Multi-Stress Accelerated Liver Cancer Progression in Rats Treated with Diethylnitrosamine
Liver cancer remains a significant global health burden, with its progression influenced by a combination of genetic, environmental, and physiological factors. This study investigates the role of multi-stress conditions in accelerating diethylnitrosamine (DEN)-induced liver cancer in rats, emphasizing the interplay between chronic stress, immune dysregulation, and inflammatory responses.
Experimental Design and Model Establishment
Eighty-four 6-week-old male Wistar rats (120–180 g) were divided into three groups: normal control (NC), DEN-only, and multi-stress + DEN (MS + DEN). The NC group was maintained at room temperature (60–80% humidity) with standard diet and water. The DEN group received sterile water containing 0.1 mg/mL DEN daily for 20 weeks under the same environmental conditions as the NC group. The MS + DEN group was subjected to a combination of chronic cold stress (5–7°C, 25–32.8% humidity), electrical stimulation via food pads (escalating voltage and duration over three weeks), and forced swimming in cold water (15–25°C for 5 minutes weekly) alongside DEN administration.
Survival rates at the end of the 20-week experiment were 22/22 (100%) in the NC group, 16/22 (72.7%) in the DEN group, and 10/22 (45.5%) in the MS + DEN group, highlighting the detrimental impact of multi-stress on survival.
Pathological and Molecular Findings
Liver tissues were analyzed through histopathology, immunohistochemistry (IHC), and western blotting. The NC group showed no signs of malignancy, while the DEN group exhibited irregular hepatic architecture, necrosis, pseudo-lobule formation, and fibrosis. Strikingly, all MS + DEN rats (10/10) developed hepatocellular carcinoma (HCC) or bile duct epithelial cancer, with extensive fibrosis.
Signal transducer and activator of transcription 3 (STAT3), a key oncogenic driver in liver cancer, was markedly upregulated in stressed rats. IHC revealed strong STAT3 signals in both DEN and MS + DEN groups. Western blot quantification showed STAT3 levels in the MS + DEN group were 8.2-fold higher than NC and 2.3-fold higher than DEN-only rats, indicating multi-stress synergistically enhances DEN-induced STAT3 activation.
Immune Modulation and Regulatory T Cells (Tregs)
Flow cytometry analysis of peripheral blood mononuclear cells (PBMCs) demonstrated significant immune dysregulation under multi-stress. CD4+ Tregs (CD4+CD25+FoxP3+) were elevated in the MS + DEN group (7.36% of total CD4+ cells) compared to DEN (5.23%) and NC (2.79%) groups. Similarly, CD4+CD25+ Tregs constituted 14.52% of CD4+ cells in MS + DEN rats, versus 8.42% in DEN and 6.7% in NC groups. These findings suggest multi-stress exacerbates immunosuppression by expanding Treg populations, creating a permissive microenvironment for tumor progression.
Inflammatory Cytokine Profiling
Enzyme-linked immunosorbent assay (ELISA) quantified serum levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β. The MS + DEN group exhibited pronounced systemic inflammation: IL-6 (>10 pg/mL detection limit) and TNF-α (>20 pg/mL) levels were significantly higher than in DEN or NC groups. IL-1β (>15 pg/mL) followed a similar trend, corroborating the role of chronic inflammation in stress-accelerated carcinogenesis.
Mechanistic Insights and Traditional Chinese Medicine (TCM) Context
The study aligns with TCM principles of dynamic homeostasis, where disrupted balance between physiological systems predisposes to disease. Prior studies link single-stress models (e.g., restraint stress) to impaired antitumor immunity and HCC growth. However, this is the first demonstration that multi-stress—combining physical, environmental, and psychological stressors—synergizes with chemical carcinogens like DEN to drastically accelerate liver cancer.
Mechanistically, multi-stress amplifies DEN’s oncogenic effects through three interconnected pathways:
- STAT3 Hyperactivation: Persistent STAT3 signaling promotes cell survival, proliferation, and immune evasion.
- Treg Expansion: Increased Tregs suppress effector T-cell responses, enabling tumor immune escape.
- Chronic Inflammation: Elevated IL-6, TNF-α, and IL-1β foster a pro-tumorigenic milieu, driving fibrosis and malignant transformation.
Implications and Future Directions
This study underscores the importance of stress management in cancer prevention, particularly in high-risk populations. The multi-stress model recapitulates complex real-world scenarios where environmental, physiological, and psychological stressors coexist. Future research should explore interventions targeting STAT3, Tregs, or inflammatory cytokines to mitigate stress-induced cancer progression. Additionally, integrating TCM-based approaches to restore homeostasis could offer novel therapeutic strategies.
doi.org/10.1097/CM9.0000000000001504
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