Open AccessSuppression of autophagy by CUB domain‐containing protein 1 signaling is essential for anchorage‐independent survival of lung cancer cells
Author(s) -
Uekita Takamasa,
Fujii Satoko,
Miyazawa Yuri,
Hashiguchi Akinori,
Abe Hitosi,
Sakamoto Michiie,
Sakai Ryuichi
Publication year - 2013
Publication title -
cancer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.035
H-Index - 141
eISSN - 1349-7006
pISSN - 1347-9032
DOI - 10.1111/cas.12154
Subject(s) - anoikis , fyn , microbiology and biotechnology , autophagy , cancer cell , programmed cell death , small interfering rna , protein kinase a , rottlerin , biology , kinase , chemistry , proto oncogene tyrosine protein kinase src , cancer research , apoptosis , cell culture , cancer , transfection , biochemistry , genetics
CUB (C1r/C1s, urchin embryonic growth factor, BMP 1) domain‐containing protein 1 ( CDCP 1) has been implicated in promoting metastasis of cancer cells through several mechanisms, including the inhibition of anoikis, which is cell death triggered by the loss of extracellular matrix interactions. However, the mechanism inhibiting cell death regulated by CDCP 1 remains elusive. Inhibition of CDCP 1 expression using small interfering RNA (si RNA ) induced the cell death of suspended cancer cells without cleaving caspase‐3, a marker of apoptosis; cell death was not inhibited by a general caspase inhibitor, suggesting that the loss of CDCP 1 induces caspase‐independent cell death. In contrast, knockdown of CDCP 1 as well as protein kinase Cδ ( PKC δ), a downstream effector of CDCP 1, in a suspension culture of lung cancer cells resulted in marked induction of membranous microtubule‐associated protein 1 light chain 3 ( LC 3)‐ II protein, a hallmark of autophagy, and caused the formation of an autophagosome structure visualized using green fluorescent protein‐tagged LC 3‐ II . Expression and phosphorylation of exogenous CDCP 1 by Fyn kinase reduced the formation of autophagosomes and inhibited phosphorylation of CDCP 1 by PP 2, a Src kinase inhibitor or inhibited PKC δ by rottlerin, stimulating autophagosome formation. Moreover, death of suspended lung cancer cells induced by CDCP 1 si RNA or by PKC δ si RNA was reduced by the autophagy inhibitor 3‐methyladenine. These results indicate that CDCP 1‐ PKC δ signaling plays a critical role in inhibiting autophagy, which is responsible for anoikis resistance of lung cancer cells.