No abstract

Occult gastrointestinal bleeding frequently frustrates clinicians' attempts to locate the source. Foci of hemorrhage within the small bowel are often found only at laparotomy and can be attributed to Meckel's diverticula, carcinomas, or less frequently, pulsion-type diverticula. We report our experience with two patients whose jejunal diverticula resulted in recurrent episodes of massive gastrointestinal hemorrhage.

Inhibitors of histone deacetylases have been shown to enhance the sensitivity of cancer cells to tumor necrosis factor-related apoptosis-inducing ligand TRAIL-mediated cytotoxicity. Valproic acid (VA), a commonly used antiepileptic agent whose pharmacokinetics and toxicity profiles are well described, is a histone deacetylase inhibitor. This project aims to evaluate if VA can potentiate Apo2L/TRAIL-mediated cytotoxicity in cultured thoracic cancer cells and to elucidate the underlying molecular mechanism responsible for this effect. VA sensitized cultured thoracic cancer cells to Apo2L/TRAIL, as indicated by a 4-fold to a >20-fold reduction of Apo2L/TRAIL IC50 values in combination-treated cells. Although VA (0.5-5 mM) or Apo2L/TRAIL (20 ng/ml) induced less than 20% cell death, VA + Apo2L/TRAIL combinations caused 60% to 90% apoptosis of cancer cells. Moreover, substantial activation of caspases 8, 9, and 3, which was observed only in cells treated with the drug combination, was completely suppressed by Bcl2 overexpression or by the caspase 9 inhibitor. Both the caspase 9 inhibitor and Bcl2 completely abrogated the substantial cytotoxicity and apoptosis induced by this combination, thus highlighting the pivotal role of the type II pathway in this process. These findings provide a rationale for the development of VA and Apo2L/TRAIL combination as a novel molecular therapeutic for thoracic cancers.

Carcinosarcoma of the esophagus is a rare malignant neoplasm, predominantly affecting men in their seventh decade of life. While presenting symptoms and anatomic location of squamous cell and carcinosarcoma of the esophagus are similar, the latter often presents as a large intraluminal polypoid mass on barium esophagram. The more favorable prognosis associated with carcinosarcoma versus other esophageal neoplasms has been attributed to early onset of symptoms, resulting in prompt diagnosis, and a lower propensity for tumor invasion. We report the case of an elderly woman presenting with dysphagia who was initially diagnosed with esophageal leiyomyosarcoma. Final tumor pathology showed esophageal carcinosarcoma.

Despite adequately expressing tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors DR4/DR5, malignant cells are frequently refractory to the cytotoxic effect of this apoptosis-inducing ligand. The susceptibility of cancer cells to TRAIL can be potentiated by cisplatin (CDDP). This study was designed to evaluate the ability of cisplatin to enhance the cytotoxic effect of TRAIL gene therapy using the recombinant adenovirus-mediated tumor-selective expression of membrane-bound green fluorescence protein (GFP)-TRAIL fusion protein (AdVgTRAIL) on thoracic cancer cells and to elucidate the putative mechanisms responsible for this synergistic combination effect. While causing little death of cultured thoracic cancer cells by itself, AdVgTRAIL in combination with CDDP, on the other hand, mediated profound supra-additive cytotoxicity and apoptosis via a strong bystander effect. CDDP/AdVgTRAIL-induced cytotoxicity was completely abrogated either by the pancaspase inhibitor zVAD-fmk or by the selective caspase 9 inhibitor or by transient knockdown of caspase 9 by siRNA, indicating that this process was caspase-mediated and mitochondria-dependent. This was confirmed by the observation that Bcl2 overexpression protected the cells from combinationinduced cytotoxicity. Robust activation of caspase 8 activity in combination-treated cells was blocked by overexpression of Bcl2, indicating that caspase 8 activation was secondary to the mitochondria-mediated amplification feedback loop. Combining CDDP with AdVgTRAIL greatly enhances its tumoricidal efficacy in cultured thoracic cancer cells in vitro. The two agents interact to mediate profound activation of caspase cascade via recruitment of the mitochondria and positive feedback loop. The CDDP/ AdVgTRAIL combination also exhibits a strong antitumor effect in in vivo animal model of human cancer xenografts.

Apo2L/TRAIL is actively investigated as a novel targeted agent to directly induce apoptosis of susceptible cancer cells. Apo2L/TRAIL-refractory cells can be sensitized to the cytotoxic effect of this ligand by cytotoxic chemotherapeutics. The aim of this study was to evaluate the in vitro tumoricidal activity of the Apo2L/TRAIL + Trichostatin A in cultured thoracic cancer cells and to elucidate the molecular basis of the synergistic cytotoxicity of this combination. Concurrent exposure of cultured cancer cells to sublethal concentrations of Apo2L/TRAIL and Trichostatin A resulted in profound enhancement of Apo2L/TRAIL-mediated cytotoxicity in all cell lines regardless of their intrinsic susceptibility to this ligand. This combination was not toxic to primary normal cells. While Apo2L/TRAIL alone or Trichostatin A alone mediated < 20% cell death, 60 to 90% of cancer cells were apoptotic following treatment with TSA + Apo2L/TRAIL combinations. Complete translocation of Bax from the cytosol to the mitochondria compartment was mainly observed in combination-treated cells and this was correlated with robust elevation of caspase 9 proteolytic activity indicative of activation of the mitochondria apoptogenic effect. Profound TSA + Apo2L/TRAIL-mediated cytotoxicity and apoptosis were completely abrogated by either Bcl2 over-expression or by the selective caspase 9 inhibitor, highlighting the essential role of mitochondria-dependent apoptosis signaling cascade in this process. Moreover, increased caspase 8 activity observed in cells treated with the TSA + Apo2L/TRAIL combination was completely suppressed by Bcl-2 over-expression or by the selective caspase 9 inhibitor indicating that the elevated caspase 8 activity in combination-treated cells was secondary to a mitochondria-mediated amplification feedback loop of caspase activation. These finding form the basis for further development of HDAC inhibitors + Apo2L/TRAIL combination as novel targeted therapy for thoracic malignancies.

Cisplatin or paclitaxel synergistically interacts with Apo2L/TRAIL to mediate profound induction of apoptosis. The mitochondria-dependent caspase activation cascade and the amplification feedback loop are essential for the complete execution of the cell death program. Furthermore, our data identify mitochondria as the direct target for the development of more refined strategies to enhance the therapeutic effect of Apo2L/TRAIL as an anticancer agent.

Histone deacetylase inhibitors (HDACIs) are novel anticancer agents with potent cytotoxicity against a wide range of malignancies. We have previously demonstrated that either Calphostin C (CC) (a protein kinase C (PKC) inhibitor) or Parthenolide (an NF-kB inhibitor) abrogates HDACI-induced transcriptional activation of NF-kB and p21, which is associated with profound potentiation of HDACI-mediated induction of apoptosis. Valproic acid (VA), a commonly used antiepileptic agent, has recently been shown to be an HDACI. This study was aimed to evaluate the anticancer property of VA in thoracic cancer cells and the development of clinically relevant strategies to enhance VA-mediated induction of apoptosis using kinase inhibitors Staurosporine (STP) or its analogue UCN-01. Treating cultured thoracic cancer cells with VA (0.62 -10.0 mM) resulted in significant cell line-and dose-dependent growth inhibition (IC 50 values: 4.1 -6.0 mM) and cell cycle arrest at G1/S checkpoint with profound accumulation of cells at G0/G1 phase but little induction of apoptosis. Valproic acid, being an HDACI, caused significant dose-dependent accumulation of hyperacetylated histones, following 24 h of treatment. Valproic acid-mediated 5 -20-fold upregulation of transcriptional activity of NF-kB was substantially (50 -90%) suppressed by cotreatment with CC, STP or UCN-01. Whereas minimal death (o20%) was observed in cells treated with either VA (1.0 or 5.0 mM) alone or kinase inhibitors alone, 60 -90% of cells underwent apoptosis following exposure to combinations of VA þ kinase inhibitors. Kinase inhibitor-mediated suppression of NF-kB transcriptional activity played an important role in sensitising cancer cells to VA as direct inhibition of NF-kB by Parthenolide drastically synergised with VA to induce apoptosis (VA þ Parthenolide: 60 -90% compared to o20% following single-drug treatments). In conclusion, VA, a well-known antiepileptic drug, has mild growth-inhibitory activity on cultured cancer cells. The weak VA-mediated induction of apoptosis of thoracic cancer cells can be profoundly enhanced either by Parthenolide, a pharmacologic inhibitor of NF-kB, or by UCN-01 a kinase inhibitor that has already undergone phase I clinical development. Combinations of VA with either a PKC inhibitor or an NF-kB inhibitor are promising novel molecularly targeted therapeutics for thoracic cancers.