title: Overexpression of IL-6 but not IL-8 increases paclitaxel resistance of U-2OS human osteosarcoma cells.
abstract: The cytokines IL-6, initially recognized as a regulator of immune and inflammatory response and IL-8, a potential regulator of angiogenesis, also regulate the growth of many tumor cells. Human cancer cells selected for multidrug resistance to common chemotherapeutic agents demonstrate increased expression of IL-6 and IL-8. To determine whether IL-6 or IL-8 overexpression contributes directly to the drug resistant phenotype, IL-6 or IL-8 cDNA were introduced into the paclitaxel sensitive human osteosarcoma cell line U-2OS using the pIRESneo bicistronic expression vector. Interleukin-6 and IL-8 transfectants were selected for either high IL-6 or IL-8 secretion and evaluated in drug resistance assays. Two IL-6 and two IL-8 secreting clones express IL-6 or IL-8 levels of 10 ng/ml and 1 ng/ml in culture, while parental U-2OS and pIRESneo vector transfected control cells express IL-6 and IL-8 levels of 0.005 ng/ml and 0.1 ng/ml, respectively. MTT cytotoxicity with IL-6 transfected cells demonstrates a five-fold increase in resistance to paclitaxel and a four-fold increase in resistance to doxorubicin as compared to U-2OS. There are no changes in mitoxantrone or topotecan resistance in the IL-6 transfectants as compared to parental U-2OS. Northern analysis of IL-6 transfectants demonstrates that the resistant phenotype is not related to increased levels of MDR-1, MRP-1, or LRP. Western analysis also confirms that P-glycoprotein levels are not altered in IL-6 transfectants. Further supporting an MDR-1 independent mechanism of drug resistance, verapamil cannot reverse paclitaxel resistance in transfected cells, findings further supported by rhodamine 123 exclusion data. Treatment of IL-6 transfected cells with paclitaxel, compared with drug-sensitive parental U-2OS, shows U-2OS(IL-6) are significantly more resistant to apoptosis induced by paclitaxel and exhibit decreased proteolytic activation of caspase-3. In contrast U-2OS(IL-8) transfectants demonstrate no appreciable increase in paclitaxel resistance when compared with parental cells. In summary, while both IL-6 and IL-8 are overexpressed in paclitaxel resistant cell lines, only IL-6 has the potential to contribute directly to paclitaxel and doxorubicin resistance in U-2OS. This resistance is through a non-MDR-1 pathway.
authors.affiliation: Department of Hematology/Oncology, Massachusetts General Hospital, Boston, MA 02114, USA.
authors.forename: Z
authors.initials: Z
authors.lastname: Duan
authors.forename: D E
authors.initials: DE
authors.lastname: Lamendola
authors.forename: R T
authors.initials: RT
authors.lastname: Penson
authors.forename: K M
authors.initials: KM
authors.lastname: Kronish
authors.forename: M V
authors.initials: MV
authors.lastname: Seiden
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis; D000970:Antineoplastic Agents / Q000494:pharmacology; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D015152:Blotting, Northern; D015153:Blotting, Western; D053148:Caspase 3; D020169:Caspases / Q000096:biosynthesis; D002455:Cell Division; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D005822:Genetic Vectors; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis*; D016209:Interleukin-8 / Q000096:biosynthesis*; D008942:Mitoxantrone / Q000494:pharmacology; D012516:Osteosarcoma / Q000188:drug therapy; D017239:Paclitaxel / Q000494:pharmacology*; D010641:Phenotype; D012313:RNA / Q000378:metabolism; D013778:Tetrazolium Salts / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D013997:Time Factors; D019772:Topotecan / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D000972:Antineoplastic Agents, Phytogenic; D018076:DNA, Complementary; D015850:Interleukin-6; D016209:Interleukin-8; D013778:Tetrazolium Salts; D013844:Thiazoles; D012313:RNA; D019772:Topotecan; D008942:Mitoxantrone; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; C022616:thiazolyl blue; D017239:Paclitaxel