Mentors

Harvey Herschman, Ph.D. (Primary)
Arion Chatziioannou, Ph.D. (Secondary)

Research Interests:

In Vivo Molecular Optical Imaging - The product of the cycloxygenases (COX), prostaglandins, are autocrines with wide ranging function in the body, including thermoregulation, platelet aggregation, wound healing, water balance, and inflammation. While Cox-1 is constitutively expressed, Cox-2 is induced in response to wounds, infection, general inflammation, and contributes to the inflammatory response. Cox-2 has been shown to be involved in oncogenesis, both as a requirement, and an antagonist, depending on the tumor type.

As expected with an inflammatory response gene, Cox-2 is tightly regulated, ensuring a rapid response both in expression and degradation. An important aspect of post-transcriptional regulation appears to be the 3' untranslated region (3' UTR) of the mRNA sequence. It contains many binding sites which are implicated in increasing or decreasing stability of the message, depending on the binding factor.

Previous studies of the 3' UTR based regulation have been done only in tissue culture studies. In order to see real world effects, a mouse model needed to be created. The Herschman Lab, under Dr. Ishikawa, previously created a knock-in mouse containing Firefly luciferase in place of the COX-2 gene, for use in studying Cox-2 regulation. As is standard practice, the luciferase cDNA was inserted using a cloned SV40 polyadenylation signal, instead of the endogenous 3' UTR of COX-2. While this construct allows for very sensitive imaging, it may not fully reflect the regulation of Cox-2 expression, as the endogenous COX-2 3'UTR, along with its many regulatory elements, are absent.

To remedy this, Dr. Chun Chu created a similar mouse, with the substitution of the SV40 3' UTR, with the COX-2 3' UTR. This will allow us to compare the two mouse breeds to determine the role of the COX-2 3' UTR in expression. As both Drs. Ishikawa and Chu have left the lab, I will continue their work. Using in vivo imaging, I will characterize expression of the Cox-2 reporter system and directly compare to actual Cox-2 protein expression. This will be done in different inflammation models, systemic inflammation, longitudinal paw inflammatory response, fibroblasts, and macrophages response. These mice will also be used in tumor formation experiments in skin and colon cancer models. These studies may shed light on the connection between inflammation, oncogenesis, and Cox-2.

Paw inflammation studies

Ex vivo imaging of systemic Cox-2 reporter expression in mouse organs

Ishikawa T, Jain, N.K., Taketo, M.M., Herschman, H.R. Imaging cyclooxygenase-2 (Cox-2) gene expression in living animals with a luciferase knock-in reporter gene. Mol. Imaging Biol. 2006;8:171-187.

Ishikawa T, Jain, N.K., Herschman, H.R. Feedback regulation of cyclooxygenase-2 transcription ex vivo and in vivo. Biochem Biophys Res Commun. 2009;378:534-538.

Ishikawa T, Herschman, H.R. Tumor formation in a mouse model of colitis associated colon cancer does not require COX-1 or COX-2 expression. Carcinogenesis. 2010 (in press).