Chronic Irradiation Research Articles

French Maritime Pine Bark (Pinus maritima Lam.) Extract (Flavangenol®) Prevents Chronic UVB Radiation‐induced Skin Damage and Carcinogenesis in Melanin‐possessing Hairless Mice

A French maritime pine bark extract, Flavangenol, is widely used as a nutritional supplement for protection against atherosclerosis, hypertension, diabetes, etc. Chronic exposure to solar UV radiation damages skin, increasing cutaneous thickness, wrinkling and pigmentation, as well as reducing elasticity, and causes skin cancer. The aim of this study was to examine the effects of flavangenol on skin damage and the incidence of skin tumors caused by long-term UVB irradiation in melanin-possessing hairless mice. The oral administration of flavangenol (60, 200 or 600 mg kg(-1), twice daily) significantly inhibited increases in skin thickness, and the formation of wrinkles and melanin granules, as well as increases in the diameter and length of skin blood vessels. Furthermore, it prevented increases in numbers of apoptotic, Ki-67-positive and 8-hydroxy-2'-deoxyguanosine (8-OHdG)-positive cells, and the expression of skin vascular endothelial growth factor (VEGF) induced by chronic UVB irradiation. The effect on these biomarkers was associated with a reduction in the incidence of tumors in mice. The antiphotoaging and anticarcinogenetic activities of flavangenol may be due to inhibition of the expression of Ki-67, 8-OHdG and VEGF through a scavenging effect on reactive oxygen species.

Expression of Cathepsins in Human Skin Photoaging

Cathepsins are involved in regulatory mechanisms in human skin, but their role in photoaged skin remains unknown. This study investigates the role of cathepsin B, D, K, and G in skin photoaging in vivo and in vitro. Cathepsin-induced changes in skin as a result of chronic UV irradiation were detected by immunohistochemistry methods. Protein cathepsin expressions in UVA-induced premature senescence in fibroblasts in vitro were detected by Western blot technique. Cathepsin mRNA expression in photoaged skin and fibroblasts was detected by real-time reverse transcription-polymerase chain reaction. Immunohistochemistry and Western blot show lower protein expression of cathepsin B, D, and K in photoaged skin and fibroblasts, while cathepsin G was higher. The mRNA expression of cathepsin B, D, and K of the photoaged skin in vivo decreased to 20 ± 0.5, 25 ± 1.6 and 22 ± 0.8%, while cathepsin G mRNA increased to 2.24 ± 0.09 times that of control. In photoaged fibroblasts, cathepsin B, D, and K mRNA was downregulated to 64 ± 2.9, 24 ± 2.1 and 9 ± 0.5% while cathepsin G mRNA was upregulated to 1.42 ± 0.06 times that of control fibroblasts. These experiments suggest that cathepsin B, D, K, and G may act as biomarkers in photoaged human skin.

Life-cycle chronic gamma exposure of Arabidopsis thaliana induces growth effects but no discernable effects on oxidative stress pathways

Arabidopsis thaliana was exposed to low-dose chronic gamma irradiation during a full life cycle (seed to seed) and several biological responses were investigated. Applied dose rates were 2336, 367 and 81 microGy h(-1). Following 24 days (inflorescence emergence), 34 days (approximately 50% of flowers open) and 54 days (silice ripening) exposure, plants were harvested and monitored for biometric parameters, capacities of enzymes involved in the antioxidative defence mechanisms (SOD, APOD, GLUR, GPOD, SPOD, CAT, ME), glutathione and ascorbate pool, lipid peroxidation products, altered gene expression of selected genes encoding for antioxidative enzymes or reactive oxygen species production, and DNA integrity. Root fresh weight was significantly reduced after gamma exposure compared to the control at all stages monitored but no significant differences in root weight for the different dose rates applied was observed. Leaf and stem fresh weight were significantly reduced at the highest irradiation level after 54 days exposure only. Also total plant fresh was significantly lower at silice riping and this for the highest and medium dose rate applied. The dose rate estimated to result in a 10% reduction in growth (EDR-10) ranged between 60 and 80 microGy h(-1). Germination of seeds from the gamma irradiated plants was not hampered. For several of the antioxidative defence enzymes studied, the enzyme capacity was generally stimulated towards flowering but generally no significant effect of dose rate on enzyme capacity was observed. Gene analysis revealed a significant transient and dose dependent change in expression of RBOHC indicating active reactive oxygen production induced by gamma irradiation. No effect of irradiation was observed on concentration or reduction state of the non-enzymatic antioxidants, ascorbate and glutathione. The level of lipid peroxidation products remained constant throughout the observation period and was not affected by dose rate. The comet assay did not reveal any effect of gamma dose rate on DNA integrity.

Reduction of IKKα Expression Promotes Chronic Ultraviolet B Exposure-Induced Skin Inflammation and Carcinogenesis

Ultraviolet B light (UVB) is a common cause of human skin cancer. UVB irradiation induces mutations in the tumor suppressor p53 gene as well as chronic inflammation, which are both essential for UVB carcinogenesis. Inhibitor of nuclear factor kappaB kinase-alpha (IKKalpha) plays an important role in maintaining skin homeostasis, and expression of IKKalpha was found to be down-regulated in human and murine skin squamous cell carcinomas. However, the role of IKKalpha in UVB skin carcinogenesis has not been investigated. Thus, here we performed UVB carcinogenesis experiments on Ikkalpha(+/+) and Ikkalpha(+/-) mice. Ikkalpha(+/-) mice were found to develop a twofold greater number of skin tumors than Ikkalpha(+/+) mice after chronic UVB irradiation. In addition, tumor latency was significantly shorter and tumors were bigger in Ikkalpha(+/-) than in Ikkalpha(+/+) mice. At an early stage of carcinogenesis, an increase in UVB-induced p53 mutations as well as macrophage recruitment and mitogenic activity, and a decrease in UVB-induced apoptosis, were detected in Ikkalpha(+/-) compared with those in Ikkalpha(+/+) skin. Also, reduction of IKKalpha levels in keratinocytes up-regulated the expression of monocyte chemoattractant protein-1 (MCP-1/CCL2), TNFalpha, IL-1, and IL-6, and elevated macrophage migration, which might promote macrophage recruitment and inflammation. Therefore, these findings suggest that reduction of IKKalpha expression orchestrates UVB carcinogen, accelerating tumorigenesis.

Carcinogenic Interactions between a Single Inhalation of239PuO2and Chronic Exposure to Cigarette Smoke in Rats

Rats were exposed once by inhalation to plutonium-239 dioxide ((239)PuO(2)), resulting in chronic alpha-particle irradiation of the lung, and exposed chronically to cigarette smoke to examine carcinogenic interactions between the two exposures. F344 rats were exposed to (239)PuO(2) to achieve an initial lung burden of 0.5 kBq and then exposed 6 h/day, 5 days/week to cigarette smoke at 100 or 250 mg particulate matter/m(3) for up to 30 months. Exposure to cigarette smoke increased the cumulative radiation dose to lung by slowing the clearance of (239)PuO(2). (239)PuO(2) alone did not affect survival, but the higher cigarette smoke exposure shortened survival in females. Combined exposure to (239)PuO(2) and cigarette smoke acted synergistically to shorten survival in both genders. The combined effects of cigarette smoke and (239)PuO(2) were approximately additive for lung hyperplasia and adenomas but were strongly synergistic for carcinomas. Differences between observed incidences and incidences predicted by survival-adjusted models accounting for increased radiation dose revealed a substantial component of synergy for carcinomas above that attributable to the radiation dose effect. The synergy for malignant lung tumors is consistent with findings from uranium miners and nuclear weapons production workers. These results bolster confidence in the epidemiological findings and have implications for risk assessment.

Human Telomeres Are Hypersensitive to UV-Induced DNA Damage and Refractory to Repair

Telomeric repeats preserve genome integrity by stabilizing chromosomes, a function that appears to be important for both cancer and aging. In view of this critical role in genomic integrity, the telomere's own integrity should be of paramount importance to the cell. Ultraviolet light (UV), the preeminent risk factor in skin cancer development, induces mainly cyclobutane pyrimidine dimers (CPD) which are both mutagenic and lethal. The human telomeric repeat unit (5′TTAGGG/CCCTAA3′) is nearly optimal for acquiring UV-induced CPD, which form at dipyrimidine sites. We developed a ChIP–based technique, immunoprecipitation of DNA damage (IPoD), to simultaneously study DNA damage and repair in the telomere and in the coding regions of p53, 28S rDNA, and mitochondrial DNA. We find that human telomeres in vivo are 7-fold hypersensitive to UV-induced DNA damage. In double-stranded oligonucleotides, this hypersensitivity is a property of both telomeric and non-telomeric repeats; in a series of telomeric repeat oligonucleotides, a phase change conferring UV-sensitivity occurs above 4 repeats. Furthermore, CPD removal in the telomere is almost absent, matching the rate in mitochondria known to lack nucleotide excision repair. Cells containing persistent high levels of telomeric CPDs nevertheless proliferate, and chronic UV irradiation of cells does not accelerate telomere shortening. Telomeres are therefore unique in at least three respects: their biophysical UV sensitivity, their prevention of excision repair, and their tolerance of unrepaired lesions. Utilizing a lesion-tolerance strategy rather than repair would prevent double-strand breaks at closely-opposed excision repair sites on opposite strands of a damage-hypersensitive repeat.

Evidence that vitamin D3 promotes mast cell–dependent reduction of chronic UVB-induced skin pathology in mice

Mast cell production of interleukin-10 (IL-10) can limit the skin pathology induced by chronic low-dose ultraviolet (UV)-B irradiation. Although the mechanism that promotes mast cell IL-10 production in this setting is unknown, exposure of the skin to UVB irradiation induces increased production of the immune modifying agent 1α,25-dihydroxyvitamin D3 (1α,25[OH]2D3). We now show that 1α,25(OH)2D3 can up-regulate IL-10 mRNA expression and induce IL-10 secretion in mouse mast cells in vitro. To investigate the roles of 1α,25(OH)2D3 and mast cell vitamin D receptor (VDR) expression in chronically UVB-irradiated skin in vivo, we engrafted the skin of genetically mast cell–deficient WBB6F1-KitW/W-v mice with bone marrow–derived cultured mast cells derived from C57BL/6 wild-type or VDR−/− mice. Optimal mast cell–dependent suppression of the inflammation, local production of proinflammatory cytokines, epidermal hyperplasia, and epidermal ulceration associated with chronic UVB irradiation of the skin in KitW/W-v mice required expression of VDR by the adoptively transferred mast cells. Our findings suggest that 1α,25(OH)2D3/VDR-dependent induction of IL-10 production by cutaneous mast cells can contribute to the mast cell’s ability to suppress inflammation and skin pathology at sites of chronic UVB irradiation.

Myricetin suppresses UVB-induced wrinkle formation and MMP-9 expression by inhibiting Raf

Chronic exposure to solar ultraviolet (UV) light causes skin photoaging. Many studies have shown that naturally occurring phytochemicals have anti-photoaging effects, but their direct target molecule(s) and mechanism(s) remain unclear. We found that myricetin, a major flavonoid in berries and red wine, inhibited wrinkle formation in mouse skin induced by chronic UVB irradiation (0.18 J/cm 2, 3 days/week for 15 weeks). Myricetin treatment reduced UVB-induced epidermal thickening of mouse skin and also suppressed UVB-induced matrix metalloproteinase-9 (MMP-9) protein expression and enzyme activity. Myricetin appeared to exert its anti-aging effects by suppressing UVB-induced Raf kinase activity and subsequent attenuation of UVB-induced phosphorylation of MEK and ERK in mouse skin. In vitro and in vivo pull-down assays revealed that myricetin bound with Raf in an ATP-noncompetitive manner. Overall, these results indicate that myricetin exerts potent anti-photoaging activity by regulating MMP-9 expression through the suppression of Raf kinase activity.

Alterations in Skin Immune Response Throughout Chronic UVB Irradiation—Skin Cancer Development and Prevention by Naproxen

Skin exposure to UVB radiation has been reported to produce both a significant inflammatory response and marked immunosuppression. This work was aimed to evaluate whether the response of murine skin to an acute UVB dose was modified by pre-exposure to chronic UVB irradiation and by topical treatment with naproxen, a nonsteroidal anti-inflammatory drug. Moreover, the effect of naproxen on the incidence of UV-induced skin tumors was studied. Prostaglandin E(2) (PGE(2)) and tumor necrosis factor alpha (TNF-alpha) levels were increased 96 h post-UVB in acutely irradiated animals and both mediators were modified by topical naproxen application-PGE(2) was decreased while TNF-alpha was increased. Such inflammatory response was suppressed when mice were chronically irradiated. Naproxen application on chronically irradiated mice reduced the incidence of tumor lesions. Taken together, our data suggest that chronic UVB irradiation generates an immunosuppressive state that prevents skin cells from responding normally to an acute irradiation challenge, thus impairing the protective effect of TNF-alpha against skin tumor development. Furthermore, reduction in the incidence of tumor lesions by naproxen may be due to its ability to increase TNF-alpha levels as well as to decrease PGE(2).

Myricetin inhibits UVB-induced angiogenesis by regulating PI-3 kinase in vivo

Myricetin is one of the principal phytochemicals in onions, berries and red wine. Previous studies showed that myricetin exhibits potent anticancer and chemopreventive effects. The present study examined the effect of myricetin on ultraviolet (UV) B-induced angiogenesis in an SKH-1 hairless mouse skin tumorigenesis model. Topical treatment with myricetin inhibited repetitive UVB-induced neovascularization in SKH-1 hairless mouse skin. The induction of vascular endothelial growth factor, matrix metalloproteinase (MMP)-9 and MMP-13 expression by chronic UVB irradiation was significantly suppressed by myricetin treatment. Immunohistochemical and western blot analyses revealed that myricetin inhibited UVB-induced hypoxia inducible factor-1alpha expression in mouse skin. Western blot analysis and kinase assay data revealed that myricetin suppressed UVB-induced phosphatidylinositol-3 (PI-3) kinase activity and subsequently attenuated the UVB-induced phosphorylation of Akt/p70(S6K) in mouse skin lysates. A pull-down assay revealed the direct binding of PI-3 kinase and myricetin in mouse skin lysates. Our results indicate that myricetin suppresses UVB-induced angiogenesis by regulating PI-3 kinase activity in vivo in mouse skin.

Interaction of Phytochemical‐Quercetin with the Other Antioxidant, Ascorbic Acid and their Protective Effect in Tilapia after Ultraviolet Irradiation

Abstract Semi‐purified, casein‐gelatin‐based diets were prepared and supplemented with quercetin (Q) and/ or ascorbic acid (AA): control diet C–Q–(100 mg/kg AA), diet C –Q+ (100 mg/kg AA + quercetin 10 g/kg), diet C +Q– (1000 mg/kg AA), and diet C +Q+ (1000 mg/kg AA + quercetin 10 g/kg). These diets were fed to tilapia for 19 wk and then fish were divided into controls and ultraviolet (UV) treatments. Fish were exposed to UV radiation. Control groups were protected with a MYLAR® polyester film and plexiglass. At week 20, the same fish were re‐exposed to UV radiation. Control groups of fish were protected by a double layer of MYLAR® and the UV groups were exposed with no protection. Before UV exposure, 24 h after, and 7 d after the second treatment, fish liver and skin were dissected for Q and AA analyses. The proportion of oxidized ascorbate was significantly increased in fish from treatments C –Q– and C –Q+ . Q concentrations in fish after exposures were negligible in skin, whereas liver concentrations were significantly different among control (34 ± 10 μg/g) and UV‐irradiated fish (11 ± 6 μg/g), respectively. The interaction between these two dietary antioxidants may change after chronic UV irradiation.

A model of interactions between radiation-induced oxidative stress, protein and DNA damage in Deinococcus radiodurans

Ionizing radiation triggers oxidative stress, which can have a variety of subtle and profound biological effects. Here we focus on mathematical modeling of potential synergistic interactions between radiation damage to DNA and oxidative stress-induced damage to proteins involved in DNA repair/replication. When sensitive sites on these proteins are attacked by radiation-induced radicals, correct repair of dangerous DNA lesions such as double strand breaks (DSBs) can be compromised. In contrast, if oxidation of important proteins is prevented by strong antioxidant defenses, DNA repair may function more efficiently. These processes probably occur to some extent even at low doses of radiation/oxidative stress, but they are easiest to investigate at high doses, where both DNA and protein damage are extensive. As an example, we use data on survival of Deinococcus radiodurans after high doses (thousands of Gy) of acute and chronic irradiation. Our model of radiogenic oxidative stress is consistent with these data and can potentially be generalized to other organisms and lower radiation doses.

Deficient deletion of apoptotic cells by macrophage migration inhibitory factor (MIF) overexpression accelerates photocarcinogenesis

Chronic ultraviolet (UV) exposure can increase the occurrence of p53 mutations, thus leading to a dysregulation of apoptosis and the initiation of skin cancer. Therefore, it is extremely important that apoptosis is induced quickly after UV irradiation, without any dysregulation. Recent studies have suggested a potentially broader role for macrophage migration inhibitory factor (MIF) in growth regulation via its ability to antagonize p53-mediated gene activation and apoptosis. To further elucidate the possible role of MIF in photocarcinogenesis, the acute and chronic UVB effect in the skin was examined using macrophage migration inhibitory factor transgenic (MIF Tg) and wild-type (WT) mice. The MIF Tg mice exposed to chronic UVB irradiation began to develop skin tumors after approximately 14 weeks, whereas the WT mice began to develop tumors after 18 weeks. A higher incidence of tumors was observed in the MIF Tg in comparison with the WT mice after chronic UVB irradiation. Next, we clarified whether the acceleration of photo-induced carcinogenesis in the MIF Tg mice was mediated by the inhibition of apoptosis There were fewer sunburned cells in the epidermis of the MIF Tg mice than the WT mice after acute UVB exposure. The epidermis derived from the MIF Tg mice exhibited substantially decreased levels of p53, bax and p21 after UVB exposure in comparison with the WT mice. Collectively, these findings suggest that chronic UVB exposure enhances MIF production, which may inhibit the p53-dependent apoptotic processes and thereby induce photocarcinogenesis in the skin.

Effects of a turmeric extract (Curcuma longa) on chronic ultraviolet B irradiation-induced skin damage in melanin-possessing hairless mice

Turmeric (the rhizomes of Curcuma longa L., Zingiberacease) is widely used as a dietary pigment and spice, and has been traditionally used for the treatment of inflammation, skin wounds and hepatic disorders in Ayurvedic, Unani and Chinese medicine. Although the topical application or oral administration of turmeric is used to improve skin trouble, there is no evidence to support this effect. The aim of this study was to clarify whether turmeric prevents chronic ultraviolet B (UVB)-irradiated skin damage. We examined the effects of a turmeric extract on skin damage including changes in skin thickness and elasticity, pigmentation and wrinkling caused by long-term, low-dose ultraviolet B irradiation in melanin-possessing hairless mice. The extract (at 300 or 1000 mg/kg, twice daily) prevented an increase in skin thickness and a reduction in skin elasticity induced by chronic UVB exposure. It also prevented the formation of wrinkles and melanin (at 1000 mg/kg, twice daily) as well as increases in the diameter and length of skin blood vessels and in the expression of matrix metalloproteinase-2 (MMP-2). Prevention of UVB-induced skin aging by turmeric may be due to the inhibition of increases in MMP-2 expression caused by chronic irradiation.

Use of computer TV morphodensitometry to study epigenetic changes in blood lymphocytes from children affected by low-dose irradiation

A novel method, computer TV morphodensitometry, was used to evaluate the effects of low-dose irradiation on peripheral blood lymphocytes from children affected by the Chernobyl disaster. This method uses digitized images to detect and measure changes in chromatin shape and density and to produce two-dimensional and three-dimensional pictures. Images can then be stored to create a video archive. This method is sensitive enough to observe subtle changes in chromatin structure that previously could be detected only by more detailed molecular analyses. In this study, lymphocyte interphase nuclei in DNA-stained blood smears from children subjected to chronic low-dose irradiation were examined by computer TV morphodensitometry. Preliminary data indicate that circulating lymphocytes from children exposed to radiation may contain significant alterations in the structure and/or density of nuclear chromatin.

Immunohistochemical survey of the distribution of epidermal melanoblasts and melanocytes during the development of UVB-induced pigmented spots

Repeated exposures to ultraviolet B radiation (UVB) induce pigmented spots on dorsal skin of (HR-1 x HR/De) F(1) hairless mouse. We showed previously that this mouse is suitable for studies of melanocyte function. To clarify the mechanism of development of pigmented spots induced by chronic UVB exposure. We used light and fluorescence microscopy to quantify changes in the numbers of differentiated melanocytes containing melanin pigments (MM) and melanoblasts/melanocytes immunohistochemically positive for tyrosinase-related protein (TRP)-1, TRP-2 (dopachrome tautomerase), and c-kit in epidermis during the development of pigmented spots in hairless mice chronically exposed to UVB (99 mJ/cm(2), 3 times/week, 8 weeks). The change in the number of TRP-1-positive cells during chronic UVB exposure was similar to that of MM: both increased dramatically during the stage of acute pigmentation, then decreased sharply after cessation of UVB, concomitantly with depigmentation; subsequently they increased gradually with the development of pigmented spots. In contrast, after two UVB exposures, no c-kit-positive cells were detected, then the number gradually increased during UVB irradiation, and continued to increase after cessation of irradiation; TRP-2-positive cells showed a rather similar pattern, except that they did not disappear initially. Our results indicate that chronic UVB irradiation induces differentiation and proliferation of melanoblasts, followed by an increase of differentiated melanocytes, leading to the development of pigmented spots. The sequence of expression of markers appeared to be c-kit, TRP-2, TRP-1, and finally melanin, as it is during normal melanocyte differentiation.

Effects of red ginseng extract on UVB irradiation-induced skin aging in hairless mice

Panax ginseng C.A. Meyer, Korean herb medicine, has been widely used in China and Japan for fatigue and enhancement of resistance to many diseases. Aim of the study This study is aimed to assess the effects of Korean red ginseng extract on UVB irradiation induced skin aging in hairless mice. Materials and methods Red ginseng extracts prepared with ethanol were used in this study. To standardize Korean red ginseng, it was analyzed by HPLC. And inhibitory effects of red ginseng extract on UVB irradiation-induced skin aging in hairless mice were determined by the measurement of wrinkle, expression of type I procollagen and MMP-1 and immunohistology. Results Based on the HPLC quantitative analysis, ginsenoside Rb1 content in Korean red ginseng was 43.5 mg/g of extract. In the result of body weight gain and food efficiency rate, body weights of all groups were increased during experimental periods. In the wrinkle measurement and image analysis of skin replicas, the results showed that the dietary supply containing red ginseng extract significantly inhibited wrinkle formation caused by chronic UVB irradiation. In the changes of expression of procollagen type I and MMP-1 in the skin of UV irradiated hairless mice fed dietary supplement containing 2.5% red ginseng extract, level of mRNA of procollagen type I was decreased. But protein level of that was increased. And in terms of MMP-1, either mRNA or protein levels of MMP-1 were significantly decreased. These results showed anti-wrinkle effect of Korean red ginseng involved the inhibition of collagen degradation rather than increased collagen synthesis. Conclusion It is shown that Korean red ginseng may be functional food candidate for skin photoaging.

Topical thymidine dinucleotide application protects against UVB-induced skin cancer in mice with DNA repair gene ( Ercc1)-deficient skin

Topical application of thymidine dinucleotides (pTpT) provides some protection against the effects of UV on the skin, however, many details of the protective mechanism have yet to be elucidated. We have used mice with an epidermis-specific knockout for the nucleotide excision repair gene, Ercc1, to investigate the mechanisms of protection. pTpT offered no protection against the pronounced UV-induced short-term erythema and skin thickening responses that are characteristic of DNA repair-deficient skin. It also had no effect on UV-induced apoptosis in Ercc1-deficient cultured keratinocytes. However, in these short-term experiments in both skin and keratinocyte culture pTpT did cause a slight reduction in proliferation. pTpT application during a chronic UV irradiation protocol provided some protection from UVB-induced skin carcinogenesis in epidermis-specific Ercc1 knockout mice. The median tumour free survival time was increased in the pTpT-treated group and treated animals had fewer tumours. In addition, pTpT-treated animals developed fewer large inwardly growing skin lesions than untreated animals. Furthermore, the proliferation response was reduced in chronically irradiated, non-lesional pTpT-treated skin. We conclude that cancer protection by pTpT in our mice is not modulated by an upregulation of DNA repair, as protection appears to be independent of a functional nucleotide excision repair pathway. We hypothesise instead that protection by pTpT is due to a reduction in epidermal proliferation.

Sensitivity of premeiotic and meiotic stages to spontaneous and induced mutations in barley and maize.

Barley and maize plants were analysed anther by anther or thecum by thecum for waxy pollen grains. The mutant cluster size depends on the time for mutation induction. Single mutant pollen grains were considerably more common than expected, indicating that the mutation rate in meiosis is considerably higher than in somatic cell generations. This is true both for spontaneous and induced mutations. Relatively seen, spontaneous mutations seemed to take place in meiosis more often than those induced by chronic irradiation. A major technical difficulty in the evaluation procedure was to estimate the influence of mutant clusters caused by several independent mutational events. It was found that around two thirds of all clusters were formed in this way.

Sequential chemotherapy and irradiation in advanced stage endometrial cancer: A Gynecologic Oncology Group phase I trial of doxorubicin–cisplatin followed by whole abdomen irradiation

Objectives The optimal treatment regimen for advanced stage endometrial carcinoma (EC) is yet to be established. The objective of this study was to evaluate the feasibility and toxicity of delivering sequential doxorubicin–cisplatin (AC) followed by whole abdomen irradiation (WAI). Methods Patients with stage III/IV EC with < 2 cm residual disease were eligible. The treatment regimen included 3 cycles of AC (50 mg/m 2 each) followed by WAI plus para-aortic and/or true pelvic boost. Outcome objectives were feasibility of the regimen, acute toxicity and chronic irradiation toxicity monitored for at least one year after completing treatment. Results Thirty-one patients were entered onto the study. Twenty-nine were evaluable for feasibility of the regimen, and 22 patients were evaluable for chronic radiation toxicity with a median follow-up of 21 months. Three patients (14%) experienced severe chronic toxicity including one treatment-related death. The five-year progression-free survival (PFS) and overall survival (OS) was 52.5% and 60.1% respectively. Conclusions The results from the first stage of this study found this regimen of sequential AC followed by WAI eligible for further study. Although toxicity was not excessive at the time of completion of the first stage, there was insufficient interest by the Gynecologic Oncology Group to continue study of this regimen; therefore, a conclusion regarding feasibility and chronic toxicity in an expanded cohort as initially intended is not possible. The risk of recurrence in advanced EC is sufficiently high that may warrant further investigation of sequential chemotherapy and WAI.