Therapeutic Silencing of BCL-2 Using NK Cell-Derived Exosomes as a Novel Therapeutic Approach in Breast Cancer

Abstract

Overexpression of the anti-apoptotic protein BCL-2 is frequently observed in multiple malignancies, including about 85% of patients with estrogen receptor positive (ER+) breast cancer. Besides being studied as a prognostic marker, BCL-2 is investigated as a therapeutic target in ER+ breast cancer. Here, we introduce a new exosome-based strategy to target BCL-2 using genetically modified natural killer (NK) cells. The NK cell line NK92MI was lentivirally transduced to express and load BCL-2 siRNAs (siBCL-2) into exosomes (NKExos) and then evaluated for its potential to treat ER+ breast cancer. Transfected NK92MI cells produced substantial levels of BCL-2 siRNAs, without substantially affecting NK cell viability or effector function and led to loading of siBCL-2 in NKExos. Remarkably, targeting BCL-2 via siBCL-2 NKExos led to enhanced intrinsic apoptosis in breast cancer cells, without affecting non-malignant cells. Together, our prototypical results for BCL-2 in breast cancer provide proof of concept for a novel strategy to utilize NKExos as a natural delivery vector for siRNA targeting of oncogenes.

Recent advances in exosome-mediated nucleic acid delivery for cancer therapy

“…siRNA exosomal therapy targeting tumor cells has been been committed to downregulating these oncogenes expression to inhibit cell proliferation and migration. Kaban et al [ 141 ] loaded BCL-2 siRNA into natural killer (NK) cell-derived exosomes to treat ER + breast cancer, leading to enhanced apoptosis in breast cancer cells. Similarly, exosomes mediated the delivery of PLK-1 siRNA into bladder cancer cells, promoting cell apoptosis through silencing PLK-1 expression [ 142 ].…”

Immune-regulating camouflaged nanoplatforms: A promising strategy to improve cancer nano-immunotherapy

“…Anti-apoptotic protein BCL-2 consistently overexpressed in the patients with estrogen receptor-positive (ER + ) breast cancer, which was deemed as an estrogen-responsive gene facilitating cancer cell growth by allowing programmed-cell-death evasion of breast cancer cells. In this study, NKExos acted as suitable vectors to deliver siRNA targeting BCL-2 into tumor sites with high efficiency and amplified the eradication of cancer cells by enhancing the immune response [ 119 ]. Lastly, T cell-derived exosomes carrying TCR/CD3 complex from parental activated T cells can present antitumor responses.…”

“… Enhancing immune response/tumor targeting Immunotherapy siBCL-2 NKExos demonstrated specific targeting of BCL-2 and significant antitumor efficacy against ER + breast cancer. [ 119 ] Human hyaluronidase (PH20) was expressed on the surface of exosomes derived from 293T cells using genetic engineering and modifying the exosomes with FA by self-assembly techniques (Exos-PH20-FA) Inducing immune response/tumor targeting Immunotherapy Exos-PH20-FA modulated the TME via polarized macrophages to the M1 phenotype and reduced the number of relevant immunosuppressive immunocytes. [ 122 ] Anti-human CD3 and anti-human HER2 antibodies were displayed on the surface of exosomes derived from Expi293 cells (SMART-Exos).…”

Emerging innovations on exosome-based onco-therapeutics

“…NK cells recognize tumor antigens primarily via surface-activated receptors and secrete cytotoxic molecules such as perforin and granzyme to lyse malignant cells ( 37 ). Similarly, NK cell-derived exosomes can kill cancer cells by providing FasL and perforin/granzyme, with the efficacy demonstrated in various tumors such as breast cancer ( 38 ) and neuroblastoma ( 39 ). NK-derived exosomes may take on the cytolytic activity after a short time interval and/or at low concentrations and are advantageous in being detectable in peripheral blood, diffusible into tissues, and thus having a cytolytic effect at the tumor sites ( 37 ).…”