Comparative Genomics Reveals Shared Mutational Landscape in Canine Hemangiosarcoma and Human Angiosarcoma.

Angiosarcoma is a highly aggressive cancer of blood vessel-forming cells with few effective treatment options and high patient mortality. It is both rare and heterogenous, making large, well-powered genomic studies nearly impossible. Dogs commonly suffer from a similar cancer, called hemangiosarcoma, with breeds like the golden retriever carrying heritable genetic factors that put them at high risk. If the clinical similarity of canine hemangiosarcoma and human angiosarcoma reflects shared genomic etiology, dogs could be a critically needed model for advancing angiosarcoma research. We assessed the genomic landscape of canine hemangiosarcoma via whole-exome sequencing (47 golden retriever hemangiosarcomas) and RNA sequencing (74 hemangiosarcomas from multiple breeds). Somatic coding mutations occurred most frequently in the tumor suppressor TP53 (59.6% of cases) as well as two genes in the PI3K pathway: the oncogene PIK3CA (29.8%) and its regulatory subunit PIK3R1 (8.5%). The predominant mutational signature was the age-associated deamination of cytosine to thymine. As reported in human angiosarcoma, CDKN2A/B was recurrently deleted and VEGFA, KDR, and KIT recurrently gained. We compared the canine data to human data recently released by The Angiosarcoma Project, and found many of the same genes and pathways significantly enriched for somatic mutations, particularly in breast and visceral angiosarcomas. Canine hemangiosarcoma closely models the genomic landscape of human angiosarcoma of the breast and viscera, and is a powerful tool for investigating the pathogenesis of this devastating disease. IMPLICATIONS: We characterize the genomic landscape of canine hemangiosarcoma and demonstrate its similarity to human angiosarcoma.

Mesenchymal stromal cells inhibit murine syngeneic anti-tumor immune responses by attenuating inflammation and reorganizing the tumor microenvironment.

The potential of mesenchymal stromal cells (MSCs) to inhibit anti-tumor immunity is becoming increasingly well recognized, but the precise steps affected by these cells during the development of an anti-tumor immune response remain incompletely understood. Here, we examined how MSCs affect the steps required to mount an effective anti-tumor immune response following administration of adenovirus Fas ligand (Ad-FasL) in the Lewis lung carcinoma (LL3) model. Administration of bone marrow-derived MSCs with LL3 cells accelerated tumor growth significantly. MSCs inhibited the inflammation induced by Ad-FasL in the primary tumors, precluding their rejection; MSCs also reduced the consequent expansion of tumor-specific T cells in the treated hosts. When immune T cells were transferred to adoptive recipients, MSCs impaired, but did not completely abrogate the ability of these T cells to promote elimination of secondary tumors. This impairment was associated with a modest reduction in tumor-infiltrating T cells, with a significant reduction in tumor-infiltrating macrophages, and with a reorganization of the stromal environment. Our data indicate that MSCs in the tumor environment reduce the efficacy of immunotherapy by creating a functional and anatomic barrier that impairs inflammation, T cell priming and expansion, and T cell function-including recruitment of effector cells.

A double blinded, placebo-controlled pilot study to examine reduction of CD34 +/CD117 +/CD133 + lymphoma progenitor cells and duration of remission induced by neoadjuvant valspodar in dogs with large B-cell lymphoma.

We previously described a population of lymphoid progenitor cells (LPCs) in canine B-cell lymphoma defined by retention of the early progenitor markers CD34 and CD117 and "slow proliferation" molecular signatures that persist in the xenotransplantation setting. We examined whether valspodar, a selective inhibitor of the ATP binding cassette B1 transporter (ABCB1, a.k.a., p-glycoprotein/multidrug resistance protein-1) used in the neoadjuvant setting would sensitize LPCs to doxorubicin and extend the length of remission in dogs with therapy naïve large B-cell lymphoma. Twenty dogs were enrolled into a double-blinded, placebo controlled study where experimental and control groups received oral valspodar (7.5 mg/kg) or placebo, respectively, twice daily for five days followed by five treatments with doxorubicin 21 days apart with a reduction in the first dose to mitigate the potential side effects of ABCB1 inhibition. Lymph node and blood LPCs were quantified at diagnosis, on the fourth day of neoadjuvant period, and 1-week after the first chemotherapy dose. Valspodar therapy was well tolerated. There were no differences between groups in total LPCs in lymph nodes or peripheral blood, nor in event-free survival or overall survival. Overall, we conclude that valspodar can be administered safely in the neoadjuvant setting for canine B-cell lymphoma; however, its use to attenuate ABCB1 + cells does not alter the composition of lymph node or blood LPCs, and it does not appear to be sufficient to prolong doxorubicin-dependent remissions in this setting.

Nfatc2 and Tob1 have non-overlapping function in T cell negative regulation and tumorigenesis.

Nfatc2 and Tob1 are intrinsic negative regulators of T cell activation. Nfatc2-deficient and Tob1-deficient T cells show reduced thresholds of activation; however, whether these factors have independent or overlapping roles in negative regulation of T cell responses has not been previously examined. Here, we show that Nfatc2 knockout (KO) but not Tob1 KO mice have age-associated accumulation of persistently activated T cells in vivo and expansion of the CD44+ memory cell compartment and age-associated lymphocytic infiltrates in visceral organs, without significant changes in numbers of CD4+CD25+Foxp3+ regulatory T cells (Treg). In vitro, CD4+CD25- "conventional" T cells (Tconvs) from both KO strains showed greater proliferation than wild type (WT) Tconvs. However, while Tregs from Nfatc2 KO mice retained normal suppressive function, Tregs from Tob1 KOs had enhanced suppressive activity. Nfatc2 KO Tconvs expanded somewhat more rapidly than WT Tconvs under conditions of homeostatic proliferation, but their accelerated growth capacity was negated, at least acutely, in a lymphoreplete environment. Finally, Nfatc2 KO mice developed a previously uncharacterized increase in B-cell malignancies, which was not accelerated by the absence of Tob1. The data thus support the prevailing hypothesis that Nfatc2 and Tob1 are non-redundant regulators of lymphocyte homeostasis.