title: Betulinic acid suppresses STAT3 activation pathway through induction of protein tyrosine phosphatase SHP-1 in human multiple myeloma cells.
abstract: STAT3 activation has been associated with survival, proliferation and invasion of various human cancers. Whether betulinic acid, a pentacyclic triterpene, can modulate the STAT3 pathway, was investigated in human multiple myeloma (MM) cells. We found that betulinic acid inhibited constitutive activation of STAT3, Src kinase, JAK1 and JAK2. Pervanadate reversed the betulinic acid-induced downregulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase (PTP). Furthermore, betulinic acid induced the expression of the PTP SHP-1 and silencing of the SHP-1 gene abolished the ability of betulinic acid to inhibit STAT3 activation and rescued betulinic acid-induced cell death. Betulinic acid also downregulated the expression of STAT3-regulated gene products such as bcl-xL, bcl-2, cyclin D1 and survivin. This correlated with an increase in apoptosis as indicated by an increase in the sub-G1 cell population and an increase in caspase-3-induced PARP cleavage. Consistent with these results, overexpression of constitutive active STAT3 significantly reduced the betulinic acid-induced apoptosis. Betulinic acid also enhanced the apoptosis induced by thalidomide (from 10 to 55%) and bortezomib (from 5 to 70%) in MM cells. Overall, our results suggest that betulinic acid downregulates STAT3 activation through upregulation of SHP-1, and this may have potential in sensitization of STAT3 overexpressing tumors to chemotherapeutic agents.
authors: Department of Experimental Therapeutics, The University of Texas M. D. Anderson Cancer Center, Houston, TX, USA.
authors: Manoj K
authors: MK
authors: Pandey
authors: Bokyung
authors: B
authors: Sung
authors: Bharat B
authors: BB
authors: Aggarwal
mesh_terms: D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D049109:Cell Proliferation / Q000187:drug effects; D004359:Drug Therapy, Combination; D024202:Electrophoretic Mobility Shift Assay; D004789:Enzyme Activation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007124:Immunoenzyme Techniques; D007166:Immunosuppressive Agents / Q000494:pharmacology; D015850:Interleukin-6 / Q000494:pharmacology; D053613:Janus Kinase 1 / Q000378:metabolism; D053614:Janus Kinase 2 / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D053978:Pentacyclic Triterpenes; D011480:Protease Inhibitors / Q000494:pharmacology; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000235:genetics / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013792:Thalidomide / Q000494:pharmacology; D014315:Triterpenes / Q000494:pharmacology*; D014407:Tumor Cells, Cultured; D019061:src-Family Kinases / Q000378:metabolism; D000094062:Betulinic Acid
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D001897:Boronic Acids; D007166:Immunosuppressive Agents; D015850:Interleukin-6; D053978:Pentacyclic Triterpenes; D011480:Protease Inhibitors; D011719:Pyrazines; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D014315:Triterpenes; D013792:Thalidomide; D000069286:Bortezomib; D008156:Luciferases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D019061:src-Family Kinases; C509249:PTPN6 protein, human; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D000094062:Betulinic Acid