H3K27 ChIP-sequencing of NNMT overexpression in normal fibroblasts

High grade serous carcinoma (HGSC) arising from either the fallopian tube or ovary has a poor prognosis primarily due to its early dissemination throughout the abdominal cavity. Genomic and proteomic approaches have provided snapshots of the proteogenomics of ovarian cancer (OvCa)1,2, but a systematic examination of both the tumor and stromal compartments is critical to understanding OvCa metastasis. We developed a label-free proteomic workflow to analyze as few as 5,000 formalin-fixed, paraffin embedded cells microdissected from each compartment. The tumor proteome was comparatively stable during progression from in situ lesions to metastatic disease; however, the metastasis-associated stroma was characterized by a highly conserved proteomic signature, prominently including the methyltransferase nicotinamide N-methyltransferase (NNMT) and the proteins it regulates. Stromal NNMT expression was necessary and sufficient for several functional aspects of the cancer associated fibroblast (CAF) phenotype, including the expression of CAF markers and the secretion of cytokines and oncogenic extracellular matrix. Stromal NNMT supported OvCa migration, proliferation, and in vivo growth and metastasis. Expression of NNMT in CAFs led to a depletion of S-adenosyl methionine (SAM) and a reduction in histone methylation associated with extensive gene expression changes in the tumor stroma. This work supports the use of ultra-low input proteomics to identify candidate drivers of disease phenotypes and reveals that NNMT is a central, metabolic regulator of CAF differentiation and cancer progression in the stroma and a novel treatment target. Three biological replicates of normal murine 3T3 fibroblasts expressing either control or NNMT overexpression construct were grown for 48 hours in physiological levels of methionine before chromatin was extracted and subjected to H3K27me3 chromatin immunoprecipitation sequencing. Input controls for both control and NNMT overexpressing cells were also included.