P32: New Functional Target in Breast Cancer Brain Metastasis

Institution: Scripps Research Institute
Investigator(s): Karin Staflin, Ph.D -
Award Cycle: 2009 (Cycle 15) Grant #: 15FB-0104 Award: $71,577
Award Type: Postdoctoral Fellowship
Research Priorities
Biology of the Breast Cell>Pathogenesis: understanding the disease

Initial Award Abstract (2009)

Brain metastases are among the most feared complications in breast cancer, but there are still no effective therapies. Nevertheless, brain metastasis is understudied in basic and clinical research. This is mainly due to a lack of suitable cell and animal models that duplicate the clinical setting to allow study of the molecular mechanisms that underlie breast cancer brain metastasis and define new functional targets for therapeutic intervention. Therefore, we have established new cell lines from breast cancer patients with brain metastasis that exhibit similar growth characteristics in our rodent models as in humans and which express the protein, called p32, in abundance. The p32 protein is expressed by several human cancers, including breast cancer, but its function remains unclear. Evidence suggests that p32 might be involved in tumor cell survival and growth. Our preliminary data demonstrate that the protein p32 is associated strongly with metastatic growth in the brain.

Our aims are to investigate if the p32 protein has a similar function in our new breast cancer brain metastasis animal models. We hope to determine:
1) Is p32 critical for breast cancer brain metastasis, and can targeting p32 stop metastatic growth?
2) Does p32 influence the metabolism of breast cancer cells that grow in the brain?
3) How does p32 influence breast cancer cell survival in the brain?

First we will abolish the protein p32 in breast cancer cells from brain metastases and look at the effects on tumor cell growth in brain of experimental mice. Then, detailed analysis will pinpoint how p32 acts to regulate metastatic growth. To understand if p32 is involved in the metabolism of the tumor cells, we will study their ability to utilize sugar and other nutrients to produce energy. We will look into any changes in cell metabolism after abolishing the protein p32 in breast cancer. If p32 affects the ability of the tumor cells to generate energy, it will have important consequences for tumor cell survival under stress and starvation which is critical during metastasis. We will compare the growth and survival rates of the brain metastatic breast cancer cells with intact p32, or after removing its expression from cells. We will study these effects on cell death (apoptosis) mechanisms in the different tumor models, both in culture and in animals.

Our group has developed unique new human breast cancer cell lines from brain metastases that recapitulate in mice the progression of metastatic brain disease as seen in the clinic. Results from this study might reveal p32 as a good candidate target in breast cancer brain metastasis for future therapeutic intervention in human patients.

Final Report (2010)

Brain metastases are the most feared complication in breast cancer where nearly 30% of patients with advanced disease develop brain lesions. Treatment options are limited and, unfortunately, extend patient survival only for a few weeks or months. Intrinsic mechanisms that allow metastatic breast cancer cells to survive and proliferate within the brain tissue are poorly understood. Therefore, it is of utmost importance that we study these processes to develop new therapeutic approaches to prevent and control this stage of the disease. Our research has focused on a protein called p32. This protein has been implicated in many different cellular processes, and its increased expression was correlated to poor prognosis in patients with breast cancer. The physiological role of p32 and its potential function in breast cancer progression remain to be clarified.

We found that p32 is abundantly expressed by metastatic breast cancer cells and, most importantly, that p32 plays a critical role in brain metastasis. If we take this protein away from breast cancer cells in our experiments, the tumor cells can no longer grow efficiently in the brain in our mouse models. Importantly, this was true for all cell lines that we tested. To understand how p32 promotes brain metastatic growth of breast cancer cells, we looked into a mechanism that we identified earlier as important for brain lesion development. We had found that breast cancer cells that home to the brain are able to adapt their energy metabolism to the specific situation in the brain. By comparing pathways of energy production in breast cancer cells before and after experimental removal of p32, we realized that p32 critically impacts the specific metabolic activities that we had identified as critical for breast cancer cell survival and grow within the brain tissue. An important part of these pathways controls the ability of the tumor cells to induce new blood vessels in the brain that provide nutrients and oxygen to the growing tumor cells. To analyze in detail how p32 promotes breast cancer cell growth in the brain, we focused on the metabolic activities of the tumor cells that control their survival and proliferation. Since p32 is so critical for brain metastasis, we used innovative technologies for a comprehensive analysis of changes that occur in breast cancer brain lesions when we experimentally abolish p32 in the tumor cells and take away their ability to grow in the brain.

Based on our results, we are now beginning to understand these changes. We identified proteins that interact specifically with p32 in breast cancer brain metastases. Studying these interactions and the consequences on breast cancer cell survival and growth in the brain allows us to pin-point new pathways that breast cancer cells use to thrive within the brain microenvironment. Relating these findings to our new results on overall gene expression activities in breast cancer brain metastases, with and without p32, provides us with new insight into the complex functional properties that allow breast cancer cells to develop clinically overt metastases in the brain. Based on our results, the new molecular targets and pathway connections that we identified as drivers of breast cancer brain metastasis, we laid a foundation for developing new therapeutic approaches to stop brain metastasis in breast cancer patients. This is the immediate goal for our upcoming studies.

Site-specific coupling and sterically controlled formation of multimeric antibody fab fragments with unnatural amino acids.
Periodical:Journal of Molecular Biology
Index Medicus: J Mol Biol
Authors: Hutchins BM, Kazane SA, Staflin K, Forsyth JS, Felding-Habermann B, Schultz PG, Smider VV
Yr: 2011 Vol: 406 Nbr: 4 Abs: Pg:595-603

Selective formation of covalent protein heterodimers with an unnatural amino acid.
Periodical:Chemistry and Biology
Index Medicus: Chem Biol
Authors: Hutchins BM, Kazane SA, Staflin K, Forsyth JS, Felding-Habermann B, Smider VV, Schultz PG
Yr: 2011 Vol: 18 Nbr: 3 Abs: Pg:299-303