Transcriptome-Wide Studies of Merkel Cell Carcinoma and Validation of Intratumoral CD8+ Lymphocyte Invasion As an Independent Predictor of Survival

Abstract

Purpose Merkel cell carcinoma (MCC) is a polyomavirus-associated skin cancer that is frequently lethal and lacks established prognostic biomarkers. This study sought to identify biomarkers that improve prognostic accuracy and provide insight into MCC biology. Patients and Methods Gene expression profiles of 35 MCC tumors were clustered based on prognosis. The cluster of genes overexpressed in good-prognosis tumors was tested for biologic process enrichment. Relevant mRNA expression differences were confirmed by quantitative polymerase chain reaction and immunohistochemistry. An independent set of 146 nonoverlapping MCC tumors (median follow-up, 25 months among 116 living patients) was employed for biomarker validation. Univariate and multivariate Cox regression analyses were performed. Results Immune response gene signatures were prominent in patients with good prognoses. In particular, genes associated with cytotoxic CD8+ lymphocytes were overexpressed in tumors from patients with favorable prognoses. In the independent validation set, cases with robust intratumoral CD8+ lymphocyte infiltration had improved outcomes (100% MCC-specific survival, n = 26) compared with instances characterized by sparse infiltration (60% survival, n = 120). Only stage and intratumoral CD8 infiltration (but not age, sex, or CD8+ lymphocytes localized to the tumor-stroma interface) were significant in both univariate and multivariate Cox regression analyses. Notably, traditional histologic identification of tumor-infiltrating lymphocytes was not a significant independent predictor of survival. Conclusion Intratumoral CD8+ lymphocyte infiltration can be readily assessed on paraffin-embedded tissue, is independently associated with improved MCC-specific survival, and therefore, may provide prognostic information that enhances established MCC staging protocols.

Rationale For Immune-Based Therapies in Merkel Polyomavirus-Positive and -Negative Merkel Cell Carcinomas

“…The importance of the CD8 T cell response against MCC is highlighted by the finding that robust intratumoral (not peritumoral) infiltration of CD8+ TILs is associated with a striking 100% survival in a study of 146 patients [46]. Additional studies have also indicated that MCC TILs, including CD3+, CD8+ T cells, are associated with improved overall and disease-specific survival [47,48].…”

“…Additional studies have also indicated that MCC TILs, including CD3+, CD8+ T cells, are associated with improved overall and disease-specific survival [47,48]. Furthermore, expression of genes encoding granzyme A, B, H and K, CCL19, lymphocyte activation genes (SLAMF1 and NKG2D) and CD8α are associated with favorable prognoses, independent of stage [46]. To date, 17 MCPyV-specific CD8 epitopes have been identified, for which 14 HLA-I tetramers have been generated, enabling functional and phenotypic analysis [43,45,49,50].…”

Human Merkel cell polyomavirus: virological background and clinical implications

“…Factors recognized as associated with poor prognosis are size of the tumor and presence of metastases according to the AJCC staging (4,47,55,(64)(65)(66)(67)(68), and immunosuppression (65,69,70). Recently, histological and immunochemistry markers have been described as potentially associated with poor outcome like low tumor infiltrating CD8 + T cells (101) and P53 and P63 expression and gen mutations (54, 68, 74) ( Table 2).…”

Disruption of BRD4 at H3K27Ac-enriched enhancer region correlates with decreased c-Myc expression in Merkel cell carcinoma

“…3 Although multiple microarray studies have provided insights into MCC pathogenesis, molecular events essential to MCC pathogenesis are largely unknown. [4][5][6] Though the principal tenet in cancer is that tumor is initiated and driven by mutations, it is now clear that epigenetic pathways also play a significant role in oncogenesis. Moreover, diverse gene mutations generally converge functionally to deregulate similar core cellular process, which can be targeted by approaching epigenetic vulnerabilities.…”