Influencing the Tumor Microenvironment: A Phase II Study of Copper Depletion Using Tetrathiomolybdate in Patients with Breast Cancer at High Risk for Recurrence and in Preclinical Models of Lung Metastases

Abstract

Purpose: Bone marrow-derived progenitor cells, including VEGFR2þ endothelial progenitor cells (EPCs) and copper-dependent pathways, model the tumor microenvironment. We hypothesized that copper depletion using tetrathiomolybdate would reduce EPCs in high risk for patients with breast cancer who have relapsed. We investigated the effect of tetrathiomolybdate on the tumor microenvironment in preclinical models. Experimental Design: Patients with stage II triple-negative breast cancer (TNBC), stage III and stage IV without any evidence of disease (NED), received oral tetrathiomolybdate to maintain ceruloplasmin (Cp) between 8 and 17 mg/dL for 2 years or until relapse. Endpoints were effect on EPCs and other biomarkers, safety, event-free (EFS), and overall survival (OS). For laboratory studies, MDA-LM2-luciferase cells were implanted into CB17-SCID mice and treated with tetrathiomolybdate or water. Tumor progression was quantified by bioluminescence imaging (BLI), copper depletion status by Cp oxidase levels, lysyl oxidase (LOX) activity by ELISA, and collagen deposition.Results: Seventy-five patients enrolled; 51 patients completed 2 years (1,396 cycles). Most common grade 3/4 toxicity was neutropenia (3.7%). Lower Cp levels correlated with reduced EPCs (P ¼ 0.002) and LOXL-2 (P < 0.001). Two-year EFS for patients with stage II-III and stage IV NED was 91% and 67%, respectively. For patients with TNBC, EFS was 90% (adjuvant patients) and 50% (stage IV NED patients) at a median follow-up of 6.3 years, respectively. In preclinical models, tetrathiomolybdate decreased metastases to lungs (P ¼ 0.04), LOX activity (P ¼ 0.03), and collagen crosslinking (P ¼ 0.012).Conclusions: Tetrathiomolybdate is safe, well tolerated, and affects copper-dependent components of the tumor microenvironment. Biomarker-driven clinical trials in high risk for patients with recurrent breast cancer are warranted.

ATP7A delivers copper to the lysyl oxidase family of enzymes and promotes tumorigenesis and metastasis

“…Copper chelation therapy is an experimental approach that has been shown to significantly extend the life expectancy of patients diagnosed with stage III and stage IV breast cancer (14), raising the possibility that inhibition of copper delivery to specific oncogenic metalloenzymes might offer therapeutic benefits. Prometastatic metalloenzymes that are affected by copper chelation therapy include the LOX family of enzymes, which have well-documented roles in tumor malignancy (6).…”

“…This idea has been supported by reports that copper chelation reduces tumor growth and malignancy in animal models of cancer (12,13). Clinical studies indicate that copper chelation prolongs the survival of patients with late-stage breast cancer (14) and kidney cancer (15). These studies raise the possibility that blocking specific steps in the delivery of copper to oncogenic metalloenzymes may provide an approach to treating cancer.…”

Copper signaling in the brain and beyond

“…Cu(gtsm) (75)), takes advantage of the oxidizing environment in cancer cells, which is less equipped to buffer increases in copper, to cause cell death (76). Additionally, systemic chelation of copper with TTM has shown positive results in phase II clinical trials for the prevention triple-negative breast cancer (TNBC) metastasis, a lethal step in TNBC progression (77,78).…”

From transformation to metastasis: deconstructing the extracellular matrix in breast cancer

“…The allosteric LOXL2 inhibitor diminishes desmoplastic response and prevents tumor cell metastasis in numerous cancer models [116]. Novel approaches of depleting copper with tetrathiomolybdate in phase I and phase II clinical trials decrease lung metastasis, LOX activity, and collagen cross-linking in high-risk breast cancer patients [117]. These approaches have yet to be investigated in clinical trials but offer novel approaches with significant potential for clinical application.…”