Abstract 4822: Analysis of somatic copy number alterations associated with poor prognosis and progression of multiple myeloma in African Americans

Abstract

Abstract The plasma cell malignancy Multiple Myeloma (MM) is a rare but deadly form of cancer with 5 year survival rates of ∼30%. The disease exacts an especially heavy burden on African American (AA) patients. In fact, African Americans are twice a likely to be diagnosed with and die from MM as compared to Caucasian Americans. Although socio-economic factors likely influence this disparity, the role of biology has not been ruled out. We have profiled ∼250 MM tumors for somatic copy number alterations using array-based Comparative Genomic Hybridization (aCGH) and Gene Expression Profiling as part of the Multiple Myeloma Genomics Initiative. To determine if somatic alterations may play a role in the disparity in incidence and/or severity of MM in AA, we compared the frequency of specific chromosomal aberrations in genes and genomic regions previously found to be involved in progression and poor outcome in MM among a cohort of one hundred ninety-six (196) patients including 16 African Americans and 180 Caucasians. The frequency of occurrence (expressed as a percentage) was determined for each of the following aberrations: 1p deletion, homozygous deletion of p18, chromosome 13 deletion, and chromosome 13 monosomy. No significant difference was detected in the frequency of chromosome 13 deletion and chromosome 13 monosomy between the two groups. However, significant differences were observed for chromosome 1p alterations. Homozygous deletion at the p18 locus at 1p occurred in 12.5% (2/16) of tumors from AA patients and 2.8% (5/180) of CA patient tumors (p = 0.045). We further stratified tumors by hyperdiploid or non-hyperdiploid status using a-CGH profiles to determine ploidy status. Most significantly, p18 homozygous deletion was found in 25% (2/8) of AA patients with non-hyperdiploid tumors and in only 1.2% (1/83) of CA patients with non-hyperdiploid tumors (p=3.2 × 10-4). A nominally significant difference among non-hyperdiploid patients was also present for overall 1p deletion, which was observed in 2/8 (25%) of AA non-hyperdiploid tumors and 33/83 (40%) of CA with non-hyperdiploid tumors (p=0.05). No differences were observed for 1p deletion or p18 homozygous deletion among hyperdiploid tumors between AA and CA patients. These results suggest that deletions at 1p are more common among African American MM patients. Furthermore, homozygous deletion encompassing the p18 locus is more significantly common among AA MM patients, especially AA patients with non-hyperdiploid tumors. As 1p deletion and p18 homozygous deletion have been linked to poor outcome, our results suggest that the increased frequency of these alterations in tumors from AA patients may in part explain the disparity in unfavorable outcomes seen among AA MM patients 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 4822.