As shown in Figure 4, PFPE caused obvious DNA fragmentation in S180 cells, which is also a typical biochemical feature of apoptosis. The data in this study suggest that the PFPE could induce apoptosis in S180 cells, and the cytotoxic effects were associated with apoptosis, implying that the extract has great potential in anti-cancer drug screening. Mitochondria play a critical role in cell apoptosis triggered by many stimuli. Loss of MMP is an early event in apoptosis. The MMP, as detected by flow cytometry with Rh123, significantly decreased immediately after 24 h PFPE treatment. Electron leakage from the mitochondrial respiratory chain may react with molecular oxygen, resulting in the formation of superoxide, which is subsequently converted to ROS. Moreover, excessive ROS may cause oxidative damage to lipids, proteins, and DNA, leading to cell death. As seen from Figure 6, compared with the control group, the generation of intracellular ROS dramatically increased in S180 cells. These results suggest that the decreased MMP and elevated ROS may both related to cell apoptosis after the PFPE treatment, and the PFPE-induced cell apoptosis might be mitochondria dependent. Consistent with in vitro findings, the in vivo study provides information that the PFPE significantly reduced the S180 sarcoma weight at the indicated dose, showing its specific role in anticancer therapy. In tumor immunotherapy, the occurrence, growth of tumor and immune state has a very important relationship. Spleen and thymus are important immunological organs. The spleen index and thymus index could reflect the immune Adriamycin function of spleen and thymus. According to other reports, CTX caused atrophy of spleen and thymus and influenced the spleen. We got similar results in the in vivo experiment in CTX treated group. However, at low concentration group, PFPE did not induce such changes. As illustrated in our work, PFPE could efficiently inhibit tumor growth and also has lower immune organ toxicity. Via GC–MS analysis, various possible chemical components were detected in PFPE. n-Hexadecanoic acid has antitumor activity to human leukemic cells as well as murine cells. Hexadecanoic acid has been reported to induce NF-kB activation in HaCaT keratinocytes, which is an important pathway involved in cancer development. Moreover, fatty acids exhibit cytotoxicity against HeLa cells and retard tumor growth. The essential oil, with n-Hexadecanoic acid and octadecanoic acid as the main components, showed significant cytotoxicity against oral cancer, breast cancer and small cell lung cancer. Steroidal compounds had a potent inhibition effect against various cancer cells. Therefore, the anti-tumor effect of PFPE both in vitro and vivo may be closely related to the specific efficacy of such components, functioning either alone or together, which needs further confirmation. In conclusion, this work provided evidence that the PFPE inhibits the proliferation of S180 cells in vitro through inducing apoptosis, while the PFPE significantly reduced the weight of S180 sarcoma in vivo. Apoptosis induction has become a new therapeutic target in cancer research, and the results in our paper indicate that the PFPE may have a potential application as a natural anti-tumor agent. Future research should investigate the specific bioactive compounds and then try to explore the molecular mechanisms of the PFPE in cancer therapy. The cyclic nucleotides, cyclic adenosine monophosphate and cyclic guanosine monophosphate are intracellular second messengers with diverse regulatory functions in both unicellular and multicellular organisms. Hence there are an extreme variety and large number of isoforms of these nucleotidyl cyclases.