Silencing fibronectin extra domain A enhances radiosensitivity in nasopharyngeal carcinomas involving an FAK/Akt/JNK pathway.
OBJECTIVE
Fibronectin extra domain A (EDA) is known to play important roles in angiogenesis, lymphangiogenesis, and metastasis in malignant tumors. The present study examined the effect of EDA on the radioresistance potential of nasopharyngeal carcinoma (NPC).


METHODS
EDA expression levels in blood samples and tumor tissues of NPC patients were tested by enzyme-linked immunosorbent assay and immunohistochemistry. Radiosensitivity was tested by colony survival assay. Apoptosis was determined by flow cytometry. The expressions of EDA, cleaved caspase 9, cleaved caspase 3, cleaved PARP, Bcl-2, and the levels of phosphorylated FAK, Akt, and JNK were measured by Western blot. Xenografts were used to confirm the effect of EDA on radiosensitivity in vivo.


RESULTS
EDA levels in blood samples of advanced NPC patients were much higher than those in early-stage patients. In tumor tissues, the positive expressions of EDA in NPC tumor tissues were shown to be correlated with the differentiation degrees of cancer cells and lymph node metastases. Additionally, the expression of EDA is positively correlated with the expression of antiapoptotic gene (Bcl2), but negatively correlated with the expressions of apoptotic genes (cleaved caspase-3, cleaved caspase-9, cleaved PARP). In vitro, EDA-silenced NPC cells CNE-2 shows substantially enhanced radiosensitivity with lower colony survival and more apoptosis in response to radiation. In vivo, EDA-silenced xenografts were more sensitive to radiation. At the molecular level, FAK/Akt/JNK signaling was demonstrated to be inactivated in EDA-silenced CNE-2 cells.


CONCLUSIONS
EDA strongly affected the radiosensitivity of NPC cells. FAK/Akt/JNK signaling was found to be a potential signaling mediating EDA function.
Department of Oncology and Southwest Cancer Center, Southwest Hospital, Third Military Medical University, Chongqing 400038, PR China.
Juanjuan
J
Ou
Feng
F
Pan
Peiliang
P
Geng
Xing
X
Wei
Ganfeng
G
Xie
Jia
J
Deng
Xueli
X
Pang
Houjie
H
Liang
D000818:Animals; D002277:Carcinoma; D053148:Caspase 3 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D005353:Fibronectins / Q000737:chemistry / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism*; D006801:Humans; D016086:Lentivirus / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000532:radiotherapy*; D009363:Neoplasm Proteins / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D011836:Radiation Tolerance / Q000502:physiology*; D014183:Transplantation, Heterologous; D014410:Tumor Stem Cell Assay / Q000379:methods
D005353:Fibronectins; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011065:Poly(ADP-ribose) Polymerases; D051417:Focal Adhesion Kinase 1; C496050:PTK2 protein, human; D051057:Proto-Oncogene Proteins c-akt; D053148:Caspase 3; D053453:Caspase 9