Phase I study of a chloroquine-gemcitabine combination in patients with metastatic or unresectable pancreatic cancer

CQ sensitizes human pancreatic cancer cells to gemcitabine through the lysosomal apoptotic pathway via reactive oxygen species

As an established anticancer drug, gemcitabine (GEM) is an effective systemic treatment for advanced pancreatic cancer (PC). However, little is known about the potential effectors that may modify tumour cell sensitivity towards GEM. Autophagy, as a physiological cellular mechanism, is involved in both cell survival and cell death. In this study, we found that exposure to GEM induced a significant increase in autophagy in a dose-dependent manner in PANC-1 and BxPC-3 cells. Inhibition of autophagy by chloroquine (CQ) and ATG7 siRNA increased GEM-induced cytotoxicity, and CQ was more effective than ATG7 siRNA. Moreover, CQ significantly enhanced GEM-induced apoptosis, while ATG7 siRNA failed to show the similar effect. Subsequently, we identified a potential mechanism of this cooperative interaction by showing that GEM with CQ pretreatment markedly triggered reactive oxygen species (ROS) boost and then increased lysosomal membrane permeability. Consequently, cathepsins released from lysosome into the cytoplasm induced apoptosis. We showed that CQ could enhance PC cells response to GEM in xenograft models. In conclusion, our data showed that CQ sensitized PC cells to GEM through the lysosomal apoptotic pathway via ROS. Thus, CQ as a potential adjuvant to GEM might represent an attractive therapeutic strategy for PC treatment.

miR-503 suppresses the proliferation and metastasis of esophageal squamous cell carcinoma by triggering autophagy via PKA/mTOR signaling

MicroRNA (miR)-503 is involved in the regulation of the malignant phenotype in multiple tumor types, and has been proven to be a novel diagnostic and therapeutic target; however, its function and mechanisms of action have not yet been fully elucidated in esophageal squamous cell carcinoma (ESCC). In the current study, we detected miR‑503 expression by RT‑qPCR and found that miR‑503 expression was increased in ESCC, but negatively correlated with lymph node metastasis, TNM stage and tumor differentiation. Functionally, we confirmed that miR‑503 inhibited the proliferation and metastasis of ESCC cells by triggering cellular autophagy. Mechanistically, we confirmed that miR‑503 exerted its biological effects by targeting protein kinase CAMP‑activated catalytic subunit alpha (PRKACA) in ESCC by dual luciferase reporter assay. Moreover, miR‑503 was found to trigger autophagy in ESCC cells through the protein kinase A (PKA)/mammalian target of rapamycin (mTOR) pathway. Taken together, our results demonstrate that miR‑503 suppresses the proliferation and metastasis of ESCC via the activation of autophagy, mediated by the PKA/mTOR signaling pathway.