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Published on: July 20, 2019
Modulating the tumor microenvironment in a mouse model of colon cancer using a combination of HIF-1α inhibitors and
Leila Rostamizadeh1, Mina Ramezani2, Hannaneh Monirinasab3
1Department of Molecular Medicine, Faculty of Advanced Medical Science, Tabriz University of Medical Sciences, Golgasht Avenue, Tabriz, Iran.
Abstract:
The immunosuppressive tumor microenvironment (TME) plays a pivotal role in the response to various anticancer therapies, such as immune and chemotherapeutic agents. In this study, the synergistic effects of gene-targeting HIF-1α siRNA combined with Toll-Like Receptor 7 agonist on TME remodeling were investigated in a mouse model of colorectal cancer (CRC). A HIF-1α-specific siRNA duplex was formulated based on the ionic gelation of tripolyphosphate (TPP) with cationic chitosan (CH) as a nanoplex and evaluated in terms of size, charge, polydispersity index and gel retardation assay. MTT assay was conducted to assess the cytotoxicity of the specific siRNA duplex against CT26 cells. Hypoxic condition was generated to evaluate the gene and protein expression levels of HIF-1α, respectively. CT26 mouse model was established to assess the synergistic effect of silencing HIF-1α combined with oxaliplatin (OXA) and imiquimod (IMQ) on tumor growth. The mean diameter of the CH/siRNA nanoparticles was 243 ± 6 nm, as confirmed with Micrograph scanning electron microscope. There were no significant differences observed between the CT26 cells treated with nanoparticles alone and the untreated cells, indicating that these nanoparticles are safe and physiologically biocompatible (p ≥ 0.05). Triple combination therapy involving HIF-1α siRNA, OXA, and IMQ significantly retarded tumor growth and led to elevated levels of cytokines linked to cellular immunity (INF-γ and IL-12) compared with those in the other groups (P < 0.05). The positive correlation coefficient (r = 0.68) between tumor size and HIF-1α expression levels was statistically significant (P = 0.003). Compared with those in the control group, the expression levels of the anti-inflammatory cytokines IL-10 and IL-4 significantly decreased (P < 0.05). In conclusion, our findings suggest that inhibiting HIF-1α could serve as a rational strategy to enhance the antitumor response in the TME.
Insights
Inhibiting hypoxia-inducible factor-1 alpha (HIF-1α) via siRNA nanoparticles combined with chemotherapy and immunotherapy effectively remodels the immunosuppressive tumor microenvironment (TME). This triple therapy significantly reduced colorectal cancer growth and boosted anti-tumor immunity.
Area of Science:
- Oncology
- Nanotechnology
- Immunotherapy
Background:
- The tumor microenvironment (TME) is a key factor in the efficacy of anticancer therapies.
- Hypoxia-inducible factor-1 alpha (HIF-1α) promotes an immunosuppressive TME, hindering treatment responses.
Purpose of the Study:
- To investigate the synergistic effects of HIF-1α siRNA nanoparticles combined with oxaliplatin and imiquimod on TME remodeling in colorectal cancer (CRC).
- To evaluate the safety and efficacy of chitosan/siRNA nanoparticles for delivering HIF-1α siRNA.
Main Methods:
- Formulation and characterization of chitosan/HIF-1α siRNA nanoparticles.
- In vitro cytotoxicity assessment using MTT assay on CT26 cells.
- In vivo evaluation in a CT26 mouse model of colorectal cancer, assessing tumor growth and cytokine profiles after triple combination therapy (HIF-1α siRNA, oxaliplatin, imiquimod).
Main Results:
- Chitosan/siRNA nanoparticles exhibited suitable physicochemical properties (243 nm diameter) and were biocompatible.
- Triple combination therapy significantly suppressed tumor growth and elevated pro-inflammatory cytokines (INF-γ, IL-12).
- HIF-1α inhibition correlated positively with tumor size and led to decreased anti-inflammatory cytokines (IL-10, IL-4).
Conclusions:
- Targeting HIF-1α with siRNA nanoparticles represents a promising strategy to overcome TME-mediated immunosuppression.
- The combination therapy enhances anti-tumor immune responses and retards colorectal cancer progression.
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