Peptidyl prolyl isomerase, Pin1 is a potential target for enhancing the therapeutic efficacy of etoposide.
The peptidyl prolyl isomerase (Pin1) that induces cis-trans isomerization of the peptide bond involving serine/threonine-proline has recently been shown to regulate the activity of many phosphoproteins including the ones involved in damage response pathways. We investigated Pin1 as a potential target for enhancing the efficacy of anticancer therapy by studying the effects of juglone, a Pin1 inhibitor on the cytotoxicity of etoposide (a widely used anticancer drug that targets topoisomerase IIα) in human tumor cell lines. Treatment of cells with juglone synergistically enhanced the cytotoxicity of etoposide (loss of clonogenicity) with a tenfold increase when etoposide treatment preceded juglone exposure. On the other hand, the toxicity was than additive when the treatment protocol was reversed (i.e exposure to juglone followed by etoposide treatment). This suggests that Pin1 inhibition possibly reduces the induction of initial DNA damage by etoposide, which was supported by a decrease in the levels of chromatin bound topoIIα. Increase in the etoposide induced toxicity by juglone appeared to be mainly due to enhanced mitotic cell death linked to cytogenetic damage, although a moderate increase in interphase (apoptotic) death was also evident as revealed by DNA degradation (hypodiploid population and TUNEL assay). Since the level of Pin1 is found to be higher in cancer cells, this enzyme could be a potential target for developing an adjuvant to enhance the efficacy of anticancer therapies.
Institute of Nuclear Medicine and Allied Sciences, Brig. S. K. Mazumdar Marg, Delhi 110054, India.
R
R
Mathur
S
S
Chandna
P
P
N Kapoor
B
B
S Dwarakanath
D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects*; D004249:DNA Damage / Q000187:drug effects; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy*; D015162:Micronucleus Tests; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D009285:Naphthoquinones / Q000494:pharmacology*; D019696:Peptidylprolyl Isomerase / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay
D000972:Antineoplastic Agents, Phytogenic; D004791:Enzyme Inhibitors; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D009285:Naphthoquinones; D005047:Etoposide; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase; C005134:juglone