Chromosomal aberrations in synchronized mammalian cells treated with 5-bromo-deoxyuridine and irradiated by ultra-violet light

Monitoring DNA breaks in optically highlighted chromatin in living cells by laser scanning confocal microscopy

The recognition and repair of DNA lesions occurs within a chromatin environment. Genetically tagging fluorescent proteins to DNA damage response proteins has provided spatial and temporal details concerning the establishment of biochemical subnuclear regions geared toward metabolizing genomic lesions. A specific marker for chromatin regions containing DNA breaks is required to study the initial dynamic structural changes in chromatin when DNA breaks occur. Here we present the experimental protocols used to investigate the dynamics of chromatin structure immediately after the simultaneous photoactivation of PAGFP-tagged core histone H2B and introduction of DNA breaks using UVA laser microirradiation on a laser scanning confocal microscope.

A phase II trial of high-dose bromodeoxyuridine with accelerated fractionation radiotherapy followed by procarbazine, lomustine, and vincristine for glioblastoma multiforme

PURPOSE

To conduct a Phase II study to evaluate the long-term efficacy and safety of high-dose 5'-bromodeoxyuridine (BrdU) and accelerated radiotherapy followed by procarbazine, lomustine (CCNU), and vincristine (PCV) chemotherapy in patients with glioblastoma multiforme.

METHODS AND MATERIALS

Between 1994 and 1996, 88 patients were enrolled to receive 1.9 Gy of radiation three times a day for two 5-day cycles separated by 2 weeks; each 5-day cycle was preceded by a continuous 96-hour infusion of BrdU at a dose of 2.1 g/m2/day. After radiotherapy, patients received PCV chemotherapy.

RESULTS

Median survival for all 88 patients was 50 weeks. Seventy (79.5 %) received one or more courses of PCV; their median survival was 57 weeks. Covariates predictive of improved survival were gross total versus subtotal resection or biopsy (p = 0.0048) and radiation dose > or = 56 Gy (p = 0.019). While receiving BrdU, 47 patients (53%) suffered grade 3 or 4 thrombocytopenia or leukopenia; 22 patients (25%) suffered grade 3 or 4 dermatologic toxicity.

CONCLUSION

Survival was not extended in patients with glioblastoma or gliosarcoma who received BrdU at the dose and administration schedule used in this study. The BrdU dose used in this study resulted in substantial myelosuppressive and dermatologic toxicity.

Radiation therapy and bromodeoxyuridine chemotherapy followed by procarbazine, lomustine, and vincristine for the treatment of anaplastic gliomas

PURPOSE

To conduct a Phase II study to evaluate the long-term efficacy and safety of radiotherapy combined with intravenous bromodeoxyuridine for patients with anaplastic glioma tumors.

METHODS AND MATERIALS

Between 1983 and 1987, study patients received 1.7-1.8 Gy radiation once a day, Monday through Friday, to a total dose of 60 Gy. On the Thursday prior to beginning radiotherapy and for the next 5 weeks (6 weeks total), patients received a continuous 96 h intravenous infusion of bromodeoxyuridine at 0.8 g/m2/24 h; following radiotherapy, patients received procarbazine, lomustine (CCNU), and vincristine (PCV) for 1 year or until tumor progressed.

RESULTS

One-hundred thirty eight patients (median age, 43 years) were evaluable for analysis. Estimated 4-year survival for the anaplastic astrocytoma (AA) stratum (n = 116) is 46%. For the astrocytoma (ASTRO) stratum (n = 22), the 6-year survival is estimated at 79%. Estimated 4-year progression-free survival for AAs is 42%, and for ASTROs, 68%. Whole brain irradiation was used in 23% and limited-field irradiation in 77%; patients receiving limited-field irradiation had a better survival rate (p = 0.07). Total tumor resection was performed in 15%, partial resection in 53%, and biopsy only in 32%. For the 81 patients with tumor recurrence, 34 (42%) are known to have received additional treatment(s). For AA, fits of the Cox proportional hazards regression model showed that covariates individually predictive of survival were younger age (p < 0.001), Karnofsky performance score (p = 0.10). Major toxicities were rash during Weeks 1 through 6 requiring dose modification in 14%, Grade > or = III leukopenia in 18%, and Grade > or = III thrombocytopeni in 9%.

CONCLUSION

The study suggests that the bromodeoxyuridine-radiotherapy-PCV, compared with other published therapies, can improve progression-free survival, and aggressive treatment of ASTRO patients can lead to substantial increases in survival compared to published survival data.

Quantized generation time in mammalian cells as an expression of the cellular clock

The distribution of possible generation times in mammalian cells does not appear to be continous within the limits of range for each cell type; rather, generation time is quantized in multiples of 3-4 hr. Synchronous cultures of Chinese hamster V79 cells were prepared using manual and automated methods to select and stage mitotic cells. Using synchronous cultures and time-lapse video tape microscopy, it was possible to show that generation times within a population of mitotically selected cells normally disperse in a quantized fashion, with intervals of 3-4 hr occurring between bursts in division. In addition, at temperatures above 37 degrees, V79 cells have a 7.5-8.5 hr modal cell cycle, while at temperatures from 36.5 degrees to 33.5 degrees the modal cell cycle is 11-12 hr long. A survey of the synchrony literature reveals that the tendency to preferred generation times holds between cell lines. The distribution of modal generation times from a variety of different cell types forms a series with a similar interval but with a greater range of values than that observed here for V79 cells. To satisfy the published data and the work presented here, I propose a subcycle, Gq, which has a traverse time equal to the period of the clock. The period appears to be fixed at close to the same value in all mammalian somatic cells. The timekeeping mechanism appears to be temperature compensated, since the time required to traverse Gq is constant at temperatures between 34 degrees and 39 degrees. It is suggested that cell cycle time increases at lower temperatures, lower serum concentration, and high cell densitite because the number of rounds of traverse through Gq increases.