Abstract The mechanisms underlying metabolic adaptation of pancreatic ductal adenocarcinoma (PDA) cells to pharmacologic inhibition of RAS–MAPK signaling are largely unknown. Using transcriptome and chromatin immunoprecipitation profiling of PDA cells treated with the MEK inhibitor (MEKi) trametinib, we identify transcriptional antagonism between c-MYC and the master transcription factors for lysosome gene expression, the MiT/TFE proteins. Under baseline conditions, c-MYC and MiT/TFE factors compete for binding to lysosome gene promoters to fine-tune gene expression. Treatment of PDA cells or patient organoids with MEKi leads to c-MYC downregulation and increased MiT/TFE-dependent lysosome biogenesis. Quantitative proteomics of immunopurified lysosomes uncovered reliance on ferritinophagy, the selective degradation of the iron storage complex ferritin, in MEKi-treated cells. Ferritinophagy promotes mitochondrial iron–sulfur cluster protein synthesis and enhanced mitochondrial respiration. Accordingly, suppressing iron utilization sensitizes PDA cells to MEKi, highlighting a critical and targetable reliance on lysosome-dependent iron supply during adaptation to KRAS–MAPK inhibition. Significance: Reduced c-MYC levels following MAPK pathway suppression facilitate the upregulation of autophagy and lysosome biogenesis. Increased autophagy–lysosome activity is required for increased ferritinophagy-mediated iron supply, which supports mitochondrial respiration under therapy stress. Disruption of ferritinophagy synergizes with KRAS–MAPK inhibition and blocks PDA growth, thus highlighting a key targetable metabolic dependency. See related commentary by Jain and Amaravadi, p. 2023. See related article by Santana-Codina et al., p. 2180. This article is highlighted in the In This Issue feature, p. 2007 

Coordinated Transcriptional and Catabolic Programs Support Iron-Dependent Adaptation to RAS–MAPK Pathway Inhibition in Pancreatic Cancer

Metabolic regulation of somatic stem cells in vivo

/pdf/asymmetric-organelle-inheritance-predicts-human-blood-stem-15ko2dn5.pdf

Asymmetric organelle inheritance predicts human blood stem cell fate

Haematopoietic stem cells (HSCs) are a rare cell type that reconstitute the entire blood and immune systems after transplantation and can be used as a curative cell therapy for a variety of haematological diseases1,2. However, the low number of HSCs in the body makes both biological analyses and clinical application difficult, and the limited extent to which human HSCs can be expanded ex vivo remains a substantial barrier to the wider and safer therapeutic use of HSC transplantation3. Although various reagents have been tested in attempts to stimulate the expansion of human HSCs, cytokines have long been thought to be essential for supporting HSCs ex vivo4. Here we report the establishment of a culture system that allows the long-term ex vivo expansion of human HSCs, achieved through the complete replacement of exogenous cytokines and albumin with chemical agonists and a caprolactam-based polymer. A phosphoinositide 3-kinase activator, in combination with a thrombopoietin-receptor agonist and the pyrimidoindole derivative UM171, were sufficient to stimulate the expansion of umbilical cord blood HSCs that are capable of serial engraftment in xenotransplantation assays. Ex vivo HSC expansion was further supported by split-clone transplantation assays and single-cell RNA-sequencing analysis. Our chemically defined expansion culture system will help to advance clinical HSC therapies. A culture system allows the long-term expansion of human haematopoietic stem cells (HSCs) in vivo without the use of recombinant cytokines or albumin, with potential applications for clinical therapies involving HSCs. 

https://www.researchsquare.com/article/pex-2163/latest.pdf

Darrien Parris

Papers

TFEB-mediated endolysosomal activity controls human hematopoietic stem cell fate.

3232- – inflammatory stress promotes heterogeneous activation of immune response programs in human hematopoietic stem cells

Discovery of a New Human Hematopoietic Stem Cell Involved with Aging That Retains Memory of Immune Activation