Differential Expression of ATM, NF-KB, PINK1 and Foxo3a in Radiation-Induced Basal Cell Carcinoma

Research in normal tissue radiobiology is in continuous progress to assess cellular response following ionizing radiation exposure especially linked to carcinogenesis risk. This was observed among patients with a history of radiotherapy of the scalp for ringworm who developed basal cell carcinoma (BCC). However, the involved mechanisms remain largely undefined. We performed a gene expression analysis of tumor biopsies and blood of radiation-induced BCC and sporadic patients using reverse transcription-quantitative PCR. Differences across groups were assessed by statistical analysis. Bioinformatic analyses were conducted using miRNet. We showed a significant overexpression of the FOXO3a, ATM, P65, TNF-α and PINK1 genes among radiation-induced BCCs compared to BCCs in sporadic patients. ATM expression level was correlated with FOXO3a. Based on receiver-operating characteristic curves, the differentially expressed genes could significantly discriminate between the two groups. Nevertheless, TNF-α and PINK1 blood expression showed no statistical differences between BCC groups. Bioinformatic analysis revealed that the candidate genes may represent putative targets for microRNAs in the skin. Our findings may yield clues as to the molecular mechanism involved in radiation-induced BCC, suggesting that deregulation of ATM-NF-kB signaling and PINK1 gene expression may contribute to BCC radiation carcinogenesis and that the analyzed genes could represent candidate radiation biomarkers associated with radiation-induced BCC.

Comprehensive analysis for detecting radiation-specific molecules expressed during radiation-induced rat thyroid carcinogenesis

Although the association between radiation exposure and thyroid carcinogenesis is epidemiologically evident, 'true' radiation-induced cancers cannot be identified from biological evidence of radiation-associated cases. To assess the individual risk for thyroid cancer due to radiation exposure, we aimed to identify biomarkers that are specifically altered during thyroid carcinogenesis after irradiation in a time-dependent manner in an animal model. Thyroid glands were obtained from rats (n = 175) at 6-16 months after local X-ray (0.1-4 Gy) irradiation of the neck at 7 weeks of age. The gene expression profile in thyroid glands was comprehensively analyzed using RNA microarray. Subsequently, the expression levels of the genes of interest were verified using droplet digital PCR (ddPCR). The expression level of candidate genes as biomarkers for irradiated thyroid was examined in a randomized, controlled, double-blind validation study (n = 19) using ddPCR. The incidence of thyroid cancer increased in a dose- and time-dependent manner and was 33% at 16 months after irradiation with 4 Gy. The Ki-67 labeling index in non-tumorous thyroid was significantly higher in the exposed group than in the control. Comprehensive analysis identified radiation-dependent alteration in 3329 genes. Among them, ddPCR revealed a stepwise increase in CDKN1A expression from early pre-cancerous phase in irradiated thyroid compared to that in the control. The irradiated thyroids were accurately distinguished (positive predictive value 100%, negative predictive value 69%) using 11.69 as the cut-off value for CDKN1A/β-actin. Thus, CDKN1A expression can be used as a biomarker for irradiated thyroid glands at the pre-cancerous phase.

Significant association between 53 BP1 expression and grade of intraepithelial neoplasia of esophagus: Alteration during esophageal carcinogenesis

BACKGROUND

Abnormal DNA damage response (DDR) leads to genomic instability and carcinogenesis. P53-binding protein 1 (53 BP1), a DDR molecule, is known to accumulate at the sites of DNA double-strand breaks. The aim of this study was to analyze the expression pattern of 53 BP1-nuclear foci (NF) in esophageal neoplasms in order to visualize the state of DDR in esophageal carcinogenesis and to clarify its significance in the molecular pathology of the disease.

METHODS

A total of 61 lesions from 22 surgically resected samples of esophageal cancer, including histologically normal squamous epithelium, low-grade intraepithelial neoplasia (LG-IN), high-grade intraepithelial neoplasia (HG-IN), carcinoma in situ (CIS), and invasive squamous cell carcinoma (SCC), were included in the study. 53 BP1 and Ki-67 expression were analyzed by double-labeled immunofluorescence.

RESULTS

The number of discrete 53 BP1-NF increased as the tumor progressed from normal epithelium through LG-IN, HG-IN, CIS, and SCC. 53 BP1-NF larger than 1 μm in diameter (large foci), indicating intensive DDR, also showed a stepwise increase during the progression of carcinogenesis. Of note, large foci of 53 BP1 were found in significantly higher numbers in HG-IN than in LG-IN. Furthermore, localization of 53 BP1-NF in Ki-67-positive cells, indicating the abnormal timing of DDR, also increased with malignancy progression.

CONCLUSIONS

53 BP1-NF accumulation increases during cancer progression from LG-IN to HG-IN to CIS to SCC. Detection of 53 BP1-NF by immunofluorescence, especially large foci, is a feasible method of estimating DNA instability and the malignant potential of esophageal intraepithelial neoplasia.

Interplay Between the Immunohistochemical Expression of P53 and the Proliferation Index in the Keratinocyte Tumors of the Skin

P53 is important for cell cycle regulation, and its overexpression is seen in malignant tumors. We examined correlation between p53 expression and cell proliferation, and its role in the pathogenesis of keratinocyte skin tumors. We used biopsies from patients with squamous cell carcinoma, actinic keratosis and keratoacanthoma. We examined crosssections stained with HE and using anti-cytokeratin, antip53 and anti-Ki67 antibodies.

Expression of p53 is found in 87, 85% of SCC, in 83. 3% of AK and 13. 4% KA. The high index of p53 expression was higher in SCC and AK compared to KA. We also observed a positive correlation between the expression of p53 and localization of the tumors. The largest proportion of subjects with AK and SCC has a high index of p53 expression on photoexposed region. We also observed that p53 expression correlates with age whereby in AK p53 expression increases with age. The high index of proliferation is most frequent in SCC and KA. Also at AK we found a strong correlation between a moderate proliferation index and tumor localization in photoexposed region. Between the proliferation index and p53 expression we observed a significant positive correlation only in SCC.

Proliferation index and the expression of p53 are useful for the differentiation of precursor keratinocyte lesions and skin carcinoma. High p53 expression has been associated with the aging and significantly correlates with the exposure to UV radiation in SCC and AK. High expression of p53 in AK and SCC supports the importance of this oncoprotein in carcinogenesis of the skin.

ICRP Publication 131: Stem Cell Biology with Respect to Carcinogenesis Aspects of Radiological Protection

This report provides a review of stem cells/progenitor cells and their responses to ionising radiation in relation to issues relevant to stochastic effects of radiation that form a major part of the International Commission on Radiological Protection's system of radiological protection. Current information on stem cell characteristics, maintenance and renewal, evolution with age, location in stem cell 'niches', and radiosensitivity to acute and protracted exposures is presented in a series of substantial reviews as annexes concerning haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. This foundation of knowledge of stem cells is used in the main text of the report to provide a biological insight into issues such as the linear-no-threshold (LNT) model, cancer risk among tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age. Knowledge of the biology and associated radiation biology of stem cells and progenitor cells is more developed in tissues that renew fairly rapidly, such as haematopoietic tissue, intestinal mucosa, and epidermis, although all the tissues considered here possess stem cell populations. Important features of stem cell maintenance, renewal, and response are the microenvironmental signals operating in the niche residence, for which a well-defined spatial location has been identified in some tissues. The identity of the target cell for carcinogenesis continues to point to the more primitive stem cell population that is mostly quiescent, and hence able to accumulate the protracted sequence of mutations necessary to result in malignancy. In addition, there is some potential for daughter progenitor cells to be target cells in particular cases, such as in haematopoietic tissue and in skin. Several biological processes could contribute to protecting stem cells from mutation accumulation: (a) accurate DNA repair; (b) rapidly induced death of injured stem cells; (c) retention of the DNA parental template strand during divisions in some tissue systems, so that mutations are passed to the daughter differentiating cells and not retained in the parental cell; and (d) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the niche. DNA repair mainly occurs within a few days of irradiation, while stem cell competition requires weeks or many months depending on the tissue type. The aforementioned processes may contribute to the differences in carcinogenic radiation risk values between tissues, and may help to explain why a rapidly replicating tissue such as small intestine is less prone to such risk. The processes also provide a mechanistic insight relevant to the LNT model, and the relative and absolute risk models. The radiobiological knowledge also provides a scientific insight into discussions of the dose and dose-rate effectiveness factor currently used in radiological protection guidelines. In addition, the biological information contributes potential reasons for the age-dependent sensitivity to radiation carcinogenesis, including the effects of in-utero exposure.

Human epidermal stem cells: Role in adverse skin reactions and carcinogenesis from radiation

In human skin, keratinopoiesis is based on a functional hierarchy among keratinocytes, with rare slow-cycling stem cells responsible for the long-term maintenance of the tissue through their self-renewal potential, and more differentiated daughter progenitor cells actively cycling to permit epidermal renewal and turn-over every month. Skin is a radio-responsive tissue, developing all types of radiation damage and pathologies, including early tissue reactions such as dysplasia and denudation in epidermis, and later fibrosis in the dermis and acanthosis in epidermis, with the TGF-beta 1 pathway as a known master switch. Also there is a risk of basal cell carcinoma, which arises from epidermal keratinocytes, notably after oncogenic events in PTCH1 or TP53 genes. This review will cover the mechanisms of adverse human skin reactions and carcinogenesis after various types of exposures to ionizing radiation, with comparison with animal data when necessary, and will discuss the possible role of stem cells and their progeny in the development of these disorders. The main endpoints presented are basal cell intrinsic radiosensitivity, genomic stability, individual factors of risk, dose specific responses, major molecular pathways involved and the cellular origin of skin reactions and cancer. Although major advances have been obtained in recent years, the precise implications of epidermal stem cells and their progeny in these processes are not yet fully characterized.

Ionizing Radiation Exposure and Basal Cell Carcinoma Pathogenesis

This commentary summarizes studies showing risk of basal cell carcinoma (BCC) development in relationship to environmental, occupational and therapeutic exposure to ionizing radiation (IR). BCC, the most common type of human cancer, is driven by the aberrant activation of hedgehog (Hh) signaling. Ptch, a tumor suppressor gene of Hh signaling pathway, and Smoothened play a key role in the development of radiation-induced BCCs in animal models. Epidemiological studies provide evidence that humans exposed to radiation as observed among the long-term, large scale cohorts of atomic bomb survivors, bone marrow transplant recipients, patients with tinea capitis and radiologic workers enhances risk of BCCs. Overall, this risk is higher in Caucasians than other races. People who were exposed early in life develop more BCCs. The enhanced IR correlation with BCC and not other common cutaneous malignancies is intriguing. The mechanism underlying these observations remains undefined. Understanding interactions between radiation-induced signaling pathways and those which drive BCC development may be important in unraveling the mechanism associated with this enhanced risk. Recent studies showed that Vismodegib, a Smoothened inhibitor, is effective in treating radiation-induced BCCs in humans, suggesting that common strategies are required for the intervention of BCCs development irrespective of their etiology.

Basal cell carcinoma of the skin (part 1): epidemiology, pathology and genetic syndromes

Basal cell carcinoma (BCC) is the most common skin cancer worldwide with increasing incidence, but difficult to assess due to the current under registration practice. Despite the low mortality rate, BCC is a cause of great morbidity and an economic burden to health services. There are several risk factors that increase the risk of BCC and partly explain its incidence. Low-penetrance susceptibility alleles, as well as genetic alterations in signaling pathways, namely SHH pathway, also contribute to the carcinogenesis. BCC associate with several genetic syndromes, of which basal cell nevus syndrome is the most common.

56Fe Particle Exposure Results in a Long-Lasting Increase in a Cellular Index of Genomic Instability and Transiently Suppresses Adult Hippocampal Neurogenesis in Vivo

The high-LET HZE particles from galactic cosmic radiation pose tremendous health risks to astronauts, as they may incur sub-threshold brain injury or maladaptations that may lead to cognitive impairment. The health effects of HZE particles are difficult to predict and unfeasible to prevent. This underscores the importance of estimating radiation risks to the central nervous system as a whole as well as to specific brain regions like the hippocampus, which is central to learning and memory. Given that neurogenesis in the hippocampus has been linked to learning and memory, we investigated the response and recovery of neurogenesis and neural stem cells in the adult mouse hippocampal dentate gyrus after HZE particle exposure using two nestin transgenic reporter mouse lines to label and track radial glia stem cells (Nestin-GFP and Nestin-CreER^T2/R26R:YFP mice, respectively). Mice were subjected to ⁵⁶Fe particle exposure (0 or 1 Gy, at either 300 or 1000 MeV/n) and brains were harvested at early (24h), intermediate (7d), and/or long time points (2-3mo) post-irradiation. ⁵⁶Fe particle exposure resulted in a robust increase in 53BP1+ foci at both the intermediate and long time points post-irradiation, suggesting long-term genomic instability in the brain. However, ⁵⁶Fe particle exposure only produced a transient decrease in immature neuron number at the intermediate time point, with no significant decrease at the long time point post-irradiation. ⁵⁶Fe particle exposure similarly produced a transient decrease in dividing progenitors, with fewer progenitors labeled at the early time point but equal number labeled at the intermediate time point, suggesting a recovery of neurogenesis. Notably, ⁵⁶Fe particle exposure did not change the total number of nestin-expressing neural stem cells. These results highlight that despite the persistence of an index of genomic instability, ⁵⁶Fe particle-induced deficits in adult hippocampal neurogenesis may be transient. These data support the regenerative capacity of the adult SGZ after HZE particle exposure and encourage additional inquiry into the relationship between radial glia stem cells and cognitive function after HZE particle exposure.

Effects of radiation on the incidence of prostate cancer among Nagasaki atomic bomb survivors

Atomic bomb survivors have been reported to have an increased risk of some cancers, especially leukemia. However, the risk of prostate cancer in atomic bomb survivors is not known to have been examined previously. This study examined the association between atomic bomb radiation and the incidence of prostate cancer among male Nagasaki atomic bomb survivors. The subjects were classified by distance from the hypocenter into a proximal group (<2 km), a distal group (≥2 km), and an early entrance group (those who entered the region <2 km from the hypocenter within 2 weeks after the explosion). Between 1996 and 2009, 631 new cases of prostate cancer were identified among approximately 18 400 male Nagasaki atomic bomb survivors who were alive in 1996. The Cox proportional hazard model was used to estimate the risk of prostate cancer development, with adjustment for age at atomic bomb explosion, attained age, smoking status, and alcohol consumption. Compared with the distal group, the proximal group had significant increased risks of total, localized, and high-grade prostate cancer (relative risk and 95% confidence interval: 1.51 [1.21-1.89]; 1.80 [1.26-2.57]; and 1.88 [1.20-2.94], respectively). This report is the first known to reveal a significant relationship between atomic bomb radiation and prostate cancer.

Strong association between cancer and genomic instability

After a first wave of radiation-induced chromosomal aberrations, a second wave appears 20-30 cell generations after radiation exposure and persists thereafter. This late effect is usually termed "genomic instability". A better term is "increased genomic instability". This effect has been observed in many cell systems in vitro and in vivo for quite a number of biological endpoints. The radiation-induced increase in genomic instability is apparently a general phenomenon. In the development of cancer, several mutations are involved. With increasing genomic instability, the probability for further mutations is enhanced. Several studies show that genomic instability is increased not only in the cancer cells but also in "normal" cells of cancer patients e.g. peripheral lymphocytes. This has for example been shown in uranium miners with bronchial carcinomas, but also in untreated head and neck cancer patients. The association between cancer and genomic instability is also found in individuals with a genetic predisposition for increased radiosensitivity. Several such syndromes have been found. In all cases, an increased genomic instability, cancer proneness and increased radiosensitivity coincide. In these syndromes, deficiencies in certain DNA-repair pathways occur as well as deregulations of the cell cycle. Especially, mutations are seen in genes encoding proteins, which are involved in the G(1)/S-phase checkpoint. Genomic instability apparently promotes cancer development. In this context, it is interesting that hypoxia, increased genomic instability and cancer are also associated. All these processes are energy dependent. Some strong evidence exists that the structure and length of telomeres is connected to the development of genomic instability.