Chloroquine Combined With Rapamycin Arrests Tumor Growth in a Patient-derived Orthotopic Xenograft (PDOX) Mouse Model of Dedifferentiated Liposarcoma

Background/Aim: Dedifferentiated liposarcoma (DDLS) is a type of soft-tissue sarcoma with a poor prognosis due to distant metastasis and resistance to chemotherapy. The antimalarial drug chloroquine (CQ) can induce apoptosis in cancer cells. CQ in combination with rapamycin (RAPA), an mTOR inhibitor, has shown efficacy on osteosarcoma and other types of cancer. In the present study the efficacy of RAPA combined with CQ on the treatment of a DDLS patient-derived orthotopic xenograft (PDOX) model was investigated. Materials and Methods: A patient-derived DDLS was transplanted into the left retroperitoneum of nude mice to establish a DDLS PDOX nude-mouse model. The mice were randomly divided as follows: untreated control group; CQ group; RAPA group; combined CQ and RAPA group (n=7 for all groups). During the treatment period, tumor volume was measured every 3-4 days with calipers. After 2 weeks treatment, the mice were sacrificed, and H&E staining was performed for histological evaluation. The TUNEL assay was performed to detect apoptosis. Results: The combination of CQ and RAPA arrested tumor growth in the DDLS PDOX compared to the untreated control (p=0.009) and was significantly more effective than RAPA alone (p=0.009). RAPA alone slowed tumor growth, but the difference was not statistically significant (p>0.05). CQ was not active alone (p>0.05). The number of apoptotic TUNEL-positive cells was significantly higher in the CQ plus RAPA group than in the other groups (p=0.02). Conclusion: Combination therapy with CQ and RAPA arrested tumor growth in a DDLS PDOX model by inducing apoptosis.