Solid tumor preparation for clinical application of flow cytometry

Correlation of Histopathological Variants, Cellular DNA Content, and Clinical Outcome in Adenoid Cystic Carcinoma of the Salivary Glands

OBJECTIVE: To study the correlation between flow cytometrically measured DNA ploidy with prognostically important histopathologic groups and clinical outcome in patients with adenoid cystic carcinoma of the salivary glands.

STUDY DESIGN: 46 tumor specimens were analyzed flow cytometrically for DNA content and assessed for histological grade. Correlations were made between tumor DNA ploidy and histopathological grade, and disease-free and overall survival of these patients.

RESULTS: Of the 46 patients, 31 had a cribiform/tubular histologic pattern, and 15 had a solid pattern. 84% of the tumors with cribriform/tubular pattern were DNA diploid, compared with 33% of tumors that were graded solid. This difference proved to be statistically significant (χ 2 11.75, P = 0.0006). Overall and disease-free survival periods were longer for patients with DNA diploid tumors in both groups, 63% vs. 36% and 62% vs 38%, respectively.

CONCLUSIONS: Tumor DNA ploidy correlates with prognostically important tumor histopathology as well as overall and disease-free survival in patients with adenoid cystic carcinoma of the salivary gland. EBM rating: B-3.

Contribution of multiparameter flow cytometry immunophenotyping to the diagnostic screening and classification of pediatric cancer

Pediatric cancer is a relatively rare and heterogeneous group of hematological and non-hematological malignancies which require multiple procedures for its diagnostic screening and classification. Until now, flow cytometry (FC) has not been systematically applied to the diagnostic work-up of such malignancies, particularly for solid tumors. Here we evaluated a FC panel of markers for the diagnostic screening of pediatric cancer and further classification of pediatric solid tumors. The proposed strategy aims at the differential diagnosis between tumoral vs. reactive samples, and hematological vs. non-hematological malignancies, and the subclassification of solid tumors. In total, 52 samples from 40 patients suspicious of containing tumor cells were analyzed by FC in parallel to conventional diagnostic procedures. The overall concordance rate between both approaches was of 96% (50/52 diagnostic samples), with 100% agreement for all reactive/inflammatory and non-infiltrated samples as well as for those corresponding to solid tumors (n = 35), with only two false negative cases diagnosed with Hodgkin lymphoma and anaplastic lymphoma, respectively. Moreover, clear discrimination between samples infiltrated by hematopoietic vs. non-hematopoietic tumor cells was systematically achieved. Distinct subtypes of solid tumors showed different protein expression profiles, allowing for the differential diagnosis of neuroblastoma (CD56^hi/GD2⁺/CD81^hi), primitive neuroectodermal tumors (CD271^hi/CD99⁺), Wilms tumors (>1 cell population), rhabdomyosarcoma (_nuMYOD1⁺/_numyogenin⁺), carcinomas (CD45⁻/EpCAM⁺), germ cell tumors (CD56⁺/CD45⁻/NG2⁺/CD10⁺) and eventually also hemangiopericytomas (CD45⁻/CD34⁺). In summary, our results show that multiparameter FC provides fast and useful complementary data to routine histopathology for the diagnostic screening and classification of pediatric cancer.

Radioluminescence microscopy: measuring the heterogeneous uptake of radiotracers in single living cells

Radiotracers play an important role in interrogating molecular processes both in vitro and in vivo. However, current methods are limited to measuring average radiotracer uptake in large cell populations and, as a result, lack the ability to quantify cell-to-cell variations. Here we apply a new technique, termed radioluminescence microscopy, to visualize radiotracer uptake in single living cells, in a standard fluorescence microscopy environment. In this technique, live cells are cultured sparsely on a thin scintillator plate and incubated with a radiotracer. Light produced following beta decay is measured using a highly sensitive microscope. Radioluminescence microscopy revealed strong heterogeneity in the uptake of [(18)F]fluoro-deoxyglucose (FDG) in single cells, which was found consistent with fluorescence imaging of a glucose analog. We also verified that dynamic uptake of FDG in single cells followed the standard two-tissue compartmental model. Last, we transfected cells with a fusion PET/fluorescence reporter gene and found that uptake of FHBG (a PET radiotracer for transgene expression) coincided with expression of the fluorescent protein. Together, these results indicate that radioluminescence microscopy can visualize radiotracer uptake with single-cell resolution, which may find a use in the precise characterization of radiotracers.

Cellular DNA content parameters as prognostic indicators in human astrocytomas

OBJECTIVE

Clinical parameters such as grade, size and/or location of the tumor are good predictors of outcome in patients with astrocytoma. The objective of this study was to determine whether DNA content parameters have a prognostic significance for this group of tumors.

METHODS

Following optimization and validation of methodology for evaluating cellular DNA content parameters (CDCP), tumor DNA ploidy and percent S phase fraction (SPF) were determined from 64 patients using formalin fixed, paraffin embedded specimens (mean coefficient of variation=4.94) obtained over a 10-year period. Median survival times correlated with grade (I/II=1154 vs. III/IV=483days, P=0.0317). Fifty-five percent of the specimens contained DNA aneuploid (DNA-A) components (average SPF=18.3%) and 45% were DNA diploid (DNA-D) (average SPF=9.6%). Survival did not correlate with overall differences in DNA ploidy (DNA-D=181 vs. DNA-A=206days, P=0.6314) when treated and untreated tumors were analyzed. However, a trend for prolonged median survival was observed in patients whose tumors were untreated with respect to cytotoxic therapy based on DNA ploidy status (DNA-D=275 vs. DNA-A=15days, P=0.3408). Survival for all patients did not correlate with median SPF (<13.5% av.=121 vs. >13.5% av.=154days, P=0.6534).

CONCLUSION

DNA content parameters may correlate with the natural history and treatment outcome of newly diagnosed untreated patients with astrocytomas.

Comparison of DNA content parameters in paired, fresh tissue pretreatment biopsies and surgical resections from squamous cell carcinoma of the head and neck

OBJECTIVE

Cellular DNA characteristics derived from pretreatment biopsy (PTB) may become important for predicting treatment outcomes in patients with head and neck squamous cell cancer (HNSCC). Whether the PTB adequately represents the whole specimen is of critical importance.

STUDY DESIGN

In a series of >700 HNSCCs, we identified 59 cases in which the PTB and the surgical resection (SR) met the following criteria: PTB and SR were from the same site, and SR was obtained within 5 weeks of PTB with no intervening treatments.

RESULTS

Twenty-nine percent of the PTB specimens were DNA diploid. Only 1 of the 11 subsequent DNA diploid SR was associated with a DNA aneuploid PTB (91% concordance). Of the 48 DNA aneuploid tumors, 3 were associated with DNA diploid PTB (94% concordance). Three other DNA aneuploid SRs were associated with PTB of poor quality.

CONCLUSION

With respect to DNA ploidy, PTB are representative of SR specimens.

Enrichment of tumor cells for cell kinetic analysis in human tumor biopsies using cytokeratin gating

PURPOSE

To determine the feasibility of using cytokeratin antibodies to distinguish normal and malignant cells in human tumors using flow cytometry. The goal was ultimately to increase the accuracy of cell kinetic measurements on human tumor biopsies.

MATERIAL AND METHODS

A panel of four antibodies was screened on a series of 48 tumors from two centres; 22 head and neck tumors (Amsterdam) and 26 esophagus carcinomas (Leuven). First, screening was carried out by immunohistochemistry on frozen sections to test intensity of staining and the fraction of cytokeratin-positive tumor cells. The antibody showing the most positive staining was then used for flow cytometry on the same tumor.

RESULTS

The two broadest spectrum antibodies (AE1/AE3, E3/C4) showed overall the best results with immunohistochemical staining, being positive in over 95% of tumors. Good cell suspensions for DNA flow cytometry could be made from frozen material by a mechanical method, whereas enzymatic methods with trypsin or collagenase were judged failures in almost all cases. From fresh material, both collagenase and trypsin produced good suspensions for flow cytometry, although the fraction of tumor cells, judged by proportion aneuploid cells, was markedly higher for trypsin. Using the best cytokeratin antibody for each tumor, two parameter flow cytometry was done (cytokeratin versus DNA content). Enrichment of tumor cells was then tested by measuring the fraction of aneuploid cells (the presumed malignant population) of cytokeratin-positive cells versus all cells. An enrichment factor ranging between 0 (no enrichment) and 1 (perfect enrichment, tumor cells only) was then calculated. The average enrichment was 0.60 for head and neck tumors and 0.59 for esophagus tumors.

CONCLUSIONS

We conclude that this method can substantially enrich the proportion of tumor cells in biopsies from carcinomas. Application of this method could significantly enhance accuracy of tumor cell kinetic measurements.

The clinical application of DNA content and kinetic parameters in the treatment of patients with squamous cell carcinomas of the head and neck

Patients with squamous cell cancers of the head and neck (SCCHN) vary tremendously in their natural history and treatment outcome even amongst subgroups where the clinical and morphological parameters are similar. The ability to pretherapeutically identify individual patients and patient subgroups that differ in these regards would greatly facilitate clinical and basic science cancer research in this tumor. DNA content parameters are simple and accurate intermediate markers of a tumor's biology and reflect the fundamental process associated with the development of malignancy, chromosomal aneuploidy. In patients with SCCHN, DNA content parameters have been shown to be highly predictive of the natural history of the tumor and treatment outcome. They are also useful as intermediate markers for the study of the underlying molecular-genetic properties and processes responsible for the biological differences seen in these cancers. DNA content parameters therefore serve as fundamental 'translational' bridges in clinical and laboratory research in patients with SCCHN.

Prognostic value of clinicopathological parameters in head and neck squamous cell carcinoma: a prospective analysis

The prognostic weight of histological and biological factors was compared with that of known clinical prognostic factors in a population of 108 consecutive previously untreated patients with head and neck squamous cell carcinoma. Parameters studied were: tumour vascularisation, mitotic index, histological differentiation, nuclear grade, keratinisation, desmoplasia, growth pattern, inflammation, tumour emboli in peripheral vessels, keratins 6, 13, 19 immunohistochemical expression, cytofluorometric ploidy and S-phase. In multivariate analysis (Cox), only age and nodal status had a significant impact on the overall survival, whereas T stage was the only significant factor associated with locoregional failure. The cumulative incidence of metastases was correlated not only with age, T and N stage, but also with histological differentiation. All the other histological and biological factors studied failed to provide further prognostic information. These findings may help to select patients with high metastatic risk.

Tumor vascularization, mitotic index, histopathologic grade, and DNA ploidy in the assessment of 114 head and neck squamous cell carcinomas

BACKGROUND

Quantification of tumor vascularization recently has been shown to a parameter of potential clinical significance. Several basic and clinical studies have demonstrated that tumor growth correlates significantly with angiogenesis.

METHODS

To determine the utility of quantification of tumor vascularization and mitotic index for the pathobiologic assessment of head and neck squamous cell carcinoma, a prospective study of 114 consecutively recruited primary neoplasms was performed. Tumors were also studied for differentiation, keratinization, nuclear atypia, growth pattern, inflammation, desmoplasia, vascular tumor emboli, and DNA content.

RESULTS

In this cohort, tumor vascularization was correlated with mitotic index (P < 0.001), nuclear grade (P = 0.03), presence of tumor emboli in the peripheral microvessels (P = 0.05), and lymph nodal status (P = 0.03). A strong relationship between poor differentiation and high N classification (P < 0.001), differentiation and keratinization (P < 0.001) and tumor cell emboli and clinically involved lymph nodes (P = 0.01) was also observed. Emboli were more rare in laryngeal and oropharynx/oral cavity tumors than in hypopharynx/epilarynx (P = 0.02).

CONCLUSIONS

This study indicates that tumor vascularization, differentiation, and tumor emboli in peripheral microvessel network are important histologic parameters in the assessment of squamous cell carcinoma of the head and neck.

Variations in DNA aneuploid cell content during tumor dissociation in human colon and head and neck cancers analyzed by flow cytometry

Experimental research involving human solid tumors often requires single cell suspensions of high yield that are representative of the tissue of origin and in which the cellular property of interest is preserved. This is particularly necessary for the determination of DNA ploidy by flow cytometry. Mechanical dissaggregation and proteolytic enzyme digestion are the most commonly employed dissociation techniques for solid tumors. Comparative testing of techniques is often not performed. Mechanical and proteolytic enzyme dissociation techniques were comparatively tested in 77 human squamous cell cancers of the head and neck (SCCHN) and 25 human colon cancers for cellular yield, dye exclusion viability, quality, and morphology of DNA histograms, and the presence and proportion of DNA aneuploid subpopulations. Significant and consistent DNA aneuploid subpopulation losses were noted in mechanical preparations of SCCHN and enzymatic preparations of colon cancers. The frequency of SCCHN specimens with DNA aneuploid subpopulations was underestimated by 52% in mechanical cell suspensions, and the proportion of DNA aneuploid cells was diminished in an additional 30% of the specimens. Conversely, the frequency of specimens with DNA aneuploid subpopulations was underestimated by 38% in cell suspensions from enzymatically dissociated human colon cancer and their proportion diminished in an additional 50% of the specimens. Incubations of human colon cancers with three commonly employed proteolytic enzymes demonstrated a progressive loss of DNA aneuploid subpopulations as a function of enzyme concentration and incubation time. This is a serious potential source of error in the flow cytometric determination of DNA ploidy in human solid tumors, and may contribute to the diversity of results obtained and occasional contradictory conclusions reached in such studies.

DNA image cytometry of keratoacanthoma and squamous cell carcinoma

The distinction between the keratoacanthoma (KA) and the squamous cell carcinoma (SCC) can sometimes be difficult on the basis of histologic and clinical criteria. The possible diagnostic significance of DNA ploidy initiated the present study evaluating the DNA ploidy in paraffin-embedded tissue sections of 7 KA and 15 SCC, and fresh frozen tissue touch preparations of 15 of the same cases using the CAS 200 Image Analyzer. In paraffin-embedded tissue sections the main peak DNA index was based on normal epidermis, and ranged from 1.03 to 1.59 in KA and from 1.47-2.71 in SCC. The DNA Index (DI) discriminated KA from SCC in 17 of 22 cases (p less than 0.0007). The highest DNA content of single nuclei ranged from 9.0-18.0 picograms (pg) (DI 2.9-6.03) in KA and 14.8-38.6 pg (DI 4.0-11.03) in SCC. The highest DNA content discriminated KA from SCC in 16 of 22 cases (p less than 0.003). In fresh frozen tissue touch preparations from 15 of the same lesions, there was considerable overlap in DNA indices of KA (0.534-1.39) and SCC (0.464-1.41). Abnormal DNA peaks seen in histograms from three SCC in paraffin-embedded tissue sections were lost in the touch preparation histograms, probably due to inadequate sampling. Therefore, image analysis of paraffin-embedded tissue sections is better able to distinguish KA from SCC than touch preparations.

Tissue preparation for simultaneous flow cytometric quantitation of tumour associated antigens and DNA in solid tumours

A multiparameter flow cytometric assay for the simultaneous study of tumour associated antigens (TAA) and DNA in fresh solid tumours was devised. Cell suspensions were prepared by disaggregating unfixed solid tumour samples mechanically over a stainless steel mesh. Indirect immunofluorescence was used to identify the TAA, and DNA was stained with propidium iodide. Cell morphology was well preserved, cell clumping was negligible, and high quality indirect immunofluorescence quality indirect immunofluorescence and DNA staining were obtained. The technique is simple, rapid, and reproducible. Multiparameter assays can be developed to study prognostic indicators such as membrane oncoproteins, receptors, and multidrug resistance in solid tumours. With a suitable panel of antibodies the technique might become an aid in the differential diagnosis and biochemical diagnosis of some solid tumours.

DNA cytometry of musculoskeletal tumors. A review

In conclusion, all the benign soft tissue tumors analyzed so far have been been diploid, whereas the malignant entities include both diploid or aneuploid variants. Further, there is a relationship between ploidy level and histologic malignancy grade. The main value of DNA analysis seems to be that it provides objective support for histologic diagnosis as to benignity and malignancy grade. Occasionally, a discrepancy between ploidy and grade is encountered. Apart from the fact that aneuploidy precludes benignity, it may prove that ploidy level in malignancy is a better predictor of clinical course than histologic grade. However, this can only be established by analyzing each malignant entity separately, because the validity of DNA cytometry probably varies with histogenetic tumor type.

Flow cytometric measurements of DNA and other cell components in human tumors: a critical appraisal

Fundamental principles of flow cytometry with emphasis on DNA measurements and cell cycle analysis in human cells and tissues are summarized. Some of the pitfalls of cell preparation techniques and histogram interpretation are discussed at length. While consensus has been reached for some organs and tumors that DNA quantitation by flow cytometry (or image cytometry) may be of prognostic value, for most cancers studied to date the information remains incomplete. Thoroughly lacking are well-structured prospective studies because retrospective studies, while suggestive, may not necessarily be of the same value. Potential usefulness of other tumor markers is briefly discussed. Many fundamental questions concerning definitions of "diploid" and "aneuploid" tumors have not been satisfactorily settled. While the goal of "objective measurements" is worthy of further pursuit, the interpretation of results is often highly subjective. The biologic reasons for behavioral differences between diploid and aneuploid tumors are still totally obscure.

Flow cytometric analysis of benign and malignant tumors of the oral and maxillofacial region

One hundred eight fresh tissue samples obtained from normal tissues, benign tumors, and malignant tumors of the oral and maxillofacial region were analyzed for nuclear DNA content and cell kinetics by flow cytometric analysis (FCM). Mean DNA indices for 22 normal tissues and 18 benign tumors were 1.00 and 1.02, respectively, and all samples but one showed diploid pattern. On the other hand, the value for 68 malignant tumors was 1.38, and 66% of them showed an aneuploid pattern. The S phase and G2 + M phase cell populations for malignant tumors were 17.2% and 7.0%, respectively. With the exception of G2 + M phase cell population, all values for malignant tumors were significantly higher than those of normal tissue and benign tumors. Although statistical differences were not observed in most of the values, they were higher in squamous cell carcinomas than in malignant salivary gland tumors. The incidence of aneuploidy and DNA index showed a tendency to increase with the increase of T classification, in N2 and N3 tumors, and in the group of patients with recurrence or who died. The DNA index and the type of DNA ploidy were well correlated to malignancy grade determined by six histologic parameters, whereas the S phase cell population was correlated to mitosis. The analysis by the two-dimensional diagnostic supporting system showed that more than 80% of malignant tumors can be correctly diagnosed by combined values of DNA index and S phase cell population. The results indicate that nuclear DNA analysis by FCM is quite useful as a supplement to histologic diagnosis and evaluation of malignancy grade.

Cellular DNA content parameters in untreated and recurrent squamous cell cancers of the head and neck

The presence and degree of DNA aneuploidy as measured by the DNA index (DI) and the S phase fraction (SPF) were determined by flow cytometry in 294 specimens from 237 patients with untreated and recurrent squamous cell carcinomas of the head and neck (SCCHN). A descriptive analysis was performed in which the specimen DNA parameters were correlated with stage, size of primary, degree of lymph node involvement, morphological grade, and treatment status of the corresponding patients. Approximately 70% of the previously untreated specimens contained DNA aneuploid populations (DI greater than 1.10) and three quarters had SPF that were above 15%. There was a strong, direct association between DI and SPF (P less than 0.001). There was no correlation of the presence or degree of DNA aneuploidy with the stage of the tumor or the size of the primary or conventional morphological grade of the tumor. Specimens from patients with recurrent tumors and untreated patients with N3 lymph nodes had significantly lower rates of DNA aneuploidy and mean DI. Serial determinations of DNA aneuploidy in patients with SCCHN undergoing cytotoxic therapy are ongoing and may prove useful in the identification and understanding of resistance and response in this tumor.

Comparative analysis of different approaches to investigate cell kinetics

The potential of different methods to investigate proliferative activity of cell populations was analysed for non-Hodgkin's lymphomas. Cells in S phase and all cycling cells were determined on cell suspensions obtained from fresh lymph node material by [3H]-thymidine autoradiography [( 3H]TdR LI), a monoclonal antibody to bromodeoxyuridine (BrdU LI), and the monoclonal antibody Ki67. A good correlation was observed between the values of [3H]TdR LI and BrdU LI (rs = 0.90; P less than 0.01), [3H]TdR LI and S phase (rs = 0.62; P less than 0.01) and [3H]TdR LI and Ki67 (rs = 0.64; P less than 0.01) in individual lymphomas. Using the median values obtained from the different approaches as cut-off points to define slowly and rapidly proliferating tumours, the best agreement was observed between [3H]TdR LI and BrdU LI (91%) and poorer agreements, even though statistically significant, were observed between [3H]TdR LI and S phase (73%) or Ki67 (76%). In conclusion, the kinetic information derived from different approaches was more or less concordant and newly proposed approaches should be directly and carefully verified for their prognostic relevance before using them as alternatives to conventional methods.