Down-regulation of the JAK2/PI3K-mediated signaling activation is involved in Taiwan cobra cardiotoxin III-induced apoptosis of human breast MDA-MB-231 cancer cells.
Cardiotoxin III (CTX III), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. Exposure of MDA-MB-231 cells with 0.03, 0.09, and 0.15 microM of CTX III for 18 h, CTX III-induced cell apoptosis, as evidenced by accumulation of sub-G1 population, externalization of phosphatidylserine, loss of mitochondrial membrane potential (DeltaPsim) with subsequent release of cytochrome c, and activation of both capases-9 and caspase-3. This correlated with up-regulation in Bax and Bad, and down-regulation of various anti-apoptotic proteins, including Bcl-2, Bcl-X(L), and survivin in CTX III-treated cells. Mechanistic studies showed that CTX III suppressed the phosphorylation of JAK2, STAT3, Akt, and activation of PI3K. Moreover, the PI3K inhibitor wortmannin blocked activation of STAT3 and Akt without affecting the JAK2 activation, whereas JAK2 inhibitor AG490 suppressed the levels of phospho-STAT3, phospho-Akt, and PI3K, suggesting that PI3K activation occurs after JAK2 phosphorylation, and both PI3K and JAK2 kinases cooperate to mediate STAT3 and Akt phosphorylation. Both AG490 and wortmannin also led to up-regulation in Bax and Bad, and down-regulation of Bcl-2, Bcl-X(L), and survivin in MDA-MB-231 cells. Taken together, these results indicate that CTX III induces apoptosis in MDA-MB-231 cells via concomitant inactivation of the JAK2, STAT3, PI3K, and Akt signaling pathways.
Lin
Kuei-Li
KL
Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan, ROC.
Su
Jung-Chen
JC
Chien
Ching-Ming
CM
Chuang
Pei-Wen
PW
Chang
Long-Sen
LS
Lin
Shinne-Ren
SR
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology; D020169:Caspases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004179:Cobra Cardiotoxin Proteins / Q000633:toxicity*; D045304:Cytochromes c / Q000737:chemistry / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D015536:Down-Regulation / Q000187:drug effects; D004546:Elapid Venoms / Q000633:toxicity*; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D019254:Genes, bcl-2 / Q000187:drug effects; D006801:Humans; D053614:Janus Kinase 2 / Q000096:biosynthesis* / Q000235:genetics; D051058:Oncogene Protein v-akt / Q000096:biosynthesis / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000096:biosynthesis* / Q000235:genetics; D010766:Phosphorylation; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013624:Taiwan
D004179:Cobra Cardiotoxin Proteins; D004546:Elapid Venoms; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C082202:cardiotoxin III, Naja naja atra; D045304:Cytochromes c; D019869:Phosphatidylinositol 3-Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2; D051058:Oncogene Protein v-akt; D020169:Caspases