Human IL-6 fosters long-term engraftment of patient-derived disease-driving myeloma cells in immunodeficient mice.

Multiple myeloma is a largely incurable and life-threatening malignancy of antibody-secreting plasma cells. An effective and widely available animal model that recapitulates human myeloma and related plasma cell disorders is lacking. We show that busulfan-conditioned human IL-6-transgenic (hIL-6-transgenic) NSG (NSG+hIL6) mice reliably support the engraftment of malignant and premalignant human plasma cells, including from patients diagnosed with monoclonal gammopathy of undetermined significance, pre- and postrelapse myeloma, plasma cell leukemia, and amyloid light chain amyloidosis. Consistent with human disease, NSG+hIL6 mice engrafted with patient-derived myeloma cells developed serum M spikes, and a majority developed anemia, hypercalcemia, and/or bone lesions. Single-cell RNA sequencing showed nonmalignant and malignant cell engraftment, the latter expressing a wide array of mRNAs associated with myeloma cell survival and proliferation. Myeloma-engrafted mice given CAR T cells targeting plasma cells or bortezomib experienced reduced tumor burden. Our results establish NSG+hIL6 mice as an effective patient-derived xenograft model for study and preclinical drug development of multiple myeloma and related plasma cell disorders.

Human IL-6 fosters long-term engraftment of patient derived disease-driving myeloma cells in immunodeficient mice.

Multiple myeloma is a largely incurable and life-threatening malignancy of antibody-secreting plasma cells. An effective and widely available animal model that recapitulates human myeloma and related plasma cell disorders is lacking. We show that busulfan-conditioned hIL-6 transgenic NSG mice (NSG+hIL6) reliably support the engraftment of malignant and pre-malignant human plasma cells including from patients diagnosed with monoclonal gammopathy of undetermined significance, pre- and post-relapse myeloma, plasma cell leukemia, and AL amyloidosis. Consistent with human disease, NSG+hIL6 mice engrafted with patient-derived myeloma cells, developed serum M spikes, and a majority developed anemia, hypercalcemia, and/or bone lesions. Single cell RNA sequencing showed non-malignant and malignant cell engraftment, the latter expressing a wide array of mRNAs associated with myeloma cell survival and proliferation. Myeloma engrafted mice given CAR T-cells targeting plasma cells or bortezomib experienced reduced tumor burden. Our results establish NSG+hIL6 mice as an effective patient derived xenograft model for study and preclinical drug development of multiple myeloma and related plasma cell disorders.

Quantitative immunopeptidomics reveals a tumor stroma-specific target for T cell therapy.

T cell receptor (TCR)-based immunotherapy has emerged as a promising therapeutic approach for the treatment of patients with solid cancers. Identifying peptide-human leukocyte antigen (pHLA) complexes highly presented on tumors and rarely expressed on healthy tissue in combination with high-affinity TCRs that when introduced into T cells can redirect T cells to eliminate tumor but not healthy tissue is a key requirement for safe and efficacious TCR-based therapies. To discover promising shared tumor antigens that could be targeted via TCR-based adoptive T cell therapy, we employed population-scale immunopeptidomics using quantitative mass spectrometry across ~1500 tumor and normal tissue samples. We identified an HLA-A*02:01-restricted pan-cancer epitope within the collagen type VI α-3 (COL6A3) gene that is highly presented on tumor stroma across multiple solid cancers due to a tumor-specific alternative splicing event that rarely occurs outside the tumor microenvironment. T cells expressing natural COL6A3-specific TCRs demonstrated only modest activity against cells presenting high copy numbers of COL6A3 pHLAs. One of these TCRs was affinity-enhanced, enabling transduced T cells to specifically eliminate tumors in vivo that expressed similar copy numbers of pHLAs as primary tumor specimens. The enhanced TCR variants exhibited a favorable safety profile with no detectable off-target reactivity, paving the way to initiate clinical trials using COL6A3-specific TCRs to target an array of solid tumors.

Type III Collagen Directs Stromal Organization and Limits Metastasis in a Murine Model of Breast Cancer.

Breast cancer metastasis is the leading cause of cancer-related deaths in women worldwide. Collagen in the tumor microenvironment plays a crucial role in regulating tumor progression. We have shown that type III collagen (Col3), a component of tumor stroma, regulates myofibroblast differentiation and scar formation after cutaneous injury. During the course of these wound-healing studies, we noted that tumors developed at a higher frequency in Col3(+/-) mice compared to wild-type littermate controls. We, therefore, examined the effect of Col3 deficiency on tumor behavior, using the murine mammary carcinoma cell line 4T1. Notably, tumor volume and pulmonary metastatic burden after orthotopic injection of 4T1 cells were increased in Col3(+/-) mice compared to Col3(+/+) littermates. By using murine (4T1) and human (MDA-MB-231) breast cancer cells grown in Col3-poor and Col3-enriched microenvironments in vitro, we found that several major events of the metastatic process were suppressed by Col3, including adhesion, invasion, and migration. In addition, Col3 deficiency increased proliferation and decreased apoptosis of 4T1 cells both in vitro and in primary tumors in vivo. Mechanistically, Col3 suppresses the procarcinogenic microenvironment by regulating stromal organization, including density and alignment of fibrillar collagen and myofibroblasts. We propose that Col3 plays an important role in the tumor microenvironment by suppressing metastasis-promoting characteristics of the tumor-associated stroma.

Notch signaling in mesenchymal stem cells harvested from geriatric mice.

OBJECTIVES: Morbidity associated with geriatric fractures may be attributed, in part, to compromised mesenchymal stem cell (MSC) function within the fracture callus. The Notch signaling pathway is important for the healing of nonskeletal tissues in an age-dependent manner, but the effect of Notch on age-dependent fracture healing and MSC dysfunction has not been substantiated. The objective of this study was to examine Notch signaling in MSCs obtained from young and geriatric mice. METHODS: Marrow-derived MSCs were harvested from the femora of 5- and 25-month-old C57BL/6 mice. We assessed in vivo MSC number using CFU-F, proliferation using an Alamar Blue assay, osteoblast differentiation by Alizarin Red S staining, and adipogenic differentiation using Oil Red O staining. Notch receptor and ligand expression was assessed using quantitative PCR, and Notch signaling was assessed by evaluating Notch target gene expression (Hey and HES) under basal conditions and when cells were plated to Jagged-1 ligand. RESULTS: MSC from geriatric mice exhibit reduced MSC number (CFU-F), proliferation, adipogenesis, and inconsistent osteogenesis. The highest expressed Notch receptor is Notch 2, and the highest expressed ligand is Jagged-1, but there were no differences in ligand and receptor gene expression between young and old MSCs. Interestingly, geriatric MSCs show decreased basal Notch signaling activity but are fully responsive to Jagged-1 stimulation. CONCLUSIONS: These data suggest that therapeutic targeting of Notch signaling should be explored in clinical therapies to improve geriatric fracture healing.