I research receptor protein tyrosine phosphatases, cell adhesion, and signal transduction, as well as PTPs in adherens junctions and desmosomes.
Research Information
Research Interests
Dr. Susann Brady-Kalnay is an expert on cell adhesion molecules in cancer progression, with an emphasis on studying the disregulation of the molecule PTPmu (PTPRM) in brain tumors and other cancers. The Brady-Kalnay Lab is developing platform technologies exploiting their insight into cell adhesion molecule dysfunction in cancer to develop specific molecular imaging agents and novel targeted therapeutics.
Cell Adhesion Molecule Proteolysis is a Key Step in the Loss of Contact Inhibition of Growth and Movement in Cancer
We recently established the existence of a key change in proteolysis of the Receptor Protein Tyrosine Phosphatase PTPmu in human cancer: full length PTPmu protein expression is reduced in aggressive invasive and metastatic tumors due to proteolysis. This includes the high-grade brain tumor, glioblastoma multiforme (GBM). We observed proteolyzed fragments of PTPmu both outside and inside of tumor cells. These fragments have unique signaling features and contribute to the growth and invasiveness of tumor cells. Based on these findings, we proposed that cell adhesion molecule proteolysis is a key step in the loss of contact inhibition of growth and movement observed in cancer cells.
A Platform Technology to See(k) and Destroy Cancer Cells
By applying over three decades worth of Dr. Brady-Kalnay’s research on the Ig superfamily, PTPmu mediated cell adhesion in normal cells, and the study of its proteolysis in cancer cells, we designed peptides that bind to the PTPmu fragments but not the normal protein to specifically detect and image cancer. The most effective peptide for identifying individual cancer cells was SBK2. By conjugating the same peptides to fluorophores, metals, or radioactive isotopes, we created a platform technology that can be used to recognize cancer cells in applications that range from diagnosis to imaging to the targeted treatment of primary, invasive and metastatic tumors to “see(k) and destroy” cancer by creating a new class of visual therapeutics.
Fluorescence Optical Imaging
The ability to image tumors and their invasive edges or boundaries in real time during surgery is of vital importance for effective surgical management of cancer. Yet brain tumors are difficult to image because of the invasive nature of the cancer cells - they migrate away from the main tumor mass in clusters of cells that can’t be seen with either the naked eye or microscopically with white light reflectance. In the laboratory, we have used many innovative imaging tools, including 3-dimensional cryo-image analysis system to visualize nerves, blood vessels, and individual invasive cancer cells in brain tumor models. Based on PTPmu proteolysis, the Brady-Kalnay laboratory developed a set of optical imaging agents to the PTPmu biomarker to visualize tumor cells in vivo. The fluorescent PTPmu agents bind to invading/dispersing cancer cells in models of many tumor types. We are pioneering the use of the fluorescent PTPmu imaging agent for image-guided surgical resection of tumors. The fluorescence-guided surgical technique is currently receiving significant clinical attention given its potential for high level of effectiveness in improving the extent of surgical resection and thus prolonging survival outcomes for cancer patients.
Magnetic Resonance Imaging (MRI)
MRI is an ideal modality for high-resolution tumor imaging and is standard of care for diagnosis and monitoring of treatment especially in brain tumors. This is accomplished by IV administration of a non-specific contrast agent gadolinium (Gd) that enhances areas of large tumor masses where the blood brain barrier is disrupted. This non-specific contrast only labels the center of the primary tumor and is not capable of enhancing the full extent of the tumor including the invasive regions. By conjugating the SBK2 peptide to a chelator, we created an efficient, selectable means to convert the peptide to an MRI imaging agent. This is achieved by complexing an enhancing metal like Gd into the chelator. We demonstrated that the PTPmu (SBK2)-Gd molecular MRI agent can identify a brain tumor lesion more specifically and with higher and more sustained contrast than conventional contrast agents. We are collaborating with the MRI group at CWRU to improve molecular imaging further by using various MRI acquisition techniques including magnetic resonance fingerprinting (MRF) and quantitative MRI.
Positron Emission Tomography (PET) and Radiotherapy
By switching the Gd in the SBK2-chelator for a radioisotope, we create an agent for use in PET imaging. PET has advantages over MRI in many cancer applications, and generally has better sensitivity than MRI. Furthermore, the SBK2 agent can be complexed with an alpha or beta emitting high energy isotopes to deliver a lethal amount of ionizing radiation directly to cancer cells and their immunosuppressive tumor microenvironment.
Novel Therapeutics
Extracellular Modulators
Once again, by exploiting the process of PTPmu proteolysis, we have developed modulators of the cleaved extracellular fragment. The MAM, Ig, and first two FNIII repeats of the PTPmu extracellular domain are necessary for mediating homophilic adhesion between two PTPmu molecules on different cells in trans. This association is hypothesized to be necessary for the proper structuring of cell-cell junctions. Proteolysis of PTPmu results in the generation of the adhesive extracellular fragment and displacement of the catalytically active intracellular domain. We hypothesize that proteolysis of RPTPs is a way for tumor cells to release cell-cell adhesion thereby ensuring invasive and metastatic success. By generating modulators to the PTPmu extracellular domain, we expect to alter the invasive nature of tumor cells.
Intracellular Therapeutics
When full-length PTPmu protein is proteolyzed to yield the extracellular fragment, a cytoplasmic intracellular domain capable of translocating to the nucleus is also produced. Human brain tumors retain the expression of the intracellular fragments. Phosphatase activity of the fragments is important in promoting migration, as inhibition of PTPmu phosphatase activity using a peptide inhibitor targeting the helix-loop helix wedge motif in the intracellular domain of PTPmu blocked tumor cell migration in vitro. In addition, PTPmu intracellular fragments are required for tumor cell survival in vitro, as use of shRNA targeting the intracellular domain reduces tumor cell survival. Finally, we determined that inhibition of PTPmu fragment expression in human cancer cells reduces tumor growth in vivo. As a result of these studies, we developed inhibitors directed to the intracellular domain of PTPmu as novel cancer therapeutic agents.
Awards and Honors
Publications
Molyneaux K, Laggner C, Brady-Kalnay SM. A novel binding pocket in the D2 domain of protein tyrosine phosphatase mu (PTPmu) guides AI screen to identify small molecules that modulate tumour cell adhesion, growth and migration. J Cell Mol Med. 2023 Nov;27(22):3553-3564. doi: 10.1111/jcmm.17973. Epub 2023 Oct 20. PMID: 37860940; PMCID: PMC10660673.
Molyneaux K, Laggner C, Vincent J, Brady-Kalnay S. Small molecule antagonists of PTPmu identified by artificial intelligence-based computational screening block glioma cell migration and growth. PLoS One. 2023 Jul 26;18(7):e0288980. doi: 10.1371/journal.pone.0288980. PMID: 37494327; PMCID: PMC10370706.
Molyneaux K, Laggner C, Brady-Kalnay SM. Artificial Intelligence-Based Computational Screening and Functional Assays Identify Candidate Small Molecule Antagonists of PTPmu-Dependent Adhesion. Int J Mol Sci. 2023 Feb 21;24(5):4274. doi: 10.3390/ijms24054274. PMID: 36901713; PMCID: PMC10001486.
Johansen ML, Vincent J, Rose M, Sloan AE, Brady-Kalnay SM. Comparison of Near-Infrared Imaging Agents Targeting the PTPmu Tumor Biomarker. Mol Imaging Biol. 2023 Aug;25(4):744-757. doi: 10.1007/s11307-023-01799-5. Epub 2023 Jan 25. PMID: 36695968.
Molyneaux K, Wnek MD, Craig SEL, Vincent J, Rucker I, Wnek GE, Brady-Kalnay SM. Physically-cross-linked poly(vinyl alcohol) cell culture plate coatings facilitate preservation of cell-cell interactions, spheroid formation, and stemness. J Biomed Mater Res B Appl Biomater. 2021 Nov;109(11):1744-1753. doi: 10.1002/jbm.b.34832. Epub 2021 Apr 13. PMID: 33847464.
Johansen ML, Perera R, Abenojar E, Wang X, Vincent J, Exner AA, Brady-Kalnay SM. Ultrasound-Based Molecular Imaging of Tumors with PTPmu Biomarker-Targeted Nanobubble Contrast Agents. Int J Mol Sci. 2021 Feb 17;22(4):1983. doi: 10.3390/ijms22041983. PMID: 33671448; PMCID: PMC7922223.
Vincent J, Craig SEL, Johansen ML, Narla J, Avril S, DiFeo A, Brady-Kalnay SM. Detection of Tumor-Specific PTPmu in Gynecological Cancer and Patient Derived Xenografts. Diagnostics (Basel). 2021 Jan 27;11(2):181. doi: 10.3390/diagnostics11020181. PMID: 33513911; PMCID: PMC7911696.
Covarrubias G, Johansen ML, Vincent J, Erokwu BO, Craig SEL, Rahmy A, Cha A, Lorkowski M, MacAskill C, Scott B, Gargesha M, Roy D, Flask CA, Karathanasis E, Brady-Kalnay SM. PTPmu-targeted nanoparticles label invasive pediatric and adult glioblastoma. Nanomedicine. 2020 Aug;28:102216. doi: 10.1016/j.nano.2020.102216. Epub 2020 May 13. PMID: 32413511; PMCID: PMC7573884.
Johansen ML, Vincent J, Gittleman H, Craig SEL, Couce M, Sloan AE, Barnholtz-Sloan JS, Brady-Kalnay SM. A PTPmu Biomarker is Associated with Increased Survival in Gliomas. Int J Mol Sci. 2019 May 14;20(10):2372. doi: 10.3390/ijms20102372. PMID: 31091655; PMCID: PMC6566278.
Anderson CE, Johansen M, Erokwu BO, Hu H, Gu Y, Zhang Y, Kavran M, Vincent J, Drumm ML, Griswold MA, Steinmetz NF, Li M, Clark H, Darrah RJ, Yu X, Brady-Kalnay SM, Flask CA. Dynamic, Simultaneous Concentration Mapping of Multiple MRI Contrast Agents with Dual Contrast - Magnetic Resonance Fingerprinting. Sci Rep. 2019 Dec 27;9(1):19888. doi: 10.1038/s41598-019-56531-7. PMID: 31882792; PMCID: PMC6934650.
Johansen ML, Gao Y, Hutnick MA, Craig SEL, Pokorski JK, Flask CA, Brady-Kalnay SM. Quantitative Molecular Imaging with a Single Gd-Based Contrast Agent Reveals Specific Tumor Binding and Retention in Vivo. Anal Chem. 2017 Jun 6;89(11):5932-5939. doi: 10.1021/acs.analchem.7b00384. Epub 2017 May 22. PMID: 28481080; PMCID: PMC5603198.
Anderson CE, Donnola SB, Jiang Y, Batesole J, Darrah R, Drumm ML, Brady-Kalnay SM, Steinmetz NF, Yu X, Griswold MA, Flask CA. Dual Contrast – Magnetic Resonance Fingerprinting (DC-MRF): A Platform for Simultaneous Quantification of Multiple MRI Contrast Agents. Sci Rep. 2017 Aug 16;7(1):8431. doi: 10.1038/s41598-017-08762-9. PMID: 28814732; PMCID: PMC5559598.
Craig SEL, Wright J, Sloan AE, Brady-Kalnay SM. Fluorescent-Guided Surgical Resection of Glioma with Targeted Molecular Imaging Agents: A Literature Review. World Neurosurg. 2016 Jun;90:154-163. doi: 10.1016/j.wneu.2016.02.060. Epub 2016 Feb 23. PMID: 26915698; PMCID: PMC4915969.
Phillips-Mason PJ, Craig SE, Brady-Kalnay SM. A protease storm cleaves a cell-cell adhesion molecule in cancer: multiple proteases converge to regulate PTPmu in glioma cells. J Cell Biochem. 2014 Sep;115(9):1609-23. doi: 10.1002/jcb.24824. PMID: 24771611; PMCID: PMC4600327.