Overexpression of IL-6 but not IL-8 increases paclitaxel resistance of U-2OS human osteosarcoma cells

Cytokine. 2002 Mar 7;17(5):234-42. doi: 10.1006/cyto.2001.1008.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / biosynthesis
  • Antineoplastic Agents / pharmacology
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Blotting, Northern
  • Blotting, Western
  • Caspase 3
  • Caspases / biosynthesis
  • Cell Division
  • DNA, Complementary / metabolism
  • Dose-Response Relationship, Drug
  • Drug Resistance, Neoplasm*
  • Enzyme Activation
  • Enzyme-Linked Immunosorbent Assay
  • Genetic Vectors
  • Humans
  • Interleukin-6 / biosynthesis*
  • Interleukin-8 / biosynthesis*
  • Mitoxantrone / pharmacology
  • Osteosarcoma / drug therapy
  • Paclitaxel / pharmacology*
  • Phenotype
  • RNA / metabolism
  • Tetrazolium Salts / pharmacology
  • Thiazoles / pharmacology
  • Time Factors
  • Topotecan / pharmacology
  • Transfection
  • Tumor Cells, Cultured


  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antineoplastic Agents
  • Antineoplastic Agents, Phytogenic
  • DNA, Complementary
  • Interleukin-6
  • Interleukin-8
  • Tetrazolium Salts
  • Thiazoles
  • RNA
  • Topotecan
  • Mitoxantrone
  • CASP3 protein, human
  • Caspase 3
  • Caspases
  • thiazolyl blue
  • Paclitaxel