Drug interactions and cytotoxic effects of paclitaxel in combination with carboplatin, epirubicin, gemcitabine or vinorelbine in breast cancer cell lines and tumor samples.

The purpose of this study was to analyze the drug interactions of paclitaxel (PTX) with epirubicin (EPI), carboplatin (CBDCA), gemcitabine (GEM) and vinorelbine (VIN) in human breast cancer cells and compare the cytotoxic activity of each drug combination in primary breast cancer samples. These experiments were intended to identify the most active agents in combination with PTX, and to provide a preclinical rational for future clinical investigations in breast cancer. Multiple drug effect/combination index (CI) isobologram analysis was applied to combinations of PTX with either CBDCA, EPI, GEM or VIN in MCF-7, MDA-MB-231 and SK-BR-3 human breast cancer cell lines. Drug concentrations were limited to the ranges achievable in humans in vivo, and the drugs were applied simultaneously at fixed molar ratios for each drug combination. Interactions were assessed at multiple effect levels (IC10-IC90). Additionally, the cytotoxic activity of these combinations was assessed in tumor samples of 50 primary breast cancer patients, utilizing the ATP-tumorchemosensitivity assay (ATP-TCA). Drug interactions were shown to be strongly dose-related in the human breast cancer cell lines investigated. At clinically relevant concentrations, CBDCA/PTX demonstrated synergistic (MCF-7) or additive (MDA-MB-231, SK-BR-3) interactions, and EPI/PTX showed additive (SK-BR-3, MCF-7) and antagonistic (MDA-MB-231) interactions. GEM/PTX and VIN/PTX, however, demonstrated antagonism over multiple dose effect levels at clinically relevant drug concentrations in all three cell lines tested. At plasma peak concentrations, EPI/PTX, CBDCA/PTX, GEM/PTX and VIN/PTX achieved > or = 90% tumor growth inhibition in 93, 86, 63 and 50%, respectively, of primary breast cancer samples investigated with the ATP-TCA. Cumulative dose-response plots of primary breast cancer tumor cells responding in vitro with > or = 90% growth inhibition showed a strong dose dependence for both EPI/PTX and CBDCA/PTX. In conclusion, the current data indicate favorable drug interactions for CBDCA/PTX at clinically relevant drug concentrations in breast cancer cells, and demonstrate superior in vitro cytotoxicity of EPI/PTX and CBDCA/PTX compared to GEM/PTX and VIN/PTX in primary breast cancer cultures.

Her-2/neu and urokinase-type plasminogen activator and its inhibitor in breast cancer.

PURPOSE: Recent studies suggest that HER-2/neu specifically promotes the invasive capacity of tumor cells by up-regulating secretion of the proteolytic enzyme, urokinase-type plasminogen activator (uPA), or its inhibitor, plasminogen activator inhibitor-1 (PAI-1), in colon and gastric cancer. It was the purpose of this study to: (a) evaluate the association between HER-2/neu and uPA and PAI-1 expression in a large primary breast cancer cohort; (b) perform the first multivariate analysis, including HER-2/neu, uPA, and PAI-1 in breast cancer; and (c) define the effect of HER-2/neu overexpression on uPA and PAI-1 expression in breast cancer cells. EXPERIMENTAL DESIGN: HER-2/neu, uPA, and PAI-1 were measured as continuous variables by ELISA in primary breast cancer tissue extracts from 587 patients with clinical follow-up and analyzed for correlations with clinical outcome. Furthermore, a full-length human HER-2/neu cDNA was introduced into five human breast cancer cell lines to define the effects of HER-2/neu overexpression on uPA and PAI-1 expression. In addition, we tested whether HER-2/neu antibodies could reverse any given alteration of uPA and PAI-1 levels. RESULTS: Our findings indicate a weak positive association between HER-2/neu and uPA (r = 0.147; P < 0.001) and no association between HER-2/neu and PAI-1 (r = 0.07; P = 0.085). HER-2/neu overexpression (> or =400 fmol/mg) and high levels of uPA/PAI-1 (> or =5.5 ng/mg and/or > or =14 ng/mg, respectively) were significantly associated with shorter disease-free survival (DFS; P < 0.001 and P = 0.003) and metastasis-free survival (MFS; P = 0.015 and P < 0.001). Multivariate analysis revealed prognostic independence between HER-2/neu and the uPA/PAI-1 axis for DFS and MFS. Both uPA and PAI-1 had no significant discriminatory effect among HER-2/neu-positive patients for DFS. The prognostic value of HER-2/neu overexpression for MFS, however, was significantly enhanced by elevated uPA expression (P = 0.053). Stable transfection of the HER-2/neu gene into multiple human breast cancer cell lines resulted in consistent down-regulation of uPA or PAI-1 expression. In addition, anti-HER-2/neu antibodies did not significantly affect uPA or PAI-1 expression in human cancer cell lines naturally overexpressing HER-2/neu. CONCLUSIONS: The present findings suggest that the invasive phenotype elicited by HER-2/neu overexpression in breast cancer is not a direct effect of uPA or PAI-1 expression. HER-2/neu and the uPA/PAI-1 axis have been shown to affect the invasive capacity of breast cancer independently. Determination of uPA can provide significant additional prognostic information for MFS in HER-2/neu-positive and -negative patients.

Enzyme-catalyzed therapeutic agent (ECTA) design: activation of the antitumor ECTA compound NB1011 by thymidylate synthase.

The in vivo administration of enzyme-inhibiting drugs for cancer and infectious disease often results in overexpression of the targeted enzyme. We have developed an enzyme-catalyzed therapeutic agent (ECTA) approach in which an enzyme overexpressed within the resistant cells is recruited as an intracellular catalyst for converting a relatively non-toxic substrate to a toxic product. We have investigated the potential of the ECTA approach to circumvent the thymidylate synthase (TS) overexpression-based resistance of tumor cells to conventional fluoropyrimidine [i.e. 5-fluorouracil (5-FU)] cancer chemotherapy. (E)-5-(2-Bromovinyl)-2'-deoxy-5'-uridyl phenyl L-methoxyalaninylphosphoramidate (NB1011) is a pronucleotide analogue of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVdU), an antiviral agent known to be a substrate for TS when in the 5'-monophosphorylated form. NB1011 was synthesized and found to be at least 10-fold more cytotoxic to 5-FU-resistant, TS-overexpressing colorectal tumor cells than to normal cells. This finding demonstrates that the ECTA approach to the design of novel chemotherapeutics results in compounds that are selectively cytotoxic to tumor cell lines that overexpress the target enzyme, TS, and therefore may be useful in the treatment of fluoropyrimidine-resistant cancer.

HER-2/neu overexpression and in vitro chemosensitivity to CMF and FEC in primary breast cancer.

Available clinical and experimental data on the effect of HER-2/neu overexpression on chemosensitivity are controversial. It was the purpose of this in vitro study to define the association between HER-2/neu overexpression and the sensitivity to the chemotherapeutic drug combinations of cyclophosphamide, methotrexate and 5-fluorouracil (CMF) and 5-fluorouracil, epirubicin and cyclophosphamide (FEC) of breast cancer cells derived from 140 chemotherapy-naïve patients at the time of primary surgery. Both drug combinations were tested at six different concentrations ranging from 6.25-200% peak plasma concentration (PPC). Immunohistochemical detection of HER-2/neu overexpression was performed with the HER-2/neu antibodies, CB11, TAB250 and AO485, in the same tumor specimens. Immunoreactions were determined as negative (0/1+), weakly positive (2+) and strongly positive (3+). However, the antibodies varied in their degrees of sensitivity. Breast cancer samples with strong (3+) HER-2/neu overexpression demonstrated 90% growth inhibition (IC90) at significantly lower PPC values, using the CB11 (p = 0.048), TAB250 (p = 0.007) and AO485 (p < or =0.01) antibodies, and showed 50% growth inhibition (IC50) at significantly lower PPC values, using the CB11 antibody (p = 0.01) compared to their counterparts with lower levels of HER-2/neu expression. When analyzing the group of patients with intermediate and strong HER-2/neu overexpression (2+ and 3+), an association between HER-2/neu overexpression and increased chemosensitivity was seen with the TAB250 (p = 0.044) and AO485 (p = 0.032) antibodies, but not with the CB11 antibody (p =0.8) at the IC90 level. Differences in chemosensitivity between samples with strong HER-2/neu overexpression and those with lower levels were then analyzed separately for CMF and FEC. Both regimens achieved 90% tumor growth inhibition at lower PPC values in samples with strong HER-2/neu overexpression (3+) compared to their counterparts with lower expression levels (AO485 p = 0.011 for CMF, and p = 0.09 for FEC). Cumulative concentration-response plots of tumors responding in vitro with 90% tumor cell inhibition showed a stronger dose dependence for both CMF and FEC among tumor samples with strong HER-2/neu overexpression compared to those with lower levels of expression. In conclusion, the data show that HER-2/neu overexpression was not associated with in vitro drug resistance to CMF or FEC. In contrast, tumors with strong HER-2/neu overexpression demonstrated increased dose-dependent in vitro sensitivity to both the FEC and CMF regimens.

Inhibitory effects of combinations of HER-2/neu antibody and chemotherapeutic agents used for treatment of human breast cancers.

Previous studies have demonstrated a synergistic interaction between rhuMAb HER2 and the cytotoxic drug cisplatin in human breast and ovarian cancer cells. To define the nature of the interaction between rhuMAb HER2 and other classes of cytotoxic drugs, we applied multiple drug effect/combination index (CI) isobologram analysis to a variety of chemotherapeutic drug/rhuMAb HER2 combinations in vitro. Synergistic interactions at clinically relevant drug concentrations were observed for rhuMAb HER2 in combination with cisplatin (CI=0.48, P=0.003), thiotepa (CI=0.67, P=0.0008), and etoposide (CI=0.54, P=0.0003). Additive cytotoxic effects were observed with rhuMAb HER2 plus doxorubicin (CI=1.16, P=0.13), paclitaxel (CI=0.91, P=0.21), methotrexate (CI=1.15, P=0.28), and vinblastine (CI=1.09, P=0.26). One drug, 5-fluorouracil, was found to be antagonistic with rhuMAb HER2 in vitro (CI=2.87, P=0.0001). In vivo drug/rhuMAb HER2 studies were conducted with HER-2/neu-transfected, MCF7 human breast cancer xenografts in athymic mice. Combinations of rhuMAb HER2 plus cyclophosphamide, doxorubicin, paclitaxel, methotrexate, etoposide, and vinblastine in vivo resulted in a significant reduction in xenograft volume compared to chemotherapy alone (P<0.05). Xenografts treated with rhuMAb HER2 plus 5-fluorouracil were not significantly different from 5-fluorouracil alone controls consistent with the subadditive effects observed with this combination in vitro. The synergistic interaction of rhuMAb HER2 with alkylating agents, platinum analogs and topoisomerase II inhibitors, as well as the additive interaction with taxanes, anthracyclines and some antimetabolites in HER-2/neu-overexpressing breast cancer cells demonstrates that these are rational combinations to test in human clinical trials.

The effect of HER-2/neu overexpression on chemotherapeutic drug sensitivity in human breast and ovarian cancer cells.

Recent studies indicate that oncogenes may be involved in determining the sensitivity of human cancers to chemotherapeutic agents. To define the effect of HER-2/neu oncogene overexpression on sensitivity to chemotherapeutic drugs, a full-length, human HER-2/neu cDNA was introduced into human breast and ovarian cancer cells. In vitro dose-response curves following exposure to 7 different classes of chemotherapeutic agents were compared for HER-2- and control-transfected cells. Chemosensitivity was also tested in vivo for HER-2- and control-transfected human breast and ovarian cancer xenografts in athymic mice. These studies indicate that HER-2/neu overexpression was not sufficient to induce intrinsic, pleomorphic drug resistance. Furthermore, changes in chemosensitivity profiles resulting from HER-2/neu transfection observed in vitro were cell line specific. In vivo, HER-2/neu-overexpressing breast and ovarian cancer xenografts were responsive to different classes of chemotherapeutic drugs compared to control-treated xenografts with no statistically significant differences between HER-2/neu-overexpressing and nonoverexpressing xenografts. We found no instance in which HER-2/neu-overexpressing xenografts were rendered more sensitive to chemotherapeutic drugs in vivo. HER-2/neu-overexpressing xenografts consistently exhibited more rapid regrowth than control xenografts following initial response to chemotherapy suggesting that a high rate of tumor cell proliferation rather than intrinsic drug resistance may be responsible for the adverse prognosis associated with HER-2/neu overexpression in human cancers.