Stability of the LATS2 tumor suppressor gene is regulated by tristetraprolin.

LATS2 is a tumor suppressor gene implicated in the control of cell growth and the cell cycle. Here, we investigated the post-transcriptional regulation of LATS2 expression by tristetraprolin (TTP). Our results show that the expression level of LATS2 is inversely correlated with TTP expression in human cancer cell lines. Overexpression of TTP reduced the expression level of LATS2. Conversely, treatment with small interfering RNA against TTP increased the expression level of LATS2 through stabilization of LATS2 mRNA and suppressed the proliferation of A549 human lung cancer cells. LATS2 mRNA contains AU-rich elements (AREs) within the 3'-untranslated region, and TTP destabilized a luciferase mRNA containing LATS2 ARE. In addition, RNA electrophoretic mobility shift assay revealed that TTP directly bound to the ARE of LATS2 mRNA. These results establish LATS2 mRNA as a physiological target of TTP and suggest the possibility that TTP controls cell growth through regulation of LATS2 mRNA stability.

Tristetraprolin downregulates the expression of both VEGF and COX-2 in human colon cancer.

BACKGROUND/AIMS: Although both VEGF and COX-2 are important factors influencing angiogenesis (and thus, carcinogenesis), the regulation of these factors in carcinogenesis remains poorly understood. The aim is to investigate the effects of tristetraprolin, an AU-rich element-binding protein on the expression of VEGF and COX-2 in human colon cancer cells. METHODOLOGY: Expression of TTP, VEGF and COX-2 in the resected colorectal cancer surgical specimens were analyzed by immunohistochemistry. Colon cancer cells were transfected with luciferase reporter linked to 3'UTR of VEGF or COX-2. The effects of TTP overexpression on the expression of VEGF, COX-2 and luciferase were determined by semiquantitative RT-PCR or luciferase assay. RESULTS: Immunohistochemical staining of resected colorectal cancer surgical specimens revealed that TTP expression was low in cancer cells but high in non-malignant mucosa. In contrast, the expression of both COX-2 and VEGF was high in cancer cells and very low in non-malignant mucosa. TTP overexpression markedly decreased the expression of both COX-2 and VEGF in colon cancer cells. In addition, TTP inhibited the expression of luciferase linked to 3'UTR of COX-2 or VEGF mRNA. CONCLUSIONS: TTP inhibits the expression of both VEGF and COX-2 and reduced expression of TTP may be responsible for the increased expression of COX-2 and VEGF in human colorectal cancer.

Tristetraprolin regulates expression of VEGF and tumorigenesis in human colon cancer.

Tristetraprolin (TTP) is an AU-rich element-binding protein that regulates mRNA stability. Here, we report that TTP suppress the growth of human colon cancer cells both in vivo and in vitro by regulating of the expression of vascular endothelial growth factor (VEGF). TTP protein expression in human colonic tissues was markedly decreased in colonic adenocarcinoma compared with in normal mucosa and adenoma. VEGF expression was higher in colonic adenocarcinoma than in normal mucosa and adenoma. Specific inhibition of TTP expression by RNA-interference increased the expression of VEGF in cultured human colon cancer cells, and TTP overexpression markedly decreased it. In addition, elevated expression of TTP decreased the expression level of luciferase linked to a 3' terminal AU-rich element (ARE) of VEGF mRNA. Colo320/TTP cells overexpressing TTP grew slowly in vitro and became tumors small in size when xenografted s.c into nude mice. These findings demonstrate that TTP acts as a negative regulator of VEGF gene expression in colon cancer cells, suggesting that it can be used as novel therapeutic agent to treat colon cancer.

Reactive oxygen species-dependent EndoG release mediates cisplatin-induced caspase-independent apoptosis in human head and neck squamous carcinoma cells.

Cisplatin is a chemotherapeutic agent that is widely used to treat cancers such as head and neck squamous cell carcinoma (HNSCC). Previously, we have reported that cisplatin induced an early caspase-dependent apoptosis (8 hr) in a HNSCC cell, HN4. In this study, we examined a late caspase-independent apoptosis as well as an early caspase-dependent apoptosis in cisplatin-treated HN4 cells. While z-VAD-fmk, a pan-caspase inhibitor, blocked the caspase activities and protected cells from the early apoptosis, it did not provide protection against delayed apoptosis occurring after extended exposure (16 hr) to cisplatin, suggesting that the delayed apoptotic response in the presence of z-VAD-fmk was caspase-independent. Cisplatin treatment induced reactive oxygen species (ROS) generation, loss of the mitochondrial membrane potential (MMP) and nuclear translocation of endonuclease G (EndoG). Small interfering RNA mediated-knockdown of EndoG significantly protected cells from the delayed apoptosis induced by cisplatin in the presence of z-VAD-fmk. Overexpression of Bcl-2 in HN4 cells prevented loss of MMP, nuclear translocation of EndoG and protected cells from the delayed apoptosis induced by cisplatin in the presence of z-VAD-fmk. Pretreatment with N-acetyl-L-cysteine (NAC), a ROS scavenger, prevented both ROS generation, loss of the MMP and nuclear translocation of EndoG. Together, our data indicate that cisplatin treatment induced ROS-mediated loss of the MMP, and, then, the nuclear translocation of EndoG, which played a crucial role in caspase-independent apoptosis of HN4 cells in the presence of z-VAD-fmk. This is the first report about the involvement of EndoG in cisplatin-induced caspase-independent apoptosis of cells.

Heat shock protein 27 is associated with irinotecan resistance in human colorectal cancer cells.

Heat shock protein (Hsp) in tumor cells has been proposed to enhance their resistance to chemotherapeutic agents. In the present study, we investigated the influence of Hsp expression on the irinotecan resistance of human colorectal cancer cells. Among eight Hsp genes tested in this study, we confirmed that the expression of Hsp27 correlated with irinotecan resistance in colorectal cancer cells. Specific inhibition of Hsp27 expression using an antisense oliogodeoxynucleotide increased the irinotecan sensitivity. On the contrary, an overexpression of Hsp27 decreased the irinotecan sensitivity in colorectal cancer cells. Elevated expression of Hsp27 decreased caspase-3 activity in colorectal cancer cells. The expression level of Hsp27 determined by immunohistochemical analysis correlated with the clinical response to irinotecan in colorectal cancer patients. Hsp27 expression levels of irinotecan-non-responder (mean staining score, 6.28; proportion of high staining score, 64.2%) were significantly higher compared to those of irinotecan-responder (mean staining score, 3.16; proportion of high staining score, 33.3%) (P for t-test=0.045). These findings suggest that Hsp27 is involved in the irinotecan resistance of colorectal cancer cells possibly by reducing caspase-3 activity.

NF-kappaB activation is required for cisplatin-induced apoptosis in head and neck squamous carcinoma cells.

This study demonstrates a requirement for NF-kappaB activation in cis-diamminedichloroplatinum (cisplatin)-induced apoptosis in human head and neck squamous cell carcinoma (HNSCC) cell lines. This conclusion was supported by the following observations: cisplatin induced IkappaBalpha degradation and NF-kappaB-dependent transcriptional activation prior to cell death; pyrrolidine dithiocarbamate (PDTC), a chemical inhibitor of NF-kappaB activation, prevented apoptosis; lactacystin, an inhibitor of IkappaBalpha degradation, also prevented apoptosis; and finally, the expression of a super-repressor mutant IkappaBalpha blocked apoptosis. The expression of tumor necrosis factor alpha (TNFalpha) was promoted by cisplatin treatment and was suppressed by PDTC treatment. In addition, a neutralizing antibody against TNFalpha protected cells from cisplatin-induced apoptosis. These findings suggest that NF-kappaB activation is required for cisplatin-induced apoptosis and TNFalpha may play an important role in NF-kappaB-mediated apoptosis in cisplatin-treated HNSCC cell lines.

Benign retroperitoneal schwannoma: surgical consideration.

Schwannoma, which arises from the neural sheath of peripheral nerves, is the most common benign tumor in the retroperitoneum in adults. Complete excision is the treatment of choice for retroperitoneal schwannoma. During surgery, it seems to be unnecessary to identify the small peripheral nerve from which it develops. Keeping a dry field, however, through meticulous control of fine vasculature is of primary importance to avoid inadvertent injury to any of the adjacent organs, large vessels or important nerves. There are few vessels, if any, on the anterior and lateral surfaces of the tumor. Numerous small vessels to and from the tumors are located at its posterior and medial (aortic) aspects, without forming large trunks. Harmonic scalpel may be a good armamentarium in this area. In conclusion, considering such multiple small tumor vessels running adjacent to the aorta, the surgeon should pay close attention to the course of central dissection of these tumors in the retroperitoneum.

Synovial sarcoma of the head and neck: a case of predominantly cystic mass.

We report a case of predominantly cystic synovial sarcoma partly adherent to the hyoid bone in the submental area. The mass demonstrated posterior acoustic enhancement at sonography and a complex cystic mass with mural nodules and solid septa at CT.

Butyrate response factor 1 enhances cisplatin sensitivity in human head and neck squamous cell carcinoma cell lines.

Cisplatin is a widely used chemotherapeutic agent in head and neck squamous cell carcinoma (HNSCC). Resistance to cisplatin is a common feature of HNSCC. To identify genes that may regulate cisplatin sensitivity, we carried out a cDNA microarray analysis of gene expression in cisplatin-sensitive and cisplatin-resistant HNSCC-derived cell lines. Among genes differentially expressed by cisplatin treatment, we have confirmed the elevated expression of butyrate responsive factor 1 (BRF1) in cisplatin-sensitive HNSCC cells and have demonstrated that the expression level of BRF1 is associated with cisplatin-sensitivity. Specific inhibition of BRF1 expression using an antisense oligodeoxynucleotide (ODN) decreased the cisplatin-sensitivity and, on the contrary, overexpression of BRF1 increased cisplatin-sensitivity in HNSCC cells. Elevated expression of BRF1 decreased the level of the human inhibitor of apoptosis protein-2 (cIAP2) and increased the caspase-3 activity in HNSCC cells. In addition, elevated expression of BRF1 decreased the expression level of enhanced green fluorescent protein (EGFP) linked to a 3' terminal AU-rich element (ARE) of cIAP2 mRNA. These findings demonstrate that BRF1 expression enhanced cisplatin sensitivity in HNSCC cells by reducing the levels of cIAP2 mRNA.

Combination chemotherapy with 5-fluorouracil and heptaplatin as first-line treatment in patients with advanced gastric cancer.

Heptaplatin is a recently developed platinum derivative. This agent has been reported to have a response rate of 17% as a single agent, and tolerable toxicity in the treatment of advanced gastric cancer. The aim of this study was to evaluate the efficacy and toxicity of a combination of 5-fluorouracil (5-FU) and heptaplatin in patients with advanced gastric cancer. Forty-seven chemotherapy-naive patients with advanced or recurred gastric cancer were recruited. 5-FU was administered over 120 hr by continuous intravenous infusion from day 1 to 5, at a daily dose of 1,000 mg/m2 and heptaplatin was administered over 1 hr by intravenous infusion on day 1 at 400 mg/m2, and this cycle was repeated every 4 weeks. The response rate was 21%, median progression-free survival was 1.9 months (95% CI, 1.6 to 2.2 months). Median overall survival was 6.2 months (95% CI, 4 to 8.4 months) and the 1-yr survival rate was 29% for all patients. The most frequent toxicity was proteinuria. Toxicities were generally mild and reversible. This study demonstrates that the combination of 5-FU/heptaplatin combination is less active but tolerated in patients with advance gastric cancer.