Correlation between radiation dose and p53 protein expression levels in human lymphocytes

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.

The role of radiation induced oxidative stress as a regulator of radio-adaptive responses

Purpose: Various sources of radiation including radiofrequency, electromagnetic radiation (EMR), low- dose X-radiation, low-level microwave radiation and ionizing radiation (IR) are indispensable parts of modern life. In the current review, we discussed the adaptive responses of biological systems to radiation with a focus on the impacts of radiation-induced oxidative stress (RIOS) and its molecular downstream signaling pathways.Materials and methods: A comprehensive search was conducted in Web of Sciences, PubMed, Scopus, Google Scholar, Embase, and Cochrane Library. Keywords included Mesh terms of "radiation," "electromagnetic radiation," "adaptive immunity," "oxidative stress," and "immune checkpoints." Manuscripts published up until December 2019 were included.Results: RIOS induces various molecular adaptors connected with adaptive responses in radiation exposed cells. One of these adaptors includes p53 which promotes various cellular signaling pathways. RIOS also activates the intrinsic apoptotic pathway by depolarization of the mitochondrial membrane potential and activating the caspase apoptotic cascade. RIOS is also involved in radiation-induced proliferative responses through interaction with mitogen-activated protein kinases (MAPks) including p38 MAPK, ERK, and c-Jun N-terminal kinase (JNK). Protein kinase B (Akt)/phosphoinositide 3-kinase (PI3K) signaling pathway has also been reported to be involved in RIOS-induced proliferative responses. Furthermore, RIOS promotes genetic instability by introducing DNA structural and epigenetic alterations, as well as attenuating DNA repair mechanisms. Inflammatory transcription factors including macrophage migration inhibitory factor (MIF), nuclear factor κB (NF-κB), and signal transducer and activator of transcription-3 (STAT-3) paly major role in RIOS-induced inflammation.Conclusion: In conclusion, RIOS considerably contributes to radiation induced adaptive responses. Other possible molecular adaptors modulating RIOS-induced responses are yet to be divulged in future studies.

DNA damage and the bystander response in tumor and normal cells exposed to X-rays

Monolayer and suspension cultures of tumor (BMG-1, CCRF-CEM), normal (AG1522, HADF, lymphocytes) and ATM-mutant (GM4405) human cells were exposed to X-rays at doses used in radiotherapy (high dose and high dose-rate) or radiological imaging (low dose and low dose-rate). Radiation-induced DNA damage, its persistence, and possible bystander effects were evaluated, based on DNA damage markers (γ-H2AX, p53^ser15) and cell-cycle-specific cyclins (cyclin B1 and cyclin D1). Dose-dependent DNA damage and a dose-independent bystander response were seen after exposure to high dose and high dose-rate radiation. The level of induced damage (expression of p53^ser15, γ-H2AX) depended on ATM status. However, low dose and dose-rate exposures neither increased expression of marker proteins nor induced a bystander response, except in the CCRF-CEM cells. Bystander effects after high-dose irradiation may contribute to stochastic and deterministic effects. Precautions to protect unexposed regions or to inhibit transmission of DNA damage signaling might reduce radiation risks.

Active caspase-3 expression levels as bioindicator of individual radiosensitivity

Several molecules and events involved in cell response to radiation-induced damage have been investigated towards a personalized radiotherapy. Considering the importance of active caspase-3 in the proteolytic cascade that ensures radiation-induced apoptosis execution, this research was designed to evaluate the expression levels of this protein as a bioindicator of individual radiosensitivity. Peripheral blood samples of 10 healthy individuals were gamma-irradiated (cobalt-60 source) with 1, 2 and 4 Gy (control: non-irradiated samples), and active caspase-3 expression levels were measured in lymphocytes, by flow cytometry, ex vivo and after different times of in vitro incubation (24, 48 and 72 hours). Short-term incubation of 24 h was the most adequate condition to evidence correlations between dose radiation and active caspase-3 expression. For each radiation dose, it was observed a significant inter-individual variation in active caspase-3 expression intensity, suggesting that this parameter may be suitable for evidence individual radiosensitivity. The methodology presented and discussed in this work may help to predict healthy tissues response to radiation exposure toward the better patient outcome.