# ENPP3 drives ccRCC progression by cGAMP hydrolysis and STING–IFN suppression

## TL;DR

ENPP3 promotes kidney cancer growth by blocking immune signals, and targeting it could boost cancer treatments.

## Contribution

ENPP3 is identified as a hypoxia-driven immune checkpoint enzyme in ccRCC that suppresses anti-tumor immunity via cGAMP hydrolysis.

## Key findings

- ENPP3 is upregulated in ccRCC and linked to poor prognosis.
- ENPP3 inhibition or blockade enhances anti-tumor immunity and synergizes with anti-PD-L1.
- ENPP3 depletion increases extracellular cGAMP and activates STING-IFN signaling in macrophages.

## Abstract

Clear-cell renal cell carcinoma (ccRCC) is an immune-desert tumor. This study investigates the role of ectonucleotide pyrophosphatase/phosphodiesterase 3 (ENPP3) as a potential therapeutic target and immune-checkpoint enzyme in ccRCC.

ENPP3 expression and its link to hypoxia and prognosis were analyzed in ccRCC. Functional roles were tested using gain/loss-of-function studies in vitro and in xenograft models, followed by therapeutic anti-ENPP3 antibody administration, alone or with anti-PD-L1. Mechanisms were explored via promoter analysis, cGAMP measurement, flow cytometry, cytokine profiling, and in vivo neutralization with STING- or interferon-α/β receptor-1 (IFNAR1) blocking antibodies.

ENPP3 is hypoxia-inducible via HIF-1α, upregulated in ccRCC, and predicts poor prognosis. ENPP3 overexpression accelerated tumor growth, while its knockdown or antibody blockade inhibited progression and synergized with anti-PD-L1. Mechanistically, ENPP3 hydrolyzes extracellular cGAMP. Its depletion elevated extracellular cGAMP, expanded anti-tumor immune cells (M1 macrophages, cDC1s, and cytotoxic T cells), reduced Tregs, and induced a STING- and IFNAR1-dependent type I interferon signature in macrophages. The anti-tumor efficacy of ENPP3 blockade was abrogated by IFNAR1 inhibition.

ENPP3 is a hypoxia-driven, cGAMP-targeting innate immune checkpoint in ccRCC. Its inhibition reactivates STING-dependent anti-tumor immunity, providing a strong preclinical rationale for targeting ENPP3 therapeutically.