Expression of SMARCF1, a truncated form of SWI1, in neuroblastoma

Previously we cloned and mapped a B120 gene to human chromosome 1p35-36.1 w here possible suppressor genes for various neuroendocrine tumors including neuroblastoma have been mapped. Very recently, B120 was identified as a tru ncated form of p270, a putative human counterpart of SWII, In the present s tudy, expression of the B120 gene product was immunohistochemically investi gated in 23 neuroblastomas, We also examined B120 expression in neural stem cells in developing brain and intact adrenal medulla, Four of 23 neuroblas tomas strongly expressed B120 gene product in both cytoplasm and nucleus. T he other neuroblastomas expressed B120 gene product in the nucleus; how eve r, the intensity of staining was much weaker and equivalent to that in deve loping human brain stem cells in the subventricular region. B120 gene produ ct was less strongly expressed in intact adrenal medulla, Subsequently, we performed loss of heterozygosity studies on 19 neuroblastomas using the pol ymorphic markers D1S195 and D1S511 located near the B120 gene, Loss of hete rozygosity was observed in three of 19 tumors that abundantly expressed B12 0 protein. Furthermore, neuroblastoma cells were transfected with B120 expr ession vector. These transfected neuroblastoma cells adhered to each other and aggregated Differential display experiments followed by reverse transcr iptase-polymerase chain reaction and Northern blot analysis were performed and three molecules with altered expression in B120-transfected neuroblasto ma cells were identified One of three genes seemed to be a proliferation-re lated and cell cycle-related nucleolar protein, p120, encoding gene. We fur ther characterized the genomic structure of B120. B120 appeared to be encod ed by 17 exons in more than 20-kbp genomic DNA, The present findings contri bute to understanding of the B120 gene, a truncated form of human SWII1, an approved term for which is SMARCF1, in normal cells and neuroblastomas.