RASSF3 downregulation increases malignant phenotypes of non-small cell lung cancer.
BACKGROUND
Ras-Association Family1A (RASSF1A) is a well-established tumor suppressor. Ten RASSF homologues comprise this family, and each member is considered a tumor suppressor. RASSF3 is one of the RASSF family members, but its function has not yet been clarified. Recently, we found that RASSF3 interacts with MDM2 and facilitates its ubiquitination, which induces apoptosis through p53 stabilization. However, the role of RASSF3 in human malignancies remains largely unknown.


METHODS
Ninety-five non-small cell lung cancer (NSCLC) patients from Nagoya University Hospital and 45 NSCLC patients from Aichi Cancer Center Hospital underwent pulmonary resection at each hospital, and lung cancer and corresponding non-cancerous lung tissues were collected. The expression levels of RASSF3 were analyzed using quantitative real-time reverse transcription PCR. We performed statistical analysis to investigate the correlation with RASSF3 expression and the clinicopathological characteristics. We also transfected RASSF3-siRNA into NSCLC cells, and performed motility assays to evaluate the influence on migration ability.


RESULTS
RASSF3 expression levels were downregulated in 125 of a total 140 NSCLCs. In a multivariate logistic regression analysis, the low RASSF3 expression group below the median value was independently correlated with progressive phenotypes (lymph node metastasis and pleural invasion), non-adenocarcinoma histology and wild-type epidermal growth factor receptor (EGFR) status. In motility assays, RASSF3-knockdown NSCLC cells increased the migration rate compared to the control cells.


CONCLUSIONS
We found that the expression levels of RASSF3 were frequently downregulated in NSCLCs. Downregulation of RASSF3 strongly correlated with the progressive phenotypes of NSCLCs and EGFR wild-type status. In vitro studies also suggested that RASSF3 downregulation increases migration ability of lung cancer cells. Together, our findings indicate RASSF3 is a candidate tumor suppressor gene of NSCLCs.
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Department of Respiratory Medicine, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan.
Asuki
A
Fukatsu
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Department of General Thoracic Surgery, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan.
Futoshi
F
Ishiguro
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Department of Respiratory Medicine, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan.
Ichidai
I
Tanaka
Department of Medical Biochemistry, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan; Department of Neurosurgery, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Takumi
T
Kudo
Department of Medical Biochemistry, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Kentaro
K
Nakagawa
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Division of Oncological Pathology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan.
Keiko
K
Shinjo
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Division of Epigenomics, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan.
Yutaka
Y
Kondo
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan.
Makiko
M
Fujii
Department of Respiratory Medicine, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan.
Yoshinori
Y
Hasegawa
Department of Thoracic Surgery, Aichi Cancer Center Hospital, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan.
Kenji
K
Tomizawa
Department of Thoracic Surgery, Aichi Cancer Center Hospital, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan.
Tetsuya
T
Mitsudomi
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Department of Cancer Genetics, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan.
Hirotaka
H
Osada
Department of Medical Biochemistry, Graduate School of Medicine, Tokyo Medical and Dental University, Tokyo 113-8519, Japan.
Yutaka
Y
Hata
Division of Molecular Oncology, Aichi Cancer Center Research Institute, 1-1 Kanokoden, Chikusa-ku, Nagoya 464-8681, Japan; Department of Cancer Genetics, Graduate School of Medicine, Nagoya University, Nagoya 466-8550, Japan. Electronic address: ysekido@aichi-cc.jp.
Yoshitaka
Y
Sekido
D017209:Apoptosis; D063646:Carcinogenesis; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis* / Q000473:pathology; D002465:Cell Movement / Q000235:genetics; D002478:Cells, Cultured; D015536:Down-Regulation; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000473:pathology; D008207:Lymphatic Metastasis; D008297:Male; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D009367:Neoplasm Staging; D010641:Phenotype; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
C454041:RASSF3 protein, human; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D051736:Proto-Oncogene Proteins c-mdm2; C512478:EGFR protein, human; D066246:ErbB Receptors; D020559:Monomeric GTP-Binding Proteins
EGFR; Lymph node metastasis; Non-small cell lung cancer; Pleural invasion; RASSF3; Tumor suppressor