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EXECUTIVE SUMMARY

 

Therapeutic Peptides for the Treatment of Metastatic Breast Cancer

 

 

SUMMARY: Siuta Consulting has been retained by the Arizona Biomedical Research Commission to identify partners for a novel treatment of metastatic breast cancer discovered by Dr. Joyce A. Schroeder in the Department of Molecular and Cellular Biology in the Arizona Cancer Center at the University of Arizona.  In vivo mouse data has demonstrated that targeting disease-specific protein interactions through the use of mimetic peptides can effectively treat metastatic breast cancer and represents a novel approach in molecular targeted therapies. 

BACKGROUND:  MUC1 is an oncogenic transmembrane protein.  During cancer progression, MUC1 is overexpressed and interacts with the epidermal growth factor receptor (EGFR) and β-catenin in a tumor-specific manner, resulting in enhanced oncogenic activity.  The MUC1 cytoplasmic domain is composed of 72 amino acids, within which lies a 15 amino acid domain containing sites of EGFR phosphorylation and β-catenin binding.  Dr. Schroeder found that targeting this interaction domain of MUC1 for both EGFR and β-catenin through the utilization of MUC1 dominant-negative peptides could significantly affect breast cancer progression. 

TECHNOLOGY:  Dr. Schroeder has synthesized a 15 amino acid peptide, MUC1 inhibitory peptide (MIP), to determine if it could act in a dominant-negative fashion to block interactions between endogenous MUC1 and EGFR/β-catenin.  In order to allow MIP to gain entrance into the cell, it was synthesized in tandem with a protein transduction domain, PTD4 (PTD4 combined with MIP is designated as PMIP). 

Treatment with PMIP was found to inhibit breast cancer cell lines in vitro and to inhibit tumor growth and recurrence in a metastatic xenograft model.  To determine the efficacy of PMIP on spontaneous breast cancer, the MMTV-pyV mT transgenic mouse was treated with PMIP, resulting in spontaneous tumor regression and inhibition of tumor growth, with no observable toxicity. 

The following in vivo experiments demonstrate the efficacy of PMIP in the inhibition of cancer progression: 

PMIP inhibits tumor growth and recurrence in a xenograft breast cancer model:

  • The first experiment was run to examine whether human PMIP (hPMIP) could alter the metastatic potential of MDA-MB-231 breast cancer cells implanted into the fat pad of severe combined immune deficiency (scid) mice.  In this experiment, cells were allowed to establish a large tumor mass (500 mm3) and mice were injected i.p. for 21 days with hPMIP or control peptide (PTD4).  At the end of treatment, primary breast tumors were resected and animals were followed to examine rates of tumor regrowth and/or metastasis to secondary mammary glands.  While regrowth and secondary mammary gland tumors were found in equal number for both treatment groups, the tumor volume for the control treated animals averaged 760 mm3 while the PMIP treated averaged only 73 mm3.  Mice were not treated with drug during the 10 days in which regrowth was followed.  A decrease in the tumor size in the hPMIP treated animals compared to control was also noted.
  • To determine potential effects of hPMIP on primary tumor growth, the MDA-MB-231 xenograft experiment was repeated (21 days of drug treatment), but began treatment at a smaller tumor size (100 mm3).  In this study, tumors continued to grow after the end of drug treatment and weren’t resected until the primary tumors had reached 800 mm3, which allowed evaluation of tumor spread.  Treatment with hPMIP resulted in a significant decrease in tumor size compared to control treated animals.  This corresponded to a significant increase in the length of time required for hPMIP treated mice to reach resection size of 800 mm3.  Although treatment ended approximately 20 days prior to resection, it was observed that hPMIP treatment substantially decreased the amount of tumor regrowth and spread 10 days after resection.  Together, these data demonstrated that hPMIP treatment can inhibit tumor growth, spread and recurrence in a highly metastatic breast cancer model.

PMIP inhibits tumor growth and induces regression in spontaneous breast cancer:

  • This experiment determined how mouse PMIP (msPMIP) would effect tumor initiation and progression in a mouse model which better recapitulates human breast cancer.  The MMTV-pyV mT transgenic model of breast cancer strongly mimics human breast cancer by activating multiple signaling pathways, including AKT, src and shc.  Studies have demonstrated that the resulting breast cancer pathologically and molecularly mimics the full progression of hyperplasia, ductal carcinoma in situ and adenocarcinomas observed in human disease.  To determine if peptide could be delivered to the mammary glands and tumors of these animals, FITC-labeled msPMIP was injected and peptide retention was analyzed 1 hour and 4 hours post-injection.  At one hour, FITC was detected throughout the animal’s body cavity, including all organs.  Four hours after injection, FITC-msPMIP was found to be retained selectively in the mammary gland tumor and in the colon and skin.
  • To determine the effects of msPMIP on spontaneous breast cancer progression, MMTV-pyV mT mice bearing mammary gland tumors of ≥0.5cm in diameter were treated for 21 days with either msPMIP or PTD4 control peptide.  Treatment had a dramatic effect on tumor growth, as msPMIP significantly slowed the total tumor growth from ~590% to ~194% over the 21 days of treatment.  Additionally, PMIP treatment significantly decreased the tumor growth rate to only 25 mm3/day compared to 69 mm3/day in control (PTD4) treated tumors.  Treatment of MMTV-pyV mT mice with hPMIP (as opposed to msPMIP) had no effect on tumor growth, emphasizing the amino acid specificity of PMIP.
  • Analysis of the overall size of tumors that arose throughout the study demonstrated that while 13% of the tumors in the control group had reached larger than 500 mm3 by the end of the study, only 1% of the msPMIP treated group reached that size.  As this transgenic model has continual expression of the polyoma middle T transgene throughout the study, the effects of drug treatment on the generation of new tumors was examined.  Although both msPMIP and control (PTD4) groups had a similar number of tumors sized 100-300 mm3 at the beginning of treatment, this number doubled by the end of treatment in the control group, but remained the same in the msPMIP group.  This data indicated that PMIP treatment was inhibiting tumor initiation in this model.  To analyze tumor initiation further, the percent of tumors that were initiated during drug treatment (initiation equals percent of tumor transitions from 0 mm3 to 100 mm3) was evaluated. This analysis demonstrated that in the msPMIP group there was a significant decrease of tumor initiation during the study.

PUBLICATIONS: 

The following five publications provide background information on MUC1:

1. M. R. Pochampalli, R. M. Bejjani and J. A. Schroeder, MUC1 is a Novel Regulator of ErbB1 Receptor Trafficking, Oncogene, 26, 1693-1701 (2007)

2. M. R. Pochampalli, B. G. Bitler and J. A. Schroeder, Transforming Growth Factor α–Dependent Cancer Progression is Modulated by MUC1, Cancer Res., 67 (14), 6591-6598 (2007)

3. J. A. Schroeder, A. A. Masri, M. C. Adriance, J. C. Tessier, K. L. Kotlarczyk, M. C. Thompson and S. J. Gendler, MUC1 Overexpression Results in Mammary Gland Tumorigenesis and Prolonged Alveolar Differentiation, Oncogene, 23, 5739-47 (2004)

4.  J. A. Schroeder, M. C. Adriance, M. C. Thompson, T. D. Camenisch and S. J. Gendler, MUC1 Alters β-Catenin-Dependent Tumor Formation and Promotes Cellular Invasion, Oncogene, 22, 1324-32 (2003)

5. J. A. Schroeder, M. C. Thompson, M. M. Gardner and S. J. Gendler, Transgenic MUC1 Interacts with Epidermal Growth Factor Receptor and Correlates with Mitogen-Activated Protein Kinase Activation in the Mouse Mammary Gland,  J. Biol. Chem., 276 (16), 13057-64 (2001)

Another manuscript describing the current research is being prepared for publication and is available upon request.

PATENT STATUS:  United States Patent Application Number 20060293234 entitled "Therapeutic Peptides for the Treatment of Metastatic Cancer" was filed on April 17, 2006 and published on December 28, 2006.   The corresponding PCT Patent Application Number WO2006113667 was also filed on April 17, 2006 and published on October 26, 2006.  Both can also be provided upon request.

LICENSE TERMS:  A worldwide exclusive license is available.  Alternatively, funding for continued research in Dr. Schroeder’s lab in exchange for an option for an exclusive license is also available.