Targeting Autophagy With the Synergistic Combination of Chloroquine and Rapamycin as a Novel Effective Treatment for Well-differentiated Liposarcoma

Abstract

Background/aim: Liposarcoma is a type of soft-tissue sarcoma arising from fat tissue. It is relatively common among soft-tissue sarcomas. Chloroquine (CQ), an antimalarial drug, can inhibit autophagy and induce apoptosis in cancer cells. Rapamycin (RAPA) is an inhibitor of mTOR. The combination of RAPA and CQ is a strong inhibitor of autophagy. Previously, we showed that the combination of RAPA and CQ was effective against a de-differentiated liposarcoma patient-derived orthotopic xenograft (PDOX) mouse model. In the present study, we investigated the mechanism of efficacy of the combination of RAPA and CQ to target autophagy in a well-differentiated liposarcoma (WDLS) cell line in vitro.

Materials and methods: The human WDLS cell line 93T449 was used. The WST-8 assay was used to test the cytotoxicity of RAPA and CQ. Western blotting was used to detect microtubule-associated protein light chain 3-II (LC3-II) which is a component of autophagosomes. Immunostaining of LC3-II was also performed for autophagosome analysis. Τhe TUNEL assay was used to detect apoptotic cells, and apoptosis-positive cells were counted in three randomly selected microscopic fields for statistical validation.

Results: RAPA alone and CQ alone inhibited the viability of 93T449 cells. The combination of RAPA and CQ inhibited 93T449 cell viability significantly more than either drug alone and increased the number of autophagosomes which led to extensive apoptosis.

Conclusion: The combination of RAPA and CQ increased the number of autophagosomes which led to apoptosis in 93T449 WDLS cells, suggesting novel effective treatment for this recalcitrant cancer by targeting autophagy.

Keywords: LC-3; Well-dedifferentiated liposarcoma; apoptosis; autophagosome; autophagy; chloroquine; rapamycin.