Junji Wada

Lipopolysaccharide (LPS) increases the invasive ability of pancreatic cancer cells through the TLR4/MyD88 signaling pathway†

Inflammation plays a multifaceted role in cancer progression, and NF‐κB is one of the key factors connecting inflammation with cancer progression. We have shown that lipopolysaccharide (LPS) promotes NF‐κB activation in colon cancer cells and pancreatic cancer cells. However, it is unclear why inflammatory stimuli can induce NF‐κB activation in cancer cells.

γ-Secretase Inhibitors Enhance Taxane-Induced Mitotic Arrest and Apoptosis in Colon Cancer Cells

BACKGROUND & AIMS Colorectal cancers are resistant to conventional chemotherapeutic treatments, including taxanes. gamma-Secretase is a multimeric membrane protein complex responsible for the intramembrane proteolysis of various type I transmembrane proteins, including amyloid beta-precursor protein and Notch. gamma-Secretase inhibitors have attracted increasing interest as anticancer drugs because of their ability to inhibit Notch signaling. However, the therapeutic usefulness of gamma-secretase inhibitors against colorectal cancers remains unclear. METHODS The effects of gamma-secretase inhibitors on growth and apoptosis induced by various chemotherapeutic agents in colon cancer cells were evaluated using Hoechst 33342 staining, colony formation assay, and cell cycle analysis. The effect of gamma-secretase inhibitors on taxane-induced mitotic arrest was evaluated using the cyclin B1-associated histone H1 kinase assay and MPM-2 reactivity. The involvement of Notch signaling was evaluated by the silencing of Notch/CBF1 signaling by RNA interference. RESULTS gamma-Secretase inhibitors enhanced taxane-induced mitotic arrest and apoptosis of colon cancer cells both in vitro and in vivo, although gamma-secretase inhibitors alone did not affect growth and apoptosis of colon cancer cells. We also showed that this effect by gamma-secretase inhibitors was restricted to taxanes and colon cancer cells. Silencing of Notch/CBF1 signaling failed to affect paclitaxel-induced mitotic arrest and apoptosis. CONCLUSIONS These data suggest that gamma-secretase inhibitors could be a new therapeutic modality for overcoming resistance to taxanes in colorectal cancers.

Gli1 contributes to the invasiveness of pancreatic cancer through matrix metalloproteinase‐9 activation

The hedgehog (Hh) signaling pathway has been reported to be associated with the growth of pancreatic cancer, but its role in the invasive phenotype is poorly understood. Therefore, we investigated the role of the Hh pathway in pancreatic cancer cell invasiveness using a Matrigel invasion assay. Blockade of the Hh pathway by cyclopamine inhibited pancreatic cancer cell invasion in association with a decreased expression of matrix metalloproteinase (MMP)‐9. By contrast, activation of the Hh pathway by the addition of exogenous Sonic hedgehog increased cell invasion and MMP‐9 expression. Stable transfection of pancreatic cancer cells with Gli1 increased their invasiveness, which was associated with activation of MMP‐9. We also showed that inhibition of MMP‐9 by small interfering RNA blocked the increased invasiveness of Gli1‐transfected cells. Furthermore, inhibition of Gli1 by small interfering RNA suppressed the invasiveness and MMP‐9 expression of pancreatic cancer cells. Taken together, these findings suggest that members of the Hh pathway, especially Gli1, play an important role in the invasiveness of pancreatic cancer cells through the regulation of MMP‐9 expression. (Cancer Sci 2008; 99: 1377–1384)

VEGFR2 is selectively expressed by FOXP3high CD4+ Treg

CD25+ FOXP3+CD4+ T cells (Treg) have been considered to play an important role in immune tolerance against several tumor antigens. It has also been indicated that high‐level expression of FOXP3 (FOXP3high) is sufficient to confer suppressive activity to normal non‐Treg. Here, we showed for the first time that vascular endothelial growth factor receptor 2 (VEGFR2) is selectively expressed by FOXP3high but not FOXP3low Treg. Such VEGFR2+ Treg exist in several tissues including PBMC and malignant effusion‐derived lymphocytes. In conclusion, VEGFR2 may be a novel target for controlling Treg with highly suppressive function.

Crosstalk of hedgehog and Wnt pathways in gastric cancer

Morphogenic signals like Hedgehog (Hh) and Wnt are reported to play critical roles in the progression of gastric cancer. We aimed to assess the relationship between Hh and Wnt signaling pathways. In 58 gastric cancer specimens, Wnt pathway activation was inversely correlated with Hh pathway activation. When AGS gastric cancer cells, in which Wnt signaling was constitutively active, were used as a target cell line, Gli1 overexpression suppressed Wnt transcriptional activity, nuclear beta-catenin accumulation and proliferation of AGS cells. Knock-down of beta-catenin by siRNA suppressed Wnt pathway activity and proliferation of AGS cells. Our data may provide some clues for the treatment of gastric cancer associated with Wnt signaling activation.

A large quantity of CD3-/CD19-/CD16- lymphocytes in malignant pleural effusion from a patient with recurrent cholangio cell carcinoma.

Tumor infiltrating lymphocytes (TILs) are candidates for adoptive cellular immunotherapy. Here we report on a patient whose TILs presented unusual lymphocyte antigens. Pleural effusions were collected from a 47-year-old man with recurrent cholangio cell carcinoma and malignant effusion. Effusion- associated lymphocytes (EALs) were separated by Ficoll-Hypaque gradient, and the EAL phenotype was determined by flow cytometry. The percentage of positive cells was determined for each lymphocyte-related differentiation antigen. The percentages of CD3+, CD19+, and CD16+ lymphocyte subpopulations among EALs were 20%, 7%, and 3%, respectively. Nearly 70% of EALs were CD3− /CD19− /CD56− /CD16−cells. The phenotypes of peripheral blood lymphocytes (PBLs) collected simultaneously from the patients peripheral blood were CD3+ (52%), CD19+ (20%), and CD16+ (20%).When EALs were cultured in medium without pleural effusion, T cell-related antigens, but not B cell- or natural killer (NK) cell-related antigens, were newly expressed on EALs, and this expression reached a plateau after 48 h in culture. The proportions of CD3+, CD19+, and CD16+ cells were 69%, 7%, and 3%, respectively. However, when EALs were cultured in medium with pleural effusion, increased expression of T cell-related antigens was not observed; the proportions of CD3+, CD19+, and CD16+ cells were 16%, 6%, and 1%, respectively. Neither total cell numbers nor cellular viability of EALs changed significantly after in-vitro culture, suggesting that significant proliferation or death of EALs did not occur during the culture period. Co-culture of the patients PBLs with autologous pleural effusion for 96 h did not alter the expression of lymphocyte-related antigens on the PBLs. These results indicate that expression of T cell-related antigens, but not B cell- or NK cell-related antigens, on EALs was blocked temporarily by the malignant pleural effusion. This is the first report concerning the existence of a large quantity of unclassified lymphocytes in which the T cell-related antigens were reversibly masked in the malignant pleural effusion.