Versican secreted by the ovary links ovulation and migration in fallopian tube derived serous cancer

High grade serous ovarian cancers (HGSOC) predominantly arise in the fallopian tube epithelium (FTE) and colonize the ovary first, before further metastasis to the peritoneum. Ovarian cancer risk is directly related to the number of ovulations, suggesting that the ovary may secrete specific factors that act as chemoattractants for fallopian tube derived tumor cells during ovulation. We found that 3D ovarian organ culture produced a secreted factor that enhanced the migration of FTE non-tumorigenic cells as well as cells harboring specific pathway modifications commonly found in high grade serous cancers. Through size fractionation and a small molecule inhibitors screen, the secreted protein was determined to be 50-100kDa in size and acted through the Epidermal Growth Factor Receptor (EGFR). To correlate the candidates with ovulation, the PREDICT organ-on-chip system was optimized to support ovulation in a perfused microfluidic platform. Versican was found in the correct molecular weight range, contained EGF-like domains, and correlated with ovulation in the PREDICT system. Exogenous versican increased migration, invasion, and enhanced adhesion of both murine and human FTE cells to the ovary in an EGFR-dependent manner. The identification of a protein secreted during ovulation that impacts the ability of FTE cells to colonize the ovary provides new insights into the development of strategies for limiting primary ovarian metastasis.

Abstract 4211: Minocycline-based metronomic therapy as a novel approach to enhance anti-tumor immune responses and reduce tumor burden in mouse models of colorectal cancer

Despite the availability of numerous new therapies including immune checkpoint inhibitors, patients with colon cancer are faced with limited treatment options. We recently demonstrated that low metronomic dose of PARP inhibitor synergizes with anti-PD-1 immunotherapy, in part, by modulating the suppressive function of MDSCs via a reduction in Arg1 and iNOS but independently of DNA damage and STING (PMC7839867). The non-antibiotic properties of minocycline (Mc) include its ability to moderately inhibit PARP. We took advantage of Mc as a weak PARP inhibitor to explore its potential on tumorigenesis and immune suppression in colon cancer models. In this study, we show that Mc significantly reduced Arg1 and iNOS in bone marrow (BM)-derived MDSCs both at the mRNA and protein levels. Paradoxically, such strong effect did not culminate in a substantial modulation of MDSCs suppressive function as assessed by co-cultured anti-CD3/CD28-stimulated CFSE-labeled T cells proliferation. However and similarly to PARP inhibitors, Mc increased PD-L1 expression in several cell types. We thus speculated that the antibiotic might enhance anti-cancer immunotherapy and explored such potential in a MC-38 and CT-26 cell-based mouse models of colon cancer representing the MSI and MSS traits of the disease. Treatment of tumor-bearing mice with low metronomic doses of Mc (0.5 or 5mkg) promoted a substantial reduction in tumor size in the MC-38 cell-based model (MSI) without an apparent superiority of any of the two doses. Surprisingly, neither dose of Mc exerted appreciable effects on tumor size in the CT-26 cell-based model (MSS). The anti-tumor effect of Mc in the MSI model was associated with a significant reduction in intratumoral monocytic-MDSC population. While MDSCs harvested from tumors of control mice re-infiltrated ex vivo generated MC-38 cell-based organoids, MDSCs harvested from tumors of Mc-treated mice failed to re-infiltrate the organoids. This suggests that Mc may interfere with MDSCs intratumorally infiltration. The Mc concentrations used in this study exerted little to no effect on bacterial growth suggesting that the observed effects were independent of the antibiotic properties of the drug. Unlike the effects observed in vitro, Mc treatment reduced intratumoral PD-L1 while increasing IFNγ. The discrepancy may be associated with intratumoral stress condition as assessed by Chop protein levels and reproduced in vitro by serum starvation. Although the metronomic Mc dose and anti-PD1 administration caused a significant reduction in tumor size individually, the combination therapy promoted a 66.7% curing of the tumors. Our results propose repurposing Mc at metronomic doses as a new approach to enhance efficacy of immunotherapy for patients with MSI colon cancer.

Citation Format: Salome V. Ibba, Hanh H. Luu, Mohamed Ghonim, Cecilia Vittori, Matthew J. Dean, Giulia Monticone, Francesca Peruzzi, Augusto Ochoa, Lucio Miele, Hamid A. Boulares. Minocycline-based metronomic therapy as a novel approach to enhance anti-tumor immune responses and reduce tumor burden in mouse models of colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4211.

Abstract 2081: Poly ADP-ribose polymerase inhibition enhances T cell cytotoxicity and anti-tumor function by altering NAD+ levels

Poly ADP-ribose polymerase (PARP) is an NAD-dependent DNA repair enzyme. Inhibition of PARP in BRCA-mutant cancers has been a clinically approved therapy for several years. While the PARP inhibitor, olaparib, has been approved for the treatment of BRCA-mutant breast and ovarian cancers, it has not been used in other cancers because its mechanism of action relies on synthetic lethality. We have found that olaparib may also have use in other cancers due to its ability to modulate the immune system directly. Specifically, we have found that olaparib is able to increase the proliferation, activation, and cytotoxicity of T cells in vitro and reduce tumor growth in vivo at low doses. Recent papers have proposed that olaparib is able to enhance T cell function through the stimulator of interferon genes (STING) pathway by enhancing antigen presenting cell activity and resulting in more granzyme B expression and enhanced tumor killing. Using purified T cells from both wild type and STING knockout mice, we have shown that olaparib can also cause an increase in granzyme B and perforin expression, an increase in T cell proliferation, and enhanced tumor cell killing in a STING-independent manner. Because PARP is an NAD-consuming enzyme, we examined the role of NAD+ in the activation T cells and the production of granzyme B and perforin. By using an inhibitor of NAD+ recycling, FK866, we show that T cells have reduced NAD+ levels, reduced granzyme B and perforin expression, and even fail to activate in the presence of CD3 and CD28 when NAD+ is limited; however, adding olaparib to these cells rescues the effects of FK866 and allows proliferation and granzyme B production. In vivo we can see that even at olaparib doses that are significantly below those which induce synthetic lethality of tumor cells, olaparib is able to inhibit tumor growth in models of both colorectal and breast cancer. This suggests that olaparib can modulate the activity of T cells directly and has implications for enhancing the anti-tumor activity of these cells both alone and in combination with other forms of immunotherapy.

Citation Format: Matthew J. Dean, Liqin Zheng, Phaethon Philbrook, Augusto C. Ochoa, A. Hamid Boulares. Poly ADP-ribose polymerase inhibition enhances T cell cytotoxicity and anti-tumor function by altering NAD+ levels [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2081.

Severe COVID-19 Is Characterized by an Impaired Type I Interferon Response and Elevated Levels of Arginase Producing Granulocytic Myeloid Derived Suppressor Cells

COVID-19 ranges from asymptomatic in 35% of cases to severe in 20% of patients. Differences in the type and degree of inflammation appear to determine the severity of the disease. Recent reports show an increase in circulating monocytic-myeloid-derived suppressor cells (M-MDSC) in severe COVID 19 that deplete arginine but are not associated with respiratory complications. Our data shows that differences in the type, function and transcriptome of granulocytic-MDSC (G-MDSC) may in part explain the severity COVID-19, in particular the association with pulmonary complications. Large infiltrates by Arginase 1+ G-MDSC (Arg+G-MDSC), expressing NOX-1 and NOX-2 (important for production of reactive oxygen species) were found in the lungs of patients who died from COVID-19 complications. Increased circulating Arg+G-MDSC depleted arginine, which impaired T cell receptor and endothelial cell function. Transcriptomic signatures of G-MDSC from patients with different stages of COVID-19, revealed that asymptomatic patients had increased expression of pathways and genes associated with type I interferon (IFN), while patients with severe COVID-19 had increased expression of genes associated with arginase production, and granulocyte degranulation and function. These results suggest that asymptomatic patients develop a protective type I IFN response, while patients with severe COVID-19 have an increased inflammatory response that depletes arginine, impairs T cell and endothelial cell function, and causes extensive pulmonary damage. Therefore, inhibition of arginase-1 and/or replenishment of arginine may be important in preventing/treating severe COVID-19.

Silencing PTEN in the fallopian tube promotes enrichment of cancer stem cell-like function through loss of PAX2

High-grade serous ovarian cancer (HGSOC) is the most lethal gynecological malignancy that is primarily detected at the metastatic stage. Most HGSOC originates from the fallopian tube epithelium (FTE) and metastasizes to the ovary before invading the peritoneum; therefore, it is crucial to study disease initiation and progression using FTE-derived models. We previously demonstrated that loss of PTEN from the FTE leads to ovarian cancer. In the present study, loss of PTEN in FTE led to the enrichment of cancer stem cell markers such as LGR5, WNT4, ALDH1, CD44. Interestingly, loss of the transcription factor PAX2, which is a common and early alteration in HGSOC, played a pivotal role in the expression of cancer stem-like cells (CSC) markers and cell function. In addition, loss of PTEN led to the generation of two distinct subpopulations of cells with different CSC marker expression, tumorigenicity, and chemoresistance profiles. Taken together, these data suggest that loss of PTEN induces reprogramming of the FTE cells into a more stem-like phenotype due to loss of PAX2 and provides a model to study early events during the FTE-driven ovarian cancer tumor formation.

Transcriptome and Functions of Granulocytic Myeloid-Derived Suppressor Cells Determine their Association with Disease Severity of COVID-19

COVID-19 ranges from asymptomatic in 35% of cases to severe in 20% of patients. Differences in the type and degree of inflammation appear to determine the severity of the disease. Recent reports show an increase in circulating monocytic-myeloid-derived suppressor cells (M-MDSC) in severe COVID 19, that deplete arginine but are not associated with respiratory complications. Our data shows that differences in the type, function and transcriptome of Granulocytic-MDSC (G-MDSC) may in part explain the severity COVID-19, in particular the association with pulmonary complications. Large infiltrates by Arginase 1 ⁺ G-MDSC (Arg ⁺ G-MDSC), expressing NOX-1 and NOX-2 (important for production of reactive oxygen species) were found in the lungs of patients who died from COVID-19 complications. Increased circulating Arg ⁺ G-MDSC depleted arginine, which impaired T cell receptor and endothelial cell function. Transcriptomic signatures of G-MDSC from patients with different stages of COVID-19, revealed that asymptomatic patients had increased expression of pathways and genes associated with type I interferon (IFN), while patients with severe COVID-19 had increased expression of genes associated with arginase production, and granulocyte degranulation and function. These results suggest that asymptomatic patients develop a protective type I IFN response, while patients with severe COVID-19 have an increased inflammatory response that depletes arginine, impairs T cell and endothelial cell function, and causes extensive pulmonary damage. Therefore, inhibition of arginase-1 and/or replenishment of arginine may be important in preventing/treating severe COVID-19.

Presence of antibody-dependent cellular cytotoxicity (ADCC) against SARS-CoV-2 in COVID-19 plasma

Background

Neutralizing-antibody (nAb) is the major focus of most ongoing COVID-19 vaccine trials. However, nAb response against SARS-CoV-2, when present, decays rapidly. Given the myriad roles of antibodies in immune responses, it is possible that antibodies could also mediate protection against SARS-CoV-2 via effector mechanisms such as antibody-dependent cellular cytotoxicity (ADCC), which we sought to explore here.

Methods

Plasma of 3 uninfected controls and 20 subjects exposed to, or recovering from, SARS-CoV-2 infection were collected from U.S. and sub-Saharan Africa. Immunofluorescence assay was used to detect the presence of SARS-CoV-2 specific IgG antibodies in the plasma samples. SARS-CoV-2 specific neutralizing capability of these plasmas was assessed with SARS-CoV-2 spike pseudotyped virus. ADCC activity was assessed with a calcein release assay.

Results

SARS-CoV-2 specific IgG antibodies were detected in all COVID-19 subjects studied. All but three COVID-19 subjects contained nAb at high potency (>80% neutralization). Plasma from 19/20 of COVID-19 subjects also demonstrated strong ADCC activity against SARS-CoV-2 spike glycoprotein, including two individuals without nAb against SARS-CoV-2.

Conclusion

Both neutralizing and non-neutralizing COVID-19 plasmas can mediate ADCC. Our findings argue that evaluation of potential vaccines against SARS-CoV-2 should include investigation of the magnitude and durability of ADCC, in addition to nAb.

Myeloid-derived suppressor cells (MDSC): When good intentions go awry

MDSC are a heterogeneous population of immature myeloid cells that are released by biological stress such as tissue damage and inflammation. Conventionally, MDSC are known for their detrimental role in chronic inflammation and neoplastic conditions. However, their intrinsic functions in immunoregulation, wound healing, and angiogenesis are intended to protect from over-reactive immune responses, maintenance of immunotolerance, tissue repair, and homeostasis. Paradoxically, under certain conditions, MDSC can impair protective immune responses and exacerbate the disease. The transition from protective to harmful MDSC is most likely driven by environmental and epigenetic mechanisms induced by prolonged exposure to unresolved inflammatory triggers. Here, we review several examples of the dual impact of MDSC in conditions such as maternal-fetal tolerance, self-antigens immunotolerance, obesity-associated cancer, sepsis and trauma. Moreover, we also highlighted the evidence indicating that MDSC have a role in COVID-19 pathophysiology. Finally, we have summarized the evidence indicating epigenetic mechanisms associated with MDSC function.

Targeting PARP-1 with metronomic therapy modulates MDSC suppressive function and enhances anti-PD-1 immunotherapy in colon cancer

Background

Poly(ADP-ribose) polymerase (PARP) inhibitors (eg, olaparib) are effective against BRCA-mutated cancers at/near maximum tolerated doses by trapping PARP-1 on damaged chromatin, benefitting only small patient proportions. The benefits of targeting non-DNA repair aspects of PARP with metronomic doses remain unexplored.

Methods

Colon epithelial cells or mouse or human bone marrow (BM)-derived-myeloid-derived suppressor cells (MDSCs) were stimulated to assess the effect of partial PARP-1 inhibition on inflammatory gene expression or immune suppression. Mice treated with azoxymethane/four dextran-sulfate-sodium cycles or APC^Min/+ mice bred into PARP-1^+/− or treated with olaparib were used to examine the role of PARP-1 in colitis-induced or spontaneous colon cancer, respectively. Syngeneic MC-38 cell-based (microsatellite instability, MSI^high) or CT-26 cell-based (microsatellite stable, MSS) tumor models were used to assess the effects of PARP inhibition on host responses and synergy with anti-Programmed cell Death protein (PD)-1 immunotherapy.

Results

Partial PARP-1 inhibition, via gene heterozygosity or a moderate dose of olaparib, protected against colitis-mediated/APC^Min-mediated intestinal tumorigenesis and APC^Min-associated cachexia, while extensive inhibition, via gene knockout or a high dose of olaparib, was ineffective or aggravating. A sub-IC50-olaparib dose or PARP-1 heterozygosity was sufficient to block tumorigenesis in a syngeneic colon cancer model by modulating the suppressive function, but not intratumoral migration or differentiation, of MDSCs, with concomitant increases in intratumoral T cell function and cytotoxicity, as assessed by granzyme-B/interferon-γ levels. Adoptive transfer of WT-BM-MDSCs abolished the protective effects of PARP-1 heterozygosity. The mechanism of MDSC modulation involved a reduction in arginase-1/inducible nitric oxide synthase/cyclo-oxygenase-2, but independent of PARP-1 trapping on chromatin. Although a high-concentration olaparib or the high-trapping PARP inhibitor, talazoparib, activated stimulator of interferon gene (STING) in BRCA-proficient cells and induced DNA damage, sub-IC50 concentrations of either drug failed to induce activation of the dsDNA break sensor. STING expression appeared dispensable for MDSC suppressive function and was not strictly required for olaparib-mediated effects. Ironically, STING activation blocked human and mouse MDSC function with no additive effects with olaparib. A metronomic dose of olaparib was highly synergistic with anti-PD-1-based immunotherapy, leading to eradication of MSI^high or reduction of MSS tumors in mice.

Conclusions

These results support a paradigm-shifting concept that expands the utility of PARP inhibitor and encourage testing metronomic dosing of PARP inhibitor to enhance the efficacy of checkpoint inhibitor-based immunotherapies in cancer.

Abstract 6691: Delivering intra-tumoral immune modulators and targeting cancer stem cells using recombinant- AAVs

Solid tumors are composed of heterogeneous cell populations that support rapid growth of cancer cells and suppress immune cell responses. Unleashing the body's own immune response to eradicate cancer cells is one of the most promising ways to treat cancer patients. However, cancer immunotherapy is not without challenges. Some of these include:

1) Phenotypic plasticity and clonal selection in a highly dynamic, heterogeneous and mutable cell population, which leads to de novo and acquired resistance;

2) Immune editing by cancer cells;

3) Expression of immune check point ligands and receptors to suppress immune response locally within the tumor microenvironment, and systemically using exosomes as immune checkpoint carriers;

4) Cross-talk between cancer stem cells and the immune microenvironment;

5) Feasibility of developing personalized treatment strategies, such as cost vs benefit of CAR-T-cell therapy and time constraint, and humanized antibody production;

6) Systemic toxicity of current immunotherapy strategies;

To address these challenges, we propose to use a recombinant adeno-associated virus (rAAV) platform to simultaneously enhance tumor immunity and target cancer stem cells by intra-tumoral administration. We express programmed cell death ligand-1 (PD-L1), and B7-H3 (CD276), in combination with a Notch1 decoy. The latter was chosen because: 1) Notch is a crucial signaling component of cancer stem cells (CSCs) maintenance and resistance and 2) Studies have shown that within the tumor, regulatory T-cells (Treg) are activated by OX40 and Notch ligand Jagged1. Blocking Notch signaling would have dual advantages: blocking Notch signaling in CSCs, and preventing activation of immunosuppressive Tregs.

Based on current clinical trials and our experimental results, we hypothesized that intra-tumoral injection of rAAV viral particles engineered to express soluble PD-1, B7-H3 and Notch1 decoys in combination with lipopolysaccharide (LPS) is a promising strategy. To test our hypothesis, we used two mouse triple negative breast (TNBC) cancer models: C0321 in the FVB background and M-Wnt in the C57/Bl6 background; both are aggressive, highly metastatic, and similar to human TNBC. Using tumor spheroids in vitro, in the presence of soluble decoys of PD-1, B7-H3 and Notch1 synergistically induced the most effective tumor cell killing, compared to single decoy application. Importantly, intra-tumoral injection of PD-1, B7-H3 and Notch1 decoys in combination with LPS induced necrosis of tumors in vivo in our preliminary findings.

Citation Format: Deniz A. Ucar, Giulia Monticone, Fokhrul Hossain, Samarpan Majumder, Dorota Wyczechowska, Matthew J. Dean, Luis Del Valle, Jovanny Zabaleta, Yong Ran, Sudarvili Shanthalingam, Abraham Bert Chabot, Bridgette M. Collins-Burow, Matthew E. Burrow, Barbara Osborne, Todd Eliot Golde, Lucio Miele. Delivering intra-tumoral immune modulators and targeting cancer stem cells using recombinant- AAVs [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 6691.

Exogenous lipid uptake induces metabolic and functional reprogramming of tumor-associated myeloid-derived suppressor cells

Myeloid-derived suppressor cells (MDSC) promote tumor growth by blocking anti-tumor T cell responses. Recent reports show that MDSC increase fatty acid uptake and fatty acid oxidation (FAO) to support their immunosuppressive functions. Inhibition of FAO promoted a therapeutic T cell-mediated anti-tumor effect. Here, we sought to determine the mechanisms by which tumor-infiltrating MDSC increase the uptake of exogenous lipids and undergo metabolic and functional reprogramming to become highly immunosuppressive cells. The results showed that tumor-derived cytokines (G-CSF and GM-CSF) and the subsequent signaling through STAT3 and STAT5 induce the expression of lipid transport receptors with the resulting increase in the uptake of lipids present at high concentrations in the tumor microenvironment. The intracellular accumulation of lipids increases the oxidative metabolism and activates the immunosuppressive mechanisms. Inhibition of STAT3 or STAT5 signaling or genetic depletion of the fatty acid translocase CD36 inhibits the activation of oxidative metabolism and the induction of immunosuppressive function in tumor-infiltrating MDSC and results in a CD8⁺ T cell-dependent delay in tumor growth. Of note, human tumor-infiltrating and peripheral blood MDSC also upregulate the expression of lipid transport proteins, and lipids promote the generation of highly suppressive human MDSC in vitro. Our data therefore provide a mechanism by which tumor-derived factors and the high lipid content in the tumor microenvironment can cause the profound metabolic and functional changes found in MDSC and suggest novel approaches to prevent or reverse these processes. These results could further enhance the efficacy of cancer immunotherapy.

Neoplasms of the canine urinary bladder

Evaluation of histologic data obtained from 90 breeds of dogs with 3,837 neoplasms collected over 10 years (1961-1971) revealed 21 cases of urinary bladder neoplasmia in 14 breeds of dogs. There was no breed predispostion. The mean age of dogs with urinary bladder neoplasia was 9.5 years; 6 were males, 13 were females, and 2 were spayed females.

Carotid body tumors in the dog: a review and report of four cases

Of 3,837 canine neoplasms from case records at Kansas State University, only 4 were of carotid body tumors. Information on these 4 cases, added to that on 18 cases already reported, indicated that such tumors are found most frequently in old dogs, principally in brachycephalic breeds. Although predisposition toward the male sex has been suggested for tumors of the chemoreceptor system, none was observed for carotid body tumors. Multicentricity apparently is not uncommon for chemoreceptor tumors; 9 of the 22 dogs simultaneously had aortic body tumor.