Multiple Myeloma (MM) is the second most common hematologic malignancy in the United States, diagnosed in approximately 14,500 Americans each year, and is responsible for 2% of all cancer deaths ( MM is an incurable malignancy of antibody-secreting plasma B-cells whose etiology is poorly understood. Chromosomal translocation t(4;14)(p16.3;q32.33) is associated with shorter overall survival and is found in 15% of MM patients. The candidate oncogene WHSC1 (MMSET) at 4p16.3 encodes a histone methyltransferase over-expressed as a result of the t(4;14) in MM cells. Surprisingly, over-expression of WHSC1 cDNA's failed to transform cell lines or to induce any phenotype when expressed in mice. We identified ACA11, an orphan box H/ACA small nucleolar RNA (snoRNA) encoded hosted within WHSC1 at 4p16.3, to be up-regulated in cell lines and MM patient samples harboring t(4;14). ACA11 modulates oxidative stress, contributes to MM cell growth and confers resistance to chemotherapy. ACA11 is a novel oncogenic non-coding RNA and is also expressed in other cancer types. Mutations that cooperate with t(4;14) in myeloma initiation are unknown, but chromosome 13 deletions (Del(13)) are highly correlated with the t(4;14) in MM. Del(13) is found in 85-94% of patients with t(4;14) and associated with poor prognosis. We mapped a minimally deleted region in MM patient samples to the retinoblastoma (RB1) gene at 13q14. Our model is that ACA11 expression cooperates with RB1 loss to cause poor-prognosis MM. We propose to characterize the role of ACA11 in multiple myeloma.
Specific Aim 1 : Cooperation between ACA11 and the histone methyltransferase WHSC1. We hypothesize that ACA11 cooperates with MMSET protein expression in myeloma pathogenesis and that WHSC1 histone methyltransferase activity is required for cooperation. We will co-express wild-type WHSC1 or HMT-dead WHSC1 alone or with ACA11 in cell lines and mice.
Specific Aim 2 :
Aim 2 : How does ACA11 affect levels of ROS and sensitivity to chemotherapy? What domains and partners of ACA11 are required for these effects? Our data suggest that ACA11 modulates reactive oxygen species and resistance to chemotherapy in myeloma. We will determine which residues of ACA11 are required for this function. We hypothesize that ACA11 RNA binding residues will be dispensable for ACA11's oxidative stress function, but that ACA11's protein-binding domains will be critical.
Specific Aim 3 : ACA11-mediated malignant transformation in the context of Rb1 deletion. The long arm of chromosome 13 is deleted in 50% of all MM patients, and in 90% of patients with the t(4;14). We hypothesize that RB1 loss cooperates with the t(4;14) in myeloma pathogenesis. We will test the effects of ACA11 and WHSC1 expression on B-cell development, oxidative stress and transformation in the context of Rb1 deficiency. Lastly, we will [identify target genes of t(4;14) by RNA- sequencing patient samples.] A betting understanding of how the t(4;14) contributes to myelomagenesis has broad implications to cancer biology and will facilitate the development of novel therapeutic approaches to patients with poor-prognosis MM.

Public Health Relevance

We discovered a small RNA molecule (ACA11) activated in multiple myeloma and other cancers that controls resistance to chemotherapy. We will perform experiments in mice to understand how ACA11 causes aggressive myeloma, and will sequence the DNA of myeloma patient cells to find other mutations that cooperate with ACA11 to cause cancer.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Molecular Oncogenesis Study Section (MONC)
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Howcroft, Thomas K
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University of Iowa
Internal Medicine/Medicine
Schools of Medicine
Iowa City
United States
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