CMU undergrad isolates key cancer enzyme

Kimberly Kicielinski, a senior chemistry and psychology major, will leave Carnegie Mellon this May to attend medical school at Penn State. Kicielinski’s three years doing research at the UPMC Hillman Cancer Center have not only helped her in deciding her future career plans: They have also contributed to further cancer research.

Kicielinski was able to isolate a certain type of enzyme, known as the CYP3A4 enzyme. It is part of a family of enzymes, called cytochrome P450s (CYPs), which normally metabolize chemicals entering the body. The CYP3A4 enzyme was found in both the tumor cells and normal cells of kidneys. This enzyme is involved in the deactivation of carcinogens and the activation of certain anti-cancer drugs, specifically benzaldehyde dimethane sulfonate. The structure of this drug consists of two branched side arms that can cross-link DNA and prevent DNA replication of cancerous cells.

The procedures taken to isolate CYP3A4 were not simple. One of the main goals was to identify the enzyme that made the key metabolite, an N-dealkylation product that is characterized by a 258 mass to charge ratio (m/z) (as detected by mass spectrometry). First, mice liver cells were centrifuged and viewed through a spectrophotometer, which identifies compounds by weight. The microsomes, which are small particles in the cytoplasm consisting of fragmented endoplasmic reticulum and attached ribosomes, produced the most metabolite.

The different cofactors NADH and NADPH, which are energy sources for the enzyme, were added to mice liver enzymes. An m/z of 258 is most produced in NADPH, which pointed to the presence of CYPs. Next, the reaction was run in a nitrogen-saturated and then a carbon monoxide-saturated environment. The production of metabolite with an m/z of 258 was minimal in both, which also pointed towards the presence of CYPs. With the presence of a heme group, CYPs require oxygen to function. In oxygen deprived environments, the expected outcome of decreased metabolite production was seen.

If CYP activity is inhibited, then the production of metabolite, m/z 258, should be present in minimal amounts. Different chemical inhibitors, 3A4, 2D6, and 2C9, were added to human microsome. The 3A4 inhibitor showed the most inhibition. This result was supported by another experiment performed with commercial antibodies; CYP3A4 produced the most metabolite.

“Knowing the enzyme responsible for metabolism provides insights into the kinetics of the drug,” Kicielinski explained. Kicielinski was one of 79 (among 300) selected to present her research at the “Posters on the Hill” event on Capitol Hill last Monday and Tuesday. Kicielinski’s accomplishments, from her scientific discoveries to being a supplemental instructor for chemistry, exceed more than just academics; she is also on the cross country team. She is receiving scholarships from the chemistry department and Phi Beta Kappa.

“I think being an SI leader was one of my most important involvements. I really enjoyed it and it helped me gain useful skills, especially being able to explain concepts on a bunch of different levels,” Kicielinski said. She also added, “Being on the cross country team also exposed me to health-related problems, like orthopedic injuries. It also helped me with time management. I work better when I have a schedule.”

Kicielinski plans on becoming an oncologist. Although she enjoys being a researcher, she would rather be a clinician and have patient contact. Her advice to undergraduates interested in pursing a science related career is: “Always do what you want to do. Don’t do something just to build your résumé. Sometimes I do things, even if it’s to the detriment of my grade. Do what makes you happy.”