Loss of MAL expression in precancerous lesions of the esophagus.
BACKGROUND
We have identified a novel function of MAL (T-cell differentiation-related gene) as a candidate suppressor gene in esophageal cancer. As the role of MAL expression in esophageal carcinogenesis is as yet undetermined, MAL expression in a rat multi-step carcinogenic model and in precancerous lesions of the human esophagus was investigated. Microarray analysis between MAL-transfectant and control cells was also carried out to clarify how MAL confers its anti-tumor effects.


METHODS
(1) In the rat model, MAL expression levels in laser microdissected normal esophageal epithelium, dysplastic tissues and carcinoma tissues were examined by reverse transcription (RT)-PCR. (2) Immunostaining with MAL antibody was performed in 10 dysplastic lesions adjacent to cancer in six cases of esophageal cancer. (3) We established a MAL transfectant using a Tet-off vector in esophageal cancer cells and performed microarray analysis under MAL-positive and MAL-negative conditions.


RESULTS
(1) In the rat model, MAL mRNA expression was observed only in the normal samples. (2) MAL expression was observed distinctively in differentiated or keratinized normal tissues and was not observed in either dysplastic lesions or carcinoma tissue. (3) Up-regulated genes in MAL-positive cells included keratin 18 (transfectant/control = 2.94) and keratin 10 (t/c = 2.82).


CONCLUSIONS
MAL expression was lost in dysplastic lesions of the rat carcinoma model as well as the human esophagus. The up-regulated keratins revealed by microarray analysis and the strong staining of the differentiated normal tissues in immunohistochemical study support the role of MAL as a regulator of differentiation in esophageal epithelium.
Mimori
Koshi
K
Department of Surgical Oncology, Medical Institute of Bioregulation, Kyushu University, 4546 Tsurumihara, Beppu, 874-0838, Japan. mmori@beppu.kyushu-u.ac.jp
Nishida
Kohjiro
K
Nakamura
Yoshito
Y
Ieta
Keisuke
K
Yoshikawa
Yasuji
Y
Sasaki
Atsushi
A
Ishii
Hideshi
H
Alonso
Miguel A
MA
Mori
Masaki
M
D000818:Animals; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D004848:Epithelium / Q000378:metabolism / Q000473:pathology; D004938:Esophageal Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004947:Esophagus / Q000378:metabolism / Q000473:pathology*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D009185:Myelin Proteins / Q000235:genetics / Q000378:metabolism*; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D020411:Oligonucleotide Array Sequence Analysis; D010212:Papilloma / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D011230:Precancerous Conditions / Q000378:metabolism* / Q000473:pathology; D011510:Proteolipids / Q000235:genetics / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014407:Tumor Cells, Cultured
C569026:MAL protein, human; C569028:Mal protein, rat; D026901:Membrane Transport Proteins; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D011510:Proteolipids; D012334:RNA, Neoplasm