Bee venom secretory phospholipase A2 and phosphatidylinositol-homologues cooperatively disrupt membrane integrity, abrogate signal transduction and inhibit proliferation of renal cancer cells.
Bee venom secretory phospholipase A2 (bv-sPLA2) and phosphatidylinositol-(3,4)-bisphosphate (PtdIns(3,4)P2) act synergistically to induce cell death in tumour cells of various origins with concomitant stimulation of the immune system. Here, we investigated the mechanisms involved in such actions and examined structural requirements of PtdIns-homologues to inhibit tumour cells in combination with bv-sPLA2. Renal cancer cells were treated with bv-sPLA2 alone or in combination with PtdIns-homologues. Inhibitory effects on [(3)H] thymidine incorporation and intracellular signal transduction pathways were tested. Reaction products generated by bv-sPLA2 interaction with PtdIns(3,4)P2 were identified by mass spectrometry. Among the tested PtdIns-homologues those with a phosphate esterified to position 3 of the inositol head group, were most efficient in cooperating with bv-sPLA2 to block tumour cell proliferation. Growth inhibition induced by the combined action of bv-sPLA2 with either PtdIns(3,4)bisphosphate or PtdIns(3,4,5)trisphosphate were synergistic and accompanied by potent cell lysis. In contrast, PtdIns, which lacked the phosphate group at position 3, failed to promote synergistic growth inhibition. The combined administration of PtdIns(3,4)P2 and bv-sPLA2 abrogated signal transduction mediated by extracellular signal regulated kinase 1 and 2 and prevented transduction of survival signals mediated by protein kinase B. Surface expression of the epidermal growth factor (EGF)-receptor was reduced after PtdIns(3,4)P2-bv-sPLA2 administration and associated with a blockade of EGF-induced signalling. In addition, mass spectroscopy revealed that bv-sPLA2 cleaves PtdIns(3,4)P2 to generate lyso-PtdIns(3,4)P2. In conclusion, we suggest that the cytotoxic activity mediated by PtdIns(3,4)P2 and bv-sPLA2 is due to cell death that results from disruption of membrane integrity, abrogation of signal transduction and the generation of cytotoxic lyso-PtdIns(3,4)P2.
Putz
Thomas
T
Department of Urology and kompetenzzentrum medizin tirol, Innsbruck Medical University, Innsbruck, Austria. thomas.putz@uklibk.ac.at
Ramoner
Reinhold
R
Gander
Hubert
H
Rahm
Andrea
A
Bartsch
Georg
G
Bernardo
Katussevani
K
Ramsay
Steven
S
Thurnher
Martin
M
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001514:Bee Venoms / Q000737:chemistry*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004357:Drug Synergism; D004789:Enzyme Activation / Q000187:drug effects; D066246:ErbB Receptors / Q000096:biosynthesis / Q000187:drug effects; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects; D054501:Group II Phospholipases A2; D006801:Humans; D007680:Kidney Neoplasms / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000737:chemistry / Q000494:pharmacology*; D010741:Phospholipases A / Q000494:pharmacology*; D054467:Phospholipases A2; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects
D000970:Antineoplastic Agents; D001514:Bee Venoms; D010716:Phosphatidylinositols; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2