siRNA-based Gold Nanoparticles as a Therapeutic Enhancer for Triple Negative Breast Cancer (TNBC) Radiotherapy

ABSTRACT Radiation therapy (RT) modulates immunological properties of tumor microenvironment (TME) to stimulate antitumor immune response. However, RT initiates immunosuppressive mechanisms as well and therefore diminishing the effects of RT immuno-stimulation. One of the main RT immunosuppressive modes is exerted by

an increase in TGF production that in breast cancers (BC) has an additive effect on already high TGF levels produced by cancer cells themselves. Triple negative breast cancer (TNBC) in particular, was demonstrated to have higher TGF levels compared to other BCs, and this finding correlated with increased tumor grade and

invasiveness, and a diminished patient survival. Consequently, RT induced increase in TGF within the TME may further potentiate invasiveness and metastatic potential of TNBC. Due to stimulatory aspects of RT immunomodulation, RT has gained interest as a prospective therapeutic enhancer in cancer immunotherapy,

such as immune checkpoint blockers, that has shown great potential in improving local control and overall survival in select cancers. Unfortunately, in most forms of BC, including TNBC, response to immunotherapy remains modest. Our long-term goal is to use RT to enhance TNBC response to immunotherapy by taking

advantage of RT immunomodulatory potential. Antitumor RT effects, including TME immunomodulation can be improved by using radiosensitizers, such as gold nanoparticles (AuNP). Furthermore, AuNPs can also serve as a drug delivery system by conjugation of small interfering RNAs (siRNAs). In this project we propose to use

AuNPs functionally modified by TGF siRNA to simultaneously enhance RT immunomodulation and counteract the immunosuppressive effects related to the increased TGF production. This approach will enhance RT antitumor effects and create a favorable TME environment for better response to future immunotherapies. This

will be tested by the following specific aims: Aim 1: To synthesize and characterize AuNP-siRNATGF1; Aim 2: To investigate the therapeutic effect of combination of RT and AuNP-siRNATGFβ1 in in vitro and in vivo mouse TNBC model. The proposed studies in determining the potential of AuNPs simultaneously target

antitumor and immunomodulatory RT effects will provide critical information for improving TNBC response to immune checkpoint blockers and for designing future RT/ immune checkpoint blockers multimodal TNBC therapies.