Current immunotherapy paradigms aim to reinvigorate CD8+ T cells, but the contribution of humoral immunity to antitumor immunity remains understudied. Here, we demonstrate that in head and neck squamous cell carcinoma (HNSCC) caused by human papillomavirus infection (HPV+), patients have transcriptional signatures of germinal center (GC) tumor infiltrating B cells (TIL-Bs) and spatial organization of immune cells consistent with tertiary lymphoid structures (TLS) with GCs, both of which correlate with favorable outcome. GC TIL-Bs in HPV+ HNSCC are characterized by distinct waves of gene expression consistent with dark zone, light zone and a transitional state of GC B cells. Semaphorin 4a expression is enhanced on GC TIL-Bs present in TLS of HPV+ HNSCC and during the differentiation of TIL-Bs. Our study suggests that therapeutics to enhance TIL-B responses in HNSCC should be prioritized in future studies to determine if they can complement current T cell mediated immunotherapies.

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Background: Low success rates in oncology drug development are prompting re-evaluation of preclinical models, including orthotopic tumor engraftment. In breast cancer models, tumor cells are typically injected into mouse mammary fat pads (MFP). However, this approach bypasses the epithelial microenvironment, potentially altering tumor properties in ways that affect translational application. Materials and Methods: Tumors were generated by mammary intraductal (MIND) engraftment of 4T1 carcinoma cells. Growth, histopathology, and molecular features were quantified. Results: Despite growth similar to that of 4T1 MFP tumors, 4T1 MIND tumors exhibit distinct histopathology and increased metastasis. Furthermore, >6,000 transcripts were found to be uniquely up-regulated in 4T1 MIND tumor cells, including genes that drive several cancer hallmarks, in addition to two known therapeutic targets that were not up-regulated in 4T1 MFP tumor cells. Conclusion: Engraftment into the epithelial microenvironment generates tumors that more closely recapitulate the complexity of malignancy, suggesting that intraductal adaptation of orthotopic mammary models may be an important step towards improving outcomes in preclinical drug screening and development.

Ovarian clear cell carcinoma (OCCC) is a deadly and treatment-resistant cancer which arises within the unique microenvironment of endometriosis. In this study, we identified a subset of endometriosis derived mesenchymal stem cells (enMSCs) characterized by loss of CD10 expression that specifically support OCCC growth. RNA sequencing identified alterations in iron export in CD10 negative enMSCs and reciprocal changes in metal transport in co-cultured OCCC cells. CD10 negative enMSCs exhibited elevated expression of iron export proteins hephaestin and ferroportin and donate iron to associated OCCCs, functionally increasing the levels of labile intracellular iron. Iron is necessary for OCCC growth, and CD10-negative enMSCs prevented the growth inhibitory effects of iron chelation. Additionally, enMSC-mediated increases in OCCC iron resulted in a unique sensitivity to ferroptosis. In vitro and in vivo, treatment with the ferroptosis inducer erastin resulted in significant death of cancer cells grown with CD10-negative enMSCs. Collectively, this work describes a novel mechanism of stromal-mediated tumor support via iron donation. This work also defines an important role of endometriosis-associated MSCs in supporting OCCC growth and identifies a critical therapeutic vulnerability of OCCC to ferroptosis based on stromal phenotype.