Dimensionality-controlled insulator-metal transition and correlated metallic state in 5d transition metal oxides Sr n+1Ir nO3n+1 (n=1, 2, and infinity)

We investigated the electronic structures of the 5d Ruddlesden-Popper series Sr n+1Ir nO3n+1 (n=1, 2, and infinity) using optical spectroscopy and first-principles calculations. As 5d orbitals are spatially more extended than 3d or 4d orbitals, it has been widely accepted that correlation effects are minimal in 5d compounds. However, we observed a Mott insulator-metal transition with a change of bandwidth as we increased n. In addition, the artificially synthesized perovskite SrIrO3 showed a very large mass enhancement of about 6, indicating that it was in a correlated metallic state.

Fibulin 1 is downregulated through promoter hypermethylation in gastric cancer

Tumour suppressor genes (TSGs) were frequently inactivated through promoter hypermethylation in gastric carcinoma as well as pre-malignant gastric lesions, suggesting that promoter hypermethylation can be used as a marker to define novel TSGs and also biomarkers for early detection of gastric cancer. In an effort to search for such genes aberrantly methylated in gastric cancer development, fibulin 1 (FBLN1) was found as a candidate TSG epigenetically downregulated in gastric cancer. FBLN1 expression was downregulated in all of gastric cancer cell lines used (100%, 7 out of 7) and the primary gastric carcinoma tissues (84%, 86 out of 102) and significantly restored after pharmacological demethylation. Hypermethylation of the FBLN1 promoter was frequently (71%, 5 out of 7) detected in gastric cancer cell lines and primary gastric carcinoma tissues. Ectopic expression of FBLN1 led to the growth inhibition of gastric cancer cells through the induction of apoptosis. In summary, FBLN1 was identified as a novel candidate TSG epigenetically downregulated in gastric cancer.

Surgical treatment of esophageal leiomyoma located near or at the esophagogastric junction via a thoracoscopic approach

Esophageal leiomyoma can be enucleated safely and effectively by minimally invasive surgery. The laparoscopic approach has been a conventional option for this kind of tumor located near or at the esophagogastric (EG) junction. The aims of this study were to evaluate the surgical outcome of thoracoscopic resection of leiomyoma at the EG junction, and discuss factors affecting the incidence of postoperative gastroesophageal reflux. Fourteen patients who underwent thoracoscopic resection of esophageal leiomyoma located near or at the EG junction (<4 cm above the esophageal hiatus) from January 2002 to August 2007 were reviewed retrospectively. Tumor characteristics, surgical methods, and postoperative outcomes were evaluated. A left approach of video-assisted thoracoscopy was used in 13 patients; a right approach was used for the other patient, whose multiple tumors were located in the EG junction and mid-esophagus. Postoperative recovery was uneventful in all patients, with no mucosa leakage or other significant complications. Mean tumor size was 3.2 cm (1.2-6.0 cm). Of the 14 patients, two had serpiginous leiomyoma, two had multiple tumors, and the others had solitary tumors. Mean postoperative stay in hospital was 7 days (4-11 days). Postoperative dysphagia was not reported, although gastroesophageal reflux was noted in one patient. Thoracoscopic resection of esophageal leiomyomas near or at the EG junction is feasible, with a low prevalence of postoperative gastroesophageal reflux.

Colorectal cancer cells with the BRAF(V600E) mutation are addicted to the ERK1/2 pathway for growth factor-independent survival and repression of BIM

The RAF-mitogen-activated protein kinase kinase 1/2-extracellular signal-regulated kinase 1/2 (RAF-MEK1/2-ERK1/2) pathway is activated in many human tumours and can protect cells against growth factor deprivation; however, most such studies have relied upon overexpression of RAF or MEK constructs that are not found in tumours. Here we show that expression of the endogenous BRAF(V600E) allele in mouse embryonic fibroblasts from conditional knock-in transgenic mice activates ERK1/2, represses the BH3-only protein BIM and protects cells from growth factor withdrawal. Human colorectal cancer (CRC) cell lines harbouring BRAF(V600E) are growth factor independent for the activation of ERK1/2 and survival. However, treatment with the MEK1/2 inhibitors U0126, PD184352 or the novel clinical candidate AZD6244 (ARRY-142886) overcomes growth factor independence, causing CRC cell death. BIM is de-phosphorylated and upregulated following MEK1/2 inhibition in all CRC cell lines studied and knockdown of BIM reduces cell death, indicating that repression of BIM is a major part of the ability of BRAF(V600E) to confer growth factor-independent survival. We conclude that a single endogenous BRAF(V600E) allele is sufficient to repress BIM and prevent death arising from growth factor withdrawal, and CRC cells with BRAF(V600E) mutations are addicted to the ERK1/2 pathway for repression of BIM and growth factor-independent survival.

Modeling, analysis, and validation of a novel HIV integrase structure provide insights into the binding modes of potent integrase inhibitors

It has been shown that L-731988, a potent integrase inhibitor, targets a conformation of the integrase enzyme formed when complexed to viral DNA, with the 3'-end dinucleotide already cleaved. It has also been shown that diketo acid inhibitors bind to the strand transfer complex of integrase and are competitive with the host target DNA. However, published X-ray structures of HIV integrase do not include the DNA; thus, there is a need to develop a model representing the strand transfer complex. In this study, we have constructed an active-site model of the HIV-1 integrase complexed with viral DNA using the crystal structure of DNA-bound transposase and have identified a binding mode for inhibitors. This proposed binding mechanism for integrase inhibitors involves interaction with a specific Mg(2+) in the active site, accentuated by a hydrophobic interaction in a cavity formed by a flexible loop upon DNA binding. We further validated the integrase active-site model by selectively mutating key residues predicted to play an important role in the binding of inhibitors. Thus, we have a binding model that is applicable to a wide range of potent integrase inhibitors and is consistent with the available resistant mutation data.

[Reversal of multidrug resistance of gastric cancer cells by down-regulation of CIAPIN1 with CIAPIN1 siRNA]

The overexpression of a new cytokine-induced apoptosis inhibitor 1 (CIAPIN1) gene has been shown previously to promote a multidrug resistant phenotype in gastric cancer cells through the upregulation of MDR1 and MRP1. In the present study, we constructed the siRNA eukaryotic expression vectors of CIAPIN1 and transfected them into SGC7901/VCR cells to examine whether the down regulation of CIAPIN1 increased cell sensitivity towards chemotherapeutic drugs. After transfection, the expression of CIAPIN1 was dramatically decreased in CIAPIN1 siRNA transfectants compared with that in parental cells and empty vector control cells. The down-regulation of CIAPIN1 significantly enhanced the sensitivity of SGC7901/VCR cells to vincristine (VCR), adriamycin (ADR) and etoposide (VP-16), but not to 5-fluorouracil (5-FU) and cisplatin (CDDP). Cell capacity to efflux adriamycin decreased markedly in CIAPIN1 siRNA transfectants, and correlation between CIAPIN1 down regulation and decreased MDR1 transcriptional activity were observed. CIAPIN1 siRNA could significantly down regulate the expression of Bcl-2, and up-regulate the expression of Bax, but not alter the expression of PTEN in gastric cancer cells. These observations suggested that the siRNA constructs of CIAPIN1 we obtained could effectively down-regulate the expression of CIAPIN1 and reverse the resistant phenotype of gastric cancer cells. The further study of the biological functions of CIAPIN1 may be helpful for understanding the mechanisms of multidrug resistance of gastric cancer and developing possible strategies to treat gastric cancer.

Post-thaw viable CD34(+) cell count is a valuable predictor of haematopoietic stem cell engraftment in autologous peripheral blood stem cell transplantation

BACKGROUND AND OBJECTIVES

In peripheral blood stem cell transplantation, the number of CD34(+) cells infused is considered a predictor of haematopoietic engraftment. However, the currently accepted minimal threshold of CD34(+) cells/kg was determined by counting CD34(+) cells before freezing, and the loss of viable CD34(+) cells during freezing, cryopreservation or thawing prior to reinfusion has not been assessed.

MATERIALS AND METHODS

Total and viable CD34(+) cells were quantified using single platform flow cytometry and viability dye, 7-amino actinomycin D (7-ADD), at the time of collection and prior to reinfusion in 46 peripheral haematopoietic stem cell grafts from 36 patients. The time to engraftment of neutrophil and platelet was assessed by routine peripheral blood cell counts performed daily.

RESULTS

The median number of viable CD34(+) cells harvested was 3.6 x 10(6)/kg (range 0.05-21.2), and the median viability was 98% (range 70-100%) before freezing. After thawing, the median number of viable CD34(+) cells was reduced to 2.2 x 10(6)/kg (range 0.04-14.8) and the median viability was reduced to 71% (range 31-89%). The number of viable CD34(+) cells/kg before freezing and after thawing significantly correlated with engraftment of neutrophils (P < 0.0001 both) and platelets (P = 0.007 and 0.006, respectively). Although the minimum dose for engraftment (2.0 x 10(6) CD34(+) cells/kg) was harvested in 37 of 46 cases (85%), only 25 cases (54%) met this threshold at the time of reinfusion. For platelet engraftment, determination of viable CD34(+) cells prior to reinfusion was more important than enumeration at the time of collection.

CONCLUSION

Quantification of post-thaw viable CD34(+) cells better represents the actual composition of the graft and may be a more accurate predictor of haematopoietic engraftment than post-thaw total CD34(+) cell counts, or prefreeze determinations, especially for platelet engraftment. It is necessary to develop good quality controls for freezing and thawing procedures to minimize variance in cell viability.

Germline hMSH2 promoter mutation in a Chinese HNPCC kindred: evidence for dual role of LOH

Hereditary non-polyposis colorectal cancer (HNPCC) is a dominantly inherited cancer predisposition syndrome that is caused by germline mutations in mismatch repair genes. By screening the core promoters of hMSH2, hMLH1, and hMSH6 in 37 Chinese suspected HNPCC families, a novel germline mutation c.-78_-79delGT was found in the hMSH2 promoter. Its pathogenic effects were supported by the following findings: (a) it co-segregated with HNPCC-related cancers and was not present in the 220 control subjects, (b) tumors harboring the mutation lacked the expression of hMSH2 and showed high microsatellite instability, (c) it significantly decreased the promoter activity, and (d) it abolished the binding ability of the transcription factor E1A-F. Loss of heterozygosity (LOH) was found in three of the tumors studied. Intriguingly, in the tumors from patients II:1 and III:1, LOH occurred in the wild-type allele and agreed well with the traditional 'two-hit' model. In contrast, in the tumor from patient III:3, LOH occurred in the mutant allele. A pathogenic somatic mutation (c.2210+1G>A) was also found in this tumor; therefore, we proposed that the 'second hit' was inactivated by somatic mutation, and the mutant allele was lost during tumor progression; this provided evidence for the new hypothesis for the dual role of LOH.