistically, Sik1 modulates osteogenesis and subchondral bone changes through Runx2 activity regulation. The research emphasizes Sik1 as a promising target for treating OA, suggesting its involvement in controlling bone formation and changes in the subchondral osteosclerosis.

Androgen receptor inhibitors are commonly used for prostate cancer treatment, but acquired resistance is a significant problem. Codeletion of RB and p53 is common in castration resistant prostate cancers, however they are difficult to target pharmacologically. To comprehensively identify gene loss events that contribute to enzalutamide response, we performed a genome-wide CRISPR knockout screen in LNCaP prostate cancer cells. This revealed novel genes implicated in resistance that are largely unstudied. Gene loss events that confer enzalutamide sensitivity are enriched for GSEA categories related to stem cell and epigenetic regulation. We investigated the myeloid lineage stem cell factor HOXA9 as a candidate gene whose loss promotes sensitivity to enzalutamide. Cancer genomic data reveals that HOXA9 overexpression correlates with poor prognosis and characteristics of advanced prostate cancer. In cell culture, HOXA9 depletion sensitizes cells to enzalutamide, whereas overexpression drives enzalutamide resistance. Combination of the HOXA9 inhibitor DB818 with enzalutamide demonstrates synergy. This demonstrates the utility of our CRISPR screen data in discovering new approaches for treating enzalutamide resistant prostate cancer.

A resident vascular endothelial stem cell (VESC) population expressing CD157 has been identified recently in mice. Herein, we identified transcription factors (TFs) regulating CD157 expression in endothelial cells (ECs) that were associated with drug resistance, angiogenesis, and EC proliferation. In the first screening, we detected 20 candidate TFs through the CD157 promoter and gene expression analyses. We found that 10 of the 20 TFs induced CD157 expression in ECs. We previously reported that 70% of CD157 VESCs were side population (SP) ECs that abundantly expressed ATP-binding cassette (ABC) transporters. Here, we found that the 10 TFs increased the expression of several ABC transporters in ECs and increased the proportion of SP ECs. Of these 10 TFs, we found that six (Atf3, Bhlhe40, Egr1, Egr2, Elf3, and Klf4) were involved in the manifestation of the SP phenotype. Furthermore, the six TFs enhanced tube formation and proliferation in ECs. Single-cell RNA sequence data in liver ECs suggested that Atf3 and Klf4 contributed to the production of CD157⁺ VESCs in the postnatal period. We concluded that Klf4 might be important for the development and maintenance of liver VESCs. Our work suggests that a TF network is involved in the differentiation hierarchy of VESCs.