| Summary: | 碩士 === 國立臺灣大學 === 生命科學系 === 103 === Calreticulin (CRT), a multifunctional Ca2+-binding chaperone, has been shown to associate with poor prognosis in gastric cancer and bladder cancer. However, the roles of CRT in prostate cancer remain elusive. Prostate cancer is one of the most frequently diagnosed cancers in males and PC-3 is a popular cell model for investigating late stage prostate cancer. By comparing early stage prostate cancer cell line LNCaP with late stage prostate cancer cell line PC-3, we found that PC-3 showed higher cell adherent ability, cell proliferation ability and higher expression of vascular endothelial growth factor-A (VEGF-A), which is an important regulator for angiogenesis and tumor growth. Furthermore, knockdown of CRT in PC-3 caused lower cell adherent ability , cell proliferation ability and VEGF-A expression. These results indicate that CRT may be a poor prognosis factor in prostate cancer. Subsequently we further investigate the upstream regulation mechanism for calreticulin expression. Lysophosphatidic acid (LPA), a low molecular weight lipid, has been proved to stimulate cell migration, invasion and proliferation in prostate cancer cells. It has been demonstrated that LPA evoked Ca2+ mobilization from the lumen of the endoplasmic reticulum (ER) via phospholipase C (PLC) pathway. On the other hand, depletion of Ca2+ from ER activated CRT promoter activity in NIH/3T3 cells. Based on these evidences, we hypothesized that LPA regulate CRT expression in prostate cancer cells. By using RT-qPCR and Western Blotting, we found that CRT expression is up-regulated both in mRNA and protein level after LPA treatment. Pharmacological blockade by LPA1-specific antagonist AM966 or LPA1/3-selective antagonist Ki16425 inhibits the enhancement effect of LPA on CRT expression. In addition, LPA-dependent CRT expression was abolished in LPA1 and LPA3 stable knockdown PC-3 cells. Furthermore, activation of LPA3 by LPA3-specific agonist OMPT enhances CRT expression. These results indicated that activation of LPA1 and LPA3 up-regulate the expression of CRT. On the contrary, activation of LPA2 by LPA2-selective agonist MDP and LPA2-specific agonist GRI977143 impaired CRT expression. In conclusion, our findings suggested that, LPA1/3 and LPA2 inversely regulate CRT expression and subsequently regulate cell adhesion, cell proliferation and VEGF-A expression in PC-3 cells.
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