Theoretical Insights into the Cotransport Mechanism of GSH with Anticancer Drugs by MRP1.

The multidrug resistance protein MRP1 is an ATP binding cassette (ABC) transporter that confers resistance to many anticancer drugs and regulates redox homeostasis, inflammation, and hormone secretion. MRP1 actively transports compounds across cell membranes, and the presence of glutathione (GSH) is required in many cases. However, the process of MRP1-mediated substrate transportation has been poorly understood. With extensive molecular dynamics simulations, we have found a sandwich-like structure which is generated by GSH, a transmembrane α-helices 11 (TM11)-TM17 axis, and anticancer drugs. This structure is crucial in MRP1 transportation. It triggers the motion of TM11 and TM17, followed by the movement of nucleotide-binding domains 1 (NBD1) and 2 (NBD2), and finally an occluded structure is formed. Trp1246, Lys332, and Phe594 were identified as the main contributors in the formation of the sandwich-like structure. Our findings clearly explain the synergy of GSH with an anticancer drug in MRP1 transportation and have significant meanings for the rational design of novel inhibitors against MRP1.

Fragment-centric topographic mapping method guides the understanding of ABCG2-inhibitor interactions.

Understanding protein-ligand interactions is crucial to drug discovery and design. However, it would be extremely difficult for the proteins which only have one available apo structure but multiple binding sites. To address this constraint, a fragment-centric topographic mapping method (AlphaSpace software) was employed to map out concave interaction pockets at the assigned protein region. These pockets are used as complementary spaces to screen the known inhibitors for this specific binding site and to guide the molecular docking pose selection as well as protein-ligand interaction analysis. By mapping the shape of central cavity surface, we have tested the strategy against a multi-drug resistant transmembrane protein-ABCG2 to assist in generating a pharmacophore model for its inhibitors that is based on the structure of apo. Classical molecular simulation and accelerated molecular simulation are used to verify the accuracy of inhibitor screening and binding pose selection. Our study not only has gained insight for the development of novel specific ABCG2 inhibitors, but also has provided a general strategy in describing protein-ligand interactions.

An adoptive T cell immunotherapy targeting cancer stem cells in a colon cancer model.

PURPOSE: Colon cancer is one of the most common malignancies worldwide. Cancer stem-like cells (CSCs) are a distinct subgroup of cancer cells that play a vital role in the development of cancer and also a role in the development of resistance against therapeutic agents. In this study we investigated the role of CSCs in colon cancer and evaluated the tumor-associated antigen CEP55 for targeting immunotherapeutically CSCs. METHODS: Side population (SP) cells from colon cancer cell line SW480, were isolated using DNA-binding dye Hoechst 33342. The cytotoxic activity of cytotoxic T lymphocytes (CTL) clone 41 for side population (SP) cells and main population (MP) cells was evaluated using 51Cr release assay. The SP cells, MP cells and presorted cells from the colon cancer cell line were evaluated in NOD/SCID mice. RESULTS: The isolated SP cells showed resistance to the chemotherapeutic agents irinotecan and oxaliplatin, which suggests that targeting the CSCs can be a better strategy for the treatment of chemotherapy-resistant colon cancer. HLA class I and HLA-A24 in SP cells and MP cells were expressed at the same level. We used CTL clone 41 to corroborate the sensitivity of SP cells to cytotoxic T lymphocyte response. The cytotoxic responses of SP cells were to the same extent as they were in MP cells and pre-sorted cells. Adoptive transfer of CTL clone 41 in immunodeficient mice inhibited SW480-induced tumors, suggesting that this approach can be used for colon cancer immunotherapy. CONCLUSION: Our novel findings suggest that colon cancer CSCs are sensitive to CTLs, and CEP55, a tumor-associated antigen, can be successfully used as active immunotherapy for targeting CSCs in colon cancer.

Intestinal obstruction due to migration of a thermometer from bladder to abdominal cavity: a case report.

Intraperitoneal foreign bodies such as retained surgical instruments can cause intestinal obstruction. However, intestinal obstruction due to transmural migration of foreign bodies has rarely been reported. Here, we report a case of intestinal obstruction due to a clinical thermometer which migrated from the bladder into the abdominal cavity. A 45-year-old man was admitted to our hospital with a one-year history of recurrent lower abdominal cramps. Two days before admission, the abdominal cramps aggravated. Intestinal obstruction was confirmed with upright abdominal radiography and computerized tomography scan which showed dilation of the small intestines and a thermometer in the abdominal cavity. Then laparotomy was performed. A scar was observed at the fundus of the bladder and a thermometer was adhering to the small bowels and mesentery which resulted in intestinal obstruction. Abdominal cramps were eliminated and defecation and flatus recovered soon after removal of the thermometer.