Cabozantinib sensitizes microsatellite stable colorectal cancer to immune checkpoint blockade by immune modulation in human immune system mouse models

Immune checkpoint inhibitors have been found to be effective in metastatic MSI-high colorectal cancers (CRC), however, have no efficacy in microsatellite stable (MSS) cancers, which comprise the majority of mCRC cases. Cabozantinib is a small molecule multi-tyrosine kinase inhibitor that is FDA approved in advanced renal cell, medullary thyroid, and hepatocellular carcinoma. Using Human Immune System (HIS) mice, we tested the ability of cabozantinib to prime MSS-CRC tumors to enhance the potency of immune checkpoint inhibitor nivolumab. In four independent experiments, we implanted distinct MSS-CRC patient-derived xenografts (PDXs) into the flanks of humanized BALB/c-Rag2nullIl2rγnullSirpαNOD (BRGS) mice that had been engrafted with human hematopoietic stem cells at birth. For each PDX, HIS-mice cohorts were treated with vehicle, nivolumab, cabozantinib, or the combination. In three out of the four models, the combination had a lower tumor growth rate compared to vehicle or nivolumab-treated groups. Furthermore, interrogation of the HIS in immune organs and tumors by flow cytometry revealed increased Granzyme B+, TNFα+ and IFNγ+ CD4+ T cells among the human tumor infiltrating leukocytes (TIL) that correlated with reduced tumor growth in the combination-treated HIS-mice. Notably, slower growth correlated with increased expression of the CD4+ T cell ligand, HLA-DR, on the tumor cells themselves. Finally, the cabozantinib/nivolumab combination was tested in comparison to cobimetinib/atezolizumab. Although both combinations showed tumor growth inhibition, cabozantinib/nivolumab had enhanced cytotoxic IFNγ and TNFα+ T cells. This pre-clinical in vivo data warrants testing the combination in clinical trials for patients with MSS-CRC.

Central human B cell tolerance manifests with a distinctive cell phenotype and is enforced via CXCR4 signaling in hu-mice

Central B cell tolerance, the process responsible for mitigating the development of autoreactive B cells, has been extensively studied in mice, while little is known of how human B cells are tolerized in the bone marrow due to the inability to phenotypically distinguish autoreactive and non-autoreactive immature B cells and the difficulty in accessing fresh human bone marrow biopsies. Using a human immune system mouse model where all human Igk+ B cells are autoreactive and therefore tolerized in the bone marrow, we show that human autoreactive immature B cells are phenotypically different from non-autoreactive due to the differential expression of CD69, CD81, CXCR4 and other surface glycoproteins, while also exhibiting lower activation of ERK. Upon treatment of human immune system mice and autoreactive mice with a CXCR4 antagonist we show that signaling through this receptor is necessary to prevent both human and mouse autoreactive B cell clones to egress the bone marrow, indicating that CXCR4 functionally contributes to central B cell tolerance.

Testing Cancer Immunotherapy in a Human Immune System Mouse Model: Correlating Treatment Responses to Human Chimerism, Therapeutic Variables and Immune Cell Phenotypes

Over the past decade, immunotherapies have revolutionized the treatment of cancer. Although the success of immunotherapy is remarkable, it is still limited to a subset of patients. More than 1500 clinical trials are currently ongoing with a goal of improving the efficacy of immunotherapy through co-administration of other agents. Preclinical, small-animal models are strongly desired to increase the pace of scientific discovery, while reducing the cost of combination drug testing in humans. Human immune system (HIS) mice are highly immune-deficient mouse recipients rtpeconstituted with human hematopoietic stem cells. These HIS-mice are capable of growing human tumor cell lines and patient-derived tumor xenografts. This model allows rapid testing of multiple, immune-related therapeutics for tumors originating from unique clinical samples. Using a cord blood-derived HIS-BALB/c-Rag2nullIl2rγnullSIRPαNOD (BRGS) mouse model, we summarize our experiments testing immune checkpoint blockade combinations in these mice bearing a variety of human tumors, including breast, colorectal, pancreatic, lung, adrenocortical, melanoma and hematological malignancies. We present in-depth characterization of the kinetics and subsets of the HIS in lymph and non-lymph organs and relate these to protocol development and immune-related treatment responses. Furthermore, we compare the phenotype of the HIS in lymph tissues and tumors. We show that the immunotype and amount of tumor infiltrating leukocytes are widely-variable and that this phenotype is tumor-dependent in the HIS-BRGS model. We further present flow cytometric analyses of immune cell subsets, activation state, cytokine production and inhibitory receptor expression in peripheral lymph organs and tumors. We show that responding tumors bear human infiltrating T cells with a more inflammatory signature compared to non-responding tumors, similar to reports of "responding" patients in human immunotherapy clinical trials. Collectively these data support the use of HIS mice as a preclinical model to test combination immunotherapies for human cancers, if careful attention is taken to both protocol details and data analysis.

Abstract 6647: Sensitizing microsatellite stable colorectal cancer to immune checkpoint therapy utilizing Wnt pathway inhibition

Immunotherapies that target immune regulatory checkpoints such as CTLA-4 and PD-1 are widely used among many cancer types and have shown positive results in CRC with high microsatellite instability. However, in microsatellite stable (MSS) CRC there is a dismal response rate of 0%. The limited efficacy has shown to be partially due to the lack of T-cells in the tumor microenvironment and/or no activation/regulation of paramount cells in the immune system. The Wnt pathway is the most commonly altered pathway in CRC and is highly involved in driving tumor initiation and progression. Recent evidence also demonstrates the Wnt pathway is involved in T-lymphocyte development, maturation/activation of CD8+ effector T cells and recruitment of dendritic cells. Therefore, targeting the Wnt pathway utilizing a Porcupine (PORCN) inhibitor (ETC-159) in MSS CRC may be a promising strategy to sensitize tumors to immune checkpoint inhibition.

Human Immune System BRGS (BALB/c, Rag2−/−, IL2RγC−/−, NODSIRPα) mice were engrafted with MSS CRC PDX (hPDX). The hPDX were randomized according to human chimerism into the following drug treatments groups: Vehicle, ETC-159, nivolumab, and the combination. Treatments began when tumors reached 100-300mm3 and tumors were measured twice weekly. At the end of study, sera, lymph nodes, spleen, and tumor tissue were collected for immunohistochemistry, single cell suspensions, and flow cytometry analysis.

Combination therapy resulted in a significant decrease in tumor volume compared to both single agents and vehicle. Flow cytometric analysis demonstrated an increase in human immune cells, in particular human CD4 and CD8 cells in the combination compared to the vehicle and nivolumab treated groups. Additionally, these T-cells showed increased signs of activation and effector function, as indicated by increased CD69+ expression, effector memory subsets, and granzyme B+ cells in the TILs, with a further reduction in Treg populations, suggesting an overall increase in inflammation. An increase in MHC II expression on tumor cells was observed in the ETC-159 single agent with a statistically significant increase in the combination treated tumors demonstrating enhanced antigen presentation. Furthermore, PD-1 expression was upregulated on CD4+ T-cells in the ETC-159 single agent. Lastly, VECTRA analysis corroborates the flow cytometry data showing a changing tumor immune landscape through an increase in CD4+ and CD8+ T cells in the tumor and surrounding stroma.

Our data demonstrates the combination treatment of ETC-159 + nivolumab in MSS CRC hPDX show increased tumor infiltration of human immune cells. Further preclinical data is compulsory but these results support further development of this combination in clinical trials.

Citation Format: Stacey M. Bagby, Sarah J. Hartman, Natalie M. Navarro, Betelehem W. Yacob, Jeremy Shulman, Jessica Barkow, Christopher H. Lieu, S. Lindsey Davis, Alexis D. Leal, Wells A. Messersmith, Angela Minic, Kimberly R. Jordan, Julie Lang, Todd M. Pitts. Sensitizing microsatellite stable colorectal cancer to immune checkpoint therapy utilizing Wnt pathway inhibition [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 6647.

The shc adaptor protein forms interdependent phosphotyrosine-mediated protein complexes in mast cells stimulated with interleukin 3

The Shc adaptor protein possesses 2 distinct phosphotyrosine (pTyr) recognition modules-the pTyr binding (PTB) domain and the Src homology 2 (SH2) domain-and multiple potential sites for tyrosine (Tyr) phosphorylation (Tyr residues 239, 240, and 317). On stimulation of hematopoietic cells with interleukin 3 (IL-3), Shc becomes phosphorylated and may therefore contribute to IL-3 signaling. We investigated the interactions mediated by the Shc modular domains and pTyr sites in IL-3-dependent IC2 premast cells. The Shc PTB domain, rather than the SH2 domain, associated both in vitro and in vivo with the Tyr-phosphorylated beta subunit of the IL-3 receptor and with the SH2-containing 5' inositol phosphatase (SHIP), and it recognized specific NXXpY phosphopeptides from these binding partners. In IL-3-stimulated mast cells, Shc phosphorylation occurred primarily on Tyr239 and 317 and was dependent on a functional PTB domain. Phosphorylated Tyr317, and to a lesser extent, Tyr239, bound the Grb2 adaptor and SHIP. Furthermore, a pTyr317 Shc phosphopeptide selectively recognized Grb2, Sos1, SHIP, and the p85 subunit of phosphatidylinositol 3' kinase from mast cells, as characterized by mass spectrometry. These results indicate that Shc undergoes an interdependent series of pTyr-mediated interactions in IL-3-stimulated mast cells, resulting in the recruitment of proteins that regulate the Ras pathway and phospholipid metabolism.

A previously unreported surgical technique utilizing five different grafting materials to successfully achieve simultaneous alveolar regeneration and closure of a large oronasal defect

This case report describes the successful surgical and restorative management of an unusual cyst-granuloma combination that had expanded to perforate the labial and nasal parts of the maxillary bone. Enucleation and curettage of the lesions resulted in a large oronasal communication that presented a reconstructive challenge. Five different graft and/or barrier materials were used to close the oral and nasal openings and to regenerate the alveolus for implant placement and for aesthetic prosthetic restoration.

Motivation for rhinoplasty: changes in 5970 cases, in three groups, 1964 to 1997

The motivational factors were divided into three categories: (1) independent decision, (2) observation of previous patients, and (3) external influences. The results of the percentage breakdown of the patients in our present study are compared with previous results are presented in 1983 in this journal. Once again, the independent decision of the patient was the most important factor in deciding to have cosmetic rhinoplasty, followed by their observation of results in other patients. These two factors have been the motivation in approximately 80% of all the patients in all three studies. The age breakdown of cosmetic rhinoplasty patients shows that after the age of 21, as patients get older, a smaller and smaller percentage of patients was motivated for surgery by independent decision alone. These older patients need external influences to motivate them to have surgery. In most cases, the desire for surgery had smoldered in them since adolescence, and they needed an external "OK" to have it done.

Clinical evaluation of an acellular dermal allograft for increasing the zone of attached gingiva

Grafting with autogenous tissue or freeze-dried skin is the generally accepted method for increasing and/or restoring the width of attached gingiva. This article describes the periodontal use of an acellular dermal allograft previously available for treating burn patients. When used as a gingival graft, this new dermal allograft has major potential advantages over the previously available periodontal graft materials, including improved color and contour match, elimination of multiple surgeries, and unlimited availability. The technique and results of acellular dermal grafting are presented and discussed. The learning objective of this article is to describe the principles and the clinical procedure of this technique. Several cases are used to illustrate this technique.

A new technique for making occlusal devices

This procedure has an application to all types of occlusal devices. It is a novel combination of hard and soft acrylic resin. The outer shell of hard resin takes the abuse of the opposing occlusion. The thin well-controlled lining of soft resin makes it easier to seat and more comfortable to wear yet is thin enough that the entire device serves as if it were made entirely of hard acrylic resin. The detailed directions for the entire procedure make it possible to fabricate these novel devices without error.