Cheol-Woong Choi

Antitumor activity of sorafenib-incorporated nanoparticles of dextran/poly(dl-lactide-co-glycolide) block copolymer

Sorafenib-incoporated nanoparticles were prepared using a block copolymer that is composed of dextran and poly(DL-lactide-co-glycolide) [Dexb LG] for antitumor drug delivery. Sorafenib-incorporated nanoparticles were prepared by a nanoprecipitation-dialysis method. Sorafenib-incorporated Dexb LG nanoparticles were uniformly distributed in an aqueous solution regardless of the content of sorafenib. Transmission electron microscopy of the sorafenib-incorporated Dexb LG nanoparticles revealed a spherical shape with a diameter < 300 nm. Sorafenib-incorporated Dexb LG nanoparticles at a polymer/drug weight ratio of 40:5 showed a relatively uniform size and morphology. Higher initial drug feeding was associated with increased drug content in nanoparticles and in nanoparticle size. A drug release study revealed a decreased drug release rate with increasing drug content. In an in vitro anti-proliferation assay using human cholangiocarcinoma cells, sorafenib-incorporated Dexb LG nanoparticles showed a similar antitumor activity as sorafenib. Sorafenib-incorporated Dexb LG nanoparticles are promising candidates as vehicles for antitumor drug targeting.

A Hybrid Joining Technology for Aluminum/Zinc Coated Steels in Vehicles

Currently, in the automotive industry, joining of the aluminum alloys with the steel is a crucial problem to be solved. Conventional joining techniques including resistance spot and gas metal arc welding are not acceptable for those applications due to a number of metallurgical problems. The investigation was carried out to develop the hybrid joining process combining the resistance spot welding and brazing. In this study, an attempt was made to apply hybrid process to the joining of dissimilar sheet metals, Al-Mg-Si (6000 series) alloy and low carbon steel sheet. Hybrid process (resistance spot weld/brazing) using filler metal was found to be effective to overcome the incompatibility between aluminum alloy and steel. Although hybrid joining process of Al alloy sheet and steel sheet did not produce acceptable bond strength, it was proved to have reasonable interfacial bond layer if the optimal process condition was applied.

Second-look endoscopy and factors associated with delayed bleeding after endoscopic submucosal dissection

Endoscopic submucosal dissection (ESD) is a widely used procedure as curative treatment for superficial gastric neoplasms, including early gastric cancer without lymph node metastasis. However, ESD requires advanced endoscopic skill and there is a major concern regarding complications from bleeding. So far, extensive efforts have been made to develop strategies to reduce post-ESD bleeding. Use of proton pump inhibitors and coagulating exposed vessels on the ulcer floor after ESD are strategies known to reduce the risk of delayed bleeding. Second-look endoscopy (SLE) is also carried out to reduce delayed bleeding following ESD in many institutions. However, the incidence of bleeding still remains around 5%, and further measures are needed to reduce delayed bleeding after gastric ESD. Recently, three randomized studies indicated that routine SLE was unnecessary. Although routine SLE may not be recommended for all patients after gastric ESD, SLE might be an important tool for the prevention of the delayed bleeding in selected high-risk patients. Thus, the identification of the risk factors, such as large size of resected specimen and treatment with multiple antiplatelet medications, may help to further guide clinicians in deciding whether to perform SLE. Studies carried out on larger cohorts are necessary to clarify the efficacy of SLE after ESD in the prevention of post-ESD bleeding in potentially high-risk patients.

Effect of extramucin pools in gastric cancer patients

Purpose Mucinous gastric adenocarcinoma (MGC) is defined by the World Health Organization as a gastric adenocarcinoma with >50% extracellular mucin pools within the tumors. In this study, we attempted to analyze the clinicopathologic features of patients pathologically diagnosed as gastric cancer with lower than 50% tumor volume of extracellular mucin pool adenocarcinoma (LEMPC). We compared MGC versus nonmucinous gastric adenocarcinoma (NMGC). We were used in abbreviations LEMPC for NMGC including extracellular mucin pool. Methods Files of 995 patients with gastric cancer NMGC (n = 935), MGC (n = 20), LEMPC (n = 40) who underwent curative resection at Pusan National University Yangsan Hospital from December 2008 to December 2013 were retrospectively analyzed. All pathologic reports after curative resection and evaluated clinicopathologic features were reviewed to identify the effect of extracellular mucin pools in gastric cancer. Results Compared with the NMGC patients, the clinicopathological features of MGC patients were as follows: more frequent open surgery, larger tumor size, more advanced T stage and N stage, more positive lymph node metastasis, and perineural invasion. LEMPC patients showed similar features compared with NMGC patients. MGC and LEMPC patients showed similar clinicopathological features, except T stage and lymph node metastasis. Conclusion LEMPC can be thought of as a previous step of MGC. It is reasonable to consider LEMPC patients in the diagnostic criteria of MGC, and to adequately treat.