Is the sustainability of exposure to non-ionizing electromagnetic radiation possible?

Technological advances imply an increase in artificially generating sources of electromagnetic fields (EMF), therefore, resulting in a permanent exposure of people and the environment (electromagnetic pollution). Inconsistent results have been published considering the evaluated health effects. The purpose of this study was to review scientific literature on EMF to provide a global and retrospective perspective, on the association between human exposure to non-ionizing radiation (NIR, mainly radiofrequency-EMF) and health and environmental effects. Studies on the health effects of 5G radiation exposure have not yet been performed with sufficient statistical power, as the exposure time is still relatively short and also the latency and intensity of exposure to 5G. The safety standards only consider thermal effects, do not contemplate non-thermal effects. We consider relevant to communicate this knowledge to the general public to improve education in this field, and to healthcare professionals to prevent diseases that may result from RF-EMF exposures.

Matrix Metalloproteinases and Their Inhibitors as Potential Prognostic Biomarkers in Head and Neck Cancer after Radiotherapy

Head and neck cancer (HNC) is among the ten most frequent tumours, with 5-year survival rates varying from 30% to 70% depending on the stage and location of the tumour. HNC is traditionally known as head and neck squamous cell carcinoma (HNSCC), since 90% arises from epithelial cells. Metastasis remains a major cause of mortality in patients with HNSCC. HNSCC patients with metastatic disease have an extremely poor prognosis with a survival rate of less than a year. Matrix metalloproteinases (MMPs) have been described as biomarkers that promote cell migration and invasion. Radiotherapy is widely used to treat HNSCC, being a determining factor in the alteration of the tumour's biology and microenvironment. This review focuses on analysing the current state of the scientific literature on this topic. Although few studies have focused on the role of these proteinases in HNC, some authors have concluded that radiotherapy alters the behaviour of MMPs and tissue inhibitors of metalloproteinases (TIMPs). Therefore, more research is needed to understand the roles played by MMPs and their inhibitors (TIMPs) as prognostic biomarkers in patients with HNC and their involvement in the response to radiotherapy.

Narrow Leafed Lupin (Lupinus angustifolius L.) β-Conglutin Seed Proteins as a New Natural Cytotoxic Agents against Breast Cancer Cells

Breast cancer (BC) is the most widespread tumor in women and the second type of most common cancer worldwide. Despite all the technical and medical advances in existing therapies, between 30 and 50% of patients with BC will develop metastasis, which contributes to the failure of existing treatments. This situation urges the need to find more effective prevention and treatment strategies like the use of plant-based nutraceutical compounds. In this context, we purified three Narrow Leafed Lupin (NLL) β-conglutins isoforms using affinity-chromatography and evaluated their effectiveness in terms of viability, proliferation, apoptosis, stemness properties, and mechanism of action on both BC cell lines and a healthy one. NLL β-conglutins proteins have very promising effects at the molecular level on BC cells at very low concentrations, emerging as a potential natural cytotoxic agent and preserving the viability of healthy cells. These proteins could act through a dual mechanism involving tumorigenic and stemness-related genes such as SIRT1 and FoxO1, depending on the state of p53. More studies must be carried out to completely understand the underlying mechanisms of action of these nutraceutical compounds in BC in vitro and in vivo, and their potential use for the inhibition of other cancer cell types.

Long-Term Outcomes of Dose-Escalated Hypofractionated Radiotherapy in Localized Prostate Cancer

This retrospective study aimed to provide some clinical outcomes regarding effectiveness, toxicity, and quality of life in PCa patients treated with dose-escalated moderately hypofractionated radiation therapy (HFRT). Patients received HFRT to a total dose of 66 Gy in 22 fractions (3 Gy/fraction) delivered via volume modulated arc therapy (VMAT) in 2011-2016. Treatment effectiveness was measured by the biochemical failure-free survival rate. Toxicity was assessed according to the criteria of the Radiation Therapy Oncology Group (RTOG) and quality of life according to the criteria of the European Organization for Research and Treatment of Cancer (EORTC). In this regard, quality of life (QoL) was measured longitudinally, at a median of 2 and 5 years after RT. Enrolled patients had low-risk (40.2%), intermediate-risk (47.5%), and high-risk (12.3%) PCa. Median follow-up was 75 months. The biochemical failure-free survival rate was 94.2%. The incidence of acute grade 2 or higher gastrointestinal (GI) and genitourinary (GU) toxicity was 9.84% and 28.69%, respectively. The incidence rate of late grade 2 or higher GI and GU toxicity was 1.64% and 4.10%, respectively. Expanded Prostate Cancer Index Composite (EPIC) scores showed that the majority of patients maintained their QoL. HFRT to 66 Gy with VMAT was associated with adequate biochemical control, low toxicity and good reported GU and GI quality of life.

Metalloproteinases 1 and 3 as Potential Biomarkers in Breast Cancer Development

Breast cancer continues to be one of the main causes of morbidity and mortality globally and was the leading cause of cancer death in women in Spain in 2020. Early diagnosis is one of the most effective methods to lower the incidence and mortality rates of breast cancer. The human metalloproteinases (MMP) mainly function as proteolytic enzymes degrading the extracellular matrix and plays important roles in most steps of breast tumorigenesis. This retrospective cohort study shows the immunohistochemical expression levels of MMP-1, MMP-2, MMP-3, and MMP-9 in 154 women with breast cancer and 42 women without tumor disease. The samples of breast tissue are assessed using several tissue matrices (TMA). The percentages of staining (≤50%–>50%) and intensity levels of staining (weak, moderate, or intense) are considered. The immunohistochemical expression of the MMP-1-intensity (p = 0.043) and MMP-3 percentage (p = 0.018) and intensity, (p = 0.025) present statistically significant associations with the variable group (control–case); therefore, expression in the tumor tissue samples of these MMPs may be related to the development of breast cancer. The relationships between these MMPs and some clinicopathological factors in breast cancer are also evaluated but no correlation is found. These results suggest the use of MMP-1 and MMP-3 as potential biomarkers of breast cancer diagnosis.

Survey of Radon Concentrations in the University of Granada in Southern Spain

The objective of this pilot study was to gather and analyze data on radon concentrations in workplaces in three buildings of Granada University (Southern Spain) constructed in different centuries. All measurements were made at basement or ground floor level under normal use conditions except for one space (mineral store), in which measurements were compared between the door closed and open. Measurements were conducted during different time periods between October 2013 and March 2019 with a Radon-Scout PLUS portable Radonmonitor. The duration of continuous recordings at different sites ranged between 42 and 1104 h. Mean accumulated radon concentrations ranged between 12 and 95 Bq/m³, below the maximal level of 300 Bq/m³ set by the World Health Organization (WHO). Relatively high values were recorded in the oldest building (15th century), which was also poorly ventilated. Ventilation appeared to be an important factor in reducing radon levels, especially in areas less exposed to radon, such as Southern Spain.

CSC Radioresistance: A Therapeutic Challenge to Improve Radiotherapy Effectiveness in Cancer

Radiotherapy (RT) is a modality of oncologic treatment that can be used to treat approximately 50% of all cancer patients either alone or in combination with other treatment modalities such as surgery, chemotherapy, immunotherapy, and therapeutic targeting. Despite the technological advances in RT, which allow a more precise delivery of radiation while progressively minimizing the impact on normal tissues, issues like radioresistance and tumor recurrence remain important challenges. Tumor heterogeneity is responsible for the variation in the radiation response of the different tumor subpopulations. A main factor related to radioresistance is the presence of cancer stem cells (CSC) inside tumors, which are responsible for metastases, relapses, RT failure, and a poor prognosis in cancer patients. The plasticity of CSCs, a process highly dependent on the epithelial–mesenchymal transition (EMT) and associated to cell dedifferentiation, complicates the identification and eradication of CSCs and it might be involved in disease relapse and progression after irradiation. The tumor microenvironment and the interactions of CSCs with their niches also play an important role in the response to RT. This review provides a deep insight into the characteristics and radioresistance mechanisms of CSCs and into the role of CSCs and tumor microenvironment in both the primary tumor and metastasis in response to radiation, and the radiobiological principles related to the CSC response to RT. Finally, we summarize the major advances and clinical trials on the development of CSC-based therapies combined with RT to overcome radioresistance. A better understanding of the potential therapeutic targets for CSC radiosensitization will provide safer and more efficient combination strategies, which in turn will improve the live expectancy and curability of cancer patients.

miRNAs as radio-response biomarkers for breast cancer stem cells

In breast cancer (BC), the presence of cancer stem cells (CSCs) has been related to relapse, metastasis, and radioresistance. Radiotherapy (RT) is an extended BC treatment, but is not always effective. CSCs have several mechanisms of radioresistance in place, and some miRNAs are involved in the cellular response to ionizing radiation (IR). Here, we studied how IR affects the expression of miRNAs related to stemness in different molecular BC subtypes. Exposition of BC cells to radiation doses of 2, 4, or 6 Gy affected their phenotype, functional characteristics, pluripotency gene expression, and in vivo tumorigenic capacity. This held true for various molecular subtypes of BC cells (classified by ER, PR and HER‐2 status), and for BC cells either plated in monolayer, or being in suspension as mammospheres. However, the effect of IR on the expression of eight stemness‐ and radioresistance‐related miRNAs (miR‐210, miR‐10b, miR‐182, miR‐142, miR‐221, miR‐21, miR‐93, miR‐15b) varied, depending on cell line subpopulation and clinicopathological features of BC patients. Therefore, clinicopathological features and, potentially also, chemotherapy regimen should be both taken into consideration, for determining a potential miRNA signature by liquid biopsy in BC patients treated with RT. Personalized and precision RT dosage regimes could improve the prognosis, treatment, and survival of BC patients.

Matrix metalloproteases and TIMPs as prognostic biomarkers in breast cancer patients treated with radiotherapy: A pilot study

Breast cancer (BC) is the most common tumour in women and one of the most important causes of cancer death worldwide. Radiation therapy (RT) is widely used for BC treatment. Some proteins have been identified as prognostic factors for BC (Ki67, p53, E‐cadherin, HER2). In the last years, it has been shown that variations in the expression of MMPs and TIMPs may contribute to the development of BC. The aim of this pilot work was to study the effects of RT on different MMPs (‐1, ‐2, ‐3, ‐7, ‐8, ‐9, ‐10, ‐12 and ‐13) and TIMPs (‐1 to ‐4), as well as their relationship with other variables related to patient characteristics and tumour biology. A group of 20 BC patients treated with RT were recruited. MMP and TIMP serum levels were analysed by immunoassay before, during and after RT. Our pilot study showed a slight increase in the levels of most MMP and TIMP with RT. However, RT produced a significantly decrease in TIMP‐1 and TIMP‐3 levels. Significant correlations were found between MMP‐3 and TIMP‐4 levels, and some of the variables studied related to patient characteristics and tumour biology. Moreover, MMP‐9 and TIMP‐3 levels could be predictive of RT toxicity. For this reason, MMP‐3, MMP‐9, TIMP‐3 and TIMP‐4 could be used as potential prognostic and predictive biomarkers for BC patients treated with RT.

Exploring the radiosensitizing potential of magnetotherapy: a pilot study in breast cancer cells

Aim: To explore the influence of electromagnetic fields (EMFs) on the cell cycle progression of MDA-MB-231 and MCF-7 breast cancer cell lines and to evaluate the radiosensitizing effect of magnetotherapy during therapeutic co-exposure to EMFs and radiotherapy. Material and methods: Cells were exposed to EMFs (25, 50 and 100 Hz; 8 and 10 mT). In the co-treatment, cells were first exposed to EMFs (50 Hz/10 mT) for 30 min and then to ionizing radiation (IR) (2 Gy) 4 h later. Cell cycle progression and free radical production were evaluated by flow cytometry, while radiosensitivity was explored by colony formation assay. Results: Generalized G1-phase arrest was found in both cell lines several hours after EMF exposure. Interestingly, a marked G1-phase delay was observed at 4 h after exposure to 50 Hz/10 mT EMFs. No cell cycle perturbation was observed after repeated exposure to EMFs. IR-derived ROS production was enhanced in EMF-exposed MCF-7 cells at 24 h post-exposure. EMF-exposed cells were more radiosensitive in comparison to sham-exposed cells. Conclusions: These results highlight the potential benefits of concomitant treatment with magnetotherapy before radiotherapy sessions to enhance the effectiveness of breast cancer therapy. Further studies are warranted to identify the subset(s) of patients who would benefit from this multimodal treatment.

Radiofrequency exposure in the Neonatal Medium Care Unit

The aims of this study were to characterize electromagnetic fields of radiofrequency (RF-EMF) levels generated in a Neonatal Medium Care Unit and to analyze RF-EMF levels inside unit's incubators. Spot and long-term measurements were made with a dosimeter. The spot measurement mean was 1.51±0.48V/m. Higher values were found in the proximity to the window and to the incubator evaluated. Mean field strength for the entire period of 17h was 0.81 (±0.07)V/m and the maximum value was 1.58V/m for long-term RF-EMF measurements in the incubator. Values found during the night period were higher than those found during the day period. It is important to consider RF-EMF exposure levels in neonatal care units, due to some evidence of adverse health effects found in children and adults. Characterization of RF-EMF exposure may be important to further investigate the mechanisms and underlying effects of electromagnetic fields (EMF) on infant health. A prudent avoidance strategy should be adopted because newborns are at a vulnerable stage of development and the actual impact of EMF on premature infants is unknown.

Valproic acid modulates radiation-enhanced matrix metalloproteinase activity and invasion of breast cancer cells

PURPOSE

To evaluate matrix metalloproteinase (MMP) activity and invasion after ionizing radiation (IR) exposure and to determine whether MMP could be epigenetically modulated by histone deacetylase (HDAC) inhibition.

MATERIAL AND METHODS

Two human breast cancer cell lines (MDA-MB-231 and MCF-7) were cultured in monolayer (2D) and in laminin-rich extracellular matrix (3D). Invasion capability, collagenolytic and gelatinolytic activity, MMP and TIMP protein and mRNA expression and clonogenic survival were analyzed after IR exposure, with and without a HDAC inhibition treatment [1.5 mM valproic acid (VA) or 1 μM trichostatin-A (TSA)].

RESULTS

IR exposure resulted in cell line-dependent stimulation of invasion capacity. In contrast to MCF-7 cells, irradiated MDA-MB-231 showed significantly enhanced mRNA expression of mmp-1, mmp-3 and mmp-13 and of their regulators timp-1 and timp-2 relative to unirradiated controls. This translated into increased collagenolytic and gelatinolytic activity and could be reduced after valproic acid (VA) treatment. Additionally, VA also mitigated IR-enhanced mmp and timp mRNA expression as well as IR-increased invasion capability. Finally, our data confirm the radiosensitizing effect of VA.

CONCLUSION

These results suggest that IR cell line-dependently induces upregulation of MMP mRNA expression, which appears to be mechanistically linked to a higher invasion capability that is modifiable by HDAC inhibition.

Outdoor characterization of radio frequency electromagnetic fields in a Spanish birth cohort

There is considerable public concern in many countries about the possible adverse effects of exposure to non-ionizing radiation electromagnetic fields, especially in vulnerable populations such as children. The aim of this study was to characterize environmental exposure profiles within the frequency range 100kHz-6GHz in the immediate surrounds of the dwellings of 123 families from the INMA-Granada birth cohort in Southern Spain, using spot measurements. The arithmetic mean root mean-square electric field (ERMS) and power density (SRMS) values were, respectively, 195.79mV/m (42.3% of data were above this mean) and 799.01µW/m(2) (30% of values were above this mean); median values were 148.80mV/m and 285.94µW/m(2), respectively. Exposure levels below the quantification limit were assigned a value of 0.01V/m. Incident field strength levels varied widely among different areas or towns/villages, demonstrating spatial variability in the distribution of exposure values related to the surface area population size and also among seasons. Although recorded values were well below International Commission for Non-Ionizing Radiation Protection reference levels, there is a particular need to characterize incident field strength levels in vulnerable populations (e.g., children) because of their chronic and ever-increasing exposure. The effects of incident field strength have not been fully elucidated; however, it may be appropriate to apply the precautionary principle in order to reduce exposure in susceptible groups.

Characterization of indoor extremely low frequency and low frequency electromagnetic fields in the INMA-Granada cohort

OBJECTIVE

To characterize the exposure to electric fields and magnetic fields of non-ionizing radiation in the electromagnetic spectrum (15 Hz to 100 kHz) in the dwellings of children from the Spanish Environment and Childhood-"INMA" population-based birth cohort.

METHODOLOGY

The study sample was drawn from the INMA-Granada cohort. Out of 300 boys participating in the 9-10 year follow-up, 123 families agreed to the exposure assessment at home and completed a specific ad hoc questionnaire gathering information on sources of non-ionizing radiation electric and magnetic fields inside the homes and on patterns of use. Long-term indoor measurements were carried out in the living room and bedroom.

RESULTS

Survey data showed a low exposure in the children's homes according to reference levels of the International Commission on Non-Ionizing Radiation Protection but with large differences among homes in mean and maximum values. Daytime electrostatic and magnetic fields were below the quantification limit in 78.6% (92 dwellings) and 92.3% (108 dwellings) of houses, with an arithmetic mean value (± standard deviation) of 7.31±9.32 V/m and 162.30±91.16 nT, respectively. Mean magnetic field values were 1.6 lower during the night than the day. Nocturnal electrostatic values were not measured. Exposure levels were influenced by the area of residence (higher values in urban/semi-urban versus rural areas), type of dwelling, age of dwelling, floor of the dwelling, and season.

CONCLUSION

Given the greater sensitivity to extremely low-frequency electromagnetic fields of children and following the precautionary principle, preventive measures are warranted to reduce their exposure.

ESR1 gene promoter region methylation in free circulating DNA and its correlation with estrogen receptor protein expression in tumor tissue in breast cancer patients

Background

Tumor expression of estrogen receptor (ER) is an important marker of prognosis, and is predictive of response to endocrine therapy in breast cancer. Several studies have observed that epigenetic events, such methylation of cytosines and deacetylation of histones, are involved in the complex mechanisms that regulate promoter transcription. However, the exact interplay of these factors in transcription activity is not well understood. In this study, we explored the relationship between ER expression status in tumor tissue samples and the methylation of the 5′ CpG promoter region of the estrogen receptor gene (ESR1) isolated from free circulating DNA (fcDNA) in plasma samples from breast cancer patients.

Methods

Patients (n = 110) with non-metastatic breast cancer had analyses performed of ER expression (luminal phenotype in tumor tissue, by immunohistochemistry method), and the ESR1-DNA methylation status (fcDNA in plasma, by quantitative methylation specific PCR technique).

Results

Our results showed a significant association between presence of methylated ESR1 in patients with breast cancer and ER negative status in the tumor tissue (p = 0.0179). There was a trend towards a higher probability of ESR1-methylation in those phenotypes with poor prognosis i.e. 80% of triple negative patients, 60% of HER2 patients, compared to 28% and 5.9% of patients with better prognosis such as luminal A and luminal B, respectively.

Conclusion

Silencing, by methylation, of the promoter region of the ESR1 affects the expression of the estrogen receptor protein in tumors of breast cancer patients; high methylation of ESR1-DNA is associated with estrogen receptor negative status which, in turn, may be implicated in the patient’s resistance to hormonal treatment in breast cancer. As such, epigenetic markers in plasma may be of interest as new targets for anticancer therapy, especially with respect to endocrine treatment.

Tumor microenvironment and breast cancer progression: a complex scenario

It is now widely accepted that the development and progression of a tumor toward the malignant phenotype is highly dependent on interactions between tumor cells and the tumor microenvironment. Different components of the tumor microenvironment may have stimulatory or inhibitory effects on tumor progression by regulating the gene expression repertoire in tumor cells and stromal cells. This review analyzes novel research findings on breast cancer progression, discussing acquisition of the metastatic phenotype in breast disease in relation to different aspects of cross-talk among components of the tumor microenvironment. Knowledge of the interaction of all of these factors would contribute to elucidating the mechanisms that disrupt regulatory/signaling cascades and downstream effects in breast cancer.

Matrix metalloproteinases: potential therapy to prevent the development of second malignancies after breast radiotherapy

Radiotherapy is widely used in the treatment of patients with breast cancer, but ionizing radiation-induced carcinogenesis has been described in several studies. Matrix metalloproteinases (MMPs) are a wide family of proteases secreted by tumour and microenvironmental cells that are directly linked with invasion and metastasis through complete extracellular matrix (ECM) breakage. In the past decade, MMPs have been associated with other carcinogenesis steps, including tumour growth and angiogenesis promotion. Moreover, in vitro studies have demonstrated an enhanced migration, invasiveness, and angiogenic ability of cancer cells after radiation exposure through an increase in MMP activity. These findings are consistent with clinical observations of breast cancer metastases raised in bone, lung and brain tissues after radiotherapy. The aim of this review was to analyse the current state of research on MMPs and report new insights into the potential of MMP-targeted therapy in combination with radiotherapy to decrease the risk of radiation-induced second malignancies and to improve the overall survival of breast cancer patients.

Combined low initial DNA damage and high radiation-induced apoptosis confers clinical resistance to long-term toxicity in breast cancer patients treated with high-dose radiotherapy

Background

Either higher levels of initial DNA damage or lower levels of radiation-induced apoptosis in peripheral blood lymphocytes have been associated to increased risk for develop late radiation-induced toxicity. It has been recently published that these two predictive tests are inversely related. The aim of the present study was to investigate the combined role of both tests in relation to clinical radiation-induced toxicity in a set of breast cancer patients treated with high dose hyperfractionated radical radiotherapy.

Methods

Peripheral blood lymphocytes were taken from 26 consecutive patients with locally advanced breast carcinoma treated with high-dose hyperfractioned radical radiotherapy. Acute and late cutaneous and subcutaneous toxicity was evaluated using the Radiation Therapy Oncology Group morbidity scoring schema. The mean follow-up of survivors (n = 13) was 197.23 months. Radiosensitivity of lymphocytes was quantified as the initial number of DNA double-strand breaks induced per Gy and per DNA unit (200 Mbp). Radiation-induced apoptosis (RIA) at 1, 2 and 8 Gy was measured by flow cytometry using annexin V/propidium iodide.

Results

Mean DSB/Gy/DNA unit obtained was 1.70 ± 0.83 (range 0.63-4.08; median, 1.46). Radiation-induced apoptosis increased with radiation dose (median 12.36, 17.79 and 24.83 for 1, 2, and 8 Gy respectively). We observed that those "expected resistant patients" (DSB values lower than 1.78 DSB/Gy per 200 Mbp and RIA values over 9.58, 14.40 or 24.83 for 1, 2 and 8 Gy respectively) were at low risk of suffer severe subcutaneous late toxicity (HR 0.223, 95%CI 0.073-0.678, P = 0.008; HR 0.206, 95%CI 0.063-0.677, P = 0.009; HR 0.239, 95%CI 0.062-0.929, P = 0.039, for RIA at 1, 2 and 8 Gy respectively) in multivariate analysis.

Conclusions

A radiation-resistant profile is proposed, where those patients who presented lower levels of initial DNA damage and higher levels of radiation induced apoptosis were at low risk of suffer severe subcutaneous late toxicity after clinical treatment at high radiation doses in our series. However, due to the small sample size, other prospective studies with higher number of patients are needed to validate these results.

Quantitative detection of methylated ESR1 and 14-3-3-sigma gene promoters in serum as candidate biomarkers for diagnosis of breast cancer and evaluation of treatment efficacy

The aim of the present study was to investigate the association between gene hypermethylation and main clinicopathological features of breast cancer, including diagnosis and treatment response. A sensitive SYBR green methylation-specific PCR technique was used to analyze the utility of circulating DNA with CpG island hypermethylation of ESR1, APC, RARB, 14-3-3-sigma and E-cad gene promoter regions as breast cancer biomarkers. Analyses were conducted of preoperative sera from 106 women with breast cancer, 34 with benign breast disease and 74 with no evidence of breast disease and of post-treatment sera from 60 of the breast cancer patients. Mean serum values of methylated ESR1 and 14-3-3-sigma gene promoters significantly differed between breast cancer patients and healthy controls (p = 0.0112 for ESR1 and p = 0.0047 for 14-3-3-sigma). When their results were combined, it was found that hypermethylation of these two genes differentiated between breast cancer patients and healthy controls (p < 0.0001) with a sensitivity of 81% (95% confidence interval: 72-88%) and specificity of 88% (95% CI: 78-94%). Presence of methylated ESR1 in serum of breast cancer patients was associated with the ER negative phenotype (p = 0.0179). Serum hypermethylation at ESR1 and 14-3-3-sigma loci was observed in cancer patients, in situ carcinoma and benign breast disease. No significant differences in methylated ERS1 or 14-3-3-sigma values were observed between pre-surgery and post-treatment measurements. Preliminary clinical applications of this approach have revealed several shortcomings, including a frequent presence of methylated 14-3-3-sigma in sera from women with breast benign disease. These findings cast some doubts on the utility for early cancer diagnosis of highly sensitive techniques to identify hypermethylation of specific gene promoters in DNA extracted from serum. Although numerous issues remain to be resolved, the quantitative measurement of circulating methylated DNA remains a promising tool for cancer risk assessment.

Radiation-induced DNA damage as a predictor of long-term toxicity in locally advanced breast cancer patients treated with high-dose hyperfractionated radical radiotherapy

This 14-year-long study makes a novel contribution to the debate on the relationship between the in vitro radiosensitivity of peripheral blood lymphocytes and normal tissue reactions after radiation therapy. The aims were (1) to prospectively assess the degree and time of onset of skin side effects in 40 prospectively recruited consecutive patients with locally advanced breast cancer treated with a hyperfractionated dose-escalation radiotherapy schedule and (2) to assess whether initial radiation-induced DNA damage in peripheral blood lymphocytes of these patients could be used to determine their likelihood of suffering severe late damage to normal tissue. Initial radiation-induced DNA double-strand breaks (DSBs) were assessed in peripheral blood lymphocytes of these patients by pulsed-field electrophoresis. Acute and late cutaneous and subcutaneous toxicity was evaluated using the Radiation Therapy Oncology Group morbidity score. A wide interindividual variation was observed in toxicity grades and in radiation-induced DNA DSBs in peripheral blood lymphocytes (mean 1.61 +/- 0.76 DSBs/Gy per 200 MBp, range 0.63- 4.08), which were not correlated. Multivariate analysis showed a correlation (P < 0.008) between late toxicity and higher prescribed protocol dose (81.6 Gy). Analysis of the 29 patients referred to 81.6 Gy revealed significantly (P < 0.031) more frequent late subcutaneous toxicity in those with intrinsic sensitivity to radiation-induced DNA DSBs of >1.69 DSBs/Gy per DNA unit. Our demonstration of a relationship between the sensitivity of in vitro-irradiated peripheral blood lymphocytes and the risk of developing late toxic effects opens up the possibility of predicting normal tissue response to radiation in individual patients, at least in high-dose non-conventional radiation therapy regimens.

PARP-1-dependent 3-nitrotyrosine protein modification after DNA damage

3-nitrotyrosine (NO2-Tyr) is thought to be a specific marker of cell injury during oxidative damage. We have evaluated the role of poly(ADP-ribose)polymerase-1 (PARP-1) in protein nitration after treatment of immortalized fibroblasts parp-1+/+ and parp-1-/- with the alkylating agent 2'-methyl-2'-nitroso-urea (MNU). Both cell lines showed increased iNOS expression following MNU treatment in parallel with a selective induction of tyrosine nitration of different proteins. PARP-1 deficient cells displayed a delayed iNOS accumulation, reduced number of nitrated proteins, and a lower global nitrotyrosine "footprint." We have identified the mitochondrial compartment as the major site of oxidative stress during DNA damage, being MnSOD one of the NO2-Tyr-modified proteins, but not in parp-1-/- cells. These results suggest that NO-derived injury can be modulated by proteins involved in the response to genotoxic damage, such as PARP-1, and may account for the limited oxidative injury in parp-1 knockout mice during carcinogenesis and inflammation.

[CD44s Cell surface expression in 55 lung adenocarcinomas. Negative correlation with tumor size and CA125 cytosolic levels]

INTRODUCTION

CD44s belongs to a family of cell adhesion molecules involved in cell adhesion, migration and cell-extracellular matrix interactions. In this work we attempt to study CD44s expression in lung adenocarcinomas and its possible correlation with other clinicobiological parameters.

MATERIAL AND METHODS

Using an EIA, cell surface CD44s levels were determined in 55 lung adenocarcinomas, classified according to clinical stage, histological grade, ploidy and cellular S-phase fraction. CA125 cytosolic concentrations were also assayed.

RESULTS

Forty two adenocarcinomas (76.4%) showed CD44s concentrations > 80 ng/mg prot, and did not differ significantly from those observed in 16 normal samples (93.7%). There were no differences in CD44s expression when clinical stage (I: 24/28, II: 6/9 and III: 12/17), lymph node involvement (N = 245/29, N+: 18/26), ploidy (diploid: 3/5, aneuploid: 32/39), histological grade (I: 6/7, III: 18/26) and cellular S-phase (> 8.8%: 24/31, < or = 8.8%: 17/24) were considered. Positive CD44s tumors had lower CA125 (p: 0.0072) cytosolic levels and a reduced tumor size (p: 0.0093).

CONCLUSIONS

CD44s expressions in lung adenocarcinomas did not correlate with any clinicobiological parameters, but there was a negative correlation between this and reduced tumor size and lower CA125 cytosolic levels.

Assessing the use of p16(INK4a) promoter gene methylation in serum for detection of bladder cancer

OBJECTIVE

This study was undertaken to investigate whether hypermethylation in p16(INK4a) gene promoter could serve as plasma biomarker of bladder cancer.

METHODS AND PATIENTS

We examined the p16(INK4a) status using methylation-specific PCR in 86 cancer patients and 49 controls (31 healthy people and 18 patients with benign urological diseases).

RESULTS

The p16(INK4a) methylation was found in 22% of the serum samples and in 26% of the bladder cancer biopsies; one of them with carcinoma in situ. The presence of hypermethylated p16(INK4a) in serum seems to be a product from tumour cells because a strong statistical association was found between both matched DNA signals (p<0.0001). Using the control group, the presence of methylated p16(INK4a) in the serum of individuals with suspicion of bladder cancer was found to be associated with the tumour presence (p=0.0009). Aberrant p16(INK4a) methylation was also observed in one non-cancer patient, which is undergoing further assessment.

CONCLUSIONS

According with our results, methylation of p16(INK4a) promoter may be involved in the bladder cancer genesis and the presence of p16(INK4a) methylated in serum of these patients could be useful in the cancer diagnosis with values of sensitivity, specificity and positive predictive value of 0.226, 0.950 and 0.98, respectively. These figures support the use of methylated p16(INK4a) as a new class of tumour marker in bladder cancer.

[CYFRA 21.1 cytosol levels in lung adenocarcinomas. Correlation with other clinico-biological parameters]

INTRODUCTION

Cyfra 21.1 are soluble cytokeratin 19 fragments present in several biological fluids. The aim of this work was to study cyfra 21.1 cytosolic levels in lung adenocarcinomas and their possible correlation with other clinical-biological parameters.

PATIENTS AND METHODS

Cyfra 21.1 was determined, using an immunoradiometric assay (CIS BioInternational. France), in 58 tissue samples of lung adenocarcinomas patients. Other parameters included in the study were the following: clinical stage, histological grade, ploidy, S-phase cellular fraction, as well as cathepsin D, CA 125 and hyaluronic acid levels in cytosols. Likewise, AH, erbB2 oncoprotein, CD44s, CD44v5 and CD44v6 levels in cell surfaces were assayed.

RESULTS

Cyfra 21.1 cytosolic levels oscillated between 24.8 and 6,774 ng/mg prot. (median 1,147.5) and were higher (p:0.00074) than those observed in 16 normal lung samples of the same patients. We did not observe any statistically significant differences in cyfra 21.1 values when clinical stage, ploidy, S-phase and histological grade were considered. When lung adenocarcinomas were classified according to cyfra 21.1 positivity, using 1,499 ng/mg prot. as cut-off, which represents the 75th percentile of the whole group, we noted that positive cases had higher levels of cathepsin D (p:0.00218), cytosolic hyaluronic acid (p:0.02947), erbB2 protein (p:0.06272) and CA 125 (p:0.07243) than negative carcinomas.

CONCLUSIONS

These results suggest the possibility that high cytosolic cyfra 21.1 levels could be associated with a poor outcome in lung adenocarcinomas.

Interactions between radiotherapy and endocrine therapy in breast cancer

Whenever radiation therapy is given with curative intent there is the risk of serious damage to normal tissue. This risk increases with the dose of radiation, as does the probability of local tumour control. In the attempt to cure, the doses reach a level that inevitably causes some undesirable adverse effects, ranging from undetectable, or minimal, to unacceptably severe. Over the last few years, a number of reports have suggested that the prediction of normal tissue response after radiotherapy may be achieved by assays on samples withdrawn from the patients prior to treatment, although recent reports have described mixed results. The ability to predict tumour response to anti-hormones in patients with breast cancer has important implications with regard to treatment. Recent discoveries promise to provide individualized treatment options. However, there are no data to support that, used jointly, the combination of radiotherapy and hormone therapy may achieve an enhancement of breast cancer tumour response. Nowadays, development in cancer therapy is increasingly arising out of studies in basic science; its implementation in the hands of clinicians is improving the management of patients with cancer. In addition, as the biological aspects of irradiation and hormonal therapy offer an explanation, at least in part, for the outcome observed in patients with breast cancer after therapy, we have focused this review on trying to analyse the most relevant experimental research about the relative roles of radiotherapy and hormonal therapy, the corresponding side-effects and, taking into account recent advances, future areas of research that we consider of major importance in the field.

[Cytosolic pS2 levels in 154 non-small-cell lung carcinomas. Correlation with other clinical and biological parameters]

INTRODUCTION

pS2 was first identified as an estrogen induced molecule in a breast cancer cell line, but its gene responds to several growth factors and oncogenic proteins. Its main clinical application lies in breast carcinomas, where it is a molecular marker to identify breast cancer patients who will respond to hormone therapy. This study was performed to evaluate the significance of the pS2 cytosolic levels in non small cell lung carcinomas classified according to different clinical and biological parameters. Likewise, the results obtained were correlated with those observed in normal tissues.

MATERIAL AND METHODS

The study group included 154 non small cell lung carcinomas (59 adenocarcinomas and 95 squamous carcinomas) and 54 normal lung samples. Cathepsin D, pS2, neuron specific enolase (NSE) and CA125 cytosolic concentrations were determined, as well as those of epidermal growth factor receptor (EGFR), erbB2 protein, CD44s, CD44v5 and CD44v6 on cell surface membranes. Likewise, clinical stage, histological grade, ploidy and cellular S-phase fraction were also considered as variables of the study.

RESULTS

We observed cytosolic pS2 values greater than 1 ng/mg protein (positive cutoff) in 18/59 adenocarcinomas and in 10/95 squamous carcinomas (p:0.00177). In adenocarcinomas, pS2 positivity was not correlated with any clinical and biological parameters, but positive cases had lower EGFR (p:0.03770) concentrations and higher CA125 (p:0.01902) levels. In squamous carcinomas, pS2 positivity was associated with lower EGFR (p:0.02270) levels and higher erbB2 protein (p:0,00563) concentrations.

CONCLUSIONS

Our results led us to suggest the following: 1) cytosolic pS2 concentrations are higher in tumoral than in normal samples; 2) adenoarcinomas had higher levels than squamous lung carcinomas; 3) in adenocarcinomas, positivity for pS2 is associated with lower EGFR levels and higher CA125 concentrations suggesting a worse outcome, and 4) in squamous lung tumors, positivity for pS2 was associated with lower EGFR and higher erbB2 oncoprotein concentrations, it not being possible to establish its clinical significance, although it may be correlated with a poor prognosis.

Individualization of radiotherapy in breast cancer patients: possible usefulness of a DNA damage assay to measure normal cell radiosensitivity

PURPOSE

The purpose of this study was to determine whether the distribution of sensitivities in breast cancer patients, measured using a DNA damage assay on lymphocytes, is likely to provide sufficient discrimination to enable the reliable identification of patients with abnormal sensitivities.

MATERIAL AND METHODS

Radiosensitivity (x) was assessed in 226 samples of lymphocytes from unselected women with breast cancer and was quantified as the initial number of DNA double-strand breaks (dsb) induced per Gy and per DNA unit (200 Mbp).

RESULTS

The existence of an inter-individual variation in the parameter (x) is described through the range (0.40-4.72 dsb/Gy/DNA unit) of values found, which have been fitted to the mathematical model defined by the log-normal distribution (mu = 0.42+/-0.03; sigma = 0.52+/-0.03; R(2)=0.9475). A total of 189 patients received radiotherapy after surgical treatment. Among them, we have detected 15 patients who developed severe skin reactions and we have compared their radiosensitivity values with the rest of patients treated.

CONCLUSIONS

Our results suggest that DNA initial damage measured on lymphocytes offers an approach to predict the acute response of human normal tissues prior to radiotherapy. Values of x higher than 3.20 dsb/Gy/DNA unit theoretically should correspond to the highly radio-sensitive patients. Using the experimental results, we have calculated the strength of the test by means of the area under the receiver operator characteristic curves (A(Z)) to determine whether the radiosensitivity assay can discriminate between patients according to their radiation response. The value found (A(Z)=0.675+/-0.072) is indicative of a fair-poor discriminating capacity of the test to identify the patients with higher risk of developing a severe acute reaction during the radiotherapy treatment.

[Expression of the adhesion molecule CD44v6 in infiltrating ductal carcinomas of the breast is associated with hormone dependence. Our experience with 168 cases]

In order to investigate the possible hormone-dependence of CD44v6 in human breast cancer, we assayed the concentrations of this isoform in the membrane fraction of 168 invasive ductal carcinomas (IDC) and in 26 normal breast tissue samples, 18 fibradenomas (FAD), 3 fibrocystic disease specimens (FD), 7 mucinous carcinomas and 4 medullary carcinomas using the ELISA method. The results were compared with those of the estrogen (ER) and progesterone (PR) receptors, pS2, tissue type plasminogen activator (t-PA), cathepsin D, epidermal growth factor receptor (EGFR) and c-erbB2/neu oncoprotein concentrations. Menopausal status, size of the tumor in the cases of cancers, axillary lymph node involvement, histologic grade, ploidy, cellular synthesis phase, multifocality and multicentricity were also considered as variables. The cut-off value for CD44v6-positivity was set at 5 ng/mg prt. membrane protein content. 64/138 (38.1%) infiltrating ductal carcinomas scored positive. This was significantly higher than for the normal breast tissue (0/26; p: 0.0001), similar to that seen in the FAD (3/18), fibrocystic disease (0/3), infiltrating mucinous carcinomas (4/7) and lobular (3/15) and significantly lower than for the infiltrating medullary carcinomas (4/4; p: 0.027). There were no significant differences with the other groups of tissues studied. Furthermore, CD44v6-positive IDC showed significantly higher concentrations of ER, PR and cathepsin D and lower (p: 0.051) concentrations of EGFR when compared to their CD44v6-negative counterparts. The significant coexpression of ER, PR and cathepsin D seems to indicate a possible role for hormonal regulation of CD44v6 expression while the role of pS2 and t-PA, estrogen related proteins, was very reduced.

Capillary electrophoresis of DNA damage after irradiation: apoptosis and necrosis

Apoptosis is a type of cellular death but also directly regulates tumorigenesis through different gene expression. This phenomenon is often used as end-point in studies of radio- and chemosensitivity of cancer cells. Restriction DNA fragments have been separated quickly, efficiently and successfully by capillary gel electrophoresis (CGE). In this study CGE has been applied to distinguish between the discrete pattern of degraded DNA produced by apoptosis and randomized DNA breaks produced by ionizing radiation. The influence of different variables has been discussed and an example of fast separation by CGE of the apoptotic fragments produced by UV light treatment is shown.

Histologic grade and CD44 are independent predictors of axillary lymph node invasion in early (T1) breast cancer

BACKGROUND

The detection rate of small, often subclinical breast cancers is increasing in affluent societies. Concomitantly, the demand for more conservative surgical approaches is also increasing among the women affected. Predictors of the absence of nodal invasion would spare many patients with early breast cancer the risks, costs and side effects of lymphadenectomy, and thus treatment with curative intent would be applied using really minimal surgery.

PATIENTS AND METHODS

We reviewed the records of 135 patients with unifocal invasive breast cancers, 2 cm or less in diameter, operated upon at 'Fundación Tejerina-Centro de Patología de la Mama', Madrid, Spain, between January 1993 and December 1997. Full clinical and pathological data were available for all of them, together with estrogen and progesterone receptor determinations, which had been routinely performed in 134 and 133 cases, respectively. Additionally, Ki67, c-erb-B2, p53, nm23, HSP27, HSP60 and CD44std expression was studied on archival, paraffin-embedded tumor material from these same patients by means of immunohistochemistry.

RESULTS

In the univariate analysis, only histologic grade 3 (p < 0.001), Ki67 expression in more than 10% of tumor cells (p = 0.005) and CD44std negativity (p = 0.004) were significantly associated with axillary node involvement. In multivariate analysis, histologic grade 3 and CD44std negativity retained statistical significance, and thus emerged as independent predictors of nodal invasion. The combination of both, furthermore, identified a subgroup in which the axillary nodes were invariably affected.

CONCLUSION

Some pathological and molecular features of small breast cancers were able to predict nodal metastasis significantly. However, none, either alone nor combined, was able to exclude axillary node invasion completely.

[Absence of correlation between the concentrations of carcinoembryonic antigen (CEA) and the tumor growth factor beta 2 (TGFB2) in the two main types of breast macrocysts]

In order to study the possible correlation between carcinoembryonic antigen (CEA) and cellular proliferation, we assayed the concentrations of this substance in the fluid of 77 bening macrocysts of the breast classified according to their Na+/K+ ratio and compared them with those of transforming growth factor beta 2. CEA levels correlated positively and significantly with the cationic ratio, the concentrations of albumin, glucose, Cl- and pH and were higher (range: 2.5-81.5, median 12.8 vs range: 0.4-41.5, median 3.2 ng/ml (p: 0.00000) in type 2 (Na+/K+ > 3) than in type 1 (Na+/K+ < 3) cysts. There was no correlation between CEA and TGFb2, nor between the former and dehydroepiandrosterone sulphate levels. These results led us to suggest that the high CEA concentrations in type 2 cysts seem to be the consequence of loos of cellular differentiation and disruption of the cyst wall lining as well as the acquisition of embryonary properties by the latter as a consequence of a reduced hormonal microenvironment.

[Clinical-biological differences between invasive ductal carcinomas and breast lobular carcinomas. Preliminary results]

In order to know the biological differences between both histological types, we have analyzed some clinical and biological parameters in tissues of women having infiltrating carcinomas (247 ductal (IDCs) 17 and lobular (ILCs) of the breast. Our preliminary results led us to suggest the following. 1) In negative axillary lymph node involvement (N-) patients, ILCs were more frequently associated with diploidy and the existence of multiple foci; likewise, they had higher pS2 cytosolic levels than IDC; 2) in N+ patients, ILC were associated with multicentricity and had higher concentrations of progesterone receptors and 3) these findings could help to explain us the clinical and biological peculiarities, as well as, the clinical outcome of both histological types.

Apoptosis after gamma irradiation. Is it an important cell death modality?

Apoptosis and necrosis are two different forms of cell death that can be induced by cytotoxic stress, such as ionizing radiation. We have studied the importance of apoptotic death induced after treatment with 6 Gy of gamma-irradiation in a panel of eight human tumour cell lines of different radiosensitivities. Three different techniques based on the detection of DNA fragmentation have been used, a qualitative one--DNA ladder formation --and two quantitative approaches--in situ tailing and comet assay. No statistically significant relationship between the two quantitative assays was found (r= 0.327, P = 0.159) so these methods seem to show different aspects of the process of cell death. The presence of the DNA ladder related well to the end-labelling method in that the least amount of end labelling was seen in samples in which necrotic degradation rather than apoptotic ladders were seen. However, as the results obtained by the comet assay are not in agreement with the DNA ladder experiments, we suggest that the distinction between the degraded DNA produced by apoptosis and necrosis may be difficult by this technique. Finally, although apoptosis has been proposed to be dependent on p53 functionality, and this may explain differences in cellular radiosensitivity, no statistically significant relationship was found between these parameters and apoptosis in the eight cell lines studied.

DNA damage and prediction of radiation response in lymphocytes and epidermal skin human cells

The success of radiotherapy in eradicating tumours depends on the total radiation dose, but what limits this dose is the tolerance of the normal tissues within the treatment volume. Studies involving fibroblast survival have demonstrated the theoretical feasibility of a predictive assay of radiation sensitivity, but such an assay is still far from clinical application. Using pulsed-field gel electrophoresis (PFGE), we have quantified the initial "apparent" number of DNA double-strand breaks (dsb) induced by the radiation as an alternative measure of sensitivity in 2 different normal cell types from the same patients, epidermal skin cells and lymphocytes. We found significant inter-individual variation in the measured dsb (1-5 dsb/Gy/DNA unit). We also found a linear correlation between molecular damage in lymphocytes and skin samples from the same patient (slope = 0.83; r = 0.694; p = 0.0001). These results suggest that the initial number of dsb could be used as an indicator of the in vivo response to radiation.

A comparison of p53 and p16 expression in human tumor cells treated with hyperthermia or ionizing radiation

To assess the potential relationship between p53 and p16 proteins in the cellular response to stress, we have examined the levels of these proteins in a series of human tumor cell lines after treatment with either ionizing radiation or hyperthermia. We found that cells with abnormal radiation-induced G1 arrest (non-functional p53) had significantly higher constitutive levels of p16 than cells showing a normal G1 arrest (functional p53). Time-course experiments were done to test the effect of gamma-irradiation on intracellular levels of p16. The pattern of changes in p16 response was similar in all cell lines studied, and p16 expression was not related to cellular sensitivity to radiation or to the level of p53 induction after treatment. We also provide evidence that short-term exposure to high temperature causes p53 accumulation. Hyperthermia-induced p53 accumulation was greatest in those cells exhibiting the highest radiation-induced p53 accumulation, suggesting a possible relationship between p53 induction after these 2 different stresses. p16 synthesis was also induced in different cell lines after heat treatment, and this response was independent of p53 functionality. When we compared the level of p16 expression with the extent of G0/G1 arrest induced by heat, a linear correlation was found, raising the possibility that p16 may be involved in the control of cell cycle progression in response to heat treatment.

Radiosensitivity of human breast cancer cell lines of different hormonal responsiveness. Modulatory effects of oestradiol

Treatments which inhibit or retard progression of the cell through the cell cycle have been reported to reduce the effectiveness of ionizing radiation by increasing cellular radioresistance. We studied cellular radiosensitivity and radiation-induced DNA damage (double-strand break, dsb) in both hormone-sensitive and non-sensitive human breast cancer cell lines. After 72h of culture in an oestradiol-deprived medium, MCF-7 BUS and T47D B8 breast cancer cells showed a significant delay in growth, whereas no effect was seen in EVSA-T cell line. In oestradiol-free medium, MGF-7 BUS cells were arrested mainly in G(zero)/G1 phase (85-90% in G(zero)/G1, 5-7% in S, and 6-8% in G2/M). The growth-delayed MCF-7 BUS cells showed reduced radiosensitivity (survival fraction at 2 Gy, SF2 = 63%; initial DNA damage 1.00 dsb/Gy/DNA unit) in comparison with proliferating cells (SF2 = 33%, initial DNA damage 2.70 dsb/Gy/DNA unit). The radio-protective effect of oestrogen deprivation was abolished by rescuing MCF-7 cells with oestrogen-containing medium. At 24h after rescue, MCF-7 BUS cells reached a cell cycle distribution close to that found under standard culture conditions and their radiosensitivity was correspondingly increased (SF2 = 40%, DNA damage = 2.52 dsb/Gy/DNA unit). Our findings indicate that: (1) sensitivity to radiation and the proportion of proliferating cells are probably related, and (2) differences in radiosensitivity reflect differences in radiation-induced DNA damage.

Relationship between DNA damage, rejoining and cell killing by radiation in mammalian cells

The prevailing hypothesis on the mechanism of radiation-induced cell killing identifies the genetic material deoxyribonucleic acid (DNA) as the most important subcellular target at biologically relevant doses. In this review we present new data and summarize the role of the DNA double-strand breaks (dsb) induced by ionizing radiation and DNA dsb rejoining as determinants of cellular radiosensitivity. When cells were irradiated at high dose-rate, two molecular end-points were identified which often correlated with radiosensitivity: (1) the apparent number of DNA dsb induced per Gy per DNA unit and (2) the half-time of the fast component of the DNA dsb rejoining kinetics. These two molecular determinants, not mutually exclusive, may be linked through a common factor such as the conformation of DNA.

Relationship between p53 status and radiosensitivity in human tumour cell lines

We examined the relationship between p53 levels before and after irradiation, radiation-induced cell cycle delays, apoptotic cell death and radiosensitivity in a panel of eight human tumour cell lines. The cell lines differed widely in their clonogenic survival after radiation, (surviving fraction at 2 Gy: SF2=0.18-0.82). Constitutive p53 protein levels varied from 2.2 +/- 0.4 to 6.3 +/- 0.3 optical density units (OD) per 10(6) cells. p53 after irradiation (6 Gy) also varied between the cell lines, ranging from no induction to a 1.6-fold increase in p53 levels 4 h after treatment. p53 function was also assessed by G1 cell cycle arrest after irradiation. The cellular response to radiation, measured as G0/G1 arrest, and the induction of apoptosis were in good agreement. However, a trace amount of DNA ladder formation was found in two cell lines lacking G1 arrest. Overall cellular radiosensitivity correlated well with the level of radiation-induced G1 arrest (correlation coefficient r=0.856; P=0.0067), with p53 constitutive levels (r=0.874, P=0.0046), and with p53 protein fold induction (r=-0.882, P=0.0038). Our data suggest that (1) the constitutive p53 level, (2) G1 arrest after irradiation, or (3) the p53 protein response to radiation may be good predictive tests for radiosensitivity in some cell types.

Relationship between doxorubicin cell sensitivity, drug-induced DNA double-strand breaks, glutathione content and P-glycoprotein in mammalian tumor cells

We have measured the cytotoxic effect of 1 h exposure to doxorubicin (DOX) on a panel of tumor cell lines. Cellular effects were measured by monolayer colony-forming assay and a colorimetric cytotoxicity assay. As parameters of chemosensitivity we used two different end-points: the dose of DOX that reduces to 50% the number of colonies (ID50) and the dose of DOX that reduces the final optical density to 50% of the control value (IC50). There was a significant correlation between both chemosensitivity indices (r = 0.886, p = 0.0034). DOX-induced DNA double-strand breaks (dsb) were evaluated using pulsed-field gel electrophoresis (PFGE) and compared with cellular effects, P-glycoprotein expression (P-170) and intracellular glutathione (GSH) levels. Our results showed a relationship between the slope of DNA dsb dose-response curves and the percentage of cells that express P-170 (r = -0.957, p = 0.0002). Our study also detects a positive relationship between cellular chemosensitivity parameters and GSH content [ID50 versus GSH (r = 0.794, p = 0.0186), IC50 versus GSH (r = 0.790, p = 0.0198)] in our panel of cell lines.

Radiation-induced DNA double-strand break rejoining in human tumour cells

Five established human breast cancer cell lines and one established human bladder cancer cell line of varying radiosensitivity have been used to determine whether the rejoining of DNA double-strand breaks (dsbs) shows a correlation with radiosensitivity. The kinetics of dsb rejoining was biphasic and both components proceeded exponentially with time. The half-time (t1/2) of rejoining ranged from 18.0 +/- 1.4 to 36.4 +/- 3.2 min (fast rejoining process) and from 1.5 +/- 0.2 to 5.1 +/- 0.2 h (slow rejoining process). We found a statistically significant relationship between the survival fraction at 2 Gy (SF2) and the t1/2 of the fast rejoining component (r = 0.949, P = 0.0039). Our results suggest that cell lines which show rapid rejoining are more radioresistant. These results support the view that, as well as the level of damage induction that we have reported previously, the repair process is a major determinant of cellular radiosensitivity. It is possible that the differences found in DNA dsb rejoining and the differences in DNA dsb induction are related by a common mechanism, e.g. conformation of chromatin in the cell.

Initial radiation-induced DNA damage in human tumour cell lines: a correlation with intrinsic cellular radiosensitivity

The role of the initial DNA double-strand breaks (dsb) as a determinant of cellular radiosensitivity was studied in human breast and bladder cancer cell lines. Cell survival was measured by monolayer colony-forming assay as appropriate and differences in radiosensitivity were seen (alpha-values ranged from 0.12 to 0.54). After pulsed-field gel electrophoresis (PFGE) the initial slopes of dose-response curves were biphasic with a flattening of the curves above 30 Gy. When the frequency of DNA dsb induction was assessed using a mathematical model based on the DNA fragment size distribution into the gel lane, we found a statistically significant relationship between the number of DNA dsb induced and the corresponding alpha-values and fraction surviving after 2Gy (P = 0.0049 and P = 0.0031 respectively). These results support the view that initial damage is a major determinant of cell radiosensitivity.