Upregulation of SOX9 in lung adenocarcinoma and its involvement in the regulation of cell growth and tumorigenicity.
OBJECTIVE
SOX9 is an important transcription factor required for development and has been implicated in several types of cancer. However, SOX9 has never been linked to lung cancer to date. Here, we show that SOX9 expression is upregulated in lung adenocarcinoma and show how it is associated with cancer cell growth.


METHODS
Data mining with five microarray data sets containing 490 clinical samples, quantitative reverse transcription-PCR validation assay in 57 independent samples, and immunohistochemistry assay with tissue microarrays containing 170 lung tissue cores were used to profile SOX9 mRNA and protein expression. Short interference RNA suppression of SOX9 in cell lines was used to scrutinize functional role(s) of SOX9 and associated molecular mechanisms.


RESULTS
SOX9 mRNA and protein were consistently overexpressed in the majority of lung adenocarcinoma. Knockdown of SOX9 in lung adenocarcinoma cell lines resulted in marked decrease of adhesive and anchorage-independent growth in concordance with the upregulation of p21 (CDKN1A) and downregulation of CDK4. In agreement with higher SOX9 expression level in lung adenocarcinoma, the p21 mRNA level was significantly lower in tumors than that in normal tissues, whereas the opposite was true for CDK4, supporting the notion that SOX9 negatively and positively regulated p21 and CDK4, respectively. Finally, whereas SOX9-knockdown cells showed significantly attenuated tumorigenicity in mice, SOX9 transfectants consistently showed markedly stronger tumorigenicity.


CONCLUSIONS
Our data suggest that SOX9 is a new hallmark of lung adenocarcinoma, in which SOX9 might contribute to gain of tumor growth potential, possibly acting through affecting the expression of cell cycle regulators p21 and CDK4.
Jiang
Shih Sheng
SS
National Institute of Cancer Research, Taiwan.
Fang
Wen-Tsen
WT
Hou
Ya-Hsiue
YH
Huang
Shiu-Feng
SF
Yen
B Linju
BL
Chang
Junn-Liang
JL
Li
Shih-Miao
SM
Liu
Hui-Ping
HP
Liu
Ying-Lan
YL
Huang
Chih-Ting
CT
Li
Yu-Wei
YW
Jang
Te-Hsuan
TH
Chan
Shih-Hsuan
SH
Yang
Su Jing
SJ
Hsiung
Chao A
CA
Wu
Cheng-Wen
CW
Wang
Lu-Hai
LH
Chang
I-Shou
IS
D000230:Adenocarcinoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D015153:Blotting, Western; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D051358:Cyclin-Dependent Kinase 4 / Q000235:genetics / Q000378:metabolism; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D015536:Down-Regulation; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D051379:Mice; D016513:Mice, SCID; D020411:Oligonucleotide Array Sequence Analysis; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055758:SOX9 Transcription Factor / Q000235:genetics* / Q000378:metabolism; D014183:Transplantation, Heterologous; D047368:Tumor Burden; D015854:Up-Regulation
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D055758:SOX9 Transcription Factor; C527932:SOX9 protein, human; D051358:Cyclin-Dependent Kinase 4