Loss-of-function mutations of JAK1/2 impair cancer cell responsiveness to IFNγ and immunogenicity. Therefore, an understanding of compensatory pathways to activate IFNγ signaling in cancer cells is clinically important for the success of immunotherapy. Here we demonstrate that the transcription factor SOX10 hinders immunogenicity of melanoma cells through the IRF4–IRF1 axis. Genetic and pharmacologic approaches revealed that SOX10 repressed IRF1 transcription via direct induction of a negative regulator, IRF4. The SOX10–IRF4–IRF1 axis regulated PD-L1 expression independently of JAK–STAT pathway activity, and suppression of SOX10 increased the efficacy of combination therapy with an anti-PD-1 antibody and histone deacetylase inhibitor against a clinically relevant melanoma model. Thus, the SOX10–IRF4–IRF1 axis serves as a potential target that can bypass JAK-STAT signaling to immunologically warm up melanoma with a "cold" tumor immune microenvironment. Significance: This study identifies a novel SOX10/IRF4 pathway that regulates noncanonical induction of IRF1 independent of the JAK–STAT pathway and can be targeted to improve the efficacy of anti-PD-1 therapy in melanoma.

Understanding the epigenomic evolution and specificity of disease subtypes from complex patient data remains a major biomedical problem. We here present DeCET (decomposition and classification of epigenomic tensors), an integrative computational approach for simultaneously analyzing hierarchical heterogeneous data, to identify robust epigenomic differences among tissue types, differentiation states, and disease subtypes. Applying DeCET to our own data from 21 uterine benign tumor (leiomyoma) patients identifies distinct epigenomic features discriminating normal myometrium and leiomyoma subtypes. Leiomyomas possess preponderant alterations in distal enhancers and long-range histone modifications confined to chromatin contact domains that constrain the evolution of pathological epigenomes. Moreover, we demonstrate the power and advantage of DeCET on multiple publicly available epigenomic datasets representing different cancers and cellular states. Epigenomic features extracted by DeCET can thus help improve our understanding of disease states, cellular development, and differentiation, thereby facilitating future therapeutic, diagnostic, and prognostic strategies.

The use of microRNAs as biomarkers has been proposed for many diseases including the diagnosis of melanoma. Although hundreds of microRNAs have been identified as differentially expressed in melanomas as compared to benign melanocytic lesions, limited consensus has been achieved across studies, constraining the effective use of these potentially useful markers. In this study we quantified microRNAs by next-generation sequencing from melanomas and their adjacent benign precursor nevi. We applied a machine learning-based pipeline to identify a microRNA signature that separated melanomas from nevi and was unaffected by confounding variables, such as patient age and tumor cell content. By employing the ratios of microRNAs that were either enriched or depleted in melanoma compared to nevi as a normalization strategy, the classifier performed similarly across multiple published microRNA datasets, obtained by microarray, small RNA sequencing, or RT-qPCR. Validation on separate cohorts of melanomas and nevi correctly classified lesions with 83% sensitivity and 71-83% specificity, independent of variation in tumor cell content of the sample or patient age.

Background: Chromosome 3p (chr3p) is frequently deleted in multiple cancers, indicating the presence of shared tumor suppressors. In aggressive uveal melanomas (UVM), this deletion often co-occurs with chr8q amplification (8q+), suggesting strong selection pressure during UVM evolution. Methods: To understand the pattern of genomic alterations mediated by chr3p deletion, we have developed an algorithm for detecting isochromosomes in 10,632 TCGA cancer patients. We further perform integrative genomics analysis to investigate how chr3p deletion could affect subsequent cancer genome evolution and synthetic lethality in UVM. Results: Analysis of genomic alterations in 33 different cancer types implicates the deletion or deleterious mutations of SET-domain-containing 2 (SETD2) at chr3p21 in significantly facilitating the formation of isochromosomes, thereby promoting genomic instability conducive to rapid cancer genome evolution. Fracturing of dicentric isochromosomes during cell division is pervasive and follows the dynamic fragmentation pattern of solids under impulse. In the most aggressive UVM subtype, chr3 deletion includes MITF, a master regulator of melanocyte survival and differentiation, and co-occurs with 8q+. We demonstrate that MITF is a master transcriptional regulator of GNAQ/GNA11 and associated synthetic-lethal genes in UVM. MITF maintains MAPK and calcium homeostasis in UVM, and its hemizygous deletion is thus accidental, likely creating an early crisis during oncogenesis. We further show that MITF, MYC, and GNAQ/GNA11 form coupled regulatory feedback loops in the melanocyte lineage, and MITF deletion in UVM creates acute dependency on MYC-mediated rescue via 8q+. The discovered feedback loops predict both overall and relapse-free patient survival within the most aggressive UVM subtype, explain sensitivity to therapeutic gene perturbations, and inform effective combinatorial therapies. Conclusions: SETD2 deletion potentiates isochromosome formation across diverse cancers. Combinatorial targeting of MITF together with a previously identified synthetic lethal gene may benefit UVM patients harboring both chr3 deletion and 8q+.

Chromosome 3p (chr3p) is frequently deleted in multiple cancers, indicating the presence of shared tumor suppressors. Analysis of genomic alterations in 33 different cancer types implicates the deletion or deleterious mutations of SET-domain-containing 2 ( SETD2 ) at chr3p21 in significantly facilitating the formation of isochromosomes, consisting of two identical mirror-imaged arms, thereby promoting genomic instability conducive to large-scale chromosomal rearrangements and rapid cancer genome evolution. Fracturing of dicentric isochromosomes during cell division is pervasive and follows the dynamic fragmentation pattern of solids under impulse. Across cancers, isochromosomes form most frequently on chr8 to amplify the MYC -containing q-arm and chr17 to delete the TP53 -containing p-arm. In the most aggressive uveal melanoma (UVM) subtype, chr3 deletion also includes MITF , a critical melanocyte differentiation and survival factor, and co-occurs with chr8q amplification. We demonstrate that MITF is a master transcriptional regulator of GNAQ / GNA11 , mutated in 90% of UVM patients, and the associated synthetic-lethal genes identified by recent CRISPR screening studies. MITF maintains MAPK and calcium homeostasis in UVM, and its deletion is thus accidental, creating an early crisis during oncogenesis. We further show that MITF, MYC, and GNAQ/GNA11 form coupled regulatory feedback loops in the melanocyte lineage, and MITF deletion in UVM creates acute dependency on MYC-mediated rescue via chr8q amplification, often as a consequence of isochromosome formation. The discovered feedback loops predict both overall and relapse-free patient survival within the most aggressive UVM subtype, explain sensitivity to therapeutic gene perturbations, and inform effective combinatorial therapies.