Mutational Profiling of Multiple Myeloma Bone Marrow Aspirates As a Clinical Tool for Personalized Treatment of Myeloma

Multiple Myeloma (MM) is increasingly being recognized as a heterogeneous disease. Previous studies have reported various oncogenic mutations in myeloma. Recent genome sequencing studies have revealed activating mutations of BRAF kinase in 4% of patients, a potentially druggable target, underscoring the importance of identifying these and other potential oncogenic mutations. However, a validated methodology for clinical assessment of mutation profiles is lacking. Applying such technologies will be increasingly important to accelerate development of targeted therapies toward tumor-specific oncogenic pathways. Utilizing a high-throughput genotyping platform we evaluated the commonly described somatic mutations in bone marrow aspirates in patients diagnosed with MM.

We developed a CLIA (Clinical Laboratory Improvement Amendments) validated, highly sensitive multiplexed PCR-based assay (SNaPshot) to simultaneously identify 70 genetic loci frequently mutated in 15 cancer genes. This assay has been used at our institution for over 3 years for tumor genotyping and to help guide therapeutic decisions for patients with solid malignancies. To test the value of this approach in patients with MM, we first validated the methodology on MM cell lines followed by testing patient derived bone marrow samples.

The detectable mutations in the 8 MM cell lines tested include: MMIR: KRAS 35G>C, G12A mutation; MMIS: KRAS 35G>C, G12A mutation; H929: NRAS 38G>A, G13D mutation; LR5: KRAS 35G>C, G12A mutation; RPMI8226: TP53 743G>A, R248Q mutation;U266: no mutations identified; OPM2: NRAS 182A>T, Q61L mutation; OPM1: TP53 524G>A, R175H mutation.

Thirty six bone marrow aspirates from patients with MM have been analyzed to date. Tweny five percent of patients had a detectable mutation, with KRAS mutation in 17%, NRAS in 5% and TP53 in 3%. Additional data in a larger cohort is currently being analyzed and will be presented.

Oncogenic driver mutations can be detected by SNaPshot from routinely-collected bone marrow aspirate samples. Experience from lung and breast cancer studies indicates that while the type and frequency of mutation varies somewhat by tumor phenotype, the common oncogenic mutations are often found in isolation. Broad tumor mutational analysis will be helpful to efficiently tailor personalized therapies based on individual tumor genetic profiles.

Dias-Santagata:Bio-Reference Laboratories, Inc.: Consultancy. Borger:Bio-Reference Laboratories, Inc: Consultancy. Iafrate:Bio-Reference Laboratories, Inc: Consultancy. Raje:Eli-Lilly: Research Funding; Amgen: Research Funding; Acetylon: Research Funding; Millennium: Consultancy; Celgene: Consultancy; Onyx: Consultancy.