We aimed to noninvasively visualize cellular interactions in living systems. Target recognition and cell-cell contacts are crucial to numerous physiological processes, including metastatic disease.  However, there are few practical and user-friendly methods to globally survey such interactions in whole organisms.  In this CAREER award, we developed chemical probes and noninvasive imaging platforms to capture cellular interactions in physiologically relevant environments.  The technologies relied on bioluminescence imaging (BLI).  BLI is a powerful technique for visualizing cells and other features in rodent models.  This imaging modality employs enzymes (luciferases) that produce light upon incubation with small molecule substrates (luciferins).  Luciferase-luciferin pairs can be introduced into non-luminescent cells and provide a readout on cell movements, gene expression, and other features over time.  Unfortunately, conventional bioluminescence imaging draws attention to areas with the largest numbers of cells (i.e., primary tumor masses) that overshadow smaller pockets of metastatic cells.

We re-engineered bioluminescent probes to produce light only when two distinct cell populations come into close proximity (e.g., tumor cell entry into distant tissues).  This approach can illuminate more rare cell populations (e.g., metastatic cells) and provide a unique vantage point in imaging analysis.  Throughout the CAREER award, we focused on two major classes of probes.  One group comprised functionalized (“caged”) luciferins that are preferentially activated by one cell type (e.g., at a metastatic site) and utilized by a second cell type (e.g., infiltrating tumor cells).  A second group comprised “split” versions of luciferase that reassemble (and thus “turn on” photon production) when cells come into contact.  Our work also produced a variety of new luciferase and luciferin scaffolds, in addition to novel platforms for imaging cell contacts with small molecule activators.  The probes were evaluated in cultured cell models and, in some cases, in vivo models.  Their continued application will facilitate studies on tumor migration to distant tissues.  Such studies have the potential to reveal new insights into how tumor-immune, tumor-stromal, and other contacts impact malignancy.

The imaging probes developed in our research were implemented into several local outreach activities, including a luminescence screening laboratory (for undergraduates) and imaging demonstrations (for middle school students).  We also mentored local students working on imaging platforms in their high school chemistry class.  Collectively, these activities exposed a variety of students to the roles of optical imaging in scientific discovery and laboratory research.  Our outreach program also included a seminar series to introduce undergraduate and graduate students to a diverse set of scientific careers.  These seminars highlighted the impacts of scientific professions in society at large.  

  The broader impacts of the research and education plan were several fold.  First, the bioluminescent tools enabled the direct interrogation of cellular interactions not currently possible with existing toolsets. Such probes can provide new views into biological systems and cancer progression.  Bioluminescence technology is also used in a wide variety of disciplines, including materials science, neurobiology, and infectious disease.  Thus, the imaging tools are likely to inspire new discoveries in these and other areas.  Second, our research provided a highly interdisciplinary training ground for students.  Graduate and undergraduate students involved in these studies became proficient at designing and synthesizing small molecule probes, engineering proteins, and performing imaging studies.  Third, our work in bioluminescent probe development was incorporated into a variety of educational outreach programs that have impacted large numbers of students.  These students learned about the challenges and excitement associated with optical imaging and research in general.  Last, our outreach work exposed students to the impacts of science in society by highlighting unique career opportunities.

Last Modified: 10/21/2019
Modified by: Jennifer Prescher