Parthenolide and sulindac cooperate to mediate growth suppression and inhibit the nuclear factor-kappa B pathway in pancreatic carcinoma cells.

Activation of the transcription factor nuclear factor-kappa B (NF-kappa B) has been implicated in pancreatic tumorigenesis. We evaluated the effect of a novel NF-kappa B inhibitor, parthenolide, a sesquiterpene lactone isolated from the herb feverfew, in three human pancreatic tumor cell lines (BxPC-3, PANC-1, and MIA PaCa-2). Parthenolide inhibited pancreatic cancer cell growth in a dose-dependent manner with substantial growth inhibition observed between 5 and 10 micromol/L parthenolide in all three cell lines. Parthenolide treatment also dose-dependently increased the amount of the NF-kappa B inhibitory protein, I kappa B-alpha, and decreased NF-kappa B DNA binding activity. We have previously shown that nonsteroidal anti-inflammatory drugs (NSAID) suppress the growth of pancreatic cancer cells. To determine whether inhibition of the NF-kappa B pathway by parthenolide could sensitize pancreatic cancer cells to NSAID inhibition, BxPC-3, PANC-1, and MIA PaCa-2 cells were treated with parthenolide and the NSAID sulindac, either alone or in combination. Treatment with the combination of parthenolide and sulindac inhibited cell growth synergistically in MIA PaCa-2 and BxPC-3 cells and additively in PANC-1 cells. In addition, treatment with the parthenolide/sulindac combination lowered the threshold for apoptosis. Increased levels of I kappa B-alpha protein were detected, especially in MIA PaCa-2 cells, after treatment with parthenolide and sulindac compared with each agent alone. Similarly, decreased NF-kappa B DNA binding and transcriptional activities were detected in cells treated with the combination compared with the single agents, demonstrating cooperative targeting of the NF-kappa B pathway. These data provide preclinical support for a combined chemotherapeutic approach with NF-kappa B inhibitors and NSAIDs for the treatment of pancreatic adenocarcinoma.

Antitumor effects of 5-fluorouracil on human colon cancer cell lines: antagonism by levamisole.

BACKGROUND: The addition of levamisole (Lev) to 5-fluorouracil (5-FU) for the adjuvant treatment of stage III colon cancer has been shown to improve 5-year survival in patients. The mechanism of action of Lev remains unknown. Because we showed little in vitro immunological effect of Lev, we asked whether Lev, alone or in combination with 5-FU, had antitumor activity in vitro. METHODS: Proliferation of COLO-205 and HT-29 colon cancer cells incubated for 2 to 3 days in Lev and 5-FU was measured in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium colorimetric assays. Cell cycle analysis was performed by treating tumor cells for 6, 24, and 48 h with Lev and 5-FU, staining cells with propidium iodide, and measuring DNA content by flow cytometry. RESULTS: The addition of Lev to 5-FU did not reduce proliferation below that of 5-FU alone. The inhibitory concentration 50% (IC(50)) for 5-FU was 3.2 x 10(-6) M for COLO-205 and 1.3 x 10(-5) M for HT-29. An IC(50) was not reached for Lev, even at millimolar doses. DNA analysis of cells treated for 48 h revealed significant S-phase accumulation of both HT-29 (from 17% in control cells to 36% in treated cells) and COLO-205 (from 35% in control cells to 59% in treated cells) cell lines at micromolar 5-FU concentrations. In contrast, Lev alone did not affect cell cycle distribution for either cell line. The addition of Lev to 5-FU not only did not augment, but inhibited, the effects of 5-FU. CONCLUSIONS: Levamisole has no direct cytotoxic effect and no additive or synergistic cytotoxic effect when combined with 5-FU on two colon cancer cell lines. Either the observed clinical effects of Lev treatment occur through an as yet unknown mechanism, require longer treatment periods in vitro to become evident, or the results of clinical trials showing its effectiveness should be carefully reexamined.