Effects of Cisplatin in Combination with Hyperthermia on Biological Characteristics of Retroperitoneal Liposarcoma
Retroperitoneal liposarcoma (RPLS) is a malignant tumor originating from adipose tissue in the retroperitoneal space, accounting for nearly 70% of all retroperitoneal tumors. Despite its prevalence, RPLS lacks an optimal treatment strategy. Surgical resection (R0/R1) is currently the most effective therapy; however, the recurrence rate remains alarmingly high. Grossly incomplete surgical resection (R2) is a significant risk factor for early recurrence. Given the challenges in treating RPLS, there is a pressing need to explore alternative or adjunctive therapies to improve outcomes.
Cisplatin, a widely used platinum-based chemotherapeutic agent, has demonstrated efficacy in treating various malignancies. Hyperthermia (HT), which involves heating the body or a specific area above normal temperature, has also shown promise in cancer treatment. Malignant cells are particularly sensitive to heat, and HT can inhibit the DNA damage repair system in cancer cells. The temperature of HT can be adjusted based on treatment goals: higher temperatures (up to 80°C) can eradicate tumor cells entirely, while moderate temperatures (41–45°C) can target tumor cells without harming adjacent tissues. Additionally, HT has the potential to enhance the efficacy of chemotherapy and radiotherapy, reduce drug resistance, promote tumor cell apoptosis, and mitigate side effects. The combination of HT with cisplatin has been applied to treat various cancers, particularly those with poor prognoses, such as soft tissue sarcoma, colon, bladder, and liver cancer. However, the effects of cisplatin and HT, either alone or in combination, on RPLS remain unexplored. This study aimed to investigate the morphological and proliferative responses of RPLS cells to cisplatin and HT, as well as to explore the underlying molecular mechanisms.
The human RPLS SW872 cell line was utilized in this study. Cells were cultured in a complete medium containing 10% fetal bovine serum (FBS) and maintained in a CO2 incubator. Cell density was adjusted to 1 × 10^5/mL, and cells were seeded in 96-well plates for experiments. Cisplatin was applied at concentrations ranging from 1.25 to 80 µg/mL, and cytotoxicity was assessed using the Cell Counting Kit-8 (CCK-8) assay after 24 hours of incubation. Apoptosis was detected using flow cytometry with an Annexin V-FITC kit. For HT treatment, cells were exposed to temperatures of 41°C or 43°C for durations of 0.5 or 1 hour, followed by incubation at 37°C for varying periods. Total RNA was extracted, and gene expression levels of tumor necrosis factor (TNF)-α and glutathione peroxidase 4 (GPX4) were measured using quantitative real-time polymerase chain reaction (qPCR). Protein expression was analyzed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting.
The results demonstrated that cisplatin induced dose-dependent cytotoxicity in SW872 cells. At a concentration of 5 µg/mL, cisplatin achieved a 50% inhibition rate of cell viability. The addition of Ferrostatin-1 (Fer-1), an inhibitor of iron-dependent cell death, did not reverse the DNA damage induced by cisplatin, suggesting that cisplatin’s cytotoxic effects are independent of ferroptosis. HT significantly promoted apoptosis in SW872 cells. After HT treatment at 41°C for 0.5 hours, the apoptotic and cell death rates were 51.8% and 41.6%, respectively. Similarly, at 43°C for 0.5 hours, the rates were 47.9% and 45.7%, respectively. These findings indicate that HT effectively induces apoptosis in RPLS cells.
Morphological observations revealed that untreated SW872 cells grew well under normal culture conditions. After HT treatment, most cells were lysed and died. Cisplatin treatment caused cell shrinkage and apoptosis. Notably, HT disrupted the clustering of tumor cells, making them more susceptible to destruction. The combination of cisplatin and HT resulted in more pronounced morphological changes, with increased cell shrinkage and apoptosis compared to either treatment alone.
The inhibition rate of cell proliferation was 0% in the control group and 50% in the cisplatin-treated group. HT alone increased the inhibition rate to 67.76%, while the combination of cisplatin and HT at 41°C for 0.5 hours raised the inhibition rate to 85.36%. At 43°C for 0.5 hours, the inhibition rate reached 86.64% with HT alone and 87.66% with the combination therapy. These results suggest that HT enhances the cytotoxicity of cisplatin, with the combination therapy being more effective than either treatment alone. However, increasing the temperature to 43°C did not further improve the synergistic effect, indicating that 41°C may be the optimal temperature for HT in combination with cisplatin.
Molecular analysis revealed that HT downregulated the expression of zonula occludens-1 (ZO-1), a tight junction protein that regulates ion transport and cell adhesion. Reduced ZO-1 expression suggests that HT decreases cell adhesion, thereby inhibiting the aggregation of SW872 cells. Additionally, HT upregulated the expression of GPX4 and TNF-α over time. GPX4 protects cells against oxidative stress and lipid peroxidation, and its upregulation is essential for cell survival. TNF-α, a cytokine involved in immune response and cell transformation, was also upregulated, indicating that HT may enhance the immune response against tumor cells.
In conclusion, this study demonstrates that both cisplatin and HT can induce apoptosis and inhibit the proliferation of RPLS SW872 cells. HT enhances the cytotoxic effects of cisplatin, with the combination therapy being more effective than either treatment alone. The optimal temperature for HT in combination with cisplatin appears to be 41°C, as increasing the temperature to 43°C did not further improve outcomes. HT exerts its effects by downregulating ZO-1, which reduces cell adhesion, and upregulating GPX4 and TNF-α, which may enhance cell survival and immune response. These findings provide valuable insights into the potential use of cisplatin and HT as a combined therapeutic strategy for RPLS.
Further research is needed to elucidate the precise molecular mechanisms underlying the effects of cisplatin and HT on RPLS cells. Additionally, in vivo studies and clinical trials are necessary to validate these findings and explore the potential of this combination therapy in improving outcomes for patients with RPLS.
doi.org/10.1097/CM9.0000000000001326
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