Immunotherapy of triple-negative breast cancer with cathepsin D-targeting antibodies

Abstract

BackgroundTriple-negative breast cancer (TNBC) treatment is currently restricted to chemotherapy. Hence, tumor-specific molecular targets and/or alternative therapeutic strategies for TNBC are urgently needed. Immunotherapy is emerging as an exciting treatment option for TNBC patients. The aspartic protease cathepsin D (cath-D), a marker of poor prognosis in breast cancer (BC), is overproduced and hypersecreted by human BC cells. This study explores whether cath-D is a tumor cell-associated extracellular biomarker and a potent target for antibody-based therapy in TNBC.MethodsCath-D prognostic value and localization was evaluated by transcriptomics, proteomics and immunohistochemistry in TNBC. First-in-class anti-cath-D human scFv fragments binding to both human and mouse cath-D were generated using phage display and cloned in the human IgG1 λ format (F1 and E2). Anti-cath-D antibody biodistribution, antitumor efficacy and in vivo underlying mechanisms were investigated in TNBC MDA-MB-231 tumor xenografts in nude mice. Antitumor effect was further assessed in TNBC patient-derived xenografts (PDXs).ResultsHigh CTSD mRNA levels correlated with shorter recurrence-free survival in TNBC, and extracellular cath-D was detected in the tumor microenvironment, but not in matched normal breast stroma. Anti-cath-D F1 and E2 antibodies accumulated in TNBC MDA-MB-231 tumor xenografts, inhibited tumor growth and improved mice survival without apparent toxicity. The Fc function of F1, the best antibody candidate, was essential for maximal tumor inhibition in the MDA-MB-231 model. Mechanistically, F1 antitumor response was triggered through natural killer cell activation via IL-15 upregulation, associated with granzyme B and perforin production, and the release of antitumor IFNγ cytokine. The F1 antibody also prevented the tumor recruitment of immunosuppressive tumor-associated macrophages M2 and myeloid-derived suppressor cells, a specific effect associated with a less immunosuppressive tumor microenvironment highlighted by TGFβ decrease. Finally, the antibody F1 inhibited tumor growth of two TNBC PDXs, isolated from patients resistant or not to neo-adjuvant chemotherapy.ConclusionCath-D is a tumor-specific extracellular target in TNBC suitable for antibody-based therapy. Immunomodulatory antibody-based strategy against cath-D is a promising immunotherapy to treat patients with TNBC.Electronic supplementary materialThe online version of this article (10.1186/s40425-019-0498-z) contains supplementary material, which is available to authorized users.

Inhibition of Cathepsin D (CTSD) enhances radiosensitivity of glioblastoma cells by attenuating autophagy

“…25 High CTSD messenger RNA levels correlated with shorter recurrence-free survival in triple-negative breast cancer, and high concentration of extracellular CTSD was detected in the tumor microenvironment. 26 Also, Zhang et al 27 found a critical CTSD-hepsin signaling axis in migration and metastasis of breast cancer. Thus far, however, studies on the role of CTSD in radiosensitivity of glioma cells are still lacking.…”

A 9-kDa matricellular SPARC fragment released by cathepsin D exhibits pro-tumor activity in the triple-negative breast cancer microenvironment

“…Here, we found that in the acidic tumor microenvironment of TNBC, cath-D cleaved SPARC exclusively in its C-terminal extracellular Ca 2+ binding domain releasing five main fragments (34-, 27-, 16-, 9-, and 6-kDa). Among these fragments, the 9-kDa C-terminal SPARC fragment (amino acids 235-303) had greater oncogenic activity than FL SPARC, highlighting the importance of limited proteolysis of matricellular proteins in the TNBC microenvironment.…”

“…However, little is known about the molecular mechanisms and the substrates involved in these processes. Our recent study indicated that cath-D is a tumor-specific extracellular target in TNBC and its suitability for antibody-based therapy (16).Thus, the identification of the cath-D extracellular substrate repertoire by N-Terminal Amine Isotopic Labeling of Substrates (N-TAILS) degradomics (17) is important for the mechanistic understanding of its role in TNBC.…”

Advances in Anti-Cancer Immunotherapy: Car-T Cell, Checkpoint Inhibitors, Dendritic Cell Vaccines, and Oncolytic Viruses, and Emerging Cellular and Molecular Targets

“…Therefore, targeting extracellular CathD immunotherapeutically may reduce tumour growth and subsequent metastasis. To address this, Ashraf et al recently demonstrated an anti-tumour efficacy for anti-CathD antibody in triple-negative breast cancer (TNBC) mice models [220]. The two human anti-CathD Abs used in this study efficiently bound to human and mouse CathD resulted in a significant inhibition of tumour growth in three different TNBC mouse models (MDA-MB-231 cell xenografts and two TNBC patient-derived xenografts) [220].…”

“…To address this, Ashraf et al recently demonstrated an anti-tumour efficacy for anti-CathD antibody in triple-negative breast cancer (TNBC) mice models [220]. The two human anti-CathD Abs used in this study efficiently bound to human and mouse CathD resulted in a significant inhibition of tumour growth in three different TNBC mouse models (MDA-MB-231 cell xenografts and two TNBC patient-derived xenografts) [220]. Furthermore, the recruitment of the immune-suppressing tumour-associated macrophages (TAMs) and myeloid-derived suppressor cells within the TME were effectively blocked.…”