Project Grant F31CA317530

THE ROLE OF THE INTERFERON-ALPHA RESPONSE IN ARA-C RESISTANT MYELOID LEUKEMIA ASSOCIATED WITH DOWN SYNDROME - PROJECT SUMMARY ALTHOUGH MOST PATIENTS WITH MYELOID LEUKEMIA ASSOCIATED WITH DOWN SYNDROME (ML-DS) ARE CURED WITH CYTARABINE (ARA-C)-BASED CHEMOTHERAPY, RELAPSED/REFRACTORY CASES HAVE EXTREMELY POOR CLINICAL OUTCOMES WITH NO CLINICAL BIOMARKERS OR SALVAGE THERAPIES IN PLACE. THESE CLINICAL FINDINGS HIGHLIGHT THE URGENT NEED FOR A BETTER UNDERSTANDING OF ARA-C-RESISTANCE MECHANISMS IN ML-DS AND THE DEVELOPMENT OF EFFECTIVE THERAPIES FOR THIS VULNERABLE GROUP OF PATIENTS. OUR LAB HAS IDENTIFIED STERILE ALPHA MOTIF AND HD-DOMAIN CONTAINING PROTEIN 1 (SAMHD1), A DEOXYNUCLEOTIDE TRIPHOSPHATE (DNTP) HYDROLASE, AS A MAJOR DRIVER OF ARA-C INACTIVATION IN ML-DS BY CONVERTING ARA-CTP, THE ACTIVE ARA-C METABOLITE, BACK INTO ITS PRODRUG FORM (ARA-C). IMMUNOBLOT ANALYSIS DEMONSTRATES THAT SAMHD1 IS SUBSTANTIALLY UPREGULATED IN ARA-C-RESISTANT ML-DS CELLS (CMY) COMPARED TO ARA-C-SENSITIVE ML-DS CELLS (CMK). GENETIC KNOCKDOWN OF SAMHD1 IN CMY CELLS SHOWS A STRONG CONCENTRATION-DEPENDENT RESENSITIZATION TO ARA-C WITH A CONSISTENT INCREASE OF ARA-CTP, DEMONSTRATING SAMHD1 TO BE A PROMISING THERAPEUTIC TARGET, YET THERE IS LITTLE KNOWN ABOUT THE MECHANISM OF SAMHD1 UPREGULATION. OUR PREVIOUS PROTEOMIC AND PATHWAY ENRICHMENT ANALYSES IDENTIFIED THE INTERFERON ALPHA (IFN-A) RESPONSE AS THE MOST SIGNIFICANTLY ENRICHED PATHWAY IN ARA-C-RESISTANT ML-DS CELLS COMPARED TO ARA-C-SENSITIVE COUNTERPARTS. WE ALSO OBSERVED STRONG UPREGULATION OF IFN-RELATED DNA DAMAGE RESISTANT SIGNATURE (IRDS) GENES IN ARA-C-RESISTANT ML-DS CELLS. IRDS GENES ARE CANONICALLY ENRICHED IN CHEMOTHERAPY-, IMMUNOTHERAPY-, OR RADIOTHERAPY-RESISTANT CANCERS AND ARE TRANSCRIBED BECAUSE OF CHRONIC IFN-A STIMULATION. MY PRELIMINARY DATA SHOW THAT ARA-C-SENSITIVE CMK CELLS DISPLAY AN INDUCIBLE TYPE I IFN RESPONSE WHICH ELEVATES SAMHD1 AND INCREASES RESISTANCE TO ARA-C. IFN SIGNALING IS THOUGHT TO CONFER RESISTANCE THROUGH TRANSCRIPTIONAL REPROGRAMMING AND PERSISTENT ACTIVATION OF INTERFERON-STIMULATED GENES (ISGS). HOWEVER, THE EXACT CONSEQUENCES OF THIS MODULATED SIGNALING PATHWAY IN ML-DS REMAIN TO BE DISCOVERED. I HYPOTHESIZE THAT ABERRANT IFN-A/JAK/STAT SIGNALING SUSTAINS ELEVATED EXPRESSION OF IRDS GENES AND SAMHD1 AND BY DIRECTLY INHIBITING THE IFN-A/JAK/STAT PATHWAY, ARA-C EFFICACY CAN BE RESTORED IN RELAPSED ML-DS PATIENTS. THIS PROJECT WILL DEFINE A PREVIOUSLY UNRECOGNIZED MECHANISM OF ARA-C RESISTANCE IN ML-DS DRIVEN BY CHRONIC IFN-A SIGNALING AND SUSTAINED SAMHD1 EXPRESSION. BY RECEIVING TRAINING FROM EXPERTS IN OMICS-BASED STUDIES, INF SIGNALING AND CLINICAL RESEARCH, I WILL GAIN A COMPREHENSIVE SCIENTIFIC UNDERSTANDING, LEARN NEW RESEARCH TECHNIQUES, AND BUILD PROFESSIONAL NETWORKING SKILLS. I WILL ALSO COLLABORATE WITH MY CO-SPONSOR, DR. JEFFREY TAUB, TO UNDERSTAND THE CLINICAL NEEDS AND CHALLENGES OF THIS PATIENT POPULATION. BY UNCOVERING THE BIOLOGY UNDERLYING RESISTANCE-ASSOCIATED GENE REGULATION, THIS WORK WILL LAY THE FOUNDATION FOR FUTURE THERAPEUTIC STRATEGIES FOR PATIENTS WITH RELAPSED ML-DS.