Melanoma antigen expression in serial fine-needle aspiration samples in patients with metastatic malignant melanoma participating in immunotherapy clinical trials: a preliminary look

Serial FNA allows direct sampling of malignant and infiltrating immune cells in patients with B-cell lymphoma receiving immunotherapy

BACKGROUND

Fine-needle aspiration (FNA) is used to diagnose malignancies, recurrences, and metastases. The procedure is quick and well tolerated and can be facilitated by ultrasound guidance.

METHODS

This article describes the authors' experience in using serial FNA to harvest cellular material during 4 clinical trials of immunotherapy by in situ vaccination in patients with low-grade lymphoma.

RESULTS

Two hundred ninety-six FNA samples were collected from 44 patients over a span of approximately 6 weeks for each patient. Samples were sufficient in quantity and quality to be analyzed by flow cytometry and/or single-cell messenger RNA sequencing. FNA samples yielded an average of 12 × 10⁶ cells with a mean cellular viability of 86%. Material collected from the tumor lymph nodes differed significantly in the proportions and phenotypes of cellular populations in comparison with matched peripheral blood samples. A comparison of flow cytometry results obtained by FNA directly from the patient and by FNA performed ex vivo and a dissociation of the same lymph node after surgical excision confirmed that FNA sampling of the patient accurately represented the tumor and the microenvironment. An analysis of the FNA samples from immunotherapy-treated target lymph nodes versus nodes from nontreated tumor sites provided insight into the impact of specific immunotherapy regimens.

CONCLUSIONS

This is the largest study describing the use of serial FNA sampling to harvest cellular material during immunotherapy clinical trials. The success of this technique opens the door for FNA sampling to expand significantly future investigations of the dynamic effects of investigational agents, be they immunotherapies or targeted therapies.

Location, location, location: The relationship of anatomic site, antigen expression, and T-cell infiltration in human melanoma metastases

Metastatic cell heterogeneity presents a significant obstacle to the development of targeted molecular and immunotherapeutics. Profiling of melanocyte differentiation antigens has revealed a nonstochastic, site-specific pattern of expression in metastases that was highest in brain, intermediate in soft tissues/lymph nodes, and lowest in visceral sites. Site-specific antigen heterogeneity, thus, is an important confounding factor to consider when assessing the potential efficacy of antigen-specific therapies.

Human melanoma metastases demonstrate nonstochastic site-specific antigen heterogeneity that correlates with T-cell infiltration

PURPOSE

Metastasis heterogeneity presents a significant obstacle to the development of targeted cancer therapeutics. In this study, we sought to establish from a large series of human melanoma metastases whether there exists a determined pattern in tumor cellular heterogeneity that may guide the development of future targeted immunotherapies.

EXPERIMENTAL DESIGN

From a cohort of 1,514 patients with metastatic melanoma, biopsies were procured over a 17-year period from 3,086 metastatic tumors involving various anatomic sites. To allow specific tumor cell profiling, we used established immunohistochemical methods to perform semiquantitative assessment for a panel of prototypic melanocyte differentiation antigens (MDA), including gp100, MART-1, and tyrosinase. To gain insight into the endogenous host immune response against these tumors, we further characterized tumor cell expression of MHC I and MHC II and, also, the concomitant CD4(+) and CD8(+) T-cell infiltrate.

RESULTS

Tumor cell profiling for MDA expression demonstrated an anatomic site-specific pattern of antigen expression that was highest in brain, intermediate in soft tissues/lymph nodes, and lowest in visceral metastases. Hierarchical clustering analysis supported that melanoma metastases have a phylogenetically determined, rather than a stochastic, pattern of antigen expression that varies by anatomic site. Furthermore, tyrosinase expression was more frequently lost in metastatic sites outside of the brain and was uniquely correlated with both endogenous CD8(+) and CD4(+) T-cell infiltrates.

CONCLUSION

Site-specific antigen heterogeneity represents a novel attribute for human melanoma metastases that should be considered in future therapy development and when assessing the responsiveness to antigen-specific immunotherapies.

Skin layer-specific Melan-A expression during progression of human cutaneous melanoma: implications for diagnostic applications of the marker

Melan-A is widely used in the diagnostics of human melanoma. The immunogenicity of this glycoprotein makes it a potential target in immunotherapy and several authors have suggested its potential as a prognostic factor. Up to now there has been no clear direct evidence of changes of Melan-A expression during the progression of melanoma. We have performed objective immunohistochemical assessment of the expression of Melan-A in benign naevi and melanomas at different stages of progression. Our results show a complex pattern of changes in the expression of Melan-A in melanomas depending on the location of melanoma cells within individual skin layers. The expression of the antigen during tumour progression significantly decreases for melanoma cells located in the granular/spinous layer (r=-0.94, P=0.02) and increases for the papillary layer (r=0.99, P=0.002) and reticular layer (r=0.89, P=0.04). It should also be emphasized that from the Clark II level of progression the melanomas can be detected with high sensitivity and specificity using a simple cut-off test based on the determination of Melan-A expression in tumour cells located within the papillary layer.

Measuring tissue-based biomarkers by immunochromatography coupled with reverse-phase lysate microarray

PURPOSE

There is a need for new technologies to study tissue-based biomarkers. The current gold standard, immunohistochemistry, is compromised by variability in tissue processing and observer bias. Reverse transcription-PCR (RT-PCR), immunocytochemistry, and reverse-phase lysate microarrays (RPM) are promising alternative technologies but have not yet been validated, or correlated, on the same patient-derived tissues. Furthermore, RPM is currently limited by time-consuming microdissection and low amounts of evaluable protein lysates.

EXPERIMENTAL DESIGN

Metastatic melanoma was surgically excised from 30 patients and macroscopically dissected from surrounding stroma. Each specimen was processed by formalin-fixation (immunohistochemistry), cytospin (immunocytochemistry), or disaggreagation and enrichment (RT-PCR and RPM). The latter protocol uses immunochromatography to remove hematopoetic-derived cells, thus enriching for melanoma cells. Each sample was measured for the expression of gp100 or MART-1 normalized to actin.

RESULTS

Immunochromatography coupled with RPM (I-RPM) is reproducible (r >/= 0.70) and, for gp100, correlates strongly with immunohistochemistry and immunocytochemistry (r = 0.78 and 0.76, respectively) and moderately with transcript levels, measured by RT-PCR (r = 0.61). In contrast, for MART-1, I-RPM correlates strongly with transcript level (r = 0.78) but only moderately strong correlations are noted with immunohistochemistry and immunocytochemistry (r = 0.64 and 0.59, respectively). In general, transcript levels show only moderately strong correlations with immunohistochemistry and immunocytochemistry (r = 0.41-0.64).

CONCLUSION

I-RPM is a promising technology for quantitative grading of tissue biomarkers; however, antigen-dependent correlations are noted.

Differential expression of melanoma-associated antigens and molecules involved in antigen processing and presentation in three cell lines established from a single patient

Tumour cells are able to evade the immune system by using several 'escape mechanisms'. Downregulation of molecules involved in the processing and presentation of self-antigens has been reported. However, these adaptations have not been compared in metastases in different anatomical locations but derived from a single patient. We investigated three melanoma cell lines--MJT1 from the parietal lobe of the brain, MJT3 from the cerebellum and MJT5 from the left side of the neck--established from biopsies excised from a 45 year old female patient. Although human leukocyte antigen (HLA) class I was detected in all three cell lines by flow cytometry using an anti-HLA monomorphic antibody, further serological analysis demonstrated HLA B38 loss in all three cell lines, HLA B7 downregulation in MJT5 (skin metastases) and B7 loss in MJT3 and MJT1 (brain metastases) compared with the HLA type of the patient's normal autologous lymphocytes. Interferon-gamma (IFNgamma) treatment increased the expression of HLA class I and transporters associated with antigen processing 1 (TAP1) in all three cell lines. De novo HLA class II molecule expression was observed after IFNgamma treatment in MJT3 and MJT5. Western blot and reverse transcription-polymerase chain reaction results revealed heterogeneity of melanoma-associated antigen (MAA) expression in the cell lines: MJT3 cells expressed higher levels of MAAs than the other two cell lines. In conclusion, this study has demonstrated that three metastatic lesions from a single patient can have differential expression of molecules involved in antigen processing (TAP1) and presentation (HLA I and II), but that expression of these molecules is modulated by IFNgamma to a similar degree in all cell lines. In contrast, the downregulation of expression of specific MAAs between the three cell lines was unaffected by the addition of IFNgamma.

Is MAGE-1 expression in metastatic malignant melanomas really helpful?

Melanoma antigen-encoding gene (MAGE-1) has been introduced as a sensitive immunohistochemical marker to aid in the diagnosis of malignant melanomas, in particular, those that are HMB-45 negative. Our goal was to determine the consistency of positive staining in melanomas on the basis of the usefulness of MAGE-1 in comparison with tyrosinase and MART-1. We studied 56 malignant melanomas using immunohistochemical markers to MAGE-1, tyrosinase, MART-1, HMB-45, and S-100. Six of 17 HMB-45-negative cases were strongly positive for MAGE-1 (35%), while 9 of 39 HMB-45-positive cases were positive for MAGE-1 (23%), overall, 27% positivity (n = 56). Tyrosinase and MART-1 were both strongly positive in 42 of 56 cases (75%). Fifty-two of 56 cases were strongly positive for S-100 (93%). We found MAGE-1 to be less sensitive than described in other studies, and overall, not very helpful, especially as a predictor of aggressive behavior. Although MAGE-1 expression has been considered as a target for immunomodulation therapy, our findings do not indicate consistent expression of this epitope in a majority of melanomas. S-100 protein, tyrosinase, and MART-1 immunomarkers were more frequently positive in our melanoma cases and appear to constitute a useful panel of markers to aid in the diagnosis of metastatic malignant melanomas, especially in patients with an unknown primary.

Metastatic balloon cell melanoma in a dog

BACKGROUND

Balloon cell melanoma is a rare variant of amelanotic melanoma that is difficult to differentiate from sebaceous cell carcinoma, liposarcoma, and other clear cell neoplasms without immunohistochemistry or ultrastructural evidence of melanin or melanosomes.

OBJECTIVE

The purpose of this report was to describe the clinical, cytologic, histologic, immunohistochemical, and ultrastructural findings in a dog with metastatic balloon cell melanoma.

METHODS

A 6-year-old female Golden Retriever was evaluated for a white, flocculent infiltrate in the anterior chamber of the left eye and an enlarged left prescapular lymph node. Cytologic evaluation of the eye and lymph node were performed following aqueocentesis and fine-needle aspiration, respectively. The affected lymph node was examined histologically and stained for cytokeratin, vimentin, S-100, and Melan A. Following euthanasia a necropsy was performed and samples of the affected lymph node were examined by electron microscopy.

RESULTS

Cytologic examination of the lymph node and aqueocentesis sample revealed round neoplastic cells that had abundant clear vacuolated cytoplasm. A tentative diagnosis of metastatic sebaceous cell carcinoma or clear cell neoplasm was made. Histologically, the affected lymph node had similar polygonal clear cells arranged in sheets and packets divided by delicate fibrovascular stroma. Immunohistochemical staining of the cells was negative for cytokeratin but positive for vimentin, weakly positive for S-100, and strongly positive for Melan A. At necropsy, metastatic lesions were identified in the diaphragm, heart, lung, kidneys, left eye, prescapular and sublumbar lymph nodes, and multiple skin sites. Ultrastructural examination of neoplastic lymph nodes revealed many membrane-bound vacuoles, myelin-like figures, and rare melanosomes.

CONCLUSION

Immunohistochemical staining and ultrastructural features of the neoplastic cells supported a diagnosis of metastatic balloon cell melanoma.