Immune evasion of dormant disseminated tumor cells is due to their scarcity and can be overcome by T cell immunotherapies.

The period between "successful" treatment of localized breast cancer and the onset of distant metastasis can last many years, representing an unexploited window to eradicate disseminated disease and prevent metastases. We find that the source of recurrence-disseminated tumor cells (DTCs) -evade endogenous immunity directed against tumor neoantigens. Although DTCs downregulate major histocompatibility complex I, this does not preclude recognition by conventional T cells. Instead, the scarcity of interactions between two relatively rare populations-DTCs and endogenous antigen-specific T cells-underlies DTC persistence. This scarcity is overcome by any one of three immunotherapies that increase the number of tumor-specific T cells: T cell-based vaccination, or adoptive transfer of T cell receptor or chimeric antigen receptor T cells. Each approach achieves robust DTC elimination, motivating discovery of MHC-restricted and -unrestricted DTC antigens that can be targeted with T cell-based immunotherapies to eliminate the reservoir of metastasis-initiating cells in patients.

Immune checkpoint blockade provokes resident memory T cells to eliminate head and neck cancer.

Immune checkpoint blockade is effective in treating many human cancers. In this issue of Cell, Luoma et al. show that tissue-resident memory T cells in head and neck cancers rapidly respond to immune checkpoint blockade, and they identify specific CD8+ T cells in pretreatment blood that predict pathologic tumor regression.

Neoantigen-specific CD4+ T cells in human melanoma have diverse differentiation states and correlate with CD8+ T cell, macrophage, and B cell function.

CD4+ T cells that recognize tumor antigens are required for immune checkpoint inhibitor efficacy in murine models, but their contributions in human cancer are unclear. We used single-cell RNA sequencing and T cell receptor sequences to identify signatures and functional correlates of tumor-specific CD4+ T cells infiltrating human melanoma. Conventional CD4+ T cells that recognize tumor neoantigens express CXCL13 and are subdivided into clusters expressing memory and T follicular helper markers, and those expressing cytolytic markers, inhibitory receptors, and IFN-γ. The frequency of CXCL13+ CD4+ T cells in the tumor correlated with the transcriptional states of CD8+ T cells and macrophages, maturation of B cells, and patient survival. Similar correlations were observed in a breast cancer cohort. These results identify phenotypes and functional correlates of tumor-specific CD4+ T cells in melanoma and suggest the possibility of using such cells to modify the tumor microenvironment.

A therapeutic cancer vaccine delivers antigens and adjuvants to lymphoid tissues using genetically modified T cells.

Therapeutic vaccines that augment T cell responses to tumor antigens have been limited by poor potency in clinical trials. In contrast, the transfer of T cells modified with foreign transgenes frequently induces potent endogenous T cell responses to epitopes in the transgene product, and these responses are undesirable, because they lead to rejection of the transferred T cells. We sought to harness gene-modified T cells as a vaccine platform and developed cancer vaccines composed of autologous T cells modified with tumor antigens and additional adjuvant signals (Tvax). T cells expressing model antigens and a broad range of tumor neoantigens induced robust and durable T cell responses through cross-presentation of antigens by host DCs. Providing Tvax with signals such as CD80, CD137L, IFN-ß, IL-12, GM-CSF, and FLT3L enhanced T cell priming. Coexpression of IL-12 and GM-CSF induced the strongest CD4+ and CD8+ T cell responses through complimentary effects on the recruitment and activation of DCs, mediated by autocrine IL-12 receptor signaling in the Tvax. Therapeutic vaccination with Tvax and adjuvants showed antitumor activity in subcutaneous and metastatic preclinical mouse models. Human T cells modified with neoantigens readily activated specific T cells derived from patients, providing a path for clinical translation of this therapeutic platform in cancer.

Mobilization of pre-existing polyclonal T cells specific to neoantigens but not self-antigens during treatment of a patient with melanoma with bempegaldesleukin and nivolumab.

T cells that recognize self-antigens and mutated neoantigens are thought to mediate antitumor activity of immune checkpoint blockade (ICB) in melanoma. Few studies have analyzed self and neoantigen-specific T cell responses in patients responding to ICB. Here, we report a patient with metastatic melanoma who had a durable clinical response after treatment with the programmed cell death protein 1 inhibitor, nivolumab, combined with the first-in-class CD122-preferential interleukin-2 pathway agonist, bempegaldesleukin (BEMPEG, NKTR-214). We used a combination of antigen-specific T cell expansion and measurement of interferon-γ secretion to identify multiple CD4+ and CD8+ T cell clones specific for neoantigens, lineage-specific antigens and cancer testis antigens in blood and tumor from this patient prior to and after therapy. Polyclonal CD4+ and CD8+ T cells specific to multiple neoantigens but not self-antigens were highly enriched in pretreatment tumor compared with peripheral blood. Neoantigen, but not self-antigen-specific T cell clones expanded in frequency in the blood during successful treatment. There was evidence of dramatic immune infiltration into the tumor on treatment, and a modest increase in the relative frequency of intratumoral neoantigen-specific T cells. These observations suggest that diverse CD8+ and CD4+ T cell clones specific for neoantigens present in tumor before treatment had a greater role in immune tumor rejection as compared with self-antigen-specific T cells in this patient. Trial registration number: NCT02983045.

Age-Specific Incidence of Melanoma in the United States.

Importance: Melanoma is epidemiologically linked to UV exposure, particularly childhood sunburn. Public health campaigns are increasing sun-protective behavior in the United States, but the effect on melanoma incidence is unknown. Objective: To examine the incidence of melanoma in the United States and whether any age-specific differences are present. Design, Setting, and Participants: Observational, population-based registry data were extracted on July 3, 2018, from the combined National Program of Cancer Registries-Surveillance Epidemiology and End Results United States Cancer Statistics database for 2001-2015. Deidentified data for 988 103 cases of invasive melanoma, with International Classification of Diseases for Oncology histologic categorization codes 8720 to 8790, were used for analysis. Data analysis was performed from July 1, 2018, to March 1, 2019. Main Outcomes and Measures: The annual rates of melanoma in pediatric, adolescent, young adult, and adult age groups were determined. Analyses were stratified by sex, and incidence rates were age-adjusted to the 2000 US standard population. Annual percentage change (APC) in incidence rate was calculated over the most recent decade for which data were available (2006-2015) using the weighted least squares method. Results: In 2015, 83 362 cases of invasive melanoma were reported in the United States, including 67 in children younger than 10 years, 251 in adolescents (10-19 years), and 1973 in young adults (20-29 years). Between 2006 and 2015, the overall incidence rate increased from 200.1 to 229.1 cases per million person-years. In adults aged 40 years or older, melanoma rates increased by an APC of 1.8% in both men (95% CI, 1.4%-2.1%) and women (95% CI, 1.4%-2.2%). In contrast, clinically and statistically significant decreases were seen in melanoma incidence for adolescents and young adults. Specifically, incidence rates decreased by an APC of -4.4% for male adolescents (95% CI, -1.7% to -7.0%), -5.4% for female adolescents (95% CI, -3.3% to -7.4%), -3.7% for male young adults (95% CI, -2.5% to -4.8%), and -3.6% for female young adults (95% CI, -2.8% to -4.5%). Data on skin pigmentation and sun protection history were unavailable; similar trends were observed with data limited to non-Hispanic whites. Young adult women appeared to have twice the risk of melanoma as young adult men. Conclusions and Relevance: The incidence of invasive melanoma in the United States appeared to decrease in adolescents and young adults from 2006 to 2015, and this finding contrasted with increases in older populations. These incidence trends suggest that public health efforts may be favorably influencing melanoma incidence in the United States.

Endogenous CD4+ T Cells Recognize Neoantigens in Lung Cancer Patients, Including Recurrent Oncogenic KRAS and ERBB2 (Her2) Driver Mutations.

T cells specific for neoantigens encoded by mutated genes in cancers are increasingly recognized as mediators of tumor destruction after immune-checkpoint inhibitor therapy or adoptive cell transfer. Much of the focus has been on identifying epitopes presented to CD8+ T cells by class I MHC. However, CD4+ class II MHC-restricted T cells have been shown to have an important role in antitumor immunity. Unfortunately, the vast majority of neoantigens recognized by CD8+ or CD4+ T cells in cancer patients result from random mutations and are patient-specific. Here, we screened the blood of 5 non-small cell lung cancer (NSCLC) patients for T-cell responses to candidate mutation-encoded neoepitopes. T-cell responses were detected to 8.8% of screened antigens, with 1 to 7 antigens identified per patient. A majority of responses were to random, patient-specific mutations. However, CD4+ T cells that recognized the recurrent KRAS G12V and the ERBB2 (Her2) internal tandem duplication (ITD) oncogenic driver mutations, but not the corresponding wild-type sequences, were identified in two patients. Two different T-cell receptors (TCR) specific for KRAS G12V and one T-cell receptor specific for Her2-ITD were isolated and conferred antigen specificity when transfected into T cells. Deep sequencing identified the Her2-ITD-specific TCR in the tumor but not nonadjacent lung. Our results showed that CD4+ T-cell responses to neoantigens, including recurrent driver mutations, can be derived from the blood of NSCLC patients. These data support the use of adoptive transfer or vaccination to augment CD4+ neoantigen-specific T cells and elucidate their role in human antitumor immunity.

Tumor-infiltrating BRAFV600E-specific CD4+ T cells correlated with complete clinical response in melanoma.

T cells specific for neoantigens encoded by mutated genes in cancers are increasingly recognized as mediators of tumor destruction after immune checkpoint inhibitor therapy or adoptive cell transfer. Unfortunately, most neoantigens result from random mutations and are patient specific, and some cancers contain few mutations to serve as potential antigens. We describe a patient with stage IV acral melanoma who achieved a complete response following adoptive transfer of tumor-infiltrating lymphocytes (TILs). Tumor exome sequencing surprisingly revealed fewer than 30 nonsynonymous somatic mutations, including oncogenic BRAFV600E. Analysis of the specificity of TILs identified rare CD4+ T cells specific for BRAFV600E and diverse CD8+ T cells reactive to nonmutated self-antigens. These specificities increased in blood after TIL transfer and persisted long-term, suggesting they contributed to the effective antitumor immune response. Gene transfer of the BRAFV600E-specific T cell receptor (TCR) conferred recognition of class II MHC-positive cells expressing the BRAF mutation. Therapy with TCR-engineered BRAFV600E-specific CD4+ T cells may have direct antitumor effects and augment CD8+ T cell responses to self- and/or mutated tumor antigens in patients with BRAF-mutated cancers.

Mitochondrial dysfunction leads to nuclear genome instability via an iron-sulfur cluster defect.

Mutations and deletions in the mitochondrial genome (mtDNA), as well as instability of the nuclear genome, are involved in multiple human diseases. Here, we report that in Saccharomyces cerevisiae, loss of mtDNA leads to nuclear genome instability, through a process of cell-cycle arrest and selection we define as a cellular crisis. This crisis is not mediated by the absence of respiration, but instead correlates with a reduction in the mitochondrial membrane potential. Analysis of cells undergoing this crisis identified a defect in iron-sulfur cluster (ISC) biogenesis, which requires normal mitochondrial function. We found that downregulation of nonmitochondrial ISC protein biogenesis was sufficient to cause increased genomic instability in cells with intact mitochondrial function. These results suggest mitochondrial dysfunction stimulates nuclear genome instability by inhibiting the production of ISC-containing protein(s), which are required for maintenance of nuclear genome integrity. For a video summary of this article, see the PaperFlick file available with the online Supplemental Data.

Ku interacts with telomerase RNA to promote telomere addition at native and broken chromosome ends.

Ku is a conserved DNA end-binding protein that plays various roles at different kinds of DNA ends. At telomeres, Ku is part of the structure that protects the chromosome end, whereas at broken DNA ends, Ku promotes DNA repair as part of the nonhomologous end-joining (NHEJ) pathway. Here, we present evidence of a new role for Ku that impacts both telomere-length maintenance and DNA repair in Saccharomyces cerevisiae. We show that Ku binds TLC1, the RNA component of telomerase. We also describe a novel separation-of-function allele of Ku that is specifically defective in TLC1 binding. In this mutant, telomeres are short and the kinetics of telomere addition are slow, but other Ku-dependent activities, such as chromosome end protection and NHEJ, are unaffected. At low frequency, yeast will use telomerase to heal DNA damage by capping the broken chromosome with telomeric DNA sequences. We show that when Ku's ability to bind TLC1 is disrupted, DNA repair via telomere healing is reduced 10- to 100-fold, and the spectrum of sequences that can acquire a telomere changes. Thus, the interaction between Ku and TLC1 RNA enables telomerase to act at both broken and normal chromosome ends.