The human genome produces thousands of long noncoding RNAs (lncRNAs)-transcripts >200 nucleotides long that do not encode proteins. Although critical roles in normal biology and disease have been ...revealed for a subset of lncRNAs, the function of the vast majority remains untested. We developed a CRISPR interference (CRISPRi) platform targeting 16,401 lncRNA loci in seven diverse cell lines, including six transformed cell lines and human induced pluripotent stem cells (iPSCs). Large-scale screening identified 499 lncRNA loci required for robust cellular growth, of which 89% showed growth-modifying function exclusively in one cell type. We further found that lncRNA knockdown can perturb complex transcriptional networks in a cell type-specific manner. These data underscore the functional importance and cell type specificity of many lncRNAs.
Alanine, serine, cysteine-preferring transporter 2 (ASCT2; SLC1A5) mediates uptake of glutamine, a conditionally essential amino acid in rapidly proliferating tumour cells. Uptake of glutamine and ...subsequent glutaminolysis is critical for activation of the mTORC1 nutrient-sensing pathway, which regulates cell growth and protein translation in cancer cells. This is of particular interest in breast cancer, as glutamine dependence is increased in high-risk breast cancer subtypes. Pharmacological inhibitors of ASCT2-mediated transport significantly reduced glutamine uptake in human breast cancer cell lines, leading to the suppression of mTORC1 signalling, cell growth and cell cycle progression. Notably, these effects were subtype-dependent, with ASCT2 transport critical only for triple-negative (TN) basal-like breast cancer cell growth compared with minimal effects in luminal breast cancer cells. Both stable and inducible shRNA-mediated ASCT2 knockdown confirmed that inhibiting ASCT2 function was sufficient to prevent cellular proliferation and induce rapid cell death in TN basal-like breast cancer cells, but not in luminal cells. Using a bioluminescent orthotopic xenograft mouse model, ASCT2 expression was then shown to be necessary for both successful engraftment and growth of HCC1806 TN breast cancer cells in vivo. Lower tumoral expression of ASCT2 conferred a significant survival advantage in xenografted mice. These responses remained intact in primary breast cancers, where gene expression analysis showed high expression of ASCT2 and glutamine metabolism-related genes, including GLUL and GLS, in a cohort of 90 TN breast cancer patients, as well as correlations with the transcriptional regulators, MYC and ATF4. This study provides preclinical evidence for the feasibility of novel therapies exploiting ASCT2 transporter activity in breast cancer, particularly in the high-risk basal-like subgroup of TN breast cancer where there is not only high expression of ASCT2, but also a marked reliance on its activity for sustained cellular proliferation.
Ribosome and protein synthesis lie at the core of cell growth and are major consumers of the cellular budget. Here we review recent progress in the coupling of ribosome synthesis and translational ...capacity with cell growth in bacteria. We elaborate on the different strategies of bacteria to modulate the protein synthesis rate at fast and slow growth rates. In particular, bacterial cells maintain translational potential at very slow growth as a strategy to keep fitness in fluctuating environments. We further discuss the important role of ribosome synthesis in rapidly proliferating eukaryotic cells such as yeast cells and cancer cells. The tight relation between ribosome and cell growth provides a broad research avenue for researchers from various disciplines.
At fast growth rates, cellular ribosome synthesis is tightly coupled with cell growth by guanosine tetra- or pentaphosphate (p)ppGpp to attain optimal proteome resource allocation in bacterial cells.Under slow growth conditions, bacterial cells adopt an ingenious strategy to keep translational potential through maintaining both a basal inactive ribosome pool and a moderate translational elongation rate; such a design reflects an adaptive mechanism to fluctuating environments.Ribosome synthesis is also tightly coupled with growth rate in yeast cells, being similar to that in bacterial cells.Excessive ribosome synthesis is crucial for cancer cells to support rapid proliferation and a high protein synthesis rate, and upregulation of ribosome synthesis promotes cancer progression.
Pituitary tumor is one type of endocrine tumor with high incidence and mortality rates. Long non-coding RNAs (lncRNAs) are a family of non-coding RNAs with longer than 200 nucleotides. Among them, ...lncRNA-UCA1 is highly expressed in multiple cancers and plays critically oncogenic roles in tumor progressions. However, the potential roles of UCA1 in human pituitary tumor have not been elucidated. In this study, the expressions of lncRNA-UCA1 were analyzed in thirty pituitary tumor samples and thirty normal pituitary tissues. Cancer cell glycolysis rate was examined by glucose uptake and lactate production. The lncRNA-UCA1 expression was detected by qRT-PCR. Glycolysis enzyme expressions were measured by Western blot and qRT-PCR. Consistent with other cancers, lncRNA-UCA1 was highly expressed in pituitary tumors. Meanwhile, we found glycolysis of pituitary tumors was higher than normal pituitary tissues. Overexpression of lncRNA-UCA1 in rat pituitary cancer cell lines, GH3 and MMQ, significantly promoted glucose uptake and lactate production. In addition, expressions of the glycolysis key enzymes, HK2 and LDHA, were significantly upregulated by exogenous overexpression of lncRNA-UCA1. Importantly, silencing lncRNA-UCA1 obviously inhibited pituitary cancer cells growth and prolactin (PRL) secretion. We report higher lncRNA-UCA1 expression is associated with higher serum PRL level in pituitary patients. Finally, by blocking the lncRNA-UCA1-promoted glycolysis of pituitary cancer cells by glycolysis inhibitor, 2-DG, we obtained recovery of cell growth rate and PRL secretion from an in vitro model. Taken together, our investigation revealed an oncogenic role of lncRNA-UCA1 through upregulating glycolysis of pituitary tumors. This study contributes to underlying molecular mechanisms of the tumorigenesis of pituitary tumors.
Copper is an essential nutrient whose redox properties make it both beneficial and toxic to the cell. Recent progress in studying transition metal signalling has forged new links between researchers ...of different disciplines that can help translate basic research in the chemistry and biology of copper into clinical therapies and diagnostics to exploit copper-dependent disease vulnerabilities. This concept is particularly relevant in cancer, as tumour growth and metastasis have a heightened requirement for this metal nutrient. Indeed, the traditional view of copper as solely an active site metabolic cofactor has been challenged by emerging evidence that copper is also a dynamic signalling metal and metalloallosteric regulator, such as for copper-dependent phosphodiesterase 3B (PDE3B) in lipolysis, mitogen-activated protein kinase kinase 1 (MEK1) and MEK2 in cell growth and proliferation and the kinases ULK1 and ULK2 in autophagy. In this Perspective, we summarize our current understanding of the connection between copper and cancer and explore how challenges in the field could be addressed by using the framework of cuproplasia, which is defined as regulated copper-dependent cell proliferation and is a representative example of a broad range of metalloplasias. Cuproplasia is linked to a diverse array of cellular processes, including mitochondrial respiration, antioxidant defence, redox signalling, kinase signalling, autophagy and protein quality control. Identifying and characterizing new modes of copper-dependent signalling offers translational opportunities that leverage disease vulnerabilities to this metal nutrient.
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