Pancreatic cancer is the fourth leading cause of cancer death. Existing therapies only moderately improve pancreatic ductal adenocarcinoma (PDAC) patient prognosis. The present study investigates the importance of the polyamine metabolism in the pancreatic tumor microenvironment. Relative mRNA expression analysis identified differential expression of polyamine biosynthesis, homeostasis, and transport mediators in both pancreatic epithelial and stromal cells from low-grade pancreatic intraepithelial neoplasia (PanIN-1) or primary PDAC patient samples. We found dysregulated mRNA levels that encode for proteins associated with the polyamine pathway of PDAC tumors compared to early lesions. Next, bioinformatic databases were used to assess expression of select genes involved in polyamine metabolism and their impact on patient survival. Higher expression of pro-polyamine genes was associated with poor patient prognosis, supporting the use of a polyamine blockade therapy (PBT) strategy for inhibiting pancreatic tumor progression. Moreover, PBT treatment of syngeneic mice injected intra-pancreatic with PAN 02 tumor cells resulted in increased survival and decreased tumor weights of PDAC-bearing mice. Histological assessment of PBT-treated tumors revealed macrophage presence and significantly increased expression of CD86, a T cell co-stimulatory marker. Collectively, therapies which target polyamine metabolism can be used to disrupt tumor progression, modulate tumor microenvironment, and extend overall survival.
Transcriptional profiling of pre- and post-malignant colorectal cancer (CRC) lesions enable temporal monitoring of molecular events underlying neoplastic progression. However, the most widely used transcriptomic dataset for CRC, TCGA-COAD, is devoid of adenoma samples, which increases reliance on an assortment of disparate microarray studies and hinders consensus building. To address this, we developed a microarray meta-dataset comprising 231 healthy, 132 adenoma, and 342 CRC tissue samples from twelve independent studies. Utilizing a stringent analytic framework, select datasets were downloaded from the Gene Expression Omnibus, normalized by frozen robust multiarray averaging and subsequently merged. Batch effects were then identified and removed by empirical Bayes estimation (ComBat). Finally, the meta-dataset was filtered for low variant probes, enabling downstream differential expression as well as quantitative and functional validation through cross-platform correlation and enrichment analyses, respectively. Overall, our meta-dataset provides a robust tool for investigating colorectal adenoma formation and malignant transformation at the transcriptional level with a pipeline that is modular and readily adaptable for similar analyses in other cancer types.
Background: While inflammation is associated with pancreatic cancer, the underlying mechanisms leading to cancer initiation are still being delineated. Eosinophils may promote or inhibit tumor growth, although the specific role in pancreatic cancer has yet to be determined. Eosinophil-supporting cytokine interleukin-5 and receptor are likely to have a role, but the significance in the pancreatic cancer microenvironment is unknown. Methods: Genetically engineered Akt1 Myr /KRas G12D and KRas G12D mice were used to model changes induced by chronic inflammation. Tissue samples were collected to analyze the tumor microenvironment and infiltration of immune cells, whereas serum was collected to analyze cytokine and amylase activity in the inflammatory model. The expression of IL-5R and the effects of IL-5 were analyzed in human and murine tumor cells. Results: Compound Akt1 Myr /KRas G12D mice, compared to single KRas G12D or Akt1 Myr mice, exhibited increased tissue damage after repeat inductions of inflammation, and had accelerated tumor development and metastasis. M2 macrophages and newly identified eosinophils co-localized with fibrotic regions rather than infiltrating into tumors, consistent with immune cell privilege. The majority of eosinophils found in the pancreas of Akt1 Myr / KRas G12D mice with chronic inflammation lacked the cytotoxic NKG2D marker. IL-5 expression was upregulated in pancreatic cells in response to inflammation, and then diminished in advanced lesions. Although not previously described in pancreatic tumors, IL-5Rα was increased during mouse pancreatic tumor progression and expressed in human pancreatic ductal adenocarcinomas (7 of 7 by immunohistochemistry). IL-5 stimulated tumor cell migration and activation through STAT5 signaling, thereby suggesting an unreported tumor-promoting role for IL-5Rα in pancreatic cancer. Conclusions: Chronic inflammation induces increased pancreatic cancer progression and immune cells such as eosinophils are attracted to areas of fibrosis. Results suggest that IL-5 in the pancreatic compartment stimulates increased IL-5Rα on ductal tumor cells to increase pancreatic tumor motility. Collectively, IL-5/IL-5Rα signaling in the mouse and human pancreatic tumors microenvironment is a novel mechanism to facilitate tumor progression.
INTRODUCTION: Bile acids (BAs) arising from duodenogastric reflux are known to facilitate gastric cancer (GC) development. Although BAs traditionally contribute to carcinogenesis through direct cellular cytotoxicity, increasing evidence implicates nuclear and membrane BA receptors (BARs) as additional factors influencing cancer risk. Indeed, some BARs are already linked with GC, but conflicting evidence and lack of information regarding other endogenous BARs warrant further investigation. In this study, we meta-analyzed multiple data sets to identify clinically relevant relationships between BAR expression and prognosis, clinicopathology, and activity in GC. METHODS: We collected transcriptomic data from the Gene Expression Omnibus and The Cancer Genome Atlas to analyze associations between BAR expression and GC prognosis, subtype, and clinicopathology. We also used Ingenuity Pathway Analysis to assess and predict functions, upstream regulators, and downstream mediators of membrane and nuclear BARs in GC. RESULTS: BARs showed differential distribution in GC; membrane BARs (G protein-coupled BAR 1, sphingosine-1-phosphate receptor 2, and cholinergic receptor muscarinic 2) were enriched in diffuse-, genome-stable, and mesenchymal-type tumors, whereas nuclear BARs (pregnane-X-receptor, constitutive androstane receptor, and farnesoid-X-receptor) were enriched in chromosome instability and metabolic subtypes. High expression of all membrane but not nuclear BARs was associated with poor prognosis and unfavorable GC clinicopathologic features. Similarly, expression patterns of membrane but not nuclear BARs varied geographically, aligning with Helicobacter pylori infection and GC mortality rates. Finally, GC-related oncogenes, namely transforming growth factor β1, were associated with membrane BARs, whereas many metabolic-associated genes were associated with nuclear BARs. DISCUSSION: Through transcriptomic meta-analysis, we identified distinct expression profiles between nuclear and membrane BARs that demonstrate prognostic relevance and warrant further investigation.
Existing therapeutics have failed to improve pancreatic ductal adenocarcinoma (PDAC) patient outcomes, in part due to tumor associated immune suppression and upregulation of compensatory mechanisms. KRAS and c-MYC are important oncogenes in PDAC linked to tumor immune suppression. We describe the use of difluoromethylornithine (DFMO) and a c-RAF inhibitor (GW5074) to indirectly target c-MYC and KRAS, respectively. DFMO in combination with GW5074 was tested for ability to improve pancreatic cancer outcomes. Pancreatic cancer cells showed decreased cell viability and increased apoptosis in response to a combination of DFMO + GW5074. In vivo orthotopic models of pancreatic tumors had decreased tumor weight in DFMO + GW5074 treated mice, when compared to control group. However, only treatment with single agent DFMO resulted in improved survival of immunocompetent pancreatic tumor bearing mice with respect to control, in contrast to treatment with GW5074 alone or DFMO + GW5074. To understand why the in vivo data was contrary to in vitro results, immunohistochemical analysis of immune cells in the tumor microenvironment was used to reveal increased expression of markers associated with anti-tumor effects such as CD86, CD3, CD4 and CD8 in DFMO treated tumors. Tumors treated with DFMO also displayed decreased expression of MYC, suggesting that DFMO-associated MYC suppression could be linked to decreased immune suppression in the tumor microenvironment and improved survival. In contrast, GW5074 treatment maintained MYC expression in tumors. Overall, the present study points to DFMO being an immunomodulatory agent, and a need for further understanding of DFMO-based therapeutic strategies in PDAC. Citation Format: Sai Preethi Nakkina, Sarah B. Gitto, Jordan M. Beardsley, Veethika Pandey, Michael M. Rohr, Jignesh Parikh, Otto Phanstiel, Deborah A. Altomare. DFMO based improvement in survival of pancreatic cancer-bearing mice is associated with modulation of immune suppression in the tumor microenvironment [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 3546.
There remains an urgent need to target pancreatic tumor cells using innovative strategies. KRAS and MYC, are important oncogenes in pancreatic ductal adenocarcinoma (PDAC) which pose a challenge to successful treatment of PDAC. Our previous studies have shown that inhibition of ornithine decarboxylase 1 (ODC1) using difluoromethylornithine (DFMO) decreases MYC expression and tumorigenesis. GW5074 can modulate RAF1, a downstream effector of KRAS. Here we test the responsiveness of pancreatic tumor cells treated with DFMO alone and in combination with GW5074. We used an orthotopic animal model of pancreatic tumor using KRas-driven murine pancreatic cancer cells (PanO2) to test the effects of these compounds on tumor microenvironment and overall survival. Cellular and molecular changes in the tumor microenvironment were assessed using immunohistochemistry. The results showed an inhibition of pancreatic cancer cell viability in DFMO and DFMO+GW5074 treatment groups in vitro, with a significant decrease in tumor weight compared to control treatment group in vivo. However, in terms of overall survival, DFMO alone resulted in a dramatic increase in survival compared to control treatment group. Interestingly, GW5074 alone or DFMO in combination with GW5074 did not result in a detectable effect on survival. Further investigation of immune cells in the tumor microenvironment revealed that standalone DFMO treatment was associated with an increase in infiltration of macrophages, T cell costimulatory marker CD86 and T cell markers (CD3, CD4 and CD8) compared to control and GW5074 treated groups. Additionally, DFMO is associated with decreased MYC expression compared to control and GW5074 treated groups. In conclusion, DFMO decreased MYC expression and associated immune suppression in the PDAC microenvironment. In contrast standalone GW5074 treatment resulted in maintenance of MYC expression and worse survival. In conclusion, the present study highlights the success of DFMO in PDAC treatment in part through downregulation of MYC and a decrease in associated immune suppression. Citation Format: Sai Preethi Nakkina, Sarah B. Gitto, Veethika Pandey, Jordan M. Beardsley, Michael W. Rohr, Jignesh G. Parikh, Otto Phanstiel, Deborah A. Altomare. DFMO mediated improvement in survival of an orthotopic model of pancreatic cancer is associated with modulating immune suppression in the tumor microenvironment [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-119.
Pancreatic cancer is the fourth leading cause of cancer death in the United States, with a five-year survival rate of less than 8%. Existing therapies have failed to improve pancreatic ductal adenocarcinoma (PDAC) patient prognosis. The dense desmoplastic reaction which occurs in PDAC makes it challenging for drugs and immune cells to infiltrate the fibrotic barrier. There is a need to exploit lesser explored targets in PDAC that can influence both the tumor and its microenvironment. One such avenue could be via targeting polyamine metabolism which is upregulated in pancreatic tumors. Though aberrant polyamine upregulation in pancreatic tumors has been known for decades, there has been little progress in translating this information into a PDAC therapeutic strategy. Additionally, there is a dearth of information regarding the dysregulation of polyamine metabolism in human PDAC and its association with clinical outcomes. Thus far, preclinical studies targeting polyamines using polyamine blockade therapy (PBT) has improved survival of pancreatic tumor bearing mice. Literature shows effectiveness of PBT in eliciting an anti-tumor immune response in other tumor types. Whether these results translate to the immune-privileged PDAC microenvironment need to be determined. The present study explores polyamine gene expression in human PDAC samples by mRNA expression analysis of frozen PDAC and Pancreatic intraepithelial neoplasia (PanIN). The Cancer Genome Atlas in the public domain was used to identify clinical outcomes of PDAC patients associated with select polyamine gene expression. Further, the anti-tumor effects of PBT and associated tumor microenvironment changes were identified using in vivo PDAC models and histological assessment. Polyamine dysregulation was found to be evident in human PDAC progression. Also, increased expression of certain polyamine-related genes was associated with poorer survival of pancreatic cancer patients. When targeting polyamines using PBT in immunocompetent C57Bl/6 mice with Pan02 tumor cells injected in the pancreas, PBT significantly increased overall survival. PBT also resulted in an increase in the infiltration of macrophages (F4/80) and expression of T-cell co-stimulatory marker (CD86) as assessed by immunohistochemistry and further quantification of imaging. Based on these changes, we hypothesized that PBT could prime the tumor microenvironment to be more susceptible to existing therapeutics. In conclusion, targeting polyamines using PBT results in increased survival and immune modulation in PDAC. Citation Format: Sai Preethi Nakkina, Sarah B. Gitto, Veethika Pandey, Jignesh G. Parikh, Dirk Geerts, Kenneth P. Olive, Otto Phanstiel, Deborah A. Altomare, Carlo Maurer. Differential expression of polyamine pathways in human pancreatic tumor progression and effects of polyamine blockade therapy on the in vivo pancreatic tumor microenvironment [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-120.
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