CD200 is overexpressed in the pancreatic tumor microenvironment and predictive of overall survival

Pancreatic cancer is an aggressive disease with a 5 year survival rate of 13%. This poor survival is attributed, in part, to limited and ineffective treatments for patients with metastatic disease, highlighting a need to identify molecular drivers of pancreatic cancer to target for more effective treatment. CD200 is a glycoprotein that interacts with the receptor CD200R and elicits an immunosuppressive response. Overexpression of CD200 has been associated with differential outcomes, depending on the tumor type. In the context of pancreatic cancer, we have previously reported that CD200 is expressed in the pancreatic tumor microenvironment (TME), and that targeting CD200 in murine tumor models reduces tumor burden. We hypothesized that CD200 is overexpressed on tumor and stromal populations in the pancreatic TME and that circulating levels of soluble CD200 (sCD200) have prognostic value for overall survival. We discovered that CD200 was overexpressed on immune, stromal, and tumor populations in the pancreatic TME. Particularly, single-cell RNA-sequencing indicated that CD200 was upregulated on inflammatory cancer-associated fibroblasts. Cytometry by time of flight analysis of PBMCs indicated that CD200 was overexpressed on innate immune populations, including monocytes, dendritic cells, and monocytic myeloid-derived suppressor cells. High sCD200 levels in plasma correlated with significantly worse overall and progression-free survival. Additionally, sCD200 correlated with the ratio of circulating matrix metalloproteinase (MMP) 3: tissue inhibitor of metalloproteinase (TIMP) 3 and MMP11/TIMP3. This study highlights the importance of CD200 expression in pancreatic cancer and provides the rationale for designing novel therapeutic strategies that target this protein.

Tomatidine targets ATF4-dependent signaling and induces ferroptosis to limit pancreatic cancer progression

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer with high metastasis and therapeutic resistance. Activating transcription factor 4 (ATF4), a master regulator of cellular stress, is exploited by cancer cells to survive. Prior research and data reported provide evidence that high ATF4 expression correlates with worse overall survival in PDAC. Tomatidine, a natural steroidal alkaloid, is associated with inhibition of ATF4 signaling in multiple diseases. Here, we discovered that in vitro and in vivo tomatidine treatment of PDAC cells inhibits tumor growth. Tomatidine inhibited nuclear translocation of ATF4 and reduced the transcriptional binding of ATF4 with downstream promoters. Tomatidine enhanced gemcitabine chemosensitivity in 3D ECM-hydrogels and in vivo. Tomatidine treatment was associated with induction of ferroptosis signaling validated by increased lipid peroxidation, mitochondrial biogenesis, and decreased GPX4 expression in PDAC cells. This study highlights a possible therapeutic approach utilizing a plant-derived metabolite, tomatidine, to target ATF4 activity in PDAC.

Abstract B077: Tomatidine targets ATF4-dependent signaling to limit pancreatic cancer in the tumor microenvironment

Background: Pancreatic ductal adenocarcinoma (PDAC), comprising of 90% pancreatic cancer malignancies, is a highly aggressive cancer with a five-year survival rate of 10.8%. Current therapies include surgical resection and chemotherapy, which are mostly ineffective because of metastasis and an immunosuppressive tumor microenvironment (TME). Tomatidine, a natural metabolite present in the tomato plant, has anti-cancer and anti-inflammatory properties. Further, tomatidine has been reported to possibly correlate with inhibition of Activating Transcription Factor 4 (ATF4)-dependent signaling in multiple diseases such as skeletal muscle atrophy and dengue virus infection. ATF4, a master regulator of cellular stress, has been implicated in different cancers including PDAC by promoting cell survival, inducing resistance towards commonly used chemotherapeutic agents as well as by affecting anti-tumor immunity. Hypothesis: We hypothesize that tomatidine can inhibit pancreatic cancer by regulating ATF4-dependent signaling. Methods: Pancreatic tumor cell lines were assayed for cell growth after tomatidine treatment. Subcutaneous tumor-bearing C57BL/6 mice and athymic mice were treated with 5 mg/kg daily i.p. injections of tomatidine or vehicle. Orthotopic tumor bearing C57BL/6 mice were treated with either 5 mg/kg tomatidine daily alone, 10 mg/kg gemcitabine twice per week alone or both in combination, respectively via i.p. injections and assessed in comparison to vehicle. To assess ATF4-dependent signaling, protein and RNA expression of ATF4 and related genes as well as binding activity of ATF4 was evaluated via immunoblotting, Q-PCR analysis and chromatin immunoprecipitation. Further, healthy donor PBMCs were treated with tomatidine in presence of cytokines to observe myeloid derived suppressor cell (MDSC) differentiation. Results: We found that tomatidine can inhibit pancreatic tumor growth in vitro and in vivo. Tomatidine also enhanced the gemcitabine chemosensitivity in an orthotopic model of pancreatic cancer in vivo. However, there was little effect of tomatidine on tumor growth when pancreatic cancer cells were implanted into athymic mice, suggesting tomatidine may affect anti-tumor immunity. Tomatidine reduced phosphorylation of 4EBP1 (downstream of ATF4) in vitro and reduced mRNA expression of ATF4 and eIF4EBP1 in MT5 tumor-bearing mice treated with tomatidine. Further, tomatidine reduced the transcriptional binding activity of ATF4 with downstream genes such as eIF4EBP1. Tomatidine affected the rate of MDSC differentiation and reduced expression of ATF4 and related gene expression in immune cells. Conclusion: This study sheds light on tomatidine, a novel plant derived anti-cancer treatment that targets an upregulated pathway (ATF4 dependent signaling) in pancreatic cancer and can therefore be used to develop a novel therapeutic against the pancreatic tumor as well as its microenvironment.

Citation Format: Debasmita Mukherjee, Lena Bercz, Liliana D’Alesio, Jessica Wedig, Timothy Pfau, Molly Torok, Shrina Jasani, Thomas A. Mace. Tomatidine targets ATF4-dependent signaling to limit pancreatic cancer in the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B077.

Contraceptive challenges and the transgender individual

In recent years public awareness of healthcare disparities experienced by transgender individuals throughout the world have garnered increasing attention within the media and from health advocates. Despite this increasing awareness, a paucity of research data and clinical protocols of care for clinicians continues to exist, especially in regard to the transgender individual’s family planning needs. Clinicians should be on the forefront of promoting strategies that forge a meaningful and collaborative relationship with the transgender man, including as he transitions through to the menopause and his sexual and reproductive healthcare needs. Unfortunately, despite best efforts to address the health concerns of transgender men in midlife, including their contraceptive needs and pregnancy desires, there is currently a paucity of research. Although hormonal contraceptives are not an option for this group of individuals, especially those on masculinizing hormones, IUD’s, both copper containing and progestin containing, should be considered for those with intact pelvic organs. For this group of transgender men with potential for pregnancy who have either completed their family or choose not to give birth, sterilization can be offered. Regardless of where they identify along the gender spectrum, these midlife individuals with potential reproductive potential should have equitable access to and up to date counseling on their contraceptive options. This commentary addresses the contraceptive challenges of the midlife transgender man. (Note: Pronouns used in this article are he/him for cis and transgender men and she/her for cis and transgender women).

Localised mid-jejunal volvulus following intussusception and enteroplication in a dog

Ileocolic intussusception was successfully treated surgically by partial enterectomy and enteroplication in an 11-month-old, male neutered German shepherd dog. Segmental intestinal volvulus was identified in the same dog two months later and was managed successfully by a second partial enterectomy. The dog made an uneventful recovery and was free of clinical disease six months after the second surgery. Both conditions are reviewed in this case report and a possible relationship between these two episodes in this dog is discussed.