Luciferase Reporter Cell Line - RKO

Anti-angiogenic therapy is an important treatment strategy for metastatic colorectal cancer (mCRC). Here, researchers conducted a clinical study of low-dose apatinib monotherapy as third-line treatment for mCRC and evaluated its efficacy and safety. Results showed that low-dose apatinib provided survival benefits comparable to conventional treatment, significantly improved patients' quality of life, and had tolerable adverse reactions. To further explore the mechanism of action of apatinib in CRC besides angiogenesis, researchers performed RNA sequencing, which suggested that apatinib may exert other potential anti-tumor effects through multiple pathways, including exosome secretion. In RKO and HCT116 cells, apatinib significantly reduced exosome secretion by targeting multivesicular body (MVB) transport. Further research showed that apatinib not only promotes MVB degradation by regulating LAMP2 but also interferes with MVB transport by inhibiting Rab11 expression. Furthermore, apatinib inhibits MVB membrane fusion by reducing the expression of SNAP23 and VAMP2. In vivo experiments showed that apatinib inhibited the growth and metastasis of orthotopic colon cancer in mice and reduced the number of serum exosomes.

To investigate the therapeutic effect of apatinib, researchers established an orthotopic mouse colon cancer model. A certain amount of RKO-luc cell suspension at a concentration of 2.5 × 10⁶/mL was subcutaneously injected into the right back of BALB/c nude mice. When the subcutaneous tumor tissue was visible to the naked eye, it was dissected and embedded in the mesentery of the BALB/c nude mice. The mice were divided into two groups: a control group and an apatinib group. In vivo bioluminescence imaging was used to detect tumors in the colon and other organs of the mice. As shown in Figure 1A, the fluorescence intensity, tumor volume, and tumor weight of the control group increased (Figure 1B), respectively (Figure 1C). Meanwhile, the fluorescence intensity of primary tumors and metastatic tumors (including liver, lymph node, and peritoneal metastases) in the apatinib treatment group was significantly reduced (Figure 1D). Furthermore, the serum exosome concentration (Figure 1E) and total exosome protein concentration (Figure 1F) of the control group mice were significantly higher than those of the apatinib treatment group mice, indicating that apatinib inhibited exosome secretion.

Figure 1. The antitumor efficacy of apatinib and exerted exosome inhibition in vivo. (Zhao L, et al., 2022)