Faculty Bibliography

INTRODUCTION/BACKGROUND:For many types of cancers, successful metastasis is critically dependent on tumor cell survival under flow conditions in the lymphatic system as well as attachment to the lymphatic endothelium at distal sites. In the lymphatic system, tumor cells are exposed to dynamic forces of laminar shear stress; however, there are currently no models to study the effects of these dynamic fluid forces on colorectal cancer metastasis. This study aims to establish the rudiments of an in vitro flow system that mimics the conditions to which tumor colorectal cancer cells (CRCCs) are exposed during lymphatic spread. METHODS:Human CRCCs (RKO and HCT-8) were cultured on collagen-1 coated glass slides in 10% fetal bovine serum, and grown until 50% confluence under static conditions. Subconfluent cells were then treated with laminar shear stress (1.2 dynes/cm(2)) using a Flexcell Streamer (Flexcell International Corp., Hillsborough, NC) parallel plate chamber for up to 48 h, in the continued presence of serum. Control conditions consisted of cells maintained under static conditions (0 dynes/cm(2)). Cells were examined with digital microscopy. Cell number was determined directly by cell count. Poly (ADP-ribose) polymerase-1, caspase-3, matrix metalloproteinase (MMP)-2, MMP-9, and vascular endothelial growth factor C levels were measured by Western blot. RESULTS:CRCCs survived under conditions of lymphatic flow (1.2 dynes/cm(2)), and were confluent by 48 h. Although a small number of cells (10% to 15%) initially detached upon exposure to shear stress, the majority of cells remained attached, and mitotic cells were observed. Cells demonstrated increased attachment and spreading under lymphatic flow compared with cells kept under control conditions. Cell number increased in cells treated with both lymphatic flow and static conditions by similar amounts until confluence was achieved. Cleaved products of poly (ADP-ribose) polymerase-1 and caspase-3 were not observed. MMP-2, MMP-9, and vascular endothelial growth factor C were expressed to similar degrees at all time points in cells exposed to lymphatic flow. CONCLUSIONS:Using a novel in vitro model of lymphatic flow, we describe colorectal tumor cell proliferation and expression of peptides critical to lymphatic spread under flow conditions. The ability to model lymphatic spread in vitro will allow additional studies to determine mechanisms of tumor cell survival in the lymphatic system.

Vascular endothelial growth factor (VEGF) is a potent secreted mitogen critical for physiologic and tumor angiogenesis. Regulation of VEGF occurs at several levels, including transcription, mRNA stabilization, translation, and differential cellular localization of various isoforms. Recent advances in our understanding of post-transcriptional regulation of VEGF include identification of the stabilizing mRNA binding protein, HuR, and the discovery of internal ribosomal entry sites in the 5'UTR of the VEGF mRNA. Monoclonal anti-VEGF antibody was recently approved for use in humans, but suffers from the need for high systemic doses. RNA interference (RNAi) technology is being used in vitro and in animal models with promising results. Here, we review the literature on post-transcriptional regulation of VEGF and describe recent progress in targeting these mechanisms for therapeutic benefit.

BACKGROUND:A variety of factors influence the increased morbidity and mortality seen in patients undergoing emergent colon surgery. Understanding comorbid conditions and variations in preoperative laboratory values that effect both morbidity and mortality can influence clinical decision making. METHODS:During a 5-year period 185 patients underwent colon surgery at the Veterans Administration Hospital in West Haven, CT. Through a retrospective chart review patients were classified as having either emergent or elective surgery. Patient characteristics and postoperative outcomes were analyzed using Chi Square and logistic regression models. RESULTS:Differences existed in preoperative variables as well as postoperative outcomes when comparing emergent and elective paitents. In those patients undergoing emergent colorectal surgery, both morbidity and mortality were increased and overall survival decresed when compared to a non-emergent population. CONCLUSIONS:Through identification of preoperative variables such as a hematocrit <30, the use of steroids, an albumin <3.5, and a creatinine of >1.4, those patients at risk for postoperative morbidity and mortality can be identified and clinical decision making can be appropriately adjusted.

HYPOTHESIS/OBJECTIVE:By using short interfering RNA (siRNA) to inhibit the in vitro expression of vascular endothelial growth factor (VEGF) A, we hope to further investigate the presence of an autocrine loop in colon cancer cells. We hypothesize that VEGF inhibition will result in decreased cellular proliferation. DESIGN/METHODS:Human colon cancer cells were evaluated for the expression of VEGF and VEGF receptor 2 (VEGFR-2). In vitro assessments were then made of the ability of anti-VEGF siRNA to knock down expression of VEGF and the subsequent effect this decreased expression had on colon cancer cell proliferation. SETTING/METHODS:Surgical oncology research laboratory. INTERVENTIONS/METHODS:Human colon cancer cells from the RKO cell line were transfected with siRNA targeting the coding region of VEGF. MAIN OUTCOME MEASURES/METHODS:Enzyme-linked immunosorbent assay, Northern blot analysis, and real-time quantitative polymerase chain reaction were performed to establish the ability of siRNA to decrease VEGF production. Proliferation assays were run on transfected and wild-type cells to establish concomitant decrease in VEGF expression and cellular proliferation. RESULTS:The RKO colon cancer cells expressed both VEGF and VEGFR-2. Those cells transfected with siRNA targeting VEGF showed a 94% knockdown in VEGF expression and a 67% decrease in cellular proliferation. CONCLUSION/CONCLUSIONS:Colon cancer cells expressing VEGF and VEGFR-2 may possess an autocrine growth pathway that can be effectively targeted using RNA interference as an antiangiogenic therapy.

PURPOSE OF REVIEW/OBJECTIVE:Gastric carcinoid tumors are rare lesions but have been the focus of much scientific investigation. The incidence of gastric carcinoid appears to be increasing without a corresponding increase in survival, despite utilization of the latest available therapies. Therefore, there is great interest in furthering the understanding of the biologic basis of these tumors, delineating the connection between hypergastrinemia and gastric carcinoids, and most importantly, improving upon current treatment options. RECENT FINDINGS/RESULTS:This review discusses the current biologic understanding of gastric carcinoid tumors, including the role of hypergastrinemia on enterochromaffin-like cell proliferation and its relation to acid-suppressive therapy. Numerous diagnostic and therapeutic modalities including endoscopic ultrasound, somatostatin receptor scintigraphy, long-acting octreotide, hepatic artery embolization, endoscopic mucosal resection, and surgical resection have also been the focus of recent investigations. SUMMARY/CONCLUSIONS:Despite the many advances that have been made in both the basic science and clinical arenas, the optimal treatment of gastric carcinoid tumors is still a matter of debate. As the understanding of the biologic basis of gastric carcinoid tumors increases, the treatment will likely be a multimodal approach tailored to individual tumor biology and will incorporate a variety of diagnostic and therapeutic modalities.