The most aggressive cancers, such as triple-negative breast cancer and pancreatic cancer, remain difficult to treat. Their malignancy does not rely on a single oncogenic target but rather on the dysregulation of multiple interconnected genes and signaling pathways within complex networks. This multifactorial nature makes the development of broadly effective treatments particularly challenging. In this context, microRNAs (miRNAs) are attracting growing interest: these small regulatory RNA molecules are able to act simultaneously on several gene networks, making them especially well suited to counteract the complexity of tumor aggressiveness. Their therapeutic use, however, faces a major obstacle: delivery. RNAs are vulnerable to degradation, often display suboptimal biodistribution, and can trigger undesirable immune responses.
To address this challenge, the authors identified a signature of extracellular vesicle–associated miRNAs functionally linked to the activity of the transcription factor NFAT3. Functional analyses showed that a combination of fifteen miRNAs, designated miR-Comb 15, is required to fully reproduce the anti-tumor effects of NFAT3-regulated vesicles, in both triple-negative breast cancer and pancreatic cancer models. Taken individually, single miRNAs exerted only partial activity. These effects were accompanied by the coordinated regulation of validated target genes controlling proliferation and invasion, supporting a mechanism of action based on network modulation rather than inhibition of a single target.
To promote therapeutic translation, the team used extracellular vesicles derived from HEK293T cells, a non-tumor source that can be produced at large scale and is readily modifiable. Using an optimized exogenous loading strategy based on a pH gradient, miR-Comb 15 was efficiently incorporated into the vesicles without compromising their integrity or intrinsic bioactivity, as confirmed by nanoparticle tracking size distribution analyses. Compared with other evaluated platforms, notably vesicles derived from human adipose tissue–derived mesenchymal stem cells and synthetic liposomes, HEK293T vesicles loaded with miR-Comb 15 consistently displayed the strongest anti-tumor activity, both in vitro and in vivo, in a murine orthotopic implantation model.
This work thus characterizes an NFAT3-dependent vesicular miRNA program and supports the value of extracellular vesicle–based delivery of therapeutic miRNA combinations as a strategy for aggressive cancers.