MicroRNA analysis of Natural Killer cell-derived exosomes: the microRNA let-7b-5p is enriched in exosomes and participates in their anti-tumor effects against pancreatic cancer cells

ABSTRACT

Natural Killer (NK) cells are important components of the immune system in the defense against tumor growth and metastasis. They release exosomes containing proteins and nucleic acids, including microRNAs (miRNAs). NK-derived exosomes play a role in the anti-tumor NK cell function since they are able to recognize and kill cancer cells. However, the involvement of exosomal miRNAs in the function of NK exosomes is poorly understood. In this study, we explored the miRNA content of NK exosomes by microarray as compared to their cellular counterparts. The expression of selected miRNAs and lytic potential of NK exosomes against childhood B acute lymphoblastic leukemia cells after co-cultures with pancreatic cancer cells were also evaluated. We identified a small subset of miRNAs, including miR-16-5p, miR-342-3p, miR-24-3p, miR-92a-3p and let-7b-5p that is highly expressed in NK exosomes. Moreover, we provide evidence that NK exosomes efficiently increase let-7b-5p expression in pancreatic cancer cells and induce inhibition of cell proliferation by targeting the cell cycle regulator CDK6. Let-7b-5p transfer by NK exosomes could represent a novel mechanism by which NK cells counteract tumor growth. However, both cytolytic activity and miRNA content of NK exosomes were reduced upon co-culture with pancreatic cancer cells. Alteration in the miRNA cargo of NK exosomes, together with their reduced cytotoxic activity, could represent another strategy exerted by cancer to evade the immune response. Our study provides new information on the molecular mechanisms used by NK exosomes to exert anti-tumor-activity and offers new clues to integrate cancer treatments with NK exosomes.

KEYWORDS:

• exosomes
• gene expression profiling
• microRNA
• Natural killer cells
• tumor microenvironment

Acknowledgments

We wish to thank the Eurofins Genomics and System Biosciences services for the support provided with processing of microarray experiments and exosome size characterization.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Microarray data are available in the public, open access repository Gene Expression Omnibus (GEO), with GEO accession number GSE186056, at https://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE186056.

Notes on contributions

ADP performed experiments, analyzed and interpreted data and wrote the article. AP designed and performed experiments, interpreted data and wrote the article. PF, FB and SS performed experiments. NT performed experiments and revised the manuscript. LQ revised the manuscript. PV and LM interpreted data and revised the manuscript.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/2162402X.2023.2221081

Additional information

Funding

This work was supported by the Associazione Italiana Ricerca sul Cancro (AIRC) under Investigator Grant ID: 19920 (LM) and Special Program Metastatic disease: the key unmet need in oncology 5 per mille 2018, ID 21147 (LM); Italian Ministry of Health under grant RF GR-2018-12365485 (AP). FB is recipient of fellowships awarded by AIRC fellowship for Italy.