Loss of secreted gelsolin enhances response to anticancer therapies.

Type 1 conventional dendritic cells (cDC1) play a critical role in priming anticancer cytotoxic CD8+ T cells. DNGR-1 (a.k.a. CLEC9A) is a cDC1 receptor that binds to F-actin exposed on necrotic cancer and normal cells. DNGR-1 signaling enhances cross-presentation of dead-cell associated antigens, including tumor antigens. We have recently shown that secreted gelsolin (sGSN), a plasma protein, competes with DNGR-1 for binding to dead cell-exposed F-actin and dampens anticancer immunity. Here, we investigated the effects of loss of sGSN on various anticancer therapies that are thought to induce cell death and provoke an immune response to cancer. We compared WT (wildtype) with Rag1-/- , Batf3-/- , Clec9agfp/gfp , sGsn-/- or sGsn-/- Clec9agfp/gfp mice implanted with transplantable tumor cell lines, including MCA-205 fibrosarcoma, 5555 BrafV600E melanoma and B16-F10 LifeAct (LA)-ovalbumin (OVA)-mCherry melanoma. Tumor-bearing mice were treated with (1) doxorubicin (intratumoral) chemotherapy for MCA-205, (2) BRAF-inhibitor PLX4720 (oral gavage) targeted therapy for 5555 BrafV600E, and (3) X-ray radiotherapy for B16 LA-OVA-mCherry. We confirmed that efficient tumor control following each therapy requires an immunocompetent host as efficacy was markedly reduced in Rag1-/- compared with WT mice. Notably, across all the therapeutic modalities, loss of sGSN significantly enhanced tumor control compared with treated WT controls. This was an on-target effect as mice deficient in both sGSN and DNGR-1 behaved no differently from WT mice following therapy. In sum, we find that mice deficient in sGsn display enhanced DNGR-1-dependent responsiveness to chemotherapy, targeted therapy and radiotherapy. Our findings are consistent with the notion some cancer therapies induce immunogenic cell death (ICD), which mobilizes anticancer T cells. Our results point to cDC1 and DNGR-1 as decoders of ICD and to sGSN as a negative regulator of such decoding, highlighting sGSN as a possible target in cancer treatment. Further prospective studies are warranted to identify patients who may benefit most from inhibition of sGSN function

DNGR-1 regulates proliferation and migration of bone marrow dendritic cell progenitors.

Conventional dendritic cells (cDCs) are sentinel cells that play a crucial role in both innate and adaptive immune responses. cDCs originate from a progenitor (pre-cDC) in the bone marrow (BM) that travels via the blood to seed peripheral tissues before locally differentiating into functional cDC1 and cDC2 cells, as part of a process known as cDCpoiesis. How cDCpoiesis is regulated and whether this affects the output of cDCs is poorly understood. In this study, we show that DNGR-1, an innate immune receptor expressed by cDC progenitors and type 1 cDCs, can regulate cDCpoiesis in mice. In a competitive chimera setting, cDC progenitors lacking DNGR-1 exhibit increased proliferation and tissue migratory potential. Compared with their WT counterparts, DNGR-1-deficient cDC progenitor cells display superior colonization of peripheral tissues but an altered distribution. These findings suggest that cDCpoiesis can be regulated in part by precursor cell-intrinsic processes driven by signals from innate immune receptors such as DNGR-1 that may respond to alterations in the BM milieu

Secreted gelsolin inhibits DNGR-1-dependent cross-presentation and cancer immunity

Cross-presentation of antigens from dead tumor cells by type 1 conventional dendritic cells (cDC1s) is thought to underlie priming of anti-cancer CD8+ T cells. cDC1 express high levels of DNGR-1 (a.k.a. CLEC9A), a receptor that binds to F-actin exposed by dead cell debris and promotes cross-presentation of associated antigens. Here, we show that secreted gelsolin (sGSN), an extracellular protein, decreases DNGR-1 binding to F-actin and cross-presentation of dead cell-associated antigens by cDC1s. Mice deficient in sGsn display increased DNGR-1-dependent resistance to transplantable tumors, especially ones expressing neoantigens associated with the actin cytoskeleton, and exhibit greater responsiveness to cancer immunotherapy. In human cancers, lower levels of intratumoral sGSN transcripts, as well as presence of mutations in proteins associated with the actin cytoskeleton, are associated with signatures of anti-cancer immunity and increased patient survival. Our results reveal a natural barrier to cross-presentation of cancer antigens that dampens anti-tumor CD8+ T cell responses

Supplementary Table S3 from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

PDXs and WES list.</p

Supplementary Methods from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

Supplementary Methods</p

Supplementary Table S5 from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

CDXs list.</p

Supplementary Table S2 from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

10 gene Miseq primers.</p

Supplementary Figure S1 - S3 from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

Supplementary Figure S1. IGV visualization for whole exome sequencing of codon Q61 of NRAS in the pre-treatment tumor vs. the relapsed tumor in patient 1. The red color indicates the A>G for the p.Q61R mutation in the tumor. Supplementary Figure S2. A. IGV visualization for the targeted sequencing of BRAF and PI3KCA in patient 6. B. IGV visualization for the targeted sequencing of BRAF and NRAS in patient 7. Supplementary Figure S3. Response of patient 5 PDX to PLX4720.</p

Supplementary Table S4 from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

40 Gene Miseq primers.</p

Supplementary Table S1 from Application of Sequencing, Liquid Biopsies, and Patient-Derived Xenografts for Personalized Medicine in Melanoma

ctDNA patient list.</p