Richard Halberg, PhD

Portrait of Richard Halberg, PhD
Associate Professor
Medicine
Address: 
K4/532 CSC
600 Highland Avenue
Madison, WI 53792
Telephone: 
(608) 263-8433
Focus Groups: 
Cancer Biology
Education: 
PhD, Biochemistry, Michigan State University
Post-doctoral, Molecular Genetics, University of Wisconsin - Madison
Research Summary: 
Tumors are often heterogeneous with respect to many features. My research focuses on identifying sources of heterogeneity and determining how such heterogeneity impacts prevention and treatment. Novel concepts are being tested with a unique experimental platform consisting of recently developed animal models and state-of-the-art imaging. The results could potentially shift current paradigms in cancer biology.
Research Detail: 

Do intestinal tumors arise from mutation(s) in a single somatic progenitor cell and its descendants? This fundamental question in cancer biology has actually been addressed by only a few studies over the past four decades (1-3). The consensus was that human colonic tumors are monoclonal until Novelli and colleagues demonstrated that the majority of early adenomas isolated from an XO/XY mosaic individual with familial adenomatous polyposis (FAP) have a polyclonal structure (4). A major criticism of this study was the inherent instability of the XO/XY karyotype; this concern was overcome in a study by Merritt and colleagues in which early adenomas were analyzed from C57BL/6J (B6) mice carrying the Min allele of Apc and chimeric for ROSA26 (R26), a ubiquitously expressed cell lineage marker (5). The majority of tumors in this mouse model of FAP were polyclonal. Thus, tumors that develop in the mammalian intestine may be derived from two or more populations of neoplastic cells, but this structure was largely concealed in earlier studies because it was undetectable with the technology of the time.

The high tumor multiplicity of the mice in the study of Merritt and colleagues made it difficult to eliminate the possibility that polyclonality arose by random collision of distinct initiated clones as opposed to some form of clonal interaction. My colleagues and I tested the random collision hypothesis by using Min mice that were also homozygous for the tumor suppression allele of Mom1. Despite the markedly reduced tumor multiplicity in these mice, the observed fraction of overtly polyclonal heterotypic adenomas was significantly higher than predicted by the random collision hypothesis (6).

 

  1. My central hypothesis is that interactions among initiated clones within a single tumor in the mammalian intestine provide a selective advantage during formation, growth, and progression. Members of my laboratory will test this hypothesis by addressing three fundamental questions:
  2. Does the polyclonality of early intestinal tumors depend on the pathway of tumorigenesis? We will analyze tumors from mice treated with either ethylnitrosourea or azoxymethane, mice in which tumorigenesis is initiated because of a mutation in the TGF-beta signaling pathway, and mice in which Apcis inactivated somatically by silencing. If interactions among transformed clones within a single tumor provide a selective advantage, polyclonality should be common in all of these distinct mouse models.
  3. How do polyclonal tumors form in the mammalian intestine? In models in which polyclonality is evident, we will test several different hypotheses that could explain the formation of heterotypic tumors. Our initial study of Min mice chimeric for R26 expression indicated that the most likely explanation involved clonal interactions occurring over one to two crypt diameters. We will extend this work by attempting to determine the nature of clonal interactions using statistical approaches. An initiated clone might transform one or more neighboring clones (recruitment). Alternatively, polyclonal tumors might form because two or more independently initiated clones are simply juxtaposed (cooperation).
  4. Does polyclonality persist as adenomas progress to invasive adenocarcinomas in the intestine? We will monitor longitudinally tumors in three mouse models using two complementary state-of-the-art imaging platforms, microCT and optical colonoscopy. Preliminary data indicate colonic tumors in Min mice have different fates: some grow and progress, some remain static, and some regress. Our colleagues have demonstrated that this is also true of colonic tumors in humans (7). The different fates may simply reflect different clonal structures.

 

These studies will rigorously test the long-held view that colonic tumors are derived from a single progenitor and progress to malignancy as mutations drive successive rounds of clonal expansion. A combination of newly developed mouse models, statistical analyses, and technologies will be employed. My R01 proposal focused on these studies of tumor polyclonality recently received an outstanding score (Priority Score 121; Percentile 0.9%). The results could profoundly change our understanding of tumorigenesis in the mammalian intestine. In 2000, Hanahan and Weinberg stated, "those researching the cancer problem will be practicing a dramatically different type of science than we have experienced over the past 25 years. Surely much of this change will be apparent at the technical level. But ultimately, the more fundamental change will be conceptual" (8). A deep understanding of this issue, the importance of clonal interactions for intestinal neoplasia, can impact the development of management strategies for this disease.

Selected Publications: 
Thliveris AT, Schwefel B, Clipson L, Plesh L, Zahm CD, Leystra AA, Washington MK, Sullivan R, Deming DA, Newton MA, Halberg RB. Transformation of Epithelial Cells through Recruitment Leads to Polyclonal Intestinal Tumors. Proceedings of the National Academy of Academy of Science, In press.
Deming DA, Leystra AA, Nettekoven L, Sievers C, Miller D, Middlebrooks M, Clipson L, Albrecht DM, Bacher J, Washington MK, Weichert JP, Halberg RB. PIK3CA and APC mutations are synergistic in the development of intestinal cancers. Oncogene, In press.
Deming DA, Leystra AA, Farhoud M, Nettekoven LA, Clipson L, Albrecht DM, Washington MK, Sullivan R, Weichert JP, Halberg RB. mTOR inhibition elicits a dramatic repsonse in PI3K-dependent colon cancers. PLOS One 8(4):e60709, 2013.
Leystra AA, Deming DA, Zahm CD, Farhoud M, Paul Olson TJ, Hadac JN, Nettekoven LA, Albrecht DM, Clipson L, Sullivan R, Washington MK, Torrealba JR, Weichert JP, Halberg RB. Mice expressing activated PI3K develop advanced colon cancer. Cancer Research 72(12):2931-36, 2012.
Irving AA, Halberg RB, Albrecht DM, Plum LA, Krentz KJ, Clipson L, Drinkwater N, Amos- Landgraf JM, Dove WF, DeLuca HF. Supplementation by vitamin D compounds does not affect colonic tumor development in vitamin D sufficient murine models. Archives of Biochemistry and Biophysics 515(1-2):64-71, 2011.
Thliveris AT, Clipson L, White A, Waggoner J, Plesh L, Skinner B L, Zahm CD, Sullivan R, Dove WF, Newton MA, Halberg RB. Clonal structure of carcinogen-induced intestinal tumors in mice. Cancer Prevention Research 4(6):916-23, 2011.
Halberg RB, Waggoner J, Rasmussen, White A, Clipson L, Prunuske AJ, Bacher JW, Sullivan R, Washington MK, Pitot HC, Petrini JHJ, Albertson DG, Dove WF. Long-lived Min mice develop advanced intestinal cancers through a genetically conservative pathway. Cancer Research 69:5768-575, 2009.
Durkee BY, Weichert JP, Halberg RB. Small animal microCT colonography. Methods. 2009 Aug 3 [Epub ahead of print].
Huttlin EL, Chen X, Barrett-Wilt GA, Hegeman AD, Halberg RB, Harms AC, Newton MA, Dove WF, Sussman MR. Discovery and validation of colonic tumor-associated proteins via metabolic labeling and stable isotopic dilution. Proc Natl Acad Sci U S A 106:17235-40, 2009.
Durkee BY, Shinki K, Newton MA, Iverson C, Weichert J, Dove WF, Halberg RB. Longitudinal assessment of colonic tumor fate in mice by computed tomography and optical colonoscopy. Academic Radiology 16:1475-82, 2009.