Identification of Tumor-Specific Paclitaxel (Taxol)-Responsive Regulatory Elements in the Interleukin-8 Promoter

Abstract

Paclitaxel is a novel antineoplastic drug which has shown promise in the treatment of previously unresponsive breast, ovary, lung, and colon cancers. Paclitaxel is active at nanomolar concentrations and functions by binding to the amino-terminal region of the ␤-tubulin molecule, thereby promoting and stabilizing the formation of microtubules. However, the therapeutic effectiveness of paclitaxel exceeds that of microtubuledisrupting agents such as colchicine and vinca alkaloids, suggesting that paclitaxel may have multiple effects on cells. Recent studies in mice show that paclitaxel and bacterial lipopolysaccharide (LPS) can induce a broad range of shared bioactivities in macrophages, which includes the following: (i) induction of a series of cytokines, such as interleukin-1␣ (IL-1␣), IL-1␤, tumor necrosis factor alpha (TNF-␣), and IP-10 (1, 5, 15, 36-38); (ii) internalization of TNF-␣ receptors (14, 15); (iii) induction of a panel of immediate early genes; (iv) provision of a second signal for macrophage tumoricidal activity and nitric oxide production (25); and (v) induction of the phosphorylation of mitogen-activated protein kinases and activation of the autophosphorylation of lyn kinase (15,22,36,37). In addition, LPS-hyporesponsive C3H/HeJ mice do not respond to paclitaxel with the same pattern of phosphorylation and gene induction as other mice do, suggesting that paclitaxel and LPS may share a functionally important signaling transduction pathway (15,37).In contrast to its effect on mouse cells, the effect of paclitaxel on human macrophages/monocytes has been more difficult to demonstrate. However, paclitaxel activates IL-8 but not IL-1␣ or IL-1␤ or IL-6 transcription in a subset of human ovarian cancer cell lines and in freshly explanted ovarian cancer cells (32). Since ovarian cancer represents a primary type of tumor that is clinically responsive to paclitaxel, these findings may have significant clinical ramifications.IL-8 is a member of the superfamily of C-X-C chemokines (29), and it is a chemotactic factor for T cells, neutrophils, and basophils (41,47,59). IL-8 induction in tumors may be beneficial to the host in that immune cells are attracted to the tumor site. In fact a recent study by Hirose et al. shows that this is indeed the case (23). Alternatively, IL-8 also enhances angiogenesis and may enhance metastasis (51). Regardless of which role IL-8 plays in a clinical setting, understanding how paclitaxel activates the IL-8 gene can elucidate additional molecular targets of paclitaxel and provide an understanding which may lead to better antitumor therapies.The IL-8 gene is regulated at both the transcriptional and posttranscriptional levels. The former is primarily mediated by multiple cis elements, including a CCAAT box, a steroid-responsive element, an HNF-1 element, two IRF-1 elements, an AP-1 sequence, an AP-3 site, a C/EBP sequence, and an NF-B-NF-IL-6 overlapping sequence (30,40,42,46). Earlier, we demonstrated that paclitaxel can induce IL-8 gene expression in human ovarian cancer cells ...

Paclitaxel (Taxol) upregulates expression of functional interleukin-6 in human ovarian cancer cells through multiple signaling pathways

“…In addition to its stabilizing effects on the microtubules and the subsequent cell cycle arrest in the G2-M phase, paclitaxel also induces the vast activation of signal-transduction pathways that may be associated with proapoptotic signaling (Blagosklonny and Fojo, 1999;Taxman et al, 2003). Among the proapoptotic signaling networks activated by paclitaxel (Meikrantz and Schlegel, 1996;Lee et al, 1997), the c-Jun Nterminal kinase (JNK) signaling pathway played an important role (Lee et al, 1998;Wang et al, 1999Wang et al, , 2000MacKeigan et al, 2000;Vivat-Hannah et al, 2001;Mingo-Sion et al, 2004).…”

Paclitaxel (Taxol)-induced Gene Expression and Cell Death Are Both Mediated by the Activation of c-Jun NH2-terminal Kinase (JNK/SAPK)

“…pCMVERK1 was a generous gift from Dr. D. A. Brenner (University of North Carolina, Chapel Hill) (44). IL-8 Ϫ133 CAT was described previously (15).…”

“…This induction is mediated by the activation of NF-B and AP-1 transcription factors, which bind to cognate sites in the IL-8 promoter. Gel shift assays show that paclitaxel caused a marked increase in protein binding to AP-1 and NF-B cognate sequences in paclitaxel-responsive cells but not in nonresponsive cells (15). However, little is known about the upstream signaling events that lead to the activation of these transcription factors in response to paclitaxel.…”

Paclitaxel-induced cell death

“…Paclitaxel is also shown to activate interleukin (IL)-8 transcriptionally in ovarian carcinoma cells, 90 and the transcription factor (AP-1, NF-B) binding sites of the IL-8 promoter are required for activation by paclitaxel. 91 …”

“…93 It has been clearly documented that paclitaxel concentrations required for blocking mitotic progression are low (IC 50 ϭ 8 nM in HeLa cells), whereas high concentrations of paclitaxel (IC 50 ϭ 330 nM in HeLa cells) are required for stabilizing polymerization (measured by microtubule mass) and massive microtubule damage. 13,25,67,94 Furthermore, in studies in which paclitaxel had functions other than mitotic arrest, the concentrations of paclitaxel used were often high, ranging from 200 nM to 30 M. 40,44,55,56,68,84,90,91,95,96 In agreement with the notion that higher concentrations of paclitaxel are required to exert functions in addition to mitotic arrest, we have observed a positive correlation between fold activation of JNK/SAPK and paclitaxel concentrations from 10 nm to 10 M, 83 suggesting that activation of the JNK/SAPK pathway is more associated with microtubule damage (induced by high concentrations of paclitaxel) than with mitotic arrest (by low concentrations of paclitaxel).…”