Malignant melanoma (MM) remains the deadliest form of skin cancer. The current advances in patient cancer care and treatment for melanoma patients, which include wide local excision as a day case procedure or surgery which involve overnight stay in the hospital, radiotherapy, and chemotherapy. The treatment considerably prolongs the survival of patients, but a percentage of cancer patients do not respond to standard therapy or relapse after treatment and after metastasis survival rates drop significantly.
In histopathological interpretation morphological assessment of any melanocytic lesion is always key, but recent developments within the field of immunocytochemistry (IHC) have provided great support in aiding the distinction of the dysplastic verses malignant lesions. This does not just apply to the diagnosis, but also more recently in providing information regarding prognosis and determining patient therapeutics. Unfortunately, at present these therapeutic regimes are often short term. As a result, new biomarkers and drug targets are constantly needed in order to develop and improve the accuracy of diagnosis and treatment.
The call for alternative targeted therapies involving several novel therapeutic drugs that target specific molecules is continuously underway. The most common therapy for MM patients who have the BRAF V600E mutation status is the employment BRAF inhibitors such as Vemurafenib to slow down the disease spread in advanced, metastatic melanoma. However, some patients develop the resistance to BRAF inhibitors which can occur frequently. The study by Orchard et al. (2019) fully supports the need for alternative treatment therapy with patients with different mutation status such as BRAF V600K.
In recent times in 2015, ROCHE Ventana Diagnostics have yielded forward, the first ready-to-use IVD IHC antibody that permits the IHC cellular pathology to evaluate the expression of BRAF V600E mutation in malignant melanoma with clinical confidence using the OptiView DAB IHC Detection Kit. According to ROCHE, the BRAF V600E (VE1) antibody can detect mutation in papillary thyroid carcinoma, colorectal cancers and malignant melanoma (Reagent-catalog.roche.com, 2018).
The published study by Orchard et al., 2019 demonstrated the close correlation between Sanger sequencing molecular detection of BRAF V600E mutation versus IHC employment of anti-BRAF V600E in a clinical laboratory (Figure 1A and B)
Figure 1 A and B. Figure 1A HE of a superficial spreading malignant melanoma. Showing spreading of nests of pagetoid atypical melanocytes Magx20. Figure 1b BRAF V600E (VE-1) staining tumor cells from Fig 1 a in a cytoplasmic staining pattern. Mag x20
PRAME is a member of the family of cancer-testis antigens (CTA), and an attractive target for immunotherapy. Several clinical trials are underway trying to utilize CTAs, including PRAME, for cancer treatment (Al-Khadairi and Decock, 2019). The clinical trial PHASE 1 involving PRAME dosage in un-resectable and progressive metastatic cutaneous melanoma administering combined plasmid-peptide vaccine derived from PRAME, showed a clinically acceptable safety profile (Gutzmer et al., 2016). PHASE 2 of this clinical trial is also planned to further evaluate PRAME’s potential as an immunotherapeutic drug/vaccine. The employment of PRAME antibody in a diagnostic laboratory can prove invaluable addition in the clinical setting distinguishing benign and malignant melanocytic lesions. Moreover, possession of a novel antibody, its significance in expression in melanoma and being able to visualize PRAME staining, may prove invaluable input to assess the limits in the sensitivity and specificity of molecular tests, which contain PRAME gene expression as reference range.
Figure 2(A-B)- Melanoma in situ (MIS) (Fig. 2A) H&E staining demonstrating junctional component that consists of nesting and lentiginous proliferation of melanocytes with pink cytoplasm, Fig.2B shows nuclear labelling of tumor cells that are anti-PRAME positive(1+) in the epidermis component.
PRAME is positively expressed in the vast majority of primary cutaneous malignant melanoma, with the lowest reported positivity rates found in desmoplastic melanomas. Furthermore, the PRAME positive IHC staining in melanocytic nevi is rare; therefore, its value can be utilised as a supplementary tool for the distinction of melanocytic nevi from melanoma.
The clinical trials employing PRAME in immunotherapy are underway and look promising, and this research outlines essential advance towards improving diagnostic methods for assessment of malignant melanoma.
Further studies are required to analyse the expression in different types of malignant tumours thoroughly such as lung, breast and colon cancers.
Following this research study, the application of this antibody will support the process of validation/ verification into laboratory antibody repertoire laboratory.
NB :- In our hands concordance between IHC and molecular tests =100%
Data on PRAME in our hands indicate that it is positively expressed in the vast majority of primary cutaneous malignant melanoma, with the lowest reported positivity rates found in desmoplastic melanomas. Furthermore, the PRAME positive IHC staining in melanocytic nevi is rare; therefore, its value can be utilized as a supplementary tool for the distinction of melanocytic nevi from melanoma.
We are beginning to understand the underlying mechanisms of the disease, including melanogenesis, and also how melanomas evade the immune system. IHC continues to play its part in the field; although both useful in diagnosis and prognosis, there is a need to standardise the subjectivity of interpretation of IHC to ensure reproducibility and consistency between laboratories and also between pathologists. This becomes increasingly important as new biomarkers are found and assessed employing the evolution of digital technology.
Want to learn more about BRAF V600E and PRAME? Join Dr. Orchard for his session, WS-02 New Companion Diagnostic Markers BRAF V600E and PRAME for Use in Malignant Melanoma Patient Management, Tuesday, Sep 14; 1:00 PM ET - 2:00 PM ET at the NSH Convention.
Written by Guy Orchard PhD, MSc (dist), FIBMS, CSci, Tissue Sciences, Viapath Analytics an NHS partnership with Synlab, St. John’s Histopathology, St. Thomas’ Hospital, London, UK
References:-
Al-Khadairi G, Decock J. Cancer Testis Antigens and Immunotherapy: Where Do We Stand in the Targeting of PRAME?. Cancers (Basel). 2019;11(7):984. Published 2019 Jul 15. doi:10.3390/cancers11070984 [Accessed 1 Dec. 2019].
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Bad.org.uk. (2017). MELANOCYTIC NAEVI (PIGMENTED MOLES). [online] Available at: https://www.bad.org.uk/shared/get-file.ashx?id=100&itemtype=document [Accessed 8 Feb. 2020]
Gutzmer R, Rivoltini L, Levchenko E, et al. Safety and immunogenicity of the PRAME cancer immunotherapeutic in metastatic melanoma: results of a phase I dose escalation study. ESMO Open. 2016;1(4):e000068. Published 2016 Aug 8. doi:10.1136/esmoopen-2016-000068 [Accessed 1 Dec. 2019]
Lezcano, C., Jungbluth, A., Nehal, K., Hollmann, T. and Busam, K. (2018). PRAME Expression in Melanocytic Tumors. The American Journal of Surgical Pathology, [online]42(11),pp.1456-1465. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6631376/ [Accessed 11 Dec. 2019].
Orchard, G.E., Wojcik, K., Rickaby, W, Martin, B., Semkova, K., Shams, F., Stefanato, C.M., (2019) Immunohistochemical detection of V600E BRAF mutation is a useful primary screening tool for malignant melanoma, British Journal of Biomedical Science, 76:2, 77-82, DOI: 10.1080/09674845.2019.1592885 [Accessed 1 Dec. 2019].
Long.G, Wilmott J.S, Capper D et al. Immunohistochemistry is highly sensitive and specific for the detection of V600E BRAF mutation in melanoma. Am. J. Surg. Pathol. 2013, 37(1); 61-65.
Schirosi. L, Strippoli S, Gaudio F. et al. Is immunohistochemistry of BRAF V600E useful as a screening tool and during progression disease of melanoma patients? BMC Cancer 2016; 16:905 p1-11.
Arkenau H.T, Kefford R, Long G.V. Targeting BRAF for patients with melanoma. Br. J. Cancer. 2011; 104:392-398.
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