Pro-Inflammatory Microenvironment Modulates the Transfer of Mutated TP53 Mediated by Tumor Exosomes.

Rossana Domenis,Martina Fabris,Adriana Cifù,Catia Mio,Francesco Curcio

doi:10.3390/ijms22126258

Abstract

Exosomes released from tumor cells are instrumental in shaping the local tumor microenvironment to allow cancer progression. Recently, it has been shown that tumor exosomes carry large fragments of dsDNA, which may reflect the mutational status of parental cells. Although it has been described that a stressful microenvironment can influence exosomal cargo, the effects on DNA packing and its transfer into recipient cells have yet to be investigated. Here, we report that exosomes derived from SW480 (human colorectal adenocarcinoma cell line) cells can carry dsDNA fragments containing the entire coding sequence of both TP53 and KRAS genes, harboring the SW480-related TP53 c.818G > A and KRAS c.35G > T typical mutations. We also report the following: that cell stimulation with lipopolysaccharides (LPS) promotes the selective packaging of the TP53 gene, but not the KRAS gene; that exosomes secreted by SW480 cells efficiently transfer the mutated sequences into normal CCD841-CoN colon epithelial and THLE-2 hepatic cells; that this mechanism is more efficient when the cells had been previously incubated with pro-inflammatory cytokines; that the TP53 gene appears actively transcribed in both recipient cells; and that mutated mRNA levels are not influenced by cytokine treatment. Our data strongly suggest that pro-inflammatory stimulation promotes the horizontal transfer of an oncogene by exosomes, although this remains a rare event. Further studies are needed to assess the impact of the oncogenic transfer by exosomes in malignant transformation and its role in tumor progression.

Highlights

Exosomes are nanometer-sized active carriers with a key role in the intercellular communication system
In patients with pancreatic cancer, large fragments of double-stranded genomic DNA have been identified in circulating exosomes [3], suggesting that a large proportion of plasma cell-free human DNA is transported in exosomes [4] and that this mechanism is important for maintaining cellular homeostasis by allowing the elimination of damaged DNA [5]
Our aim in this study is to evaluate the hypothesis that a pro-inflammatory stimulus may modulate the transfer of mutated genes into exosomes and support their transcription into recipient cells, amplifying the ability of exosomes to induce malignant transformation

Summary

Introduction

Exosomes are nanometer-sized active carriers with a key role in the intercellular communication system. They are involved in several physiological functions and pathological conditions [1]. Exosomes transport diverse and specific repertoires of nucleic acids and proteins, which suggests the existence of a sorting mechanism that regulates the composition of their cargo [2]. In patients with pancreatic cancer, large fragments of double-stranded genomic DNA have been identified in circulating exosomes [3], suggesting that a large proportion of plasma cell-free human DNA is transported in exosomes [4] and that this mechanism is important for maintaining cellular homeostasis by allowing the elimination of damaged DNA [5]. The inhibition of exosome secretion leads to the accumulation of nuclear DNA in the cytoplasm and triggers a reactive oxygen species (ROS)-dependent DNA damage response (DDR) [5], which in turn results in cell cycle arrest and apoptosis

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Results

Conclusion