ADAPT identifies an ESCRT complex composition that discriminates VCaP from LNCaP prostate cancer cell exosomes.

Libraries of single-stranded oligodeoxynucleotides (ssODNs) can be enriched for sequences that specifically bind molecules on naïve complex biological samples like cells or tissues. Depending on the enrichment strategy, the ssODNs can identify molecules specifically associated with a defined biological condition, for example a pathological phenotype, and thus are potentially useful for biomarker discovery. We performed ADAPT, a variant of SELEX, on exosomes secreted by VCaP prostate cancer cells. A library of ∼1011 ssODNs was enriched for those that bind to VCaP exosomes and discriminate them from exosomes derived from LNCaP prostate cancer cells. Next-generation sequencing (NGS) identified the best discriminating ssODNs, nine of which were resynthesized and their discriminatory ability confirmed by qPCR. Affinity purification with one of the sequences (Sequence 7) combined with LC-MS/MS identified its molecular target complex, whereof most proteins are part of or associated with the multiprotein ESCRT complex participating in exosome biogenesis. Within this complex, YBX1 was identified as the directly-bound target protein. ADAPT thus is able to differentiate exosomes from cancer cell subtypes from the same lineage. The composition of ESCRT complexes in exosomes from VCaP versus LNCaP cells might constitute a discriminatory element between these prostate cancer subtypes.

Translocation of a Cell Surface Spliceosomal Complex Induces Alternative Splicing Events and Lymphoma Cell Necrosis.

Spliceosomal dysregulation dramatically affects many cellular processes, notably signal transduction, metabolism, and proliferation, and has led to the concept of targeting intracellular spliceosomal proteins to combat cancer. Here we show that a subset of lymphoma cells displays a spliceosomal complex on their surface, which we term surface spliceosomal complex (SSC). The SSC consists of at least 13 core components and was discovered as the binding target of the non-Hodgkin's lymphoma-specific aptamer C10.36. The aptamer triggers SSC internalization, causing global changes in alternative splicing patterns that eventually lead to necrotic cell death. Our study reveals an exceptional spatial arrangement of a spliceosomal complex and defines it not only as a potential target of anti-cancer drugs, but also suggests that its localization plays a fundamental role in cell survival.