Enhanced antitumor therapy by inhibition of p21waf1 in human malignant mesothelioma.
OBJECTIVE
The p21 cyclin-dependent kinase inhibitor was frequently expressed in human malignant pleural mesothelioma (MPM) tissues as well as cell lines. Recent data indicate that p21 keeps tumor cells alive after DNA damage, favoring a survival advantage. In this study, we assessed the possibility of p21 suppression as a therapeutic target for MPM.


METHODS
We established two different MPM-derived (from H28 and H2052 cells) subclones using vector-based short hairpin RNA (shRNA). Then, chemosensitivity against low doses of antineoplastic DNA-damaging agents was investigated by colony formation assays, and furthermore, the type of cell response induced by these drugs was analyzed. To examine the effect of p21 shRNA on chemosensitivity in vivo, tumor formation assays in nude mice were done.


RESULTS
In colony formation assay, the IC50 of doxorubicin was 33 +/- 3.0 nmol/L in p21 shRNA-transfected cells with respect to 125 +/- 10 nmol/L of control vector-transfected cells. This enhancement of growth inhibition was achieved by converting a senescence-like growth arrest to apoptosis in response to doxorubicin, etoposide, and CPT11. In the in vivo assays, CPT11 and loss-of-expression of p21 in combination led to considerable suppression of tumor growth associated with a substantially enhanced apoptotic response, whereas CPT11 alone was ineffective at inducing these responses.


CONCLUSIONS
These results indicated that p21 might play an important role in chemosensitivity to anticancer agents, and the suppression of its expression might be a potential therapeutic target for MPM.
Lazzarini
Raffaella
R
Department of Molecular Pathology and Innovative Therapies, Marche University, Ancona, Italy.
Moretti
Simona
S
Orecchia
Sara
S
Betta
Pier-Giacomo
PG
Procopio
Antonio
A
Catalano
Alfonso
A
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D002166:Camptothecin / Q000031:analogs & derivatives / Q000494:pharmacology; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D016922:Cellular Senescence / Q000187:drug effects / Q000502:physiology; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000187:drug effects* / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000502:physiology*; D005047:Etoposide / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D000077146:Irinotecan; D008297:Male; D008654:Mesothelioma / Q000378:metabolism*; D051379:Mice; D008819:Mice, Nude; D034622:RNA Interference; D014162:Transfection; D023041:Xenograft Model Antitumor Assays
D000970:Antineoplastic Agents; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005047:Etoposide; D000077146:Irinotecan; D004317:Doxorubicin; D002166:Camptothecin