Identification and targeting of pathways separating healthy stem cell aging from malignant transformation

ABSTRACT Myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) are generally incurable hematologic malignancies, originating from aberrant hematopoietic stem and multipotent progenitor cells (HSPC). These diseases occur mainly in the elderly and are preceded by an often-unrecognized precancerous phase, which can last for years and is hallmarked by a progressively changing HSPC compartment. These molecularly and functionally diverging stem cells, harbor a higher propensity to undergo malignant transformation. Mechanisms that separate the healthy aging process from cancer evolution are incompletely resolved. This gap in our knowledge poses a significant challenge for the development of curative therapies for myeloid malignancies for which overall cure rates have remained below 30% over the last decades. Our study will investigate the role of chaperone-mediated autophagy (CMA), a highly selective subtype of autophagy, which we recently demonstrated to confer key roles in stress mitigation in and metabolic control of HSPC. Contrary to macroautophagy, CMA specifically degrades proteins containing defined recognition motifs (“KFERQ”, and variants), and maintains integrity and proper function of many cell types during chronic stress and aging. CMA declines in and critically contributes to several age-associated pathologies, yet its role in leukemogenesis and cancer stem cell evolution is unknown. Using new genetic mouse models, we have obtained exciting preliminary data strongly suggesting that loss of CMA drives expansion of HSPC bearing gene lesions found in clonal hematopoiesis of indeterminate potential (CHIP); yet upon malignant transformation, CMA is critically needed in and likely selected for in LSC. For this study, we hypothesize that CMA enables LSC maintenance through governing metabolic adaptation to amino acid starvation, licensing increase of fatty acid production through upregulation of coenzyme A synthesis from lysosomal cysteine. We will utilize a complementary model set consisting of genetic mouse models, human cell lines and primary patient-derived cells for the study of (i) CMA activation patterns in CHIP-HSPC and LSC (leveraging a CMA reporter mouse and lentiviral CMA biosensors for primary human cells), (ii) molecular and (iii) functional consequences of CMA inactivation and stimulation. Our study will provide new insights into a molecular mechanism declining during aging and predisposing adult tissue-specific stem cells to malignant transformation, which will have important implications for the development of new therapeutic strategies for targeting autophagy in myeloid malignancies, and possibly other stem cell- derived cancers.