Resident and circulating memory T cells persist for years in melanoma patients with durable responses to immunotherapy

While T-cell responses to cancer immunotherapy have been avidly studied, long-lived memory has been poorly characterized. In a cohort of metastatic melanoma survivors with exceptional responses to immunotherapy, we probed memory CD8+ T-cell responses across tissues, and across several years. Single-cell RNA sequencing revealed three subsets of resident memory T (TRM) cells shared between tumors and distant vitiligo-affected skin. Paired T-cell receptor sequencing further identified clonotypes in tumors that co-existed as TRM in skin and as effector memory T (TEM) cells in blood. Clonotypes that dispersed throughout tumor, skin and blood preferentially expressed an IFNG/TNF-high signature, which had a strong prognostic value for patients with melanoma. Remarkably, clonotypes from tumors were found in patient skin and blood up to 9 years later, with skin maintaining the most focused tumor-associated clonal repertoire. These studies reveal that cancer survivors can maintain durable memory as functional, broadly distributed TRM and TEM compartments. Turk and colleagues analyze exceptional responders to checkpoint blockade for melanoma, and detect tissue-resident memory and effector memory T-cell clonotypes in skin and blood, respectively, up to 9 years after treatment.