Hudan Liu

Aberrant activation of Wnt signaling pathway is crucial for the onset and progression of human colorectal cancer (CRC). Owing to the persistent dependence on Wnt signaling for growth and survival, inhibition of this pathway is an attractive approach for new therapies. 11α, 12α-epoxyleukamenin E (EPLE) is a novel ent-kaurane diterpenoid that we previously isolated from Salvia cavaleriei, exhibiting antitumor activities in a variety of cancer cells. Herein, we found that whereas sparing normal human colon mucosal epithelial cells, EPLE selectively inhibited the proliferation of CRC cell lines as well as primary tumor cells. Mechanistically, we demonstrated EPLE exerted its function through suppressing Wnt signaling pathway, as evidenced by EPLE-mediated downregulation of Wnt target genes such as c-Myc, Axin2 and Survivin. Consistently, luciferase reporter assays showed that the EPLE directly blocked Wnt/β-catenin–mediated transcriptional activation. In combination of co-immunoprecipitation and protein structure-based analyses, we determined that the EPLE entered the interface of β-catenin/TCF4 complexes and blocked their interaction that is required for β-catenin–mediated transcriptional activation. Moreover, overexpression of β-catenin alleviated the cytotoxicity of EPLE in CRC cells, supporting Wnt signaling is a major and specific target of EPLE. Combined treatments of EPLE and 5-fluorouracil, the first-line chemotherapy for CRC patients, achieved a synergistic effect. More importantly, EPLE hampered tumor development in a CRC xenograft model. Our data thus establish EPLE as a novel inhibitor of Wnt signaling that holds great promise as a potential candidate for further preclinical evaluation for CRC treatments.

Kruppel-like factor 4 (KLF4) induces tumorigenesis or suppresses tumor growth in a tissue-dependent manner. However, the roles of KLF4 in hematological malignancies and the mechanisms of action are not fully understood. Inducible KLF4-overexpression Jurkat cell line combined with mouse models bearing cell-derived xenografts and primary T-cell acute lymphoblastic leukemia (T-ALL) cells from four patients were used to assess the functional role of KLF4 in T-ALL cells in vitro and in vivo. A genome-wide RNA-seq analysis was conducted to identify genes regulated by KLF4 in T-ALL cells. Chromatin immunoprecipitation (ChIP) PCR was used to determine direct binding sites of KLF4 in T-ALL cells. Here we reveal that KLF4 induced apoptosis through the BCL2/BCLXL pathway in human T-ALL cell lines and primary T-ALL specimens. In consistence, mice engrafted with KLF4-overexpressing T-ALL cells exhibited prolonged survival. Interestingly, the KLF4-induced apoptosis in T-ALL cells was compromised in xenografts but the invasion capacity of KLF4-expressing T-ALL cells to hosts was dramatically dampened. We found that KLF4 overexpression inhibited T cell-associated genes including NOTCH1, BCL11B, GATA3, and TCF7. Further mechanistic studies revealed that KLF4 directly bound to the promoters of NOTCH1, BCL2, and CXCR4 and suppressed their expression. Additionally, KLF4 induced SUMOylation and degradation of BCL11B. These results suggest that KLF4 as a major transcription factor that suppresses the expression of T-cell associated genes, thus inhibiting T-ALL progression.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive and lethal disease with a high rate of metastasis. Numerous signaling events have been implicated in the molecular pathogenesis of this neoplasm. Aberrantly high expression of JAGGED2, one of the NOTCH ligands, often occurs in human PDAC. However, what role JAGGED2 plays in the disease development and whether JAGGED2 executes its function through activating NOTCH signaling remain to be determined. We report here that JAGGED2 plays a critical role in promoting PDAC metastasis in vitro and in vivo. Depletion of JAGGED2, but not its homolog JAGGED1, profoundly inhibited both migration and invasion without influencing cell proliferation. Furthermore, reconstitution of JAGGED2 expression rescued the migratory defect. Surprisingly, neither pharmacologic nor genetic inhibition of NOTCH downstream signaling resulted in obvious defect in metastasis. Instead, depletion of NOTCH1 expression per se gave rise to migratory defects similar to JAGGED2 ablation. Moreover, blockade of ligand–receptor interaction by a specific JAGGED2-Fc fusion protein dramatically inhibited PDAC cell migration, suggesting that tumor metastasis relies on physical interactions of JAGGED2-NOTCH1 but not Notch downstream signaling activation. Taken together, our data reveal a novel role of NOTCH in regulation of PDAC metastasis, and identify JAGGED2 as a critical mediator in this event. These findings also provide rationale for developing small molecules or biologic agents targeting JAGGED2 for therapeutic intervention. Mol Cancer Ther; 14(1); 289–97. ©2014 AACR.

Protein was found in E.coli which can specifically bind to NF-IL6 mRNA 3'UTR. After a series of purification steps, the RNA-specific binding protein was directly sequenced on the Porton LF3200 Protein Sequencer. A sequence of 10 amino acids of the purified NF-IL6 3'UTR binding protein was obtained, namely, Ala-Thr-Arg-Ile-Glu-Phe-His-Gly-Cyss(?)-Gly. A BLAST search with the 10 amino acids against NCBI database failed to identify any protein with identical sequence. The significance of identifying an eukaryotic mRNA binding protein in E.coli is discussed.