[Mutation and expression of SEMA3B and SEMA3F gene in nasopharyngeal carcinoma].
OBJECTIVE
Though the molecular etiology of nasopharyngeal carcinoma(NPC) is currently unknown, evidence from both loss of heterozygosity analysis and functional studies suggested that there are NPC-associated tumor suppressor genes(TSGs) residing in chromosome 3p21.3. Recently, two members of semaphorin family, SEMA3B and SEMA3F gene, located at 3p21.3, were characterized as TSGs. Studies showed that SEMA3B and SEMA3F are capable of suppressing the growth of tumor cells and inducing apoptosis. Loss of SEMA3B mRNA expression or aberrant SEMA3F cellular localization were found in lung cancers. In order to investigate the involvement of SEMA3B and SEMA3F in NPC, the authors examined both mutation and expression of these two genes in NPC.


METHODS
The entire coding regions, the splice donor/acceptor sites, and partial regulatory regions of SEMA3B and SEMA3F gene were screened for mutations by PCR-sequencing in 21 primary NPC tumors and 2 NPC cell lines(CNE2 and SUNE1). The mRNA expression levels were determined by semi-quantitative RT-PCR analysis.


RESULTS
No somatic mutation was found in either SEMA3B or SEMA3F gene. However, two missense polymorphisms including Thr415Ile and lle242Met were found in SEMA3B in NPC. For the Thr415Ile polymorphism, the Ile allele type which leads to SEMA3B function defects was predominant in NPC with the allele frequency of 64% (27/42). SEMA3B mRNA was expressed in all 6 non-neoplastic nasopharyngeal epithelia, but was absent or down-regulated in 76% (16/21) of primary NPC tumors. No significant difference of SEMA3B expression was observed between NPC and noncancerous controls.


CONCLUSIONS
High frequency of SEMA3B expression alterations suggests that the inactivation of this gene was strongly associated with NPC. SEMA3B may be a tumor suppressor on 3p21.3 involved in NPC.
Liu
Xiao-Qiong
XQ
Department of Pathology, Cancer Center, Sun Yat-sen University, Guangzhou, Guangdong, 510060, P. R. China.
Sun
Min
M
Chen
Han-Kui
HK
Li
Jing-Xiang
JX
Pan
Zhi-Gang
ZG
Long
Qing-Xin
QX
Wang
Xun-Zhang
XZ
Zeng
Yi-Xin
YX
D002294:Carcinoma, Squamous Cell / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D005091:Exons; D016147:Genes, Tumor Suppressor; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis* / Q000235:genetics; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D020125:Mutation, Missense; D009303:Nasopharyngeal Neoplasms / Q000378:metabolism* / Q000473:pathology; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics; D039961:Semaphorins
D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C409766:SEMA3B protein, human; C491230:SEMA3F protein, human; D039961:Semaphorins