Head and neck squamous cell carcinoma (HNSCC) shows substantial intra- and inter-tumoral heterogeneity. We mapped tumor architecture across HPV-positive and HPV-negative HNSCC through spatial transcriptomics (n = 26). HPV-positive tumors display hypercellularity, higher lymphocyte presence, enriched hypoxia and reduced partial epithelial-to-mesenchymal transition (p-EMT) in malignant cells. We observed two distinct spatial architectures of p-EMT: p-EMT edge, where p-EMT is coupled to fibroblasts at the invasive front via TGFβ, and p-EMT core, in which tumor-infiltrating immunosuppressive macrophages and neutrophils induce p-EMT via oncostatin M in the core of tumor nests. These two p-EMT patterns were consistent across multiple samples from the same tumor, suggesting they are tumor-wide features. Together, these findings reveal that distinct interactions in the tumor microenvironment converge on a similar p-EMT cellular phenotype, but in a different spatial pattern that may have potential biological and clinical implications for our understanding of invasion, immune modulation and new targeted therapeutics for HNSCC.

In head and neck squamous cell carcinoma (HNSCC), immunotherapy response rates remain modest, with difficulty predicting responders. Previous studies characterizing immunotherapy-associated cellular changes in HNSCC focus on immune cells, providing limited insight into malignant cell responses. Here, we perform single-cell RNA sequencing (RNA-seq) on 16 HNSCC patients pre- and post-neoadjuvant pembrolizumab treatment. We identify an interferon (IFN)/major histocompatibility complex class II (MHC-II) expression program in malignant cells, characterized by MHC-II and IFN-response genes, which is associated with response to pembrolizumab. We validate malignant cell MHC-II expression at the protein level via multiplexed immunofluorescence. In a murine HNSCC model, IFN-γ-induced malignant cell MHC-II expression marks immunotherapy-sensitive tumors with favorable immune microenvironments. Finally, we confirm that pre-treatment malignant-IFN/MHC-II is a marker of response through deconvolution of bulk RNA-seq data from an independent cohort. Beyond identifying the malignant IFN/MHC-II program as a potential biomarker for immunotherapy response in HNSCC, our work elucidates the important role of malignant cells in immunotherapy.

Abstract Neuroblastoma (NB) and paraganglioma (PPGL) arise from the sympathoadrenal lineage, yet their developmental relationship and heterogeneity remain unclear. Single-cell and spatial transcriptomics revealed shared, spatially organized developmental states, including populations characteristic of the other tumor type, chromaffin-like cells in NB and neuroblast-like cells in PPGL and hybrids co-expressing adjacent states. Deconvolution of an independent PPGL cohort associated metastatic disease most strongly with chromaffin hybrid states, alongside connecting progenitor-like, cycling neuroblast, and early chromaffin identities, whereas non-metastatic tumors were enriched for differentiated late chromaffin identities. In mice, combined loss of the candidate 1p36 tumor suppressor KIF1Bβ and NF1 recapitulates these developmental architectures by prolonging developmental plasticity, reactivating embryonic neurogenic programs, and driving chromaffin-to-neuroblast transitions generating pheochromocytoma, neuroblastoma and composite tumors. Mouse tumors contained discrete spatial domains of developmental and neoplastic states that mirrored those in human PPGL. Together, our findings establish chromaffin-neuroblast plasticity as a mechanism of sympathoadrenal tumor heterogeneity and identify hybrid developmental states as a potential indicator of plasticity associated with metastatic PPGL.

Abstract Background: Single-cell RNA sequencing has revealed diverse malignant programs in head and neck squamous cell carcinoma (HNSCC), including partial epithelial-to-mesenchymal transition (p-EMT), a state linked to invasion and poor outcome. However, how p-EMT is spatially organized within tumors and shaped by the tumor microenvironment (TME) remains unclear. Here, we used spatial transcriptomics to define tumor-wide spatial architectures of p-EMT in HPV-positive and HPV-negative HNSCC and to identify their microenvironmental drivers. Methods: We profiled 26 primary HNSCC tumors (18 HPV-negative, 8 HPV-positive) using 10x Visium spatial transcriptomics, with paired single-cell RNA-seq for 11 tumors. Cell states were defined using consensus expression meta-programs, and malignant regions were identified via inferred copy number aberrations. Spatial interactions were quantified using distance-based neighborhood analyses, and malignant regions were stratified into tumor edge and core compartments. Key findings were validated using high-resolution Visium HD on paired sections, 25-plex CODEX spatial proteomics in an independent cohort of 40 laryngeal squamous cell carcinomas, and cytokine perturbation assays in vitro. Results: HPV-positive tumors exhibited increased cellular density, an immune-enriched microenvironment, and malignant programs consistent with hypoxia, alongside relative depletion of p-EMT. In contrast, HPV-negative tumors showed prominent p-EMT that segregated into two distinct spatial architectures. The canonical p-EMT edge pattern localized to the invasive front, where p-EMT malignant cells spatially coupled to fibroblasts through TGFβ-associated signaling. Notably, we identified an alternative p-EMT core architecture characterized by diffuse p-EMT throughout tumor cores and co-localization with immunosuppressive macrophages and neutrophils. This spatial niche-related transcriptional program was associated with worse overall survival in large external cohorts. Ligand-receptor analyses and in vitro validations implicated oncostatin M (OSM) as a key upstream driver of p-EMT in tumor cores. Both Visium HD and CODEX independently confirmed the spatial organization of p-EMT states and the corresponding TME interactions. Notably, both p-EMT architectures were consistent across multiple samples from the same tumor, indicating tumor-wide organizational states rather than region-specific variability. Conclusions: We identify two tumor-wide p-EMT architectures in HNSCC driven by distinct microenvironmental programs: fibroblast-derived TGFβ at tumor edges and myeloid-derived OSM in tumor cores. These findings establish OSM as a novel regulator of p-EMT and suggest spatially organized EMT programs as clinically relevant determinants of tumor aggressiveness, with potential implications across cancer types. Citation Format: Dor Simkin, Thomas F. Barrett, Lingling Zhang, Michael J. Moore, Alissa R. Greenwald, Noam Darnell, Michael Mints, Salma Ramadan, Victoria Yu, Riley DZ Mullins, Jesse Zaretsky, Porter Bischoff, Douglas Adkins, Wade L. Thorstad, Sana D. Karam, Randall C. Paniello, Jason T. Rich, Ryan S. Jackson, Patrik Pipkorn, Paul A. Zolkind, Guangyong Peng, R. Alex Harbison, Rebecca Chernock, Anuraag S. Parikh, Sidharth V. Puram, Itay Tirosh. Spatial analysis of head and neck cancer reveals two ecosystems with distinct modes of epithelial-to-mesenchymal transition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(8_Suppl):Abstract nr LB163.

Recent years have seen a rapid proliferation of single-cell cancer studies, yet most of these studies profiled few tumors, limiting their statistical power. Combining data and results across studies holds great promise but also involves various challenges. We recently began to address these challenges by curating a large collection of cancer single-cell RNA-sequencing datasets, leveraging it for systematic analyses of tumor heterogeneity. Here we greatly extend this repository to 124 datasets for over 40 cancer types, together comprising 2,836 samples, with improved data annotations, visualizations and exploration. Using this vast cohort, we generate an updated map of recurrent expression programs in malignant cells and systematically quantify context-dependent gene expression and cell-cycle patterns across cell types and cancer types. These data, annotations and analysis results are all freely available for exploration and download through the Curated Cancer Cell Atlas, a central community resource that opens new avenues in cancer research. Tyler et al. introduce a curated collection of 124 multicancer, single-cell RNA-sequencing datasets with 2,836 samples and present recurrent cancer cell expression metaprograms, quantifying context-dependent expression and proliferation across cell and cancer types.

Human papillomavirus (HPV)-related multiphenotypic sinonasal carcinoma (HMSC) is a rare tumor that morphologically resembles high-grade adenoid cystic carcinoma (ACC) but exhibits indolent clinical behavior. Both demonstrate MYB proto-oncogene upregulation, though HMSC lacks the MYB translocation characteristic of ACC. We performed single-cell RNA sequencing on an HMSC tumor and compared expression patterns with published ACC and oropharyngeal squamous cell carcinoma (OPSCC) datasets. Malignant HMSC cells clustered separately from ACC and lacked bicellular luminal and myoepithelial differentiation. A greater proportion of HMSC cells expressing HPV-related genes (HPVon) expressed MYB (83% vs. 62%, p = 0.022) and MYB targets (p = 6.4 × 10−6), supporting an HPV-MYB association. Validation in HPV + OPSCC revealed MYB upregulation in HPVon cells from 7/10 tumors (p < 0.05). A 264-gene signature from HPVon HMSC cells correlated with worse prognosis in HPV + OPSCC (p < 0.003), suggesting an alternate role for HPV. Further validation of the HPV-MYB association and gene signature may improve therapeutic strategies in HPV-related malignancies.

Single-cell RNA-seq (scRNA-seq) has transformed the study of cancer biology. Recent years have seen a rapid expansion in the number of single-cell cancer studies, yet most of these studies profiled few tumours, such that individual datasets have limited statistical power. Combining the data and results across studies holds great promise but also involves various challenges. We recently began to address these challenges by curating a large collection of cancer scRNA-seq datasets, and leveraging it for systematic analyses of tumor heterogeneity. Here we significantly extend this repository to 124 datasets for over 40 cancer types, together comprising 2,822 samples, with improved data annotations, visualisations and exploration. Utilising this vast cohort, we systematically quantified context-dependent gene expression and proliferation patterns across cell types and cancer types. These data, annotations and analysis results are all freely available for exploration and download via the Curated Cancer Cell Atlas (3CA) website (https://www.weizmann.ac.il/sites/3CA/), a central source of data and analyses for the cancer research community that opens new avenues in cancer research. ### Competing Interest Statement Itay Tirosh is an advisory board member of Immunitas Therapeutics.

Head and neck squamous cell carcinoma (HNSCC) includes a subset of cancers driven by human papillomavirus (HPV). Here we use single-cell RNA-seq to profile both HPV-positive and HPV-negative oropharyngeal tumors, uncovering a high level of cellular diversity within and between tumors. First, we detect diverse chromosomal aberrations within individual tumors, suggesting genomic instability and enabling the identification of malignant cells even at pathologically negative margins. Second, we uncover diversity with respect to HNSCC subtypes and other cellular states such as the cell cycle, senescence and epithelial-mesenchymal transitions. Third, we find heterogeneity in viral gene expression within HPV-positive tumors. HPV expression is lost or repressed in a subset of cells, which are associated with a decrease in HPV-associated cell cycle phenotypes, decreased response to treatment, increased invasion and poor prognosis. These findings suggest that HPV expression diversity must be considered during diagnosis and treatment of HPV-positive tumors, with important prognostic ramifications.

Each tumour contains diverse cellular states that underlie intratumour heterogeneity (ITH), a central challenge of cancer therapeutics(1). Dozens of recent studies have begun to describe ITH by single-cell RNA sequencing, but each study typically profiled only a small number of tumours and provided a narrow view of transcriptional ITH2. Here we curate, annotate and integrate the data from 77 different studies to reveal the patterns of transcriptional ITH across 1,163 tumour samples covering 24 tumour types. Among the malignant cells, we identify 41 consensus meta-programs, each consisting of dozens of genes that are coordinately upregulated in subpopulations of cells within many tumours. The meta-programs cover diverse cellular processes including both generic (for example, cell cycle and stress) and lineage-specific patterns that we map into 11 hallmarks of transcriptional ITH. Most meta-programs of carcinoma cells are similar to those identified in non-malignant epithelial cells, suggesting that a large fraction of malignant ITH programs are variable even before oncogenesis, reflecting the biology of their cell of origin. We further extended the meta-program analysis to six common non-malignant cell types and utilize these to map cell-cell interactions within the tumour microenvironment. In summary, we have assembled a comprehensive pan-cancer single-cell RNA-sequencing dataset, which is available through the Curated Cancer Cell Atlas website, and leveraged this dataset to carry out a systematic characterization of transcriptional ITH.

To identify predictive/targetable markers in human papillomavirus positive (HPV+) tonsillar and base of tongue cancer (TSCC/BOTSCC), whole-exome sequencing (WES) of tumours of patients with/without recurrence was performed. Forty primary tumours and adjacent normal tissue were separated by micro-dissection from formalin-fixed paraffin-embedded tissue from patients treated with curative intent 2000–2014 at Karolinska University Hospital. Successful sequencing was obtained in primary tumours of 18 patients without and primaries of 17 with local or distant recurrence, as well as in 10 corresponding recurrences (i.e., five local relapses and five distant metastases) from these 17 patients. One variant—a high-impact deletion in the CDC27 gene—was observed only in primaries of 5/17 patients that had a recurrence after full treatment but in none of those without recurrence. In addition, 3 variants and 26 mutated genes, including CDC27, BCLAF1 and AQP7, were present in at least 30% of all primary tumours independent of prognosis. To conclude, a CDC27 deletion was specific and found in ~30% of samples from patients with a local relapse/distant metastasis and could, therefore, potentially be a prospective marker to predict prognosis. Commonly mutated genes, such as BCLAF1, should be further studied in the context of targeted therapy.

Each tumor contains malignant cells that differ in genotype, phenotype, and in their interactions with the tumor micro-environment (TME). This results in distinct integrated cellular states that govern intra-tumor heterogeneity (ITH), a central challenge of cancer therapeutics. Dozens of recent studies have begun to describe ITH by single cell RNA-seq, but each study typically profiledonly a small number of tumors and provided a narrow view of transcriptional ITH. Here, we curate, annotate and integrate the data from 77 different studies to reveal the patterns of ITH across 1,163 tumor samples covering 24 tumor types. Focusing on the malignant cells, we find thousands of transcriptional ITH programs that can be described by 41 consensus meta-programs (MPs), each consisting of dozens of genes that are coordinately upregulated in subpopulations of cells within many different tumors. The MPs cover diverse cellular processes and differ in their cancer-type distribution. General MPs associated with processes such as cell cycle and stress vary within most tumors, while context-specific MPs reflect the unique biology of particular cancer types, often resembling developmental cell types and suggesting the co-existence of variable differentiation states within tumors. Some of the MPs are further associated with overall tumor proliferation or immune state, highlighting their potential clinical significance. Based on functional similarities among MPs, we propose a set of 11 hallmarks that together account for the majority of observed ITH programs. Given the breadth and scope of the investigated cohort, the MPs and hallmarks described here reflect the first comprehensive pan-cancer description of transcriptional ITH.

Invasive urothelial bladder cancer (UBC) has high recurrence rates even after radical cystectomy (RC). Exosomes are membrane-bound nanovesicles, which have been shown to contribute to carcinogenesis and metastasis. We previously showed that urinary exosomes display a malignant profile in UBC patients despite the absence of detectable tumour. Here, we investigated exosomes from sampling sites close to or distant from the former tumour, aiming to understand the effect of the tumour on the local milieu. Ten patients scheduled for cystectomy after transurethral bladder resection (TUR-B), without remaining detectable tumour, were included. Exosomes were isolated from tissue explants of both the previous tumour site and distant bladder tissue. Proteins were quantified by mass spectrometry in seven patients. Exosomes from the previous tumour site were enriched in inflammatory but not cancer-related pathways compared to distant tissue. However, the 69 most abundant proteins in tissue-derived exosomes regardless of site, 20 of which were also found in urinary exosomes from our previous study, were enriched for cancer-related metabolic pathways and associated with poor prognosis in an external mRNA dataset. The enrichment of cancer-related pathways in the most abundant proteins, regardless of sampling site, confirms our hypothesis that despite the absence of detectable tumour, the entire bladder releases exosomes that contribute to metastasis and highlights the need for early RC.

Complexities in cell-type composition have rightfully led to skepticism and caution in the interpretation of bulk transcriptomic analyses. Recent studies have shown that deconvolution algorithms can be utilized to computationally estimate cell-type proportions from the gene expression data of bulk blood samples, but their performance when applied to tumor tissues, including those from head and neck, remains poorly characterized. Here, we use single-cell data (~6000 single cells) collected from 21 head and neck squamous cell carcinoma (HNSCC) samples to generate cell-type-specific gene expression signatures. We leverage bulk RNA-seq data from >500 HNSCC samples profiled by The Cancer Genome Atlas (TCGA), and using single-cell data as a reference, apply two newly developed deconvolution algorithms (CIBERSORTx and MuSiC) to the bulk transcriptome data to quantitatively estimate cell-type proportions for each tumor in TCGA. We show that these two algorithms produce similar estimates of constituent/major cell-type proportions and that a high T-cell fraction correlates with improved survival. By further characterizing T-cell subpopulations, we identify that regulatory T-cells (Tregs) were the major contributor to this improved survival. Lastly, we assessed gene expression, specifically in the Treg population, and found that TNFRSF4 (Tumor Necrosis Factor Receptor Superfamily Member 4) was differentially expressed in the core Treg subpopulation. Moreover, higher TNFRSF4 expression was associated with greater survival, suggesting that TNFRSF4 could play a key role in mechanisms underlying the contribution of Treg in HNSCC outcomes.

Hypopharyngeal squamous cell carcinoma (HPSCC) has a very poor prognosis. Local surgery may increase survival, but is often avoided due to significant post-op co-morbidities. Since prognostic markers are lacking, the aim was to find predictive biomarkers that identify patients whose response to oncological treatment is poor and who may benefit from primary surgery to increase survival. Pretreatment biopsies from 23 HPSCC patients, 3 human papillomavirus (HPV) positive and 20 HPV-negative, were analyzed for expression of 750 mRNAs using the Nanostring nCounter IO360 panel in relation to 3-year survival. Validation was performed through immunohistochemistry (IHC) for HLA class I and S100A12 in 74 HPV-negative HPSCC samples. Clustering identified a subset of HPV-negative HPSCC with favorable prognosis and a gene expression signature overexpressing calgranulins and immune genes, distinct from that of HPV-positive HPSCC. Enrichment analysis showed immune signaling, including the tumor inflammation signature, to be enriched in surviving patients. IHC validation confirmed high S100A12 and HLA class I expression to correlate with survival in HPV-negative HPSCC. This shows that immune activity is strongly related to survival in HPV-negative HPSCC. Enrichment of the tumor inflammation signature indicates a potential benefit of immunotherapy. Low expression of both HLA class I and S100A12 could be used to select patients for local surgery.

In the effort of developing new immunotherapies, the sentinel node (SN) has proven a promising source from which to harness an effective antitumour T cell response. However, tumour immune escape, a process in which regulatory T cells (Tregs) play a central role, remains a major limiting factor. Therefore, there is a clear need to increase the knowledge of Treg function and signalling in sentinel nodes. Here, we set out to explore whether the proteome in SN‐resident T cells is altered by the tumour and to identify key proteins in SN T cell signalling, focusing on Tregs. Five patients with muscle‐invasive urothelial bladder cancer were prospectively included. Mass spectrometry was performed on two patients, with validation and functional studies being performed on three additional patients and four healthy donors. At cystectomy, SN, non‐SN lymph nodes and peripheral blood samples were collected from the patients and T cell subsets isolated through flow cytometry before downstream experiments. Proteomic analysis indicated that growth and immune signalling pathways are upregulated in SN‐resident Tregs. Furthermore, centrality analysis identified the cytokine IL‐16 to be central in the SN‐Treg signalling network. We show that tumour‐released factors, through activating caspase‐3, increase Treg IL‐16 processing into bioactive forms, reinforcing Treg suppressive capacity. In conclusion, we provide evidence that Tregs exposed to secreted factors from bladder tumours show increased immune and growth signalling and altered IL‐16 processing which translates to enhanced Treg suppressive function, indicating altered IL‐16 signalling as a novel tumour immune escape mechanism.

BACKGROUND:Hypopharyngeal cancer (HPSCC) shows a poor clinical outcome, while HPSCC, caused by human papillomavirus (HPV), presents a better outcome. Here, HPCC, immune proteins, and tumor infiltrating CD8+ lymphocytes (CD8+ TILs) were evaluated in relation to HPV and outcome.METHODS:Fresh frozen tissue from four HPV-positive HPSCC, 39 HPV-negative HPSCC, and normal samples were analyzed for protein expression by the Proseek immuno-oncology immunoassay. CD8+ TIL numbers evaluated by immunohistochemistry on 144 formalin-fixed biopsies were analyzed in relation to clinical outcome.RESULTS:Proteins differing between HPV-positive and negative HPSCC included CD8A, PD-L1, Fas ligand, and chemokines. High CD8+ TIL numbers were correlated to improve clinical outcome in HPV-negative HPSCC.CONCLUSIONS:High expression of immune proteins in HPV-positive HPSCC may explain the better clinical outcome. CD8+ TILs are of relevance for outcome of HPV-negative HPSCC, while tumors with high immune activity but poor patient survival suggest a role for immune therapy.

Next-generation sequencing has revolutionized cancer research, providing large-scale molecular characterizations for all common cancer types and contributing to personalized medicine through understanding of inter-tumor heterogeneity [1,2]. Exemplified by the cancer genome atlas (TCGA), these studies uncovered driver mutations and divided each cancer type into subtypes with distinct molecular features and clinical characteristics, such as survival and treatment response [3]. However, these studies, which largely considered each tumor as an individual “bulk” sample, are insufficient for characterizing the diversity of cells within a tumor. Such diversity includes the various immune and stromal cell types as well as the multitude of cellular states among neoplastic cells, which collectively underlie tumor biology and clinical behavior. The advent of single-cell technologies, such as singlecell RNA sequencing (scRNA-Seq), overcomes this weakness and heralds a new revolution in cancer research [4-6]. Several cancer types have already been profiled by large-scale scRNA-Seq studies, providing a cellular view of their composition and diversity, and further clarifying previous observations. For example, subtypes identified previously by TCGA are now refined and their underlying basis have been revealed [6]. This is a rapidly developing field, and in the coming years we can expect single-cell atlases to be published for most cancer types, and a

Invasive urinary bladder cancer shows high recurrence rates after cystectomy even with apparent complete downstaging at cystectomy. Exosomes are nano-sized vesicles important in cell-cell communication, which have been hypothesized to contribute to cancer dissemination and recurrence. The aim of this study was to investigate if pro-carcinogenic exosomes could be detected in urine from histologically downstaged bladder cancer patients. 13 Patients were included in this study. Paired ureter and urine samples from nine patients underwent mass spectrometry, while samples from the remaining patients were used for exosome characterization. At cystectomy, exosomes were isolated from bladder and ureter urine, whereafter quantitative proteome profiling was performed. Urinary exosomes clustered based on whether they came from the bladder, with tumour contact, or the ureters, without tumour contact, even though all came from completely downstaged patients. Proteins overexpressed in exosomes derived from bladder urine contained several oncogenes and were mainly associated with tumour metabolism pathways. Although patients were histologically tumour-free at cystectomy, the bladder urine contained exosomes with a carcinogenic metabolic profile. This suggests a continuous release of exosomes from the bladder, which may promote recurrence at distant sites through metabolic rewiring, even after apparent complete downstaging. These exosomes, coming from either undetected cancer cells or partly transformed cells, are likely to increase the risk of metastasis and encourages cystectomy even in completely downstaged patients.

INTRODUCTION:In recent years, immunotherapy for the treatment of solid cancer has emerged as a promising therapeutic alternative. Adoptive cell therapy (ACT), especially T cell-based, has been found to cause tumor regression and even cure in a percentage of treated patients. Checkpoint inhibitors further underscore the potential of the T cell compartment in the treatment of cancer. Not all patients respond to these treatments; however, many challenges remain.AREAS COVERED:This review covers the challenges and progress in tumor antigen target identification and selection, and cell product manufacturing for T cell ACT. Tumor immune escape mechanisms and strategies to overcome those in the context of T cell ACT are also discussed.EXPERT OPINION:The immunotherapy toolbox is rapidly expanding and improving, and the future promises further breakthroughs in the T cell ACT field. The heterogeneity of the tumor microenvironment and the multiplicity of tumor immune escape mechanisms pose formidable challenges to successful T cell immunotherapy in solid tumors, however. Individualized approaches and strategies combining treatments targeting different immunotherapeutic aspects will be needed in order to expand the applicability and improve the response rates in future.