Effect of sunitinib on TRAIL-induced apoptosis in preclinical colon cancer models

e14633

Background: Tumor necrosis factor related apoptosis-inducing ligand (TRAIL) is a potent inducer of apoptosis, however not all cancers respond to TRAIL, which may be due to activation of survival signals. Sunitinib is a potent inhibitor of multiple receptor tyrosine kinases, including vascular endothelial growth factor receptor (VEGFR) and platelet-derived growth factor receptor (PDGFR). These receptors and their signaling cascades promote cell survival and drug resistance. Inhibition of these pathways with sunitinib may augment TRAIL-mediated apoptosis. Aims: 1) Determine sensitivity of colon cancer cell lines to the combination of TRAIL and sunitinib, 2) identify mechanism by which sunitinib enhances TRAIL-mediated apoptosis, and 3) investigate the anticancer activity of this drug combination in xenograft models. Methods & Results: Sunitinib enhanced the anticancer activity of TRAIL in HCT116 and HCT15 colon cancer cell lines, with increased caspase cleavage and DNA fragmentation using western blot analysis and propidium iodide staining, respectively. Overexpression of Bcl-2 in HCT116 cells reduced TRAIL+sunitinib-mediated apoptosis, suggesting that sunitinib enhances TRAIL-induced apoptosis via activation of the mitochondrial apoptotic pathway. Sunitinib enhanced TRAIL-induced JNK activation, which may play a role in TRAIL+sunitinib-mediated apoptosis. Xenograft models of HCT116 and HCT15 were established in nude mice and treated with TRAIL, sunitinib, or the combination. The TRAIL+sunitinib combination significantly reduced tumor burden in both xenograft models compared to either treatment alone. The reduction in tumor volume correlated with increased apoptosis and decreased tumor proliferation and angiogenesis as determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay and immunohistochemistry for Proliferating Cell Nuclear Antigen and VEGF. Conclusion: These results are the first to demonstrate that simultaneous treatment with TRAIL and sunitinib reduced cell viability, induced apoptosis, inhibited tumor proliferation and angiogenesis in both in vitro and in vivo models of colon cancer, and warrants further investigation.

No significant financial relationships to disclose.

The catalytic subunit of the DNA polymerase of herpes simplex virus type 1 interacts specifically with the C terminus of the UL8 component of the viral helicase-primase complex

The herpes simplex virus type 1 (HSV-1) UL8 DNA replication protein is a component of a trimeric helicase-primase complex. Sixteen UL8-specific monoclonal antibodies (MAbs) were isolated and characterized. In initial immunoprecipitation experiments, one of these, MAb 804, was shown to coprecipitate POL, the catalytic subunit of the HSV-1 DNA polymerase, from extracts of insect cells infected with recombinant baculoviruses expressing the POL and UL8 proteins. Coprecipitation of POL was dependent on the presence of UL8 protein. Rapid enzyme-linked immunosorbent assays (ELISAs), in which one protein was bound to microtiter wells and binding of the other protein was detected with a UL8- or POL-specific MAb, were developed to investigate further the interaction between the two proteins. When tested in the ELISAs, five of the UL8-specific MAbs consistently inhibited the interaction, raising the possibility that these antibodies act by binding to epitopes at or near a site(s) on UL8 involved in its interaction with POL. The epitopes recognized by four of the inhibitory MAbs were approximately located by using a series of truncated UL8 proteins expressed in mammalian cells. Three of these MAbs recognized an epitope near the C terminus of UL8, which was subjected to fine mapping with a series of overlapping peptides. The C-terminal peptides were then tested in the ELISA for their ability to inhibit the POL-UL8 interaction: the most potent exhibited a 50% inhibitory concentration of approximately 5 microM. Our findings suggest that the UL8 protein may be involved in recruiting HSV-1 DNA polymerase into the viral DNA replication complex and also identify a potential new target for antiviral therapy.

The herpes simplex virus type 1 UL8 protein influences the intracellular localization of the UL52 but not the ICP8 or POL replication proteins in virus-infected cells

We have developed a panel of 14 monoclonal antibodies (MAbs) to POL, the catalytic subunit of herpes simplex virus type 1 (HSV-1) DNA polymerase encoded by gene UL30, and one MAb to the UL52 protein, another of the seven proteins essential for replication of HSV DNA. The approximate locations of the epitopes of the polymerase-specific MAbs were identified using truncated polymerase molecules, and the antibodies were characterized in a number of immunological assays allowing eight different specificities to be recognized. These MAbs, together with a polyclonal antibody raised in rabbits against a third DNA replication protein, ICP8, were used to localize the respective proteins by immunofluorescence in cells infected with wild-type HSV-1 or the DNA replication-defective mutants ambUL8 or 2-2. In BHK cells infected with ambUL8, a mutant with an amber termination codon within the coding region of gene UL8, the UL52 protein did not enter the nucleus, although ICP8 and POL entered the nucleus in a normal fashion. The failure of the UL52 protein to be correctly transported to the nucleus was also observed in both HFL and Vero cells infected with ambUL8. In contrast, UL52 protein was transported to the nucleus in BHK cells infected with wild-type HSV-1 or with 2-2, a mutant lacking a functional UL9 protein.

Rapid urease test in the management of Campylobacter pyloridis-associated gastritis

Campylobacter pyloridis colonization of the stomach may be an etiological factor in gastritis and peptic ulceration. Campylobacter pyloridis produces large amounts of urease, and the presence of this enzyme in gastric mucosa usually indicates infection with the organism. In this paper we describe the use of a rapid urease test (CLOtest) to detect C. pyloridis infection in gastric mucosal biopsies. In 141 consecutive endoscopy cases, antral biopsies were taken for culture and histology, and an extra biopsy was inserted into the CLOtest gel. There were 79 patients infected with C. pyloridis, 78 of whom were detected by CLOtest: 75% were positive at 20 min, 92% at 3 h, and 98% at 24 h. There were no false positive results. Eighteen infected patients were rebiopsied after a course of amoxycillin and bismuth subcitrate. Active chronic gastritis resolved in eight of nine who were cleared of the organism, but histological gastritis was unchanged in nine patients who were still infected. CLOtest is a simple, sensitive, and highly specific test that enables the endoscopist to diagnose C. pyloridis infection in the endoscopy room. A negative test after antibiotic therapy correlates with clearance of the bacteria and healing of active gastritis.

Antibacterial action of bismuth in relation to Campylobacter pyloridis colonization and gastritis

Colloidal bismuth subcitrate (CBS, De-Nol) heals duodenal ulcers but with a lower relapse rate than cimetidine, perhaps due to inhibition of Campylobacter pyloridis (CP) organisms. To test this hypothesis we studied gastric mucosal histology in three groups of ulcer patients treated with either cimetidine, CBS, or CBS in combination with an antibiotic. Cimetidine had no effect on CP or gastric mucosal histology but with CBS therapy there was a significant reduction in the number of bacteria (p less than 0.0001). However, relapse of both CP infection and gastritis usually occurred once CBS was withdrawn. When CBS was combined with amoxycillin or tinidazole, long-term disappearance of both CP bacteria and gastritis was achieved (p less than 0.0001). In ultrastructural studies 30-90 min after single oral doses of CBS or bismuth subsalicylate, CP had detached from the gastric epithelial cells and exhibited structural degradation associated with the selective deposition of a particulate bismuth complex within and upon the surface of the organisms. In vitro, CP and other campylobacters were inhibited by bismuth compounds at 25 mg/l but they were resistant to cimetidine and ranitidine. CBS has a powerful antibacterial effect against CP but relapse of infection is common after CBS alone. In combination with antibiotics however, eradication of CP and long-term healing of gastritis occurs. In such cases the gastroduodenal mucosa is intact, and less likely to ulcerate.