Ploidy pattern and cell cycle in breast cancer as detected by image analysis and flow cytometry

A Lamin-Binding Ligand Inhibits Homologous Recombination Repair of DNA Double-Strand Breaks

Nuclear lamins are type V intermediate filament proteins. Lamins, including LA, LB1, LB2, and LC, are the major protein components forming the nuclear lamina to support the mechanical stability of the mammalian cell nucleus. Increasing evidence has shown that LA participates in homologous recombination (HR) repair of DNA double-strand breaks (DSBs) . However, the mechanisms underlying this process are incompletely understood. We recently identified the first lamin-binding ligand 1 (LBL1) that directly binds LA and inhibited cancer cell growth. We provided here further mechanistic investigations of LBL1 and revealed that LA interacts with the HR recombinase Rad51 to protect Rad51 from degradation. LBL1 inhibits LA-Rad51 interaction leading to accelerated proteasome-mediated degradation of Rad51, culminating in inhibition of HR repair of DSBs. These results uncover a novel post-translational regulation of Rad51 by LA and suggest that targeting the LA-Rad51 axis may represent a promising strategy to develop cancer therapeutics.

Genomic instability in laminopathy-based premature aging

Premature aging syndromes often result from mutations in nuclear proteins involved in the maintenance of genomic integrity. Lamin A is a major component of the nuclear lamina and nuclear skeleton. Truncation in lamin A causes Hutchinson-Gilford progerial syndrome (HGPS), a severe form of early-onset premature aging. Lack of functional Zmpste24, a metalloproteinase responsible for the maturation of prelamin A, also results in progeroid phenotypes in mice and humans. We found that Zmpste24-deficient mouse embryonic fibroblasts (MEFs) show increased DNA damage and chromosome aberrations and are more sensitive to DNA-damaging agents. Bone marrow cells isolated from Zmpste24-/- mice show increased aneuploidy and the mice are more sensitive to DNA-damaging agents. Recruitment of p53 binding protein 1 (53BP1) and Rad51 to sites of DNA lesion is impaired in Zmpste24-/- MEFs and in HGPS fibroblasts, resulting in delayed checkpoint response and defective DNA repair. Wild-type MEFs ectopically expressing unprocessible prelamin A show similar defects in checkpoint response and DNA repair. Our results indicate that unprocessed prelamin A and truncated lamin A act dominant negatively to perturb DNA damage response and repair, resulting in genomic instability which might contribute to laminopathy-based premature aging.

Ploidy analysis of field cancerization and cancer development in the hamster cheek pouch carcinogenesis model

BACKGROUND

The hamster cheek-pouch carcinogenesis model is a well-known animal system that closely mimics the development of premalignant and malignant lesions in human oral cancer. Our aim was to numerically characterize the premalignant and malignant lesions and expressions of field cancerization in this model using ploidy as the end-point.

METHODS

To study the DNA content and proliferation status of the cells in this model we assessed the Feulgen reaction and the immunohistochemical reaction for 5-bromo-2-deoxiuridine (BrdU) in different histological areas of serial tissue sections of the cheek pouches of animals injected with BrdU.

RESULTS

Ploidy values were higher in cancerized epithelia with no unusual microscopic features (NUMF), in preneoplastic and tumor areas than in control epithelia. The aneuploidy index was higher in NUMF areas than in control and differed significantly from control in preneoplastic areas and carcinoma.

CONCLUSIONS

The unexpected alteration in DNA content observed in NUMF epithelia is of great relevance as a biomarker of field cancerized areas.

DNA ploidy pattern in choroidal melanoma: correlation with survival. A flow cytometry study on archival material

BACKGROUND/AIMS

Paraffin embedded samples have provided an important source of material for retrospective cytofluorimetric studies, useful in establishing the predictive value of DNA content measurements. The aim of this study was to investigate the incidence and type of aneuploidy in choroidal malignant melanomas (CMM) and the significance in the clinical outcome (median follow up 55 months).

METHODS

DNA content was quantified by flow cytometry in 61 CMM from archival material. Non-tumour ocular tissue was used as the reference diploid standard. Cases in which the coefficient of variation (CV) of the diploid peak was > 8% were excluded. The CMM were classified as spindle A, spindle B, mixed spindle and epithelioid, epithelioid, and necrotic.

RESULTS

The frequency of the aneuploid DNA pattern was 38%. Necrotic tumours showed a worse clinical outcome independent of the ploidy pattern. Spindle A tumours were found to be diploid. Spindle B and mixed tumours showed a prevalent diploid and near diploid aneuploid pattern (DI < 1.3), yet aneuploidy was not correlated with a worse prognosis. The epithelioid tumours were prevalently diploid. However, 83% of the aneuploid tumours were hypodiploid (DI < 0.95), and showed the worst prognosis.

CONCLUSION

These results indicate that increasing DNA abnormalities in CMM, especially in the epithelioid histotype, were associated with an increasing mortality.

Prognostic significance of DNA content and S-phase fraction in epithelial ovarian carcinomas analyzed by image cytometry

The objective of this study was to evaluate the prognostic significance of DNA ploidy and S-phase fraction (SPF) in epithelial ovarian carcinomas analyzed by image cytometry. Frozen tissue of 103 epithelial ovarian carcinomas was analyzed for DNA ploidy and SPF with a Cell Analysis System Image Analyser (CAS 200, Becton-Dickinson) and correlations with clinical and histomorphologic factors and time to progression and overall survival were evaluated by univariate and multivariable analysis. Fifty-four percent of the ovarian carcinomas were found to be diploid, 38% aneuploid, and 8% tetraploid. The S-phase fraction was low (<5%) in 27%, intermediate (5-14.5%) in 47%, and high (>/=14.5%) in 26% of the patients. By univariate analysis overall survival and time to progression were significantly correlated with the S-phase fraction (P = 0.003 and P = 0.003), but not with DNA ploidy (P = 0. 31 and P = 0.51). A DNA index > 1.4 was correlated with poor outcome but the result did not achieve formal statistical significance (P = 0.08 and P = 0.12). A high SPF was a strong predictor of early recurrence, while a low SPF identified patients with a favorable long-term outcome. Other significant predictors of survival were FIGO stage, grade of differentiation, presence of distant metastasis, residual tumor, lymph node metastasis, and patient age. In multivariable statistical analysis only FIGO stage, histologic grade, and residual tumor after surgery were independent predictors of overall survival and time to progression.

DNA ploidy pattern in papillary renal cell carcinoma. Correlation with clinicopathological parameters and survival

Papillary renal cell carcinoma (PRCC) is a less frequent histomorphologic variant of renal cortical carcinoma (RCC). Morphologically, PRCC differs from other forms of RCC in that it is associated with frequent tumor infiltration by macrophages and lymphocytes, and a tendency for central necrosis and cystic change. Follow-up data revealed that survival rates are higher among patients with PRCC than among patients with other forms of RCC. The authors explore the DNA content in a series of PRCC and correlate the findings with nuclear grade, pathological stage and survival. Using Flow Cytometry, we analysed the DNA ploidy pattern of 37 paraffin-embedded PRCC. At least 3 tumor fragments were analysed in each case. To obtain the reference diploid standard, the non-tumor renal tissue from the same case was added to the solution. Tumor ploidy was classified as diploid and aneuploid. The degree of DNA content abnormalities was given by the DNA Index (DI). An aneuploid DNA profile was found in 65% of the tumors. 25% of the aneuploid tumors presented near diploid peaks (1.10 < DI < 1.30; low degree aneuploidy), 25% were hyperdiploid, while 22% had a hypodiploid profile (DI < 0.90). A homogeneous DNA ploidy pattern was observed in 25 tumors (68%), while there was intratumoral heterogeneity in 12 tumors (32%). Patients with aneuploid DNA patterns had high grade/stage tumors and died at the end of the follow-up period, while patients with diploid/near diploid profiles had low grade/stage tumors and survived. However, the multi-way analysis of variance performed in order to investigate the prognostic significance of ploidy pattern against tumor stage and grade showed a highly significant main effect of ploidy pattern. Moreover, the patients with hypodiploid DNA profile presented the worst prognosis. These results suggest that the DNA profile of PRCC is a highly significant prognostic index.

Image cytometric analysis in pathology

Image cytometry (ICM) is used in surgical pathology to quantify nuclear DNA content, nuclear and cytoplasmic immunostain. DNA aneuploidy is shown to be an independent negative prognostic factor in malignant melanoma, small cell carcinoma of the lung, esophageal, ovarian, endometrial, prostatic, urinary bladder, and papillary thyroid carcinoma. On bladder washings, DNA ploidy by ICM is used as an aid in diagnosis and management of recurrent transitional cell carcinoma of the bladder. Quantitation of nuclear immunostain for proliferation markers by ICM has clinical significance in prognosis and management of solid tumors of bladder, breast and ovary, astrocytoma, lymphoma, and malignant melanoma. Angiogenesis, measured by microvessel density is a predictor of prognosis in breast carcinoma and an independent predictor of metastasis for breast carcinoma, malignant melanoma, non-small cell lung carcinoma, and prostate carcinoma. Quantitated by ICM, angiogenesis is predictive of the presence or subsequent development of regional lymph node metastases in head and neck squamous carcinomas. Future prospects for ICM in pathology include the standardization of ICM techniques; extended clinical use of DNA ploidy for diagnosis, prognosis and as a help with therapeutic decisions; development of neural networks and quantification of fluorescence in situ hybridization to distinguish benign from malignant lesions of low malignant potential, and three-dimensional reconstruction of morphology from two-dimensional sections measured for prognostic parameters.

Comparison of flow and image cytometry for DNA content analysis of fresh and formalin-fixed, paraffin-embedded tissue in breast carcinoma

DNA ploidy and S-phase fraction are considered to be prognostic variables in breast carcinoma. DNA content of 35 cases of breast carcinoma of varying histologic types and nuclear grades was analyzed by flow cytometry and image analysis in both fresh and formalin-fixed, paraffin-embedded tissue. Fresh cell and deparaffinized nuclear suspensions were used for flow cytometry. Fresh and deparaffinized tumor tissue samples were used for image analysis. The results of analysis for DNA ploidy, DNA index of DNA aneuploid Go/G1 peaks, and S-phase fraction were compared in different tissue preparations for both techniques. The two techniques produced comparable DNA ploidy results with both fresh and formalin-fixed, paraffin-embedded tissue. Sensitivity for detection of DNA aneuploidy was somewhat greater by image analysis, particularly in deparaffinized tissue. There was 89% agreement in detection of DNA aneuploidy by flow cytometry in fresh and paraffin-embedded, formalin-fixed tissue; the coefficients of variation of the DNA diploid Go/G1 peaks were much wider in the latter. In image analysis there was 91% agreement between fresh and fixed specimens. Agreement between the flow cytometry and image analysis in fresh specimens was 91%; in deparaffinized nuclear suspensions it was 94%. There is a high degree of correlation between the values of DNA index of DNA aneuploid Go/G1 peaks; the estimates of S-phase fraction are much more variable. Results also show a good correlation of the DNA ploidy with the nuclear grades.(ABSTRACT TRUNCATED AT 250 WORDS)