Abstract 366P
Background
The functional role of exosomes (EXs) is currently deeply studied in oncology, representing a new tool to study resistance and to predict tumor response to immunotherapy.We previously demonstrated that, EXs from the peripheral blood mononuclear cells (PBMC-EXs) may be used for selection of immune-responsive lung cancer patients and that they exhibit an in vitro ability to affect cancer cell death and tumor aggressiveness. We aimed to demonstrate that the antitumor immune response in patients is modulated by the existence of a functional crosstalk between PBMCs and tumor derived-exosomes (TEXs) and that TEXs are also able to promote EMT by activation of fibronectin-integrin α5β1 axis in cancer cells.
Methods
TEXs were isolated from H1975, PC9 and PC9 Osimertinib Resistant cells (PC9 OR) using differential ultracentrifugation steps. WB and FACS analysis were performed to detect EXs markers HSP70, CD9 and CD81 as well as the expression of fibronectin and the immune-checkpoint PDL-1. Furthermore, to detect the effect on immune system modulation, we incubated the exosomes from sensitive and resistant cells with PBMCs derived from NSCLC patients.
Results
TEXs showed a mean size of 100–130 nm and were positive for exosomes markers. They were able to promote cell migration and showed significant expression of PDL-1 and fibronectin that were found at highest levels in PC9OR.We also found that PC9OR-TEXs were able to increase the mRNA expression of PD1, CTLA-4 and FOXP3 in PBMCs, along with an increase of IL-2, INF-γ, TGF-βR and TNF-α levels. In addition, FACS analysis showed that PC9OR-TEXs caused the highest reduction of the CD3+ T cell subset in PBMCs. Parallel experiments also demonstrated that TEXs are able to promote EMT activation in the same cells they released from and that this mechanism is mediated by interaction of fibronectin carried by exosomes with α5β1 integrin expressed on cell surface.
Conclusions
Our findings indicated that TEXs are able to both mediate cross-talk between PBMCs and cancer cells and promote EMT-mediated resistance. The highest immunomodulation and EMT promoting were induced by TEXs from OR cells thus indicating a relevant role of exosomes in mediating resistance to osimertinib in NSCLC patients.
Funding
Associazione Italiana Ricerca sul Cancro (AIRC)
Disclosure
All authors have declared no conflicts of interest.