Dusting for Fingerprints

Noninvasive Genomic Melanoma Detection

Hensin Tsao, MD, PhD

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In This Article

Abstract and Introduction

Abstract

Tape stripping of the stratum corneum produced highly sensitive and specific melanoma identification.

Introduction

An accurate genetic fingerprint for melanoma may finally be available through common "dust." Tape stripping of the stratum corneum has been used in skin research for some time. Investigators conducted a trial of an epidermal genetic information retrieval (EGIR) system, which uses a custom adhesive film to noninvasively sample RNA from the stratum corneum, enabling such downstream applications as expression analysis.

These investigators, some of whom serve on the advisory board and some as employees of the manufacturer, used EGIR to sample skin overlying pigmented lesions: 29 melanomas (in situ and invasive) and 68 nevi (benign and atypical), and 15 normal skin specimens. RNA from the tape was subjected to transcriptome analysis, and computational methods were used to isolate 312 differentially expressed genes, which fell into two large groups: One encompassed all 29 melanomas and 13 of the nevi, and the other included the bulk of the nevi, as well as all of the normal skin specimens. The genes in the "melanoma" group are involved in regulation of melanocyte development and pigmentation signaling, skin development, cellular development, and cancer. Genes in the "nevus" group have a role in cellular growth and proliferation, embryonic development, and skeletal and muscular system development and function.

Using a training set of melanoma lesions and nevi (including in situ, invasive, superficial spreading, lentigo maligna, lentigo maligna melanoma, and dysplastic and nondysplastic nevi), the investigators produced a 168-gene fingerprint that correctly identified 37 of 38 melanomas and 35 of 37 nevi. Sensitivity and specificity for detecting melanoma in the training dataset were 100% and 95%, respectively. Additional statistical refinement reduced the 168-gene discriminator to a set of 17 genes that remained 100% sensitive and 88% specific. This 17-gene classifier was negative for all nonlesional skin specimens and solar lentigines, and for 17 of 18 basal cell carcinomas, demonstrating that the expression signature was specific for melanoma.

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