The role of folate receptor alpha (FRα) in the response of malignant pleural mesothelioma to pemetrexed-containing chemotherapy

BACKGROUND: The standard treatment of choice for malignant pleural mesothelioma is chemotherapy with pemetrexed and platinum, but the clinical outcome is poor. This study investigates the response to pemetrexed in a panel of eight mesothelioma cell lines and the clinical outcome for patients treated with pemetrexed in relation to folate receptor alpha (FR alpha).METHODS: Cell lines were treated with pemetrexed to determine the concentration that reduced growth to 50% (GI(50)). FR alpha expression was determined by western blotting and that of FR alpha, reduced folate carrier (RFC) and proton-coupled folate transporter (PCFT) by real-time quantitative RT-PCR. Immunohistochemistry for FR alpha was carried out on 62 paraffin-embedded samples of mesothelioma from patients who were subsequently treated with pemetrexed.RESULTS: A wide range of GI(50) values was obtained for the cell lines, H2452 cells being the most sensitive (GI(50) 22 nM) and RS5 cells having a GI(50) value greater than 10 mu M. No FR alpha protein was detected in any cell line, and there was no relationship between sensitivity and expression of folate transporters. FR alpha was detected in 39% of tumour samples, generally in a small percentage of cells. There was no correlation between the presence of FR alpha and the outcome of pemetrexed treatment, and no significant difference between histological subtypes.CONCLUSION: Response to treatment with pemetrexed does not depend on the presence of FR alpha. British Journal of Cancer (2010) 102, 553-560. doi:10.1038/sj.bjc.6605501 www.bjcancer.com Published online 5 January 2010 (C) 2010 Cancer Research U

Synergistic activity of troxacitabine (Troxatyl™) and gemcitabine in pancreatic cancer

<p>Abstract</p> <p>Background</p> <p>Gemcitabine, a deoxycytidine nucleoside analog, is the current standard chemotherapy used as first-line treatment for patients with locally advanced or metastatic cancer of the pancreas, and extends life survival by 5.7 months. Advanced pancreatic cancer thus remains a highly unmet medical need and new therapeutic agents are required for this patient population. Troxacitabine (Troxatyl™) is the first unnatural L-nucleoside analog to show potent preclinical antitumor activity and is currently under clinical investigation. Troxacitabine was recently evaluated as a first-line therapy in 54 patients with advanced adenocarcinoma of the pancreas and gave comparable overall results to those reported with gemcitabine in recently published randomized trials.</p> <p>Methods</p> <p>The human pancreatic adenocarcinoma cell lines, AsPC-1, Capan-2, MIA PaCa-2 and Panc-1, were exposed to troxacitabine or gemcitabine alone or in combination, for 72 h, and the effects on cell growth were determined by electronic particle counting. Synergistic efficacy was determined by the isobologram and combination-index methods of Chou and Talalay. Mechanistic studies addressed incorporation of troxacitabine into DNA and intracellular levels of troxacitabine and gemcitabine metabolites. For <it>in vivo </it>studies, we evaluated the effect of both drugs, alone and in combination, on the growth of established human pancreatic (AsPC-1) tumors implanted subcutaneously in nude mice. Statistical analysis was calculated by a one-way ANOVA with Dunnett as a post-test and the two-tailed unpaired <it>t </it>test using GraphPad prism software.</p> <p>Results</p> <p>Synergy, evaluated using the CalcuSyn Software, was observed in all four cell-lines at multiple drug concentrations resulting in combination indices under 0.7 at Fa of 0.5 (50% reduction of cell growth). The effects of drug exposures on troxacitabine and gemcitabine nucleotide pools were analyzed, and although gemcitabine reduced phosphorylation of troxacitabine when cells were exposed at equal drug concentrations, there was no effect on phosphorylated pools at drug combinations that were synergistic. The amount of troxacitabine incorporated into DNA was also not affected by the presence of gemcitabine. <it>In vivo </it>testing against a human pancreatic (AsPC-1) xenograft mouse tumor model indicated that both drugs were more than additive at well-tolerated doses and schedule. The biological basis for this synergy is unclear as we did not observe changes in apoptosis, DNA repair, troxacitabine incorporation into DNA or troxacitabine metabolism in the presence of gemcitabine.</p> <p>Conclusion</p> <p>These data, together with phase I clinical data showing tolerability of both agents when combined, suggest combination therapy with troxacitabine and gemcitabine warrants further evaluation in advanced pancreatic cancer patients.</p

Irinotecan plus raltitrexed vs raltitrexed alone in patients with gemcitabine-pretreated advanced pancreatic adenocarcinoma

There is no established second-line treatment for advanced pancreatic cancer after gemcitabine failure. In view of the urgent need for such therapy, and since preclinical and phase I clinical data suggest an encouraging, potentially synergistic activity between raltitrexed and irinotecan, the present randomised phase II study was initiated. A total of 38 patients with metastatic pancreatic adenocarcinoma, who progressed while receiving or within 6 months after discontinuation of palliative first-line chemotherapy with gemcitabine, were enrolled in this study. They were randomised to 3-weekly courses of raltitrexed 3 mg m−2 on day 1 (arm A) or irinotecan 200 mg m−2 on day 1 plus raltitrexed 3 mg m−2 on day 2 (arm B). The primary study end point was objective response, secondary end points included progression-free survival (PFS) and overall survival (OS), as well as clinical benefit response in symptomatic patients (n=28). In the combination arm, the IRC-confirmed objective response rate was 16% (three out of 19 patients had a partial remission; 95% CI, 3–40%), which was clearly superior to that in the comparator/control arm with raltitrexed alone, in which no response was obtained. Therefore, the trial was already stopped at the first stage of accrual. Also, the secondary study end points, median PFS (2.5 vs 4.0 months), OS (4.3 vs 6.5 months), and clinical benefit response (8 vs 29%) were superior in the combination arm. The objective and subjective benefits of raltitrexed+irinotecan were not negated by severe, clinically relevant treatment-related toxicities: gastrointestinal symptoms (42 vs 68%), partial alopecia (0 vs 42%), and cholinergic syndrome (0 vs 21%) were more commonly noted in arm B; however, grade 3 adverse events occurred in only three patients in both treatment groups. Our data indicate that combined raltitrexed+irinotecan seems to be an effective salvage regimen in patients with gemcitabine-pretreated pancreatic cancer. The superior response activity, PFS and OS (when compared to raltitrexed), as well as its tolerability and ease of administration suggest that future trials with this combination are warranted