UNRAVELING THE DUAL ROLE OF MULTIPLE MYELOMA EXTRACELLULAR VESICLES IN THERAPEUTIC SIRNA DELIVERY AND IMMUNE MODULATION

Multiple myeloma (MM) is a plasma cell malignancy that develops within a supportive, immunosuppressive bone marrow microenvironment (BMM). Progression from precursor stages, such as monoclonal gammopathy of undetermined significance (MGUS), to overt MM depends on this microenvironment, which provides critical growth and survival signals to malignant plasma cells. Among the mediators of intercellular communication, extracellular vesicles (EVs) have emerged as important carriers of biological information, transferring proteins, nucleic acids, and lipids to surrounding cells and influencing their phenotype and function. Due to their natural biocompatibility and tumor tropism, MM-derived EVs (MM-EVs) are of interest both as contributors to disease progression and as potential therapeutic delivery vehicles. This thesis represents a multidisciplinary effort to investigate a shared property of MM-EVs: their capacity to interact with recipient cells, be internalized, and deliver biologically active molecular cargo. In the first part of this work, this intrinsic delivery competence was explored in a controlled and deliberate engineered setting. Biodistribution studies demonstrated that MM-derived EVs preferentially accumulate in myeloma lesions in vivo, supporting their capacity to reach malignant plasma cells. Based on this observation, EVs were engineered to carry siRNA/miRNA cargo, and their ability to deliver functional RNA to MM cells was validated through measurable gene silencing. These findings demonstrate that MM-derived EVs can be artificially exploited as efficient and biologically competent delivery vehicles. In the second part of the thesis, the delivery properties of MM-EVs were investigated from a different perspective, focusing on their naturally occurring biological function. Rather than being externally engineered, EVs were studied in the context of their physiological interactions with immune cells, providing insight into how MM-derived EVs naturally mediate intercellular communication within the immune microenvironment. Exposure of peripheral blood mononuclear cells to MM-EVs was associated with reduced viability in specific immune subsets, including NK cells CD8⁺ and CD4⁺ T cells, as well as functional alterations in surviving CD8⁺ T cells characterized by reduced cytokine production and increased inhibitory receptor markers. These findings indicate that EV-mediated transfer of bioactive components can modulate immune cell function. Proteomic profiling of MM-EVs provides contextual insight into these observations. The EV cargo included proteins associated with signaling pathways involved in immune regulation, including components linked to Notch signaling. Taken together, this work supports the concept that MM-EVs can act as biologically active carriers capable of modulating recipient cell responses. Their ability to transfer complex molecular cargo may contribute to immune dysregulation in MM. Further studies dissecting the molecular determinants of EV uptake and downstream signaling will be required to clarify the mechanisms underlying these effects and to evaluate their relevance for therapeutic targeting or exploitation.