Head and neck squamous cell carcinoma (HNSCC) is a primary malignant tumor. As the seventh most common cancer worldwide, the number of newly diagnosed cases is expected to exceed 870000 in 2020 and continues to rise. The treatment methods for HNSCC include surgery, radiotherapy (RT), chemotherapy (CRT), etc. The prognosis of HNSCC is poor, with over half of advanced patients experiencing local recurrence or metastasis.

 

The long-term survival rate of patients is low, partly due to the drug resistance of cancer cells. In various tumors, including HNSCC, inhibitors of apoptosis proteins (lAPs) are often overexpressed, leading to cancer cell apoptosis evasion and dysregulation of the apoptosis pathway, resulting in cancer recurrence or metastasis in patients.

 

 

The IAP activity of cancer cells can be inhibited by antagonistic proteins, such as the endogenous antagonist SMAC (the Second mitochondria derived activator of caspase), which binds to the repeat domain of IAP, activates downstream caspase, and promotes apoptosis signaling. In the past 20 years, SMAC mimetics have become potential targeted drugs for the treatment of HNSCC. The SMAC mimetic Xevinapant is a novel and potent small molecule IAP antagonist, which is believed to enhance the effectiveness of anti-cancer therapy, restore the sensitivity of cancer cells to apoptosis, and increase cancer cell apoptosis. However, the role of Xevinapant is currently not fully understood, and most preclinical data is focused on the combination of Xevinapan and chemotherapy, with little data on the combination of Xevinapat and radiotherapy, especially in vitro studies of HNSCC, where relevant research data is particularly scarce.

 

Julia Fleischmann and others from the University of Erlangen Nuremberg in Germany conducted a study on this, and the related results were published in the journal Cells on June 17, 2023, titled "The Effect of Xeninatant Combined with Lonizing Radiation on HNSCC and Normal Tissue Cells and the Impact of Xeninatant on lts Targeted Proteins clAP1 and XIAP.".

 

In this study, the ZenCELL owI live cell dynamic imaging and analysis system from InnoME in Germany was used to monitor 9 cell lines (7 HNSCC cell lines: Cal33) CLS-354、Detroit 562、HSC4、RPMI-2650、UD-SSC-2、UM-SSC-47, The dynamic changes of healthy tissue cell lines (01-GI-SBL, SBLF9) under single or combined treatment with Xevinapan and ionizing radiation (IR) were analyzed, and corresponding images, growth curves, and other data were obtained. Based on this, the important indicator of "doubling time" was calculated and evaluated.

 

 

The author first studied the growth status of cells treated with different concentrations of Xevinapan and plotted growth curves (Figures A and B). Three concentrations of low (8.4uM), medium (13.3 μ M), and high (16.7 μ M) were selected for in-depth study. The results showed that there were significant differences and trends in the effects of low, medium, and high concentrations of drugs on cancer cells.

 

The doubling time of all cell lines treated with Xevinapant alone at three concentrations and in combination with IR showed the same trend as shown in Figure C. In almost all cell lines, low concentrations of Xevinapant have a significant inhibitory effect on cell growth, whether acting alone or in combination with IR. Compared with the control group treated with untreated or IR alone, the doubling time is increased, and Xevinapant shows a significant synergistic inhibitory effect with IR.

 

For the healthy tissue cell line SBLF9, Xevinapant has the weakest effect and there is no significant increase in doubling time. When the concentration of Xevinapant increased to 16.7 μ M, the doubling time of all cell lines except SBLF9 showed negative values (negative values in Figure C indicate the time required for cells to decrease to half of their current number), indicating that at this concentration, Xevinapant's strong cytotoxicity inhibited cell growth, leading to a decrease in cell numbers. This effect began almost immediately after administration of Xevinapant and persisted throughout the entire monitoring process of zenCellowI (Figure D). 13.3uM of Xevinapant also showed similar effects on almost all cell lines, with strong inhibition of cell growth and negative doubling time. However, compared to high concentration drugs, the production of cytotoxicity was not strong or rapid.

 

The results of this study indicate that the IAP inhibitor Xevinapant can inactivate all HNSCC tumor cells at high concentrations and has a minimal impact on normal tissue cells, especially when combined with IR, it exhibits a significant synergistic inhibitory effect on tumor cells, indicating that Xevinapant may be an effective drug for HNSCC combination therapy.