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
publication describes the current research in greater detail:
B. Bitler, I. Menzl, C. L. Huerta, B.
Sands, W. Knowlton, A. Chang and J. A. Schroeder, Intracellular MUC1 Peptides
Inhibit Cancer Progression,
Clinical Cancer Research, 15:100-109 (2009).
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)
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.