Liquid biopsy, consisting in the non-invasive analysis of circulating tumor-derived material (the Tumor Circulome), represents an innovative tool in precision oncology to overcome current limitations associated with tissue biopsies. Within the tumor circulome, ctDNA and CTCs are the only components whose clinical application is FDA-cleared. Extracellular vesicles, ctRNA and tumor-educated platelets are relatively novel tumor circulome constituents with promising potential at each stage of cancer management. Here, we discuss the clinical applications of each element of the tumor circulome and the prevailing factors that currently limit implementation in clinical practice. We also detail the most recent technological developments in the field, which demonstrate potential in improving the clinical value of liquid biopsies. Commented [GDR3R2]: Thanks for doing that Commented [MK(2]: Please include all weblinks in a separate section before "References", entitled "Resources" Commented [MK(1]: Please include all weblinks in a separate section before "References", entitled "Resources" Commented [MK(4]: Since this is how it is depicted in the Figure. Commented [MK(5]: I suggest that this be converted into "Key Figure". The Figure represents the contents of the review well. Commented [MK(6]: Are the authors talking about advances in sample isolation? I'd encourage you to give examples to align the readers to what advancements the authors are referring to. Commented [GDR7R6]: Done with some of the innovations discussed in the following chapters.

The confinement of multiple myeloma (MM) to the bone marrow microenvironment requires an invasive bone marrow biopsy to monitor the malignant compartment. The existing clinical tools used to determine treatment response and tumor relapse are limited in sensitivity mainly because they indirectly measure tumor burden inside the bone marrow and fail to capture the patchy, multisite tumor infiltrates associated with MM. Microparticles (MPs) are 0.1- to 1.0-μm membrane vesicles, which contain the cellular content of their originating cell. MPs are functional mediators and convey prothrombotic, promalignant, proresistance, and proinflammatory messages, establishing intercellular cross talk and bypassing the need for direct cell-cell contact in many pathologies. In this study, we analyzed plasma cell–derived MPs (CD138+) from deidentified MM patients (n = 64) and normal subjects (n = 18) using flow cytometry. The morphology and size of the MPs were further analyzed using scanning electron microscopy. Our study shows the proof of a systemic signature of MPs in MM patients. We observed that the levels of MPs were significantly elevated in MM corresponding to the tumor burden. We provide the first evidence for the presence of MPs in the peripheral blood of MM patients with potential applications in personalized MM clinical monitoring.

Cancer management paradigms are shifting towards a personalized approach thanks to the advent of the -omics technologies. Liquid biopsies, consisting in the sampling of blood and other bodily fluids, are emerging as a valid alternative to circulating tumor biomarkers and tumor tissue biopsies for cancer diagnosis, routine monitoring and prognostication. The content of a liquid biopsy is referred to as the "tumor circulome". Among its components, circulating tumor DNA (ctDNA), including both cell-free and exosome-associated DNA, is the most widely characterized element. ctDNA analysis has a tremendous capability in the diagnostic arena. Its potential has been demonstrated at each level of disease staging and management and supported by a recent FDA approval for companion diagnostic, and the investments being made by pharmaceutical companies in this sector are numerous. The approaches available for ctDNA analysis allow both quantitative and qualitative studies and range from PCR and dPCR-mediated single/multiple gene mutational assessment to whole genome next generation sequencing and methylation mapping. Although the principal object of a liquid biopsy is blood, other body fluids such as urine and saliva show potential as complementary DNA sources for tumor analysis. In this review we provide a synopsis on the state of play of current ctDNA application. We discuss the clinical significance of ctDNA analysis and review the state of the art of technologies being currently developed to this aim. We also discuss the current issues limiting ctDNA application and highlight the promising approaches being developed to overcome these.

BackgroundBreast cancer is the most frequently diagnosed cancer in women. Resident macrophages at distant sites provide a highly responsive and immunologically dynamic innate immune response against foreign infiltrates. Despite extensive characterization of the role of macrophages and other immune cells in malignant tissues, there is very little known about the mechanisms which facilitate metastatic breast cancer spread to distant sites of immunological integrity. The mechanisms by which a key healthy defense mechanism fails to protect distant sites from infiltration by metastatic cells in cancer patients remain undefined.Breast tumors, typical of many tumor types, shed membrane vesicles called microparticles (MPs), ranging in size from 0.1–1 μm in diameter. MPs serve as vectors in the intercellular transfer of functional proteins and nucleic acids and in drug sequestration. In addition, MPs are also emerging to be important players in the evasion of cancer cell immune surveillance.MethodsA comparative analysis of effects of MPs isolated from human breast cancer cells and non-malignant human brain endothelial cells were examined on THP-1 derived macrophages in vitro. MP-mediated effects on cell phenotype and functionality was assessed by cytokine analysis, cell chemotaxis and phagocytosis, immunolabelling, flow cytometry and confocal imaging. Student’s t-test or a one-way analysis of variance (ANOVA) was used for comparison and statistical analysis.ResultsIn this paper we report on the discovery of a new cellular basis for immune evasion, which is mediated by breast cancer derived MPs. MPs shed from multidrug resistant (MDR) cells were shown to selectively polarize macrophage cells to a functionally incapacitated state and facilitate their engulfment by foreign cells.ConclusionsWe propose this mechanism may serve to physically disrupt the inherent immune response prior to cancer cell colonization whilst releasing mediators required for the recruitment of distant immune cells. These findings introduce a new paradigm in cancer cell biology with significant implications in understanding breast cancer colonization at distant sites. Most importantly, this is also the first demonstration that MPs serve as conduits in a parallel pathway supporting the cellular survival of MDR cancer cells through immune evasion.

Abstract. Multiple myeloma (MM) is a mature B cell neoplasm that results in multi-organ failure. The median age of onset, diverse clinical manifestations, heterogeneous survival rate, clonal evolution, intrinsic and acquired drug resistance have impact on the therapeutic management of the disease.