Bubble-free rapid microfluidic PCR.

Microfluidic polymerase chain reaction (PCR) has been of great interest owing to its ability to perform rapid and specific nucleic acid amplification and analysis on small volumes of samples. One of the major drawbacks of microfluidic PCR is bubble generation and reagent evaporation, which can cause malfunctions. Here, through theoretical modeling and characterization of bubble behavior, we propose a bubble-free microfluidic PCR device via controlled fluid transfer. Our approach exploits a thin impermeable polyethylene (PE) top layer that minimizes the generation of bubbles by inhibiting mass transport along a vertical direction. Simulation results demonstrate that a calculated mass flow difference of approximately 370% can be obtained by utilizing an impermeable membrane as the vertical barrier layer. To demonstrate proof-of-concept, two nanoporous polymeric materials, poly(dimethylsiloxane) (PDMS) and PE, were used for stand-alone self-powered sample loading (approximately 70 s) and for use as a vertical barrier layer, respectively. Consequently, we demonstrate successful amplification of the cMET gene, a nucleic acid (NA) biomarker for lung cancer, and complete an ultrafast PCR test in less than 3 min using a high powered Peltier-based thermal cycler under bubble-free conditions. This approach will result in a new paradigm for ultrafast molecular diagnosis and can facilitate NA-based nearly instantaneous diagnostics for point-of-care testing and for personalized and preventive medicine.

Identification of Tyrosine-Phosphorylated Proteins Upregulated during Epithelial-Mesenchymal Transition Induced with TGF-ß.

The epithelial-to-mesenchymal transition (EMT) is a unique process for the phenotypic changes of tumor cells characterized by a transition from polarized rigid epithelial cells to migrant mesenchymal cells, thus conferring the ability of tumor invasion and metastasis. A major challenge in the treatment of lung adenocarcinoma is to identify early stage patients at a high risk of recurrence or metastasis, thereby permitting the best therapeutic strategy and prognosis. In this study, we used a transforming growth factor-ß (TGF-ß)-induced EMT model to quantitatively identify protein tyrosine phosphorylation during the course of EMT in relation to malignant characteristics of lung adenocarcinoma cells. We performed relative quantitation analysis of tyrosine-phosphorylated peptides in TGF-ß-treated and -untreated lung adenocarcinoma cells and identified tyrosine-phosphorylated proteins that were upregulated in TGF-ß-treated cells. These include tensin-1 (TNS1) phosphorylated on Y1404, hepatocyte growth factor receptor (c-Met) phosphorylated on Y1234, and NT-3 growth factor receptor (TrkC) phosphorylated on Y516. We also found that these protein phosphorylation profiles were specifically observed in tissue samples of patients with poor prognostic lung adenocarcinoma. Tyrosine phosphorylations of these proteins represent possible candidates of prognostic prediction markers for lung adenocarcinoma.

Separation of phosphoprotein isotypes having the same number of phosphate groups using phosphate-affinity SDS-PAGE.

Herein, we demonstrate the separation of phosphoprotein isotypes having the same number of phosphate groups using phosphate-affinity SDS-PAGE. The phosphate-affinity site is a polyacrylamide-bound Phos-tag that enables the mobility shift detection of phosphoproteins from their nonphosphorylated counterparts. As the first practical example of the separation, we characterized the monophosphorylated Tau isotypes by each of three tyrosine kinases, c-Abl, MET, and Fyn. Each monophosphoisotype phosphorylated at the Tyr-394, Tyr-197, or Tyr-18 was detected as three distinct migration bands. As a further application, we extended this technique to the mobility shift analysis of His and Asp phosphoisotypes in the Sinorhizobium meliloti FixL/FixJ two-component system. FixL is autophosphorylated at the His-285 with ATP, and the phosphate group is transferred to the Asp-54 of FixJ and subsequently removed by the FixL phosphatase activity. Using this method, we first performed simultaneous detection of the phosphorylated and nonphosphorylated isotypes of FixL and FixJ generated in their phosphotransfer reaction in vitro. As a result, a monophosphoisotype of FixL containing the phosphorylated His residue was confirmed. As for FixJ, on the other hand, two monophosphoisotypes were detected as two distinct migration bands. One is a well-known isotype phosphorylated at the Asp-54. The other is a novel isotype phosphorylated at the His-84.

Detection of hepatocyte growth factor/scatter factor receptor (c-Met) and MUC1 from the axillary fluid drainage in patients after breast cancer surgery.

BACKGROUND: Drains are inserted in the dissected axilla of most patients during surgery for breast cancer. OBJECTIVE: To evaluate the presence and prognostic value of MUC1 and Met-hepatocyte growth factor/scatter factor in the axillary drainage of these patients. METHODS: The study group included 40 consecutive patients with invasive ductal carcinoma of the breast who were suitable for breast-conserving treatment; 20 malignant melanoma patients found to have negative axillary sentinel lymph node served as the control group. The output of the drains, which had been placed in the axilla during operation, was collected, and the presence of MUC1, Met-HGF/SF and beta-actin were assessed in the lymphatic fluid by reverse transcription-polymerase chain reaction assays. The data were compared to the pathologic features of the tumor and the axillary lymph nodes, and to the estrogen and progesterone receptors status. RESULTS: RT-PCR assays of the axillary lymphatic drainage were positive for MUC1 and Met-HGF/SF in 15 (37.5%) and 26 (65%) of the patients, respectively. Patients in whom MUC1 and Met-HGF/SF were not found in the axillary fluid had smaller tumors and less capillary and lymphatic invasion, compared to patients with positive assays (P < 0.0 for all these comparisons). The lymph nodes were negative for metastases in all patients with negative assays (P < 0.001). The presence of MUC1 and Met-HGF/SF showed negative correlations with the estrogen and progesterone receptors (P < 0.05). CONCLUSION: MUC1 and Met-HGF/SF can be detected in the axillary fluids of patients with breast cancer. The expression of both tumor markers in the axillary drainage is strongly associated with unfavorable tumor features and can be used as a prognostic factor.

Dissociation of heparan sulfate and receptor binding domains of hepatocyte growth factor reveals that heparan sulfate-c-met interaction facilitates signaling.

Hepatocyte growth factor (HGF) is a secreted, heparan sulfate (HS) glycosaminoglycan-binding protein that stimulates mitogenesis, motogenesis, and morphogenesis in a wide array of cellular targets, including hepatocytes and other epithelial cells, melanocytes, endothelial cells, and hematopoietic cells. NK1 is an alternative HGF isoform that consists of the N-terminal (N) and first kringle (K1) domains of full-length HGF and stimulates all major HGF biological activities. Within NK1, the N domain retains the HS binding properties of full-length HGF and mediates HS-stimulated ligand oligomerization but lacks significant mitogenic or motogenic activity. In contrast, K1 does not bind HS, but it stimulates receptor and mitogen-activated protein kinase activation, mitogenesis, and motogenesis, demonstrating that structurally distinct and dissociable domains of HGF are the primary mediators of HS binding and receptor activation. Despite the absence of HS-K1 binding, K1 mitogenic activity in HS-negative cells is strictly dependent on added soluble heparin, whereas K1-stimulated motility is not. We also found that, like the receptors for fibroblast growth factors, the HGF receptor c-Met binds tightly to HS. These data suggest that HS can facilitate HGF signaling through interaction with c-Met that is independent of HGF-HS interaction and that the recruitment of specific intracellular effectors that mediate distinct HGF responses such as mitogenesis and motility is regulated by HS-c-Met interaction at the cell surface.

HGF/SF modifies the interaction between its receptor c-Met, and the E-cadherin/catenin complex in prostate cancer cells.

The effect of HGF/SF on the association between the E-cadherin/catenin complex and the tyrosine kinase receptor c-Met, was examined in prostate cancer cells LNCap FGC. Stimulation by HGF/SF showed E-cadherin and beta-catenin to be co-precipitated and located at areas of cell-cell contact with the HGF/SF receptor c-Met, as detected by immunoprecipitation and immunofluorescence respectively. Furthermore, continued exposure to this motogen increased the level of co-precipitations between the E-cadherin/catenin complex with c-Met, and also increased tyrosine phosphorylation of c-Met. In contrast, continued stimulation by HGF/SF decreased the level of co-localised peripheral staining and increased the level of cytoplasmic staining. In conclusion, the association between the E-cadherin/catenin complex with the HGF/SF receptor c-Met, may influence or regulate intercellular adhesion in prostate cancer following stimulation by HGF/SF.

Co-expression of hepatocyte growth factor and its receptor in human prostate cancer.

Hepatocyte growth factor acts differently depending on the organs or tumours involved. It may be produced simultaneously with its receptor, c-Met, in several types of malignant tumour cells and may exercise an autocrine regulation. To analyse the effect of hepatocyte growth factor in human prostate cancer, we conducted immunohistochemistry, in situ hybridization and the reverse transcriptase polymerase chain reaction. The first two techniques revealed the growth factor in prostate cancer cells, and the polymerase chain reaction confirmed this expression. c-Met is expressed in prostate cancer cells, but not in interstitial cells. Hepatocyte growth factor is expressed in interstitial cells, especially in hormone-treated cancer tissue, indicating that the growth factor pathway changes with the hormonal status. Low-grade tumours expressed c-Met at the plasma membrane. Higher grade tumours tended to express it in the cytoplasm, suggesting that the role of c-Met as the hepatocyte growth factor receptor was blocked in higher grade tumours. The relationship between the growth factor and its receptor is thus influenced by hormonal status and differentiation in prostate cancer and is not explained simply in terms of autocrine or paracrine action.