IRF-1 responsiveness to IFN-γ predicts different cancer immune phenotypes

BACKGROUND

Several lines of evidence suggest a dichotomy between immune active and quiescent cancers, with the former associated with a good prognostic phenotype and better responsiveness to immunotherapy. Central to such dichotomy is the master regulator of the acute inflammatory process interferon regulatory factor (IRF)-1. However, it remains unknown whether the responsiveness of IRF-1 to cytokines is able to differentiate cancer immune phenotypes.

METHODS

IRF-1 activation was measured in 15 melanoma cell lines at basal level and after treatment with IFN-γ, TNF-α and a combination of both. Microarray analysis was used to compare transcriptional patterns between cell lines characterised by high or low IRF-1 activation.

RESULTS

We observed a strong positive correlation between IRF-1 activation at basal level and after IFN-γ and TNF-α treatment. Microarray demonstrated that three cell lines with low and three with high IRF-1 inducible translocation scores differed in the expression of 597 transcripts. Functional interpretation analysis showed mTOR and Wnt/β-cathenin as the top downregulated pathways in the cell lines with low inducible IRF-1 activation, suggesting that a low IRF-1 inducibility recapitulates a cancer phenotype already described in literature characterised by poor prognosis.

CONCLUSION

Our findings support the central role of IRF-1 in influencing different tumour phenotypes.

Laser scanning cytometry evaluation of MART-1, gp100, and HLA-A2 expression in melanoma metastases

Assessment of antigen expression by solid tumors has relied predominantly on immunohistochemistry, flow cytometry, and more recently quantitative real-time polymerase chain reaction. However, all these techniques present intrinsic limits. The laser scanning cytometer, by combining the properties of light and fluorescence microscopy with those of laser cytometry, can quantitatively and objectively analyze hypocellular samples such as fine-needle aspirates on an individual cell basis. To validate the fidelity of laser scanning cytometry for quantitative immunophenotyping of fine-needle aspirates, the authors measured the expression of the melanoma-associated antigens MART-1 and gp100 as well as HLA-A2, a HLA class 1 restriction element associated with their recognition by melanoma-specific T cells. Expression of melanoma antigens and HLA was measured by laser scanning cytometry and immunohistochemistry in fine-needle aspirates from melanoma metastases. In addition, transcription levels of both melanoma antigens were recorded by quantitative real-time polymerase chain reaction. A quantity of less than 1,000 cells per sample (average 682 cells) was sufficient for the analysis. Laser scanning cytometry estimates correlated with those of immunohistochemistry and quantitative real-time polymerase chain reaction for MART-1 and gp100. A good correlation in HLA-A2 detection by laser scanning cytometry and immunohistochemistry was also observed. Moreover, the laser scanning cytometer could discriminate subsets of cells from the same lesion with heterogeneous melanoma antigen expression, leading to the observation that cells with a DNA index greater than 2.5 expressed significantly less gp100. Thus, laser scanning cytometry yields detailed information on protein expression in individual cells and represents a new tool for dissecting the immune response in the tumor microenvironment.

Absence of SV-40 large T antigen (Tag) in malignant mesothelioma effusions: an immunocytochemical study

Simian Virus 40 (SV 40) was recently implicated in the pathogenesis of malignant mesothelioma. The oncogenic capacity of SV-40 is a function of a nuclear protein, the large T antigen (Tag). SV-40 Tag DNA sequences are detected by the polymerase chain reaction in 40-80% of malignant mesothelial proliferations. However, the role of immunohistochemistry (IHC) in demonstrating the nuclear localization of Tag is controversial. We sought to determine the clinical utility of SV-40 Tag IHC in pleural effusion cytology as an ancillary tool in the cytologic diagnosis of malignant mesothelioma (MM). Formalin-fixed, paraffin-embedded cell block sections from 100 pleural effusions (32 MMs, 25 benign reactive, 43 metastatic adenocarcinomas) were immunostained for the SV-40 anti-Tag, using two primary monoclonal SV-40 Tag antibodies: clone Pab 416 and clone Pab 101. Despite strong and consistent immunoreactivity in positive controls, no nuclear immunostaining was observed in any case. We believe the small sample size in cytology cell block sections, the low viral copy number in infected cells, and the effect of formalin fixation may have resulted in absence of immunoreactivity. The role of SV-40 Tag IHC in diagnostic cytopathology remains unclear unless further studies reliably show its detection.

Short-term kinetics of tumor antigen expression in response to vaccination

The melanoma patient's immune response to tumor has been extensively studied. Yet, the frequently observed coexistence of tumor-associated Ag (TAA)-specific T cells with their target cells in vivo remains unexplained. Loss of TAA expression might contribute to this paradox. We studied TAA expression in metastases by obtaining fine-needle aspirations from 52 tumor lesions in 30 patients with melanoma before and soon after immunotherapy. Limitations due to low amounts of starting material were overcome with a high fidelity antisense RNA amplification method. TAA expression was measured by quantitative real-time PCR of anti-sense RNA. Decrease in gp100/Pmel-17 TAA preceded tumor disappearance in several instances and could be best explained by immune selection because most patients had received gp100/Pmel-17-specific vaccination. Conversely, immune selection was absent in nonregressing lesions. These observations suggest that vaccination, when successful, triggers a broad inflammatory reaction that can lead to tumor destruction despite immune selection. Additionally, lack of clinical response might be attributed to lack of this initiating event rather than immune escape. This study provides an insight into the natural history of tumors and defines a strategy for the characterization of gene expression in tumors during therapy.

The multidrug-resistant phenotype associated with overexpression of the new ABC half-transporter, MXR (ABCG2)

Mechanisms of drug resistance other than P-glycoprotein are of increasing interest as the list of newly identified members of the ABC transport family has grown. We sought to characterize the phenotype of the newly discovered ABC transporter encoded by the mitoxantrone resistance gene, MXR, also known as ABCP1 or BCRP. The pharmacodynamics of mitoxantrone and 12 other fluorescent drugs were evaluated by confocal microscopy in four multidrug-resistant human colon (S1) and breast (MCF-7) cancer cell lines. We utilized two sublines, MCF-7 AdVp3000 and S1-M1-80, and detected overexpression of MXR by PCR, immunoblot assay and immunohistochemistry. These MXR overexpressing sublines were compared to cell lines with P-glycoprotein- and MRP-mediated resistance. High levels of cross-resistance were observed for mitoxantrone, the anthracyclines, bisantrene and topotecan. Reduced levels of mitoxantrone, daunorubicin, bisantrene, topotecan, rhodamine 123 and prazosin were observed in the two sublines with high MXR expression. Neither the P-glycoprotein substrates vinblastine, paclitaxel, verapamil and calcein-AM, nor the MRP substrate calcein, were extruded from MCF-7 AdVp3000 and S1-M1-80 cells. Thus, the multidrug-resistant phenotype due to MXR expression is overlapping with, but distinct from, that due to P-glycoprotein. Further, cells that overexpress the MXR protein seem to be more resistant to mitoxantrone and topotecan than cells with P-glycoprotein-mediated multidrug resistance. Our studies suggest that the ABC half-transporter, MXR, is a potent, new mechanism for conferring multiple drug resistance. Definition of its mechanism of transport and its role in clinical oncology is required.

Development and characterization of melanoma cell lines established by fine-needle aspiration biopsy: advances in the monitoring of patients with metastatic melanoma

The establishment of melanoma cell lines from fine-needle aspiration biopsies (FNAB) has allowed for an enhanced understanding of the complex interactions that occur between T cells and tumor cells. The technique of FNAB offers the advantage of providing a sequential analysis of the same tumor nodules throughout treatment. The expression of melanoma antigens (MAs) was assessed in fresh melanoma FNAB samples and from tumor cell lines derived from these samples using several different approaches. Cytospin preparations of freshly isolated tumor cell explants were analyzed by immunocytochemistry (ICC), while the daughter cell line was analyzed by fluorescent activated cell sorting (FACS) analysis, and semiquantitative and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR, qRT-PCR). As assessed by these methods, the level of MA expression by the original tumor cell explants correlated with the expression in established in vitro cell lines. Molecular analysis of the established cell lines utilizing PCR technology improved the sensitivity of detection of MA expression. Thus FNAB of melanoma is an efficient and effective method of tissue procurement, capable of generating, sequentially and from the same lesion, fresh tumor cells, tumor infiltrating lymphocytes (TIL), and long-term melanoma cell lines.

Costimulatory markers in muscle of patients with idiopathic inflammatory myopathies and in cultured muscle cells

In an attempt to understand the mechanisms of cell injury in the inflammatory myopathies, we analyzed the expression of costimulatory molecules, CTLA4, CD28, CD86, CD40, and CD154 as well as HLA class I, HLA class II, and ICAM-I in normal muscle and in muscle biopsies from patients with polymyositis (PM) or dermatomyositis (DM). By immunohistochemical staining, DM and PM biopsies showed the presence of CTLA4, CD28, CD86, and CD40 on inflammatory cells. More strikingly, however, low levels of CTLA4 and CD28 were observed on muscle cells. The expression of CTLA4 and CD28 on nonlymphoid cells has not been previously reported. These unexpected findings were confirmed in cultured normal human myoblasts: various proinflammatory cytokines induced the expression of CTLA4 and CD28 on normal human muscle cells. The sequences of the cDNAs were found to be identical to the sequences for these molecules in T cells. The data suggest a novel complexity in the network of cellular interactions between the infiltrated immune cells and the muscle cells in which the normal relationship between infiltrating inflammatory cells and target tissue is under a previously unrecognized set of controls.

Immune selection after antigen-specific immunotherapy of melanoma

BACKGROUND

Melanoma antigen (MA)-specific vaccination strongly enhances antitumor reactivity in vivo and is capable of producing strong cytotoxic T lymphocyte responses in vitro. Furthermore, specific human leukocyte antigen-restricted T cell activation is hypothesized to occur in response to peptide-based immunotherapy, which may lead to the preferential killing of tumor cells bearing the relevant MA. The development of melanoma antigen-loss variants may subsequently occur in vivo.

METHODS

Analysis of 532 melanoma lesions from 204 patients was performed on fine-needle aspiration biopsy specimens. Lesions were graded for the expression of the MAs gp100 and MART-1 with use of immunocytochemistry. A total of 351 melanoma lesions were divided into cohorts on the basis of the treatment received. The pretreatment group (n = 175) consisted of lesions obtained before any form of gp100 immunotherapy, with the posttreatment group (n = 176) consisting of lesions obtained after vaccination with a modified gp100 epitope, gp209-2M +/- interleukin 2 (IL-2).

RESULTS

The percentage of lesions not expressing the gp100 antigen is greater than the percentage not expressing MART-1 (26% vs 14%). The frequency of lesions with high expression (> 75%) of gp100 significantly decreased with therapy (47% vs 34%) and conversely negative lesions increased (18% vs 29%). Treatment of lesions with peptide alone (no IL-2) revealed a significant decrease in gp100 expression (47% vs 32%), enhanced with the addition of IL-2 to therapy (47% vs 35%). The expression of MART-1 remained essentially unchanged unless IL-2 was added (54% vs 54%, MART-1 peptide alone, 54% vs 43%, MART-1 peptide + IL-2). Of 94 patients (181 lesions) assessed for gp100 expression before treatment, 10 patients responded to therapy. Pretreatment lesions in responding patients expressed some level of gp100 in all cases compared with 27% of nonresponding lesions, which were negative for gp100 expression. CONCLUSIONS. This study indirectly demonstrates that vaccination with an MA-derived peptide can result in immune selection in vivo. Furthermore, it provides strong immunologic evidence for the specificity of MA vaccines and to the relevance of MA expression in predicting the response to vaccination.

E-cadherin, N-cadherin, and calretinin in pleural effusions: the good, the bad, the worthless

The distinction between reactive mesothelial cells (RMC), malignant mesothelioma (MM), and metastatic adenocarcinoma (ACA) in pleural effusions may be impossible based on morphology alone. E-cadherin, N-cadherin, and calretinin are newly described immunocytochemical markers which can potentially be utilized for facilitating this distinction. E-cadherin and N-cadherin are calcium-dependent intercellular adhesion molecules expressed in epithelial cells and mesenchymal/mesothelial cells, respectively. The differential expression of E-cadherins in epithelial cells and N-cadherins in mesothelial cells has been utilized to differentiate reactive mesothelial cells, MMs and ACAs. Calretinin is a calcium-binding protein within the family of EF-hand proteins. It is abundantly expressed in peripheral and central nervous tissues, and has been shown to consistently immunoreact with mesothelial cells. We studied cell block sections from 77 pleural effusions (22 RMC, 26 MM, and 29 ACA) to investigate the potential immunocytochemical use of anti-E-cadherin, anti-N-cadherin, and anti-calretinin antibodies for differentiating between RMC, MM, and ACA in pleural effusions. A modified avidin-biotin peroxidase complex (ABC) method was used. E-cadherin immunostaining was observed in 14% of RMC, 46% of MMs, and 97% of ACAs. A distinct membrane staining pattern was seen in ACAs. The pattern of staining was cytoplasmic in all reactive RMC and varied from membrane to cytoplasmic in MMs. Anti-N-cadherin immunoreacted with 77% of RMC, 35% of MMs, and 48% of ACAs. Twenty-seven percent of RMC, 58% of MMs, and 31% of ACAs immunoreacted with anti-calretinin. Based on these results, we conclude that anti-E-cadherin is a potentially useful marker in the distinction of ACA cells from RMC. However, it is not as useful for the distinction of ACA and MM. Anti-N-cadherin and anti-calretinin did not reliably distinguish between reactive mesothelial, MM, and ACA cells in pleural effusions.

Immunophenotypic analysis of non-Hodgkin's lymphomas in cytologic specimens: a correlative study of immunocytochemical and flow cytometric techniques

Most Non-Hodgkin's lymphomas(NHL) can be accurately diagnosed and classified based on morphologic and immunophenotypic findings on cytologic specimens. Immunophenotyping can be accomplished via immunocytochemistry (IC) or flow cytometry (FC). We reviewed our experience with 98 cytology specimens (70 fine-needle aspirates [FNA] and 28 effusions) that were submitted for immunophenotyping utilizing both IC and FC between January 1992 and December 1997 for the diagnosis of NHL. Eighty-five percent of the cases were immunophenotyped by both techniques. Among these there were only two discrepancies between IC and FC, yielding a 98% correlation rate. Of the 98 cases, 11% could not be immunophenotyped by FC and 4% could not be immunophenotyped by IC. The advantage of IC is the preservation of cytomorphology, which results in the requirement for a lower number of neoplastic cells and a limited, targeted panel of antibodies. This is especially useful in predominantly necrotic lymphomas in which only a few well-preserved neoplastic cells may be present, rendering the specimen inadequate for immunophenotyping by FC. The advantages of FC are in the detection of a small population of monoclonal cells in a background of reactive cells (particularly useful in effusion samples in which the predominant cell population is often reactive T lymphocytes), increased diagnostic precision through evaluation of objective parameters, and the use of multiple markers with dual labelling. We conclude that IC and FC are both excellent methods for immunophenotyping of cytology specimens and can be used interchangeably depending on the institutional expertise and availability.

E-cadherin, N-cadherin, and calretinin in pleural effusions: the good, the bad, the worthless

The distinction between reactive mesothelial cells (RMC), malignant mesothelioma (MM), and metastatic adenocarcinoma (ACA) in pleural effusions may be impossible based on morphology alone. E-cadherin, N-cadherin, and calretinin are newly described immunocytochemical markers which can potentially be utilized for facilitating this distinction. E-cadherin and N-cadherin are calcium-dependent intercellular adhesion molecules expressed in epithelial cells and mesenchymal/mesothelial cells, respectively. The differential expression of E-cadherins in epithelial cells and N-cadherins in mesothelial cells has been utilized to differentiate reactive mesothelial cells, MMs and ACAs. Calretinin is a calcium-binding protein within the family of EF-hand proteins. It is abundantly expressed in peripheral and central nervous tissues, and has been shown to consistently immunoreact with mesothelial cells. We studied cell block sections from 77 pleural effusions (22 RMC, 26 MM, and 29 ACA) to investigate the potential immunocytochemical use of anti-E-cadherin, anti-N-cadherin, and anti-calretinin antibodies for differentiating between RMC, MM, and ACA in pleural effusions. A modified avidin-biotin peroxidase complex (ABC) method was used. E-cadherin immunostaining was observed in 14% of RMC, 46% of MMs, and 97% of ACAs. A distinct membrane staining pattern was seen in ACAs. The pattern of staining was cytoplasmic in all reactive RMC and varied from membrane to cytoplasmic in MMs. Anti-N-cadherin immunoreacted with 77% of RMC, 35% of MMs, and 48% of ACAs. Twenty-seven percent of RMC, 58% of MMs, and 31% of ACAs immunoreacted with anti-calretinin. Based on these results, we conclude that anti-E-cadherin is a potentially useful marker in the distinction of ACA cells from RMC. However, it is not as useful for the distinction of ACA and MM. Anti-N-cadherin and anti-calretinin did not reliably distinguish between reactive mesothelial, MM, and ACA cells in pleural effusions.

Functional dissociation between local and systemic immune response during anti-melanoma peptide vaccination

Peptide vaccination against tumor Ags can induce powerful systemic CTL responses. However, in the majority of patients, no tumor regression is noted. To study this discrepancy, we analyzed CTL reactivity in a melanoma patient (F001) vaccinated with g209-2M peptide, a single residue variant of gp100(209-217). G209/g209-2M-reactive CTL were identified in post- but not prevaccination PBL. Limiting dilution analysis identified one predominant CTL clone (C1-35), with TCR Vbeta6s2, recognizing g209/HLA-A*0201-expressing targets. Additionally, two autologous melanoma lines (F001TU-3 and -4) and 20 separate tumor-infiltrating lymphocyte cultures were generated from a fine needle aspirate of a metastatic lesion progressing after initial response to vaccination. Both F001TU did not express gp100 and were not recognized by C1-35. Loss of gp100 by F001TU correlated with a marked reduction of gp100 expression in the same metastatic lesion compared with prevaccination. Thus, ineffectiveness of C1-35 and tumor progression could be best explained by loss of target Ag expression. Interestingly, 12 of 20 tumor-infiltrating lymphocyte cultures recognized F001TU, but none demonstrated g209/g209-2M reactivity, suggesting a functional dissociation between systemic and local immune response. This study suggests that vaccination effects must be analyzed in the target tissue, rather than in the systemic circulation alone.

If cells could talk. The application of new techniques to cytopathology

Cytopathology is no longer simply a screening modality limited to the "Pap mills" of yore. The news in cervicovaginal cytology is automation. The news in FNA cytology is the application of molecular techniques. Whether it is the detection of specific proteins/antigens for definitive diagnoses/treatment guidance in immunotherapy, or it is "reading nucleic acids," the cytopathologist of the future will be called upon to gather and report more detailed and precise information. As we develop methods for extrapolating the secrets previously locked within the individual cells, it becomes evident that the cells were talking all along, we just did not know how to listen.

Heterogeneous expression of melanoma-associated antigens and HLA-A2 in metastatic melanoma in vivo

MART-1/MelanA and Pmel17/gp100 are melanoma-associated antigens (MAAs) that can be recognized by tumor-infiltrating lymphocytes (TILs) capable of mediating successful adoptive therapy in vivo. Analysis of melanoma cell lines in vitro has demonstrated that heterogeneous antigen expression in the context of class I MHC is a significant co-factor in determining the recognition of melanoma targets by cytotoxic lymphocytes (CTLs). In this study, 217 specimens from 103 patients with metastatic melanoma were examined for the expression of MART-1/MelanA (monoclonal antibody [MAb] M27C10) and Pmel17/gp100 (HMB45 MAb) by immuno-histochemistry. Marked heterogeneity in the expression of both MAAs was confirmed by analysis of the percentage of positively staining tumor cells or the average intensity of tumor staining. We also noted heterogeneity of expression among multiple lesions taken from different anatomic sites within a patient. A dissociation was noted in the detection of MART-1 and gp100 in some lesions, with gp100 being undetectable in 24% of the lesions and MART-1 being undetectable in 11%. In several cases, loss of one MAA was not associated with loss of the other MAA, suggesting that MART-1 can represent a useful additional marker for the diagnosis of melanoma in gp100 (HMB45)-negative lesions. Of the 217 specimens, 155 were obtained from HLA-A*0201 patients, of which 6% were negative for HLA-A2, 8% were negative for MART-1/MelanA and 21% were negative for Pmel17/gp100. The potential significance of our findings is illustrated by a case study in which a patient with melanoma experienced rapid tumor progression in association with loss of either MAA or HLA expression in several lesions.

Use of recombinant poxviruses to stimulate anti-melanoma T cell reactivity

BACKGROUND

Dendritic cells (DC) are potent professional antigen-presenting cells that can activate naive T lymphocytes and initiate cellular immune responses. As adjuvants, DC may be useful for enhancing immunogenicity and mediating tumor regression. Endogenous expression of antigen by DC could offer the potential advantage of allowing prolonged constitutive presentation of endogenously processed epitopes and exploitation of multiple restriction elements for the presentation of the same antigen.

METHODS

DC were prepared from the peripheral blood of HLA A*0201 patients with metastatic melanoma in the presence of IL-4 (1000 IU/mL) and GMCSF (1000 IU/mL). Recombinant vaccinia and fowlpox viruses encoding the hMART-1 gene were constructed and used to infect DC. The efficiency of infection and expression of the MART-1 antigen were assessed by immunohistochemistry and intracellular FACS analyses. Cytotoxic lymphocytes (CTL) were generated by the stimulation of CD8+ T cells, with DC expressing the recombinant gene. Reactivity of the CTL was determined at weeks 1 and 2 by the amount of IFN-gamma released.

RESULTS

DC were infected with recombinant poxviruses and demonstrated specific melanoma antigen expression by immunohistochemistry, immunofluorescence, and intracellular FACS analysis. The expression by DC of MART-1 MAA after viral infection was sufficient to generate CD8+ T lymphocytes that recognized naturally processed epitopes on tumor cells in 10 of 11 patients.

CONCLUSIONS

Human DC are receptive to infection by recombinant poxviruses encoding MAA genes and are capable of efficiently processing and presenting these MAA to cytotoxic T cells. The potential advantage of this approach is the ability to present specific antigen independent of the identification of the epitope or the MHC restriction element. This strategy may be useful for the identification of relevant epitopes for a diverse number of HLA alleles and for active immunization in patients.

Comparative analysis of the in vivo expression of tyrosinase, MART-1/Melan-A, and gp100 in metastatic melanoma lesions: implications for immunotherapy

A variety of human melanoma-associated antigens (MAA) have been identified that can be recognized by T lymphocytes in a major histocompatibility complex-restricted fashion. Among them, tyrosinase, MART-1/Melan- A, and gp100 are derived from nonmutated melanocyte lineage-specific antigens (Ag). These Ag can be recognized by CD8+ and, in the case of tyrosinase, CD4+ T cells. The in situ expression of these MAA may be a significant cofactor in determining the recognition of melanoma targets by Ag-specific T cells. In this study, we examined the patterns of expression of these MAA using immunohistochemical methods on 30 metastatic tumor deposits derived from 25 patients. MAA expression was heterogeneous among the 30 specimens and also within individual lesions. Of note, 23% of the samples examined failed to express the gp100 protein, and 17% of samples had no detectable expression of MART-1. In contrast, all lesions demonstrated some degree of tyrosinase expression even in cases where both gp100 and MART-1 were not detectable. In addition, 60% of samples (18 of 30) showed strong positivity for tyrosinase (> 75% of cells staining) compared with 40% for gp100 and 36% for MART-1. Currently, a number of experimental immunotherapies for melanoma are directed against the MAA tyrosinase, MART-1, and gp100. Although threshold levels of Ag required for T-cell recognition have not yet been defined, tumor-associated Ag expressed in high density, such as tyrosinase, may be better targets for future immunotherapy trials.

Generation and genetic characterization of immortal human prostate epithelial cell lines derived from primary cancer specimens

Difficulty in establishing long-term human prostate epithelial cell lines has impeded efforts to understand prostate tumorigenesis and to develop alternative therapies for prostate cancer. In the current study, we describe a method that was successful in generating 14 immortal benign or malignant prostate epithelial cell cultures from primary adenocarcinomas of the prostate resected from six successive patients. Immortalization with the E6 and E7 transforming proteins of human papilloma virus serotype 16 was necessary to establish long-term cultures. Microscopic examination of fresh tumor specimens exhibited a variable mixture of benign and malignant epithelium. Thus, single-cell cloning of tumor-derived cell cultures was essential for defining tumor cell lines. Efforts to characterize these cultures using traditional criteria such as karyotype, growth in nude mice, and prostate-specific antigen expression were noninformative. However, allelic loss of heterozygosity (LOH) represents a powerful alternative method for characterizing tumor cell lines originating from primary adenocarcinomas of the prostate. Microdissected fresh tumors from four of six patients revealed LOH at multiple loci on chromosome 8p, as assessed by PCR. LOH on chromosome 8p matching the patterns found in microdissected tumors was also observed in a tumor-derived cell line and its clones, as well as in one clone from a tumor-derived cell line from a second patient. LOH was not observed in immortal lines generated from autologous benign prostatic epithelium, seminal vesicle epithelium, or fibroblasts. The multifocal nature of prostate cancer, as well as the presence of an entire spectrum of malignant transformation within individual prostate glands, necessitates this type of careful analysis of derivative cell cultures for their validation as in vitro models that accurately reflect the primary cancers from which they are derived.

Effusion cytology of malignant melanoma. A morphologic and immunocytochemical analysis including application of the MART-1 antibody

BACKGROUND

Malignant effusions are complications of metastatic malignant melanoma (MM). Differential diagnosis often involves distinguishing MM from adenocarcinoma and reactive mesothelial cells. Descriptions in the literature of the morphologic and immunocytochemical (IM) staining characteristics of MM in effusions are sparse. A combination of morphology and immunocytochemistry should yield the most accurate diagnostic results. The MART-1 antigen, a transmembrane protein, is specifically expressed in melanocytes and MM. A recently developed monoclonal antibody to the MART-1 antigen may represent a useful marker for the identification of MM in effusions.

METHODS

The authors conducted a retrospective review of 32 effusion samples diagnosed as MM. The review consisted of morphologic and IM analyses of the effusion samples with antibodies to MART 1, HMB45, S-100, and cytokeratins (AE1/ AE3). IM stains were performed on cell block or cytospin material, depending on availability. In the morphologic review, emphasis was placed on Diff Quik-stained material, due to its enhanced cytoplasmic volume and detail.

RESULTS

Predominant cytologic features noted were lack of cellular cohesion (in 100% of cases), large eccentric nuclei with prominent nucleoli (in 100%), multinucleation (in 84%), variable cytoplasmic vacuolization (in 75%), pigment (in 72%), and cell-in-cell engulfment (in 47%). All immunoreactive cases with sufficient material stained with at least one of the markers used. Tumor cells were positive with IM stains to MART-1 in 78% of cases, HMB45 in 81%, and S-100 in 81%. Coexpression of MART-1, HMB45, and S-100 was noted in 63% of cases. Of cases that showed expression for only 1 of the 3 antigens, the MART-1 was positive in 1 case, and HMB45 and S-100 were positive in 2 cases each. Three cases showed immunoreactivity for cytokeratins in the melanoma cells.

CONCLUSIONS

The diagnosis of MM in effusions can be made reliably through a combination of morphologic and IM features. Differential diagnosis often involves distinguishing MM from adenocarcinoma or reactive mesothelial cells. Cytoplasmic vacuolization, multinucleation, prominent nucleoli, and cell-in-cell engulfment are cytologic features common to all three. The lack of IM staining for cytokeratins alone cannot reliably distinguish MM; 11% of cases showed positive staining with this antibody in the melanoma cells. The use of a panel of antibodies increases the accuracy of diagnosing MM. In this study, MART-1 proved a useful adjunct to the HMB45/S-100/cytokeratin panel for the diagnosis of MM in effusions, staining 78% of the immunoreactive cases, with positivity in 1 case that was negative for HMB45 and S-100.

Analysis of expression of the melanoma-associated antigens MART-1 and gp100 in metastatic melanoma cell lines and in in situ lesions

MART-1 and gp100 melanoma associated antigens (MAA) are expressed by cells of the melanocytic lineage and are recognized by the majority of HLA-A2 restricted tumor-infiltrating lymphocytes. Heterogeneity of expression of MAA in tumor deposits may affect the natural history or response to therapy of patients with melanoma. In this study, we evaluated the expression of these MAA with a new monoclonal antibody (mAb) directed against MART-1 (M2-7C10) and the commercially available HMB45 mAb directed against gp100. Expression was tested in vitro by intracellular fluorescence analysis and in vivo by immunophenotyping of tissue specimens. Nine melanoma cell lines and 25 tissue specimens from metastatic melanoma were analyzed. One cell line did not express MART-1 or gp100. The expression of both antigens was more heterogeneous and significantly reduced (p < 0.01) in melanoma cell lines compared with melanocytes, suggesting progressive loss of expression of MAA by neoplastic cells. None of the nonmelanoma cancer lines tested stained for MART-1 or gp100. Analysis of melanoma lesions by immunohistochemistry showed significant heterogeneity of expression of both MART-1 and gp100 MAA either as a percentage of cells expressing MAA or as intensity of expression. Ten of 25 frozen sections expressed MART-1 in < 50% of the cells. In 6 of 25 lesions, immunoreactivity for MART-1 was totally absent. Fine needle aspiration of metastatic lesions seemed to yield information accurately about amount and heterogeneity of expression of MAA in tumor lesions in vivo. Heterogeneity of expression of MAA may be one of several mechanisms leading to tumor escape from immune recognition, and pretreatment evaluation of tumor lesion for expression of these antigens may help in selecting patients best suited to antigen-specific vaccine therapies.

Fluorescence in situ hybridization (FISH): a user's guide to optimal preparation of cytologic specimens

Fluorescence in situ hybridization (FISH) is a reliable method for tagging centromeric regions of specific chromosomes in interphase nuclei. Not only is FISH useful for chromosome enumeration, but as region-specific chromosome probes are developed, the clinical applications and potentials for use by pathologists are extensive. This technique lends itself particularly to use in cytology preparations because the cells are disaggregated and monolayer preparations yield excellent technical hybridization results. Over a 7-mo period we processed cytologic samples in an attempt to define and outline a method for optimal specimen processing for FISH use in cell suspensions, techniques applicable to all fresh cytology specimens which can also be used for the processing of surgical pathology aspirates and other material. All samples should be promptly processed to ensure specimen viability, and triaged on an individual basis to ensure preparation of moderately cellular monolayered cytospins. Equivalent nuclear probe signals have been obtained with several sample fixation methods: air-drying, 95% ethanol, methanol (Diff-Quik fixative), and Carnoy's solution. No difference was noted in the nuclear probe signals or specimen adhesion on positively charged or noncharged slides. After initial fixation our slides remained at room temperature until FISH was performed, without any adverse effects. A short digestion with proteinase K and subsequent rehybridization yielded positive results on samples that originally yielded poor nuclear probe signals.

Locus-specific analysis of human leukocyte antigen class I expression in melanoma cell lines

Surface expression of human leukocyte antigen (HLA) class I antigens on melanoma lines was evaluated by locus-specific monoclonal antibodies (mAbs) with three different techniques: Fluorescence-activated cell sorting (FACS), immunohistochemistry with cytospin preparation (ICP), and complement-mediated cytotoxicity (CMC). Eleven HLA class I-expressing cell lines developed from metastases were used. Specific expression of HLA loci was examined under routine culture conditions and after 48-h incubation in interferon-gamma (IFN-gamma; 500 U/ml). Loss of allelic expression was seen in one line (586-MEL): Products of genes coding for HLA-A29 and -B44, in strong linkage disequilibrium, were not detectable. HLA-A antigens were consistently detected by all methodologies and minimally affected by pretreatment with IFN-gamma. HLA-B antigens were detectable in 8 of 11 lines by ICP and 3 of 11 lines by CMC. By FACS the supratypic specificity HLA-Bw6 was expressed at low levels in most lines (mean fluorescence 47.2 +/- 13.4 and rose to 259.8 +/- 45.9 after incubation with IFN-gamma; p < 0.001). HLA-Cw antigen detection by CMC correlated with HLA-B (p < 0.01), suggesting that down-regulation and sensitivity to IFN-gamma are shared by the two loci. This low expression of the HLA-B antigens may play a role in the evasion of the host immune response and its up-regulation may be useful in allowing tumor antigen recognition.