Date of Award

5-8-2015

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

Chemistry

First Advisor

Qian Wang

Abstract

Novel techniques for better studying cancer cell behavior and progression are extremely important. Our lab is interested in synthesizing specifically designed organic reagents and applying them in the studies of cancers. In this dissertation, we used organic probes to investigate cancer cells in the following topics: determination of amino acid concentration in different types of cancers, tumor toxicity of organic probes towards HER2 positive breast cancer cells, glycoproteins identification in breast cancer cells and development of enzyme activity assay for colon cancer cells.

The first chapter was focused on the determination of cysteine/homocysteine concentrations using turn-on sensors in cancer cells. Traditional methods such as HPLC are time consuming and cumbersome. DCP family probes were synthesized by our group previously, of which three probes reacted with cysteine/homocysteine specifically. To test the reactivity, the sensors were reacted with different substrates, including amino acid, nucleotides and proteins. All three sensors showed great selectivity towards cysteine and homocysteine. We confirmed the correlation between fluorescence intensity and cysteine concentration. Then liver cancer cell model which was previously reported with different intracellular cysteine concentration was used to test the sensitivity of sensor 2 inside live cells. The staining results from the liver cancer cells pretreated with 400 μM of cysteine showed higher intensity of fluorescence than the cells pretreated with 0 μM.

To study cysteine/homocysteine concentration in breast cancer cells, we used sensor 2 to stain genetic modified breast cell line MCF10A Vector and MCF10A HER2, which could mimic normal breast cells and breast cancer cells. MCF10A HER2 had higher cysteine/homocysteine level than MCF10A Vector.

Besides being good fluorescent probes, DCP family probes may also work as anti-tumor drugs. To study the toxicity of DCP family probes, we have performed cell viability assay to screen possible probes targeting the breast cancer marker HER2 in Chapter 2. Several probes were selected and the HER2 downstream signaling pathways were further studied. It was found that sensor 3 may be further modified for HER2 specific drugs to treat breast cancer.

In Chapter 3, we used bioorthoganol probes and correlating reporters to develop protocols for cell imaging and enrichment of glycoproteins. Using two different fluorescent reporters, we addressed the total glycosylation level as well as cell surface specific glycosylation in three different breast cell lines. We also confirmed that breast cancer cells had elevated the level of glycosylation compared to the normal breast cells in this chapter. To enrich glycoproteins, our lab modified a silicone bead with disulfide bond and triple bond at the end of surface chain. The triple bond could react with azide and be used to fish labeled proteins while the disulfide bond could be cleaved to release the proteins after enrichment. Using this probe, we tried different methods for glycoprotein purification. Unfortunately, we were not able to develop a protocol to enrich glycoproteins with these beads.

In the last Chapter, we moved to the enzyme activity detection in colon cancer cell line. A fluorescent sensor named RSAAA was synthesized specifically targeting on mitochondria and might be worked potentially as substrate for aldehyde dehydrogenase 2 (ALDH2). We tested the efficiency of this sensor working as substrate for ALDH2. Based on the results, we developed a protocol to stain cells and isolated populations with different ALDH2 activity. To study the role of ALDH2 in cancer stemness, ALDH2 high and ALDH2 low cell populations were isolated using the protocol set up in this chapter. The tumorigenicity of two populations was studied to identify the enrichment of cancer stem cells. In HCT15, ALDH2 high cells had more cancer stem cell population and were more malignant compared to the ALDH2 low population.

Specific designed probes could be powerful tools in the study of biological progress. We have devoted to the application of multiple probes to better understand and study cancer cells. Good communications between chemistry and biology help to support the translation from basic organic chemistry to the applications in biological fields. The emerging field of studies would be greatly appreciated in the development of new methods for biological processes.

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