Up-Regulated Expression of LAMP2 and Autophagy Activity during Neuroendocrine Differentiation of Prostate Cancer LNCaP Cells

Abstract

Neuroendocrine (NE) prostate cancer (PCa) is a highly aggressive subtype of prostate cancer associated with resistance to androgen ablation therapy. In this study, we used LNCaP prostate cancer cells cultured in a serum-free medium for 6 days as a NE model of prostate cancer. Serum deprivation increased the expression of NE markers such as neuron-specific enolase (NSE) and βIII tubulin (βIII tub) and decreased the expression of the androgen receptor protein in LNCaP cells. Using cDNA microarrays, we compared gene expression profiles of NE cells and non-differentiated LNCaP cells. We identified up-regulation of 155 genes, among them LAMP2, a lysosomal membrane protein involved in lysosomal stability and autophagy. We then confirmed up-regulation of LAMP2 in NE cells by qRT-PCR, Western blot and confocal microscopy assays, showing that mRNA up-regulation correlated with increased levels of LAMP2 protein. Subsequently, we determined autophagy activity in NE cells by assessing the protein levels of SQSTM/p62 and LC3 by Western blot and LC3 and Atg5 mRNAs content by qRT-PCR. The decreased levels of SQSTM/p62 was accompanied by an enhanced expression of LC3 and ATG5, suggesting activation of autophagy in NE cells. Blockage of autophagy with 1μM AKT inhibitor IV, or by silencing Beclin 1 and Atg5, prevented NE cell differentiation, as revealed by decreased levels of the NE markers. In addition, AKT inhibitor IV as well as Beclin1 and Atg5 kwockdown attenuated LAMP2 expression in NE cells. On the other hand, LAMP2 knockdown by siRNA led to a marked blockage of autophagy, prevention of NE differentiation and decrease of cell survival. Taken together, these results suggest that LAMP2 overexpression assists NE differentiation of LNCaP cells induced by serum deprivation and facilitates autophagy activity in order to attain the NE phenotype and cell survival. LAMP2 could thus be a potential biomarker and potential target for NE prostate cancer.

Irisin and Autophagy: First Update

“…Ultimately, the autophagolysosomes were formed by the fusion of lysosomes and autophagosomes, also through the involvement of the lysosomal-associated membrane protein 2 (LAMP2). The autophagolysosomes are responsible of degradation of damaged macromolecules and dysfunctional organelles in cells for the recycling; the contents are broken down into constituent macromolecular precursors that can be reused as raw “bio”-material or, alternatively, metabolized (fusion and degradation stage) [ 25 ]. A summary of the molecular events involved in the autophagy process is illustrated in Figure 1 .…”

The lysosomal membrane protein LAMP2A promotes autophagic flux and prevents SNCA-induced Parkinson disease-like symptoms in the Drosophila brain

“…In humans, LAMP2 gene deficiency leads to Danon disease, histologically characterized by an extensive accumulation of autophagic vacuoles in various tissues and defects in autophagosome-lysosome fusion [21,89,90]. A similar apparent block of autophagy could be reproduced in lamp2 knock-out mice, leading to the accumulation of autophagic vacuoles and of SQSTM1-positive aggregates in the brain [91][92][93], or by LAMP2 inactivation in mouse and human cultured cells [88,[94][95][96]. The LAMP2 gene products appear to play a specific role in the fusion of autophagosomes with lysosomes [88,95,97].…”

Lamp2 inhibits epithelial-mesenchymal transition by suppressing Snail expression in HCC

“…The LAMP-2C isoform functions as a receptor for RNA and DNA degradation [ 17 , 18 ]. A recent report demonstrated the upregulation of Lamp2 and increased autophagy activity during neuroendocrine differentiation of prostate cancer LNCAP cells [ 19 ]. However, the impact of Lamp2 on HCC is poorly understood.…”