Peter O. Simon

Selective sigma-2 ligands preferentially bind to pancreatic adenocarcinomas: applications in diagnostic imaging and therapy

BackgroundResistance to modern adjuvant treatment is in part due to the failure of programmed cell death. Therefore the molecules that execute the apoptotic program are potential targets for the development of anti-cancer therapeutics. The sigma-2 receptor has been found to be over-expressed in some types of malignant tumors, and, recently, small molecule ligands to the sigma-2 receptor were found to induce cancer cell apoptosis.ResultsThe sigma-2 receptor was expressed at high levels in both human and murine pancreas cancer cell lines, with minimal or limited expression in normal tissues, including: brain, kidney, liver, lung, pancreas and spleen. Micro-PET imaging was used to demonstrate that the sigma-2 receptor was preferentially expressed in tumor as opposed to normal tissues in pancreas tumor allograft-bearing mice. Two structurally distinct sigma-2 receptor ligands, SV119 and WC26, were found to induce apoptosis to mice and human pancreatic cancer cells in vitro and in vivo. Sigma-2 receptor ligands induced apoptosis in a dose dependent fashion in all pancreatic cell lines tested. At the highest dose tested (10 μM), all sigma-2 receptor ligands induced 10–20% apoptosis in all pancreatic cancer cell lines tested (p < 0.05). In pancreas tumor allograft-bearing mice, a single bolus dose of WC26 caused approximately 50% apoptosis in the tumor compared to no appreciable apoptosis in tumor-bearing, vehicle-injected control animals (p < 0.0001). WC26 significantly slowed tumor growth after a 5 day treatment compared to vehicle-injected control animals (p < 0.0001) and blood chemistry panels suggested that there is minimal peripheral toxicity.ConclusionWe demonstrate a novel therapeutic strategy that induces a significant increase in pancreas cancer cell death. This strategy highlights a new potential target for the treatment of pancreas cancer, which has little in the way of effective treatments.

Circulating Mesothelin Protein and Cellular Antimesothelin Immunity in Patients with Pancreatic Cancer

Purpose: Mesothelin is a glycoprotein expressed on normal mesothelial cells and is overexpressed in several histologic types of tumors including pancreatic adenocarcinomas. A soluble form of mesothelin has been detected in patients with ovarian cancer and malignant mesothelioma, and has prognostic value. Mesothelin has also been considered as a target for immune-based therapies. We conducted a study on the potential clinical utility of mesothelin as a biomarker for pancreatic disease and therapeutic target pancreatic cancer. Experimental Design: Tumor cell–bound and soluble mesothelin in patients was evaluated by immunohistochemistry and ELISA, respectively. The in vitro cellular immune response to mesothelin was evaluated by INFγ ELISA and intracellular cytokine staining for IFNγ in CD4+ and CD8+ T cells. The level of circulating antibodies to mesothelin was measured by ELISA. Results: All tumor tissue from patients with pancreatic adenocarcinoma expressed mesothelin (n = 10). Circulating mesothelin protein was detected in patients with pancreatic adenocarcinoma (73 of 74 patients) and benign pancreatic disease (5 of 5) but not in healthy individuals. Mesothelin-specific CD4+ and CD8+ T cells were generated from peripheral blood lymphocytes of patients with pancreatic cancer in 50% of patients compared with only 20% of healthy individuals. Antibodies reactive to mesothelin were detected in <3% of either patients or healthy individuals. Conclusions: Circulating mesothelin is a useful biomarker for pancreatic disease. Furthermore, mesothelin-specific T cells can be induced in patients with pancreatic cancer. This suggests that mesothelin is a potential target for immune-based intervention strategies in pancreatic cancer. (Clin Cancer Res 2009;15(21):6511–8)

Sigma-2 receptor ligands potentiate conventional chemotherapies and improve survival in models of pancreatic adenocarcinoma

BackgroundWe have previously reported that the sigma-2 receptor is highly expressed in pancreas cancer. Furthermore, we have demonstrated that sigma-2 receptor specific ligands induce apoptosis in a dose-dependent fashion. Here, we examined whether sigma-2 receptor ligands potentiate conventional chemotherapies such as gemcitabine and paclitaxel.MethodsMouse (Panc-02) and human (CFPAC-1, Panc-1, AsPC-1) pancreas cancer cell lines were used in this study. Apoptosis was determined by FACS or immunohistochemical analysis after TUNEL and Caspase-3 staining. Combination therapy with the sigma-2 ligand SV119 and the conventional chemotherapies gemcitabine and paclitaxel was evaluated in an allogenic animal model of pancreas cancer.ResultsSV119, gemcitabine, and paclitaxel induced apoptosis in a dose-dependent fashion in all pancreas cancer cell lines tested. Combinations demonstrated increases in apoptosis. Mice were treated with SV119 (1 mg/day) which was administered in combination with paclitaxel (300 μg/day) over 7 days to mice with established tumors. A survival benefit was observed with combination therapy (p = 0.0002). Every other day treatment of SV119 (1 mg/day) in combination with weekly treatment of gemcitabine (1.5 mg/week) for 2 weeks also showed a survival benefit (p = 0.046). Animals tolerated the combination therapy and no gross toxicity was noted in serum biochemistry data or on necropsy.ConclusionSV119 augments tumoricidal activity of paclitaxel and gemcitabine without major side effects. These results highlight the potential utility of the sigma-2 ligand as an adjuvant treatment in pancreas cancer.

Use of multifunctional sigma-2 receptor ligand conjugates to trigger cancer-selective cell death signaling

One major challenge in the development of cancer therapeutics is the selective delivery of the drugs to their cellular targets. In the case of pancreatic cancer, the σ-2 receptor is a unique target that triggers apoptosis upon activation. We have previously developed a series of chemical compounds with high affinity for the σ-2 receptor and showed rapid internalization of the ligands. One particular specific ligand of the σ-2 receptor, SV119, binds to pancreatic cancer cells and induces target cell death in vitro and in vivo. In this study, we characterized the ability of SV119 to selectively deliver other death-inducing cargos to augment the cytotoxic properties of SV119 itself. When conjugated to SV119, small molecules that are known to interfere with intracellular prosurvival pathways retained their ability to induce cell death, the efficiency of which was enhanced by the combinatorial effect of SV119 delivered with its small molecule cargo. Our findings define a simple platform technology to increase the tumor-selective delivery of small molecule therapeutics via σ-2 ligands, permitting chemotherapeutic synergy that can optimize efficacy and patient benefit.

Targeting AKT with the proapoptotic peptide, TAT-CTMP: a novel strategy for the treatment of human pancreatic adenocarcinoma.

Pancreatic adenocarcinoma carries an ominous prognosis and has little effective treatment. Several studies have demonstrated that the potently antiapoptotic phosphatidyl inositol 3′‐kinase (PI3K)—protein kinase B/AKT pathway is active in pancreas cancer. A recent study identified an endogenous AKT antagonist, carboxyl terminal modulator protein (CTMP). CTMP inhibits the phosphorylation of AKT, preventing full activation of the kinase. We screened several cell permeable peptides from the N‐terminal domain of CTMP (termed TAT‐CTMP1–4) in vitro and found one that caused significant apoptosis in pancreatic adenocarcinoma cell lines. An inactive variant of this peptide was synthesized and used as a negative control. In all cell lines tested, TAT‐CTMP4 induced a dose‐dependent increase in apoptosis as detected by %‐TUNEL positive cells and %‐active caspase‐3 (% active caspase‐3 ranged from 31.2 to 61.9 at the highest dose tested (10 μM). A screening of various cell and tissue types revealed that the proapoptotic activity was highest in pancreatic adenocarcinoma. TAT‐CTMP induced similar levels of active caspase‐3 as several other known inducers of apoptosis: gemcitabine, radiation therapy, wortmannin and recombinant tumor necrosis factor (TNF)‐α. No apoptosis was observed in donor human peripheral blood mononuclear cells (PBMC, p < 0.01). We further showed that TAT‐CTMP4 could augment either gemcitabine chemotherapy or radiation therapy, standard therapies for pancreas cancer. Pancreatic adenocarcinoma xenografts treated with a single dose of TAT‐CTMP4 demonstrated a marked increase in caspase‐3 positive tumor cells when compared with untreated controls. Additionally, pancreatic adenocarcinoma allografts treated with intratumoral TAT‐CTMP and systemic gemcitabine displayed a significantly smaller tumor burden while undergoing treatment than mice in control groups (p < 0.001). These data indicate that inhibiting AKT with CTMP may be of therapeutic benefit in the treatment of pancreatic adenocarcinoma and, when combined with established therapies, may result in an increase in tumor cell death.

A single-institution review of 157 patients presenting with benign and malignant tumors of the ampulla of Vater: Management and outcomes

BACKGROUND Although benign ampullary tumors are removed endoscopically, due to their potential to progress to malignant disease, the favored treatment for adenocarcinoma is pancreaticoduodenectomy. We reviewed our institutions experience in order to identify which patients were at highest risk of disease progression following surgical resection, as well as evaluate whether localized T1 tumors are best treated by pancreaticoduodenectomy. METHODS We retrospectively reviewed 157 patients who presented with an ampullary mass, from 2001 to 2010, and identified 51 with benign adenoma and 106 with adenocarcinoma. RESULTS Patients with malignant tumors most often presented with larger tumors and jaundice, which alone was predictive of survival (OR = 67). Forty-five percent of patients with pathologically confirmed T1 tumors had positive lymph nodes and median survival was modest at 60 months. Lymph node involvement was predictive of recurrence and decreased survival. CONCLUSION Patients with malignant tumors often present with jaundice and larger tumors. These findings should warrant suspicion for cancer and expedited preoperative workup. Based on our finding that nearly half the patients with T1 tumors had positive lymph nodes, we recommend pancreaticoduodenectomy for any patient with biopsy proven adenocarcinoma who is a suitable candidate for surgery.

The effect of mesh reinforcement of a stapled transection line on the rate of pancreatic occlusion failure after distal pancreatectomy: review of a single institution's experience

BACKGROUND Pancreatic occlusion failure (POF) after distal pancreatectomy remains a common source of morbidity. Here, we review our experience with distal pancreatectomy and attempt to identify factors which influence POF rates. PATIENTS AND METHODS One hundred sixty-nine distal pancreatectomies were performed between 2002 and 2007. Review of the computerized medical records and physician office records was performed for all patients. Univariate and multivariate analyses were performed to determine factors which might influence the incidence of POF. The data set was analysed for factors which might influence the pancreatic occlusion rate. Analysis included patient and disease characteristics including: age, gender, body mass index (BMI), diagnosis, consistency of the pancreas and history of pancreatitis, as well as intra-operative variables including: surgeon, absorbable mesh reinforcement and operative approach. RESULTS POF was the most common peri-operative complication. POF was identified in 32 out of 169 patients (19%). Transection technique (hand sewn, stapled, stapled with mesh) and procedure complexity were factors associated with differences in POF rates by both univariate and multivariate analyses. POF was identified in 7 out of 70 patients (10%) when an absorbable mesh was utilized, and 25 of 99 patients (25%) when mesh was not utilized (P < 0.02). DISCUSSION These data suggest that a randomized controlled trial will be required to determine if mesh reinforcement reduces the rate and severity of POF after distal pancreatectomy.

Balloon-Occluded Retrograde Transvenous Obliteration of Gastric Varices

Balloon-occluded retrograde transvenous obliteration (BRTO) of gastric varices is an image-guided transcatheter procedure used to treat gastric varices with sclerosants rather than decompression of the portal venous system. The history of its development, relevant portal venous, and systemic venous anatomic considerations, techniques, indications, and early results will be reviewed. In addition, the status of the practice of BRTO in the United States will be discussed.

Utility of the Gyrus open forceps in hepatic parenchymal transection

OBJECTIVE This study aimed to evaluate if the Gyrus open forceps is a safe and efficient tool for hepatic parenchymal transection. BACKGROUND Blood loss during hepatic transection remains a significant risk factor for morbidity and mortality associated with liver surgery. Various electrosurgical devices have been engineered to reduce blood loss. The Gyrus open forceps is a bipolar cautery device which has recently been introduced into hepatic surgery. METHODS We conducted a single-institution, retrospective review of all liver resections performed from November 2005 through November 2007. Patients undergoing resection of at least two liver segments where the Gyrus was the primary method of transection were included. Patient charts were reviewed; clinicopathological data were collected. RESULTS Of the 215 open liver resections performed during the study period, 47 patients met the inclusion criteria. Mean patient age was 61 years; 34% were female. The majority required resection for malignant disease (94%); frequent indications included colorectal metastasis (66%), hepatocellular carcinoma (6%) and cholangiocarcinoma (4%). Right hemihepatectomy (49%), left hemihepatectomy (13%) and right trisectionectomy (13%) were the most frequently performed procedures. A total of 26 patients (55%) underwent a major ancillary procedure concurrently. There were no operative mortalities. Median operative time was 220 min (range 97-398 min). Inflow occlusion was required in nine patients (19%) for a median time of 12 min (range 3-30 min). Median total estimated blood loss was 400 ml (range 10-2000 ml) and 10 patients (21%) required perioperative transfusion. All patients had macroscopically negative margins. Median length of stay was 8 days. Two patients (4%) had clinically significant bile leak. The 30-day postoperative mortality was zero. CONCLUSIONS Use of the Gyrus open forceps appears to be a safe and efficient manner of hepatic parenchymal transection which allows rapid transection with acceptable blood loss, a low rate of perioperative transfusion, and minimal postoperative bile leak.