Epigenetic inactivation of the candidate 3p21.3 suppressor gene BLU in human cancers

Abstract

Many distinct regions of 3p show frequent allelic losses in a wide range of tumour types. Previously, the BLU candidate tumour suppressor gene (TSG) encoded by a gene-rich critical deleted region in 3p21.3 was found to be inactivated rarely in lung cancer, although expression was downregulated in a subset of lung tumour cell lines. To elucidate the role of BLU in tumorigenesis, we analysed BLU promoter methylation status in tumour cell lines and detected promoter region hypermethylation in 39% lung, 42% breast, 50% kidney, 86% neuroblastoma and 80% nasopharyngeal (NPC) tumour cell lines. Methylation of the BLU promoter region correlated with the downregulation of BLU transcript expression in tumour cell lines. Expression was recovered in tumour cell lines treated with 5-aza 2-deoxycytidine. Exogenous expression of BLU in neuroblastoma (SK-N-SH) and NSCLC (NCI-H1299) resulted in reduced colony formation efficiency, in vitro. Furthermore, methylation of the BLU promoter region was detected in primary sporadic SCLC (14%), NSCLC (19%) and neuroblastoma (41%). As frequent methylation of the RASSF1A 3p21.3 TSG has also been reported in these tumour types, we investigated whether BLU and RASSF1A methylation were independent or related events. No correlation was found between hypermethylation of RASSF1A and BLU promoter region CpG islands in SCLC or neuroblastoma. However, there was association between RASSF1A and BLU methylation in NSCLC (P ¼ 0.0031). Our data suggest that in SCLC and neuroblastoma, RASSF1A and BLU methylations are unrelated events and not a manifestation of a regional alteration in epigenetic status, while in NSCLC there may be a regional methylation effect. Together, these data suggest a significant role for epigenetic inactivation of BLU in the pathogenesis of common human cancers and that methylation inactivation of BLU occurs independent of RASSF1A in SCLC and neuroblastoma tumours.

Inhibition of tumor growth and metastasis in vitro and in vivo by targeting macrophage migration inhibitory factor in human neuroblastoma

“…BLU is also inactivated in neuroblastoma. Methylation of the BLU promoter region (inactivation of BLU) in neuroblastoma inversely correlates with tumor stage (Agathanggelou et al, 2003). These data suggest that BLU is one of the candidate tumor suppressor genes.…”

“…BLU is abundantly expressed in normal lung tissue. However, its expression is drastically reduced in a subset of lung tumor cell lines (Agathanggelou et al, 2003). BLU is also inactivated in neuroblastoma.…”

Allele loss and epigenetic inactivation of 3p21.3 in malignant liver tumors

“…MSP was performed using specific primers and conditions already described. 2,3,8,15,19,24 Detailed primer sequences are available on request. Briefly, a 20 ml reaction volume contained 150 ng bisulfite-modified DNA, 1 Â PCR buffer, 1.5 mM MgCl 2 , 0.16 mM dNTPs, 0.25 mM specific primer mix (forward and reverse primers) and 1 unit Taq enzyme (Roche, Mannheim, Germany).…”

“…BLU promoter region hypermethylation was observed in cervical cancer, 18 lung, breast, kidney, nasopharyngeal and neuroblastoma cell lines. 19 This study was performed to analyze the status of RASSF1A, SEMA3B and BLU in malignant liver tumors.…”

Tumor suppressor BLU inhibits proliferation of nasopharyngeal carcinoma cells by regulation of cell cycle, c-Jun N-terminal kinase and the cyclin D1 promoter

“…EBV plays a crucial role in the clonal expansion of pre-malignant cells [4], and regionally prevalent viral strains may be responsible for carcinogenesis [5]. Genetic or epigenetic changes of BLU are frequent in NPC [6-8]. …”