Diabetes mellitus mortality in Spanish cities: Trends and geographical inequalities

AIM

To analyze the geographical pattern of diabetes mellitus (DM) mortality and its association with socioeconomic factors in 26 Spanish cities.

METHODS

We conducted an ecological study of DM mortality trends with two cross-sectional cuts (1996-2001; 2002-2007) using census tract (CT) as the unit of analysis. Smoothed standardized mortality rates (sSMR) were calculated using Bayesian models, and a socioeconomic deprivation score was calculated for each CT.

RESULTS

In total, 27,757 deaths by DM were recorded, with higher mortality rates observed in men and in the period 1996-2001. For men, a significant association between CT deprivation score and DM mortality was observed in 6 cities in the first study period and in 7 cities in the second period. The highest relative risk was observed in Pamplona (RR, 5.13; 95% credible interval (95%CI), 1.32-15.16). For women, a significant association between CT deprivation score and DM mortality was observed in 13 cities in the first period and 8 in the second. The strongest association was observed in San Sebastián (RR, 3.44; 95%CI, 1.25-7.36). DM mortality remained stable in the majority of cities, although a marked decrease was observed in some cities, including Madrid (RR, 0.67 and 0.64 for men and women, respectively).

CONCLUSIONS

Our findings demonstrate clear inequalities in DM mortality in Spain. These inequalities remained constant over time are were more marked in women. Detection of high-risk areas is crucial for the implementation of specific interventions.

FOXM1 allows human keratinocytes to bypass the oncogene-induced differentiation checkpoint in response to gain of MYC or loss of p53

Tumour suppressor p53 or proto-oncogene MYC is frequently altered in squamous carcinomas, but this is insufficient to drive carcinogenesis. We have shown that overactivation of MYC or loss of p53 via DNA damage triggers an anti-oncogenic differentiation-mitosis checkpoint in human epidermal keratinocytes, resulting in impaired cell division and squamous differentiation. Forkhead box M1 (FOXM1) is a transcription factor recently proposed to govern the expression of a set of mitotic genes. Deregulation of FOXM1 occurs in a wide variety of epithelial malignancies. We have ectopically expressed FOXM1 in keratinocytes of the skin after overexpression of MYC or inactivation of endogenous p53. Ectopic FOXM1 rescues the proliferative capacity of MYC- or p53-mutant cells in spite of higher genetic damage and a larger cell size typical of differentiation. As a consequence, differentiation induced by loss of p53 or MYC is converted into increased proliferation and keratinocytes displaying genomic instability are maintained within the proliferative compartment. The results demonstrate that keratinocyte oncogene-induced differentiation is caused by mitosis control and provide new insight into the mechanisms driving malignant progression in squamous cancer.

Cyclin E drives human keratinocyte growth into differentiation

Human epidermis is continuously exposed to environmental mutagenic hazard and is the most frequent target of human cancer. How the epidermis coordinates proliferation with differentiation to maintain homeostasis, even in hyperproliferative conditions, is unclear. For instance, overactivation of the proto-oncogene MYC in keratinocytes stimulates differentiation. Here we explore the cell cycle regulation as proliferating human keratinocytes commit to terminal differentiation upon loss of anchorage or overactivation of MYC. The S-phase of the cell cycle is deregulated as mitotic regulators are inhibited in the onset of differentiation. Experimental inhibition of mitotic kinase cdk1 or kinases of the mitosis spindle checkpoint Aurora B or Polo-like Kinase, triggered keratinocyte terminal differentiation. Furthermore, hyperactivation of the cell cycle by overexpressing the DNA replication regulator Cyclin E induced mitosis failure and differentiation. Inhibition of Cyclin E by shRNAs attenuated the induction of differentiation by MYC. In addition, we present evidence that Cyclin E induces DNA damage and the p53 pathway. The results provide novel clues for the mechanisms committing proliferative keratinocytes to differentiate, with implications for tissue homeostasis maintenance, HPV amplification and tumorigenesis.

Chronic liver disease and cirrhosis mortality and social deprivation: a spatial analysis in small areas of Madrid region

OBJECTIVES

To study census-tract distribution of chronic liver disease and cirrhosis mortality in the Madrid Region and its association with socio-economic deprivation.

METHODS

Cross-sectional, ecological (3906 census-tract) study, using mortality data for 1996-2003 and a deprivation index drawn up on the basis of 2001 census data. Standardised mortality ratios were calculated taking Spanish rates for 2001 as reference. Smoothed census-tract relative risks were computed using the Besag-York-Mollie model. Relative risks (RRs) of dying and their 95% credibility intervals (95% CIs) were calculated according to quartiles of the deprivation index (with the fourth quartile -Q- of the indicator being the most unfavourable situation). Maps were plotted depicting the distribution of the posterior probability of RR > 1.

RESULTS

Census tracts with a high risk of mortality were detected, mostly located in the centre and on the eastern, south-eastern and south-western fringes of the city of Madrid. Mortality increased with deprivation. RRs of mortality according to quartíles of the deprivation index were: Q2 = 1.5 (CI: 1.3-1.6), Q3 = 1.9 (CI:1.7-2.2) and Q4 = 2.5 (CI:2.2-2.8) for men; and Q2 = 1.3 (CI:1.1-1.5), Q3 = 1.5 (CI:1.3-1.7) and Q4 = 1.6 (CI:1.3-1.8) for women.

CONCLUSIONS

This small-area study enabled census tracts with excess mortality eligible for a special public health intervention to be identified, and their association with socio-economic deprivation to be confirmed.

Census tract socioeconomic and physical environment and cardiovascular mortality in the Region of Madrid (Spain)

BACKGROUND

Features of the area might contribute to differences in cardiovascular mortality. The census tract distribution of ischaemic heart disease (IHD) and cerebrovascular disease mortality in the Region of Madrid and its association with deprivation and environmental variables were examined in this study.

METHODS

Cross-sectional, ecological study covering 3906 census tracts (median of around 1000 inhabitants), using mortality data (population aged <75 years) for 1996-2003, as well as socioeconomic deprivation and other environmental indicators (subjective perceptions of pollution, background noise, lack of green spaces and delinquency) drawn from the 2001 census. Standardised mortality ratios were calculated. Smoothed census tract relative risks were calculated using the Besag-York-Mollié model. Relative risks (RRs) of dying and their 95% credibility intervals (95% CI) were calculated according to the indicators considered (with the fourth quartile, Q, being the most unfavourable situation). Maps were plotted depicting the distribution of the posterior probability of RR>1.

RESULTS

Census tracts with excess mortality were mostly located in the city of Madrid. Mortality increased with deprivation: RRs of IHD and stroke mortality in Q4 with respect to Q1 were 1.42 (95% CI 1.31 to 1.54) and 1.66 (95% CI 1.45 to 1.88) for men, and 1.54 (95% CI 1.33 to 1.79) and 1.52 (95% CI 1.29 to 1.76) for women respectively. Associations with deprivation decreased only slightly when perceived lack of green spaces and delinquency were included in the model. In men, subjective perceptions of areas remained associated with cardiovascular mortality after adjustment for deprivation.

CONCLUSION

Deprivation and subjective perceptions of physical environmental characteristics are ecologically associated with cardiovascular disease mortality.

Prevention program for disturbed eating and body dissatisfaction in a Spanish university population: a pilot study

A pilot study was carried out in university students to evaluate the effect of a health promotion program for eating disturbances and body dissatisfaction. A subgroup of 135 medical students of both sexes in their second year was selected. There were divided in three groups, high-risk students (EDI >40) and low-risk students (EDI <40) who participated in the program and nonparticipants as comparison group. Program had a total of 16 workshops of 90 min. A year later the different assessment measurements were compared, body image, attitudes and eating behaviours, psychopathological levels and self-esteem. Differences by gender were found on the impact of the intervention. The program presented a statistical significant improvement in body-image satisfaction, eating attitudes only in high-risk female students in the intervention group. This pilot program for eating disorder prevention in university populations can be considered effective, mainly in female populations at risk for developing an eating disorder.

Population at risk for eating disorders in a Spanish region

OBJECTIVE

To estimate the prevalence of adolescent population at risk for eating disorders (EDs), to examine gender differences and their association with non-psychotic mental disorders.

METHODS

Cross-sectional study using an anonymous, self-reported questionnaire in the classroom and measurement of weight and height in a representative sample of 4334 teenagers of both sexes. A definition of population at risk for EDs has been established, that differentiates those with dieting criteria and those with binge-purge eating behaviour criteria. This definition includes a combination of weight, behaviour, Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria, and Eating Disorder Inventory (EDI) results. The General Health Questionnaire-28 (GHQ-28) was used to assess non-psychotic mental disorders.

RESULTS

The prevalence of population at risk for EDs was 2.2% (95% CI: 1.6-2.8) for men and 15.3% (95% CI: 13.8-16.9) for women. The prevalence rate of combining both ED risk and mental disorder was 0.8% (95% CI: 0.4-1.2) for men and 9.9% (95% CI: 8.6-11.2) for women. Non-psychotic mental disorders were more prevalent in the population at risk for EDs than in the rest of the population.

CONCLUSIONS

A considerable proportion of adolescent females have eating problems and non-psychotic mental disorders. Their male counterparts also suffer from these disorders, however, a different pattern is followed.

The EMECAM project: a multicentre study on air pollution and mortality in Spain: combined results for particulates and for sulfur dioxide

OBJECTIVE

The EMECAM study is a collaborative effort to evaluate the impact of air pollution on mortality in Spain. In this paper the combined results are presented for the short term effects of particulates and sulfur dioxide on both daily mortality for all and for specific causes.

METHODS

The relation between daily mortality for all causes, cardiovascular diseases, and respiratory diseases, and air pollution for particulates (daily concentrations) and SO(2) (24 and 1 hour concentrations) was assessed in 13 Spanish cities for the period 1990-6. With a standardised method, magnitude of association in each city was estimated by Poisson regression in a generalised additive model. Local estimates were obtained from both single and two pollutant analyses. Lastly, combined estimates for each cause and pollutant were obtained.

RESULTS

For combined results, in single pollutant models a 10 microg/m(3) increase in the concentration of the mean of the concurrent and one day lag for black smoke was associated with a 0.8% (95% confidence interval (95% CI) 0.4 to 1.1%) increase in total mortality. The estimates for total suspended particles (TSPs) and particulate matter of aerodynamic diameter <10 microm (PM(10)) and total mortality were slightly lower. The same increase in concentrations of SO(2) was associated with a 0.5% increase in daily deaths. For groups of specific causes, higher estimations were found, specially for respiratory conditions. Peak concentrations of SO(2) showed significant associations with the three groups of mortality. When two pollutant analyses were performed, estimates for particulates, specially for black smoke, did not substantially change. The estimates for daily concentrations of SO(2) were greatly reduced, but, on the contrary, the association with peak concentrations of SO(2) did not show any change.

CONCLUSIONS

There is an association between mortality and pollution through particulates among city populations in Spain. Peak rather than daily concentrations of SO(2) were related to mortality. Results suggest that populations in Spanish cities are exposed to health risks derived from air pollution.

[Validation of self-reported weight and height in an adolescent population]

INTRODUCTION

The aim of this study was to examine the relationship between self-reported population in order to evaluate the validity of self-reported measures for the purpose of estimating the prevalence of low (less-than-or-equal 15th percentile) and high (greater-than-or-equal 85th percentile) body mass index (BMI) in the study population.

SUBJECTS AND METHOD

Information on self-reported and objective weight and height was obtained from a representative sample of 3,244 adolescents, aged 15-18 years, in secondary education schools in the Autonomous Community of Madrid. We calculated the mean relative error; the correlation between subjective and objective parameters, sensitivity, specificity and predictive value positive of low and high BMIs.

RESULTS

The mean relative errors were as follows: weight: +0.07% for males versus and 0.79% for females; height, +0.51% for males versus +0.98% for females; BMI: 0.88% for males versus 2.63% for females. The correlation between self-reported and objective BMI was 0.87 for males and 0.90 for females. The prevalence of high BMI was underestimated by 34.1% and 34.4% of females white that of low BMI was overestimated by 10.7% of males and 14.8% of females.

CONCLUSION

Analysis of BMI as a continuous variable, based on self-reported weight and height measurement data, entails a small margin of error. However, its use as a categorical variable involves a considerable underestimate of the prevalence of high BMI, and an smaller overestimate of the prevalence of low BMI.

Switch from p53 to MDM2 as differentiating human keratinocytes lose their proliferative potential and increase in cellular size

p53 transcription factor is mutated in most skin cell carcinomas and in more than 50% of all human malignancies. One of its transcriptional targets is MDM2, which in turn down-regulates p53. The role of the p53/MDM2 regulatory loop upon genotoxic stress is well documented, but less is known about its role in normal tissue homeostasis. We have explored this pathway during the different transitions of the human epidermal differentiation programme and after isolating stem cells, transit amplifying cells or differentiating cells from epidermis. Maximum expression of p53 was found in proliferating keratinocytes. A striking and transient induction of MDM2 and a down-modulation of p53 characterized the transition from proliferation to differentiation in primary human keratinocytes. These changes were delayed in late differentiating carcinoma cells, and were clearly different in suspended primary fibroblasts. Interestingly, these changes correlated with an increase in cell size, at the time of irreversible commitment to differentiation. Induction of MDM2 was also associated with suppression of proliferation in normal, or hyperproliferative, psoriatic epidermis. Moreover, both proteins were induced as keratinocytes were driven to leave the stem cell compartment by c-Myc activation. Overall, our results show a critical regulation of the p53/MDM2 pathway at the epidermal transition from proliferation to differentiation.

Normal and c-Myc-promoted human keratinocyte differentiation both occur via a novel cell cycle involving cellular growth and endoreplication

The relationship between cell cycle and differentiation in human keratinocytes is poorly understood. It is believed that keratinocytes suppress DNA replication and cell cycle arrest in G0 before they initiate terminal differentiation. However, a temporal separation between both events has not been established. Moreover, c-Myc promotes keratinocyte differentiation without causing cell cycle arrest. To address these paradoxes we have analysed cell cycle control during normal and c-Myc-promoted differentiation. Continuous activation of c-Myc or initiation of terminal differentiation results in a block of G2/M, cellular growth, endoreplication and polyploidy. Keratinocytes abandon G1, continue replicating DNA as they differentiate terminally and become polyploid. In fact, simply blocking mitosis with nocodazole resulted in increased cell size, terminal differentiation and endoreplication. This indicates that terminal differentiation associates with defective cell cycle progression and provides a novel insight into c-Myc biology.

Epidermal differentiation, apoptosis, and senescence: common pathways?

Regulation and execution of epidermal terminal differentiation, apoptosis and cellular senescence share some molecular and cellular features. The three phenomena result in suppression of proliferation and in some instances they seem to overlap. The boundaries between keratinocyte terminal differentiation and senescence are unclear and the former has been proposed to be a form of apoptosis. However, cumulative evidence argues that they are alternative, independent responses to different stimuli. I summarize in this review classical and recent evidence underlying the molecular control of these biological processes and propose a rationale to understand their nature and function in epidermis.

Leukemia, lymphomas, and myeloma mortality in the vicinity of nuclear power plants and nuclear fuel facilities in Spain

Mortality due to hematological tumors in towns near Spain's seven nuclear power plants and five nuclear fuel facilities during the period 1975-1993 was ascertained. The study was based on 610 leukemia-, 198 lymphoma-, and 122 myeloma-induced deaths in 489 towns situated within a 30-km radius of such installations. As control areas, we used 477 towns lying within a 50- to 100-km radius of each installation, matched by population size and a series of sociodemographic characteristics (income level, proportion of active population engaged in farming, proportion of unemployed, percentage of illiteracy, and province). Relative risk (RR) for each area and the trends in risk with increasing proximity to an installation were analyzed using log-linear models. None of the nuclear power plants registered an excess risk of leukemia-induced mortality in any of the surrounding areas. Excess risk of leukemia mortality was, however, observed in the vicinity of the uranium-processing facilities in Andújar [RR, 1.30; 95% confidence interval, 1.03-1.64] and Ciudad Rodrigo (RR, 1.68; 95% confidence interval, 0.92-3.08). Excess risk of multiplemyeloma mortality was found in the area surrounding the Zorita nuclear power plant. Statistical testing revealed that, with the single exception of multiple myeloma, none of the tumors studied showed evidence of a rise in risk with proximity to an installation. No study area yielded evidence of a raised risk of leukemia mortality among persons under the age of 25 years. More specific studies are called for in areas near installations that have been fully operational for longer periods. In this connection, stress should be laid on the importance of using dosimetric information in all future studies.

[Air pollutants and their monitoring]

Some basic concepts regarding air pollution are set out. Although, from a health care standpoint, our interest revolves around the impact which pollution has on human health, it being important to ascertain the main pollutants, the sources of emissions, the physiochemical properties thereof, the sampling and analysis methods which are used at the air pollution control stations, the limits set by the laws currently in impact and the World Health Organization recommendations with regard to the levels of immission. This study reviews these concepts with regard to the pollutants which have been analyzed in the Spanish Multicenter Study of Air Pollution and Mortality (EMECAM): particles, sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3). For this purpose, the most recent publications on this subject have been used, including part of what is going to be the line around which all of the measures aimed at combating air pollution are going to be revolving in the very near future, that is, the new set of European Union Directives (some currently in the proposal stage) and the latest recommendations (not as yet published) of the World Health Organization. Lastly, a wide range of aspects are set out which involve Public Health in the field of air pollution, despite the monitoring and control thereof falling to the environmental affairs authorities in terms of government organization.

Evidence that apoptosis and terminal differentiation of epidermal keratinocytes are distinct processes

Although there are clear parallels between apoptosis and epidermal terminal differentiation it is unclear whether terminal differentiation of keratinocytes is a form of apoptosis. We found that apoptosis was rare in adherent cultures of normal keratinocytes, even when growth factors were removed. When keratinocytes were placed in suspension for 24-96 h the majority of cells were induced to undergo terminal differentiation, as assessed by involucrin expression and cornified envelope assembly, but few cells underwent apoptosis, as assessed by morphological examination, TUNEL labelling and by DNA laddering. Withdrawal of serum and growth factors stimulated apoptosis of suspended keratinocytes but led to some reduction in the number of cells that underwent terminal differentiation. At 96 h the majority of cells retained their nuclei in the presence or absence of serum and growth factors. In normal epidermis only occasional cells within the granular layer had apoptotic nuclei, determined by TUNEL labelling and light and electron microscopy. In affected epidermis of psoriasis, Darier's disease and pityriasis rubra pilaris, diseases characterized by perturbation of growth, differentiation or adhesion, light microscopy revealed no higher proportion of apoptotic nuclei than in normal epidermis. However, the majority of viable epidermal layers in diseased skin were positive by TUNEL labelling, suggesting that TUNEL is not always a specific marker of apoptosis in keratinocytes. We conclude that in vivo and in culture keratinocyte terminal differentiation and apoptosis are distinct cellular events, subject to different stimuli.

c-Myc promotes differentiation of human epidermal stem cells

The epidermis contains two types of proliferative keratinocyte: stem cells, with unlimited self-renewal capacity, and transit amplifying cells, those daughters of stem cells that are destined to withdraw from the cell cycle and terminally differentiate after a few rounds of division. In a search for factors that regulate exit from the stem cell compartment, we constitutively expressed c-Myc in primary human keratinocytes by use of wild-type and steroid-activatable constructs. In contrast to its role in other cell types, activation of c-Myc in keratinocytes caused a progressive reduction in growth rate, without inducing apoptosis, and a marked stimulation of terminal differentiation. Keratinocytes can be enriched for stem or transit amplifying cells on the basis of beta1 integrin expression and by use of this method to fractionate cells prior to c-Myc activation, we found that c-Myc acted selectively on stem cells, driving them into the transit amplifying compartment. As a result, activation of c-Myc in epidermis reconstituted on a dermal equivalent led to premature execution of the differentiation program. The transcriptional regulatory domain of c-Myc was required for these effects because a deletion within that domain acted as a dominant-negative mutation. Our results reveal a novel biological role for c-Myc and provide new insights into the mechanism regulating epidermal stem cell fate.

Induction of PA2.26, a cell-surface antigen expressed by active fibroblasts, in mouse epidermal keratinocytes during carcinogenesis

The monoclonal antibody PA2.26, produced against mouse epidermal keratinocytes transformed with 7,12-dimethylbenz[a]anthracene (DMBA), recognizes a 43- to 47-kDa cell-surface protein that was absent from non-tumorigenic epidermal keratinocytes but present in transformed epidermal cell lines as well as cultured normal fibroblasts. In vivo, the antigen was absent from normal epidermis but induced in basal-like epidermal keratinocytes and dermal fibroblasts during tissue regeneration after wounding and treatment with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). The PA2.26 protein was also expressed in basal-like cells of differentiated papillomas and carcinomas generated in mice treated with DMBA and TPA. In addition, the antigen was abundantly synthesized by stromal cells of the tumors. These results suggest that PA2.26 antigen is involved in reactive processes during skin remodeling and carcinogenesis.

Changes in expression of members of the fos and jun families and myc network during terminal differentiation of human keratinocytes

Normal human epidermal keratinocytes are induced to undergo terminal differentiation when disaggregated and placed in suspension: commitment occurs at about 5 h and overt differentiation by 24 h. In contrast, the squamous cell carcinoma line SCC12B2 does not initiate terminal differentiation until 75 h in suspension and the ndk strain of keratinocytes undergoes growth arrest but does not differentiate at all. In order to identify genes that may regulate terminal differentiation we have examined mRNA levels of members of the fos and jun gene families and myc gene network in suspension cultures of normal keratinocytes, SCC12B2 and ndk. The major changes observed were an up-regulation of c-Fos and Fra-1 and a decrease in c-Myc at the time of commitment, followed by an increase in Mad, Mxi1, Fra-2 and JunB expression at the onset of differentiation. The sequence of events shows a striking similarity to that which occurs during myeloid differentiation and suggests a role for AP-1 complexes and Myc and Mad complexes in regulating keratinocyte differentiation.

Regulation of cell surface beta 1 integrin levels during keratinocyte terminal differentiation

Integrins of the beta 1 family play a central role in controlling adhesion and terminal differentiation within the epidermis. When human epidermal keratinocytes undergo terminal differentiation, intracellular transport of newly synthesized integrins is inhibited, and mature receptors are lost from the cell surface. We have examined the mechanisms underlying these processes, using an experimental model in which keratinocytes are placed in suspension to induce terminal differentiation. The block in intracellular transport was keratinocyte- and integrin-specific since it was not observed when fibroblasts were placed in suspension and did not affect E-cadherin synthesis in suspended keratinocytes. Newly synthesized beta 1 integrins associated with an endoplasmic reticulum resident protein, calnexin; the association was prolonged when keratinocytes were placed in suspension, suggesting a role for calnexin in the inhibition of transport. After 24 h, the level of beta 1 integrin mRNA declines in suspended keratinocytes, reflecting inhibition of gene transcription, but in fibroblasts, the level remained constant. Transport of integrins could be blocked in both adherent keratinocytes and fibroblasts by inhibiting total protein synthesis, raising the possibility that transport is coupled to de novo integrin synthesis. The fate of receptors on the surface of keratinocytes was followed by confocal immunofluorescence microscopy, immunoelectron microscopy, and biochemical analysis: with the onset of terminal differentiation, endocytosed receptors were transported to the lysosomes. These experiments reveal novel mechanisms by which integrin levels can be controlled. Together with our earlier evidence for transcriptional regulation and affinity modulation of integrins, they highlight the complexity of the mechanisms which ensure that the onset of terminal differentiation is linked to detachment of keratinocytes from the underlying basement membrane.

Expression of intermediate filament proteins by normal and transformed mouse epidermal-keratinocytes in culture

The aberrant expression of embryonic simple epithelial keratins K8 and K18 has been previously detected in chemically-induced mouse skin carcinomas and in cultured epidermal keratinocytes containing H-ras oncogenes. In this study, we report that cell lines derived from benign papillomas do not generally synthesize simple epithelial keratins, regardless of the presence of H-ras gene alterations. These results reinforce our previous suggestion that the expression of these keratins during mouse epidermal carcinogenesis is a marker of malignant transformation. The comparison of the two-dimensional electrophoresis intermediate filament protein profiles of transformed keratinocytes in culture, reveal that during in vitro progression to the malignant phenotype increased synthesis of simple epithelial keratins is associated to a general disturbance on the expression of cytoskeletal proteins.

Changes in keratin expression during malignant progression of transformed mouse epidermal keratinocytes

We have studied in this report the expression of keratins in mouse epidermal keratinocytes transformed in culture by a chemical carcinogen (PDV) and in cell lines (PDVCM1, PDVCM2, PDVCV1, and PDVC57) derived by tumor transplantation of PDV cells in syngeneic C57Bl/6 mice. PDV, PDVCM1, PDVCM2, and PDVCV1 cell lines are weakly to moderately tumorigenic, giving rise to squamous cell carcinomas, although not at all injection points, whereas PDVC57 cells are more malignant, inducing highly anaplastic carcinomas at 100% of injection sites. All the cell lines synthesize anomalously simple epithelial keratins, substantial amounts of K8, and minor quantities of K18 and K19, but the level of expression is increased in PDVC57. We have found that in PDVC57 cells upregulation of K8 is linked to down-regulation of the normal keratins produced by epidermal keratinocytes in culture (i.e., K5, K6, K14, and K17). On the other hand, K8 does not generally colocalize with K13, a keratin also aberrantly expressed by epidermal cell cultures when induced to differentiate by high Ca2+ medium. K13, normally synthesized in internal stratified epithelia, is anomalously induced in mouse epidermal tumors and has been used as an early marker of carcinoma progression. In tumors induced by the cell lines upon injection in mice, K8 is found in the less differentiated regions as opposite to K13, restricted to the differentiating areas of the tumors. In PDV, PDVCM1, PDVCM2, and PDVCV1 carcinomas the overall expression of K13 is higher than that of K8. However, this relation is inverted in tumors induced by PDVC57 cells, in a good correlation with the tumoral phenotypes produced by the cell lines. Our results suggest that upregulation of the simple epithelial keratin K8, as found in transformed epidermal cell lines and tumors, is a late marker of malignant progression and is associated with the loss of the differentiated phenotype.

Biochemical characterization of Artemia ras p21

The biochemical properties of Artemia ras proteins (p21) have been studied after immunoprecipitation with the monoclonal antibody Y13-259. The ras products bind GTP and GDP, and have GTPase activity. Artemia p21 was unable to hydrolyze Gp4G, although this dinucleotide exhibits high affinity for the protein. Our results demonstrate that the protein(s) recognized by the Y13-259 antibody in this crustacean behave as typical mammalian ras p21s.