Molecular characterization of tumor-derived exosomes as tool for minimal residual disease monitoring

B cell malignancies, including Diffuse Large B-cell Lymphoma and Multiple Myeloma, are often characterized by incomplete response to clinical treatments that result in persistence of minimal residual disease with frequent fatal outcomes. In terms of disease staging and treatment regimen design, there is an urgent need to develop novel diagnostic tools which allow for non-invasive approaches to early detection of disease and for individualized disease state monitoring. Liquid biopsy allows cancer care providers to screen individual patients for the presence of tumor indicators using a simple blood test, thus providing an alternative approach to the costly and sometimes "risky" traditional biopsy procedures. Reflecting the genomic and proteomic profile of their parental cells, exosomes are potential biomarkers for the prediction of cancer burden, which could have a relevant impact on personalized therapy. We successfully validated the screening of random peptide libraries as a method to identify peptide binders for the idiotypic determinants of the immunoglobulin B Cell Receptor (IgBCRs). Recently, we demonstrated that tumor B cell-derived exosomes express the IgBCR of their parental B-cells, thus constituting a personal "barcode" of tumor clones which can be subsequently targeted by so-called “Id-peptides” (Iaccino E. et al. Molecular Cancer 2017). Moreover, in these studies the analysis of tumor-derived exosomes (TDEs) allowed an earlier detection of tumor growth compared to the conventional measure of serum paraprotein. In translating this research to the clinic, our work describes the design of an innovative technological platform allowing for a comprehensive TDEs characterization. Putting these ideas into practice, Id- peptides targeting TDEs has been tested by in vitro assays. The identified Id-peptides has been used to develop a multicolor flow cytometric protocol for TDEs high-sensitivity detection allowing a multiplexed approach in the isolation and enrichment of TDEs subpopulations, aimed at the comprehensive next-generation sequencing and proteomic analysis of TDEs contains.