Sensitivity of non-small-cell lung cancer cell lines established from patients treated with prolonged infusions of Paclitaxel.

OBJECTIVE: Regimens with prolonged infusions of taxanes have been developed for patients with cancer to overcome drug resistance. Our objective of the present study was to examine the impact of prolonged exposure on the cytotoxicity of taxanes against non-small-cell lung carcinoma (NSCLC) cell lines and the clinical response and outcome of the patients. METHODS: Five cell lines (NCI-H2882, -H2887, -H2973, -H3122, -H3255) were derived from previously untreated patients with NSCLC who participated in clinical trials of continuous 96-hour infusions of paclitaxel followed by bolus cisplatin. Two additional cell lines (NCI-H838, -H1299) with previously published data were used as controls. Drug sensitivities were assessed by the MTS (Promega) assay. Multidrug resistance (MDR) phenotypes were assessed by quantitative real-time PCR and HER-2/NEU by both immunohistochemistry and ELISA. RESULTS: The median of mean IC(50) values of docetaxel at the exposure durations of 3, 24, 72 and 120 h were 0.52, 0.06, 0.03 and 0.06 microM, respectively. The median of mean IC(50) values of paclitaxel at the exposure duration of 3, 24, 72 and 120 h were 0.48, 0.13, 0.03 and 0.02 microM, respectively. In all cell lines studied, there was a less than 4-fold difference in the IC(50) values between docetaxel and paclitaxel at 3-, 72-, and 120-hour exposure times. The single cell line with moderate MDR1 expression (NCI-H2887) was the only cell line established from a patient with progressive disease when treated with paclitaxel. CONCLUSIONS: This study demonstrates prolonged exposure to both docetaxel and paclitaxel inhibits the growth of NSCLC cell lines in similar fashion.

Regulation of cellular proliferation, cytoskeletal function, and signal transduction through CXCR4 and c-Kit in small cell lung cancer cells.

The regulation of biological functions including cell growth, viability, migration, and adhesion of small cell lung cancer (SCLC) cells depends largely on the autocrine or paracrine stimulation of growth factor receptors and chemokine receptors. Stem cell factor (SCF) and its receptor c-Kit have been identified as important regulators of SCLC viability and are coexpressed in approximately 40-70% of SCLC specimens. In vitro, the inhibition of c-Kit tyrosine kinase activity by the small molecule tyrosine kinase inhibitor STI571 (Gleevec) abrogates cell growth. We have investigated the role of c-Kit and chemokine receptors in the regulation of cell migration and adhesion of SCLC cells. CXCR4, the chemokine receptor for stromal cell-derived factor-1alpha (SDF-1alpha), was found to be the major chemokine receptor commonly expressed in all of the 10 SCLC cell lines tested. SCF and SDF-1alpha increased cellular proliferation over a course of 72 h in both the c-Kit- and the CXCR4-positive NCI-H69 SCLC cell line. Recently, SDF-1alpha and CXCR4 have been shown to be important regulators of migration and metastasis in breast and ovarian cancer. We found that SDF-1alpha dramatically increased cell motility and adhesion in CXCR4-expressing NCI-H446 SCLC cells. In addition, SDF-1alpha altered cell morphology with increased formation of filopodia and neurite-like projections. In NCI-H69 SCLC cells, SCF and SDF-1alpha cooperatively induced morphological changes and activated downstream signaling pathways. Treatment of NCI-H69 cells with STI571 specifically inhibited the c-Kit signaling events of Akt and p70 S6 kinase, whereas SDF-1alpha-mediated activation of Akt or p70 S6 kinase was normal. In contrast, the phosphatidylinositol 3-kinase inhibitor, LY294002, prevented these cells from adhering and completely blocked SCF- and/or SDF-1alpha-induced Akt or p70 S6 kinase phosphorylation. These results demonstrate that the CXCR4 receptor is functionally expressed in SCLC cells and may, therefore, be involved in the pathogenesis of SCLC in vivo. Inhibition of both the CXCR4 and the c-Kit downstream events could be a promising therapeutic approach in SCLC.