Leptomycin B stabilizes and activates p53 in primary prostatic epithelial cells and induces apoptosis in the LNCaP cell line.
BACKGROUND
Previous studies showed that primary cultures of normal and malignant human prostatic epithelial cells are defective in their ability to upregulate the tumor suppressor protein p53 in response to DNA damage. This dysfunctional regulation of p53 may be relevant to both the high incidence of prostate cancer and its resistance to chemotherapy. Leptomycin B (LMB) has recently been found to increase the protein level and transcriptional activity of p53 by interfering with nucleocytoplasmic export and subsequent degradation by the proteasome. We investigated the ability of LMB to activate p53 in prostatic epithelial cells.


METHODS
Primary cultures and the cell lines LNCaP and DU 145 were treated with LMB. p53 protein was evaluated in Western blots and by immunocytochemistry. Induction of downstream targets of p53 was evaluated in Western and Northern blots. Growth inhibition, cell cycle arrest, and apoptosis in response to LMB were measured in clonal growth assays, by flow cytometry, and by Hoescht/propidium iodide staining, respectively.


RESULTS
Treatment of prostatic epithelial cells with LMB led to post-translational stabilization of p53, activation of downstream target genes, and induction of cell cycle arrest in primary cultures and apoptosis in LNCaP (with wild-type p53) but not DU 145 (with mutant p53) cells.


CONCLUSIONS
p53 in primary cultures of normal and malignant prostate cells, although dysfunctional in that it is not responsive to DNA damage, is activated by LMB. The ability of LMB to stabilize p53 and induce expression of p53-responsive growth inhibitory genes may be a useful lead in the development of chemopreventive or therapeutic small molecules that can modulate p53 function in prostatic epithelial cells.
Lecane
Philip S
PS
Department of Urology, Stanford University School of Medicine, Stanford, California 94305, USA.
Kiviharju
Taija M
TM
Sellers
Robert G
RG
Peehl
Donna M
DM
D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000235:genetics; D002455:Cell Division / Q000187:drug effects; D002467:Cell Nucleus / Q000378:metabolism; D002999:Clone Cells; D050759:Cyclin-Dependent Kinase Inhibitor p21; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000235:genetics; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D008297:Male; D011467:Prostate / Q000166:cytology*; D011471:Prostatic Neoplasms; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics
D000903:Antibiotics, Antineoplastic; C493956:CDKN1A protein, human; D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D005231:Fatty Acids, Unsaturated; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C038753:leptomycin B