Profiling proteomic responses in small intestinal neuroendocrine tumor GOT1 after [¹⁷⁷Lu]Lu-DOTATATE therapy

Peptide receptor radionuclide therapy with [¹⁷⁷Lu]Lu-DOTATATE is an established treatment for somatostatin receptor-expressing neuroendocrine tumors. Although strong anti-tumor effects have been demonstrated in experimental models, curative responses in patients remain limited. Improved understanding of the molecular responses induced by [¹⁷⁷Lu]Lu-DOTATATE may help identify strategies for treatment optimization. This study aimed to characterize proteomic alterations in GOT1 small intestinal neuroendocrine tumor xenografts following [¹⁷⁷Lu]Lu-DOTATATE therapy.

GOT1 tumor-bearing BALB/c nude mice received a non-curative intravenous administration of 15 MBq [¹⁷⁷Lu]Lu-DOTATATE or saline control. Tumors were collected 1 or 13 days after treatment to represent early response and regrowth phases. Tumor volumes were monitored using magnetic resonance imaging. Proteomic profiling was performed using liquid chromatography tandem mass spectrometry with tandem mass tag labeling. Differential protein expression was analyzed using Welch's t-test with significance defined as fold change ≥ 1.5 and p < 0.01. Functional enrichment and pathway analyses were conducted using Gene Ontology annotation and Ingenuity Pathway Analysis.

Treatment induced a transient reduction in tumor volume followed by regrowth. In total, 3861 proteins were quantified, of which 155 showed significantly altered expression after treatment. Affected proteins were associated with cytoskeletal organization, oxidative stress response, protein metabolism, and systemic regulation. Pathway analyses identified inhibition of several signaling pathways linked to cell migration and invasiveness, including RhoA, Rac, integrin, and CXCR4 signaling. Upstream regulator analysis suggested activation of RABL6 and inhibition of p53 signaling during tumor regrowth. Proteins related to endoplasmic reticulum stress and ubiquitin-proteasome activity were also altered. Selected findings were validated by ELISA.

[¹⁷⁷Lu]Lu-DOTATATE therapy induced extensive proteomic changes in GOT1 tumors, including suppression of pathways associated with invasiveness and modulation of p53- and stress-related signaling. These findings suggest potential therapeutic benefits of combining [¹⁷⁷Lu]Lu-DOTATATE with agents targeting p53 regulation or endoplasmic reticulum stress pathways to improve treatment efficacy in neuroendocrine tumors.