Arnold J. Levine, PhD

2012-2013 BCRF Project(s):
1) Dr. Levine is renowned for his work in establishing p53 as a tumor suppressor gene, one of the body's most important defenses against many forms of cancer. Further contributing to our understanding of the molecular basis of cancer, Dr. Levine is currently studying the potential correlations between p53 mutations and breast cancer stem cells, also characterized as tumor initiating cells. Over the past few years there has arisen the concept of a breast cancer stem cell that produces a tumor and a more differentiated set of cell types and it is the stem cell that is required for the malignant state. Whether a cancer stem cell arises from a normal breast stem cell that has become cancerous or de-differentiates from a more developed tumor cell remains unclear.

A year ago, five publications demonstrated that an induced pluripotent stem cell could be efficiently produced (up to 80% of the cells) in cell culture from a differentiated fibroblast only in the absence of the p53 tumor suppressor gene. Based upon this observation, Dr. Levine's team tested the hypothesis that breast cancer stem cells arise efficiently in tumors with p53 mutations. They employed RNA microarrays to demonstrate that breast cancers with p53 mutations had stem cell signatures. These observations have been confirmed with several other cancers and in a series of experiments carried out in cell culture. Based upon these studies, they will attempt to develop a new diagnostic test to identify breast cancers with a poor prognostic outcome. This diagnostic can also be employed as a biomarker to indicate which drug treatments will be useful for a particular tumor.

Mid-year Progress: Over the past few years, the concept of a breast cancer stem cell has arisen that produces a tumor and a more differentiated set of cell types. It is thought that the stem cell is required for the malignant state. A great deal of evidence has suggested that cells can undergo efficient epigenetic reprograming to become induced pluripotent stem cells but this requires the loss of a functional p53 protein. Based upon the observation that the loss of a functional p53 protein seems to play a role in the formation of breast cancer stem cells, Dr. Levine's group tested the hypothesis that these cells arise efficiently in tumors with p53 mutations. Employing RNA micro arrays, they showed that breast cancers with p53 mutations had stem cell signatures. Central to these signatures was the over-expression of two proteins, MELK and TMEM97. The researchers have produced antibodies directed against these proteins and obtained cell lines that over-express these proteins and produce tumors in laboratory models. They have obtained a small molecule inhibitor of the MELK protein kinase and are testing it and other derivatives to determine if MELK activity drives the growth of these tumors. Monoclonal antibodies directed against the cell surface protein TMEM97 are being prepared. This trans-membrane protein inserts cholesterol into the membrane of these cancer cells, and the investigators are testing whether or not the monoclonal antibodies inhibit tumor cell growth. The goal of this project is to develop novel potential therapeutic agents that inhibit or kill cells from triple negative and HER2/neu breast cancers.

2) Co-Investigator: Kim Hirshfield, MD, PhD, The Institute for Advanced Study, Princeton, and The Cancer Institute of New Jersey, New Brunswick, NJ

Genetic variations between individuals can confer a risk for the development of breast cancer, the age of onset of a breast cancer, the response to treatment for a breast cancer and the risk of developing a re-occurrence of a breast cancer. Drs. Levine and Hirshfield have identified three genes, ZNF585B, ZNF709, and ZNF788, which are expressed in normal breast tissue but are not in many breast cancers. When the ZNF genes are turned off, there is an increased level in the expression of two different human endogenous retroviruses in the cancer cells. These retroviruses insert their DNAs into the host genome and can cause mutations that activate oncogenes and inactivate tumor suppressor genes. As such, these zinc finger genes are candidates for new breast cancer tumor suppressor genes. Drs. Levine and Hirshfield will test this hypothesis.

Mid-year Progress: Examining the polymorphisms in the p53, p63 ands p73 pathways in humans has uncovered a new class of oncogenes involved in triple negative breast cancers. Drs. Hirshfield and Levine have identified a gene fusion copy number polymorphism present in 25% of the Western Caucasian population that appears to be transcriptionally silent in normal tissue but expressed in triple negative breast cancers. The extra copy gene fusion is composed of a fusion of the KANSL-1 gene and the ARL17A gene. KANSL-1 is part of a histone acetyltransferase found in the MLL, NSL and MSL complexes that acetylate and regulate H-4 histones as well as the p53 and ATM proteins. When the c-DNA from this fusion gene that is expressed in triple negative breast cancers is expressed in cell culture it inhibits the acetylation of histones and alters transcription of many genes. It also inhibits p53 activity, which responds to DNA damage and genomic instability by the killing these cancer cells. The fusion protein blocks ATM activity involved in DNA repair processes. The inhibition of these activities helps to explain why triple negative cancers have genomic instability. These results suggest two sets of drugs (HDAC inhibitors and PARP inhibitors) could be a useful treatment of those cancers with the KAMSL-1-ARL17A fusion gene containing tumors and we are testing these ideas in cell culture. A polymorphism in the PERP gene, which mediates p53-induced apoptosis, has been shown to be associated with recurrence free survival in women who have had both surgery and radiation treatment.

Bio:
Arnold Levine's research centers on the causes of cancer. In 1979, Levine and others discovered the p53 tumor suppressor protein, a molecule that inhibits tumor development. As chair of the National Institutes of Health Commission on AIDS Research and the National Academies Cancer Policy Board, he has helped determine national research priorities. He established the Institute's Center for Systems Biology, which concentrates on research at the interface of molecular biology and the physical sciences; on genetics and genomics, polymorphisms and molecular aspects of evolution, signal transduction pathways and networks, stress responses, and pharmacogenomics in cancer biology.