Aneuploidy in breast cancer: a fluorescence in situ hybridization study

Joint Clustering of Single-Cell Sequencing and Fluorescence In Situ Hybridization Data for Reconstructing Clonal Heterogeneity in Cancers

Aneuploidy and whole genome duplication (WGD) events are common features of cancers associated with poor outcomes, but the ways they influence trajectories of clonal evolution are poorly understood. Phylogenetic methods for reconstructing clonal evolution from genomic data have proven a powerful tool for understanding how clonal evolution occurs in the process of cancer progression, but extant methods so far have limited the ability to resolve tumor evolution via ploidy changes. This limitation exists in part because single-cell DNA-sequencing (scSeq), which has been crucial to developing detailed profiles of clonal evolution, has difficulty in resolving ploidy changes and WGD. Multiplex interphase fluorescence in situ hybridization (miFISH) provides a more unambiguous signal of single-cell ploidy changes but it is limited to profiling small numbers of single markers. Here, we develop a joint clustering method to combine these two data sources with the goal of better resolving ploidy changes in tumor evolution. We develop a probabilistic framework to maximize the probability of latent variables given the pre-clustered datasets, which we optimize via Markov chain Monte Carlo sampling combined with linear regression. We validate the method by using simulated data derived from a glioblastoma (GBM) case profiled by both scSeq and miFISH. We further apply the method to two GBM cases with scSeq and miFISH data by reconstructing a phylogenetic tree from the joint clustering results, demonstrating their synergistic value in understanding how focal copy number changes and WGD events can collectively contribute to tumor progression.

Prognostic value of TOP2A gene amplification and chromosome 17 polysomy in early breast cancer

The aim of this study was to analyze the occurrence of TOP2A gene amplification and chromosome 17 polysomy in patients with early breast cancer and to correlate the status of these alterations with the prognostic significance expressed as patients' clinical features and survival. Such concurrent analyses of TOP2A gene status and chromosome 17 polysomy have not been performed before. Study group included 149 consecutive stage I-III patients administered standard multimodality treatment. TOP2A abnormalities were examined by standard fluorescence in situ hybridization (FISH) and developed by our group quantitative real-time PCR (qPCR). TOP2A amplification and deletion assessed by FISH were found in 23% and 7% of the tumours, respectively, and by qPCR in 31% and 11% of the tumours, respectively. Chromosome 17 polysomy was detected in 40% of the cases. TOP2A amplification (by qPCR) correlated with shorter disease-free survival (p = 0.03) and overall survival (p = 0.047), and the prognostic value of TOP2A was confirmed in the multivariate analysis (HR = 3.22, 95% CI 1.09-9.56, p = 0.03). TOP2A gene amplification, but not chromosome 17 polysomy, carries negative prognostic information in early breast cancer. Given the aforementioned results, qPCR might serve as a prognostic tool in determining the patient's prognosis.

RECONSTRUCTING TUMOR PHYLOGENIES FROM HETEROGENEOUS SINGLE-CELL DATA

Studies of gene expression in cancerous tumors have revealed that tumors presenting indistinguishable symptoms in the clinic can be substantially different entities at the molecular level. The ability to distinguish between these genetically distinct cancers will make possible more accurate prognoses and more finely targeted therapeutics, provided we can characterize commonly occurring cancer sub-types and the specific molecular abnormalities that produce them. We develop a new method for identifying these common tumor progression pathways by applying phylogeny inference algorithms to single-cell assays, taking advantage of information on tumor heterogeneity lost to prior microarray-based approaches. We combine this approach with expectation maximization to infer unknown parameters used in the phylogeny construction. We further develop new algorithms to merge inferred trees across different assays. We validate the expectation maximization method on simulated data and demonstrate the combined approach on a set of fluorescent in situ hybridization (FISH) data measuring cell-by-cell gene and chromosome copy numbers in a large sample of breast cancers. The results further validate the proposed computational methods by showing consistency with several previous findings on these cancers and provide novel insights into the mechanisms of tumor progression in these patients.

The causes and consequences of polyploidy in normal development and cancer

Although nearly all mammalian species are diploid, whole-genome duplications occur in select mammalian tissues as part of normal development. Such programmed polyploidization involves changes in the regulatory pathways that normally maintain the diploid state of the mammalian genome. Unscheduled whole-genome duplications, which lead primarily to tetraploid cells, also take place in a substantial fraction of human tumors and have been proposed to constitute an important step in the development of cancer aneuploidy. The origins of these polyploidization events and their consequences for tumor progression are explored in this review.

Breast cancer and aneusomy 17: implications for carcinogenesis and therapeutic response

Abnormalities of chromosome 17, recognised over two decades ago to be important in tumorigenesis, often occur in breast cancer. Changes of specific loci on chromosome 17 including ERBB2 amplification, P53 loss, BRCA1 loss, and TOP2A amplification or deletion are known to have important roles in breast-cancer pathophysiology. Numerical aberrations of chromosome 17 are linked to breast-cancer initiation and progression, and possibly to treatment response. However, the clinical importance of chromosome 17 anomalies, in particular the effect on ERBB2 protein expression, is unknown. Reports are conflicting regarding the association of copy gain of chromosome 17 (polysomy 17) with strong ERBB2 protein expression in the absence of true ERBB2 gene amplification. Copy-number anomalies in chromosome 17 seem to be common in tumours that show discrepant ERBB2 expression and in tumours with discordant ERBB2-protein and ERBB2 gene copy number measurements. The mechanisms of ERBB2 dosage changes-gene amplification versus chromosome gain and loss-probably differ in primary and metastatic disease; however, a correction for chromosome 17 copy-number is necessary to completely distinguish between these mechanisms. A better understanding of how polysomy 17 affects gene-copy number and protein expression will help to select patients who will respond to therapies targeting ERBB2 and other protein products of chromosome 17 loci.

Numerical aberrations of chromosomes 1 and 7 by fluorescent in situ hybridization and DNA ploidy analysis in breast cancer

The goals of this study were to detect the numerical alterations of chromosomes 1 and 7 in breast cancer and to correlate the findings with DNA ploidy status as well as with parameters of prognostic significance. Fluorescence in situ hybridization (FISH) with centromeric probes for chromosomes 1 and 7 and cellular DNA content measurement by image analysis-based cytophotometry were applied on interface nuclei from fresh tissue imprints of 59 breast ductal carcinomas. Immunohistochemical stainings for estrogen receptor (ER), progesterone receptor (PR), HER-2, p53, and Ki67 were performed on paraffin tumor sections. The correlation between DNA ploidy and chromosomal aberrations revealed a significant association between aneuploidy and aneusomy for both chromosomes 1 (p=0.002) and 7 (p=0.00001), however, a number of diploid tumors were found to be aneusomic, especially for chromosome 1. Chromosome 7 polysomy was significantly associated with a higher incidence of axillary lymph node metastasis (p=0.05), poorly differentiated (grade III) tumors (p=0.03), negative ER and PR status (p=0.02 and 0.001, respectively), as well as p53 protein expression (p=0.05) and a higher Ki67 labeling index (p=0.004). Chromosome 1 aneusomy was only related with HER-2 protein overexpression (p=0.05). No association between chromosome alterations and tumor size was detected. In conclusion, the results of our study indicate that the detection of numerical aberrations of chromosomes 1 and 7 by FISH seems to be more sensitive than DNA ploidy status for the evaluation of abnormal cellular DNA and chromosome 7 aneusomy characterizes tumors with aggressive features and therefore might be a useful predictor of unfavorable biological behavior in breast cancer.

Tetraploidy and chromosomal instability are early events during cervical carcinogenesis

Chromosomal instability as manifested by increases in aneuploidy and structural chromosome aberrations is believed to play a critical role in the intermediate to late stages in the development of cervical malignancies. The current study was designed to determine the role of tetraploidy in the formation of aneuploidy and ascertain the occurrence of these alterations during the earlier stages of cervical carcinogenesis. Cervical cell samples, with diagnoses ranging from Normal to high-grade lesions, (HSIL) were obtained from 143 women and were evaluated for chromosomal alterations using dual-probe fluorescence in situ hybridization. Cervical cells from a subset of the group were also evaluated for chromosomal instability in the form of micronuclei. The frequencies of cells exhibiting either tetrasomy or aneusomy for Chromosomes 3 and 17 increased significantly with disease progression and displayed distinctive patterns where aneusomy was rarely present in the absence of tetrasomy. The frequencies of micronuclei that formed through either chromosomal loss or breakage increased significantly in both the low-grade and high-grade diagnostic categories and were highly correlated with both the number of tetrasomic and aneusomic cervical cells. In addition, a unique chromosomal alteration involving a significant non-random loss of Chromosome 17 specific to near-tetraploid aneusomic cells (trisomy 17 and tetrasomy 3) was observed. We conclude that tetraploidy and chromosomal instability are related events occurring during the early stages of cervical carcinogenesis that predispose cervical cells to the formation of aneuploidy frequently involving the loss of Chromosome 17.

Centrosomal aberrations in primary invasive breast cancer are associated with nodal status and hormone receptor expression

Our purpose was to assess the presence of centrosomal aberrations as measured by immunohistochemistry in primary invasive breast cancer and their association with established and proposed prognostic factors. Tissue sections of 103 primary invasive breast cancers were examined using centrosome-specific antibodies to pericentrin and gamma-tubulin. At least 3 different tumor regions per case were examined to determine maximum centrosomal aberration levels, which represent the proportion of cells with abnormal centrosomes in the region with the highest percentage of cells with centrosomal aberrations. The chi(2) test was performed to evaluate the association of maximum centrosomal aberration levels with patient age; tumor size; nodal status; nuclear grade; hormone receptor and Her2/neu expression; proportion of Ki67-, p53- and Bcl-2-positive tumor cells; DNA index; S-phase fraction; and proliferation index. With pericentrin immunohistochemistry, maximum centrosomal aberration levels >35% were detectable in 92 of the 103 breast carcinomas (89%). We found a highly significant correlation of maximum centrosomal aberration levels above 35% with axillary nodal tumor involvement (p < 0.0001) and the absence of hormone receptors (p < 0.0001). In addition, there was a borderline significant relationship with age <50 years (p = 0.050) and Her2/neu overexpression (p = 0.050). Among node-negative patients, maximum centrosomal aberration levels >35% were also associated with an increased DNA index (p = 0.006). In a subset of patients, additional staining of centrosomes with a monoclonal anti-gamma-tubulin antibody essentially confirmed these results. In primary invasive breast cancer, centrosomal aberrations are associated with those factors predicting a more aggressive course of disease. This might indicate a fundamental role of centrosomal dysfunction in disease evolution, possibly as a result of chromosome missegregation during mitosis.

Molecular evolutionary patterns in breast cancer

Geno-phenotypic patterns of pre-invasive and invasive lobular breast cancers and infiltrating ductal carcinomas of low, intermediate, and high grade are reviewed. One of the main differences between lobular breast cancers and ductal carcinomas is the presence of inactivating E-cadherin gene mutations in lobular breast cancers. In many other respects, lobular breast cancers and low-grade ductal carcinomas exhibit similar geno-phenotypic profiles. The development of p53 dysfunction may be a hallmark of infiltrating ductal cancers of intermediate and high grade. Sequential Her-2/neu and ras abnormalities define a subset of aggressive high-grade tumors, and the development of Rb dysfunction may define a separate subset of aggressive ductal cancers. Based on these observations, a branching molecular evolutionary model for the development and progression of breast cancer is proposed.

Abnormal chromosome 8 copy number in cytological smears from breast carcinomas detected by means of fluorescence in situ hybridization (FISH)

Numerical change in chromosome 8 is an acquired abnormality associated with high clinical stage and may be involved in the conversion of carcinoma in situ in the breast to invasive carcinoma. Fine needle aspiration smears from 53 cases of breast carcinoma were hybridized with centromeric probes for chromosome 8 and the X chromosome. Thirty-eight cases revealed chromosome 8 copy gain. Of the 45 grade II and III tumours, 28 showed polysomy (>3 signals) and six showed trisomy. Of the eight grade I tumours, four were trisomic, none were polysomic. There were only two cases of chromosome 8 copy loss (one each of grade I and III). X chromosome polysomy was also a frequent finding although the signal counts were similar to those for chromosome 8 in only a few cases. Chromosome 8 polysomy occurs frequently in breast carcinoma and high copy number (>3) is associated with high malignancy grade.

Aneuploidy theory explains tumor formation, the absence of immune surveillance, and the failure of chemotherapy

The autocatalyzed progression of aneuploidy accounts for all cancer-specific phenotypes, the Hayflick limit of cultured cells, carcinogen-induced tumors in mice, the age distribution of human cancer, and multidrug-resistance. Here aneuploidy theory addresses tumor formation. The logistic equation, phi(n)(+1) = rphi(n) (1 - phi(n)), models the autocatalyzed progression of aneuploidy in vivo and in vitro. The variable phi(n)(+1) is the average aneuploid fraction of a population of cells at the n+1 cell division and is determined by the value at the nth cell division. The value r is the growth control parameter. The logistic equation was used to compute the probability distribution for values of phi after numerous divisions of aneuploid cells. The autocatalyzed progression of aneuploidy follows the laws of deterministic chaos, which means that certain values of phi are more probable than others. The probability map of the logistic equation shows that: 1) an aneuploid fraction of at least 0.30 is necessary to sustain a population of cancer cells; and 2) the most likely aneuploid fraction after many population doublings is 0.70, which is equivalent to a DNA(index)=1.7, the point of maximum disorder of the genome that still sustains life. Aneuploidy theory also explains the lack of immune surveillance and the failure of chemotherapy.

Expression and mutational analyses of the human MAD2L1 gene in breast cancer cells

Breast cancer is a heterogeneous disorder in which most tumors display some degree of aneuploidy, especially those at later stages of the disease. Aneuploidy and associated chromosome instability may be important in the progression of mammary tumorigenesis. Aneuploidy is prevented during normal cell division in part through regulation of a mitotic spindle checkpoint where mitotic arrest prevents segregation of misaligned chromosomes into daughter cells at anaphase. Mitotic arrest genes, including the MAD family, which was originally characterized in yeast, help regulate normal function of the mitotic spindle checkpoint. Decreased expression of the human gene MAD2L1 was previously reported in a breast cancer cell line exhibiting chromosome instability and aneuploidy. To explore further the potential role of MAD2L1 in breast cancer, we analyzed MAD2L1 gene expression in 13 minimally to grossly aneuploid human breast cancer cell lines and found significant differences of expression in three lines. Sequence analysis of MAD2L1 cDNA in these as well as nine additional aneuploid breast cancer and five immortalized normal human mammary epithelial cell lines revealed one heterozygous frameshift (572 del A) mutation in a cancer cell line that demonstrated a high level of transcript expression. In addition, two 3'UTR sequence variants were noted in breast cancer cell lines. The 572 del A mutation creates a truncated MAD2 protein product. Further functional studies in primary breast tumors are therefore warranted to determine the potential role MAD2L1 may play in breast cancer.

Incidence of chromosomes 1 and 17 aneusomy in breast cancer and adjacent tissue: an interphase cytogenetic study

BACKGROUND

Characterization of the biopathologic events underlying the early steps of breast carcinogenesis may have a dramatic impact on reducing breast cancer mortality. Genes involved in breast tumorigenesis are localized on chromosomes 1 and 17, and numeric aberrations of these chromosomes have been correlated with breast cancer tumorigenesis and progression. According to the field cancerization hypothesis, specific chromosome aberrations may be present in breast cancer and in normal-appearing adjacent tissue. The latter changes reflect the genomic damage that follows longterm carcinogenic exposure and precede the morphologically detectable neoplastic transformation. We hypothesize that detection of these aberrations in benign breast epithelium may provide a tool for molecular risk assessment.

STUDY DESIGN

Using fluorescence in situ hybridization with centromere-specific probes, we determined the status of chromosomes 1 and 17 in fresh imprints of 28 samples of primary tumors and 54 samples of their surrounding uninvolved parenchyma taken from patients undergoing operations for breast carcinoma. Ten contralateral breast biopsy specimens collected from patients with previous breast carcinoma were also evaluated as a surrogate of a high-risk group to rule out the hypothesis that chromosomal aneusomy in tumor-adjacent tissue could be related to a paracrine effect of the primary tumor. Ten samples of benign breast tissue taken from patients at low risk were used as controls to define tolerance limits for aneusomy definition.

RESULTS

Using threshold values of 40% of signal loss and 13% of signal gain to define chromosome aneusomy (ie, mean + 3 SDs of the control group signals), we found the following: 1) almost all primary breast tumors were aneusomic for chromosomes 1 and 17; 2) primary breast tumor and adjacent uninvolved parenchyma shared the same pattern of chromosomes 1 and 17 aneusomy in 66.7% of patients; and 3) chromosomes 1 and 17 aneusomies in contralateral benign breast samples from high-risk patients were not different from those in primary breast tumor or adjacent tissue samples.

CONCLUSIONS

These results suggest that chromosomes 1 and 17 aneusomy may represent an intermediate biomarker of breast tumorigenesis potentially useful to detect patients at high risk of breast carcinoma who may benefit from preventive interventions.

Treatment of leptomeningeal metastases evaluated by interphase cytogenetics

PURPOSE

Although cytologic examination of CSF is the primary method for the evaluation of response to therapy for leptomeningeal metastases (LMMs), the procedure's sensitivity decreases throughout the course of protracted therapy. We studied whether this response could be monitored more accurately through the detection of numerical chromosomal aberrations by interphase cytogenetics, using fluorescence in situ hybridization (FISH).

PATIENTS AND METHODS

Seven patients treated for LMMs and with a known numerical aberration for chromosome 1 in their pretreatment CSF were included in this study. Up to 16 consecutive CSF samples were analyzed by means of the fluorescence in situ hybridization (FISH) technique for cells with aberrant chromosome 1 content. The results of routine cytology and FISH analyses were compared and were correlated with each patient's neurologic status.

RESULTS

Routine cytology detected malignancies in only 24 of the 76 samples, all of which were classified as chromosomally abnormal by FISH (except for two samples that could not be evaluated). Moreover, FISH demonstrated aneusomic cells in 32 additional samples, which could therefore be classified as malignant. The FISH results correlated better with patient neurologic status in that more malignant cells were detected in the CSF of neurologically deteriorating patients.

CONCLUSION

Using FISH in addition to performing routine cytologic examination of CSF led to a more accurate evaluation of response to treatment in patients treated for LMMs.

Histopathologic analysis of chromosome aneuploidy in ductal carcinoma in situ

Formalin-fixed, paraffin-embedded sections from 28 cases of ductal carcinoma in situ (DCIS; 12 with coexisting invasive neoplasm) were analyzed for numerical alterations of chromosomes 7, 8, 16, and 17 by performing fluorescence in situ hybridization (FISH) using centromeric (alpha-satellite) probes. Based on signal counts in 200 to 300 nuclei, each hybridization was classified as disomic (copy loss in <40%, copy gain in < 10%), monosomic (copy loss in at least 50% of nuclei, partial if 40% to 49%) or trisomic/polysomic (copy gain in at least 20% of nuclei, partial if 10% to 19%). Grade I lesions were characterized by complete lack of significant chromosome gain, but 29% showed partial (focal) monosomy. Grade III lesions, in contrast, showed partial or complete trisomy/polysomy in 88% of hybridizations versus monosomy in only 4%. Grade II DCIS exhibited a mixed pattern of chromosome aneuploidy: 38% hybridizations were disomic, 36% trisomic/polysomic, and 26% monosomic (8 of 10 hybridizations showing complete monosomy occurred in grade II lesions). Disomic hybridizations exhibiting rare cells (5% to 10%) with copy gain were more frequent in tumors with coexisting invasive neoplasm (5 of 17 v 2 of 33, P = .02). In morphologically heterogeneous lesions, higher-grade foci were characterized by chromosome copy gain relative to corresponding lower-grade areas in 17 of 22 (77%) hybridizations. These results show the presence of multiple (at least 3) distinct chromosome aneuploidy patterns in DCIS, in keeping with divergent mechanisms of genetic alteration. Degree of chromosomal instability, moreover, may correlate with progression of DCIS to invasive growth, implying that genetic instability is a parameter that impacts the likelihood of early breast carcinoma progression.

Multiple polysomies in breast carcinomas: preferential gain of chromosomes 1, 5, 6, 7, 12, 16, 17, 18, and 19

Chromosome G-banding analysis of metaphase cells from 16 primary breast carcinomas revealed the presence of multiple polysomies in near-diploid as well as in polyploid cells. Chromosome 17 was preferentially gained in 7 tumors, followed in frequency by chromosomes 1, 12, and 19 (5 tumors each), and chromosomes 5, 6, 7, 16, and 18 (4 tumors each). Eleven of the 16 carcinomas had, apart from the clones exhibiting the numerical gains, other unrelated clones. Nine of these 11 cases had clones with structural chromosome aberrations, 5 of which had structural aberrations involving the short arm of chromosome 3. The biologic significance, if any, of this seemingly nonrandom coexistence of multiple polysomies with structural aberrations of 3p is at present not known. The pattern of numerical chromosome aberrations observed in the present study is comparable to previous results from fluorescence in situ hybridization (FISH) studies, with the use of centromeric probes on interphase cells. However, unlike FISH studies, which have been focused on chromosomes 1, 3, 7, 8, 11, 16, and 17, the cytogenetic results reveal that other chromosomes also may be nonrandomly gained as part of multiple polysomies in breast carcinomas. In addition, the tumors with multiple polysomies were generally of high histologic grade and with metastasis to axillary lymph nodes, suggesting that multiple wholechromosome gains may be a pathway of genetic evolution or progression or both in some breast carcinomas.

Chromosome 11 aneuploidy detected by fluorescent in situ hybridization (FISH) in breast cancer: relation with progesterone receptor expression

Progesterone receptor (PR) expression is known to be impaired in breast cancer. As the PR gene is located on chromosome 11 which is also often affected, we studied their relationship in 15 patients with breast carcinoma. Tumoural imprints were used for PR immunocytochemistry and for FISH with chromosome 11 centromeric probes. Distribution profiles of chromosome 11 number in PR+ and PR- cell populations were examined. No difference in the number of chromosome 11 was found between PR+ and PR- breast tumours. Thus, loss of PR expression in breast cancer cannot be explained only by loss of chromosome 11; other genetic or non-genetic mechanisms should be advanced.

Interphase cytogenetics of chromosomes 11 and 17 in fine needle aspirates of breast cancer

The aims of this investigation were to compare quantitative with qualitative analysis of fluorescent in situ hybridization (FISH) centromere signals in interphase breast cancer cell nuclei and to evaluate the possible clinical utility of detecting numerical abnormalities of chromosomes 11 and 17 by FISH in the preoperative prediction of breast cancer histological grade. Commercial digoxigenin-labeled centromere probes to chromosomes 11 and 17 were hybridized to 69 malignant aspirates with histological follow-up. Aspirates were categorized as disomic or aneusomic for chromosomes 11 and 17 qualitatively; a subset of aspirates was also analyzed quantitatively. The quantitative and qualitative approaches resulted in almost identical categorisation. There was a significant association between the qualitative categorization of aspirates as aneusomic or disomic, the histological grade of the excised tumours (P = .0695, n = 69), and the cytological grade of the clinical aspirates (P = .006, n = 35). Although histological grade III tumors were almost invariably polysomic for one or both chromosomes, polysomy was also detected in grade I and II tumors. Qualitative FISH analysis was shown to be more sensitive than cytological grading in predicting histological grade III but was of lower specificity and was therefore not clinically useful.

Child with mosaic variegated aneuploidy and embryonal rhabdomyosarcoma

We report on a 7-year-old boy with mosaic variegated aneuploidy (MVA) who developed embryonal rhabdomyosarcoma of the soft palate. This patient is the 11th case report of MVA and represents further documentation of the true existence of this rare mitotic mutant. Clinical findings share similarities to those previously described patients including microcephaly and growth retardation as the two most common abnormalities. Notably, mental retardation is not universally present. Results of serial cytogenetic analyses performed on somatic and neoplastic tissues are reviewed and compared with those of other previously reported patients. We postulate that mosaic variegated aneuploidy is causally related to the development of rhabdomyosarcoma in our patient. This is the first report of a patient with MVA who developed cancer and suggests that these patients may be at risk for malignancy and require long-term follow-up and cancer surveillance.

Comparison of chromosomal aberrations detected by fluorescence in situ hybridization with clinical parameters, DNA ploidy and Ki 67 expression in renal cell carcinoma

To evaluate the significance of chromosomal aberrations in renal cell carcinoma, fluorescence in situ hybridization (FISH) was used to determine its prevalence and correlation with clinical parameters of malignancy. In addition, correlation of chromosomal aberration with Ki 67 expression was analysed. We performed FISH with chromosome-specific DNA probes, and the signal number of pericentromeric sequences on chromosomes 3, 7, 9 and 17 was detected within interphase nuclei in touch preparations from tumour specimen. The incidence of loss of chromosome 3 was significantly higher than those of chromosomes 7, 9 and 17 (P < 0.001, P = 0.03 and P < 0.001 respectively). Hyperdiploid aberration of chromosomes 3 and 17 was significantly correlated with tumour stage (P = 0.03, P = 0.02 respectively), whereas hyperdiploid aberration of chromosome 9 was associated with nuclear grade (P = 0.04). Disomy of chromosome 7 was correlated with venous involvement (P = 0.04). Ki 67 expression was significantly associated with hyperdiploid aberration of chromosome 17 (P = 0.01), but not with aberration of chromosome 3. There was a significant relationship between hyperdiploid aberration of chromosome 7 and Ki 67 expression (P = 0.01). In conclusions, gain of chromosome 17 may reflect tumour development, and aberration of chromosome 7 may affect metastatic potential of malignancy, whereas loss of chromosome 3 may be associated with early stage of tumour development in renal cell carcinoma.

Chromosome aberrations in renal tumors detected by fluorescence in situ hybridization

The aim of this study was to investigate the relationship between chromosome aberrations detected by fluorescence in situ hybridization (FISH) and tumor grade, stage, venous involvement, and DNA ploidy status in 18 renal tumors. Using FISH with chromosome-specific DNA probes, the copy number of pericentromeric sequences on chromosomes 3, 7, 9, and 17 was detected within interphase nuclei in touch preparations from tumor specimens. Monosomy for chromosome 3 was detected in seven of 9 DNA diploid tumors, whereas all DNA aneuploid tumors demonstrated trisomy or tetrasomy for chromosome 7. Moreover, monosomy for chromosome 3 was more frequently shown in the diploid and low-stage tumors than in the aneuploid and high-stage tumors. The percentage of hyperdiploid cells significantly correlated with DNA ploidy status in the case of chromosomes 3 and 7 (p = 0.030, p = 0.007, respectively). The percentage of hyperdiploid cells for chromosome 3 had borderline significance with tumor stage. On the other hand, the percentage of diploid cells for chromosome 17 was significantly correlated with DNA ploidy status and tumor stage (p = 0.030, p = 0.027, respectively). Moreover, the percentage of diploid cells for chromosome 7 in renal cell carcinoma (RCC) with venous involvement was significantly lower than those without venous involvement (p = 0.023). These results suggest that the incidence of chromosomal aberrations detected by FISH is more frequent than the chromosomal aneuploidy reported previously by conventional cytogenetics. Therefore, loss of chromosome 3 may be associated with an early event in RCC carcinogenesis. Gain of chromosomes 3 and 7 is correlated with tumor progression as well as gain and loss of chromosome 17. Study of the chromosomal aberrations may provide a greater understanding of tumor carcinogenesis and progression in RCC.

Flow cytometric DNA hypertetraploidy is associated with unfavourable prognostic features in breast cancer

AIM

Breast tumours with a DNA content higher than 4N (hypertetraploidy) are not well characterised. The aim of this study was to evaluate the clinical and biological characteristics of 51 hypertetraploid breast carcinomas selected from a series of 860 consecutive cases analysed by flow cytometry.

METHODS

The clinicopathological characteristics of the hypertetraploid group were compared with those of a control group of 138 non-hypertetraploid breast carcinomas. Breast tumours from patients submitted to surgery as primary therapeutic approach (15 hypertetraploid and the 138 non-hypertetraploid) were TNM staged and classified according to the histological type and grade. The remaining 36 patients had advanced neoplastic disease at presentation and were classified by cytological criteria only. DNA flow cytometric analysis was performed on fresh-frozen samples stained with propidium iodide. Hormone receptors were analysed by immunocytochemistry.

RESULTS

The incidence of hypertetraploid breast tumours was 5.9% (51 of 860). All the patients were women and the mean age at diagnosis was 65 years. There was a family history of breast cancer in 21.6% of cases. In the group of operated patients, 33.3% had pT3 tumours and 53.3% had axillary lymph node metastases. All but one tumour were invasive ductal carcinomas; the remaining was an invasive papillary carcinoma. Ten (66.7%) tumours were classified as poorly differentiated carcinomas. Oestrogen and progesterone receptors were negative in 33 (64.7%) and 38 (74.5%) tumours, respectively. At last follow up, 35 (72.9%) patients were alive, while 13 (27.1%) died of disease within three years of diagnosis. Statistical comparison of the clinicopathological features of hypertetraploid v non-hypertetraploid breast carcinomas yielded a significant difference in tumour size (p < 0.001), histological grade (p < 0.001), hormone receptor status (p < 0.001), and overall survival (p < 0.001) between the two groups.

CONCLUSION

Flow cytometric DNA hypertetraploidy is related to clinicopathological features of breast cancer usually associated with unfavourable prognosis.

Origins and clinical implications of aneuploidy in early bladder cancer

Cytogenetic and flow cytometric studies in a variety of human solid tumors have suggested that gross aneuploidy may arise by a process of abrupt chromosome complement doubling followed by gradual chromosome loss. However, this sequence has not been demonstrated directly in serial studies in individual patients in vivo. The purpose of this study was to search for evidence of chromosome complement doubling and subsequent chromosome loss in flow cytometric ploidy patterns in serial bladder washings and/or biopsies from individual patients with early bladder cancer. Fifty-two patients with noninvasive bladder cancer were followed with serial flow cytometric DNA studies for periods ranging from 5.1 to 42.7 months (median 15.1 months). Serial changes in DNA ploidy and S phase fractions were recorded and correlated with histologic and/or cytologic findings, response to treatment and clinical outcome. The data suggest a series of genetic evolutionary changes in early bladder cancer that include the initial development of peridiploid aneuploidy and repeated rounds of DNA content doubling with chromosome loss in patients with progressive disease. It is likely that gross DNA aneuploidy, and more specifically, DNA multiploidy and DNA hypertetraploidy, all arise by this mechanism. The sequence of DNA diploidy, peridiploid aneuploidy, near-tetraploidy, hypotetraploidy and hypertetraploidy is associated with a progressive increase in S phase fraction, and with increasing tumor grade; late steps in this ploidy sequence were often present in tumors that were refractory to local therapeutic measures and tumors that developed deep tumor invasion and/or distant metastases. We conclude that DNA multiploidy and hypertetraploidy are markers of advanced stages of genetic evolution in human bladder cancer.