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Xin-Hua Liu

  • ASSISTANT PROFESSOR Medicine
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Publications

Liu X, Yao S, Kirschenbaum A, Levine A. NS398, a selective cyclooxygenase-2 inhibitor, induces apoptosis and down-regulates Bcl-2 expression in LNCaP cells. Cancer Res 1998 Oct 1; 58(19): 4245-9.

Cyclooxygenase (COX)-2, an inducible enzyme that catalyzes the formation of prostaglandins and other eicosanoids from arachidonic acid, is constitutively expressed in LNCaP human prostate cancer cell line. To evaluate the potential role of COX-2 in prostate cancer, LNCaP cells were treated with NS398, a selective COX-2 inhibitor, and the effects on cell viability and apoptosis were determined. NS398 treatment induced apoptosis in LNCaP cells in a time- and dose-dependent fashion. Treatment with 100 microM NS398 caused a down-regulation in bcl-2 protein expression, followed by chromatin condensation, chromosomal DNA fragmentation, and changes in nuclear morphology detected by 4,6-diamidino-2-phenylindole staining, DNA fragmentation assay, and terminal deoxynucleotidyl transferase-mediated UTP-biotin nick end-labeling assay. In contrast, NS398 treatment had no effect on either cell viability or nuclear function and morphology in human fetal prostate fibroblasts. These results demonstrate that NS398 induces apoptosis in LNCaP cells but not in human fetal prostate fibroblasts, and that this induction is associated with a decreased level of bcl-2 protein.

Liu X, Kirschenbaum A, Yao S, Stearns ME, Holland J, Claffey K, Levine A. Upregulation of vascular endothelial growth factor by cobalt-induced hypoxia is mediated by persistent induction of cyclooxygenase-2 in a metastatic human prostate cancer cell line. Clin Exp Metastasis 1999 17(8):687-94.

Upregulation of vascular endothelial growth factor (VEGF) expression induced by hypoxia is crucial event leading to neovascularization. Cyclooxygenase-2, an inducible enzyme that catalyzes the formation of prostaglandins (PGs) from arachidonic acid, has been demonstrated to be induced by hypoxia and play role in angiogenesis and metastasis. To investigate the potential effect of COX-2 on hypoxia-induced VEGF expression in prostate cancer. We examined the relationship between COX-2 expression and VEGF induction in response to cobalt chloride (CoCl2)-simulated hypoxia in three human prostate cancer cell lines with differing biological phenotypes. Northern blotting and ELISA revealed that all three tested cell lines constitutively expressed VEGF mRNA, and secreted VEGF protein to different degrees (LNCaP > PC-3 > PC3ML). However, these cell lines differed in the ability to produce VEGF in the presence of CoCl2-simulated hypoxia. CoCl2 treatment resulted in 40% and 75% increases in VEGF mRNA, and 50% and 95% in protein secretion by LNCaP and PC-3 cell lines, respectively. In contrast, PC-3ML cell line, a PC-3 subline with highly invasive, metastatic phenotype, exhibits a dramatic upregulation of VEGF, 5.6-fold in mRNA and 6.3-fold in protein secretion after treatment with CoCl2. The upregulation of VEGF in PC-3ML cells is accompanied by a persistent induction of COX-2 mRNA (6.5-fold) and protein (5-fold). Whereas COX-2 expression is only transiently induced in PC-3 cells and not affected by CoCl2 in LNCaP cells. Moreover, the increases in VEGF mRNA and protein secretion induced by CoCl2 in PC-3ML cells were significantly suppressed following exposure to NS398, a selective COX-2 inhibitor. Finally, the effect of COX-2 inhibition on CoCl2-induced VEGF production was reversed by the treatment with exogenous PGE2. Our data demonstrate that VEGF induction by cobalt chloride-simulated hypoxia is maintained by a concomitant, persistent induction of COX-2 expression and sustained elevation of PGE2 synthesis in a human metastatic prostate cancer cell line, and suggest that COX-2 activity, reflected by PGE2 production, is involved in hypoxia-induced VEGF expression, and thus, modulates prostatic tumor angiogenesis.

Liu X, Kirschenbaum A, Yao S, Lee R, Holland J, Levine A. Inhibition of cyclooxygenase-2 suppresses angiogenesis and growth of prostate cancer in vivo. J Urol 2000 Sep; 164: 820-825.

Purpose: Cyclooxygenase (COX)-2, an inducible enzyme which catalyzes the formation of prostaglandins from arachidonic acid, is expressed in prostate cancer specimens and cell lines. To evaluate the in vivo efficacy of a COX-2 inhibitor in prostate cancer, NS398 was administered to mice inoculated with the PC-3 human prostate cancer cell line. Materials and Methods: A total of 28 male nude mice were inoculated subcutaneously with 1 million PC-3 cells. Tumors were palpable in all 28 animals 1 week after inoculation and mice were randomized to receive either vehicle (control) or NS398, 3 mg./kg. body weight, intraperitoneally three times weekly for 9 weeks. Tumors were measured at weekly intervals. After a 10-week experimental period, mice were euthanized and tumors were immuno- histochemically assayed for proliferation (PCNA), apoptosis (TUNEL) and microvessel density (MVD) (Factor-VIII-related antigen). Tumor VEGF content was assayed by Western blotting. Results: NS398 induced a sustained inhibition of PC-3 tumor cell growth and a regression of existing tumors. Average tumor surface area from control mice was 285 mm.2 as compared with 22 mm.2 from treated mice (93% inhibition, p <0.001). Immunohistochemical analysis revealed that NS398 had no effect on proliferation (PCNA), but induced apoptosis (TUNEL) and decreased MVD (angiogenesis). VEGF expression was also significantly down regulated in the NS398-treated tumors. Conclusions: These results demonstrate that a selective COX-2 inhibitor suppresses PC-3 cell tumor growth in vivo. Tumor growth suppression is achieved by a combination of direct induction of tumor cell apoptosis and down regulation of tumor VEGF with decreased angiogenesis

Industry Relationships

Physicians and scientists on the faculty of the Icahn School of Medicine at Mount Sinai often interact with pharmaceutical, device and biotechnology companies to improve patient care, develop new therapies and achieve scientific breakthroughs. In order to promote an ethical and transparent environment for conducting research, providing clinical care and teaching, Mount Sinai requires that salaried faculty inform the School of their relationships with such companies.

Dr.Liu is not currently required to report Industry relationships.

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