Chromosomal aberrations induced by chemotherapy and radiotherapy in lymphocytes from patients with breast carcinoma

CYTOGENETIC DAMAGES IN LUNG CANCER PATIENTS TREATED BY EXTERNAL RADIATION THERAPY

OBJECTIVE

to estimate the chromosome type aberrations outcome in lung cancer patients during radiation therapy course depending on radiation energy.

MATERIALS AND METHODS

Chromosome aberrations were studied in 16 lung cancer patients examined before treat- ment in the middle and at the end of external gamma-radiotherapy 60Со on ROCUS-AM and megavolt therapy on lin- ear accelerator Clinac 600C.

RESULTS

The radiation-induced chromosome aberrations outcome in lung cancer patients during radiotherapy with different irradiation sources was studied. The over-spontaneous excess of chromosome type aberrations in cancer patients before treatment was shown. The similar and different features of cytogenetic damage accumulation dur- ing radiation therapy regarding to radiation type was displayed. The cytogenetic damage frequency raised during the course of therapeutic exposure in both studied groups. At the same time, the growth rate depended on the irra- diation regimen and was higher for patients undergoing 60Co gamma-therapy. The different range of cells with unsta- ble chromosome aberrations from the beginning to the end of the radiation therapy course was displayed. In the middle of the course the number of aberrations per aberrant cell was similar - 1-5 damages for gamma therapy, 1-4 damages for megavoltage therapy. At the end of treatment the maximum of 10 aberrations per aberrant cell for ROCUS-AM and in 5 aberrations per aberrant cell for linear accelerator was observed. During radiotherapy the distri- butions of radiation-induced chromosome aberrations was found to be over-dispersed according to Poisson statis- tic in both patients' groups.

CONCLUSIONS

The study of chromosome type aberration revealed the particularities of cytogenetic damages out- come during radiotherapy course depending on the irradiation source used. The more pronounced genotoxic effect in blood lymphocytes of lung cancer patients due to gamma-irradiation with ROCUS-AM was demonstra- ted despite the higher radiation energy used on a linear accelerator. Therefore, in radiation treatment effects estimation it is necessary to take into account not only the radiation quality and energy, but also the source, regimen and pre-radiotherapy procedures. The data obtained can contribute to the assessment of the conse- quences of local fractionated irradiation and to the development of a reference biodosimetry system in radia- tion therapy.

CLINICAL APPLICATIONS OF BIOMARKERS OF RADIATION EXPOSURE: LIMITATIONS AND POSSIBLE SOLUTIONS THROUGH COORDINATED RESEARCH

Dosimetric biomarkers have been effectively and intensively used for a long time in the area of radiation protection. In contrast to that, no robust standards or widely accepted protocols for application of these end-points in radiotherapy, diagnostic and interventional radiology and nuclear medicine exist to date. The International Atomic Energy Agency (IAEA) organized the review of the available data on the possibilities of the use of dosimetric biomarkers in medical irradiation scenarios. The resultant Technical Report also contains a summary of identified problems, gaps in knowledge, limitations in methodology and recommendations for their overcoming. This work provided a conceptual background for the initiation of a new IAEA Coordinated Research Project E35010, MEDBIODOSE (2017-21), which is aimed specifically at the development and improvement of applications of biodosimetric markers in clinical practice.

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.

DNA and cytogenetic damage in white blood cells of postmenopausal breast cancer patients treated with radiotherapy

The primary and residual genome damage and its elimination rate were evaluated in peripheral blood lymphocytes of breast cancer patients treated with adjuvant radiotherapy after surgical removal of the tumor by mastectomy or quadrantectomy. The levels of DNA/chromosome damage were estimated before, throughout, as well as after six months, respectively one year after the radiotherapy, using the alkaline comet assay, the chromosome aberration analysis and the cytokinesis-block micronucleus assay. The marked individual differences in the baseline genome damage were observed in patients, which additionally increased until the end of the radiotherapy cycle. The levels of DNA/cytogenetic damage slowly declined during post-irradiation period; although in the majority of subjects they did not return to pre-therapy levels. In addition to the well-established comet parameters, the long-tailed nuclei were also proved as a useful indicator of individual DNA damage and response to radiation. One of the most important observation was that older breast cancer patients, irradiated after mastectomy, had higher values of almost all parameters evaluated. We found positive correlations between the comet assay parameters and the cytogenetic biomarkers that confirmed their complementary value in the assessment of the radiation sensitivity/susceptibility in elderly breast cancer patients. The specific patterns of DNA damage observed in the majority of subjects after a prolonged exposure to ionizing radiation indicate the possibility of adaptive response. Such results may also be linked to the hormesis theory and support previous observations, but the underlying mechanisms should be further investigated on a much larger population.

Peripheral leukocyte response to oncological radiotherapy: Expression of heat shock proteins

PURPOSE

To study Heat Shock Proteins (HSP) expression in patients subjected to radiotherapy and their potential use as biomarkers for radiation tolerance. An evaluation is also made of whether irradiated volume is critical to the outcome of normal tissue injury using polymorphonuclear neutrophils as biosensors, and whether HSP antibodies (Ab) may be involved in post-radiotherapy disease.

MATERIAL AND METHODS

Twelve patients receiving the same total dose of radiotherapy, but in three different volumes, and four healthy volunteers used as controls were analysed. hsp27 and 70i mRNA were determined by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and Southern-blot, HSP by flow cytometry, and HSP-Ab by Enzyme-linked Immnoadsorbent Assay (ELISA). The clinical protocol included radiation related toxicity based on clinical and analytical scales.

RESULTS

Radiotherapy caused hsp downregulation, maximum in patients with the largest irradiated volumes, and a decrease in intracellular HSP content. Patients with greatest intraleukocyte HSP levels before treatment suffered more severe radiation morbidity. Patients with endocrine neoplasms presented the highest HSP-Ab titers.

CONCLUSIONS

Radiotherapy downregulates hsp27 and 70i, which would enhance radiosensitivity. HSP content prior to treatment is suggested as a prognostic biomarker for radiation tolerance, with circulating leukocytes as biosensors. HSP-Ab may be biomarkers of tumor disease, but do not seem to be involved in the morbidity of acute post-radiotherapy disease, which is closely related to the volumes irradiated.

Frequency of sister chromatid exchanges and micronuclei monitored over time in patients with early-stage breast cancer: results of an observational study

Spontaneous chromosomal instability correlates with a high risk of cancer. The frequency of spontaneous sister chromatid exchanges (SCE) and micronuclei (MN) in peripheral blood lymphocytes was used for evaluation of spontaneous chromosomal instability in early-stage breast cancer patients to determine whether SCE and MN frequencies are biomarkers of damage from chemotherapy and radiotherapy. In 20 stage I-II breast cancer patients, SCE and MN were measured before surgery and at 4 weeks after. In patients who received adjuvant chemotherapy (CTx), they were also determined before starting radiotherapy (RTx). Other assessments were done 2, 6, and 12 months after RTx in almost all patients and at 18 months in 4 patients. Generalized estimating equations (GEE) were used to estimate population averaged effects at the different treatment and follow-up time points. Moreover, SCE and MN baseline values in patients were compared with those of a control group of 12 healthy women. A significant difference emerged between patients and healthy controls (P<0.0001 for SCE and P<0.0003 for MN; Mann-Whitney test); SCE increased significantly after CTx and MN increased significantly after RTx. In the GEE model, the smoking habit was associated with increased SCE in patients treated with CTx; age significantly affected MN frequencies. Both MN and SCE frequencies are increased in breast cancer patients and are indicators of CTx and RTx damage, respectively. The increased SCE levels in patients treated with CTx may be due to a synergic effect of smoking and chemotherapy.

Inter-relation of apoptosis and DNA double-strand breaks in patients with multiple primary cancers

Since the development of multiple primary cancers in an individual is considered an unlikely event, it is suspected that a defect in DNA repair or apoptosis is the underlying cause for some of these patients. Therefore, this study was based on the hypothesis that such patients have increased remaining DNA double-strand breaks (DSBs) and reduced levels of apoptosis after in vitro irradiation. To investigate these mechanisms in cancer patients, 19 with multiple primary cancers were selected out of 25 121 cancer patients. For inclusion in this study, patients had to present with first malignancy at an early age, have a positive family history of cancer and no risk factors. The exclusion criteria were recurrence of cancer or metastasis, haematological tumours and tumours possibly connected to a patient risk factor such as smoking or drinking. Their peripheral blood lymphocytes were tested for proper repair of DNA DSBs and apoptosis after in vitro irradiation. DSBs were measured using constant field gel electrophoresis at 0, 8 and 24 h after irradiation. Apoptotic rates were determined at 24, 48 and 72 h after irradiation using the TUNEL assay. We found that patients' lymphocytes had significantly more initial DNA DSBs compared with controls, but there was no difference in the number of remaining DNA DSBs. Apoptotic rates of lymphocytes were only slightly lower in patients than in controls. These findings show that there are limited differences between patients with multiple cancers and healthy individuals. However, we found a trend towards an inverse correlation between remaining DNA DSBs and apoptotic rates in patients' lymphocytes. This is indicative of DNA DSBs persisting in patients' cells, presumably leading to a higher level of stable chromosomal aberrations that may contribute to tumour formation.

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.

Persistence of translocation frequencies in blood lymphocytes following radiotherapy: implications for retrospective radiation biodosimetry

Chromosome aberration analysis using a G-banding technique was performed on peripheral blood lymphocyte cultures from eight individuals over a 5 year period following therapeutic radiation exposure. Samples were placed in three time periods comprising 0-12, 12-36 and 36-60 months post-treatment. The group was heterogeneous with respect to exposure and this resulted in wide differences in initial total translocation yields. Total translocation frequencies declined in seven of the eight cases, reaching significance in four cases. This decline was attributed to a decrease in cells, which in addition to translocations, also contained aberrations such as dicentrics which resulted in them being unstable. In all eight cases, when only stable cells were considered, no significant differences were observed in translocation frequencies between the different time periods post-treatment. Thus, although the frequency of translocations in stable cells is persistent over time, extrapolating to total initial yield, and using this to equate to dose, is not possible in cases where the exposure has been high and non-homogeneous. In practice, retrospective biological dosimetry is more often required in cases of historical, usually protracted, exposures which will have been essentially uniform and not of a sufficiently high dose for many cells to have acquired more than one aberration. In such cases the frequency of translocations observed some years after the exposure can be assumed to reflect induced frequencies and be used for dose estimation.

Lymph nodes in the irradiated field influence the yield of radiation-induced chromosomal aberrations in lymphocytes from breast cancer patients

PURPOSE

To measure chromosomal aberrations in blood lymphocytes from breast cancer patients treated with radiotherapy after quadrantectomy or tumorectomy.

METHODS AND MATERIALS

Twenty-two breast cancer patients treated with breast-conserving surgery and radiation were evaluated. Adjuvant chemotherapy was also given to 9 patients. Blood samples were obtained before radiotherapy, after about one-half of the fractions, and at the end of the treatment of the whole breast (50 Gy). Chromosome aberrations in peripheral blood lymphocytes were measured using chemical-induced premature chromosome condensation combined with fluorescence in situ hybridization.

RESULTS

Radiation treatment produced a significant increase in the yield of chromosomal aberrations. A large interindividual variability was observed. The variability was not related to field size, previous chemotherapy, or treatment morbidity. Chromosome aberrations in lymphocytes at the end of the treatment were significantly higher in the group of patients with no lymph nodes surgically removed before the treatment than in the group of patients with more than 10 lymph nodes removed.

CONCLUSION

The number of lymph nodes within the radiation field is an important factor affecting the yield of radiation-induced chromosomal aberrations in breast cancer patients.