Expression of NrasQ61R and MYC transgene in germinal center B cells induces a highly malignant multiple myeloma in mice.

NRAS Q61 mutations are prevalent in advanced/relapsed multiple myeloma (MM) and correlate with poor patient outcomes. Thus, we generated a novel MM model by conditionally activating expression of endogenous NrasQ61R and an MYC transgene in germinal center (GC) B cells (VQ mice). VQ mice developed a highly malignant MM characterized by a high proliferation index, hyperactivation of extracellular signal-regulated kinase and AKT signaling, impaired hematopoiesis, widespread extramedullary disease, bone lesions, kidney abnormalities, preserved programmed cell death protein 1 and T-cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibition motif domain immune-checkpoint pathways, and expression of human high-risk MM gene signatures. VQ MM mice recapitulate most of the biological and clinical features of human advanced/high-risk MM. These MM phenotypes are serially transplantable in syngeneic recipients. Two MM cell lines were also derived to facilitate future genetic manipulations. Combination therapies based on MEK inhibition significantly prolonged the survival of VQ mice with advanced-stage MM. Our study provides a strong rationale to develop MEK inhibition-based therapies for treating advanced/relapsed MM.

Versican-Derived Matrikines Regulate Batf3-Dendritic Cell Differentiation and Promote T Cell Infiltration in Colorectal Cancer.

Colorectal cancer originates within immunologically complex microenvironments. To date, the benefits of immunotherapy have been modest, except in neoantigen-laden mismatch repair-deficient tumors. Approaches to enhance tumor-infiltrating lymphocytes in the tumor bed may substantially augment clinical immunotherapy responses. In this article, we report that proteolysis of the tolerogenic matrix proteoglycan versican (VCAN) strongly correlated with CD8+ T cell infiltration in colorectal cancer, regardless of mismatch repair status. Tumors displaying active VCAN proteolysis and low total VCAN were associated with robust (10-fold) CD8+ T cell infiltration. Tumor-intrinsic WNT pathway activation was associated with CD8+ T cell exclusion and VCAN accumulation. In addition to regulating VCAN levels at the tumor site, VCAN proteolysis results in the generation of bioactive fragments with novel functions (VCAN-derived matrikines). Versikine, a VCAN-derived matrikine, enhanced the generation of CD103+CD11chiMHCIIhi conventional dendritic cells (cDCs) from Flt3L-mobilized primary bone marrow-derived progenitors, suggesting that VCAN proteolysis may promote differentiation of tumor-seeding DC precursors toward IRF8- and BATF3-expressing cDCs. Intratumoral BATF3-dependent DCs are critical determinants for T cell antitumor immunity, effector T cell trafficking to the tumor site, and response to immunotherapies. Our findings provide a rationale for testing VCAN proteolysis as a predictive and/or prognostic immune biomarker and VCAN-derived matrikines as novel immunotherapy agents.

X-linked genes exhibit miR6891-5p-regulated skewing in Sjögren's syndrome.

Many autoimmune diseases exhibit a strikingly increased prevalence in females, with primary Sjögren's syndrome (pSS) being the most female-predominant example. However, the molecular basis underlying the female-bias in pSS remains elusive. To address this knowledge gap, we performed genome-wide, allele-specific profiling of minor salivary gland-derived mesenchymal stromal cells (MSCs) from pSS patients and control subjects, and detected major differences in the regulation of X-linked genes. In control female MSCs, X-linked genes were expressed from both paternal and maternal X chromosomes with a median paternal ratio of ~ 0.5. However, in pSS female MSCs, X-linked genes exhibited preferential expression from one of the two X chromosomes. Concomitantly, pSS MSCs showed decrease in XIST levels and reorganization of H3K27me3+ foci in the nucleus. Moreover, the HLA-locus-expressed miRNA miR6891-5p was decreased in pSS MSCs. miR6891-5p inhibition in control MSCs caused XIST dysregulation, ectopic silencing, and allelic skewing. Allelic skewing was accompanied by the mislocation of protein products encoded by the skewed genes, which was recapitulated by XIST and miR6891-5p disruption in control MSCs. Our data reveal X skewing as a molecular hallmark of pSS and highlight the importance of restoring X-chromosomal allelic balance for pSS treatment. KEY MESSAGES: X-linked genes exhibit skewing in primary Sjögren's syndrome (pSS). X skewing in pSS associates with alterations in H3K27me3 deposition. pSS MSCs show decreased levels of miR6891-5p, a HLA-expressed miRNA. miR6891-5p inhibition causes H3K27me3 dysregulation and allelic skewing.

Stromal remodeling regulates dendritic cell abundance and activity in the tumor microenvironment.

Stimulatory type 1 conventional dendritic cells (cDC1s) engage in productive interactions with CD8+ effectors along tumor-stroma boundaries. The paradoxical accumulation of "poised" cDC1s within stromal sheets is unlikely to simply reflect passive exclusion from tumor cores. Drawing parallels with embryonic morphogenesis, we hypothesized that invasive margin stromal remodeling generates developmentally conserved cell fate cues that regulate cDC1 behavior. We find that, in human T cell-inflamed tumors, CD8+ T cells penetrate tumor nests, whereas cDC1s are confined within adjacent stroma that recurrently displays site-specific proteolysis of the matrix proteoglycan versican (VCAN), an essential organ-sculpting modification in development. VCAN is necessary, and its proteolytic fragment (matrikine) versikine is sufficient for cDC1 accumulation. Versikine does not influence tumor-seeding pre-DC differentiation; rather, it orchestrates a distinctive cDC1 activation program conferring exquisite sensitivity to DNA sensing, supported by atypical innate lymphoid cells. Thus, peritumoral stroma mimicking embryonic provisional matrix remodeling regulates cDC1 abundance and activity to elicit T cell-inflamed tumor microenvironments.

Immunometabolic function of the transcription cofactor VGLL3 provides an evolutionary rationale for sexual dimorphism in autoimmunity.

Sexual dimorphism is exhibited remarkably in the female predominance of autoimmune diseases (e.g. systemic lupus erythematosus, female-to-male ratio 9 : 1). To understand the female bias in autoimmunity, we focused on vestigial-like family member 3 (VGLL3), a molecule with increased expression in females and known to promote autoimmunity. We report that VGLL3 mediates the cellular stress response by upregulating p53 and IL-17C. Energy stress allows VGLL3 to be induced by IFNα, which ultimately leads to p53-dependent, lupus-associated, inflammatory cell death. Our results suggest that female-biased expression of VGLL3 helps cells adapt to metabolic stress, which, intriguingly, is known as a significant challenge during the evolution of placental mammals due to the need to feed a developing embryo. The findings also uncover the importance of maintaining metabolic homeostasis in the prevention of autoimmunity.

Tumor matrix remodeling and novel immunotherapies: the promise of matrix-derived immune biomarkers.

Recent advances in our understanding of the dynamics of cellular cross-talk have highlighted the significance of host-versus-tumor effect that can be harnessed with immune therapies. Tumors exploit immune checkpoints to evade adaptive immune responses. Cancer immunotherapy has witnessed a revolution in the past decade with the development of immune checkpoint inhibitors (ICIs), monoclonal antibodies against cytotoxic T lymphocyte antigen 4 (CTLA-4) and programmed cell death protein 1 (PD-1) or their ligands, such as PD1 ligand 1 (PD-L1). ICIs have been reported to have activity against a broad range of tumor types, in both solid organ and hematologic malignancy contexts. However, less than one-third of the patients achieve a durable and meaningful treatment response. Expression of immune checkpoint ligands (e.g., PD-L1), mutational burden and tumor-infiltrating lymphocytes are currently used as biomarkers for predicting response to ICIs. However, they do not reliably predict which patients will benefit from these therapies. There is dire need to discover novel biomarkers to predict treatment efficacy and to identify areas for development of combination strategies to improve response rates. Emerging evidence suggests key roles of tumor extracellular matrix (ECM) components and their proteolytic remodeling products in regulating each step of the cancer-immunity cycle. Here we review tumor matrix dynamics and matrix remodeling in context of anti-tumor immune responses and immunotherapy and propose the exploration of matrix-based biomarkers to identify candidates for immune therapy.

Extracellular matrix and the myeloid-in-myeloma compartment: balancing tolerogenic and immunogenic inflammation in the myeloma niche.

The last 10-15 years have witnessed a revolution in treating multiple myeloma, an incurable cancer of Ab-producing plasma cells. Advances in myeloma therapy were ushered in by novel agents that remodel the myeloma immune microenvironment. The first generation of novel agents included immunomodulatory drugs (thalidomide analogs) and proteasome inhibitors that target crucial pathways that regulate immunity and inflammation, such as NF-κB. This paradigm continued with the recent regulatory approval of mAbs (elotuzumab, daratumumab) that impact both tumor cells and associated immune cells. Moreover, recent clinical data support checkpoint inhibition immunotherapy in myeloma. With the success of these agents has come the growing realization that the myeloid infiltrate in myeloma lesions-what we collectively call the myeloid-in-myeloma compartment-variably sustains or deters tumor cells by shaping the inflammatory milieu of the myeloma niche and by promoting or antagonizing immune-modulating therapies. The myeloid-in-myeloma compartment includes myeloma-associated macrophages and granulocytes, dendritic cells, and myeloid-derived-suppressor cells. These cell types reflect variable states of differentiation and activation of tumor-infiltrating cells derived from resident myeloid progenitors in the bone marrow-the canonical myeloma niche-or myeloid cells that seed both canonical and extramedullary, noncanonical niches. Myeloma-infiltrating myeloid cells engage in crosstalk with extracellular matrix components, stromal cells, and tumor cells. This complex regulation determines the composition, activation state, and maturation of the myeloid-in-myeloma compartment as well as the balance between immunogenic and tolerogenic inflammation in the niche. Redressing this balance may be a crucial determinant for the success of antimyeloma immunotherapies.