GLI-mediated Keratin 17 expression promotes tumor cell growth through the anti-apoptotic function in oral squamous cell carcinomas.
OBJECTIVE
Keratin 17 (KRT17) has been suggested as a potential diagnostic marker of squamous cell carcinoma including oral squamous cell carcinoma (OSCC). The current study was conducted to clarify the function of KRT17 and its expression mechanism in OSCC.


METHODS
Immunohistochemical analyses were carried out to examine the expression of KRT17, GLI family zinc finger (GLI)-1, GLI-2, or cleaved caspase-3 in OSCCs. The expression of KRT17, GLI-1, or GLI-2 was investigated among OSCC cell lines, and the effects of loss-of-function of KRT17 or GLI, using siRNA or inhibitor, on the cell growth of the OSCC cell line HSC-2 particularly with respect to apoptosis were examined.


RESULTS
Immunohistochemical analyses of tissue specimens obtained from 78 OSCC patients revealed that KRT17 was not observed in non-tumor regions but was strongly expressed at high frequencies in tumor regions. Knockdown of KRT17 increased the number of cleaved caspase-3-positive cells, leading to the reduction of cell number. Loss-of-function of GLI-1 or GLI-2 also increased the cell numbers of apoptotic cells positive for staining of Annexin-V and propidium iodide (PI) and the terminal deoxynucleotidyl transferase dUTP-biotin nick-end labeling (TUNEL) method, and induced DNA fragmentation. This inhibitory effect on cell growth was partially rescued by exogenous KRT17 expression. In the KRT17-positive regions in OSCCs, GLI-1 or GLI-2 was frequently detected, and the number of cells with cleaved caspase-3 positive was decreased.


CONCLUSIONS
KRT17 promotes tumor cell growth, at least partially, through its anti-apoptotic effect as a result of the KRT17 overexpression by GLIs in OSCC.
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.|Section of Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Yurie
Y
Mikami
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Shinsuke
S
Fujii
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Kengo
K
Nagata
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Hiroko
H
Wada
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Kana
K
Hasegawa
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.|Section of Oral and Maxillofacial Surgery, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Misaki
M
Abe
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.|Department of Periodontology, Division of Oral Rehabilitation, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Reiko U
RU
Yoshimoto
Section of Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Shintaro
S
Kawano
Section of Maxillofacial Oncology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
Seiji
S
Nakamura
Laboratory of Oral Pathology, Division of Maxillofacial Diagnostic and Surgical Sciences, Faculty of Dental Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. kiyo@dent.kyushu-u.ac.jp.
Tamotsu
http://orcid.org/0000-0002-5219-2652
T
Kiyoshima
D017209:Apoptosis / Q000235:genetics; D014408:Biomarkers, Tumor / Q000235:genetics*; D002294:Carcinoma, Squamous Cell / Q000235:genetics* / Q000473:pathology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D053537:Keratin-17 / Q000096:biosynthesis / Q000235:genetics*; D009061:Mouth Mucosa / Q000473:pathology; D009062:Mouth Neoplasms / Q000235:genetics* / Q000473:pathology; D000071676:Zinc Finger Protein GLI1 / Q000096:biosynthesis* / Q000235:genetics
D014408:Biomarkers, Tumor; C400551:GLI1 protein, human; D053537:Keratin-17; D000071676:Zinc Finger Protein GLI1
Apoptosis; GLI; Keratin 17; Oral squamous cell carcinoma; Tumor cell growth