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: Hendrick Soh, Natarajan Venkatesan, Mysore S Veena, Sandhiya Ravichandran, Alborz Zinabadi, Saroj K Basak, Kislay Parvatiyar, Meera Srivastava, Li-Jung Liang, David W Gjertson, Jorge Z Torres, Neda A Moatamed, Eri S Srivatsan
• Journal: Molecular and cellular biology (Mol Cell Biol) Vol. 36 Issue 12 Pg. 1776-92 (06 15 2016) ISSN: 1098-5549 [Electronic] United States
• PMID: 27090639 (Publication Type: Journal Article)
• Copyright: Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Chemical References

• CST6 protein, human
• Cystatin M
• I-kappa B Proteins
• NF-kappa B
• TNF protein, human
• Tumor Necrosis Factor-alpha
• CTSL protein, human
• Cathepsin L
• Doxycycline

Topics

• Animals
• Cathepsin L (metabolism)
• Cell Line, Tumor
• Cell Proliferation
• Cystatin M (genetics, metabolism)
• Cytoplasm (metabolism)
• Doxycycline (administration & dosage)
• Female
• Gene Expression Regulation, Neoplastic
• Genetic Vectors (pharmacology)
• HeLa Cells
• Humans
• I-kappa B Proteins (metabolism)
• Lentivirus (genetics)
• Mice
• Mice, Nude
• NF-kappa B (metabolism)
• Neoplasm Transplantation
• Phosphorylation
• Signal Transduction
• Tumor Necrosis Factor-alpha (metabolism)
• Uterine Cervical Neoplasms (genetics, metabolism, pathology)