Residual chromosomal damage after radiochemotherapy with and without amifostine detected by 24-color FISH

Is in vivo and ex vivo irradiation equally reliable for individual Radiosensitivity testing by three colour fluorescence in situ hybridization?

BACKGROUND

Individual radiosensitivity is influencing the outcome of radiation therapy. A general ex vivo testing is very work-intensive. It is of interest to see if a significant prediction concerning the sensitivity can be made by in vivo irradiation during radiation treatment.

METHODS

Blood samples of 274 patients with rectal cancer and 43 lung cancer patients receiving radiotherapy were examined after 2 Gy ex vivo and in vivo ionizing radiation. Chromosomes # 1, 2 and 4 were stained by the 3-color-fluorescence in situ hybridization. Chromosomal aberrations were analyzed as breaks per metaphase (B/M). The deposited energy per session was calculated for each patient.

RESULTS

Weak correlation could be found between the chromosomal aberrations ex and in vivo. Though receiving significantly smaller deposited energy during radiation therapy (RT) the lung cancer cohort displayed B/M values similar to the rectal cancer cohort. Considering the individual deposit energy differences improved slightly the correlation.

CONCLUSIONS

As various factors influence the induction of chromosomal aberrations it seems not feasible to estimate individual radiosensitivity via in vivo irradiation. An ex vivo estimation of individual radiosensitivity should be preferred.

Persistence of radiation-induced aberrations in patients after radiotherapy with C-ions and IMRT

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A follow-up of aberrations in lymphocytes of cancer patients was performed.

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The ratio of dicentrics to translocations declined indicating bone marrow damage.

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Bone marrow exposure was verified by examination of treatment plans.

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Clonal aberrations were also present before therapy and thus not radiation induced.

Background and purpose

Chromosomal aberrations in peripheral blood lymphocytes are a biomarker for radiation exposure and are associated with an increased risk for malignancies. To determine the long-term cytogenetic effect of radiotherapy, we analyzed the persistence of different aberration types up to 2.5 years after the treatment.

Materials and methods

Cytogenetic damage was analyzed in lymphocytes from 14 patients that had undergone C-ion boost + IMRT treatment for prostate cancer. Samples were taken immediately, 1 year and 2.5 years after therapy. Aberrations were scored using the multiplex fluorescence in situ hybridization technique and grouped according to their transmissibility to daughter cells.

Results

Dicentric chromosomes (non-transmissible) and translocations (transmissible) were induced with equal frequencies. In the follow-up period, the translocation yield remained unchanged while the yield of dicentrics decreased to ≈40% of the initial value (p = 0.011 and p = 0.001 for 1 and 2.5 years after compared to end of therapy). In 2 patients clonal aberrations were observed; however they were also found in samples taken before therapy and thus were not radiotherapy induced.

Conclusion

The shift in the aberrations spectrum towards a higher fraction of translocations indicates the exposure of hematopoietic stem and progenitor cells underlining the importance of a careful sparing of bone marrow during radiotherapy to minimize the risk for secondary cancers.

The influence of amifostine administration prior to cyclophosphamide on in vitro maturation of mouse oocytes

PURPOSE

The protective effect of amifostine against cyclophosphamide (CP) was evaluated on mouse oocytes.

MATERIALS AND METHODS

Female mice were divided into four groups as follows: group1: cyclophosphamide (CP) (75 mg/kg, i.p) injection, group2: amifostine (250 mg/kg, i.p) injection, group3: amifostine (250 mg/kg, i.p) administered prior to CP (75 mg/kg, i.p) injection, Control group with injection of saline. About 21 days after injection, in vitro maturation (IVM) of oocytes was recorded. Furthermore the percentage of aneuploid oocytes was determined.

RESULTS

In the CP group IVM rate was significantly decreased and aneploidy rate was significantly increased when compared to other groups (p < 0.05). With the administration of Amifostine prior to CP injection IVM rate was increased and aneploidy rate was decreased.

DISCUSSION

Depletion in IVM rate with administration of CP is due its adverse effects on oocyte quality. Amifostine administration prior to CP injection appears to modulate deleterious effects of CP on oocytes.

Persisting ring chromosomes detected by mFISH in lymphocytes of a cancer patient-a case report

We report the case of an 84 years old prostate cancer patient with severe side effects after radiotherapy in 2006. He was cytogenetically analysed in 2009 and in 2012 in a comparative study for individual radiosensitivity of prostate cancer patients. No other patient had clonal aberrations, but this patient showed ring chromosomes in the range of 21-25% of lymphocytes. He received 5 cycles of 5-fluorouracil/folic acid for chemotherapy of sigmoid colon carcinoma in 2003, three years before radiotherapy of prostate cancer. Blood samples were irradiated ex vivo with Cs-137 γ-rays (0.7Gy/min) in the G0-phase of the cell cycle. 100 FISH painted metaphases were analysed for the control and the irradiated samples each. Multicolour in situ hybridisation techniques like mFISH and mBand as well as MYC locus, telomere and centromere painting probes were used to characterise ring metaphases. Metaphase search and autocapture was performed with a Zeiss Axioplan 2 imaging microscope followed by scoring and image analysis using Metafer 4/ISIS software (MetaSystems). In 2009 chromosome 8 rings were found in about 25% of lymphocytes. Rings were stable over time and increased to about 30% until 2012. The ring chromosome 8 always lacked telomere signals and a small amount of rings displayed up to four centromere signals. In aberrant metaphases 8pter and 8qter were either translocated or deleted. Further analyses revealed that the breakpoint at the p arm is localised at 8p21.2-22. The breakpoint at the q arm turned out to be distal from the MYC locus at 8q23-24. We hypothesise that the ring chromosome 8 has been developed during the 5 FU/folic acid treatments in 2003. The long term persistence might be due to clonal expansion of a damaged but viable hematopoietic stem cell giving rise to cycling progenitor cells that permit cell survival and proliferation.

Cytogenetic abnormalities and clinical features in a patient cohort affected by three or more synchronous or metachronous primitive malignancies

The multiple cancers (MC) phenotype represents an intriguing entity from both the clinical and the biomolecular points of view. Multiple cancers can arise in a patient either synchronously or metachronously and are frequently detected in hereditary disorders. Here we report the clinical and cytogenetic characterization of 48 patients developing at least three malignancies outside the context of a known genetic condition and 30 control individuals. Medical and pathology reports were registered, blood was collected for cytogenetic studies, and the standard G-banding technique was used for chromosomal analysis of the lymphocyte cultures. Chromosomal analysis of the peripheral blood cultures revealed high cytogenetic instability in 83% of patients' karyotypes that displayed structural rearrangements most often involving chromosomes X, 1, 6, and 7. Peculiar telomeric associations and marker chromosomes were detected in patients with a suspected cancer family history. The MC condition can be observed over a wide clinical range, which includes either apparently sporadic cases or families with a strong history of tumors. These findings indicate that Xq, 6p, and 7q are likely to harbor genes of importance in cancer development, and the present cytogenetic mapping may be crucial for further molecular genetic investigations to recognize a predictive cytogenetic signature useful to detect patients with a high risk of multiple malignancies.

Technical report: Radiation sensitivity testing by fluorescencein‐situhybridization: how many metaphases have to be analysed?

PURPOSE

The technique of three-colour fluorescence in-situ hybridization (FISH) is generally regarded as 'gold standard' for detecting chromosomal aberrations. The question was: how many metaphases should be counted to get reliable results?

MATERIAL AND METHODS

Peripheral blood lymphocytes were irradiated in vitro (2.0 Gy). Metaphase chromosomes (1, 2, 4) were labelled by means of three-colour FISH and chromosomal aberrations (breaks per metaphase [B/M], complex chromosomal rearrangements per metaphase [CCR/M]) were analysed. To evaluate the correlation between the number of metaphases counted and the reliable detection of the rate of break events, B/M and CCR/M were scored using 250-1,000 metaphases in steps of 50 unirradiated cells, and from 50 to 200 metaphases in steps of 10 after 2 Gy.

RESULTS

Analysing spontaneously occurring aberrations, B/M values based on 500 and 750 counted metaphases agreed well with those B/M values from 1,000 scored metaphases. After counting 150 metaphases after 2 Gy, the confidence interval of B/M values was about 44% smaller and the confidence interval of CCR/M values was about 41% smaller compared with values obtained after counting 100 metaphases.

CONCLUSIONS

Scoring the number of spontaneous aberrations, reliable results can be obtained after counting 500 metaphases. After 2 Gy, a minimum of 150 metaphases should be analysed.

Cytogenetic damage induced by radiotherapy. Evaluation of protection by amifostine and analysis of chromosome aberrations persistence

PURPOSE

To evaluate the cytogenetic damage induced by radiotherapy, the effect of concomitant amifostine and the persistence of translocations and dicentrics after the treatment.

MATERIALS AND METHODS

Blood samples from 16 head and neck cancer patients were obtained at different times, just before treatment, at the 1st and 22nd sessions, at the end of radiotherapy, and one, four and 12 months later. Solid stain and fluorescent in situ hybridization (FISH) techniques were applied to analyse chromosome aberrations.

RESULTS

In all the analysis the frequencies of dicentrics plus rings were slightly lower in the group of patients receiving concomitant amifostine, but in each sampling point the differences were not significant. The persistence of translocations and dicentrics one year after radiotherapy was very similar, with a decline of more than 50%. For all the chromosome aberrations considered, a negative correlation between their initial yield and the percentage of this yield remained 12 months after radiotherapy was observed (p < 0.05).

CONCLUSION

No significant protection by amifostine against radiation-induced chromosome damage was observed in head and neck cancer patients treated only with radiotherapy. In these cases, the persistence of translocations and dicentrics during the first year after radiotherapy is similar and related to their initial yield.

Cytogenetic damage in lymphocytes of patients undergoing therapy for small cell lung cancer and ovarian carcinoma

The level of cytogenetic damage in peripheral blood lymphocytes of patients undergoing chemotherapy has been analyzed incisively 20 years ago. The results showed that the highest level of cytogenetic damage was observed at the end of therapy. In recent years, the doses of anticancer drugs were intensified thanks to the discovery of colony stimulating factors. Therefore, it was interesting to analyze the kinetics of micronuclei formation in lymphocytes of patients undergoing modern chemotherapy. The frequencies of micronuclei were measured in lymphocytes of 6 patients with small cell lung cancer treated with a combination of cisplatin and etoposide and 7 patients with ovarian carcinoma treated with a combination of taxol and cisplatin. 3 patients with lung cancer received radiotherapy in addition to chemotherapy. Micronuclei were analyzed in lymphocytes collected before the start of therapy and 1 day before each following cycle of chemotherapy. The micronucleus frequencies were compared with the kinetics of leukocyte counts. The micronucleus frequencies showed an interindividual variability. On average, the frequencies of micronuclei increased during the first half of therapy and declined thereafter, reaching, in some patients with ovarian carcinoma, values below the pre-treatment level. Leukocyte counts decreased strongly at the beginning of therapy with an upward trend at the end. We suggest that the decline of micronuclei was due to repopulation of lymphocytes and acquired drug resistance.

Cytogenetic instability in young patients with multiple primary cancers

Patients younger than 45 years with multiple cancers and a family history of cancer were identified and examined for cytogenetic instability. The cohort included 50 individuals: 19 patients suffering from at least 2 independent cancers, 11 healthy control individuals, a positive control group of 5 highly radiosensitive patients (>grade 3, RTOG), and a tumor control group of 15 patients with a single tumor. Peripheral blood lymphocytes were irradiated in vitro (0.7 Gy, 2.0 Gy). Metaphase chromosomes 1, 2, and 4 were labeled by means of 3-color fluorescence in situ hybridization. Chromosomal aberrations (breaks per metaphase [B/M], complex chromosomal rearrangements [CCR/M]) were analyzed. Very high levels of chromosomal aberrations were detected in a "core group" of 5 patients. These patients displayed much higher rates of B/M and CCR/M than controls. Ten patients had moderately elevated chromosomal aberrations and 4 patients were indistinguishable from controls. We conclude that a significant proportion of young patients with multiple tumors and a family background of cancer display cytogenetic instability.