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M Höglund

Publications and source records attributed to M Höglund.

At least 37 records · Page 2Linked to original sources
PubMed2001

The tumor-associated gene HMGIC is expressed in normal and osteoarthritis-affected synovia.

Chromosomal rearrangements involving chromosome bands 12q13-15 are very frequent findings in benign solid tumors, and recently, the primary molecular target for these aberrations was identified as the gene HMGIC. However, mutations in this gene have also been observed in nonneoplastic tissues. In a previous study, we reported breakpoints within HMGIC of synovia affected by osteoarthritis (OA) in two cases with 12q15 aberrations. To analyze further the role of HMGIC in this disease, we have performed cytogenetic, fluorescent in situ hybridization (FISH), RNA, and protein expression analyses on synovial samples from patients with OA and individuals without signs of the disorder. Cytogenetic analysis of short-term cultured cells revealed clonal 12q13-15 aberrations in 2/36 cases of OA synovia and no rearrangement in any of the five controls. With FISH analysis, it was shown that the chromosomal breakpoints in the two aberrant cases were located outside the HMGIC locus. In contrast, at RNA and protein expression analyses, OA-affected as well as normal synovia displayed transcription and translation of the gene. We also analyzed whether immunoreactivity for HMGIC was associated with the proliferation-specific antigen Ki-67, but no correlation between the staining patterns of these proteins was observed. From the results of the present study, it is evident that expression of HMGIC cannot simply be considered a sign of neoplasia or an effect of proliferation.

Adolescent↗
PubMed2001

Paired multiplex reverse-transcriptase polymerase chain reaction (PMRT-PCR) analysis as a rapid and accurate diagnostic tool for the detection of MLL fusion genes in hematologic malignancies.

The MLL gene in chromosome band 11q23 is frequently rearranged in acute lymphoblastic and acute myeloid leukemias. To date, more than 50 different chromosomal regions are known to participate in translocations involving 11q23, many of which affect MLL. The pathogenetically important outcome of these rearrangements is most likely the creation of a fusion gene consisting of the 5' part of the MLL gene and the 3' end of the partner gene. Although abnormalities of the MLL gene as such are generally associated with poor survival, recent data suggest that the prognostic impact varies among the different fusion genes generated. Hence, detection of the specific chimeric gene produced is important for proper prognostication and clinical decision making. We have developed a paired multiplex reverse-transcriptase polymerase chain reaction analysis to facilitate a rapid and accurate detection of the most frequent MLL fusion genes in adult and childhood acute leukemias. To increase the specificity, two sets of primers were designed for each fusion gene, and these paired primer sets were run in parallel in two separate multiplex one-step PCR reactions. Using the described protocol, we were able to amplify successfully, in one single assay, the six clinically relevant fusion genes generated by the t(4;11)(q21;q23) [MLL/AF4], t(6;11)(q27;q23) [MLL/AF6], t(9;11)(p21-22;q23) [MLL/AF9], t(10;11)(p11-13;q23) [MLL/AF10], t(11;19)(q23;p13.1) [MLL/ELL], and t(11;19)(q23; p13.3) [MLL/ENL] in cell lines, as well as in patient material.

Biomarkers, Tumor↗
PubMed2001

Comparable aciclovir exposures produced by oral valaciclovir and intravenous aciclovir in immunocompromised cancer patients.

The objective of this study was to evaluate the comparability of systemic aciclovir exposure at steady state in immunocompromised patients following oral valaciclovir 1000 mg tds and intravenous (iv) aciclovir 5 mg/kg tds. A two-centre, randomized, open label, two-way crossover study was undertaken. Patients aged 18-65 years who had undergone high-dose chemotherapy for cancer and were neutropenic (neutrophil count <0.5 x 109/mL) with normal renal function were recruited. The pharmacokinetic parameters of aciclovir after oral valaciclovir 1000 mg or iv aciclovir 5 mg/kg given as 1 h infusion, each administered every 8 h for seven doses, were compared. Fifteen patients were enrolled and 13 completed both treatments. The mean (s.d.) values for aciclovir after oral valaciclovir and iv aciclovir were: AUC0-8 76.3 (29.7) and 64.2 (20.0) microM x h; peak plasma concentration (Cmax) 26.6 (10.5) and 34.0 (11.9) microM; time to maximal plasma concentration (tmax) 2.01 (0.65) and 0.95 (0.19); and plasma elimination half-life (t1/2) 2.83 (0.91) and 2.44 (0.62) h, respectively. The mean absolute bioavailability of aciclovir from oral valaciclovir was 60 +/- 21%. Equivalent systemic exposure to aciclovir after oral valaciclovir 1000 mg and iv aciclovir 5 mg/kg was observed with AUC0-8 (oral/iv ratio = 1.16; 90% CI 0.98-1.39), whilst significantly reduced peak aciclovir concentrations were obtained with oral valaciclovir (ratio = 0.75; 90% CI 0.60-0.94). Oral valaciclovir offers a convenient, and possibly safer, alternative to iv aciclovir, delivering comparable systemic exposures with reduced peak levels. This may contribute to shorter hospitalization, reduced costs for healthcare providers and improved quality of life for patients.

Acyclovir↗
PubMed2001

Activity of CHS 828 in primary cultures of human hematological and solid tumors in vitro.

CHS 828 is a pyridyl cyanoguanidine that has shown promising preclinical anticancer activity against various experimental tumor models and is presently being tested in a phase II trial in man. In the present study the fluorometric microculture cytotoxicity assay was used for in vitro evaluation of CHS 828 activity in primary cell cultures from hematological and solid tumors. In total, 156 samples from various diagnoses were tested with 72-h continuous drug exposure. CHS 828 showed high relative in vitro activity against tumor cells from chronic lymphocytic leukemia as well as from acute leukemia and high-grade lymphoma. Activity was also observed in several solid tumor cell samples, although the group as a whole appeared less responsive. CHS 828 was significantly more active against hematological malignancies compared to normal lymphocytes. Correlation analysis with standard drugs revealed low to moderate correlation coefficients. The results show that CHS 828 has potent antitumor activity against primary cultures of human tumor cells from patients and might have a unique mechanism of action.

Adolescent↗
PubMed2001

Fracture of the carpal scaphoid. A prospective, randomised 12-year follow-up comparing operative and conservative treatment.

We compared the long-term outcome in 61 patients (62 fractures) treated operatively or conservatively for an acute fracture of the carpal scaphoid. A total of 30 fractures was randomised to conservative treatment using a cast and 32 to operative treatment using a Herbert bone screw. The duration of sick leave was shorter for patients treated by operation, but this was only significant in patients with blue-collar occupations. There were no differences between the groups in respect of function, radiological healing of the fracture, or carpal arthritis after follow-up at 12 years. Those managed by operation showed radiological signs of arthritis of the scaphotrapezial joint more often, but this finding did not correlate with subjective symptoms. Operative treatment of an acute fracture of the scaphoid allows early return of function and should be regarded as an alternative to conservative treatment in patients in whom immobilisation in a cast for three months is not acceptable for reasons related to sports, social life or work.

Adolescent↗
PubMed2001

Characterization of chromosome aberrations in salivary gland tumors by FISH, including multicolor COBRA-FISH.

Fluorescence in situ hybridization (FISH), including COBRA-FISH, was used to characterize 11 salivary gland tumors that had been investigated by banding analysis. Five cases were pleomorphic adenoma (PA), three were adenoid cystic carcinoma, and one case each was mucoepidermoid carcinoma, carcinoma ex-pleomorphic adenoma (CaPA), and adenocarcinoma. All 11 cases were selected on the basis that they had shown rearrangement of 6q or 9p or had unresolved aberrations after karyotyping. The COBRA-FISH and FISH analyses led to a revised karyotype in all informative cases and made it possible to clarify almost all chromosomal rearrangements occurring in the tumors. Of particular note were the confirmation of the existence of 6q deletions, a common change in salivary gland carcinomas, and the demonstration that a seemingly balanced t(6;9) resulted in del(6q). Other rearrangements that were revealed by FISH included amplification of 12q sequences (MDM2 and CDK4) in one PA. We also investigated the status of the PLAG1 gene in four cases (one PA, one CaPA, one adenoid cystic carcinoma, and one mucoepidermoid carcinoma) with 8q12 rearrangements. Only in the former two cases were the FISH results compatible with intragenic rearrangements. Overall, the results of the study show that, even with good banding quality and in karyotypes of modest complexity, much new information will be gained by supplementing the banding analysis with a multicolor FISH approach, such as COBRA-FISH.

Adult↗
PubMed2001

Altered expression of TGFB receptors and mitogenic effects of TGFB in pancreatic carcinomas.

Alteration of the transforming growth factor beta (TGFB) signalling pathway is important in pancreatic carcinogenesis, as shown by the frequent inactivation of the downstream target SMAD4. We recently analysed a series of pancreatic carcinoma cell lines with respect to alterations of five SMAD genes involved in TGFB signalling, and showed that SMAD4 was structurally rearranged in 42% of these. This pathway may, however, also be affected by alterations of genes whose products regulate the activation of TGFB as well as of TGFB receptor genes. We therefore studied the expression of UPA, UPAR, IGF2R, ALK5 (TGFBR1), TGFBR2, TGFBR3, ENG, ALK1, TGFB1, TGFB2, and TGFB3 in a series of 14 pancreatic carcinoma cell lines. We also analysed ALK5 and TGFBR2 for mutations, cell surface localisation of TGFBR2 and ENG, and TGFB1 response. No mutations of ALK5 or TGFBR2 were found. However, 4 cell lines were methylated within the ALK5 promoter region. ALK5 expression was strongly reduced in 9 cases, whereas TGFBR2 expression was increased in 12 of the cell lines. The TGFB signalling associated receptors ENG and ALK1 were co-expressed in 4 of the cell lines. There was no evidence for disruption of the UPAR-IGF2R TGFB activating pathway. The response to TGFB1 was analysed in 12 cell lines, and 6 of these (50%) showed increased proliferation. The cell lines stimulated by TGFB showed frequent mutations of SMAD4, KRAS2, and TP53, as well as frequent absence of CDKN2B expression. These results suggest that the ALK5-SMAD4 part of the TGFB signalling pathway is a major target for inactivation in pancreatic carcinomas, that the expression of TGFBR2, TGFBR3, and receptors involved in TGFB activation are maintained, and that alterations of components of the TGFB signalling pathway may be accompanied by a positive effect of TGFB on cell growth.

Activin Receptors, Type I↗
PubMed2000

Chromosomal breakage-fusion-bridge events cause genetic intratumor heterogeneity.

It has long been known that rearrangements of chromosomes through breakage-fusion-bridge (BFB) cycles may cause variability of phenotypic and genetic traits within a cell population. Because intercellular heterogeneity is often found in neoplastic tissues, we investigated the occurrence of BFB events in human solid tumors. Evidence of frequent BFB events was found in malignancies that showed unspecific chromosome aberrations, including ring chromosomes, dicentric chromosomes, and telomeric associations, as well as extensive intratumor heterogeneity in the pattern of structural changes but not in tumors with tumor-specific aberrations and low variability. Fluorescence in situ hybridization analysis demonstrated that chromosomes participating in anaphase bridge formation were involved in a significantly higher number of structural aberrations than other chromosomes. Tumors with BFB events showed a decreased elimination rate of unstable chromosome aberrations after irradiation compared with normal cells and other tumor cells. This result suggests that a combination of mitotically unstable chromosomes and an elevated tolerance to chromosomal damage leads to constant genomic reorganization in many malignancies, thereby providing a flexible genetic system for clonal evolution and progression.

Chromosome Aberrations↗
PubMed2000

[Malpractice in connection with radius fractures must be reduced. Clear guidelines for treatment and follow-up are required].

PSR handles the vast majority of malpractice injuries in Sweden. PSR is a claims handling company which settles claims for malpractice on behalf of the insurance company owned by the Swedish county councils: the County Councils Mutual Insurance Company. A central issue in the law regulating patient injuries in Swedish health care is to define injuries that could have been avoided if a certain therapeutic/diagnostic procedure or a more appropriate method had been utilized. PSR arranged a multiprofessional conference regarding guidelines to decrease the number of malpractice injuries in the treatment of distal radius fractures. Among the most important issues defined were: To improve and standardize diagnostic imaging Patient information Early decision making in surgery and physical/occupational therapy A more well-defined indication for surgery, in which type of trauma, biological age and functional demands are considered in addition to radiographs Less stereotyped thinking in follow-up Controlled randomized trials.

Clinical Competence↗
PubMed2000

Cytogenetics of hepatoblastoma: further characterization of 1q rearrangements by fluorescence in situ hybridization: an international collaborative study.

BACKGROUND: Hepatoblastoma (HBT) is the most common hepatic neoplasm in children. This notwithstanding, little is known about pathogenetic factors, such as genetic abnormalities, of importance for the development and progression of this tumor type. To date, only 33 cytogenetically abnormal HBT have been published, and trisomies for chromosomes 2 and 20 have been shown to be the most frequent aberrations. Recently, unbalanced translocations involving proximal 1q have been described in several HBT, suggesting that a pathogenetically important gene maps to 1q. PROCEDURE: Six primary and one recurrent HBT were cytogenetically analyzed after short-term tissue culture. In addition, fluorescence in situ hybridization (FISH) studies, using locus-specific probes, were performed on three of these pediatric HBT as well as on one previously reported adult HBT. RESULTS: Total or partial trisomy 8, gain of chromosome 20, and structural rearrangements of chromosome 1 were detected in three HBT, and overrepresentation of chromosome 2 material was found in two HBT. The adjacent chromosome bands 1q12 and 1q21 were involved in three translocations, t(1;2), t(1;4), and t(1;11), which were all unbalanced and resulted in gain of 1q material. The previously reported adult HBT displayed 1q deletions with breakpoints at 1q12-21. FISH analyses of the 1q rearrangements revealed that all breakpoints were within the heterochromatic region. CONCLUSIONS: These findings provide further support for the importance of trisomies 2, 8, and 20 and rearrangements of 1q in the development of HBT. Furthermore, the consistent localization of breakpoints within the heterochromatic segment of chromosome 1 suggests that the important pathogenetic consequence of 1q abnormalities is the resulting genomic imbalance rather than a specific gene rearrangement.

Child, Preschool↗
PubMed2000

Cytogenetic and FISH studies of a single center consecutive series of 152 childhood acute lymphoblastic leukemias.

Between 1977 and 1996, cytogenetic investigations were performed on 182 childhood (< or = 16 yr) acute lymphoblastic leukemias (ALL), constituting 94% (182 of 194) of all ALL patients diagnosed and treated at the Departments of Pediatrics, Lund and Malmo University Hospitals, Sweden, during these two decades. The cytogenetic analyses were successful in 152 cases (84%). The failure rate was higher for the ALL investigated before 1987 (30% vs. 4%, p < 0.0001), and also the incidence of cytogenetically normal cases was higher during 1977-86 (43% vs. 25%, p < 0.05). Clonal chromosomal abnormalities were found in 103 (68%) ALL. Structural rearrangements were detected, by chromosome banding alone, in 76 cases (50%). Fluorescence in situ hybridization (FISH) was used to identify cases with t(12;21), 11q23 rearrangements, and 9p deletions, using probes for ETV6/CBFA2, MLL, and CDKN2A/B, in 72 cases from which cells in fixative and/or unstained metaphase preparations were available. In total, the most common structural rearrangements were del(9p) (17%), t(12;21) (15%), del(6q) (8%), and MLL rearrangements (4%). Six (32%) of nineteen cytogenetically normal ALL analyzed by FISH harbored cryptic abnormalities; three displayed t(12;21) and four had del(9p), one of which also carried a t(12;21). Five (45%) of the t(12;21)-positive ALL showed +der(21)t(12;21) or ider(21)(q10)t(12;21), resulting in the formation of double fusion genes. Among the more rare aberrations, eight structural rearrangements were identified as novel recurrent ALL-associated abnormalities, and nine cases harbored rearrangements previously not reported. Sixteen cases displayed karyotypically unrelated clones at different investigations. Seven ALL (5%) showed simple chromosomal changes, unrelated to the aberrations detected at diagnosis, during morphologic and clinical remission, and in all but one instance the patients remained in remission, with the abnormal clone disappearing in subsequent investigations. This indicates that the emergence of novel clonal chromosomal aberrations during remission in childhood ALL is rather common and does not by necessity predict a forthcoming relapse.

Adolescent↗
PubMed2000

Granulocyte colony-stimulating factor (G-CSF) induces the production of cytokines in vivo.

Granulocyte colony-stimulating factor (G-CSF) is a haematopoietic growth factor required for the proliferation and differentiation of haematopoietic precursors of neutrophil granulocytes and is now used to overcome congenital and acquired neutropenia. In addition to increasing the numbers of neutrophils in vivo and modulating neutrophil functions, G-CSF may induce the production of cytokines such as tumour necrosis factor alpha (TNF-alpha). In the present study, the plasma levels of granulocyte-macrophage colony-stimulating factor (GM-CSF) in six healthy volunteers given G-CSF at 10 microgram/kg once daily for 6 d were measured and found to be elevated. The elevated levels (P < 0.05) were detected on day 2, peaked on days 6-7 and returned to baseline on day 12. In vitro, G-CSF did not enhance the secretion of TNF-alpha and GM-CSF from mononuclear cells, whole blood or endothelial cells. However, in the co-presence of whole blood and endothelial cells, the secretion of TNF-alpha was significantly enhanced by G-CSF at low concentrations. The GM-CSF secretion, however, was unaltered. G-CSF pretreatment of whole blood suppressed lipopolysaccharide (LPS)-induced secretion of TNF-alpha and GM-CSF in a dose-dependent manner. These results together with our previous findings suggest that G-CSF induces the production of TNF-alpha and GM-CSF in vivo, and that this production may be due to the co-effects of endothelial cells and whole blood under the influence of G-CSF through an as yet unknown network of cells and cytokines. Treatment of whole blood with G-CSF suppresses LPS-induced secretion of TNF-alpha and GM-CSF.

Adult↗
PubMed2000

Locus-specific multifluor FISH analysis allows physical characterization of complex chromosome abnormalities in neoplasia.

Novel techniques in molecular cytogenetics have radically improved the ability to characterize genetic changes in neoplastic cells. In parallel, a rapid development in high-throughput genomics has resulted in detailed physical maps of the human genome. Combining these two fields, we have developed a method for the simultaneous visualization of several physically defined segments along a chromosome. Seven YAC clones and one subtelomeric cosmid clone from chromosome 12 were labeled with unique combinations of four fluors and hybridized to metaphase chromosomes from neoplastic cells. In a uterine leiomyoma and a myxoid liposarcoma with translocations 12;14 and 12;16, the breakpoints in chromosome 12 could be localized to the HMGIC and CHOP regions, respectively. In the other tumors, more complex aberrations were visualized, including two inversions in 12q with a common breakpoint between MDM2 and D12S332 in a pleomorphic adenoma, amplification of MDM2 and CDK4 in ring chromosomes from a malignant fibrous histiocytoma, and amplification of KRAS2 together with other unbalanced rearrangements in two pancreatic adenocarcinomas. Combinatorially labeled single-copy probes may thus simultaneously provide physical localization of breakpoints and an overview of complex structural rearrangements. Genes Chromosomes Cancer 28:347-352, 2000.

Chromosome Aberrations↗
PubMed2000

Characterization of genomically amplified segments using PCR: optimizing relative-PCR for reliable and simple gene expression and gene copy analyses.

Gene amplification is one of the mechanisms for oncogene activation in solid tumors. The size of the amplified regions may vary considerably among individual tumors, and more than one gene may be affected within the same amplicon. The main objective in analyzing genomic amplifications has therefore been to map the shortest region involved and to identify genes with increased expression as a result of the increased gene copy number. To facilitate such an analysis, we have developed simple polymerase chain reaction (PCR) procedures using the internal standards beta-actin (ACTB) and L1Hs for gene expression and gene copy number analyses, respectively. We used cDNA derived from pancreatic carcinoma cell lines, and genomic DNA extracted from the same cell lines, as templates in the gene expression and in the gene copy number analyses, respectively. To determine the optimal number of PCR cycles, dilution series of the templates were made. Furthermore, competing primers were used to adjust for differences in target sequence levels. We show that by these simple means it is possible to determine optimal conditions for expression analyses. In addition, the procedure was adapted for the analysis of gene copy number changes at the genomic level using L1Hs as the internal standard. This PCR method makes it possible to produce detailed gene copy number profiles of amplified genomic regions.

DNA Primers↗
PubMed1999

Isochromosome 17q in blast crisis of chronic myeloid leukemia and in other hematologic malignancies is the result of clustered breakpoints in 17p11 and is not associated with coding TP53 mutations.

An isochromosome of the long arm of chromosome 17, i(17q), is the most frequent genetic abnormality observed during the disease progression of Philadelphia chromosome-positive chronic myeloid leukemia (CML), and has been described as the sole anomaly in various other hematologic malignancies. The i(17q) hence plays a presumably important pathogenetic role both in leukemia development and progression. This notwithstanding, the molecular consequences of this abnormality have not been investigated in detail. We have analyzed 21 hematologic malignancies (8 CML in blast crisis, 8 myelodysplastic syndromes [MDS], 2 acute myeloid leukemias, 2 chronic lymphocytic leukemias, and 1 acute lymphoblastic leukemia) with i(17q) by fluorescence in situ hybridization (FISH). Using a yeast artificial chromosome (YAC) contig, derived from the short arm of chromosome 17, all cases were shown to have a breakpoint in 17p. In 12 cases, the breaks occurred within the Smith-Magenis Syndrome (SMS) common deletion region in 17p11, a gene-rich region which is genetically unstable. In 10 of these 12 cases, we were able to further map the breakpoints to specific markers localized within a single YAC clone. Six other cases showed breakpoints located proximally to the SMS common deletion region, but still within 17p11, and yet another case had a breakpoint distal to this region. Furthermore, using chromosome 17 centromere-specific probes, it could be shown that the majority of the i(17q) chromosomes (11 of 15 investigated cases) were dicentric, ie, they contained two centromeres, strongly suggesting that i(17q) is formed through an intrachromosomal recombination event, and also implicating that the i(17q), in a formal sense, should be designated idic(17)(p11). Because i(17q) formation results in loss of 17p material, potentially uncovering the effect of a tumor suppressor on the remaining 17p, the occurrence of TP53 mutations was studied in 17 cases by sequencing the entire coding region. In 16 cases, no TP53 mutations were found, whereas one MDS displayed a homozygous deletion of TP53. Thus, our data suggest that there is no association between i(17q) and coding TP53 mutations, and that another tumor suppressor gene(s), located in proximity of the SMS common deletion region, or in a more distal location, is of pathogenetic importance in i(17q)-associated leukemia.

Adolescent↗
PubMed1999

Molecular analyses of the 15q and 18q SMAD genes in pancreatic cancer.

SMAD4 (DPC4) is part of the TGFB signaling pathway and is frequently inactivated in pancreatic carcinomas. TGFB signals from the membrane to the nucleus via SMAD proteins. TGFB receptor activation results in SMAD2 and SMAD3 phosphorylation, which then form heteromeric complexes with SMAD4. Inhibitory SMADs, SMAD6 and SMAD7, can prevent TGFB signaling by interacting either with the receptor or with SMAD2 and SMAD3. The encoding sequences for these proteins are organized in two gene clusters, one at 18q21 (SMAD2, SMAD4, and SMAD7) and the other at 15q21-22 (SMAD3 and SMAD6). Losses of 15q and 18q material are frequent in pancreatic carcinomas, and in order to map the extent of 15q and 18q deletions and to investigate further the involvement of SMAD4 and the possible function of SMAD2 and SMAD3 as tumor suppressor genes in pancreatic carcinoma, we performed loss of heterozygosity studies as well as mutation and expression analyses of SMAD4, SMAD2, and SMAD3 in 13 low-passage cell lines from 12 pancreatic carcinoma patients. To investigate possible amplifications of SMAD6 and SMAD7, the genomic organization and the expression levels of these genes were analyzed. One tumor with homozygous loss of SMAD4 was detected, and mutations of this gene were found in four of the 12 carcinomas; no SMAD2 or SMAD3 inactivating genomic alterations were found. In none of the cases was transcriptional silencing seen. No genomic amplifications, mutations, or increased expression of SMAD6 and SMAD7 were detected. These results suggest that functional abrogation of SMAD2 or SMAD3 and increased expression of SMAD6 or SMAD7 are infrequent in pancreatic carcinomas and further stress the particular importance of SMAD4 inactivation in pancreatic carcinogenesis.

Aged↗
PubMed1999

Variable stability of chromosomes containing amplified alpha-satellite sequences in human mesenchymal tumours.

Alpha-satellite sequences are found in the centromeric region of all human chromosomes and have been implicated in centromeric function. We describe the structure and behaviour of chromosomes containing amplified human alphoid DNA from chromosome 12, in an osteosarcoma cell line (OSA) and an atypical lipomatous tumour (ALT). In OSA, the amplified material was detected in one large marker chromosome, whereas in ALT amplified sequences were observed in chromosomes of variable number and appearance. The marker in OSA was mitotically stable, but those in ALT exhibited a high degree of mitotic instability, forming bridges at anaphase and chromatin strings between interphase nuclei. The amplified alpha-satellite arrays reacted positively with human anti-centromeric antiserum and anti-centromere protein B antibodies in both tumours. Centromere protein C, previously shown to be present only in functional kinetochores, was invariably detected at the constriction of the marker in OSA, while one-fifth of markers in ALT appeared to exhibit additional centromere protein C-positive regions outside the primary constriction, indicating that the observed chromosomal instability in ALT might, at least in part, be a consequence of the occasional formation of more than one functional kinetochore. In OSA the alphoid DNA was coamplified with unique sequences from central 12q and the amplified material was C-band negative but in ALT amplified material from central 12q as well as sequences from proximal 12p were detected, resulting in C-band-positive areas. A propensity for additional kinetochore formation might thus be associated with the coamplification of alphoid DNA and pericentromeric sequences from chromosome 12.

Anaphase↗