ENPP1 Inhibition as a Therapeutic Target in Osteosarcoma
Thomas A. Rodriguez
Department of Biology
Faculty Supervisor: Cathy Samayoa
Background: Osteosarcoma (OS) genome is characterized by high chromosomal instability (CIN). CIN is a hallmark in human cancers, associated with metastasis, immune evasion, and therapeutic resistance. CIN leads to Micronuclei formation and cytosolic dsDNA, resulting in activation of the cGAS-STING pathway. Given high levels of CIN, it is not surprising that this anti-tumoral axis is paradoxically co-opted to provide immune evasion rather than immune surveillance. CINhigh-tumors induce the expression of ENPP1 to hydrolyze cGAMP, which dampens the downstream effects of STING signaling.
Results: Pan-RNAseq revealed ENPP1 expression was high in OS. ENPP1 OE increased tumor growth kinetics and spontaneous lung metastasis after orthotopic inoculation. Mechanistically, pathway analysis revealed downregulation in KRAS signaling after inhibition of ENPP1 (ENPP1i, AVA-NP-695). Connectivity map unveiled MEKi recapitulate the signature of ENPP1i. WB showed an increase in replication stress markers in a dose-response manner after treatment with ENPP1i or MEKi. We also observed a downregulation in DNA repair proteins (BRCA1/2 and RAD51) which could be therapeutically exploited. This stress was leveraged with PARPi, which synergized with ENPP1i in a targeted-pharmacological screen. This novel vulnerability was validated in NSG mice by observing tumor regression upon ENPP1i-PARPi and MEKi-PARPi combination therapies in OS-PDX tumors.