Post-traumatic stress disorder and drug use disorder: examination of aetiological models in a Swedish population-based cohort

Background: There are two primary phenotypic models of comorbidity between post-traumatic stress disorder (PTSD) and drug use disorder (DUD), i.e. self-medication (PTSD precedes and causes DUD) and susceptibility (DUD precedes and causes PTSD). We sought to clarify the longitudinal relationship between PTSD and DUD, while examining sex differences.Method: We used approximately 23 years of longitudinal data from Swedish population registries to conduct two complementary statistical models: Cox proportional hazard models (N ≈ 1.5 million) and a cross-lagged panel model (N ≈ 3.8 million).Results: Cox proportional hazards models, adjusting for cohort and socioeconomic status, found strong evidence for the self-medication hypothesis, as PTSD predicted increased risk for DUD among both women [hazard ratio (HR) = 5.34, 95% confidence interval (CI) 5.18, 5.51] and men (HR = 3.65, 95% CI 3.54, 3.77), and moreover, that the PTSD to DUD association was significantly higher among women (interaction term 0.68, 95% CI 0.65, 0.71). The results of the susceptibility model were significant, but not as strong as the self-medication model. DUD predicted risk for PTSD among both women (HR = 2.43, 95% CI 2.38, 2.50) and men (HR = 2.55, 95% CI 2.50, 2.60), and HR was significantly higher in men (interaction term 1.05, 95% CI 1.02, 1.08). Investigating the pathways simultaneously in the cross-lagged model yielded support for both pathways of risk. The cross-paths instantiating the susceptibility model (0.10-0.22 in females, 0.12-0.19 in males) were mostly larger than those capturing the self-medication model (0.01-0.16 in females, 0.04-0.22 in males).Conclusions: We demonstrate that the relationship between PTSD and DUD is bidirectional, with evidence that future research should prioritize examining specific pathways of risk that may differ between men and women.

All-cause and cardiovascular mortality risk after surgery versus radioiodine treatment for hyperthyroidism

Background

Little is known about the long-term side-effects of different treatments for hyperthyroidism. The few studies previously published on the subject either included only women or focused mainly on cancer outcomes. This register study compared the impact of surgery versus radioiodine on all-cause and cause-specific mortality in a cohort of men and women.

Methods

Healthcare registers were used to find hyperthyroid patients over 35 years of age who were treated with radioiodine or surgery between 1976 and 2000. Comparisons between treatments were made to assess all-cause and cause-specific deaths to 2013. Three different statistical methods were applied: Cox regression, propensity score matching and inverse probability weighting.

Results

Of the 10 992 patients included, 10 250 had been treated with radioiodine (mean age 65·1 years; 8668 women, 84·6 per cent) and 742 had been treated surgically (mean age 44·1 years; 633 women, 85·3 per cent). Mean duration of follow-up varied between 16·3 and 22·3 years, depending on the statistical method used. All-cause mortality was significantly lower among surgically treated patients, with a hazard ratio of 0·82 in the regression analysis, 0·80 in propensity score matching and 0·85 in inverse probability weighting. This was due mainly to lower cardiovascular mortality in the surgical group. Men in particular seemed to benefit from surgery compared with radioiodine treatment.

Conclusion

Compared with treatment with radioiodine, surgery for hyperthyroidism is associated with a lower risk of all-cause and cardiovascular mortality in the long term. This finding was more evident among men.

Evaluation of prevalent and incident ovarian cancer co-morbidity

BACKGROUND

The peak in incidence of ovarian cancer occurs around 65 years and concurrent increasing risk by age for a number of diseases strongly influence treatment and prognosis. The aim was to explore prevalence and incidence of co-morbidity in ovarian cancer patients compared with the general population.

METHODS

The study population was patients with ovarian cancer in Sweden 1993-2006 (n=11 139) and five controls per case (n=55 687). Co-morbidity from 1987 to 2006 was obtained from the Swedish Patient Register. Prevalent data were analysed with logistic regression and incident data with Cox proportional hazards models.

RESULTS

Women developing ovarian cancer did not have higher overall morbidity than other women earlier than 3 months preceding cancer diagnosis. However, at time of diagnosis 11 of 13 prevalent diagnosis groups were more common among ovarian cancer patients compared with controls. The incidence of many common diagnoses was increased several years following the ovarian cancer and the most common diagnoses during the follow-up period were thromboembolism, haematologic and gastrointestinal complications.

CONCLUSION

Women developing ovarian cancer do not have higher overall morbidity the years preceding cancer diagnosis. The incidence of many common diagnoses was increased several years following the ovarian cancer. It is crucial to consider time between co-morbidity and cancer diagnosis to understand and interpret associations.

Determinants of mobile phone output power in a multinational study: implications for exposure assessment

OBJECTIVES

The output power of a mobile phone is directly related to its radiofrequency (RF) electromagnetic field strength, and may theoretically vary substantially in different networks and phone use circumstances due to power control technologies. To improve indices of RF exposure for epidemiological studies, we assessed determinants of mobile phone output power in a multinational study.

METHODS

More than 500 volunteers in 12 countries used Global System for Mobile communications software-modified phones (GSM SMPs) for approximately 1 month each. The SMPs recorded date, time, and duration of each call, and the frequency band and output power at fixed sampling intervals throughout each call. Questionnaires provided information on the typical circumstances of an individual's phone use. Linear regression models were used to analyse the influence of possible explanatory variables on the average output power and the percentage call time at maximum power for each call.

RESULTS

Measurements of over 60,000 phone calls showed that the average output power was approximately 50% of the maximum, and that output power varied by a factor of up to 2 to 3 between study centres and network operators. Maximum power was used during a considerable proportion of call time (39% on average). Output power decreased with increasing call duration, but showed little variation in relation to reported frequency of use while in a moving vehicle or inside buildings. Higher output powers for rural compared with urban use of the SMP were observed principally in Sweden where the study covered very sparsely populated areas.

CONCLUSIONS

Average power levels are substantially higher than the minimum levels theoretically achievable in GSM networks. Exposure indices could be improved by accounting for average power levels of different telecommunications systems. There appears to be little value in gathering information on circumstances of phone use other than use in very sparsely populated regions.

Medical history, cigarette smoking and risk of acoustic neuroma: an international case-control study

Acoustic neuroma (vestibular schwannoma) is a benign tumor of the vestibulocochlear nerve. Its recorded incidence is increasing but risk factors for this tumor have scarcely been investigated. We conducted a population-based case-control study of risk factors for acoustic neuroma in the UK and Nordic countries, including 563 cases and 2,703 controls. Tumor risk was analyzed in relation to medical history and cigarette smoking. Risk of acoustic neuroma was significantly raised in parous compared with nulliparous women (OR = 1.7, 95% CI: 1.1-2.6), but was not related to age at first birth or number of children. Risk was not associated with a history of allergic disease, past head injury, past diagnosis of a neoplasm or birth characteristics, but was significantly raised for past diagnosis of epilepsy (OR = 2.5, 95% CI: 1.3-4.9). Tumor risk was significantly reduced in subjects who had ever regularly smoked cigarettes (OR = 0.7, 95% CI: 0.6-0.9), but the reduction applied only to current smokers (OR = 0.5, 95% CI: 0.4-0.6), not ex-smokers (OR = 1.0, 95% CI: 0.8-1.3). The reduced risk of acoustic neuroma in smokers and raised risk in parous women might relate to sex hormone levels, or smoking might suppress tumor growth, but effects of parity and smoking on timing of diagnosis of the tumor are also a potential explanation. The raised risk in relation to past diagnosis of epilepsy might be a surveillance artefact or imply that epilepsy and/or antiepileptic medication use predispose to acoustic neuroma. These findings need replication by other studies and possible mechanisms need to be clarified.

Validation of short term recall of mobile phone use for the Interphone study

AIM

To validate short term recall of mobile phone use within Interphone, an international collaborative case control study of tumours of the brain, acoustic nerve, and salivary glands related to mobile telephone use.

METHODS

Mobile phone use of 672 volunteers in 11 countries was recorded by operators or through the use of software modified phones, and compared to use recalled six months later using the Interphone study questionnaire. Agreement between recalled and actual phone use was analysed using both categorical and continuous measures of number and duration of phone calls.

RESULTS

Correlations between recalled and actual phone use were moderate to high (ranging from 0.5 to 0.8 across countries) and of the same order for number and duration of calls. The kappa statistic demonstrated fair to moderate agreement for both number and duration of calls (weighted kappa ranging from 0.20 to 0.60 across countries). On average, subjects underestimated the number of calls per month (geometric mean ratio of recalled to actual = 0.92, 95% CI 0.85 to 0.99), whereas duration of calls was overestimated (geometric mean ratio = 1.42, 95% CI 1.29 to 1.56). The ratio of recalled to actual use increased with level of use, showing underestimation in light users and overestimation in heavy users. There was substantial heterogeneity in this ratio between countries. Inter-individual variation was also large, and increased with level of use.

CONCLUSIONS

Volunteer subjects recalled their recent phone use with moderate systematic error and substantial random error. This large random error can be expected to reduce the power of the Interphone study to detect an increase in risk of brain, acoustic nerve, and parotid gland tumours with increasing mobile phone use, if one exists.

Mobile phone use and risk of acoustic neuroma: results of the Interphone case-control study in five North European countries

There is public concern that use of mobile phones could increase the risk of brain tumours. If such an effect exists, acoustic neuroma would be of particular concern because of the proximity of the acoustic nerve to the handset. We conducted, to a shared protocol, six population-based case-control studies in four Nordic countries and the UK to assess the risk of acoustic neuroma in relation to mobile phone use. Data were collected by personal interview from 678 cases of acoustic neuroma and 3553 controls. The risk of acoustic neuroma in relation to regular mobile phone use in the pooled data set was not raised (odds ratio (OR) = 0.9, 95% confidence interval (CI): 0.7-1.1). There was no association of risk with duration of use, lifetime cumulative hours of use or number of calls, for phone use overall or for analogue or digital phones separately. Risk of a tumour on the same side of the head as reported phone use was raised for use for 10 years or longer (OR = 1.8, 95% CI: 1.1-3.1). The study suggests that there is no substantial risk of acoustic neuroma in the first decade after starting mobile phone use. However, an increase in risk after longer term use or after a longer lag period could not be ruled out.

Output power levels from mobile phones in different geographical areas; implications for exposure assessment

BACKGROUND

The power level used by the mobile phone is one of the most important factors determining the intensity of the radiofrequency exposure during a call. Mobile phone calls made in areas where base stations are densely situated (normally urban areas) should theoretically on average use lower output power levels than mobile phone calls made in areas with larger distances between base stations (rural areas).

AIMS

To analyse the distribution of power levels from mobile phones in four geographical areas with different population densities.

METHODS

The output power for all mobile phone calls managed by the GSM operator Telia Mobile was recorded during one week in four defined areas (rural, small urban, suburban, and city area) in Sweden. The recording included output power for the 900 MHz and the 1800 MHz frequency band.

RESULTS

In the rural area, the highest power level was used about 50% of the time, while the lowest power was used only 3% of the time. The corresponding numbers for the city area were approximately 25% and 22%. The output power distribution in all defined urban areas was similar.

CONCLUSION

In rural areas where base stations are sparse, the output power level used by mobile phones are on average considerably higher than in more densely populated areas. A quantitative assessment of individual exposure to radiofrequency fields is important for epidemiological studies of possible health effects for many reasons. Degree of urbanisation may be an important parameter to consider in the assessment of radiofrequency exposure from mobile phone use.

Functional polymorphism in the alcohol dehydrogenase 3 (ADH3) promoter

The ADH3 gene encodes alcohol dehydrogenase 3 (ADH3)/glutathione-dependent formaldehyde dehydrogenase, the ancestral and most conserved form of alcohol dehydrogenase. ADH3 is expressed in all tissues examined and the enzyme is essential for formaldehyde scavenging. We have screened the promoter region including exon 1 and exons 5, 6 and 7 of the ADH3 gene for allelic variants. Using 80 samples of genomic DNA from Swedes as template, the various parts of the gene were PCR amplified and subsequently analyzed on single strand conformation polymorphism (SSCP) gels. No abnormal migration patterns could be detected by SSCP analysis of exons 5, 6 and 7 while for the promoter region, a large number of the samples displayed differences in SSCP gel migration patterns. Cloning and sequence analysis revealed four possible base pair exchanges in the promoter region. Two transitions were found at position -197 and -196, GG --> AA, one at position -79, G --> A and finally, close to the transcription start site, a fourth transition was found at position +9, C --> T. An allele specific PCR method was developed and allele frequencies were determined in three populations: Chinese, Spanish and Swedish. GG-197,-196 and AA-197,-196 alleles were common in all three populations, G-79 and A-79 were common in Swedes and Spaniards but only A-79 was found among Chinese. T+9 was the most rare allele with an allele frequency of 1.5% in Swedes. Finally, promoter activity assessments and electrophoretic mobility shift assays demonstrated that the C+9 --> T+9 exchange resulted in a significant transcriptional decrease in HeLa cells and a decreased binding of nuclear proteins. These base pair exchanges may have an effect on the expression of the enzyme and thereby influence the capacity of certain individuals to metabolize formaldehyde.

C-erb-b2/int-2 amplification appears faster in breast-cancer patients receiving second-line endocrine treatment

We have examined the appearance of c-erb-b2 and int-2 amplification in 2 different groups of breast-cancer patients. The groups differed with regard to their clinical status in that one group was receiving first-line endocrine treatment (tamoxifen) whereas the second was receiving second-line endocrine treatment (after failing on tamoxifen). The latter group of patients showed clinicallya a more advanced disease (higher frequency of stage-IV as compared to stage-III disease). Consecutive tumor samples were obtained using fine-needle biopsies from individual tumor lesions of each patient every second or third month. Median time from diagnosis to the last biopsy for patients receiving tamoxifen was 25 months and, for patients receiving second-line treatment, 55 months. The presence of amplification was determined using semi-quantificative PCR. We found that both genes developed amplification during tumor progression. The appearance of amplification was more pronounced in the clinically more advanced patients receiving second-line treatment (p = 0.018).

Prognostic significance of c-erb-B2 amplification in fine-needle biopsies of breast cancer patients not operated at diagnosis

Prognostication of breast cancer patients, not operated at diagnosis, poses a clinically difficult problem. To use gene amplification we examined cytological samples and determined c-erb-B2 gene copy number with semi-quantitative PCR. Control experiments showed the same gene-copy number in aliquots that were either air-dried (and MGG-stained), fixed in methanol (and air-dried), or snap-frozen in liquid nitrogen. Therefore we examined the prognostic value of c-erb-B2 amplification in 95 breast cancer patients that had not been operated at diagnosis (up to 12 years previously). Tumor cells were obtained from routine archival cytological smears. 15 patients (16%) had developed amplification. Univariate and multivariate analysis showed that c-erb-B2 amplification is a significant prognostic factor (p < 0.0001). Hence routine cytological MGG smears can be used for prognostic determination.

Higher frequency of gene amplification in breast cancer patients who received adjuvant chemotherapy

BACKGROUND

Amplification of certain genes is involved in resistance to chemotherapy. The development of such amplification in patients by drug treatment has not yet been established. We have assessed the appearance of gene amplification in breast cancer patients with recurrent disease. One group of patients had previously received adjuvant chemotherapy (cyclophosphamide, methotrexate, 5-fluorouracil [CMF]) after surgery. The second group had not. All of these patients had developed recurrent disease and were receiving first-line endocrine treatment (tamoxifen).

METHODS

Tumor cells were obtained from the recurrent carcinoma using fine-needle biopsies. Gene copy number was determined for dihydrofolate reductase and thymidylate synthase with semiquantitative polymerase chain reaction. Dihydrofolate reductase is involved in resistance to methotrexate (M) and thymidylate synthetase in resistance to 5-fluoropyrimidines (F), two targets for the CMF regime.

RESULTS

We found that amplification of the examined genes develops in higher frequency among patients who previously received chemotherapy (p = 0.002).

CONCLUSIONS

These findings provide strong evidence for gene amplification induced by drug treatment.

Prognostic value of amplification of c-erb-B2 in bladder carcinoma

Amplification of c-erb-B2 is examined in patients with transitional cell bladder carcinoma. In a pilot study we found that the amplification correlated with high tumor grade. Tumor grade is a known prognostic factor. Therefore, we next examined the prognostic value of c-erb-B2 amplification in patients with >16 years of clinical follow-up. The gene copy number was determined, using semiquantitative PCR, in archival formalin-fixed tissues. Twenty-three percent (37/163 patients) showed the amplification. The amplification correlated with grade and stage. Moreover, we found that tumor grade (P < 0.001) and c-erb-B2 amplification (P < 0.001) showed prognostic information for survival. Patients with grade 3 tumors and concomitant c-erb-B2 amplification showed the worst prognosis. Multivariate analysis indicates that grade and c-erb-B2 amplification are independent prognostic factors.

Prognostic value of erb-B2 and myc amplification in breast cancer imprints

BACKGROUND

Amplification of erb-B2 and myc shows prognostic value in patients with operable breast cancer. Amplification is usually detected in tumor samples remaining after pathologic work-up, preventing the examination of small tumors.

METHODS

Tumor imprints that contained low numbers of contaminating normal cells were obtained from small tumors. The prognostic value of erb-B2 and myc amplification in imprint breast preparations was examined, using the polymerase chain reaction (PCR) to determine gene copy number. Tumor material was obtained from 162 patients with breast cancer operated 1975-1976.

RESULTS

Amplification of erb-B2 existed in 21% and myc in 16% of the patients. Both erb-B2 and myc amplification showed prognostic significance in univariate analysis for survival and relapse free survival. In multivariate analysis, erb-B2 was a significant factor. In small tumors less than 13 mm in greatest dimension, erb-B2 showed prognostic significance for survival but not for relapse free survival.

CONCLUSIONS

The use of imprints/PCR allows the detection of gene amplification in breast cancer. The procedure is suitable for the analysis of small tumors and can be used to examine very small tumors, such as those detected mammographically.

Intratumoral heterogeneity for amplified genes in human breast carcinoma

Intratumoral heterogeneity was studied in human breast cancer by examining separate tumor lesions of individual patients. Tumor samples were obtained from each patient by fine-needle biopsies from 2 to 4 separate tumor lesions. We used a semi-quantitative PCR to distinguish between samples with gene amplification and single gene copy samples. Five genes were analyzed in each biopsy: MDR-1, dihydrofolate reductase, thymidylate synthase, c-erb-B2 and int-2. Three groups of patients were examined: those awaiting initiation of treatment; those receiving first-line endocrine therapy; and those receiving second-line endocrine treatment. A pattern of intratumoral heterogeneity for gene amplification was clearly apparent. The frequency of amplification was lowest before initiating therapy and highest in patients receiving second-line treatment (p = 0.023).

Reduced formation of high molecular weight DNA in murine gliomas treated with nitrosourea and chlorpromazine

We have examined the formation of DNA in rat glioma cells. Cytotoxicity was induced in the cells using BCNU (1,3-bis(2-chloroethyl)-1-nitroso-urea) in the presence or absence of CPZ (chlorpromazine). There was impaired formation of DNA in cells treated with BCNU. This was further enhanced in cells treated with both BCNU and CPZ. In the latter case we did not find any intact high molecular weight DNA.

Breast cancer: prognostic significance of c-erb-B2 and int-2 amplification compared with DNA ploidy, S-phase fraction, and conventional clinicopathological features

The prognostic value of oncogene amplification and conventional clinicopathological features was determined in consecutive breast cancers detected during 5 months in 1975-1976 in 4 Swedish counties. Material was collected from 162 of the 179 patients and tumor size, nodal status, FSH, estrogen/progesterone receptor status, DNA ploidy and S-phase fraction determined. Tissues remaining from 80 patients were stored frozen until 1991, when amplification of the oncogenes c-erb-B2 and int-2 was determined. We show that c-erb-B2 amplification (but not int-2 amplification) and positive axillary nodal status show prognostic significance for both survival and relapse-free survival in univariate and multivariate analysis. The other examined factors showed no significance.

Demonstration of gene-amplification by PCR in archival paraffin-embedded breast cancer tissue

The polymerase chain reaction (PCR) is a powerful tool to examine genetic alterations in tumor samples. We describe a simple, rapid, nonisotopic PCR method to semi-quantitatively determine the number of gene copies in human formalin-fixed paraffin-embedded tissue. The procedure is exemplified by analysis of 15 years old breast cancer samples to determine the presence of amplification of c-erb-B2. The samples were obtained from routine specimens kept in pathological archives. Patients with amplified samples showed a poor prognosis, both for recurrences and death in breast cancer.

Gene amplification detected in carcinoma cells from human urinary bladder washings by the polymerase chain reaction method

BACKGROUND

Urinary bladder carcinoma often is diagnosed from malignant cells in bladder washings obtained at cystoscopic examination. In some cases, there are difficulties distinguishing between cytologic Grades 1 and 2. Detection of genetic alterations in combination with morphologic analysis may facilitate the diagnosis.

METHODS

The presence of amplified c-erb-B2 and epidermal growth factor receptor (EGF-R) was examined in tumor cells present in bladder washings. The gene copy number was determined with the polymerase chain reaction (PCR).

RESULTS

The authors detected amplified c-erb-B2 and EGF-R in cancer cells of cytologic Grade 2 and 3 tumors. They did not detect amplification in cytologic Grade 1 tumor cells or in cells from bladders, without known malignant neoplasms.

CONCLUSIONS

Examination of genetic alterations, in combination with morphologic analysis, facilitates the diagnosis of carcinoma.

Appearance of amplified thymidylate synthase or dihydrofolate reductase genes in stage-IV breast-cancer patients receiving endocrine treatment

We have examined the appearance of amplification of 2 genes involved in resistance to chemotherapy (thymidylate synthase, dihydrofolate reductase) in patients receiving endocrine treatment. Chronological tumor samples were obtained from breast-cancer patients with clinical stage-IV disease, using fine-needle biopsies. The presence of amplification of thymidylate synthase and dihydrofolate reductase was determined using PCR in 185 fine-needle biopsies from 37 patients. None of the initial samples of each patient showed amplification. However, in 7 of the 37 patients (19%) we detected development of gene amplification: in 2 cases of thymidylate synthase and in 5 cases of dihydrofolate reductase. Five of the 7 patients with amplification were receiving second-line endocrine treatment after failing to respond to tamoxifen.

Reduced occurrence of mdr-1 amplification in stage-IV breast-cancer patients treated with tamoxifen compared with other endocrine treatments

Amplification of mdr-1 occurs in breast cancer patients receiving endocrine treatment. We have compared a group of patients receiving tamoxifen and a group receiving second-line endocrine treatment after failure of tamoxifen treatment. Chronological tumor samples were obtained by fine-needle biopsies from the same tumor lesion of each patient and PCR was used to detect the appearance of gene amplification. Three of 20 patients receiving tamoxifen developed amplified mdr-1 whereas 7 of 17 patients receiving second-line endocrine treatment developed mdr-1 amplification.

Detection and temporal appearance of multiple copies of c-erb-B2 genes in advanced mammary carcinoma using fine needle biopsies and the polymerase chain reaction

Aspiration of tumor cells by the fine-needle biopsy method yields only a small number of cells, which hampers conventional molecular analysis for the presence of multiple copies of oncogenes. We have therefore adopted the polymerase chain reaction (PCR) method to study semi-quantitatively the level of the c-erb-B2 gene in human breast tumor samples. Of 39 patients with mammary carcinoma, 7 (19%) contained multiple copies of c-erb-B2 genes, whereas only two samples failed to give informative data. Next the multiple copies of c-erb-B2 genes, whereas only two samples failed to give informative data. Next the temporal appearance of multiple gene copies was examined in 20 patients with clinical stage IV disease. Tumor samples were obtained every second to third month from the same tumor lesion of each patient. None of the initial samples from each patient contained multiple copies of c-erb-B2. Of 16 patients that showed progressive clinical disease, 5 developed multiple gene copies, showing that the event occurs in clinical stage IV disease.

Appearance and detection of multiple copies of the mdr-1 gene in clinical samples of mammary carcinoma

To examine the presence of multiple copies of the mdr-I gene in clinical tumor samples we have developed an approach where the cells are obtained by fine-needle biopsies and the number of gene copies determined by PCR. The temporal appearance of amplified mdr-I was examined in 20 breast-cancer patients with clinical stage-IV disease receiving endocrine treatment. Tumor samples were obtained every 2nd to 3rd month from the same tumor lesion. None of the initial samples from each patient contained multiple copies of mdr-I. Of 16 patients who showed increased tumor size, 4 developed multiple gene copies, showing that the event occurs without cytotoxic selection of cells with chemotherapy.

Amplification of oncogenes in mammary carcinoma shown by fine-needle biopsy

A procedure that measures the amplification of oncogenes in human cancer cells is described. The cells were obtained by fine-needle biopsy to allow repeated sampling from individual metastases. A drawback was the low number of cells obtained, but this could be overcome by using a slot-blot hybridization technique to measure gene amplification. Two patients with mammary cancer (primary tumors or metastases), analyzed for the levels of amplification of the oncogene erb-B2, are described in detail. This technique is suitable for analyzing alterations occurring during cancer progression and for identifying subgroups of mammary cancer with different characteristics.

An abnormal profile of DNA replication intermediates in Bloom's syndrome

Bloom's syndrome (BS) cells display a characteristic genomic instability, notably an elevated frequency of sister-chromatid exchange. Replicating DNA in cultured BS cells was labeled with [3H]thymidine using several time schedules. Separation of DNA in agarose gels showed high molecular weight DNA and three classes of DNA replication intermediates: 20-kilobase DNA, 10-kilobase DNA, and Okazaki fragments. In contrast newly replicated DNA from normal cells showed no 20-kilobase DNA replication intermediates. Certain BS cells, exceptional in that their characteristic genomic instability has for unknown reasons been corrected, also differed from normal cells in having the 20-kilobase intermediate, but they differed from both normal cells and the other (the uncorrected) BS cells in lacking the 10-kilobase DNA replication intermediates.

Increased levels of 5-fluorouracil-induced DNA lesions in Bloom's syndrome

In Bloom's syndrome (BS) the regulation of uracil-DNA glycosylase, an enzyme involved in the repair of DNA containing 5-FU, is altered. 5-FU induces higher levels of DNA fragmentation in BS cells than in non-BS cells. The increase in DNA fragmentation is connected to the cytotoxic mechanism where 5-FU is incorporated into DNA. When 5-FU induces DNA fragmentation by a mechanism not involving the incorporation of drug into DNA, the levels of DNA fragmentation in BS and non-BS cells remain similar.

Bleomycin-induced DNA lesions are dependent on nucleosome repeat length

Treatment of cells or nuclei with bleomycin induces DNA lesions. We detect the presence of lesions as the release of fragments from bulk DNA when cells (or nuclei) are lysed in dilute alkali. To further characterize the lesions we have altered experimentally the average nucleosome repeat length and probed the lysate with nuclease S1 in order to remove single-stranded DNA. In salt-incubated nuclei with short average nucleosome repeat length (140-145 base pairs) (and also with long nucleosome-free stretches of DNA) one can induced fewer DNA lesions in the nucleosome-containing DNA as compared to nuclei with 190-195 base pairs average nucleosome repeat length. Hence the ability of bleomycin to induce DNA lesions is dependent on nucleosome repeat length.

Altered formation of DNA in human cells treated with inhibitors of DNA topoisomerase II (etoposide and teniposide)

We have investigated the importance of DNA topoisomerase II for the formation of mammalian DNA replication intermediates. Treatment with the DNA topoisomerase II inhibitor etoposide (teniposide) prevents the formation of large intermediates, such as 10-kilobase DNA, but allows the formation of small intermediates, i.e., Okazaki fragments. In untreated cells, there is a distinct stage in which the 10-kilobase DNA intermediates are joined before the appearance of mature chromatin. We find that pretreatment with etoposide (teniposide) prevents the appearance of this stage. When the protocol is reversed and the cells contain labeled 10-kilobase DNA before exposure to the drugs, one can detect the stage.

Appearance of a late stage during mammalian DNA replication when cells resume formation of 10 kb DNA replication intermediates

After the joining of human large DNA replication intermediates and before the appearance of mature chromatin DNA, there exists a distinct stage--'the post-elongation stage'. This stage reappears during recovery of DNA synthesis simultaneously with the reappearance of a large DNA replication intermediate, 10 kb DNA.

Altered formation of DNA replication intermediates in human 46 BR fibroblast cells hypersensitive to 3-aminobenzamide

The appearance of DNA replication intermediates was investigated in a human fibroblast strain (46 BR) which is hypersensitive to the lethal effects of 3-aminobenzamide. 3-Aminobenzamide is an inhibitor of poly(ADP-ribose) synthetase and modulates DNA ligase activity. We detected the same intermediates (10 kb DNA and Okazaki-fragments) as in normal fibroblasts, but kinetics and amounts of intermediates were altered, either as a result of, or in order to overcome the defect in the cells.

Reduced DNA damage induced in human melanoma cells by dacarbazine in the presence of deoxyribonucleosides

Decarbazine induces DNA lesions in replicating DNA. We show here that deoxyribonucleosides, with the exception of thymidine, in doses of 250 microM or higher, prevent dacarbazine-induced DNA lesions. The DNA lesions that appear in the presence of thymidine can be prevented by aphidicolin, an inhibitor of DNA synthesis. Cytotoxicity analyses confirm that the combination thymidine-dacarbazine prevents cell outgrowth only partially, while other deoxyribonucleosides completely abolish the dacarbazine effect.

5-Fluoropyrimidine-induced DNA damage in human colon adenocarcinoma and its augmentation by the nucleoside transport inhibitor dipyridamole

5-Fluorouracil and 5-fluorodeoxyuridine induce DNA lesions via two different mechanisms, one involving and the other not involving the incorporation of drug into DNA. The DNA lesions are detected by lysing cells in dilute alkali and then separating the DNA in agarose gel electrophoresis. We examine here the effect of dipyridamole, a nucleoside transport inhibitor, on the DNA lesions. We find that dipyridamole augments the levels of DNA fragmentation when the lesions are induced by the mechanism not involving the incorporation of drug. In parallel cytotoxicity is increased.

Altered formation of DNA replication intermediates in cells growing in different culture conditions

In human melanoma cells one can detect two discrete DNA replication intermediates, 10-kb DNA intermediates and Okakzaki fragments. Both intermediates are seen when cells are rapidly growing in medium supplemented with fetal calf serum. When the medium is supplemented with newborn calf serum, one can detect Okakzaki fragments but not 10-kb DNA intermediates. In contrast we do not detect changes in the replicon sizes in the two media.

Step-wise progression of mammalian 10-kb DNA replication intermediates to mature chromatin

In mammalian DNA synthesis the primary replication intermediates are joined to larger intermediates. After the joining process is complete one can detect a distinct stage called the post-elongation stage. Furthermore a 10-kb DNA1 population is detected before the post-elongation stage whereas a 10-kb DNA2 population is part of this stage DNA. When cells are treated with 3-aminobenzamide, an inhibitor of poly(ADP-ribose) synthetase, an altered post-elongation-stage DNA was detected, which does not contain 10-kb fragments. The step(s) affected by 3-aminobenzamide prevents the appearance of 10-kb DNA in the post-elongation stage. The drug effect is reversible with the appearance of 10-kb DNA in the post-elongation stage when the cells are washed free of drug. Hence there is a step-wise progression from 10-kb DNA, via the post-elongation stage, to mature chromatin.

Cytotoxicity, calmodulin and DNA lesions in cells treated with streptozotocin

Streptozotocin is a nitrosourea-derivative containing a methyl group instead of a haloethyl group. Treatment of human adenocarcinoma cells with streptozotocin induces DNA lesions. The presence of the lesions is visualized during cell lysis in dilute alkali as changes in fragmentation of prelabelled DNA. The increase in DNA fragmentation is paralleled by increased cytotoxicity. Furthermore prolonged duration of treatment reduces the level of DNA fragmentation. The repair of the DNA lesions is prevented by treating the cells with W-7, an inhibitor of calmodulin.

Increased levels of DNA lesions induced by leucovorin-5-fluoropyrimidine in human colon adenocarcinoma

Leucovorin augments the growth inhibitory effect of 5-fluoropyrimidines on neoplastic cells. The effect is paralleled by much higher levels of DNA fragmentation than in cells treated with 5-fluoropyrimidines alone at the same concentration. The lesions are induced by a mechanism independent of incorporation of the drug into DNA, in all probability due to reduced repair of DNA lesions induced independently of the drug treatment. Thymidine added after the treatment with fluoropyrimidines partly rescues the cells and reduces the level of DNA fragmentation.

Progressive formation of DNA lesions during treatment with anti-metabolites without incorporation of the drugs into DNA

Anti-metabolites, such as methotrexate, 5-fluoropyrimidines or hydroxyurea, induce progressive formation of DNA lesions. 5-Fluoropyrimidines induce DNA lesions either by incorporation of the drug into DNA or by a mechanism not involving incorporation. The second mechanism, not involving incorporation, is also seen with methotrexate and hydroxyurea. The three anti-metabolites have in common their ability to reduce intracellular levels of nucleotides, resulting in reduced efficiency of repair of DNA lesions. The lesions probably appear spontaneously, independently of the drug treatment.

Increased growth inhibition and DNA lesions in human colon adenocarcinoma cells treated with methotrexate or 5-fluorodeoxyuridine followed by calmodulin inhibitors

The antineoplastic agents methotrexate and 5-fluorodeoxyuridine induce DNA lesions, although the drugs are not incorporated into DNA. The lesions arise as a result of reduced repair of damage occurring in DNA independently of the treatment with antineoplastic agents. When cells containing DNA lesions are treated with calmodulin inhibitors (W-7, phenothiazine, promethazine), the amount of lesions is increased, in all probability due to reduced DNA repair. This is paralleled by increased growth inhibition. Hence by inhibiting calmodulin, one can modulate the levels of DNA lesions and change the growth-inhibitory effect induced by methotrexate or 5-fluorodeoxyuridine. This strongly supports the importance of this type of DNA lesion in the toxic effects induced by the drugs.

Extensive regions of single-stranded DNA in aphidicolin-treated melanoma cells

We have looked for the presence of single-stranded DNA in human melanoma cells. Single-stranded DNA was observed by lysis of cells in dilute alkali (to partly denature the DNA) followed by CsCl gradient centrifugations. In normally growing cells we did not observe single-stranded DNA whereas large amounts were present in cells treated with aphidicolin (an inhibitor of DNA polymerase alpha). The single-stranded DNA is much larger (greater than 20 kb) than Okazaki fragments. When the cells were washed free of aphidicolin, the single-stranded DNA was converted to high molecular weight DNA. Furthermore, when DNA synthesis is recovering after drug treatment, the single-stranded DNA disappears. The single-stranded DNA represents a transient step during the maturation of newly synthesized DNA.

Treatment with dilute alkali-nuclease S1 permits the analysis of DNA damage: cells treated with platinum analogues

We describe here an approach to characterize various lesions induced in DNA by drug treatments, using three parameters: (a) release of single-stranded DNA fragments by cell lysis in dilute alkali, which result from enzymatic strand scission during DNA repair or chemical alterations of DNA; (b) the presence of high molecular weight DNA in cells after lysis in dilute alkali followed by nuclease S1 treatment which, due to drug-induced DNA cross-links and its level is a measure of the amount of DNA-containing cross-links; and (c) the appearance of small double-stranded DNA fragments, when the cell lysis is followed by digestion with nuclease S1 to remove single-stranded DNA. This DNA shows the same characteristics as DNA of untreated cells, but it may contain monoadducts. By following the flow of label through the three parameters, one can characterize both the lesions induced in DNA and how the lesions are repaired. We report here results of three platinum analogues: cis-Pt(II), trans-Pt(II), and cis-FLAP(II). A large proportion of DNA in treated cells appears as fragments (parameter c). The cis- compounds and trans- compounds differ with regard to appearance of high molecular weight DNA (parameter b) and the initial release of fragments (parameter a).

Conversion of post-elongation stage DNA to mature DNA occurs even if movement of the replication fork has stopped

During DNA synthesis there is a distinct stage immediately after the joining of large DNA replication intermediates (post-elongation stage). The conversion of this DNA to mature DNA was analysed in cells treated with aphidicolin to stop the movement of the replication fork. In such cells mature DNA is formed. In contrast, UV-A, which induces a wide spectrum of DNA lesions, inhibits the conversion to mature DNA. The data indicate that the maturation of the post-elongation stage can be uncoupled from the movement of the replication fork.

W-7, a calmodulin inhibitor, potentiates dacarbazine cytotoxicity in human neoplastic cells

Dacarbazine induces damage in replicative DNA, with a maximum level at 24 hr after treatment. Repair of these lesions does not occur when cells are post-treated with the calmodulin inhibitor W-7. In parallel cell cytotoxicity increases. The augmentation effect of W-7 is prevented by simultaneous incubation of cells with high levels of calmodulin and does not occur in cells pre-treated with aphidicolin (to stop DNA synthesis). Furthermore, W-5, an analogue of W-7 with a less inhibitory effect on calmodulin, does not interfere with DNA repair. The results show that calmodulin and/or calmodulin-regulated proteins are involved in the repair process of dacarbazine-induced DNA lesions.

5,6-Dichloro-1-beta-O-ribofuranosylbenzimidazole induces DNA damage by interfering with DNA topoisomerase II

We have examined DNA in cells treated with 5,6-dichloro-1-beta-O-ribofuranosylbenzimidazole (DRB), an adenosine analogue. The results show that DRB induces an partial fragmentation of DNA when the cells are lysed in dilute alkali. Fragmentation of DNA does not occur in control cells, nor in cells pretreated with novobiocin or VP-16/VM-26. The data show that DRB interferes with DNA topoisomerase II. In agreement with this interpretation, crude nuclear extracts of DRB-treated cells result in reduced in vitro KC1/SDS precipitation of covalent protein-DNA complexes. Formation of covalent complexes is typical of topoisomerase-DNA interaction.

Inhibition of poly(ADP-ribose) synthetase potentiates cell dacarbazine cytotoxicity

Dacarbazine induces DNA lesions in cells synthesizing new DNA. When poly(ADP-ribosylation) is inhibited with 3-aminobenzamide, repair of the dacarbazine-induced DNA lesions is reduced. This is parallelled by increased cytotoxicity. Cells pre-treated with aphidicolin (to stop DNA synthesis) are resistant to dacarbazine.

DNA lesions in human neoplastic cells and cytotoxicity of 5-fluoropyrimidines

We have examined the induction of alkali-labile regions in DNA of human neoplastic cells treated with 5-fluorouracil and 5-fluorodeoxyuridine. 5-Fluorouracil induces DNA lesions by two mechanisms: incorporation of drug into DNA and a second mechanism not involving the incorporation. The second mechanism is seen in cells treated with aphidicolin, a specific inhibitor of DNA polymerase alpha, to stop the movement of the DNA replication forks. 5-Fluorodeoxyuridine is not incorporated into DNA of these cells; only the second mechanism of induction of alkali-labile DNA is detected. The second mechanism is in all probability due to inefficient DNA repair of normally occurring defects in purine and pyrimidine residues. Furthermore there is a correlation between increasing levels of alkali-labile regions in the DNA and cytotoxicity of the drugs. This may be one explanation for the cytocidal effects of 5-fluoropyrimidines.

Leucovorine prevents methotrexate from inducing DNA lesions

Methotrexate induces DNA strand fragmentation. We show here that the induction of DNA lesions can be overcome by treatment with leucovorine, a folic acid analogue.

Ca2+ and calmodulin are involved in the processes conferring stability to DNA in proliferating neoplastic cells

We have examined, in proliferating neoplastic cells, the effect on DNA of EGTA (a chelator of Ca2+) and W7 (an inhibitor of calmodulin). The treatment results in release of single-stranded DNA fragments (2-10 kb) from pre-labelled HMW DNA. When DNA from synchronized neoplastic cells in S phase is examined, almost all pre-labelled DNA appears as short fragments. However, fragmentation does not occur in growth-arrested cells or in normal cells. Furthermore, fragmentation can be prevented by incubating cells in excessive amounts of Ca2+. Hence Ca2+ and the Ca2+-binding protein calmodulin are involved in the processes conferring stability to DNA in proliferating neoplastic cells.

There exists a distinct stage during mammalian DNA synthesis immediately after joining of replication intermediates

We describe an approach, using alkaline cell lysis and digestion with nuclease S1, which permits to distinguish between newly ligated DNA and the DNA of mature chromatin. When cells with steady-state labelled DNA (mature DNA) are analyzed, the results show labelled "nucleosomal-sized" DNA. However, when DNA of cells pulse-labelled with thymidine for 45 seconds is examined one can detect only large DNA. The newly ligated DNA is not reduced to "nucleosomal-sized" DNA by nuclease S1. When the large DNA is denatured in formamide one can detect 10 kb DNA fragments. Furthermore in pulse-chase experiments there appear, after formamide-treatment, increasing amounts of "nucleosomal-sized" DNA with a parallel decrease in the amount of 10 kb DNA fragments. Hence the newly ligated, large, DNA differs from mature DNA and represents a distinct stage during DNA replication.

The increased cytotoxicity in colon adenocarcinoma of methotrexate-5-fluorouracil is not associated with increased induction of lesions in DNA by 5-fluorouracil

Sequential methotrexate-5-fluorouracil (Mtx-5-Fu) reduces proliferation of human colon adenocarcinoma cells. The DNA of treated cells was examined by cell lysis in dilute alkali in order to detect if there is any release of single-stranded DNA fragments, which occurs in cells treated with 5-Fu. The results showed that in spite of increased cytotoxicity of Mtx-5-Fu there is reduced release of DNA fragments. The findings are paralleled by a reduced incorporation of 5-Fu into DNA. Hypoxanthine reduces the growth inhibitory effect of Mtx-5-Fu. In treated cells grown in the presence of hypoxanthine, alkaline lysis causes release of DNA fragments from bulk DNA, in contrast to cells grown without hypoxanthine. Hence, the increased cytotoxicity of Mtx-5-Fu in human colon adenocarcinoma is not associated with enhanced lesions in DNA by 5-Fu.