Inter-organellar communication in metabolic reprogramming of colorectal cancer

PROJECT SUMMARY Colorectal cancers (CRC) are characterized as having a hierarchical organization requiring proliferating and de-differentiated stem cells to maintain tumor growth and progression. Cellular plasticity underlying colorectal cancer is essential for a process which occurs following selective pressures of the tumor microenvironment and chemotherapeutics. The colonic tumor microenvironment is characterized by extreme hypoxia due to the anoxic lumen. Hypoxia promotes metabolic rewiring, and such processes are utilized by cancer cells to support biosynthesis, cell survival and dynamic alteration in cell fates. A critical feature of cellular metabolism is organellar interaction and coordination, yet how these contribute to CRC plasticity, survival, progression and treatment response are unclear. Endoplasmic reticulum-mitochondria contact sites (ERMCS) are the most abundant inter-organellar interaction. I generated a panel of ERMCS reporter CRC cell lines, and through unbiased high content imaging and CRISPR screens, I have identified essential mechanisms required for ER- mitochondrial interactions in CRC. Moreover, I show a key role of tumor hypoxia in modulating ERMCS. Hypoxia inhibited mitochondrial complex III and IV to decrease ERMCS. Treating cells with the mitochondrial electron carrier, coenzyme (CoQ) rescued ERMCS suppression following hypoxia. I hypothesize that tumor hypoxia regulates ER-mitochondrial contacts (ERMCS) by altering mitochondrial respiration and CoQ redox for metabolic adaptation and survival. In aim 1 (F99 phase), I will focus on identifying the molecular mechanism of hypoxia dependent ERMCS inhibition and expand into in vivo models with our novel ERMCS reporter mouse model. During the K00 phase, I will apply knowledge gained during graduate school in cancer metabolism and organellar interaction to an independent postdoctoral project. The plasticity of colorectal tumor epithelium depends on integration of organellar functions to sustain metabolic demands. Therefore, my goal as a postdoctoral fellow is to understand the dynamic changes and requirement for organellar interactions and metabolic compartmentalization during cell fates alterations in CRC. I plan to use genetic murine and primary patient organoid models of CRC, volumetric electron microscopy, in vivo organellar metabolomics, and functional CRISPR screens to answer these questions. Lastly, in addition to the proposed studies, this training plan includes activities important for career development, mentorship, networking, and scientific communication to prepare me for successful transition to a postdoctoral fellowship and my career as an independent investigator studying cancer metabolism.