Abstract
Constitutive activation of the Hedgehog (Hh) signaling pathway has been implicated in the development of many human malignancies. Hh targets, such as Patched (PTCH), smoothened (SMO), Sonic hedgehog (SHH) and glioma-associated oncogene homologue 1 (GLI1), are markers of Hh signaling activation and expressed in most Hh-associated tumors. The protein kinase LKB1 has been shown to slow proliferation and induce cell-cycle arrest in many cell lines. In this study, we observed that activated LKB1 decreased the expression of factors related to Hh reporter activity in MDA-MB-231 breast cancer cells, including of SMO, SHH and GLI1. In contrast, LKB1 siRNA increased the expression of these target genes. The same results were shown to inhibit the Hh factors Sufu and Hip. Furthermore, we also observed negative correlation between LKB1 and glioma-associated oncogene homologue 1 (GLI1) in three breast cancer cell lines. Meanwhile, LKB1 siRNA rescued the inhibition of cell growth by 3-Keto-N-(aminoethyl-N'-aminocaproyldihydrocinnamoyl) cyclopamine (KAAD-cyclopamine), an antagonist of the Hh element SMO, which suggests that LKB1 acts as the downstream of SMO. In vivo, LKB1 siRNA increased tumor growth in the mammary fat pad, and the expression levels of Hh displayed similar results in vitro. Overexpression of the LKB1 protein in human breast cancers is associated with the expression of Hh. We found that breast carcinomas with detectable Hh had weak or undetectable expression of LKB1, whereas tumors that expressed high levels of LKB1 had undetectable Hh signaling. In this study, we find that LKB1 are negatively correlated with the expression of Hh related transcription factors. These findings suggest that LKB1 may inhibit tumorigenesis by regulating Hh signaling in certain cancers.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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AMP-Activated Protein Kinase Kinases
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Adult
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Aged
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Animals
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Breast Neoplasms / genetics*
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Breast Neoplasms / metabolism
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Breast Neoplasms / pathology
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Carcinoma, Ductal, Breast / genetics*
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Carcinoma, Ductal, Breast / metabolism
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Carcinoma, Ductal, Breast / pathology
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Cell Line, Tumor
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Cell Proliferation / drug effects
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Cinnamates / pharmacology
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Female
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Gene Expression Regulation, Neoplastic*
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Hedgehog Proteins / genetics*
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Hedgehog Proteins / metabolism
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Humans
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Mice, Nude
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Middle Aged
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Neoplasms, Experimental / genetics
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Neoplasms, Experimental / metabolism
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Neoplasms, Experimental / pathology
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Patched Receptors
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Patched-1 Receptor
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Protein Serine-Threonine Kinases / antagonists & inhibitors
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Protein Serine-Threonine Kinases / genetics*
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Protein Serine-Threonine Kinases / metabolism
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RNA, Small Interfering / genetics
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RNA, Small Interfering / metabolism
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism
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Receptors, G-Protein-Coupled / genetics
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Receptors, G-Protein-Coupled / metabolism
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Signal Transduction
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Smoothened Receptor
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Transcription Factors / genetics
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Transcription Factors / metabolism
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Veratrum Alkaloids / pharmacology
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Zinc Finger Protein GLI1
Substances
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3-keto-N-aminoethylaminoethylcaproyldihydrocinnamoyl cyclopamine
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Cinnamates
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GLI1 protein, human
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Hedgehog Proteins
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PTCH1 protein, human
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Patched Receptors
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Patched-1 Receptor
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Ptch1 protein, mouse
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RNA, Small Interfering
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Receptors, Cell Surface
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Receptors, G-Protein-Coupled
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SHH protein, human
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SMO protein, human
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Smoothened Receptor
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Transcription Factors
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Veratrum Alkaloids
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Zinc Finger Protein GLI1
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Protein Serine-Threonine Kinases
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STK11 protein, human
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AMP-Activated Protein Kinase Kinases
Grants and funding
This study was supported by Shanghai Science and Technology Committee (grants 09zr1424800 and 124119a4700). Shanghai Health Bureau scientific research subject (20124164). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.