Key words: cytokine; IL-8; protein arrays; breast cancer; estrogen receptor; tumor progressionCytokines, cell communication mediators, play important roles in a wide range of physiological processes, such as cell growth, differentiation, apoptosis, wound healing and homeostasis. 1 A wealth of evidences suggests that cytokines, growth factors, chemokines, angiogenic factors and proteases are involved in cancer progression. 2-5 A number of autocrine and paracrine cytokine loops influence tumor development. 6 -9 Cytokines not only provide defense against cancer cells, but also promote cancer cell growth at every stage of cancer development. 10 Alteration of cytokine levels is associated with cancer progression, 11,12 response to chemotherapy 13,14 and metastatic status. 15,16 Therefore, determination of these factors in human breast cancer cells will shed light on the development of human breast cancer, identify new molecular targets for developing effective agents against breast cancer, discover biomarkers to aid in diagnosis and to predict clinical outcome, and eventually provide guideline for individual therapy. Furthermore, despite recent improvements in curing breast cancer patients, breast cancer still remains a serious threat to women's lives. Therefore, it is imperative to identify new targets for the development of effective treatment strategy. Because of the limitation of technology, however, previous studies only measured single or few cytokines at once. This greatly limits our understanding of the roles of those factors in breast cancer and the potential application in clinical diagnosis and prediction of clinical outcome.We recently developed several novel cytokine antibody array systems, which allow investigators to detect multiple cytokine expression levels simultaneously with high specificity and sensitivity. [17][18][19][20] By using human cytokine antibody array technology, we have begun to analyze differential cytokine expression levels in various human cancers, including human breast cancer, with the goal to identify key factor(s) involved in human breast cancer progression. Human cytokine antibody arrays indicate that expression of IL-8 is linked to ER status, metastasis status and vimentin status. Tumor biology experiments suggest that IL-8 is involved in breast cancer cell invasion and angiogenesis. Furthermore, ER␣ directly downregulates IL-8 expression. Our results suggest a potential new pathway involved in ER␣ inaction and upregulation of IL-8, leading to the invasiveness and angiogenesis of human breast cancer.

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Drug resistance remains a major hurdle to successful cancer treatment. Many mechanisms such as overexpression of multidrug-resistance related proteins, increased drug metabolism, decreased apoptosis, and impairment of signal transduction pathway can contribute multidrug resistance (MDR). Recent studies strongly suggest a close link between cytokines and drug resistance. To identify new targets involved in drug resistance, we established a multidrug-resistant human breast cancer cell line MCF-7/R and examined the cytokine profile using cytokine antibody array technology. Among 120 cytokines/chemokines screened, IL-6, IL-8, and 13 other proteins were found to be markedly increased in drug-resistant MCF-7/R cell line as compared to sensitive MCF-7/S cell line, while 7 proteins were specifically reduced in drug-resistant MCF-7/R cells. Neutralizing antibodies against IL-6 and IL-8 partially reversed the drug resistance of MCF-7/R to paclitaxel and doxorubicin, while a neutralizing antibody against MCP-1 had no significant effect. Inhibition of endogenous IL-6 or IL-8 by siRNA technology significantly enhanced drug sensitivity of MCF-7/R cells. Furthermore, overexpression of IL-6 or IL-8 expression by transfection increased the ADM resistance in MCF-7/S cells. Our data suggest that increased expression levels of IL-6 and IL-8 may contribute to MDR in human breast cancer cells.

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Stable re-expression of connexin 43 (cx43) in human glioblastoma suppresses transformation and tumorigenicity. The present study was designed to examine the role of cx43 in chemotherapy-induced apoptosis. Expression of cx43 in human glioblastoma cells significantly increased sensitivity to several common chemotherapeutic agents, including etoposide, paclitaxel (Taxol) and doxorubicin, compared with control-transfected cells. The increased sensitivity to chemotherapeutic agents resulted from apoptosis as evidenced by Hoechst dye staining, TUNEL assay and annexin V assay. These cx43-mediated effects were coupled with decreased expression of the specific apoptosis inhibitor bcl-2. Over-expression of bcl-2 in cx43-transfected cells partially confers the resistance to apoptosis induced by etoposide, suggesting that the cx43-mediated apoptosis to chemotherapeutic agents is regulated in part through the down-regulation of bcl-2 expression. Furthermore, the cx43-mediated apoptosis in response to chemotherapeutic drugs may not be linked to increased gap junctional communication in cx43-transfected cells. Our results demonstrate a new role of cx43 in the mediation of apoptosis during chemotherapy.