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FEBS Open Bio. 2013 May 10;3:225-30. doi: 10.1016/j.fob.2013.04.005. Print 2013.

Calretinin mediates apoptosis in small cell lung cancer cells expressing tetraspanin CD9.

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Department of Respiratory Medicine, Allergy and Rheumatic Diseases, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan ; Department of Respiratory Medicine, The Second Affiliated Hospital, School of Medicine, Xi'an Jiaotong University, Xi'an 71004, China.


A majority of small cell lung cancer (SCLC) cells lack a metastasis suppressor, tetraspanin CD9, and CD9 expression promotes their apoptosis. By a proteomics-based approach, we compared an SCLC cell line with its CD9 transfectant and found that a calcium-binding neuronal protein, calretinin, is upregulated in CD9-positive SCLC cells. Ectopic or anticancer drug-induced CD9 expression upregulated calretinin, whereas CD9 knockdown down-regulated calretinin in SCLC cells. When calretinin was knocked down, CD9-positive SCLC cells revealed increased Akt phosphorylation and decreased apoptosis. These results suggest that CD9 positively regulates the expression of calretinin that mediates proapoptotic effect in SCLC cells.


Apoptosis; CD9; Calretinin; KO, knockout; MALDI-TOF, matrix-assisted laser desorption/ionization time-of-flight; NSCLC, nonsmall cell lung cancer; PARP, poly(ADP-ribose)polymerase; PMF, peptide mass fingerprinting; Proteomics; RT-PCR, reverse transcription-PCR; SCLC, small cell lung cancer; Small cell lung cancer; Tetraspanin

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