Merkel cell carcinoma (MCC) is an uncommon, but highly malignant, cutaneous tumor. Merkel cell polyoma virus (MCV) has been implicated in a majority of MCC tumors; however, viralnegative tumors have been reported to be more prevalent in some geographic regions subject to high sun exposure. While the impact of MCV and viral T-antigens on MCC development has been extensively investigated, little is known about the etiology of viralnegative tumors. We performed targeted capture and massively parallel DNA sequencing of 619 cancer genes to compare the gene mutations and copy number alterations in MCV-positive (n ¼ 13) and -negative (n ¼ 21) MCC tumors and cell lines. We found that MCV-positive tumors displayed very low mutation rates, but MCV-negative tumors exhibited a high mutation burden associated with a UV-induced DNA damage signature. All viral-negative tumors harbored mutations in RB1, TP53, and a high frequency of mutations in NOTCH1 and FAT1. Additional mutated or amplified cancer genes of potential clinical importance included PI3K (PIK3CA, AKT1, PIK3CG) and MAPK (HRAS, NF1) pathway members and the receptor tyrosine kinase FGFR2. Furthermore, looking ahead to potential therapeutic strategies encompassing immune checkpoint inhibitors such as anti-PD-L1, we also assessed the status of T-cell-infiltrating lymphocytes (TIL) and PD-L1 in MCC tumors. A subset of viral-negative tumors exhibited high TILs and PD-L1 expression, corresponding with the higher mutation load within these cancers. Taken together, this study provides new insights into the underlying biology of viral-negative MCC and paves the road for further investigation into new treatment opportunities. Cancer Res; 75(24); 5228-34. Ó2015 AACR.
A djuvant immune checkpoint inhibition (CPI) and BRAF/ MEK-targeted therapies after therapeutic lymph node dissection (TLND) have improved relapse-free survival (RFS) in patients with clinical stage III nodal melanoma. Despite these improvements, approximately 40-50% of patients have a relapse within 3-5 years after TLND 1-3 . Preclinical and early clinical trial data suggest that neoadjuvant CPI leads to superior anti-tumor immunity and survival benefit compared to adjuvant CPI 4,5 . Similarly to stage IV melanoma, the combination of anti-CLTA-4 and anti-PD-1 appears to be superior to anti-PD-1 monotherapy in the neoadjuvant setting 6,7 . Previous clinical trials (OpACIN (NCT02437279) and OpACIN-neo (NCT02977052)) testing neoadjuvant ipilimumab (anti-CTLA-4) plus nivolumab (anti-PD-1) in stage III melanoma demonstrated high pathologic response rates (pRRs; 74-78%) and a strong association between pathologic response and RFS, with 94-100% of responding patients remaining free of relapse at 2 years 5,7-9 . Similarly, long-term benefit was observed upon complete response to CPI in stage IV melanoma, even after cessation of CPI [10][11][12] .The association between response and survival; the observed ongoing responses after cessation of therapy in stage IV melanoma; and the substantial morbidity from TLND [13][14][15][16] that impairs
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