Tumor-derived exosomes are enriched in ΔNp73, which promotes oncogenic potential in acceptor cells and correlates with patient survival.

Tumor-derived exosomes are emerging as local and systemic cell-to-cell mediators of oncogenic information through the horizontal transfer of mRNAs, microRNAs and proteins during tumorigenesis. The exosomal content has been described as biologically active when taken up by the recipient cell. Identifying the specific molecular cargo of exosomes will help to determine their function in specific steps of the tumorigenic process. Here we evaluate whether ΔNp73 is selectively packaged in tumor-derived exosomes, its function in the acceptor cells in vitro and in vivo and its prognosis potential in cancer. ΔNp73 messenger is enriched in tumor-derived exosomes, suggesting its active sorting in these microvesicles. We observed the transmission of this exosome cargo to different cell types and how it confers proliferation potential and chemoresistance to the acceptor cells in vitro and in animal models. Finally, our data support the potential prognostic value of exosomal ΔNp73 in colon cancer patients.

Proteasome activator complex PA28 identified as an accessible target in prostate cancer by in vivo selection of human antibodies.

Antibody cancer therapies rely on systemically accessible targets and suitable antibodies that exert a functional activity or deliver a payload to the tumor site. Here, we present proof-of-principle of in vivo selection of human antibodies in tumor-bearing mice that identified a tumor-specific antibody able to deliver a payload and unveils the target antigen. By using an ex vivo enrichment process against freshly disaggregated tumors to purge the repertoire, in combination with in vivo biopanning at optimized phage circulation time, we have identified a human domain antibody capable of mediating selective localization of phage to human prostate cancer xenografts. Affinity chromatography followed by mass spectrometry analysis showed that the antibody recognizes the proteasome activator complex PA28. The specificity of soluble antibody was confirmed by demonstrating its binding to the active human PA28αß complex. Whereas systemically administered control phage was confined in the lumen of blood vessels of both normal tissues and tumors, the selected phage spread from tumor vessels into the perivascular tumor parenchyma. In these areas, the selected phage partially colocalized with PA28 complex. Furthermore, we found that the expression of the α subunit of PA28 [proteasome activator complex subunit 1 (PSME1)] is elevated in primary and metastatic human prostate cancer and used anti-PSME1 antibodies to show that PSME1 is an accessible marker in mouse xenograft tumors. These results support the use of PA28 as a tumor marker and a potential target for therapeutic intervention in prostate cancer.

Programming controlled adhesion of E. coli to target surfaces, cells, and tumors with synthetic adhesins.

In this work we report synthetic adhesins (SAs) enabling the rational design of the adhesion properties of E. coli. SAs have a modular structure comprising a stable ß-domain for outer membrane anchoring and surface-exposed immunoglobulin domains with high affinity and specificity that can be selected from large repertoires. SAs are constitutively and stably expressed in an E. coli strain lacking a conserved set of natural adhesins, directing a robust, fast, and specific adhesion of bacteria to target antigenic surfaces and cells. We demonstrate the functionality of SAs in vivo, showing that, compared to wild type E. coli, lower doses of engineered E. coli are sufficient to colonize solid tumors expressing an antigen recognized by the SA. In addition, lower levels of engineered bacteria were found in non-target tissues. Therefore, SAs provide stable and specific adhesion capabilities to E. coli against target surfaces of interest for diverse applications using live bacteria.

Basement membrane-rich organoids with functional human blood vessels are permissive niches for human breast cancer metastasis.

Metastatic breast cancer is the leading cause of death by malignancy in women worldwide. Tumor metastasis is a multistep process encompassing local invasion of cancer cells at primary tumor site, intravasation into the blood vessel, survival in systemic circulation, and extravasation across the endothelium to metastasize at a secondary site. However, only a small percentage of circulating cancer cells initiate metastatic colonies. This fact, together with the inaccessibility and structural complexity of target tissues has hampered the study of the later steps in cancer metastasis. In addition, most data are derived from in vivo models where critical steps such as intravasation/extravasation of human cancer cells are mediated by murine endothelial cells. Here, we developed a new mouse model to study the molecular and cellular mechanisms underlying late steps of the metastatic cascade. We have shown that a network of functional human blood vessels can be formed by co-implantation of human endothelial cells and mesenchymal cells, embedded within a reconstituted basement membrane-like matrix and inoculated subcutaneously into immunodeficient mice. The ability of circulating cancer cells to colonize these human vascularized organoids was next assessed in an orthotopic model of human breast cancer by bioluminescent imaging, molecular techniques and immunohistological analysis. We demonstrate that disseminated human breast cancer cells efficiently colonize organoids containing a functional microvessel network composed of human endothelial cells, connected to the mouse circulatory system. Human breast cancer cells could be clearly detected at different stages of the metastatic process: initial arrest in the human microvasculature, extravasation, and growth into avascular micrometastases. This new mouse model may help us to map the extravasation process with unprecedented detail, opening the way for the identification of relevant targets for therapeutic intervention.