Investigating micronucleus assay applicability for prediction of normal tissue intrinsic radiosensitivity in gynecological cancer patients

Prediction of the Acute or Late Radiation Toxicity Effects in Radiotherapy Patients Using Ex Vivo Induced Biodosimetric Markers: A Review

A search for effective methods for the assessment of patients' individual response to radiation is one of the important tasks of clinical radiobiology. This review summarizes available data on the use of ex vivo cytogenetic markers, typically used for biodosimetry, for the prediction of individual clinical radiosensitivity (normal tissue toxicity, NTT) in cells of cancer patients undergoing therapeutic irradiation. In approximately 50% of the relevant reports, selected for the analysis in peer-reviewed international journals, the average ex vivo induced yield of these biodosimetric markers was higher in patients with severe reactions than in patients with a lower grade of NTT. Also, a significant correlation was sometimes found between the biodosimetric marker yield and the severity of acute or late NTT reactions at an individual level, but this observation was not unequivocally proven. A similar controversy of published results was found regarding the attempts to apply G2- and γH2AX foci assays for NTT prediction. A correlation between ex vivo cytogenetic biomarker yields and NTT occurred most frequently when chromosome aberrations (not micronuclei) were measured in lymphocytes (not fibroblasts) irradiated to relatively high doses (4-6 Gy, not 2 Gy) in patients with various grades of late (not early) radiotherapy (RT) morbidity. The limitations of existing approaches are discussed, and recommendations on the improvement of the ex vivo cytogenetic testing for NTT prediction are provided. However, the efficiency of these methods still needs to be validated in properly organized clinical trials involving large and verified patient cohorts.

Comparing Lymphocyte Radiosensitivity of Prostate Cancer Patients with Healthy Donors Using Micronuclei and Chemical Premature Chromosome Condensation Tests

Background:

Cytogenetic tests are usually used for diagnosing predisposed individuals to cancer by determining their lymphocyte radiosensitivity.

Objective:

To determine the potential role of radiosensitivity in predisposition of prostate cancer by comparing lymphocyte radiosensitivity of prostate cancer patients with healthy donors.

Materials and Methods:

In this experimental study, the blood samples of 10 prostate cancer patients and 10 healthy donors were irradiated to 0.25, 0.5, 1, 2, 4 and 6 Gy ionizing radiation produced by a 6MV Linac. One sample of each group receiving no radiation was regarded as the background. The micronuclei (MN) and chemical premature chromosome condensation (PCC) cytogenetic tests were performed on all samples and the numbers of MN and PCC rings were scored. Dose-response curves were plotted for both healthy and cancerous groups with two tests.

Results:

There was a significant difference between the numbers of MN within each group due to different levels of radiation doses. There was also a significant difference between the two groups in all identical doses, with the exception of 6 Gy. The chemical PCC test indicated a significant difference between the scored PCC rings in each group at doses higher than 0.25 Gy. However, no differences were noted between the healthy donors and prostate cancer patients receiving the same level of doses.

Conclusion:

MN test can be considered as a reliable indicator of predisposition of prostate cancer. On the other hand, the chemical PCC test could not differentiate between healthy donors and prostate cancer patients at the dose range examined in this study.

Micronucleus assay for predicting side effects of radiotherapy for cervical cancer

Radiotherapy (RT) is an important treatment for cervical cancer. The quality of life of patients undergoing RT may be compromised during and following treatment by nausea, diarrhea, vomiting, burns, erythema and fistula. Cytokinesis-block micronucleus (CBMN) assays may be useful for predicting adverse effects of RT for cancer. The CBMN test is easy to perform and is reproducible for screening subjects exposed to ionizing radiation. We investigated the use of the frequency of micronuclei (MN) from peripheral blood samples, irradiated in vitro, as a possible biomarker to predict the side effects of RT in patients with cervical cancer. We used 10 patients with cervical cancer receiving RT and chemotherapy. We found a strong relation between the frequency of MN and the appearance of acute side effects of RT for cervical cancer. We suggest that the methodology presented here may be useful for predicting side effects of RT for patients affected by cervical cancer and who have undergone chemotherapy.

Micronucleus Assay: The State of Art, and Future Directions

During almost 40 years of use, the micronucleus assay (MN) has become one of the most popular methods to assess genotoxicity of different chemical and physical factors, including ionizing radiation-induced DNA damage. In this minireview, we focus on the position of MN among the other genotoxicity tests, its usefulness in different applications and visibility by international organizations, such as International Atomic Energy Agency, Organization for Economic Co-operation and Development and International Organization for Standardization. In addition, the mechanism of micronuclei formation is discussed. Finally, foreseen directions of the MN development are pointed, such as automation, buccal cells MN and chromothripsis phenomenon.

The incidence of inflammation among patients suffering from cervix cancer with positive beta haemolytic streptococci cultures from genital tract

Aim

The main goal of this investigation was to evaluate the influence of positive beta haemolytic streptococci culture from the genital tract on patients receiving radiation therapy who suffer from cervical cancer. The other aim was to observe radiation therapy complications.

Background

Group B streptococci (GBS), group C streptococci (GCS) and group G streptococci (GGS) have been described as frequent invasive pathogens in elderly patients, often in association with underlying medical conditions including immunodeficiency and cancer.

Materials and methods

In the years 2006-2015, vaginal swabs from 452 patients were examined. A total of 118 women with positive beta haemolytic streptococci (BHS) groups A, B, C, F, G cultures were analysed, of whom 111 were diagnosed with cervix cancer of IB to IVA degree according to the FIGO 1988 clinical classification.

Results

Of the 452 patients suffering from cervix cancer 26.1% were positive for A, B, C, F or G group BHS isolated from the genital tract. All of the 114 examined strains were sensitive to beta-lactam antibiotics. The antimicrobials for which resistance was noted were erythromycin, clindamycin, ciprofloxacin and tetracycline.

Conclusions

Positive cultures of BHS from the genital tract were demonstrated to occur in patients with cervix cancer. Complications were found during radiotherapy in 30 (27%) of these patients, including 20 (18%) patients suffering from clinical symptoms of inflammation. When beta-lactam antibiotics are not recommended because of allergy, sensitivity tests to other drugs are necessary.

Dependence of micronuclei assay on the depth of absorbed dose

AIM

The purpose of the present study is to investigate the dependence of micronuclei response on the depth of absorbed dose.

BACKGROUND

One of the most common cytogenetic methods used for radiation dosimetry is micronuclei (MN). Being less complex and faster than other methods are two remarkable advantages of the MN method which make it suitable for monitoring of population. In biological dosimetry based on the micronuclei method, the investigation into the dependence of response on the depth in which dose is absorbed is significant, though has received less attention so far.

MATERIALS AND METHODS

Blood samples were poured in separate vials to be irradiated at different depths using a linear accelerator system.

RESULTS

According to the results, MN, as a function of the absorbed dose, had the best fitness with the linear-quadratic model at all depths. Furthermore, the results showed the dependence of MN response on the depth of absorbed dose. For doses up to 2 Gy, the maximum difference from the reference depth of 1.5 cm was related to the depth of 10 cm; however, by increasing the absorbed dose, the response associated with the depth of 20 cm showed the maximum deviation from the reference depth.

CONCLUSIONS

Consequently, it is necessary to apply a correction factor to the biological dosimetry. The correction factor is dependent on the depth and the absorbed dose.

Assessment of Correlation between Chromosomal Radiosensitivity of Peripheral Blood Lymphocytes after In vitro Irradiation and Normal Tissue Side Effects for Cancer Patients Undergoing Radiotherapy

Patients receiving identical radiation treatments experience different effects, from undetectable to severe, on normal tissues. A crucial factor of radiotherapy related side effects is individual radiosensitivity. It is difficult to spare surrounding normal tissues delivering radiation to cancer cells during radiotherapy. Therefore, it may be useful to develop a simple routine cytogenetic assay which would allow the screening of a large number of individuals for radiosensitivity optimizing tumor control rates and minimizing severe radiotherapy effects with possibility to predict risk level for developing more severe early normal tissue adverse events after irradiation. This study was conducted to assess the correlation between in vitro radiosensitivity of peripheral blood lymphocytes from cancer patients who are undergoing radiotherapy using the cytokinesis-block micronucleus (CBMN), G2 chromosomal radiosensitivity assays, and normal tissue acute side effects. The CBMN and G2 chromosomal radiosensitivity assays were performed on blood samples taken from cancer patients before radiotherapy, after first fractionation, and after radiotherapy. Acute normal tissue reactions were graded according to the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer. This study suggests that there is a correlation between higher frequency of micronuclei after in vitro irradiation of blood samples and higher degree of normal tissue reactions. In addition, higher number of chromatid breaks was observed in patients with more severe normal tissue reactions. This pilot study included only 5 cancer patients, and therefore, further studies with a bigger cohort are required to identify radiosensitive patients.

A flow cytometry assay that measures cellular sensitivity to DNA-damaging agents, customized for clinical routine laboratories

OBJECTIVES

The clonogenic assay examines cell sensitivity to toxic agents and has been shown to correlate with normal tissue sensitivity to radiotherapy in cancer patients. The clonogenic assay is not clinically applicable due to its intra-individual variability and the time frame of the protocol. We aimed to develop a clinically applicable assay that correlated with the clonogenic assay.

DESIGN AND METHODS

We have developed a faster and less labor-intensive cell division assay (CD assay) using flow cytometry and incorporation of a fluorescent thymidine analogue. The CD assay was calibrated to the clonogenic assay and optimized for peripheral blood lymphocytes.

RESULTS

Following ionizing radiation of primary human skin fibroblasts, the four-day CD assay gave similar results as the 14-day clonogenic survival assay. In lymphocytes isolated from patient blood samples, the CD assay was able to detect increased radiosensitivity in ataxia telangiectasia patients and increased radiosensitivity after in vitro treatment with DNA-PK and ATM inhibitors. The CD assay found a variation in the intrinsic radiosensitivity of lymphocytes isolated from healthy control samples. The CD assay was able to measure the anti-proliferation effect of different chemotherapeutic drugs in lymphocytes.

CONCLUSIONS

Our results indicate that the CD assay is a fast and reliable method to measure the anti-proliferation effect of DNA-damaging agents with a potential to find the most sensitive patients in the work-up before cancer treatment.

Chromosomal radiosensitivity of human immunodeficiency virus positive/negative cervical cancer patients in South Africa

Cervical cancer is the second most common cancer amongst South African women and is the leading cause of cancer-associated mortality in this region. Several international studies on radiation‑induced DNA damage in lymphocytes of cervical cancer patients have remained inconclusive. Despite the high incidence of cervical cancer in South Africa, and the extensive use of radiotherapy to treat it, the chromosomal radiosensitivity of South African cervical cancer patients has not been studied to date. Since a high number of these patients are human immunodeficiency virus (HIV)‑positive, the effect of HIV infection on chromosomal radiosensitivity was also investigated. Blood samples from 35 cervical cancer patients (20 HIV‑negative and 15 HIV‑positive) and 20 healthy controls were exposed to X‑rays at doses of 6 MV of 2 and 4 Gy in vitro. Chromosomal radiosensitivity was assessed using the micronucleus (MN) assay. MN scores were obtained using the Metafer 4 platform, an automated microscopic system. Three scoring methods of the MNScore module of Metafer were applied and compared. Cervical cancer patients had higher MN values than healthy controls, with HIV‑positive patients having the highest MN values. Differences between groups were significant when using a scoring method that corrects for false positive and false negative MN. The present study suggested increased chromosomal radiosensitivity in HIV-positive South African cervical cancer patients.