NRG1 gene rearrangements in clinical breast cancer: identification of an adjacent novel amplicon associated with poor prognosis

Abstract

Rearrangements of the neuregulin (NRG1) gene have been implicated in breast carcinoma oncogenesis. To determine the frequency and clinical significance of NRG1 aberrations in clinical breast tumors, a breast cancer tissue microarray was screened for NRG1 aberrations by fluorescent in situ hybridization (FISH) using a two-color split-apart probe combination flanking the NRG1 gene. Rearrangements of NRG1 were identified in 17/382 cases by FISH, and bacterial artificial chromosome array comparative genomic hybridization was applied to five of these cases to further map the chromosome 8p abnormalities. In all five cases, there was a novel amplicon centromeric to NRG1 with a minimum common region of amplification encompassing two genes, SPFH2 and FLJ14299. Subsequent FISH analysis for the novel amplicon revealed that it was present in 63/262 cases. Abnormalities of NRG1 did not correlate with patient outcome, but the novel amplicon was associated with poor prognosis in univariate analysis, and in multivariate analysis was of prognostic significance independent of nodal status, tumor grade, estrogen receptor status, and human epidermal growth factor receptor (HER)2 overexpression. Of the two genes in the novel amplicon, expression of SPFH2 correlated most significantly with amplification. This amplicon may emerge as a result of breakpoints and chromosomal rearrangements within the NRG1 locus.

High-resolution analysis of chromosome rearrangements on 8p in breast, colon and pancreatic cancer reveals a complex pattern of loss, gain and translocation

“…The group of breaks at NRG1 and possible cluster of breaks 5 0 of UNC5D are indicated. The most frequent core amplicon (defined previously, Garcia et al, 2005;Prentice et al, 2005) includes ZNF703, previously named FLJ14299, and may extend to RAB11FIP1. The inversion and deletion accompanying the translocation in T-47D illustrates that the distal break may not be the rearrangement that is selected for.…”

“…FGFR1, at 38.4 Mb, although originally proposed as the principle target for amplification in this region, is not included (Ray et al, 2004;Garcia et al, 2005;Prentice et al, 2005). This amplicon we defined using the same array on breast tumour tissues (Garcia et al, 2005), and it was independently identified by Prentice et al (2005).…”

“…The ZNF703/FLJ14299, SPFH2, BRF2 and RAB11FIP1 genes map to this region and their amplification correlates with overexpression. This amplicon was present in 24% of primary breast tumours and found to correlate with poor survival (Garcia et al, 2005;Prentice et al, 2005). The long-suspected amplification target, FGFR1, was excluded from the current consensus amplicon and detected as amplified in fewer, 10-15%, of cases (Theillet et al, 1993;Ugolini et al, 1999;Prentice et al, 2005).…”

“…Our working hypothesis is that the translocations result in aberrant expression of normal or modified heregulins, which act in an autocrine loop on the cancer cells, as in at least one of the cell lines, MDA-MB-175, the translocation results in fusion of NRG1 and secretion of a fusion protein with soluble heregulin-like activity (Schaefer et al, 1997;Liu et al, 1999;Wang et al, 1999). We have subsequently shown that breakpoints in NRG1 are present in about 6% of uncultured breast tumours (Huang et al, 2004 also supported by Prentice et al, 2005).…”

“…large-scale amplifications) attached to 8p12 (Bernardino et al, 1998) and fluorescence in situ hybridization (FISH), CGH and Southern blotting show amplification generally in the region of 8p12 (Dib et al, 1995;Bautista and Theillet, 1998;Davidson et al, 2000), which often, but not invariably, includes FGFR1, and may occasionally extend as far distally as NRG1 (Ugolini et al, 1999). Recent array CGH studies that examine the 8p12 region in breast cancer have concentrated on the definition of the 8p12 amplicon (Ray et al, 2004;Garcia et al, 2005;Prentice et al, 2005). The amplicon has been defined to extend from 36.9 to 37.9 Mb (Garcia et al, 2005).…”