Nectin-4-targeted immunoSPECT/CT imaging and photothermal therapy of triple-negative breast cancer

Abstract

Background: Triple-negative breast cancer (TNBC) is more prone to distant metastasis and visceral recurrence in comparison to other breast cancer subtypes, and is related to dismal prognosis. Nevertheless, TNBC has an undesirable response to targeted therapies. Therefore, to tackle the huge challenges in the diagnosis and treatment of TNBC, Nectin-4 was selected as a theranostic target because it was recently found to be highly expressed in TNBC. We developed anti-Nectin-4 monoclonal antibody (mAb_Nectin-4)-based theranostic pair, ^99mTc-HYNIC-mAb_Nectin-4 and mAb_Nectin-4-ICG. ^99mTc-HYNIC-mAb_Nectin-4 was applied to conduct immuno-single photon emission computed tomography (SPECT) for TNBC diagnosis and classification, and mAb_Nectin-4-ICG to mediate photothermal therapy (PTT) for relieving TNBC tumor growth.

Methods: Nectin-4 expression levels of breast cancer cells (MDA-MB-468: TNBC cells; and MCF-7, non-TNBC cells) were proved by western blot, flow cytometry, and immunofluorescence imagning. Cell uptake assays, SPECT imaging, and biodistribution were performed to evaluate Nectin-4 targeting of ^99mTc-HYNIC-mAb_Nectin-4. A photothermal agent (PTA) mAb_Nectin-4-ICG was generated and characterized. In vitro photothermal therapy (PTT) mediated by mAb_Nectin-4-ICG was conducted under an 808 nm laser. Fluorescence (FL) imaging was performed for mAb_Nectin-4-ICG mapping in vivo. In vivo PTT treatment effects on TNBC tumors and corresponding systematic toxicity were evaluated.

Results: Nectin-4 is overexpressed in MDA-MB-468 TNBC cells, which could specifically uptake ^99mTc-HYNIC-mAb_Nectin-4 with high targeting in vitro. The corresponding immunoSPECT imaging demonstrated exceptional performance in TNBC diagnosis and molecular classification. mAb_Nectin-4-ICG exhibited favourable biocompatibility, photothermal effects, and Nectin-4 targeting. FL imaging mapped biodistribution of mAb_Nectin-4-ICG with excellent tumor-targeting and retention in vivo. Moreover, mAb_Nectin-4-ICG-mediated PTT provided advanced TNBC tumor destruction efficiency with low systematic toxicity.

Conclusion: mAb_Nectin-4-based radioimmunoimaging provides visualization tools for the stratification and diagnosis for TNBC, and the corresponding mAb_Nectin-4-mediated PTT shows a powerful anti-tumor effect. Our findings demonstrate that this Nectin-4 targeting strategy offers a simple theranostic platform for TNBC.

Keywords: Indocyanine green; Nectin-4; Photothermal therapy; Single photon emission computed tomography; Triple-negative breast cancer.