## 4 Discussion
An anticancer drug should have low cytotoxicity to normal cells and should selectively exhibit cytotoxicity to malignant tumor cells [42]. In this experiment, the IC\({}_{50}\) values of sasam-Kyeongokgo and gefitinib for NCI-H520 cells were calculated as 17.21 \(\pm\) 7.28 mg/mL and 4.56 \(\pm\) 1.46 \(\upmu\)M (2.00 \(\pm\) 0.64 \(\upmu\)g/mL), respectively. Thus, both drugs exhibited relatively low cytotoxicity to the cells. In general, gefitinib is known to have an IC\({}_{50}\) of approximately 0.1 \(\upmu\)M for sensitive EGFR-expressing tumor cell lines. The NCI-H520 cells used in this experiment also exhibited resistance to gefitinib, similar to the finding of a previous report [41]. Nude mice are typical athymic animals and are the most commonly used experimental animals for the development of anticancer drugs, since they can receive transplants of allogeneic tumor cells as well as human-derived tumor cells [43]. In a tumor-transplanted nude mouse model, the anticancer effect is mainly characterized by the growth inhibition of the transplanted mass [44; 45]. The results of this experiment confirmed that the sasam-Kyeongokgo and gefitinib combination administration groups showed significantly superior reductions in the tumor volume and tumor weight in comparison with the gefitinib alone group. In the cytotoxicity test for the NCI-H520 cells, sasam-Kyeongokgo showed relatively low cytotoxicity, but increases in the number of apoptotic cells in the tumor mass and immune activity were confirmed through various test results. On the basis of these findings, the synergistic anticancer effect of the combination of gefitinib and sasam-Kyeongokgo is considered to be due to immune activity rather than direct cytotoxicity to tumor cells. Significant immunosuppression is known to be induced after tumor transplantation, and this immunosuppression is mainly related to the T lymphocytes [46]. Various studies have been conducted to identify measures that can be implemented to strengthen the body's defense against tumors by stimulating an individual's immune cells and inducing cytokine production. The development of anticancer drugs through immune activation has attracted attention in this regard [47; 48]. Moreover, antioxidants are known to exhibit effective anticancer effects in relation to immune activity [49; 50]. This experiment also showed significant immunosuppression caused by NCI-H520 tumor cell transplantation. Along with a decrease in the weight of the immune organs, significant atrophy was confirmed due to the decrease in the number of lymphocytes in the spleen and lymph nodes. In contrast, gefitinib alone had no significant effect on tumor-transplant-related immunosuppression. On the other hand, significant immunological activity was confirmed in the group administered sasam-Kyeongokgo alone and those that received the three doses of the sasam-Kyeongokgo and gefitinib combination. In particular, a significant immunoactive effect was confirmed in comparison with the gefitinib-alone group, and it was in good agreement with these immunoactive effects. A decrease in the tumor weight and volume and an increase in apoptosis were confirmed. Therefore, it is considered that the increase in the anticancer effect of gefitinib by the combined administration of sasam-Kyeongokgo is related to immune activity. TNF-\(\alpha\) is a representative type of cytokine produced in various cell types, including splenocytes, and is known to play an important role in the differentiation of T lymphocytes [51]. TNF-\(\alpha\) generally activates cellular immunity and increases the function of IL-2, which promotes antibody production [52]. IL-1 is another type of cytokine secreted by various cells, such as lymphocytes, dendritic cells, macrophages, endothelial cells, fibroblasts, and keratinocytes. There are two types of IL-1, namely IL-1\(\beta\), secreted by cells, and IL-1\(\alpha\), which is a membrane-attached type. They play important roles in the immune response [53].