Seventy-nine patients with advanced, measurable, metastatic colorectal cancer previously unexposed to chemotherapy were randomly assigned to treatment with either fluorouracil (FUra) administered intravenously at a dose of 370 mg/m2/d for 5 days or the combination of FUra in the same dose and schedule with high-dose continuous infusion leucovorin calcium (500 mg/m2/d) beginning 24 hours before the first dose of FUra and continuing for 12 hours after the completion of FUra therapy. Patients whose disease progressed on treatment with FUra alone were, if eligible, crossed over to receive leucovorin and FUra. Three patients on the FUra plus leucovorin arm of the study were excluded from the analysis because they did not meet eligibility requirements. The treatment arms were well balanced for prognostic criteria including performance status, age, prior radiotherapy, distribution of metastatic sites, and on-study carcinoembryonic antigen (CEA), lactic dehydrogenase, and serum albumin. FUra plus leucovorin was superior to FUra alone for response (P = .0019) and for time to progression or death (log-rank, P = .045). Response rates were 16 of 36 (44%) versus five of 40 (13%), and median time to progression or death was 164 versus 120 days in the two arms of the trial, respectively. Overall survival, however, while longer in the FUra and leucovorin arm was not significantly so. An analysis of the toxicities experienced by the patients in the two treatment groups showed that, except for significantly more stomatitis in the leucovorin arm of the study, the side effects experienced by patients treated with either regimen were comparable. These results suggest that the efficacy of FUra in patients with advanced, measurable, metastatic colorectal cancer can be enhanced significantly by administration of a continuous high-dose infusion of leucovorin calcium.
Abstract: Identification of differential sensitivity of cancer cells as compared to normal cells has the potential to reveal a therapeutic window for the use of silver nanoparticles (AgNPs) as a therapeutic agent for cancer therapy. Exposure to AgNPs is known to cause dose-dependent toxicities, including induction of oxidative stress and DNA damage, which can lead to cell death. Triple-negative breast cancer (TNBC) subtypes are more vulnerable to agents that cause oxidative stress and DNA damage than are other breast cancer subtypes. We hypothesized that TNBC may be susceptible to AgNP cytotoxicity, a potential vulnerability that could be exploited for the development of new therapeutic agents. We show that AgNPs are highly cytotoxic toward TNBC cells at doses that have little effect on nontumorigenic breast cells or cells derived from liver, kidney, and monocyte lineages. AgNPs induced more DNA and oxidative damage in TNBC cells than in other breast cells. In vitro and in vivo studies showed that AgNPs reduce TNBC growth and improve radiation therapy. These studies show that unmodified AgNPs act as a self-therapeutic agent with a combination of selective cytotoxicity and radiation dose-enhancement effects in TNBC at doses that are nontoxic to noncancerous breast and other cells. Keywords: DNA damage, radiation sensitizer, glutathione, redox
The use of leucovorin to modulate 5-fluorouracil (FUra)-mediated inhibition of thymidylate synthase has been shown both in vitro and in vivo to improve the antitumor activity of FUra. Based on the activity of this combination in previously untreated patients, we performed a study of FUra and high-dose leucovorin (HDFA) in patients with metastatic breast cancer and minimal prior chemotherapy. Patients were stratified by prior chemotherapy (or relapse within 12 months of completing adjuvant chemotherapy) versus no prior chemotherapy (or relapse at greater than 12 months since completion of adjuvant chemotherapy). FUra was given daily for 5 days at 370 mg/m2/day with HDFA, 500 mg/m2/day, beginning 24 hours before and continuing 12 hours beyond the first and last FUra doses, respectively. Two objective responses occurred among 21 patients in the pretreated group (10%; 95% confidence interval: 1–30%). Four of 36 eligible patients (11%) in the “no prior therapy group” had complete responses (95% confidence interval: 3–26%). The major toxicities were moderate leucopenia and mucositis. We conclude that FUra plus leucovorin has modest antitumor activity in metastatic breast cancer.
Abstract A simple procedure for the isolation of genes as DNA fragment lengths is described. By using a commercial continuous elution protein electrophoresis apparatus and incorporating an agarose matrix, preparative scale amounts (300 μg) of DNA can be purified by fragment lengths from a mixture of genomic fragment lengths with high recovery yields. Fractions corresponding to unique fragment length ranges are screened for individual genes by dot‐blot analysis. Using this technique, we have isolated two genes: PGK1 , a single copy housekeeping gene; and p53 (exons 3–11), a tumor suppressor gene, whose DNA fragment lengths elute at 4 and 7.5 kbp, respectively, from a single preparative run. As an example of the utility of the technique, we applied it to improving the sensitivity of the ligation‐mediated polymerase chain reaction (LMPCR) — a nucleic acid amplification technique used for the detection and mapping of DNA damage along genes. By eliminating excess nontargeted genomic DNA, the agarose matrix continuous elution electrophoresis (CEE) procedure provided a 24‐fold increase in signal strength attributable to base damage caused by exposing DNA to reactive oxygen species. Genomic DNA fragment length purification by agarose matrix CEE should also prove useful in other research areas requiring gene isolation, such as genomics and molecular biology.
Under physiological conditions, guanine-rich sequences of DNA and RNA can adopt stable and atypical four-stranded helical structures called G-quadruplexes (G4). Such G4 structures have been shown to occur in vivo and to play a role in various processes such as transcription, translation and telomere maintenance. Owing to their high-thermodynamic stability, resolution of G4 structures in vivo requires specialized enzymes. RHAU is a human RNA helicase of the DEAH-box family that exhibits a unique ATP-dependent G4-resolvase activity with a high affinity and specificity for its substrate in vitro. How RHAU recognizes G4-RNAs has not yet been established. Here, we show that the amino-terminal region of RHAU is essential for RHAU to bind G4 structures and further identify within this region the evolutionary conserved RSM (RHAU-specific motif) domain as a major affinity and specificity determinant. G4-resolvase activity and strict RSM dependency are also observed with CG9323, the Drosophila orthologue of RHAU, in the amino terminal region of which the RSM is the only conserved motif. Thus, these results reveal a novel motif in RHAU protein that plays an important role in recognizing and resolving G4-RNA structures, properties unique to RHAU among many known RNA helicases.
