Murine pancreatic adenocarcinoma dampens SHIP-1 expression and alters MDSC homeostasis and function
Shari Pilon-Thomas1, Nadine Nelson, Nasreen Vohra
1Immunology Program, H. Lee Moffitt Comprehensive Cancer Center and Research Institute, Tampa, Florida, United States of America.
Background:
Pancreatic cancer is one of the most aggressive cancers, with tumor-induced myeloid-derived suppressor cells (MDSC) contributing to its pathogenesis and ineffective therapies. In response to cytokine/chemokine receptor activation, src homology 2 domain-containing inositol 5'-phosphatase-1 (SHIP-1) influences phosphatidylinositol-3-kinase (PI3K) signaling events, which regulate immunohomeostasis. We hypothesize that factors from murine pancreatic cancer cells cause the down-regulation of SHIP-1 expression, which may potentially contribute to MDSC expansion, and the suppression of CD8(+) T cell immune responses. Therefore, we sought to determine the role of SHIP-1 in solid tumor progression, such as murine pancreatic cancer.
Methodology And Principal Findings:
Immunocompetent C57BL/6 mice were inoculated with either murine Panc02 cells (tumor-bearing [TB] mice) or Phosphate Buffer Saline (PBS) (control mice). Cytometric Bead Array (CBA) analysis of supernatants of cultured Panc02 detected pro-inflammatory cytokines such as IL-6, IL-10 and MCP-1. TB mice showed a significant increase in serum levels of pro-inflammatory factors IL-6 and MCP-1 measured by CBA. qRT-PCR and Western blot analyses revealed the in vivo down-regulation of SHIP-1 expression in splenocytes from TB mice. Western blot analyses also detected reduced SHIP-1 activity, increased AKT-1 and BAD hyper-phosphorylation and up-regulation of BCL-2 expression in splenocytes from TB mice. In vitro, qRT-PCR and Western blot analyses detected reduced SHIP-1 mRNA and protein expression in control splenocytes co-cultured with Panc02 cells. Flow cytometry results showed significant expansion of MDSC in peripheral blood and splenocytes from TB mice. AutoMACS sorted TB MDSC exhibited hyper-phosphorylation of AKT-1 and over-expression of BCL-2 detected by western blot analysis. TB MDSC significantly suppressed antigen-specific CD8(+) T cell immune responses in vitro.
Conclusion/Significance:
SHIP-1 may regulate immune development that impacts MDSC expansion and function, contributing to pancreatic tumor progression. Thus, SHIP-1 can be a potential therapeutic target to help restore immunohomeostasis and improve therapeutic responses in patients with pancreatic cancer.
Insights
Pancreatic cancer progression is linked to reduced SHIP-1, leading to myeloid-derived suppressor cells (MDSC) expansion and suppressed CD8(+) T cells. Restoring SHIP-1 may improve immune responses in pancreatic cancer patients.
Area of Science:
- Immunology
- Oncology
- Molecular Biology
Background:
- Pancreatic cancer is aggressive, with myeloid-derived suppressor cells (MDSC) hindering treatment.
- Src homology 2 domain-containing inositol 5'-phosphatase-1 (SHIP-1) regulates immune homeostasis via PI3K signaling.
- SHIP-1's role in pancreatic cancer-induced MDSC expansion and T cell suppression is unclear.
Purpose of the Study:
- To investigate the role of SHIP-1 in pancreatic cancer progression.
- To determine if pancreatic cancer cells down-regulate SHIP-1, promoting MDSC expansion.
- To assess SHIP-1's impact on CD8(+) T cell immune responses.
Main Methods:
- Murine pancreatic cancer model (Panc02 cells) and control groups.
- Cytometric Bead Array (CBA) for cytokine analysis (IL-6, IL-10, MCP-1).
- qRT-PCR and Western blot for SHIP-1, AKT-1, BAD, and BCL-2 expression and activity.
- Flow cytometry for MDSC quantification and CD8(+) T cell suppression assays.
Main Results:
- Tumor-bearing mice showed increased IL-6 and MCP-1 serum levels.
- Splenocytes from tumor-bearing mice exhibited down-regulated SHIP-1 expression and activity, with increased AKT-1/BAD phosphorylation and BCL-2 expression.
- MDSC significantly expanded in tumor-bearing mice and suppressed CD8(+) T cell responses in vitro.
Conclusions:
- SHIP-1 down-regulation in pancreatic cancer contributes to MDSC expansion and immune suppression.
- Restoring SHIP-1 function may be a therapeutic strategy for pancreatic cancer.
- Targeting SHIP-1 could help re-establish immune homeostasis and enhance treatment efficacy.
