ER‑α36 knockdown is associated with lysosomal dysfunction and proliferation inhibition in liver cancer cells

Estrogen receptor (ER)‑α36 and autophagy have each independently been reported to promote the proliferation of liver cancer cells; however, the association between them has not been explored. Therefore, the present study aimed to investigate the role and the underlying mechanism of ER‑α36 in the regulation of autophagy in liver cancer cells. The proliferation of liver cancer cell variants was examined by colony formation assay. A xenograft tumor model in nude mice was used to examine the role of ER‑α36 in malignant proliferation of liver cancer cells in vivo. Autophagic flux and lysosomal localization were assessed with immunofluorescence and confocal microscopy. The levels of ER‑α36, LAMP1, AKT, p62 and LC3‑Ⅱ/Ⅰ in liver cancer cell variants, and tumors formed by HepG2 cell variants in the nude mice were examined using Western blot and immunohistochemistry. The results revealed that ER‑α36 knockdown impaired autophagic flux by increasing lysosomal membrane permeabilization (LMP) and blocking lysosomal degradation. ER‑α36 knockdown also significantly inhibited the proliferation of liver cancer cells and orthotopic liver xenograft tumors. In addition, decreased AKT phosphorylation and the juxtanuclear clustering of lysosomes were observed in the liver cancer cells with ER‑α36 knockdown. In vitro experiments using the AKT inhibitor MK‑2206 indicated that AKT is involved in the ER‑α36 knockdown‑induced changes in LMP and lysosomal localization in liver cancer cells. In summary, the present study revealed that ER‑α36 plays a role in regulating the autophagy and proliferation of liver cancer cells, which is associated with the modulation of AKT signaling, LMP and lysosome localization. These findings highlight an important role of ER‑α36 in liver tumorigenesis.