Ontario familial colon cancer registry: methods and first-year response rates

The Ontario Familial Colon Cancer Registry (OFCCR) is a novel registry that collects family history information, epidemiologic data, blood samples and tumour specimens from a population-based sample of colorectal cancer patients and their families. Families are classified as either high familial risk, intermediate familial/other risk or low (sporadic) risk for colorectal cancer. Obtaining high response rates in genetic family studies is especially challenging because of both the time commitment required and issues of confidentiality. The first-year response rate was 61%, resulting in 1,395 participating probands. In an attempt to assess potential response bias, we compared participants with non-participants. The age and sex of participants did not differ from non-participating probands; however, cases in rural areas were somewhat more likely to participate. To date, 57% of 1,587 relatives participated; females were more likely to participate, and relatives of low familial risk were least likely to participate. The OFCCR is an excellent resource that will facilitate the study of genetic and environmental factors associated with colorectal cancer.

Induction of a fatigue-resistant phenotype in rabbit fast muscle by small daily amounts of stimulation

We have shown that fatigue resistance can be induced in rabbit tibialis anterior (TA) muscles without excessive power loss by continuous stimulation at low frequencies, such as 5 Hz, and that the same result is obtained by delivering a 10-Hz pattern in equal on/off periods. Here we ask whether the same phenotype could be produced with daily amounts of stimulation that would be more appropriate for clinical use. We stimulated rabbit TA muscles for 6 wk, alternating fixed 30-min on periods of stimulation at 10 Hz with off periods of different duration. All patterns transformed fast-glycolytic fibers into fast-oxidative fibers. The muscles had fatigue-resistant properties but retained a higher contractile speed and power production than muscles transformed completely to the slow-oxidative type. We conclude that in the rabbit as little as one 30-min period of stimulation in 24 h can result in a substantial increase in the resistance of the muscle to fatigue.

Localization of a putative transcriptional regulator (ATRX) at pericentromeric heterochromatin and the short arms of acrocentric chromosomes

ATRX is a member of the SNF2 family of helicase/ATPases that is thought to regulate gene expression via an effect on chromatin structure and/or function. Mutations in the hATRX gene cause severe syndromal mental retardation associated with alpha-thalassemia. Using indirect immunofluorescence and confocal microscopy we have shown that ATRX protein is associated with pericentromeric heterochromatin during interphase and mitosis. By coimmunofluorescence, ATRX localizes with a mouse homologue of the Drosophila heterochromatic protein HP1 in vivo, consistent with a previous two-hybrid screen identifying this interaction. From the analysis of a trap assay for nuclear proteins, we have shown that the localization of ATRX to heterochromatin is encoded by its N-terminal region, which contains a conserved plant homeodomain-like finger and a coiled-coil domain. In addition to its association with heterochromatin, at metaphase ATRX clearly binds to the short arms of human acrocentric chromosomes, where the arrays of ribosomal DNA are located. The unexpected association of a putative transcriptional regulator with highly repetitive DNA provides a potential explanation for the variability in phenotype of patients with identical mutations in the ATRX gene.

The dose-related response of rabbit fast muscle to long-term low-frequency stimulation

Rabbit tibialis anterior muscles were stimulated continuously at 2.5 Hz, 5 Hz, or 10 Hz for 10 months. The resulting adaptive transformation was dose-related for contractile speed, myosin isoform composition, and enzyme activities. The "fast-oxidative" state produced by stimulation at 2.5 Hz was stable: even after 10 months, 84% of the fibers were of type 2A. Absence of a secondary decline in oxidative activity in these muscles provided strong evidence of a causal link between myosin transitions and metabolic adaptation. Significant fiber loss occurred only after prolonged stimulation at 10 Hz. The myosin isoform composition of individual muscles stimulated at 5 Hz resembled that of muscles stimulated at either the lower or the higher frequency, behavior consistent with a threshold for fiber type change. In clinical applications such as cardiomyoplasty, muscles could be used more effectively by engineering their properties to combine speed and power of contraction with the necessary resistance to fatigue.

Cost-utility analysis of paclitaxel in combination with cisplatin for patients with advanced ovarian cancer

The standard treatment for patients with advanced ovarian cancer (AOC) has been cyclophosphamide and cisplatin (CP). Recently, the results of a large randomized comparative trial demonstrated that the combination of paclitaxel and cisplatin (TP) provided a progression-free survival benefit of 5 months. In this study, a cost-utility analysis was performed from a Canadian health care system perspective to estimate the incremental cost-effectiveness of the TP combination. Twelve AOC patients who received treatment with TP were matched for age and disease stage on a 1-to-2 basis with a CP control. Total hospital resource consumption was then collected for all patients. Treatment preferences were estimated from a cohort of 20 patients and 40 healthy female volunteers using the time trade-off technique. The outcomes were then generated through a decision-analytic model. First-line treatment costs with TP were approximately fourfold greater on a per-cycle basis than the CP alternative (Can$1911 vs Can$459). When progression-free survival benefit and patient treatment preferences were incorporated into the analysis, the results of the decision model revealed an incremental cost between Can$12,000 and Can$24,000 per quality-adjusted progression-free year with the TP protocol. Even though the TP combination has a considerably higher drug acquisition cost, the results of the current analysis suggest that this new chemotherapy regimen does provide patients with substantial quality-adjusted progression-free survival benefit at a reasonable cost to the Canadian health care system.

New Ontario familial breast cancer registry to facilitate genetic and epidemiologic studies

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Variegated expression of a globin transgene correlates with chromatin accessibility but not methylation status

There are now many mammalian examples in which single cell assays of transgene activity have revealed variegated patterns of expression. We have previously reported that transgenes in which globin regulatory elements drive the lacZ reporter gene exhibit variegated expression patterns in mouse erythrocytes, with transgene activity detectable in only a sub-population of circulating erythroid cells. In order to elucidate the molecular mechanism responsible for variegated expression in this system, we have compared the chromatin structure and methylation status of the transgene locus in expressing and non-expressing populations of erythrocytes. We find that there is a difference in the chromatin conformation of the transgene locus between the two states. Relative to active transgenes, transgene loci which have been silenced exhibit a reduced sensitivity to general digestion by DNase I, as well as a failure to establish a transgene-specific DNase I hypersensitive site, suggesting that silenced transgenes are situated within less accessible chromatin structures. Surprisingly, the restrictive chromatin structure observed at silenced transgene loci did not correlate with increased methylation, with transgenes from both active and inactive loci appearing largely unmethylated following analysis with methylation-sensitive restriction enzymes and by sequencing PCR products derived from bisulphite-converted genomic DNA.

Fast-to-slow transformation in stimulated rat muscle

Several previous studies have failed to demonstrate changes due to chronic stimulation in contractile speed of innervated fast rat muscles, and it has been suggested that the adaptive capacity of skeletal muscle in this species is limited. We have reassessed this contention. Fast muscles of the rat hind limb were stimulated continuously at 10 or 20 Hz for 55-61 days. The maximum shortening velocity of the extensor digitorum longus muscles was reduced to 50% of the control value. The proportion of type 1 fibers increased from 4% in control muscle to 34% in stimulated muscles and there was a corresponding reduction in type 2B/D fibers. The proportion of type 2A fibers after stimulation was similar to that in control muscles. These results, taken together with our published analyses of myosin isoform composition of these muscles, show that the mechanisms that control gene expression in response to activity are not exclusive to larger mammals.

Induction of a fast-oxidative phenotype by chronic muscle stimulation: histochemical and metabolic studies

Chronic electrical stimulation of skeletal muscle at 10 Hz induces fast-to-slow fiber type transformation. Does a lower aggregate amount of activity lead to a less complete transformation, or does it produce the same transformation over a longer time course? We examined this question by subjecting adult rabbit tibialis anterior and extensor digitorum longus muscles to continuous stimulation at 2.5 Hz for 2-12 wk. Most of the fibers acquired the histochemical and immunocytochemical characteristics of type 2A, not type 1, fibers. There was a corresponding rise in oxidative activity, but this was accompanied by a marked decline in anaerobic glycolysis. The activities of hexokinase and 3-oxoacid CoA-transferase stopped increasing after 2 wk, glutamate oxaloacetate transaminase after 4 wk, and beta-hydroxyacyl-CoA dehydrogenase after 6 wk of stimulation. Succinate dehydrogenase, citrate synthase, lactate dehydrogenase, and creatine phosphokinase continued to change up to 12 wk of stimulation. Changes in enzyme activity were not as rapid or as marked as those observed for stimulation at 10 Hz, and none showed the typical two-phase response of oxidative enzyme activities to stimulation at 10 Hz. The latter may therefore be dependent on induction of type 1 myosin isoforms.

Induction of a fast-oxidative phenotype by chronic muscle stimulation: mechanical and biochemical studies

We studied changes in the mechanical properties and myosin isoform composition of rabbit tibialis anterior muscles that were subjected to continuous stimulation at 2.5 Hz for up to 12 wk. The effects of stimulation at 2.5 Hz were less profound than those observed for the same duration of stimulation at 10 Hz (12). Stimulation at 10 Hz for 12 wk induced complete transformation to a slow-contracting muscle homogeneous in slow myosin isoforms; stimulation for the same period at 2.5 Hz resulted in moderate changes in contractile speed and a very small increase in the synthesis of slow myosin isoforms. On the other hand, the fatigue resistance of muscles stimulated at 2.5 Hz was as great, in both isometric and dynamic fatigue tests, as that of the muscles stimulated at 10 Hz. Thus entire fast skeletal muscles can be transformed to a state in which fast myosin isoforms continue to be synthesized, but the oxidative capacity is sufficient to support sustained working at a higher power output than that associated with slow muscle.

A new polymorphic locus, D7S411, isolated by cloning from preparative pulse-field gels is close to the mutation causing cystic fibrosis

The mutation causing cystic fibrosis (CF) has been localized to the DNA sequence of 700 kb bounded by the loci identified by the markers pMP6d-9 (D7S399) and pJ3.11 (D7S8). A 560-kb fragment obtained after SacII digestion of DNA from a cell line containing this region of human chromosome 7 in a mouse background was separated using pulse-field gel electrophoresis and isolated from the gel. The DNA was digested with BamHI prior to cloning into lambda EMBL3. Approximately 0.1% of the resulting clones contained human repetitive sequences, and 24 such recombinants were studied. Of these, 23 are on chromosome 7; 8 clones were duplicated, and of the 15 different recombinants, 7 are between MET and INT1L1, and a further 7 are between INT1L1 and pMP6d-9, leaving a single marker, pG2, which is between pMP6d-9 and pJ3.11. pG2 recognizes an RFLP with XbaI. A cosmid walk from pG2 has generated a further marker, H80, which recognizes an RFLP with PstI. This new locus (D7S411) divides the remaining region between the CF flanking markers, thereby making it more accessible to fine pulse-field mapping and allowing the precise localization of further clones to this region. Although it is not possible to position the CF locus unequivocally with respect to D7S411, both polymorphic markers at this locus exhibit low but significant linkage disequilibrium with CF, placing the emphasis for the search for the gene on the D7S399 to D7S411 interval of 250 kb.

A randomized trial of two dose levels of cyclophosphamide, methotrexate, and fluorouracil chemotherapy for patients with metastatic breast cancer

This study was designed to assess the role of dosage of chemotherapy for treatment of metastatic breast cancer. One hundred thirty-three patients without prior chemotherapy for metastatic disease were randomly allocated to receive two different dose levels of cyclophosphamide (C), methotrexate (M), and fluorouracil (F), administered intravenously (IV) every 3 weeks. Patients were stratified by sites of disease (visceral, bone, or soft-tissue dominant) and by interval from primary surgery to first recurrence. Doses on the higher-dose arm were 600 mg/m2 (C,F) and 40 mg/m2 (M) with escalation if possible; doses on the lower-dose arm were 300 mg/m2 (C,F) and 20 mg/m2 (M) without escalation. Patients who failed to respond to lower-dose CMF were crossed over to the higher-dose arm. Patients randomized to the higher-dose arm had longer survival measured from initiation of chemotherapy (median survival, 15.6 months v 12.8 months, P = .026 by log-rank test), but the effect of dose was of borderline significance (P approximately 0.12) when adjusted for a chance imbalance between the two arms in the time from first relapse to randomization, using the Cox proportional hazards model. Response rates (International Union Against Cancer [UICC] criteria) for patients with measurable disease were higher-dose arm: 16/53 (30%) and lower-dose arm: 6/53 (11%), (P = .03). Only one of 37 patients responded on crossover from the lower- to the higher-dose arm. Patients experienced more vomiting, myelosuppression, conjunctivitis, and alopecia when receiving higher doses of chemotherapy. A series of 34 linear analogue self-assessment scales were used to make detailed quality of life assessments on a subset of 49 patients. These scales confirmed greater toxicity in the immediate posttreatment period, but also a trend to improvement in general health and some disease-related indices, in patients receiving higher-dose chemotherapy. This trial suggests that better palliation is achieved by using full-dose chemotherapy.

Eliciting preferences for alternative cancer drug treatments. The influence of framing, medium, and rater variables

In oncology there is increasing interest in the development of techniques to help patients choose between alternative therapies in ways that are consistent with their preferences. The purpose of this study was to examine some methodological problems associated with the elicitation of preferences. Preferences for alternative drug therapies were sought from 208 visitors to an open house at the Ontario Cancer Institute and from 216 university nursing students. Preferences were not significantly dependent on the sex, age or professional status of the respondents, nor on the medium used for elicitation of preferences (computer terminal versus pencil-and-paper questionnaire). In contrast, the importance of the way decision problems are framed was confirmed. Comparison of a positive frame (outcomes expressed as the probability of surviving) with a negative frame (outcomes expressed as the probability of dying) and a mixed frame (probabilities of surviving and dying were both given) pointed to the presence or absence of the word "survive" in the outcome description as the main source of framing bias. The framing effect was in the opposite direction to that hypothesized.

Letter: Gestational diabetes

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