Targeting DUSP1 overcomes resistance to ¹⁷⁷Lu-DOTATATE in neuroendocrine tumors

Background: Neuroendocrine tumors (NETs) often present as metastatic or unresectable disease, and while ¹⁷⁷Lu-DOTATATE PRRT benefits SSTR2-positive patients, its modest response rate highlights the need for improved combinations. DUSP1, a MAPK phosphatase regulating JNK/p38, is elevated in multiple cancers, yet its role in NETs is unknown. Given the contribution of MAPK signaling to therapy resistance, we hypothesized that DUSP1 inhibition enhances NET sensitivity to ¹⁷⁷Lu-DOTATATE. Materials and Methods: We compared DUSP1 mRNA levels in primary versus metastatic NETs using public transcriptomic datasets and assessed DUSP1 protein across NET cell lines and two PDX models by Western blot. Functional studies with the DUSP1 inhibitor BCI measured viability, clonogenic survival, apoptosis, mitochondrial depolarization, ROS and MAPK activation, with RNA-seq defining transcriptional changes. Rescue experiments used CC90001, ISRIB, NAC, DUSP1 overexpression, and the JNK1-K55R mutant. Synergy with PRRT was evaluated by combining BCI with sub-lethal ¹⁷⁷Lu-DOTATATE. Results: Transcriptomic profiling showed elevated DUSP1 in lymph-node metastases versus primary NETs, and DUSP1 protein was highly expressed across NET cell lines and PDX models. BCI (1-2.5 μM) markedly reduced viability and clonogenic survival (~80% at 1 μM) and induced apoptosis (cleaved PARP ~6-fold, caspase-3/7 ~4-fold, ΔΨm loss ~2-fold). RNA-seq and Western blotting confirmed strong activation of pro-apoptotic JNK1/2 and p38. JNK inhibition, the JNK1-K55R mutant, and DUSP1 overexpression each rescued cells, whereas DUSP1 knockdown induced apoptosis-establishing DUSP1 as a key NET survival factor. RNA-seq also revealed ER-stress activation (XBP1s, ATF4, CHOP). ISRIB blocked ER stress and rescued cells, while NAC suppressed ROS, prevented MAPK/ER-stress activation, and fully rescued cells, indicating that DUSP1 inhibition triggers a ROS-dependent cascade converging on JNK and ER-stress pathways. Combining BCI with ¹⁷⁷Lu-DOTATATE produced strong synergy (CI < 0.5) with enhanced apoptosis. JNK inhibition and ISRIB each rescued combination-induced apoptosis (~60% and ~40%), showing that both pathways are required for PRRT sensitization. Conclusion: DUSP1 is an actionable therapeutic vulnerability in NETs. Its inhibition induces ROS-driven activation of pro-apoptotic MAPK and ER-stress pathways, potentiating ¹⁷⁷Lu-DOTATATE. These findings provide preclinical support for DUSP1-targeted combination strategies, with ongoing in vivo studies needed to advance this approach toward clinical translation.