[Biomarkers of radiation-induced DNA repair processes]

Early Biomarkers Associated with P53 Signaling for Acute Radiation Injury

Accurate dose assessment within 1 day or even 12 h after exposure through current methods of dose estimation remains a challenge, in response to a large number of casualties caused by nuclear or radiation accidents. P53 signaling pathway plays an important role in DNA damage repair and cell apoptosis induced by ionizing radiation. The changes of radiation-induced P53 related genes in the early stage of ionizing radiation should compensate for the deficiency of lymphocyte decline and γ-H2AX analysis as novel biomarkers of radiation damage. Bioinformatic analysis was performed on previous data to find candidate genes from human peripheral blood irradiated in vitro. The expression levels of candidate genes were detected by RT-PCR. The expressions of screened DDB2, AEN, TRIAP1, and TRAF4 were stable in healthy population, but significantly up-regulated by radiation, with time specificity and dose dependence in 2–24 h after irradiation. They are early indicators for medical treatment in acute radiation injury. Their effective combination could achieve a more accurate dose assessment for large-scale wounded patients within 24 h post exposure. The effective combination of p53-related genes DDB2, AEN, TRIAP1, and TRAF4 is a novel biodosimetry for a large number of people exposed to acute nuclear accidents.

Disulfiram Alone Functions as a Radiosensitizer for Pancreatic Cancer Both In Vitro and In Vivo

The prognosis of pancreatic cancer remains very poor worldwide, partly due to the lack of specificity of early symptoms and innate resistance to chemo-/radiotherapy. Disulfiram (DSF), an anti-alcoholism drug widely used in the clinic, has been known for decades for its antitumor effects when simultaneously applied with copper ions, including pancreatic cancer. However, controversy still exists in the context of the antitumor effects of DSF alone in pancreatic cancer and related mechanisms, especially in its potential roles as a sensitizer for cancer radiotherapy. In the present study, we focused on whether and how DSF could facilitate ionizing radiation (IR) to eliminate pancreatic cancer. DSF alone significantly suppressed the survival of pancreatic cancer cells after exposure to IR, both in vitro and in vivo. Additionally, DSF treatment alone caused DNA double-strand breaks (DSBs) and further enhanced IR-induced DSBs in pancreatic cancer cells. In addition, DSF alone boosted IR-induced cell cycle G2/M phase arrest and apoptosis in pancreatic cancer exposed to IR. RNA sequencing and bioinformatics analysis results suggested that DSF could trigger cell adhesion molecule (CAM) signaling, which might be involved in its function in regulating the radiosensitivity of pancreatic cancer cells. In conclusion, we suggest that DSF alone may function as a radiosensitizer for pancreatic cancer, probably by regulating IR-induced DNA damage, cell cycle arrest and apoptosis, at least partially through the CAM signaling pathway.

Two novel mutations in the MCM8 gene shared by two Chinese siblings with primary ovarian insufficiency and short stature

BACKGROUND

Minichromosome maintenance complex component 8 (MCM8) is responsible for homologous recombination and DNA double-strand breaks (DSBs) repair and is the cause of primary ovarian insufficiency (POI), which is seldom diagnosed in adolescents and children.

METHODS

Whole-exome sequencing was performed in a 13-year-old girl, and Sanger sequencing was used to identify potentially pathogenic variants in her sister (aged 6 years and 7 months) and parents. To identify potential pathogenic mutations, DSBs were induced by mitomycin C (MMC), and the DNA repair capacity was evaluated by the histone H2AX phosphorylation level.

RESULTS

Two novel mutations of MCM8, i.e., c.724T>C (p.C242R) and c.1334C>A (p.S445*), were identified in a 13-year-old girl with POI who exhibited disappeared bilateral ovaries and short stature (height standard difference score [HtSDS] = -3.05), and her sister (aged 6 years and 7 months) with progressive POI whose ovary size decreased from normal to unclear and height growth gradually slowed. In the functional experiments, compared with the wild-type, HeLa cells overexpressing mutant p.C242R and p.S445* showed a higher sensitivity to MMC. Furthermore, the mutant p.S445* has a more deleterious effect on DNA damage repair.

CONCLUSION

Our results reveal that affected children with the novel pathogenetic mutations p.C242R and p.S445* in the MCM8 gene are characterized by POI, short stature, cancer susceptibility, and genomic instability.

Biomarkers of Brain Damage Induced by Radiotherapy

Radiotherapy remains currently a critical component for both primary and metastatic brain tumors either alone or in combination with surgery, chemotherapy, and molecularly targeted agents, while it could cause simultaneously normal brain tissue injury leading to serious health consequences, that is, development of cognitive impairments following cranial radiotherapy is considered as a critical clinical disadvantage especially for the whole brain radiotherapy. Biomarkers can help to detect the accurate physiology or conditions of patients with brain tumor and develop effective treatment procedures for these patients. In the near future, biomarkers will become one of the prime driving forces of cancer treatment. In this minireview, we analyze the documented work on the acute brain damage and late consequences induced by radiotherapy, identify the biomarkers, in particular, the predictive biomarkers for the damage, and summarize the biological significance of the biomarkers. It is expected that translation of these research advance to radiotherapy would assist stratifying patients for optimized treatment and improving therapeutic efficacy and the quality of life.

The effect of prophylactic oral vitamin C use on DNA double-strand breaks after abdominal contrast-enhanced CT: A preliminary study

PURPOSE

To investigate the protective effect of oral Vitamin C on DNA double-strand breaks (DSBs) after abdominal contrast-enhanced CT examination.

MATERIALS AND METHODS

Sixty patients undergoing abdominal multiphase contrast-enhanced CT were divided into control group (n = 30) and prevention group (n = 30). Patients in the prevention group were orally administered 1 g Vitamin C 30-120 minutes prior to CT examination. Blood samples were obtained prior to and 5 min following CT examination for each subject. γ-H2AX foci representing DSBs in the nucleus of lymphocytes were marked by fluorescent markers. Change in γ-H2AX foci/cell was compared through Student t-tests or ANOVA testing. The relationship between physical parameters and increase in γ-H2AX foci was analyzed through Pearson or Spearman correlation analysis.

RESULTS

The mean increase in γ-H2AX was 0.49 foci /cell in the control group and 0.19 foci/cell in the prevention group (p < 0.001), corresponding to a 61% reduction in the mean increase in γ-H2AX foci in the prevention group compared to the control group. In the prevention group, increase in γ-H2AX foci/cell positively correlated with dose length product and volume CT dose index (r = 0.449 and 0.403, respectively; both p < 0.05). No difference in the increase in γ-H2AX foci/cell was found between the different time interval subgroups of 30, 60, and 120 min between Vitamin C administration and CT examination (p > 0.05).

CONCLUSION

Oral Vitamin C can significantly reduce the level of DSBs after abdominal contrast-enhanced CT examination and is a simple and effective method to decrease DNA damage.

Looking for solutions: vision and a call-for-attention for radiation research scientists

Purpose: The concept of benefit-risk assessment has often been propagated for clinical professionals for deciding the radiological exam for the patient. A detailed look into how to use this concept leads to several unanswered questions. The purpose of this article is to bring forth questions which have remained unanswered for several decades. These questions pertain to our inability to provide needed information to physicians for making benefit-risk assessment for deciding a frequent imaging modality like the computed tomography (CT) such as non-applicability of risk estimates to an individual patient, the concept of cumulative risk at low doses, accounting for the time gap between series of CT scans, risk variation with age, gender and disease condition. In the absence of concrete information on these, it becomes essentially benefit assessment rather than benefit-risk. The article also provides a motivation to think that there are a large number of patients getting exposed every year to radiation doses over 100 mSv of effective dose and several tens of mGy of organ doses. This may provide a very large cohort for radiation effect studies. Further, a series of ideas are presented as a vision for future studies. Conclusions: The article emphasizes the need to create a research agenda to deal with day-to-day questions faced in medical practice and provides a call-for-attention. Further, it provides some challenging ideas as outside of the box thinking points that may provide research direction for future years.