title: Cystatin E/M Suppresses Tumor Cell Growth through Cytoplasmic Retention of NF-κB.
abstract: We and others have shown that the cystatin E/M gene is inactivated in primary human tumors, pointing to its role as a tumor suppressor gene. However, the molecular mechanism of tumor suppression is not yet understood. Using plasmid-directed cystatin E/M gene overexpression, a lentivirus-mediated tetracycline-inducible vector system, and human papillomavirus 16 (HPV 16) E6 and E7 gene-immortalized normal human epidermal keratinocytes, we demonstrated intracellular and non-cell-autonomous apoptotic growth inhibition of tumor cell lines and that growth inhibition is associated with cytoplasmic retention of NF-κB. We further demonstrated decreased phosphorylation of IκB kinase (IKKβ) and IκBα in the presence of tumor necrosis factor alpha (TNF-α), confirming the role of cystatin E/M in the regulation of the NF-κB signaling pathway. Growth suppression of nude mouse xenograft tumors carrying a tetracycline-inducible vector system was observed with the addition of doxycycline in drinking water, confirming that the cystatin E/M gene is a tumor suppressor gene. Finally, immunohistochemical analyses of cervical carcinoma in situ and primary tumors have shown a statistically significant inverse relationship between the expression of cystatin E/M and cathepsin L and a direct relationship between the loss of cystatin E/M expression and nuclear expression of NF-κB. We therefore propose that the cystatin E/M suppressor gene plays an important role in the regulation of NF-κB.
authors.affiliation: Division of General Surgery, Department of Surgery, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Hendrick
authors.initials: H
authors.lastname: Soh
authors.affiliation: Division of General Surgery, Department of Surgery, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Natarajan
authors.initials: N
authors.lastname: Venkatesan
authors.affiliation: Department of Medicine, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Mysore S
authors.initials: MS
authors.lastname: Veena
authors.affiliation: Division of General Surgery, Department of Surgery, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Sandhiya
authors.initials: S
authors.lastname: Ravichandran
authors.affiliation: Division of General Surgery, Department of Surgery, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Alborz
authors.initials: A
authors.lastname: Zinabadi
authors.affiliation: Department of Medicine, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Saroj K
authors.initials: SK
authors.lastname: Basak
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, UCLA, Los Angeles, California, USA.
authors.forename: Kislay
authors.initials: K
authors.lastname: Parvatiyar
authors.affiliation: Department of Anatomy, Physiology and Genetics and Institute of Molecular Medicine, Uniformed Services University of Health Services School of Medicine, Bethesda, Maryland, USA.
authors.forename: Meera
authors.initials: M
authors.lastname: Srivastava
authors.affiliation: Department of Medicine, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Li-Jung
authors.initials: LJ
authors.lastname: Liang
authors.affiliation: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Gjertson
authors.affiliation: Department of Chemistry and Biochemistry, UCLA, Los Angeles, California, USA.
authors.forename: Jorge Z
authors.initials: JZ
authors.lastname: Torres
authors.affiliation: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
authors.forename: Neda A
authors.initials: NA
authors.lastname: Moatamed
authors.affiliation: Division of General Surgery, Department of Surgery, VAGLAHS/David Geffen School of Medicine at UCLA, Los Angeles, California, USA Jonsson Comprehensive Cancer Center, UCLA, Los Angeles, California, USA esrivats@g.ucla.edu.
authors.forename: Eri S
authors.initials: ES
authors.lastname: Srivatsan
mesh_terms: D000818:Animals; D056668:Cathepsin L / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D055332:Cystatin M / Q000235:genetics / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism*; D004318:Doxycycline / Q000008:administration & dosage; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005822:Genetic Vectors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism*; D016086:Lentivirus / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D016328:NF-kappa B / Q000378:metabolism*; D009368:Neoplasm Transplantation; D010766:Phosphorylation; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D002583:Uterine Cervical Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*
chemical_list: C525104:CST6 protein, human; D055332:Cystatin M; D020672:I-kappa B Proteins; D016328:NF-kappa B; C439524:TNF protein, human; D014409:Tumor Necrosis Factor-alpha; C534281:CTSL protein, human; D056668:Cathepsin L; D004318:Doxycycline