title: Inhibition of constitutive STAT3 activity sensitizes resistant non-Hodgkin's lymphoma and multiple myeloma to chemotherapeutic drug-mediated apoptosis.
abstract: Hematopoietic malignancies have been shown to depend on cytokine growth factor autocrine/paracrine loops for growth and differentiation. This results in the constitutive activation of cytokine-mediated transcription factors like signal transducer and activators of transcription (STAT) 3 in non-Hodgkin's lymphoma (NHL) and multiple myeloma (MM). Recent evidence demonstrates that cytokines also contribute to a drug-resistant phenotype in many tumor cell types. We hypothesized that inhibitors of the STAT3 pathway would sensitize drug-resistant and endogenous cytokine-dependent NHL and MM tumor cells to the cytotoxic effects of chemotherapeutic drugs. We examined an AIDS-related NHL cell line, 2F7, known to be dependent on interleukin (IL)-10 for survival and an MM cell line, U266, known to be dependent on IL-6 for survival. IL-10 and IL-6 signal the cells through the activation of Janus kinase (JAK)1 and JAK2, respectively. Thus, we investigated the effect of two chemical STAT3 pathway inhibitors, namely, piceatannol (JAK1/STAT3 inhibitor) and tyrphostin AG490 (JAK2/STAT3 inhibitor), on the tumor cells for sensitization to therapeutic drugs. We demonstrate by phosphoprotein immunoblotting analysis and electrophoretic mobility shift analysis that piceatannol and AG490 inhibit the constitutive activity of STAT3 in 2F7 and U266, respectively. Furthermore, piceatannol and AG490 sensitize 2F7 and U266 cells, respectively, to apoptosis by a range of therapeutic drugs including cisplatin, fludarabine, Adriamycin, and vinblastine. The specificity of the inhibitors was corroborated in experiments showing that piceatannol had no effect on U266 and, likewise, AG490 has no effect on 2F7. The sensitization observed by these inhibitors correlated with the inhibition of Bcl-2 expression in 2F7 and Bcl-xL expression in U266. Altogether, these results demonstrate that STAT3 pathway inhibitors are a novel class of chemotherapeutic sensitizing agents capable of reversing the drug-resistant phenotype of cytokine-dependent tumor cells.
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles School of Medicine, University of California, Los Angeles, California 90095, USA.
authors.forename: Steve
authors.initials: S
authors.lastname: Alas
authors.forename: Benjamin
authors.initials: B
authors.lastname: Bonavida
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism; D016207:Cytokines / Q000378:metabolism; D053938:DNA Fragmentation; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors*; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation; D004317:Doxorubicin / Q000494:pharmacology; D006801:Humans; D015151:Immunoblotting; D016753:Interleukin-10 / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D053613:Janus Kinase 1; D053614:Janus Kinase 2; D008228:Lymphoma, Non-Hodgkin / Q000378:metabolism*; D008954:Models, Biological; D009101:Multiple Myeloma / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D050796:STAT3 Transcription Factor; D013267:Stilbenes / Q000494:pharmacology; D013997:Time Factors; D015534:Trans-Activators / Q000037:antagonists & inhibitors*; D014407:Tumor Cells, Cultured; D020032:Tyrphostins / Q000494:pharmacology; D014747:Vinblastine / Q000494:pharmacology; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein
chemical_list: D000970:Antineoplastic Agents; C494819:BAD protein, human; C494811:BCL2L1 protein, human; D002352:Carrier Proteins; D016207:Cytokines; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D013267:Stilbenes; D015534:Trans-Activators; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; D051020:bcl-X Protein; D016753:Interleukin-10; D014747:Vinblastine; C041525:3,3',4,5'-tetrahydroxystilbene; D004317:Doxorubicin; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; C507924:JAK2 protein, human; D053613:Janus Kinase 1; D053614:Janus Kinase 2