Epithelial-mesenchymal transition (EMT) has been reported to play an important role in the migration and invasion of tumor cells. Hematopoietic pre-B-cell leukemia transcription factor (PBX)-interacting protein (HPIP/PBXIP1) has emerged as an important regulator of the development of cancer. However, the role of HPIP in lung cancer is unclear. Thus, in the present study, we investigated the role of HPIP in transforming growth factor (TGF)-β1-induced EMT in A549 lung cancer cells in vitro. Our data demonstrated that HPIP was overexpressed in the lung cancer cell lines. TGF-β1 increased the expression of HPIP in the A549 cells. In addition, HPIP silencing significantly attenuated TGF-β1-induced EMT and migration/invasion in the A549 cells. Furthermore, knockdown of HPIP greatly inhibited TGF-β1-induced phosphorylation of Smad2 in the A549 cells. In conclusion, we demonstrated that HPIP silencing suppressed TGF-β1-induced EMT in lung cancer cells by inhibiting Smad2 activation. Therefore, HPIP may be a new therapeutic target for the treatment of lung cancer.

In pre-initiation complexes, RNA helicase A interacts with β-actin and acts as a bridging factor linking nuclear actin with RNA polymerase II (Pol II). In addition, β-actin participates in Pol IIdependent transcription elongation by interacting with the positive transcription elongation factor Cdk9. However, many relationships between β-actin and Pol II remain to be identified. In an interleukin 6 (IL-6)-induced p21 expression model, we demonstrated that β-actin knockdown reduced p21 expression. Immunofluorescence analysis showed that the colocalization of β-actin and Pol II increased significantly in cells treated with IL-6. It is known that the Rpb5, Rpb6 and Rpb7 subunits are located at the surface of the enzyme. We next constructed recombinant pcDNA-HA-Rpb5, pcDNA-HA-Rpb6 and pcDNA-HA-Rpb7 plasmids and expressed the three polymerase II subunits in HepG2 cells. We found that β-actin could be immunoprecipitated with HA-Rpb5 and HA-Rpb7. A Glutathione-S-transferase pull-down assay revealed that β-actin was associated with Rpb5 and Rpb7 in vitro. Furthermore, overexpression of Rpb5 and Rpb7 in cells reduced p21 expression significantly, suggesting that Rpb5 and Rpb7 competitively interact with β-actin. This study shows that β-actin associates with Pol II subunits through direct proteinprotein interactions and provides fundamental insight into Pol II transcriptional regulation.

Abstract. P-selectin plays a crucial role during hematogenous metastasis, and the blockade of P-selectin binding to its ligand can attenuate metastasis in various tumor models. Heparin or chemically modified heparins with decreased anticoagulant activities exhibit marked inhibitory effects on P-selectinmediated adhesion. Here, we prepared chemically modified heparins with reduced anticoagulant activities and investigated whether they effectively inhibited P-selectin binding to breast cancer cells under static and flow conditions. The results indicated that P-selectin binding to ZR-75-30 cells was attenuated by chemically modified heparins in a sulfationdependent manner under static and flow conditions. Flow cytometric analysis with heparan sulfate-specific monoclonal antibody revealed that heparan sulfate-like proteoglycans on the tumor cell surface were not implicated in this process. Instead, other glycoproteins were found to serve as P-selectin ligands. These findings suggest that further detailed research involving chemically modified heparins with low or no anticoagulant activities is warranted, and that chemically modified heparins should be considered in the treatment of metastatic breast cancer disease, with P-selectin potentially being a good target.