Abstract 4647: Clinical Implications of Rabphillin-3A-Like (RPH3AL/NOC2) Gene Alterations in Breast Cancer
Authors: Salih Chura , Jia Xu , Shanmugam Chandrakumar , Katkoori Venkat R. , Callens Tom , Messiaen Ludwine M. , Hameed Omar , Manne Upender 
Published: February 2011

Abstract
Background: The Rabphillin-3A-like (RPH3AL) gene, located at the 17p13.3 locus, has been reported to be involved in progression and metastasis of colorectal cancer. Since there have been no studies of this gene in breast cancer (BC), mutations and loss of heterozygosity (LOH) of RPH3AL in BCs were evaluated.
Methods: BCs (n=104) and matching benign tissues were evaluated for LOH by use of two locus-specific polymorphic markers (D17S1866 and D17S643) and ABI-3100 sequencing technology. Of 104 cases, 16 had corresponding snap-frozen BCs and benign epithelial tissues. The cDNA samples of these frozen cases were analyzed for RPH3AL mutations by RT-PCR and direct sequencing. Since most of the missense mutations were located in the exon-6 region, the genomic DNA samples of 68 (of 104) BCs and their corresponding benign tissues were assessed only for exon 6 by the use of exon-6 specific primers. Additionally, 96 (of 104) BCs and the corresponding control tissues were analyzed for germ line mutations at 43 base pairs downstream from exon-6. Mutations and LOH status were correlated with clinicopathologic features of BCs and patient overall survival by chi-square and Kaplan-Meier analyses, respectively.
Results: LOH analysis demonstrated that 69 of 99 (70%) informative cases exhibited LOH in at least one marker. In total, 19% (13 of 68) of BCs exhibited missense point mutations in the coding region (exon-6) of RPH3AL. Six BCs exhibited mutations at codon 175, two BCs at codon 200, one BC had double mutations at codon 178 and 189, and four BCs had single mutations at codons 165, 174, 181 and 196. There was a germ-line mutation (G&gt;T) at 43 base pairs downstream from exon-6. Genotyping of this alteration showed that 31% (30 of 96) of BCs were homozygous for the G/G allele, 56% (54 of 96) were heterozygous for G/T, and 13% (12 of 96) were homozygous for T/T. In our correlative analysis, most BCs with mutations were associated with lymph-node metastases (9 of 13, 69%) and with an allelic loss (8 of 13, 62%). The G/G alleles were more commonly found in African-Americans than Caucasians (χ2, p=0.003), in ER/PR positive BCs than in ER/PR negative BCs (χ2, p=0.03), and in BCs with advanced stage (χ2, p=0.02). The incidence of LOH increased with nodal metastasis (χ2, p=0.04) and tumor size (χ2, p=0.05) of the BCs. Furthermore, LOH was significantly associated with poor patient survival (log rank, p=0.002).
Conclusions: The results suggest that genetic alterations in the RPH3AL gene are associated with aggressive behavior of breast cancer. (Grant Support: UAB-Breast SPORE-Pilot and Susan G. Komen Breast Cancer Foundation, POP138306).
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4647.