Autophagy is differentially induced in prostate cancer LNCaP, DU145 and PC-3 cells via distinct splicing profiles of ATG5.
Autophagic responses to chemotherapeutic agents may vary greatly among different prostate cancer cells and have not been well characterized. In this study, we showed that valproic acid (VPA) induced conversion of LC3-I to LC3-II and formation of LC3 puncta, the typical markers of autophagy, in LNCaP and PC-3 cells. However, these markers were undetectable in DU145 cells upon autophagic stimulation, indicating a defect of autophagy in this cell line. Among several critical autophagy-related proteins, ATG5 and ATG12-ATG5 conjugates, which are essential for autophagy induction, were absent in DU145 cells. No canonical transcripts for full-length ATG5 but only two alternatively spliced ATG5 transcripts were identified in DU145 cells. These alternative transcripts lack one or two exons, leading to premature termination of ATG5 translation. Transfection of the wild-type ATG5 gene into DU145 cells rescued the production of ATG5 and ATG12-ATG5 conjugates, resulting in formation of LC3-II conjugates and LC3 puncta. Moreover, the levels of the SQSTM1 protein, which should be degradable as an autophagy adaptor, were much higher in DU145 than in LNCaP and PC-3 cells, but were significantly decreased after ATG5 restoration in DU145 cells. However, expression of wild-type ATG5 in DU145 or knockdown of ATG5 in LNCaP and PC-3 cells did not change the inhibitory effects of VPA on these cells. Collectively, these results indicated that VPA-induced autophagy in prostate cancer cells depended on ATG5 and more importantly, that the autophagy pathway was genetically impaired in DU145 cells, suggesting caution in interpreting autophagic responses in this cell line.
Department of Immunobiology, Institute of Tissue Transplantation and Immunology, Jinan University, Guangzhou, China.
Dong-Yun
DY
Ouyang
Li-Hui
LH
Xu
Xian-Hui
XH
He
Yan-Ting
YT
Zhang
Long-Hui
LH
Zeng
Ji-Ye
JY
Cai
Shuai
S
Ren
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D017398:Alternative Splicing / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D000071192:Autophagy-Related Protein 12; D000071187:Autophagy-Related Protein 5; D001483:Base Sequence; D045744:Cell Line, Tumor; D055785:Gene Knockdown Techniques; D006801:Humans; D008297:Male; D008869:Microtubule-Associated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D000071456:Sequestosome-1 Protein; D025841:Small Ubiquitin-Related Modifier Proteins / Q000378:metabolism; D014162:Transfection; D014635:Valproic Acid / Q000494:pharmacology
C466624:ATG12 protein, human; C502778:ATG5 protein, human; D048868:Adaptor Proteins, Signal Transducing; D000071192:Autophagy-Related Protein 12; D000071187:Autophagy-Related Protein 5; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D012334:RNA, Neoplasm; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein; D025841:Small Ubiquitin-Related Modifier Proteins; D014635:Valproic Acid