An in vitro culture platform for studying the effect of collective cell migration on spatial self-organization within induced pluripotent stem cell colonies.

BACKGROUND: Human induced pluripotent stem cells (hiPSCs) provide an in vitro system to identify the impact of cell behavior on the earliest stages of cell fate specification during human development. Here, we developed an hiPSC-based model to study the effect of collective cell migration in meso-endodermal lineage segregation and cell fate decisions through the control of space confinement using a detachable ring culture system. RESULTS: The actomyosin organization of cells at the edge of undifferentiated colonies formed in a ring barrier differed from that of the cells in the center of the colony. In addition, even in the absence of exogenous supplements, ectoderm, mesoderm, endoderm, and extraembryonic cells differentiated following the induction of collective cell migration at the colony edge by removing the ring-barrier. However, when collective cell migration was inhibited by blocking E-cadherin function, this fate decision within an hiPSC colony was altered to an ectodermal fate. Furthermore, the induction of collective cell migration at the colony edge using an endodermal induction media enhanced endodermal differentiation efficiency in association with cadherin switching, which is involved in the epithelial-mesenchymal transition. CONCLUSIONS: Our findings suggest that collective cell migration can be an effective way to drive the segregation of mesoderm and endoderm lineages, and cell fate decisions of hiPSCs.

A Novel Combination Therapy for Human Oxaliplatin-resistant Colorectal Cancer Using Oxaliplatin and Coxsackievirus A11.

BACKGROUND: Colorectal cancer (CRC) is a major cause of morbidity and mortality throughout the world. It is the third most common cancer worldwide and the fourth most common cause of cancer-related death. FOLFOX, a combination of leucovorin calcium, fluorouracil, and oxaliplatin, is the first-line chemotherapy for stage III and stage IV CRC. However, patients with FOLFOX-resistant CRC have a poor prognosis. In recent years, virochemotherapy has been proposed as a potential treatment for chemotherapy-resistant cancer. MATERIALS AND METHODS: Through our first screening assay, we found that coxsackievirus A11 (CVA11) displayed potent oncolytic activities. We tested whether coxsackievirus A11 (CVA11) has oncolytic activity in human CRC cells in vitro and in vivo. We also examined whether pretreatment of oxaliplatin-resistant CRC cells with oxaliplatin enhances the oncolytic activity of CVA11. RESULTS: We found that CVA11 was potently oncolytic against the oxaliplatin-sensitive Caco-2 cell line, but had little effect on the oxaliplatin-resistant line WiDr. However, pretreatment of WiDr cells with oxaliplatin enhanced the oncolytic activity of CVA11, and the combination therapy was more cytotoxic than either oxaliplatin treatment or CVA11 infection alone. Furthermore, growth of subcutaneous WiDr tumors in a xenograft model was significantly lower in mice treated with oxaliplatin followed by intratumoral CVA11 injection compared with mice receiving either treatment alone. CONCLUSION: Oxaliplatin pretreatment sensitized oxaliplatin-resistant CRC cells to lysis by CVA11 infection in vitro and in vivo. Taken together, these findings identify a novel potential chemovirotherapeutic modality for the treatment of oxaliplatin-resistant human CRC.

Lamin A reassembly at the end of mitosis is regulated by its SUMO-interacting motif.

Modification of proteins with small ubiquitin-related modifier (SUMO; SUMOylation) is involved in the regulation of various biological processes. Recent studies have demonstrated that noncovalent associations between SUMOylated proteins and co-operative proteins containing SUMO-interacting motifs (SIMs) are important for the spatiotemporal organization of many protein complexes. In this study, we demonstrate that interactions between lamin A, a major component of the nuclear lamina, and SUMO isoforms are dependent on one of the four SIMs (SIM3) resided in lamin A polypeptide in vitro. Live cell imaging and immunofluorescence staining showed that SIM3 is required for accumulation of lamin A on the chromosomes during telophase, and subsequent evaluation of a panel of deletion mutants determined that a 156-amino acid region spanning the carboxyl-terminal Ig-fold domain of lamin A is sufficient for this accumulation. Notably, mutation of SIM3 abrogated the dephosphorylation of mitosis-specific phosphorylation at Ser-22 of lamin A, which normally occurs during telophase, and the subsequent nuclear lamina reorganization. Furthermore, expression of a conjugation-defective SUMO2 mutant, which was previously shown to inhibit endogenous SUMOylation in a dominant-negative manner, also impaired the accumulation of wild type lamin A on telophase chromosomes. These findings suggest that interactions between SIM3 of lamin A and a putative SUMO2-modified protein plays an important role in the reorganization of the nuclear lamina at the end of mitosis.