Prostate cancer is the most prevalent cancer diagnosed among men in the United
States. The major green tea polyphenol epigallocatechin-3 gallate (EGCG) has been shown
to exert remarkable preventive effects against various types of cancer including
prostate cancer. Recent human clinical study proved that EGCG can prevent progression of
high grade prostatic intraepithelial neoplasia (PIN) to prostate cancer. Cellular
studies show that EGCG exhibits antiproliferative and apoptotic effects in
androgen-responsive LNCaP and androgen-unresponsive DU145, PC3 prostate cancer cell
lines. Previously, we have established a new type of prostate cancer line, androgen
repressed carcinoma of prostate (ARCaP). ARCaP cells are highly invasive and metastatic
and this cell line showed unique response to androgen since the hormone repressed the
proliferation. In this study, we show that androgen-repressed ARCaP prostate cancer cell
line, which represents more advanced and aggressive type of prostate cancer, is
resistant to EGCG treatment. In Western blot analyses, EGCG treated ARCaP cell line
showed increase in phosphorylation of NF-κB and decrease in activation of p38 MAPK and
Bax/Bcl-2 ratio. The levels of p21/CIP1/WAF1, cyclin-dependent kinases (CDKs) 2, 4, 6,
activated forms of Akt and c-Jun NH2-terminal protein kinase (JNK) remain unchanged in
EGCG treated ARCaP cells whereas decrease in active Akt, active JNK, and CDKs 2, 4, 6,
and increased level of p21/CIP1/WAF1 were observed in LNCaP cells upon EGCG treatment.
Moreover, EGCG treatment confers stronger adherence to types I, II, IV collagen
extracellular matrix proteins on ARCaP cells. On the contrary, LNCaP cells lost the
adhesion significantly to all extracellular matrix proteins tested, including collagens,
fibronectin, laminin, vitronectin, and tenascin. Most importantly, ARCaP cells formed
more colonies on soft agar in our anchorage-independent assay when treated with EGCG
whereas the colony forming ability of LNCaP cells was totally abolished under the same
condition. This study suggests that the use of tea catechin EGCG as anticancer agent may
not be effective for treating patients with androgen repressed subtype of prostate
cancer. This is the first study of apoptosis in ARCaP cell line. The GeneChip microarray
analysis revealed several genes that were differentially expressed when treated with
EGCG. Among those, matrix metalloproteinases (MMPs) 1 and 3 were significantly up
regulated in LNCaP cells upon EGCG treatment. Both RNA transcription and protein
secretion/activation of these MMPs were observed by GeneChip assay, reverse
transcription-polymerase chain reaction (RT-PCR) and by enzyme linked immunosorbent
assay (ELISA) which can detect proMMP1 and total MMP3 in cell culture media. This
feature is very unique in that (1) the MMPs are generally known to be involved in tumor
invasion and metastasis not the cell death, and (2) the other EGCG sensitive prostate
cancer cell lines, DU145 and PC3, did not display such characteristics. EGCG did not
affect the expression of these MMPs in ARCaP cells also. Using GeneChip analysis, we
found several genes whose expressions were oppositely regulated in LNCaP and ARCaP cells
upon EGCG treatment. These include early growth response -1 (EGR1), growth arrest and
DNA damage inducible gene 45 (GADD45). The expression level of EGR1 and GADD45 were
decreased in ARCaP cells but the level was increased in LNCaP cells after EGCG
treatment. These results suggest that the proapoptotic EGR1 and GADD45 may play a role
in EGCG induced apoptosis in LNCaP cells and thus may explain, at least in part, the
resistance of ARCaP cells against such apoptotic stimuli. The role of these proteins in
EGCG induced apoptosis is not known. The decreased level of topoisomerase II in EGCG
treated LNCaP cells is also exciting. Topoisomerases are necessary in DNA replication
and thus for survival of the organism. Since only LNCaP cells, but not ARCaP cells,
displayed reduced expression of topoisomerase II during EGCG induced apoptosis and since
ARCaP cells underwent apoptosis when treated with topoisomerase inhibitor etoposide, the
function of this enzyme might be involved in life or death decision of ARCaP and LNCaP
cells. Elucidating the molecular effects of these proteins and the mechanisms of how
these proteins function in ARCaP and LNCaP cell lines would help understanding the
prostate cancer and may help with future design of cancer chemopreventive and
chemotherapeutic agents. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial
fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2006. / Date of Defense: May 12, 2006. / Apoptosis, Tea, Catechin, Prostate, Cancer / Includes bibliographical references. / Qing-Xiang Amy Sang, Professor Directing Dissertation; Thomas C.S. Keller III, Outside Committee Member; Joseph B. Schlenoff, Committee Member; Hong Li, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_168547 |
| Contributors | Suh, Yewseok (authoraut), Sang, Qing-Xiang Amy (professor directing dissertation), III, Thomas C.S. Keller (outside committee member), Schlenoff, Joseph B. (committee member), Li, Hong (committee member), Department of Chemistry and Biochemistry (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
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