"Stress-Mediated Reprogramming of Prostate Cancer One-Carbon Cycle Drives Disease Progression"
Omer Faruk Kuzu (Researcher, Fahri Saatcioglu group, IBV)
One-carbon (1C) metabolism has a key role in metabolic programming with both mitochondrial (m1C) and cytoplasmic (c1C) components. Here we show that activating transcription factor 4 (ATF4) exclusively activates gene expression involved in m1C, but not the c1C cycle in prostate cancer cells. This includes activation of methylenetetrahydrofolate dehydrogenase 2 (MTHFD2) expression, the central player in the m1C cycle. Consistent with the key role of m1C cycle in prostate cancer, MTHFD2 knockdown inhibited prostate cancer cell growth, prostatosphere formation, and growth of patient-derived xenograft organoids. In addition, therapeutic silencing of MTHFD2 by systemically administered nanoliposomal siRNA profoundly inhibited tumor growth in preclinical prostate cancer mouse models. Consistently, MTHFD2 expression is significantly increased in human prostate cancer, and a gene expression signature based on the m1C cycle has significant prognostic value. Furthermore, MTHFD2 expression is coordinately regulated by ATF4 and the oncoprotein c-MYC, which has been implicated in prostate cancer. These data suggest that the m1C cycle is essential for prostate cancer progression and may serve as a novel biomarker and therapeutic target. SIGNIFICANCE: These findings demonstrate that the mitochondrial, but not cytoplasmic, one-carbon cycle has a key role in prostate cancer cell growth and survival and may serve as a biomarker and/or therapeutic target.
"Contour Learning Localization Provides Super Resolution Tracking of Endosome Maturation in Extended Field of Depth Microscopy"
Edna Xian Hu (NCMM General Lab Coordinator, Visiting Researcher, Oddmund Bakke group, IBV)
It is a great challenge to study the rapid dynamics of intracellular membrane trafficking events in live cells. Multiple intracellular membrane trafficking pathways co-exist and interlace with each other in close proximation in time and space. On top of that, many vesicles undergo fusion and fission events and change in size, shape and even identity as they move more or less rapidly in the cytoplasm along cytoskeletal paths driven by molecular motors. All these events make tracking and analysing their behaviour using modern microscopy technology very challenging. Here we present a new imaging and tracking method tailored for intracellular trafficking vesicle tracking and how we use this method to study the coating protein dynamics during the endosome maturation process. Live cell image series obtained by the super-resolution microscopy techniques (Airyscan and Live-SR) of maturing endosomes are tracked by our new ImageJ based seed-growing polygon detection algorithm. The intensities of coat proteins labelled with either the green fluorophore (GFP) or the red fluorophore (RFP/mCherry/mApple) are automatically recorded and analysed. The method was first tested with the well-studied Rab5 and Rab7 switch during endosome maturation and then applied to study the dynamics of other proteins that have been reported to interact with either Rab5 or Rab7 (EEA1, Rab9, Rab 4, Rab8,etc) during the Rab switch phase of the endosome maturation process. We found that some of the proteins are merely visiting the endosomes during the process(e.g. Rab11); but the presence of several others are in phase with the Rab switch(e.g. Rab4, Rab8 and Rab9), indicating that they may play a role in regulating the endosome maturation process.