Febres-Aldana, C. | bioRxiv Science

bioRxiv2026

Spatially Organized Tertiary Lymphoid Structures Emerge in Small Cell Lung Cancer and Associate with Improved Survival

Tertiary lymphoid structures (TLS) are ectopic immune aggregates associated with improved prognosis and response to immunotherapy in multiple solid tumors. However, their presence, spatial organization, and functional relevance in small cell lung cancer (SCLC), a malignancy characterized by profound immune evasion, remain poorly understood. Using imaging mass cytometry (IMC) across 320 regions of interest spanning primary lung tumor, tumor-adjacent lung, liver and lymph node metastasis, complemented by Visium HD spatial transcriptomics, we characterized the cellular architecture and molecular programs of TLS-like niches in SCLC. TLS-like niches were identified in a subset of SCLC samples, predominantly primary lung tumor tissues and adjacent lung, spanning a continuum from loose lymphoid aggregates to compact follicle-like immune structures. Organized TLS-like niches contained CD20+ B-cell cores, closely associated with CD4+ and CD8A+ T cells, proliferating lymphocytes, HLA-DR+ antigen-presenting compartments, and SMA+ stromal scaffolds, and were enriched for canonical TLS organizer signals (CXCL13, LTB, FDCSP). Patients with TLS-positive tumors demonstrated improved overall survival, and core TLS-associated transcriptional programs were associated with favorable survival in an independent bulk RNA-seq cohort. To our knowledge, this represents one of the first spatially resolved analyses of TLS-like immune architecture in SCLC, demonstrating that organized lymphoid immunity can emerge in this classically immune-evasive disease and is associated with improved survival.

cancer biology↗

bioRxiv2025

RRAS and RRAS2 mutations are oncogenic drivers in lung cancer and are sensitive to the pan-RAS inhibitor RMC-6236

IntroductionRRAS and RRAS2 encode a subfamily of RAS-like small GTPases that share considerable structural and functional similarities with KRAS, HRAS, and NRAS. Whether homologous RRAS/RRAS2 mutations are oncogenic and actionable drivers in lung cancer remains underexplored. MethodsAn institutional cohort of 8,488 non-small cell lung carcinomas (NSCLC) sequenced by comprehensive targeted DNA sequencing (MSK-IMPACT) between 2016-2024 was evaluated for RRAS/RRAS2 mutations. RRASQ87L or RRAS2Q72L were modeled in murine IL3-dependent Ba/F3 cells and immortalized human bronchiolar epithelial cells (HBECs). The oncogenic potential, signaling characteristics, and sensitivity to PI3K and MAPK pathway inhibitors, including the novel pan-RAS inhibitor RMC-6236, were evaluated in vitro and in vivo. ResultsRRASQ87L or RRAS2Q72L, homologous to KRAS-codon Q61 substitutions, were found in [~]0.45% of NSCLCs (38/8,488), with all but two lacking other MAPK pathway oncogenic drivers. RRASQ87L and RRAS2Q72L mutations transformed Ba/F3 and HBEC cells and robustly activated MAPK and PI3K-mTOR pathway signaling. RMC-6236 suppressed proliferation of RRASQ87L and RRAS2Q72L mutant cell lines, reduced ERK phosphorylation, induced apoptosis, and impeded cell-cycle progression. In vivo, RMC-6236 significantly inhibited growth of RRASQ87L/RRAS2Q72L-mutant HBEC-derived xenografts. ConclusionsRRASQ87L and RRAS2Q72L are recurrent, oncogenic, and potentially actionable drivers in NSCLC. Our study supports the inclusion of RRAS/RRAS2 into routine molecular diagnostic panels for precision oncology and provides preclinical rationale for investigating the potential therapeutic utility of pan-RAS inhibitors for patients with RRASQ87L/RRAS2Q72L-mutant lung cancers. Statement of translational relevanceTargeted therapies have transformed standard of care for oncogene-driven non-small cell lung carcinomas (NSCLC), yet a significant subset lacks actionable drivers. We identified recurrent RRASQ87L and RRAS2Q72L mutations which are mutually exclusive with other MAPK pathway drivers and found in [~]0.45% of NSCLC, comparable in prevalence to NTRK and NRG1 fusions. In preclinical models, these mutations activate canonical growth signaling, drive tumorigenic phenotypes, and confer sensitivity to RAS/MAPK-directed agents, including the novel pan-RAS inhibitor RMC-6236, currently in trials for patients with solid tumors harboring KRAS mutations. These data support RRASQ87L and RRAS2Q72L as bona fide lung cancer drivers and nominate RRAS/RRAS2-mutant tumors as candidates for pan-RAS-targeted therapeutics. Our findings provide a biologic rationale and preclinical evidence to inform molecular testing paradigms and to prioritize enrollment of patients with RRAS/RRAS2-mutant NSCLC into future clinical trials of pan-RAS inhibitors.

cancer biology↗