Aberrant expression of connexin 26 is associated with lung metastasis of colorectal cancer.
OBJECTIVE
Connexin 26 (Cx26) is one of the gap junction-forming family members classically considered to be tumor suppressors. However, recent studies show association of elevated expression of Cx26 with poor prognosis in several human malignancies. Furthermore, Cx26 has been observed to be indispensable to spontaneous metastasis of melanoma cells. Here, we assessed Cx26 expression in primary colorectal cancer (CRC) and the metastatic lesions to elucidate its role in metastasis.


METHODS
Cx26 expression was assessed in 25 adenomas, 167 CRCs, and normal mucosa, together with the metastatic lesions.


RESULTS
Normal mucosa and adenomatous tissue expressed Cx26 mainly in the plasma membrane, whereas cancer cells mostly contained Cx26 in the cytoplasm. The incidence of aberrant Cx26 expression varied widely in CRC (mean, 49.5 +/- 35.5%), and the expression levels were confirmed by Western blot and quantitative reverse transcription-PCR. Clinicopathologic survey revealed association of high expression with less differentiated histology and venous invasion (P = 0.0053 and P = 0.0084, respectively). Notably, high Cx26 expression was associated with shorter disease-free survival and shorter lung metastasis-free survival in 154 curatively resected CRC sets (P = 0.041 and P = 0.028, respectively). Survey of metastatic lesions revealed that lung metastasis, but not liver and lymph nodes metastases, expressed higher Cx26 than the CRC series or corresponding primary CRCs (P < 0.0001 and P = 0.0001, respectively).


CONCLUSIONS
These findings suggest that aberrant expression of Cx26 plays an essential role in lung metastasis. Thus, Cx26 is a promising therapeutic target, particularly for CRC patients who develop lung metastasis.
Ezumi
Koji
K
Department of Surgery, Gastroenterological Surgery, Graduate School of Medicine, Osaka University, Yamada-oka, Suita City, Osaka, Japan.
Yamamoto
Hirofumi
H
Murata
Kohei
K
Higashiyama
Masahiko
M
Damdinsuren
Bazarragchaa
B
Nakamura
Yurika
Y
Kyo
Naganori
N
Okami
Jiro
J
Ngan
Chew Yee
CY
Takemasa
Ichiro
I
Ikeda
Masataka
M
Sekimoto
Mitsugu
M
Matsuura
Nariaki
N
Nojima
Hiroshi
H
Monden
Morito
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000235:genetics / Q000473:pathology* / Q000601:surgery; D000072259:Connexin 26; D017630:Connexins / Q000235:genetics*; D017931:DNA Primers; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000473:pathology; D008175:Lung Neoplasms / Q000235:genetics / Q000473:pathology / Q000556:secondary* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D016133:Polymerase Chain Reaction
D017630:Connexins; D017931:DNA Primers; C000607042:GJB2 protein, human; D000072259:Connexin 26