Adherence of older people to a multidimensional program to improve health-related quality of life and functional capacity.

BACKGROUND: The adherence of the elderly to therapeutic programs, either they are pharmacological or psychosocial, is generally low. OBJECTIVE: Identifying predictive variables of adherence of a social program from elderly with multifunctional independence or mild dependence. METHOD: Prospective longitudinal design with 104 elderly participants in a social program. The inclusion criteria were: to participate in a social program for elderly, present functional independence or mild dependence, without depression clinically confirmed. Descriptive analyzes were performed with the study variables in addition to hypothesis testing and linear and logistic regression models to identify predictive variables of adherence. RESULTS: 22% of the participants met the minimum adherence, observing better compliance in younger people (p = 0.004), among those who had a better Health-Related Quality of Life (p = 0.036) and better health literacy levels (p = 0.017). According to a linear regression model, the variables associated with adherence were: social program of origin (OR = 5,122), perception of social support (OR = 1,170), cognitive status (OR = 2,537). CONCLUSION: The level of adherence of the older people of the study can be evaluated as low, which is consistent with the findings of the specialized literature. The variables identified with predictive capacity on adherence were social program of origin, a condition that can be incorporated into the design of the interventions in order to facilitate territorial equity. It is also important to highlight the importance of health literacy and the risk of dysphagia in the level of adherence.

Invasive meningococcal disease in Chile seven years after ACWY conjugate vaccine introduction.

BACKGROUND: A serogroup W (MenW) outbreak in Chile prompted a meningococcal vaccination campaign using tetravalent meningococcal-conjugate vaccines (MCV-ACWY) in children since 2012, followed by its introduction into the National Immunization Program (NIP) in toddlers from 2014. Direct protection was observed, but no indirect effects in other age-groups were evidenced. The aim of this study was to describe invasive meningococcal disease (IMD) cases in Chile between 2009 and 2019, and its trend after the introduction of MCV-ACWYs. METHODS: IMD cases, cumulative incidence per 100,000 inhabitants, CFR, and vaccination uptake were described. Data were obtained from the Public Health Institute and NIP. RESULTS: Overall-IMD cases increased in 2009-2014 period, followed by a decline in 2015-2019, focused in infants, children <5 years and people ≥60 years. Serogroup B (MenB) and MenW alternate its predominance. Median overall incidence was 0.6/100,000, increasing from 0.6/100,000 in 2009 to 0.8/100,000 in 2014, later decreasing to 0.4/100,000 in 2019. Median incidences for MenB, serogroup C (MenC) and Y (MenY) were 0.25/100,000, <0.01/100,000 and <0.01/100,000, respectively. Median MenW incidence was 0.53/100,000, increasing from 0.01/100,000 in 2009 to 0.56/100,000 in 2014, followed by a constant decline to 0.12 in 2019. Infants, children <5 years and adults ≥60 years were affected the most, with median incidences of 9.7, 0.9 and 0.93, decreasing to 1.3, 0.1 and 0.1/100,000 in 2019, respectively. Median overall-CFR was 19%, 7.5% for MenB and 24.5% for MenW. Median MCV-ACWY uptake was 93% CONCLUSION: Overall-IMD, MenW cases and incidence declined since 2015 after the MCV-ACWY introduction, while MenB, MenC and MenY have been stable. MenW incidence declined in all age groups, including non-immunized infants and people >60 years. Further analysis and a longer period of observation are needed to have a more robust conclusion about this epidemiological trend. By 2019, CFR remains high.

Meningococcal invasive disease by serogroup W and use of ACWY conjugate vaccines as control strategy in Chile.

BACKGROUND: Serogroup causing invasive meningococcal disease (IMD) can change abruptly, as it occurred in Chile when serogroup predominance switched from MenB to MenW in 2012. As a response, a national vaccination strategy was implemented since 2012 using tetravalent meningococcal-conjugate vaccines (MCV-ACWY) in children 9 months through 4 years of age. The aim of this study was to describe IMD cases by MenW in Chile 2009-2016, and to analyse its trend after the introduction of MCV-ACWY. METHODS: Descriptive study of IMD cases in Chile, period 2009-2016. Cumulative incidence and mortality rate per 100,000 inhabitants, and case fatality rate (CRF) were used for descriptive analysis. Linear regression was used for post-intervention trend analysis. RESULTS: In 2012, MenW, mainly ST-11 cc, became predominant. MenW incidence rose from 0.01/100,000 inhabitants in 2009 to a maximum of 0.6/100,000 in 2015. Infants and adults 80 years of age and older were mostly affected, with an incidence peak of 9.7/100,000 and 1.6/100,000, respectively, in 2015. In the group of children from 1 to 4 years of age MenW incidence declined from 1.3/100,000 in 2012 to 0.1/100,000 in 2016, a 92.3% reduction after vaccination implementation. In the same period and age-cohort, CFR decreased from 23% to 0%. High mortality rates concentrated in infants and adults 80 years of age and over. CONCLUSION: MenW became predominant in Chile since 2012. IMD cases increased steadily from 2009 to 2016, with higher incidence, CFR and mortality concentrating in infants and people 80 years of age and older. MCV-ACWY provided direct protection against MenW, reducing its incidence after mass meningococcal vaccine implementation. Indirect effects of vaccination are not yet observed.

Renin-angiotensin system-regulating aminopeptidase activities are modified in the pineal gland of rats with breast cancer induced by N-methyl-nitrosourea.

OBJECTIVE: Pineal function has been considered particularly as a neuroendocrine modulator in hormone responsive tumors, like the hormone-dependent mammary tumors. The complexity of the gland function, moreover, is denoted by the presence of a local renin-angiotensin-system (RAS) that regulates melatonin biosynthesis. Classically, angiotensin II (Ang II) has been considered as the effector peptide of the RAS, but Ang II is not the only active peptide. Several of its degradation products, including angiotensin III (Ang III) and angiotensin IV (Ang IV) also possess biological functions. These peptides are formed via the activity of several aminopeptidases. Our aim is to know their role in the regulation of pineal RAS and breast cancer. DESIGN: Aminopeptidase N (APN), aminopeptidase B (APB) and aminopeptidase A (aspartyl- and glutamyl-aminopeptidase, APA) activities are measured in the pineal gland of rats with breast cancer induced by N-methyl nitrosourea (NMU). METHODS: Aminopeptidase activities were measured fluorimetrically using their corresponding aminoacyl-beta-naphthylamides as substrates. RESULTS: Specific APN and APB activities in pineal gland of controls and NMU-treated rats were not modified. Aspartyl aminopeptidase activity significantly decreased in NMU-treated rats when compared with control group. On the contrary, glutamyl aminopeptidase activity did not show significant differences between groups. CONCLUSIONS: We propose that the local RAS in pineal gland is modified in rats with breast cancer induced by NMU through the inhibition of AspAP activity, which may lead to increased levels of Ang II. Ang II could be responsible of the overproduction of melatonin, supporting a mechanism to restrain the promotion and/or progression of breast cancer.

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.

Pyrrolidon carboxypeptidase activities in the hypothalamus-pituitary-thyroid and hypothalamus-pituitary-ovary axes of rats with mammary gland cancer induced by N-methyl nitrosourea.

Pyrrolidon carboxypeptidase is an omega-peptidase that hydrolyses N-terminal pyroglutamyl residues from biologically active peptides such as gonadotropin-releasing and thyrotrophin-releasing hormones. We previously described a decrease in both rat and human pyrrolidon carboxypeptidase activity with breast cancer, suggesting that gonadotropin-releasing hormone may be an important local intracrine, autocrine and/or paracrine hormonal factor in the pathogenesis of breast cancer while playing a role in the tumoral process. However, the other susceptible substrate of pyrrolidon carboxypeptidase, thyrotrophin-releasing hormone, may also be modified with breast cancer, supporting an association between breast cancer and thyroid disorders. The present work analyses soluble and membrane-bound pyrrolidon carboxypeptidase activities in the hypothalamus-pituitary-thyroid and hypothalamus-pituitary-ovary axes in N-methyl nitrosourea-induced breast cancer in rats. Our aim was to determine the possible relationship between gonadotropin-releasing hormone and thyrotrophin-releasing hormone regulation through pyrrolidon carboxypeptidase activity. We propose that pyrrolidon carboxypeptidase activity dysregulation at various local and systemic levels may participate in the initiation, promotion and progression of breast cancer induced in rat by N-methyl nitrosourea through the increase in gonadotropin-releasing hormone. Since pyrrolidon carboxypeptidase activity also acts on thyrotrophin-releasing hormone, the dysregulation of this enzyme's activity could indirectly affect hypothalamus-pituitary-thyroid axis function, and thus potentially represent a link between the diseases of thyroid and breast cancer.

Serum oxytocinase activity is related to tumor growth parameters in N-methyl nitrosourea induced rat breast cancer.

Oxytocinase has been reported to hydrolyse the peptide hormone oxytocin (OT). We have previously described changes in oxytocinase activity in human breast cancer, where a highly significant increase occurred in tumoral tissue. In the present work, we analysed oxytocinase activity in serum of rats with breast cancer induced by N-methyl-nitrosourea (NMU). We also correlated these data with the number and size of tumors and the body weight of the animals to evaluate the putative value of this activity as a biological marker of the disease. Our results confirm the involvement of OT in carcinogenesis and suggest a mayor role for oxytocinase activity in the development of breast cancer.

Serum pyrrolidone carboxypeptidase activity in N-methyl-nitrosourea induced rat breast cancer.

Pyrrolidone carboxypeptidase (Pcp) (E.C. 3.4.19.3) is an omega peptidase widely distributed in animal fluids and tissues and hydrolyses N-terminal pyroglutamic residues from biologically active peptides such as gonadotropin releasing hormone (GnRH). Previous results obtained by us showed a decrease in human breast cancer Pcp activity, suggesting that this enzyme activity or its putative substrates may play a major role in breast cancer pathogenesis. The aim of the present work is to analyse serum Pcp activity in N-methyl-nitrosourea (NMU) induced rat mammary tumours using pyroglutamyl-beta-naphthylamide as substrate. Serum Pcp activity was significantly lower in NMU-treated rats than in controls. Moreover, multiple regression analysis showed a significant correlation between Pcp activity and the number and size of tumours and the body weight of the animals. Since NMU-induced carcinomas are mainly oestrogen-dependent, the decrease observed in Pcp activity may reflect an increase in circulating levels of GnRH that lead to an increase in gonadal steroid hormones production responsible, at least in part, for the initiation and promotion of the disease.

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.

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.

[Achievements and challenges of the expanded immunization program in the Americas]. / Logros y desafíos del programa ampliado de inmunizaciones en la región de las Américas.

The Expanded Program on Immunization (EPI) was initiated in 1974 in The Americas, based on the WHA 2757 resolution passed by the World Assembly of Health. Its purpose was to improve immunization coverage and to decrease morbidity and mortality caused by vaccine preventable diseases through vaccination. Specific goals were to eradicate in determined time periods poliomyelitis, measles, neonatal tetanus, to eliminate tuberculous meningitis in children four years and younger, diphtheria, and tetanus. This article presents up to date information on vaccination coverage trends between 1990 and 1998 in 13 countries of the American Region, briefly describes implementation of surveillance programs required for appropriate monitoring of vaccine impact, and discusses the changes observed in morbidity attributable to vaccine preventable disease in these countries during four periods, 1968 before the existence of EPI, 1978, four years after its introduction, 1988 and 1998. Although much remains to be done, the impact of EPI in the Americas has been outstanding in decreasing morbidity caused by vaccine preventable diseases.

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.

Variation in sensitizing effect of caffeine in human tumour cell lines after gamma-irradiation.

BACKGROUND AND PURPOSE: We have investigated whether the protective role of the G2 checkpoint has increasing importance when the p53-dependent G1 checkpoint is inactivated. MATERIALS AND METHODS: We have studied the differential effect of caffeine by clonogenic assays and flow cytometry in three human tumour cell lines with different functionality of p53 protein. RESULTS: The radiosensitizing effect of caffeine (2 mM) expressed itself as a significant decrease in surviving fraction at 2 Gy and a significant increase in alpha-values in RT112 and TE671, both with non-functional p53. However, no radiosensitizing effect was seen in cells with a normal p53 function (MCF-7 BUS). Two millimoles of caffeine also caused important changes in the cell cycle progression after irradiation. MCF-7 BUS showed a G1 arrest after irradiation and an early G2 arrest but those cells that reached the second G2 did not arrest significantly. In contrast, TE671 exhibited radiosensitization by caffeine, no G1 arrest, a G2 arrest in those cells irradiated in G2, no significant accumulation in the second G2 but an overall delay in release from the first cell cycle, which could be abrogated by caffeine. RT112 was similar to TE671 except that the emphasis in a G2 arrest was shifted from the block in cells irradiated in G2 to those irradiated at other cell cycle phases. CONCLUSION: The data presented confirm that p53 status can be a significant determinant of the efficacy of caffeine as radiosensitizer in these tumour cell lines, and document the importance of the G2 checkpoint in this effect.

[Immune status against measles and rubella among 4 Chilean groups of different ages]. / Estado inmunitario de 4 grupos de edad de población chilena contra sarampión y rubeola.

BACKGROUND: Results of clinical and epidemiological studies confirm that no cases of measles have occurred in Chile since 1993. However, since covering of vaccination programs do not exceed 95%, an immunological surveillance for this disease is warranted. AIM: To know the immune status against measles and rubella in the Chilean population. MATERIAL AND METHODS: A serological census of a representative sample of communities with high (90% or more) or low immunization coverings was performed. Four sub samples along the country were selected: 122 children aged 18 months of age (stratum A), 1,276 children attending the first years of basic school (stratum B), 899 teenagers in their last high school year (stratum C) and 399 women attending a family planning clinic (stratum D). IgG antibodies against measles and rubella were measured using ELISA and hemagglutination inhibition techniques, respectively. RESULTS: Antibodies against measles and rubella were found in 96% and 94% of study subjects. No differences in these titres were found between different strata or communities with high or low vaccination covering. There is a high percentage of positive antibodies against measles among children of 18 months of age and a high percentage of antibodies against rubella among teenagers and women in family planning. Only 3% of the sample had not received any vaccine at the moment of the study. CONCLUSIONS: The high prevalence of antibodies against rubella allows to conclude that it is not necessary to consider this antigen in the next vaccination campaign. Due to the high prevalence of antibodies against measles, only the population older than 20 years old should be affected by the disease if this virus enters the country.

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.

Economisation of vaccination against Haemophilus influenzae type b: a randomised trial of immunogenicity of fractional-dose and two-dose regimens.

BACKGROUND: The cost of Haemophilus influenzae type b (Hib) conjugate vaccines has limited their use in non-industrialised countries. To identify more economical vaccination schedules, we carried out a randomised trial of the immunogenicity of alternative regimens to the standard three-dose series. METHODS: 627 Chilean infants were randomly allocated to one of four regimens with either Hib polysaccharide-tetanus toxoid conjugate vaccine (PRP-T) or Hib oligosaccharide-diphtheria mutant toxoid conjugate vaccine (PRP-CRM197), for a total of eight groups. All infants receive diphtheria-tetanus-pertussis (DTP) vaccine at ages 2, 4, and 6 months. The regimens included three full doses, three fractional doses consisting of one half or one third of the full dose, and a regimen of two full doses (at age 4 and 6 months). The primary outcome was the proportion of infants with serum anti-polyribosylribitol phosphate (PRP, the type b capsular polysaccharide) concentrations of 0.15 microg/mL or more at age 8 months. FINDINGS: 93% (95% CI 85-98) of infants vaccinated with three full doses of PRP-T or PRP-CRM197 (95% CI 84-98) achieved anti-PRP concentrations of 0.15 microg/mL or more at age 8 months, compared with 91% (83-96) to 100% (95-100) of infants immunised with any fractional-dose regimen. Of the infants vaccinated with two doses of PRP-T or PRP-CRM197, 99% (93-100) and 87% (77-93) developed anti-PRP concentrations of 0.15 microg/mL or more, respectively. INTERPRETATION: 91% (83-96) to 100% (95-100) of infants immunised with one-half or one-third of a full dose of Hib conjugate developed protective antibody concentrations. Carrier priming with DTP may make two-dose schedules an option in some places. These alternative regimens could bring the cost of Hib vaccines within reach of countries that currently cannot afford them.

[Comparative study of the efficacy of two types of BCG vaccines administered in different doses]. / Estudio comparativo de la eficacia de dos tipos de vacunas BCG administradas en dosis diferentes.

BACKGROUND: In 1993, WHO and UNICEF recommended the administration of 0.05 ml doses of BCG, instead of 0.1 ml, to newborns. This recommendation was adopted by the Chilean Ministry of Health, using the Mérieux vaccine. Subsequently, different Health Services detected a high percentage of children without BCG scar at the time of their growth and development control. AIM: To assess the efficacy of BCG vaccination in a double blind randomized fashion, using two vaccine types and different doses. PATIENTS AND METHODS: Newborns of two public hospitals of Santiago were randomly assigned to receive the Tokio or Mérieux BCG strains in doses of 0.05 or 0.1 ml. Ninety five to 125 days after vaccination, vaccine scar was measured and inmunogenicity was assessed using the tuberculin test. RESULTS: Six hundred newborns (150 in each group) were included in the protocol and results were assessed in 408. The percentage of children with a PPD reaction of 0 mm was 9.3, 3.7, 7.8 and 0% with the Mérieux vaccine in doses of 0.1 ml, Tokio vaccines in doses of 0.1 ml, Mérieux vaccine in doses of 0.05 ml and Tokio vaccine in doses of 0.05 ml, respectively. In the same groups the scar diameters were 6.4 +/- 3.4, 7.3 +/- 2.7, 5.6 +/- 2.8 and 7.3 +/- 2.9 mm. The observed differences for each group are significant, depending on the type of strain and dose, but favoring the Tokio type of vaccine. CONCLUSIONS: The BCG scar diameters obtained in this study are similar to those obtained in previous works in 1984 and 1986. This scar is the evidence of vaccination that nurses detect in health controls. Therefore the use of 0.1 doses for vaccination, that result in better scars and PPD response, is recommended.

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.