title: New pyrazolo[3,4-d]pyrimidine SRC inhibitors induce apoptosis in mesothelioma cell lines through p27 nuclear stabilization.
abstract: Malignant mesothelioma (MM) is a highly aggressive tumor of the serous membranes for which there is currently no effective curative modality. Recent data suggest that hyperactivation of the tyrosine kinase SRC has a key role in MM development and therefore this kinase represents an important molecular target for MM therapy. We tested new pyrazolo[3,4-d]pyrimidine SRC inhibitors on a panel of MM cell lines expressing the active form of SRC. These SRC inhibitors exerted a significant proapoptotic effect on MM cells without affecting the normal mesothelial cell line MET-5A, supporting a possible use of these SRC inhibitors for a safe treatment of MM. We also showed that SRC inhibitor-induced apoptosis occurred concomitantly with an increase in the nuclear stability of the cyclin-dependent kinase inhibitor p27. This finding is remarkable considering that loss of nuclear p27 expression is a well-established adverse prognostic factor in MM, and p27 nuclear localization is crucial for its tumor-suppressive function. Consistently, SRC inhibition seems to promote the increase in p27 nuclear level also by inactivating the AKT kinase and downregulating cyclin D1, which would otherwise delay p27 nuclear import and provoke its cytoplasmic accumulation. To determine whether p27 stabilization has a direct role in apoptosis induced by SRC inhibition, we stably silenced the CDKN1B gene, encoding p27, in MSTO-211H and REN mesothelioma cells by transduction with lentiviral vectors expressing short hairpin RNAs against the CDKN1B transcript. Strikingly, p27 silencing was able to suppress the apoptosis induced by these SRC inhibitors in both MM cell lines, suggesting that p27 has a crucial proapoptotic role in MM cells treated with SRC inhibitors. Our findings reveal a new mechanism, dependent on p27 nuclear stabilization, by which SRC inhibition can induce apoptosis in MM cells and provide a new rationale for the use of SRC inhibitors in MM therapy.
authors.affiliation: Department of Human Pathology and Oncology, University of Siena, Siena, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Indovina
authors.forename: F
authors.initials: F
authors.lastname: Giorgi
authors.forename: V
authors.initials: V
authors.lastname: Rizzo
authors.forename: B
authors.initials: B
authors.lastname: Khadang
authors.forename: S
authors.initials: S
authors.lastname: Schenone
authors.forename: D
authors.initials: D
authors.lastname: Di Marzo
authors.forename: I M
authors.initials: IM
authors.lastname: Forte
authors.forename: V
authors.initials: V
authors.lastname: Tomei
authors.forename: E
authors.initials: E
authors.lastname: Mattioli
authors.forename: V
authors.initials: V
authors.lastname: D'Urso
authors.forename: B
authors.initials: B
authors.lastname: Grilli
authors.forename: M
authors.initials: M
authors.lastname: Botta
authors.forename: A
authors.initials: A
authors.lastname: Giordano
authors.forename: F
authors.initials: F
authors.lastname: Pentimalli
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D019938:Cyclin D1 / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004795:Enzyme Stability / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D008654:Mesothelioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D015394:Molecular Structure; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011720:Pyrazoles / Q000737:chemistry / Q000494:pharmacology*; D011743:Pyrimidines / Q000737:chemistry / Q000494:pharmacology*; D034622:RNA Interference; D019061:src-Family Kinases / Q000037:antagonists & inhibitors*
chemical_list: D000970:Antineoplastic Agents; D011720:Pyrazoles; D011743:Pyrimidines; D019938:Cyclin D1; D050760:Cyclin-Dependent Kinase Inhibitor p27; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt