LAPTM4B facilitates tumor growth and induces autophagy in hepatocellular carcinoma

Background: Hepatocellular carcinoma (HCC) is one of the most frequent cancers and the third leading cause of cancer-related deaths. It has been reported that lysosomal associated transmembrane protein LAPTM4B expression is significantly upregulated in human cancers and closely associated with tumor initiation and progression. Purpose: We aimed to reveal the relevance of LAPTM4B and the pathogenesis of HCC. Methods: Cell viability assessment, colony formation assay, in vivo xenograrft model, microarray, real-time PCR, immunofluorescence and western blot analysis were applied. Results: Our results demonstrated that LAPTM4B promoted HCC cell proliferation in vitro and tumorigenesis in vivo. Additionally, upon starvation conditions, LAPTM4B facilitated cell survival, inhibited apoptosis and induced autophagic flux. Expression profiling coupled with gene ontology (GO) analysis revealed that 159 gene downregulated by LAPTM4B silencing was significantly enriched in response to nutrient and some metabolic processes. Moreover, LAPTM4B activated ATG3 transcription to modulate HCC cell apoptosis and autophagy. Conclusion: Our findings demonstrate that LAPTM4B acts as an oncogene that promotes HCC tumorigenesis and autophagy, and indicate that LAPTM4B may be used as a novel therapeutic target for HCC treatment.