Abstract 3153: Targeting the stress response kinase GCN2 to restore immunity in the tumor microenvironment

Recent advances in cancer metabolism suggest that targeting amino acid metabolism represents a promising strategy for the development of novel therapeutic agents. Tumor, stromal and myeloid-derived suppressor cells (MDSC) within the tumor microenvironment (TME) create a nutrient-poor environment that inhibit immune function and support tumor growth. GCN2 (general control nonderepressible 2), a stress response kinase, plays a key role in maintaining cellular homeostasis under a wide range of stressors. Phosphorylation of GCN2 (pGCN2) in response to stress leads to inhibition of global protein synthesis and subsequently leads to 1) T cell anergy and apoptosis, 2) enhanced MDSC-dependent immune suppression and 3) tumor cell survival. Collectively, these roles suggest that GCN2 inhibition could have both a direct anticancer and an immune-activating effect. Treating nutrient-deprived T cells in vitro with a RAPT GCN2 inhibitor (RPT-GCN2i) rescued CD4+ and CD8+ T cell proliferation and effector functions. The RPT-GCN2i also reversed T cell suppression mediated by MDSCs derived from healthy donors or cancer patients. Using syngeneic mouse tumor models, we demonstrated that translational induction of activating transcription factor 4 (ATF4) is a strong marker of GCN2 pathway activation in vivo. Oral administration of an RPT-GCN2i exhibited notable drug-target occupancy and potently inhibited GCN2 kinase and ATF4 in the TME. RPT-GCN2i as a single agent and in combination with checkpoint blockade or angiogenesis inhibitor (anti-VEGFR) led to delays in tumor growth rate in various syngeneic tumor models. In addition, GCN2 inhibition redirected MDSC within the TME from a suppressive to inflammatory phenotype through downregulation of Arg1 and iNOS. Our results show that inhibition of GCN2 is an attractive approach for enhancing antitumor immune response and therefore GCN2 is a promising therapeutic target for the treatment of cancer.

Citation Format: Lisa Marshall, Buvana Ravishankar, Urvi Kolhatkar, Mengshu Xu, Lavanya Adusumilli, Deepa Pookot, Thant Zaw, Chandru Ramana, Raashi Sreenivasan, Mikhail Zibinsky, Jeffrey Jackson, Grant Shibuya, Paul Leger, Omar Robles, Anqi Ma, Andrew Ng, Anton Shakhmin, Justy Guagua, Scott Jacobson, Steve Wong, Delia Bradford, Tracy L. McGaha, M Teresa Ciudad, James E. Talmadge, Holly C. Britton, George Katibah, Gene Cutler, David Wustrow, Paul D. Kassner, Dirk G. Brockstedt. Targeting the stress response kinase GCN2 to restore immunity in the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3153.

Antimicrobial efficacy of aqueous ozone in combination with short chain fatty acid buffers

Background

Mitigating surface contamination by microbes such as S. aureus, Salmonella enterica, or Klebsiella pneumoniae, is an ongoing problem in hospital and food production environments.

Aim

To determine whether addition of buffering solution to source water used for manufacture of aqueous ozone increases ozone efficacy against ozone-resistant bacterial species.

Methods

Antimicrobial effects of aqueous ozone were studied in combination with acetate, propionate, or butyrate short chain fatty acids (SCFA) as well as citrate or oxalate buffer formulations against Staphylococcus aureus on glass coupons. Aqueous ozone combined with an acetate buffer was also evaluated against Salmonella enterica and Klebsiella pneumoniae.

Findings

The acetate, propionate, and butyrate buffered aqueous ozone combinations had a significant 3-4 log reduction of S. aureus (P<0.05) colony forming unit (CFU), while citrate or oxalate buffered aqueous ozone, although statistically significant versus buffer alone, had less activity. Treatment of S. aureus, S. enterica, or K. pneumoniae with acetate buffered aqueous ozone also resulted in a 4 log or greater reduction in CFUs post-treatment for all three species, versus treatment with water alone.

Conclusions

All buffer systems tested had a significantly greater reduction in CFUs following treatment with the combination of buffer and ozone, compared to treatment with buffer or ozone individually, which has not been previously reported for hard surfaces. These results suggest that SCFA buffered ozone has greater anti-bacterial activity relative to either agent alone, and the activity is independent of the buffering activity. Thus, these formulations have potential to sanitize without residues, using an environmentally conscious formulation.

Dietary omega-3 and omega-6 polyunsaturated fatty acids modulate hepatic pathology

Recent evidence has suggested that dietary polyunsaturated fatty acids (PUFAs) modulate inflammation; however, few studies have focused on the pathobiology of PUFA using isocaloric and isolipidic diets and it is unclear if the associated pathologies are due to dietary PUFA composition, lipid metabolism or obesity, as most studies compare diets fed ad libitum. Our studies used isocaloric and isolipidic liquid diets (35% of calories from fat), with differing compositions of omega (ω)-6 or long chain (Lc) ω-3 PUFA that were pair-fed and assessed hepatic pathology, inflammation and lipid metabolism. Consistent with an isocaloric, pair-fed model we observed no significant difference in diet consumption between the groups. In contrast, the body and liver weight, total lipid level and abdominal fat deposits were significantly higher in mice fed an ω-6 diet. An analysis of the fatty acid profile in plasma and liver showed that mice on the ω-6 diet had significantly more arachidonic acid (AA) in the plasma and liver, whereas, in these mice ω-3 fatty acids such as eicosapentaenoic acid (EPA) were not detected and docosahexaenoic acid (DHA) was significantly lower. Histopathologic analyses documented that mice on the ω-6 diet had a significant increase in macrovesicular steatosis, extramedullary myelopoiesis (EMM), apoptotic hepatocytes and decreased glycogen storage in lobular hepatocytes, and hepatocyte proliferation relative to mice fed the Lc ω-3 diet. Together, these results support PUFA dietary regulation of hepatic pathology and inflammation with implications for enteral feeding regulation of steatosis and other hepatic lesions.

Abstract 245: Dietary long-chain omega-3 fatty acids reduce adipose inflammation in mammary tissue of mice fed moderate fat-isocaloric diets

Increased adipose tissue Inflammation and breast density; including ductal epithelial hyperplasia have been associated with increased risks for breast cancer. Omega 6 (ω6) and omega 3 (ω3) fatty acids (FAs); serve as substrates for pro-inflammatory and inflammation resolving mediators respectively, emphasizing the potential regulatory role for dietary intake of these FAs in inflammation. Western diets have a ω6:ω3 FA ratio of &gt;15:1 with low levels of long-chain (LC)-ω3FA. White adipose tissue inflammatory foci, characterized by crown-like structures (CLS) consisting of dead adipocytes and adjacent macrophages in breast tissue have been related to breast cancer risk in overweight and obese women presumably by the obesity-inflammation-aromatase axis. However, a role of dietary ω6:ω3 FA in adipose inflammation, independent of obesity is not clear. Herein, we examined effects of dietary ω6:ω3 ratio on the mammary tissue microenvironment and adipose inflammation using a moderate fat, iso-caloric diets, and pair-fed model. The LieberDeCarli diet containing 21:1 ratio of ω6:ω3 FA was used as a ω6 diet, whereas encapsulated fish oil containing a 3:1 ratio of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid was used to decrease ω6:ω3 ratio to 0.7:1 in the ω3 diet. Both iso-caloric diets contained 35.5% of calories derived from fat and were pair-fed to maintain iso-intake. Female BALB/c mice were established on the ω6 and ω3 diets for 10 weeks and weight gain and diet consumption monitored. There were no differences in the volume of diet consumed and weight gain between dietary groups. At autopsy, mammary fat pads (MFP) were collected and analyzed for fatty acid composition, histopathology, epithelial proliferation and macrophage infiltration. Arachidonic acid (AA) levels in the MFPs were not different between the groups but EPA and DHA were absent in the MFPs from the ω6 diet fed mice. Whereas, (2.41+/- 0.5) mole% of EPA and (1.52+/-0.29) mole% of DHA were detected in MFP of ω3 diet fed mice. The MFP of ω6 diet fed mice had significantly increased areas of unilocular adipocytes relative to adipocytes of the ω3 group. Similarly, ω6 diet fed mice had increased connective tissue in the ductal stroma, significantly higher numbers of proliferating cells in the ductal epithelium, as well as in adipose tissue area of MFP. In addition, ω6 diet fed mice had a significant increase in the numbers of CLS in mammary adipose tissue. In summary, our studies demonstrated that despite the comparable levels of AA in MFP in both of groups, the presence of LC-ω3 FA (EPA and DHA) was able to reduce inflammation in the MFP of ω3 diet fed mice, thus regulating the MFP microenvironments by reducing macrophage infiltration and ductal epithelial proliferation in an obesity-independent manner.

Citation Format: Saraswoti Khadge, Geoffrey M. Thiele, John Graham Sharp, Lynell W. Klassen, Timothy R. McGuire, Michael J. Duryee, Holly C. Britton, Alicia J. Dafferner, Jordan Beck, Paul Black, Concetta C. DiRusso, James E. Talmadge. Dietary long-chain omega-3 fatty acids reduce adipose inflammation in mammary tissue of mice fed moderate fat-isocaloric diets [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 245. doi:10.1158/1538-7445.AM2017-245

Abstract 4312: Preneoplastic activity of dietary poly unsaturated fatty acid (PUFA) regulation of organ and tissue microenvironments in an iso-caloric pair-fed mouse model

Diets containing omega-3 (ω3) PUFAs have health benefits due to their anti-inflammatory activity and lower risk of chronic conditions including cardiac, autoimmune and neoplastic diseases. This contrasts with ω6 PUFA containing Western diets, which are pro-inflammatory. Balancing the dietary ω6:ω3 ratio has been suggested to have cancer preventive and potentially therapeutic activity; however, the majority of these studies have not differentiated dietary PUFA content from obesity. Herein we examined the effects of the ω6:ω3 ratio in iso-caloric diets that were pair fed. These diets had 35.5% of calories from fat with an ω6:ω3 ratio in the ω6 and ω3 based diets of 42:1 and 1:1 respectively (confirmed by gas chromatography-mass spectrometry) using the liquid, Lieber DeCarli diet and fish oil substituting for 70% of olive oil. The ω3 diet contained eicosapentaenoic (EPA) and docosahexaenoic (DHA) acid at a 3:1 ratio, while the ω6 diet contained linoleic acid as the predominant ω6 PUFA and a low level of the ω3 PUFA, linolenic acid. After establishing female BALB/c mice on these diets, weight gain and diet consumption were monitored for 12 weeks, the mice sacrificed and the dietary effects on mammary gland and hepatic histopathology, leukocyte phenotypes and organ and tissue lipidomics determined. In association with pair feeding there were no differences in diet consumed (ω-3 diet used as baseline) and weight gain between cohorts. The cohort on the ω6 diet had depressed numbers of marrow progenitor cells and increased splenic subcapsular extramedullary hematopoiesis consistent with an inflammatory response, increased hepatocyte lipidosis, hypertrophy and multinucleation and increased hepatic vascularity with thicker intima. The ω-6 dietary cohort also had mammary fat pads (MFPs) with increased adipocytes in the tubular epithelium, stromal cellularity and epithelial tissue density. These mammary gland and hepatic histopathologic changes and subclinical inflammation are consistent with pre-neoplastic lesions and were accompanied by organ specific lipodemic changes. This included significant increases in arachidonic acid (AA) in the plasma, spleen and liver, but not MFPs, of the ω-6 cohort, and a significant increase in EPA and DHA levels in the plasma, spleen, MFPs and liver of the ω-3 cohort. In addition, the liver and MFPs had a significant increase in the ω3 PUFA, docosapentaenoic acid. In summary, our studies demonstrate that the dietary ratio of ω6:ω3, independent of obesity can regulate mammary gland and hepatocyte proliferation and subclinical inflammation in association with significant, organ specific increases in AA levels contributing to microenvironmental preneoplastic hyperplasia.

Citation Format: Saraswoti Khadge, Paul Black, Concetta DiRusso, Geoff Thiele, Lynell W. Klassen, J Graham Sharp, Timothy R. McGuire, Michael J. Duryee, Holly C. Britton, Alicia Dafferner, Jordan Beck, James E. Talmadge. Preneoplastic activity of dietary poly unsaturated fatty acid (PUFA) regulation of organ and tissue microenvironments in an iso-caloric pair-fed mouse model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4312.

Abstract 1167: Osteolysis, splenic and hepatic extramedullary hematopoiesis, MDSCs, tumor growth, and metastases by orthotopic mammary tumors are increased by alcohol consumption and fatty diets

Fatty diets can induce low-grade inflammation that we report is increased by chronic alcohol consumption (CAC). CAC as 16.6% of total calories when administered in combination with the Lieber-DeCarli high-fat diet increases inflammation included hepatic and splenic extramedullary hematopoiesis (EMH) as assessed by flow cytometry, immunohistochemistry and a colony forming unit-granulocyte macrophage (CFU-GM) assay. Further, an increased number of hepatic myeloid derived suppressor cells (MDSCs) CD11b+Gr1+ cells that were predominantly Ly6cbr are observed. The increase in MDSCs is associated with an increased number of hepatic non-parenchymal cells including adipocytes (Oil Red O). Consistent with the increased number of hepatic MDSCs and EMH is a decrease in bone marrow cellularity and progenitor cells measured by flow cytometry (Lin-CD11b-Gr1-Sca-1+) and CFU-GM/femur. Unexpectedly, we observed demineralization and osteolytic lesions by micro computed tomography (micro CT) in all bones examined including femur, tibia, fibula and vertebral column that was associated with osteoclast activity (Trap+). Osteolysis was most notable in the fibula and vertebral spurs associated with osteoclast channels, and the demineralization appeared to be associated with areas of active myelopoiesis. The low grade, chronic inflammation associated with the Lieber-DeCarli fatty diet and CAC accelerated the induction of orthotopic 4T1 mammary tumors, resulting in extensive bone osteolysis, demineralization and increased metastases at aberrant sites including splenic, cardiac, hepatic, and extensive lymph node foci in addition to peritoneal and pleural effusions. The latter were haemorrhagic with a predominant nucleated cell infiltrate composed of bands, segs and myelocytes, supporting EMH. These results support the suggestion that a high-fat diet and CAC together increase tumor induction, metastasis and pathology in association with MDSC mobilization, expansion and EMH resulting in increased numbers of osteoclasts, associated bone demineralization and suppression of T-cell frequency and function. These results support the development of combination therapy strategies incorporating multiple molecular therapeutics that inhibit OCs, MDSCs and their associated mediators.

Citation Format: Anand Dusad, Saraswoti Khadge, Geoffrey M. Thiele, Michael J. Duryee, Holly C. Britton, Lynell W. Klassen, Alicia J. Dafferner, Tracy Farrell, Timothy R. McGuire, Carlos D. Hunter, Karen C. Easterling, Karen J. O'Kane, John Graham Sharp, James E. Talmadge. Osteolysis, splenic and hepatic extramedullary hematopoiesis, MDSCs, tumor growth, and metastases by orthotopic mammary tumors are increased by alcohol consumption and fatty diets. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1167. doi:10.1158/1538-7445.AM2014-1167

Abstract 4363: Tumor regulation of myeloid-derived suppressor cell proliferation, circulation and apoptosis

In response to stress, myeloid progenitor cells (MPCs) mobilize and establish sites of extramedullary hematopoiesis (EMH) within lymphoid and parenchymal organs. We report that the spleens of 4T1 mammary tumor-bearing (TB) mice are the primary site of MPC proliferation resulting in extensive EMH in association with decreased apoptosis, increased myeloid cell survival, and increased hematopoietic growth factor (GF) transcription by the tumor cells. MPC trafficking and survival differs between TB and naïve mice with leukocyte arrest in the lungs of naïve mice and accumulation in the splenic red pulp of TB mice with little marrow or tumor arrest or proliferation. Indeed, despite the high levels of GF transcription by tumor cells MDSC apoptosis in tumors is very high perhaps due to the high levels of NOS2 in the tumor microenvironment. Further myeloid proliferation directly correlates with the decrease in T-cell frequency, which is associated with extrathymic, but not thymic T-cell proliferation. In summary, tumor cytokines regulate a dynamic relationship between MPCs and T-cells regulating their proliferation, trafficking, accumulation, apoptosis, and survival.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4363. doi:1538-7445.AM2012-4363