Flow cytometric DNA analysis of squamous cell carcinoma of the esophagus

Chromosomal aneuploidies and combinational fluorescence in situ hybridization probe panels are useful for predicting prognosis for esophageal squamous cell carcinoma

BACKGROUND

Esophageal squamous cell carcinoma (ESCC) is a common cancer type in China. In this study, we aimed to develop aneuploidy markers for diagnosis and prognosis of ESCC.

METHODS

Chromosomal aneuploidies were detected in 493 primary tumors and 61 precancerous lesions by fluorescence in situ hybridization with chromosome enumeration probes (CEP), and cut-off values were set by receiver operating characteristic (ROC) curves.

RESULTS

According to the cut-off values, chromosomes 3, 8, 10, 12, 17 and 20 presented frequent gains, with rates of 70.1, 69.7, 58.9, 66.9, 67.5 and 77.2 % in tumors and of 32.1, 26.8, 33.9, 41.2, 44.0 and 42.0 % in precancerous lesions. Loss of chromosome Y was detected in 72.0 % of male patients. An optimal four-probe panel CEP3/12/17/20 was established for detecting ESCC (sensitivity: 86.1 %), and CEP3/10/12/20 for precancerous lesions (sensitivity: 48.0 %). Gain of CEP8 was significantly correlated with lymph node metastasis (LNM) and late stages (P = 0.002 and 0.001), and loss of CEPY with age (P = 0.002, male). Kaplan-Meier survival curves indicated that patients with positive CEP10/17 (pT1 + T2, P = 0.041) and CEP8/17 (stages IIb + III + IV, P = 0.002) had poor overall survival. Combinations of LNM/stage and CEP panels could divide patients into more subgroups, including LNM + CEP3/17, LNM + CEP10/17, LNM + CEP3/10/17, stage + CEP3/17, stage + CEP10/17 and stage + CEP3/10/17 (P = 0.0004, 0.0003, 0.0001, 0.005, 0.001 and 0.0008, respectively). Multivariate Cox regression analysis confirmed that the above combinational models were independent prognostic factors.

CONCLUSIONS

Our data suggest that the combinational probe sets may have potential for detection and prognostic prediction of ESCC.

Prognostic significance of CyclinD1 and E-Cadherin in patients with esophageal squamous cell carcinoma: multiinstitutional retrospective analysis. Research Committee on Malignancy of Esophageal Cancer, Japanese Society for Esophageal Diseases

BACKGROUND

Although many molecular biologic molecules have been analyzed for their prognostic influence on patients with esophageal cancer, previous studies have not been able to raise statistically significant prognostic factors.

STUDY DESIGN

Immunohistochemical analysis of CyclinD1 expression and E-Cadherin expression was performed retrospectively in 416 esophageal squamous cell cancer patients who underwent curative resection of esophageal cancer at 10 major surgical departments in Japan, where more than 30 esophagectomies are performed in a year. The prognostic impact of these molecules and their relationship to clinicopathologic data of the patients were evaluated.

RESULTS

Univariate analysis revealed that pN (pTNM), pT (pTNM), CyclinD1 expression, and E-Cadherin expression were significant prognostic factors, and multivariate analysis revealed that pN (risk ratio (RR) 2.19), pT (RR 3.35), CyclinD1 (RR 1.42), and E-Cadherin (RR 0.71) were significant prognostic factors. Combination analysis of these genes revealed that E-Cadherin-preserved and CyclinD1-negative patients had the best prognosis; E-Cadherin-reduced and CyclinD1-positive patients had the worst prognosis.

CONCLUSIONS

Increased CyclinD1 expression and reduced E-Cadherin expression were significant prognostic factors in patients with esophageal squamous cell carcinoma.

Prognostic factors of oesophageal squamous cell carcinoma from the perspective of molecular biology

Recent developments in molecular biology have revealed that several oncogenes, suppressor genes and adhesion molecules are involved in the development of oesophageal cancer; however, the role of these genes is still unknown. To evaluate which molecular biological factors are related to patients' prognosis and recurrence, we checked p53, p16, p21/Waf1, cyclin D1, Ki-67, epidermal growth factor receptor (EGFR), vascular endothelial growth factor (VEGF), Mdm2, Bcl2, E-cadherin and MRP1/CD9 by means of immunohistochemical analysis in 116 cases of oesophageal cancer (R0). We also checked the regrowth capability of the primary cultures of the resected tumours and the effect of post-operative treatment. Although univariate analysis revealed that pN (pTNM), pT (pTNM), sex, cyclin D1, Ki-67, VEGF, E-cadherin and cell regrowth capability were prognostic factors, multivariate analysis revealed that pN (risk ratio (RR) 3.17), sex (RR 8.13), cell regrowth capability (RR 3.03) and E-cadherin (RR 0.30) were prognostic factors. Interestingly, step-wise analysis revealed that the following five factors were prognostic factors: pN (RR 5.74), sex (RR 3.14), cyclin D1 (RR 2.29), E-cadherin (RR 0.26) and cell regrowth capability (RR 1.94). Logistic regression analysis revealed that the risk factors of haematogenous recurrence were pN (odds ratio (OR) 8.97), cyclin D1 (OR 4.52) and EGFR (OR 0.18). On the other hand, the risk factor of lymph node recurrence was pN (OR 5.16). With regard to the effect of postoperative treatment, post-operative radiotherapy was a favourable risk factor (RR 0.43) and reduced the haematogenous recurrence (OR 0.18). Our data indicate that combination analysis using pN, sex, cyclin D1, E-cadherin, EGFR and cell regrowth capability may be useful for the prediction of patient survival and recurrence.

Flow-cytometric DNA content analysis of oesophageal carcinoma. Comparison between tumour and sequential non-tumour mucosae

The DNA content in oesophageal carcinoma and in sequential non-tumour mucosa was evaluated in 35 patients with oesophageal carcinoma, to explore the hypotheses that DNA distribution pattern and S-phase fraction can reflect malignant potential and that DNA aneuploidy can provide an early-warning signal of developing cancer. DNA flow cytometry was performed on 129 specimens from the tumours and on 119 specimens from non-tumour mucosa. Control specimens from gastric fundus had normal diploid DNA content and low S-phase fraction. Aneuploidy was found in 94.3% of the carcinoma specimens and intratumoral heterogeneity in 54.3%. Of the non-tumour specimens, 43.7% showed aneuploidy and none multiple aneuploidy. Pattern III distribution was present in 8.6% of the tumour specimens but not in non-tumour mucosa, where the incidence of aneuploidy rose with closeness to the tumour (p < 0.001). S-phase fraction was smaller in non-tumour than in tumour specimens (p < 0.0001). The study indicated that histologically tumour-free oesophageal mucosa may have a high malignant potential in patients with oesophageal carcinoma. The relative instability of such mucosa, with aneuploid cells and low S-phase fraction, may facilitate transition to abnormally proliferating cells in response to environmental signals. Cigarette smoking and alcohol may increase the risk of multicentric cancer development.

Genetic alterations in patients with esophageal cancer with short- and long-term survival rates after curative esophagectomy

OBJECTIVE

The objective of this study was to ascertain the exact relation between specific oncogenes and long- and short-term survival rates in patients with esophageal cancer.

SUMMARY BACKGROUND DATA

Recent developments in molecular biology have shown that several oncogenes and suppressor genes are involved in the development of esophageal cancer. However, the role of these genes still is unknown.

METHODS

The clinical outcome of 84 cases of R0-resected esophageal carcinomas (from 1986-1993) and the molecular and biologic characteristics of these tumors were studied. The patients studied were divided into three groups, which were designated as follows: shortest term survivors (up to 6 months), short-term survivors (7-12 months), and long-term survivors (>5 years). These groups included 23, 17, and 44 subjects, respectively. For the genomic analysis, CyclinD1, int-2, murine double minute 2 (MDM2), retinoblastoma, p53, adenomatous polyposis coli (APC), deleted in colorectal carcinoma (DCC), and human papillomavirus were studied in these patients. The regrowth capability of primary cultures and the clinicopathologic characteristics of these patients also were analyzed.

RESULTS

The CyclinD1 and int-2 genes, which are located in the 11q13 chromosome, and the MDM2 gene were related to short survival. However, the p53 mutation and human papillomavirus infection were not related to short-term survival. The average ratio of genomic abnormalities to genes examined was higher in the shortest and short-term survival groups than in the long-term survival group. Regrowth capability in primary cultures also was related to short-term survival. Among the long-term survival patients, 7 (16%) of 44 cases suffered further cancer after esophagectomy.

CONCLUSIONS

These results suggest that the 11q13 amplicon and MDM2 may play an important role in the progression of esophageal cancer, and an accumulation of genomic abnormalities may result in poor prognosis. Careful follow-up testing for double cancer is needed in long-term survivors of esophageal cancer.

Study of tumour ploidy in early stages of buccal mucosa cancer

The purpose of this study was to determine whether a tumour's DNA content is a prognostic factor in screening out the biologically aggressive varieties of early buccal mucosa cancer. Seventy-eight cases of early squamous cell carcinoma of the buccal mucosa were studied, including 73 with aneuploid and diploid tumours. T1 and T2 tumours, pathological differentiation, vascular and perineural invasion, and the recurrence and disease-free survival rate in relation to aneuploid and diploid content were ascertained. The recurrence rate in aneuploid tumours is 72%, whereas in diploid tumours it is 6% (P<0.001). A Cox regression analysis demonstrated that tumour ploidy was a prognostic factor in disease-free survival, independent of other clinico-pathological characteristics examined. Aneuploidy is the most accurate predictor of biological aggressiveness of cancer of the buccal mucose. Aneuploid early buccal mucosa cancers should be treated by multimodal therapy to achieve a cure.

Flow cytometric analysis of DNA heterogeneity in superficial carcinoma of the esophagus

BACKGROUND

There are few studies of flow cytometric analysis for DNA heterogeneity of patients with superficial carcinoma of the esophagus limited to the epithelium or superficially invading the lamina propria or submucosa.

METHODS

Flow cytometric analysis of cellular DNA content was performed on superficial carcinomas of the esophagus using paraffin embedded blocks of the surgically resected specimens from 56 patients. To evaluate the intratumoral DNA heterogeneity, a total of 141 samples of the 56 tumors were analyzed, depending upon the tumor size.

RESULTS

One or two of the samples was available from 18 of 19 patients with tumors 2 cm or less in greatest dimension, whereas more than three of the samples were available from 22 of 37 patients with tumors 2.1 cm or greater in dimension (P < 0.003). Of 56 tumors, 40 (71.4%) exhibited DNA aneuploidy; DNA heterogeneity was found in 26 tumors (46.4%). The remaining 16 tumors exhibited DNA diploidy. Two of the five tumors that were limited to the epithelium had DNA heterogeneity. The mean dimension of the tumors with DNA heterogeneity was significantly greater (5.8 +/- 2.8 cm) than those exhibiting DNA diploidy (2.3 +/- 1.1 cm) and DNA aneuploidy without heterogeneity (2.9 +/- 2.4 cm). Recurrences after esophagectomy were detected in 6 of the 56 patients; the DNA ploidy pattern of these six patients exhibited DNA heterogeneity.

CONCLUSION

The incidence of DNA heterogeneity increases as tumor size increases and is associated with an increased risk of tumor recurrence after esophagectomy in patients with superficial carcinoma of the esophagus.

Esophageal squamous cell carcinoma: pathology and prognosis

Between 1985 and 1992 a total of 403 patients with resected thoracic esophageal squamous cell carcinoma were evaluated histopathologically, and various pathologic findings related to survival were examined. Concerning depth of tumor invasion, 8 (2%) cases were pTis, 110 (27%) were pT1, 48 (12%) were pT2, 202 (50%) were pT3, and 35 (9%) were pT4. Lymphatic invasion was detected in 299 cases (74%), blood vessel invasion in 200 cases (49%), intramural metastasis in 45 (11%), and lymph node metastasis in 232 (58%). In pT1 carcinoma cases, 4% of mucosal carcinomas and 30% of submucosal carcinomas had lymph node metastasis. Tumors with deeper invasion had a higher incidence of lymph node metastasis: 74% of pT3 carcinomas and 83% of pT4 carcinomas. The sites of lymph node metastasis were divided into mediastinal, cervical, and abdominal fields; and rates of lymph node metastasis were 49%, 14%, and 41%, respectively. In all resected cases, the operative mortality rate was 3.2%, and the overall 5-year survival rate was 44.8%. The 5-year survival rate of patients with curative resection (R0 and R1) was 49.5%, whereas patients with palliative resection (R2) did not survive more than 3 years. There was no significant difference in survival relative to tumor location. In curatively resected cases, the significant prognostic factors by multivariate analysis were pT category, vascular invasion, lymph node metastasis, and intramural metastasis. Prognosis of lymph node-positive cases did not depend on the positive node site. Patients with only one positive node had a better prognosis, and those with six or more positive nodes had a poor prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA or cell kinetics flow cytometry analysis of 33 small gastrointestinal cancers treated by photodynamic therapy

BACKGROUND

Photodynamic therapy (PDT) mediated by hematoporphyrin derivative (HPD) is a new treatment for cancers of small volume undergoing Phase II or III clinical trials in various medical fields. However, there is a lack of prognostic criteria of efficacy as in other cancer treatment.

METHODS

Cell DNA content or cell kinetics throughout the cell cycle were analyzed by flow cytometry and propidium iodide staining before and after HPD-PDT in 33 patients with Tis or T1 cancers of the gastrointestinal tract. The authors compared results in near-diploid cancers with those obtained in normal corresponding tissue.

RESULTS

Complete local tumor destruction and negative histologic findings (complete response [CR]) were observed in 17 of 33 patients during a period averaging 15.7 months. Flow cytometry DNA analysis was feasible in 32 patients. Aneuploidy, found in 15 of the 32 indicated a poor prognosis because 5 of 15 patients with aneuploid tumors were classified as having CR, compared with 12 of 17 patients with near-diploid tumors (P < 0.05). Changes in ploidy after PDT in 11 patients consisted of a reduction in the number of aneuploid peaks in 8 patients and the appearance of one aneuploid peak in 3 patients. Percentages of cells in SG2M phase in near-diploid tumors differed from those observed in control subjects for adenocarcinomas, and there was no significant decrease after HPD-PDT. There was no correlation between the decrease of SG2M cells and the response to HPD-PDT.

CONCLUSION

Results obtained with PDT in this series of patients confirm previously published findings. Changes occurring in the ploidy of PDT-treated patients demonstrate that PDT acts directly on cancer cells in humans and not only on tumor vasculature. However, response to PDT varies from one cell population to another. The appearance of aneuploid populations after PDT suggests that destruction of sensitive cell populations allows the growth of aneuploid clones that initially are not detectable by flow cytometry.

DNA stem line heterogeneity in esophageal cancer accurately identified by flow cytometric analysis

BACKGROUND

This study was designed to evaluate the importance of DNA stem line heterogeneity in determining the malignant potential of esophageal cancer.

METHODS

Flow cytometric analysis of intratumor heterogeneity of DNA contents was performed on step-sectioned slices of 57 resected esophageal carcinomas.

RESULTS

DNA stem line heterogeneity, as assessed by DNA content measurements, was present in 25 (44%) tumors; 6 (11%) were a combination of diploid and aneuploid DNA pattern, and 19 (33%) had two or more aneuploid peaks with different DNA contents (multiploid). Of the remaining 32 homogeneous tumors, 4 showed only a diploid DNA pattern in all samples examined, whereas 28 tumors had only the aneuploid pattern. Tumors with the heterogeneous DNA pattern had a significantly higher frequency of lymph node metastasis than did those with the homogeneous DNA pattern (P < 0.05).

CONCLUSIONS

For evaluation of the highly malignant potential of esophageal carcinoma by nuclear DNA contents, it is important to identify accurately intratumoral heterogeneity. Because different DNA stem lines were evident in different areas of the lesion, evaluation of multiple specimens from a wide area of each lesion is needed to determine with accuracy the degree of intratumor DNA stem line heterogeneity.

Flow cytometric DNA analysis does not predict the radiochemoresponsiveness of esophageal cancer

The relationship between the DNA pattern and the responsiveness to chemotherapy or chemoradiotherapy has been evaluated in 30 patients with squamous cell carcinoma of the esophagus. In 24 patients polychemotherapy with cisplatin (100 mg/m2 on day 1) and 5-fluorouracil (1,000 mg/m2/24 h, continuous infusion of 120 h) every 3 weeks, was performed. Six other patients received chemoradiotherapy with cisplatin 80 mg/m2 on day 1 and 18.5 Gy (split course). Before treatment, at least three endoscopic biopsies were taken from each tumor and frozen at -85 degrees C. Five patients were excluded from the evaluation, three because of interrupted treatment and two due to unsuitable biopsy material obtained endoscopically. The response rate to the cytoreductive treatment was 40% (10/25). DNA content was analyzed with flow cytometry. Out of 25 evaluable patients, a diploid and aneuploid tumor was present in 8 (32.0%) and 17 (68.0%) patients, respectively. According to the DNA pattern, a major response was observed in 4 of 8 patients with a diploid tumor and in 6 of 17 patients with an aneuploid tumor (P = 0.5). No relationship between the percentage of cells in the S-phase and the response to the cytoreductive treatment was evident. Although a slightly higher percentage of major responses was found in euploid tumors, there is no evidence that flow-cytometric DNA analysis can be helpful in the selection of patients for chemotherapy or chemoradiotherapy.

Prognostic value of DNA ploidy in squamous cell carcinoma of esophagus. Analyzed with improved flow cytometric measurement

BACKGROUND

The prognostic value of flow cytometric DNA analysis on paraffin-embedded tumor samples has been controversial in esophageal cancer. To clarify its true significance, the authors developed an improved method that excludes the possibility of contamination by lymphocytes in tumor sample.

METHODS

Single nuclear suspension was prepared from paraffin-embedded samples on 103 patients with squamous cell carcinoma of the esophagus. Both DNA content and nuclear size were simultaneously measured by flow cytometry on 30,000 nuclei, and contaminated lymphocyte nuclei were eliminated from the data by optimal gating. Correlation between DNA ploidy and postoperative survival was examined.

RESULTS

Analysis using a flow cytometric cell sorter showed that the frequency of tumor cells in the lymphocyte-reducing gating fraction (LGF) was significantly higher than that in the conventional nongating fraction (NGF). LGF analysis showed aneuploid peaks in 58 patients (56.3%), but NGF analysis showed aneuploid peaks in only 38 patients. LGF analysis revealed that the aneuploid tumors had higher histologic grading (P < 0.05) and worse survival rate (P < 0.01) compared with diploid tumors. However, conventional methods could not detect this difference.

CONCLUSIONS

Flow cytometric analysis gating by nuclear size may be helpful to detect aneuploid peaks, and for predicting prognosis of patients with squamous cell carcinoma of esophagus.

Influence of preoperative radiotherapy on DNA ploidy in squamous cell carcinomas of the oesophagus

The influence of preoperative radiotherapy on the prevalence of DNA aneuploidy and the prognostic significance of tumour DNA ploidy was evaluated in 126 patients with squamous cell carcinoma of the oesophagus. Preoperative radiotherapy with 30 Gy was performed in 52 patients. DNA ploidy was analysed by flow cytometry on nuclei isolated from paraffin embedded tumour tissue. DNA aneuploidy was identified in 75 tumours (61%) and found to correlate significantly with tumour stage. The percentage of aneuploid carcinomas was significantly reduced by preoperative radiotherapy (surgery only group, 71%; radiotherapy group, 47%, p = 0.01). Although the median survival time was slightly better in the diploid than in the aneuploid group (11.3 and 8.0 months respectively), this difference was not statistically significant. A curative tumour resection was the most important prognostic factor. Preoperative radiotherapy did not prolong survival in oesophageal cancer.

Prognostic significance of cell culture in carcinoma of the oesophagus

The prognostic significance of the potential of cells to grow in tissue culture was studied in 50 patients with oesophageal cancer. The ability of cell lines to grow from resected oesophageal specimens was determined; from 50 patients, 21 cell lines were established (42 per cent). The patients were divided into two groups on this basis: group 1, from whom cancer cells could be grown as continuous cell lines and group 2, from whom cell lines could not be established. The cumulative survival rate of patients in group 1 was significantly lower than that of those in group 2 (P < 0.05). There was also a significantly higher incidence of lymph node metastases in group 1 (P < 0.05). These results suggest that the potential of cancer cells for growth is a useful long-term prognostic indicator for patients with oesophageal carcinoma.

Comparison of pepsin and trypsin digestion on paraffin-embedded tissue preparation for DNA flow cytometry

Preparation with enzymes plays an important part in obtaining good results in cellular DNA content measurements from paraffin-embedded tissue using flow cytometry. Therefore, we have compared two groups of DNA histograms obtained with pepsin (Hedley method) and trypsin digestion (Schutte method). Samples of five tumor types were compared: eight lung, seven breast, five thyroid, seven stomach, and six colon cancer cases. All samples were stained with propidium iodide (PI). The incidence of DNA aneuploidy determined by the Schutte method indicated a higher ratio in four tumor types than that determined by the Hedley method. Concerning the coefficient of variation (CV) used to estimate the quality of the DNA histogram, the diploid G1 peak determined by the Schutte method produced a smaller CV in five tumor types than did the Hedley method. This Schutte method had especially good results in lung and thyroid cancer. Furthermore, the amount of debris (background) determined by the Schutte method indicated a decrease in four tumor types compared with the Hedley method. In cell-cycle analysis of ten DNA diploid cases, DNA histograms by the Hedley method showed an increased S-phase fraction due to an overlapping of debris and aggregated cells. These results indicate that preparation by trypsin digestion is a method superior to pepsin digestion when the sample from paraffin-embedded tissue is stained with PI for the purpose of DNA content measurement.

A flow cytometric analysis of DNA content in primary and metastatic lesions of esophageal squamous cell carcinoma

BACKGROUND

DNA content of malignant tumors has been considered a significant prognostic factor, but intratumor variations in DNA content and differences in DNA content between primary and metastatic lesions have been found in various tumors.

METHODS

DNA indexes of multiple samples obtained from different sites in each tumor were determined by flow cytometry (FCM) in 27 esophageal squamous cell carcinomas.

RESULTS

Intratumor variation in DNA indexes in primary lesions was found in 10 (37%) of the 27 specimens. Of the rest, all DNA indexes were diploid in 5 and all identically aneuploid in 12 samples. A DNA index differing from that of the metastatic lesion was found in four (50%) of eight primary lesions; however, a component of the DNA index identical to that of metastatic lesion was found in seven (88%) of eight primary lesions.

CONCLUSIONS

Recurrence after a "curative" operation was frequent in patients with a tumor that had an aneuploid DNA index, with or without a variation in DNA indexes. There was no recurrence in the five patients with tumors that had only a diploid DNA index. These results suggest that differences in DNA content between primary and metastatic lesions reflect intratumor variation in DNA content in the primary lesions. The presence of a tumor cell population with an aneuploid DNA content, even when the DNA content varied in the primary lesion, may indicate an aggressive clinical course in patients with esophageal squamous cell carcinoma.

Clinical application of flow cytometry for DNA analysis of solid tumors

Recent developments of flow cytometry (FCM) technology which make multiple correlative biological measurements on normal and neoplastic cells is affecting areas of diagnostic pathology as well as research fields, and a general understanding of FCM techniques is essential for pathologists. Today, FCM DNA measurements of tumors also becomes routine in the clinical and/or pathological laboratory for aid in cancer diagnosis and cancer treatment. It can also contribute to diagnosis of tumors as a supplemental method to conventional histopathology, and DNA ploidy and the percentage of S-phase fraction are considered as complementary prognostic parameters independent of the stage of disease. This article reviews clinical applications of flow cytometry focusing on the DNA measurements of solid tumors, and related practical issues, such as the methodology for nuclear DNA measurement, interpretation of DNA histograms and the relationship of DNA ploidy and S-phase fraction to clinical and pathological features of human solid tumors.

Intratumoral heterogeneity in DNA ploidy of esophageal squamous cell carcinomas

Intratumoral heterogeneity in DNA ploidy was investigated in 23 cases of squamous cell carcinoma of the esophagus. Nuclear DNA content was determined for multiple samples taken from the same tumor, using a flow cytometric technique. The incidence of DNA aneuploidy was 87% in this series, and DNA indices ranged from 0.78 to 2.64 but most of them fell within values between 1 and 2. Of these cases ten (43.5%) showed intratumoral heterogeneity in DNA ploidy; in addition to a diploid population, one to four heterogeneous aneuploid subpopulations were discernible in the same tumor. However, morphologic variation was minimal within the same tumor. DNA index seen in metastatic lesions was identical with one of those in the primary lesion. Mechanisms responsible for intratumoral difference in DNA ploidy are also discussed from the aspect of tumor progression.

Three-dimensional DNA image cytometry by confocal scanning laser microscopy in thick tissue blocks

A method for the quantification of nuclear DNA in thick tissue blocks by confocal scanning laser microscopy is presented. Tissues were stained en bloc for DNA by chromomycin A3. Three-dimensional images, 60 microns deep, were obtained by stacking up confocal fluorescent images obtained with an MRC-500 (Bio-Rad, Richmond, CA). The effects due to bleaching and attenuation by depth of fluorescence emission were corrected mathematically. The DNA contents were estimated by summing up the detected emission intensities (discretized into pixel gray levels) from each segmented nucleus. Applications to an adult rat liver and to a human in situ carcinoma of theesophagus are shown to demonstrate, respectively, the precision of the method and its potential usefulness in histopathology. Comparisons are made with DNA histograms obtained on the same materials by image cytometry on smears and by flow cytometry. Ploidy peaks obtained with the confocal method, although wider than with other methods, are well separated. Confocal image cytometry offers the invaluable advantage of preserving the tissue architecture and therefore allowing, for instance, the selection of histological regions and the evaluation of the degree of heterogeneity of a tumor.