SummaryWe investigated the P450 dependent¯avonoid hydroxylase from the ornamental plant Catharanthus roseus. cDNAs were obtained by heterologous screening with the CYP75 Hf1 cDNA from Petunia hybrida. The C. roseus protein shared 68±78% identity with other CYP75s, and genomic blots suggested one or two genes. The protein was expressed in Escherichia coli as translational fusion with the P450 reductase from C. roseus. Enzyme assays showed that it was a¯avonoid 3¢,5¢-hydroxylase, but 3¢-hydroxylated products were also detected. The substrate speci®city was investigated with the C. roseus enzyme and a fusion protein of the Petunia hybrida CYP75 with the C. roseus P450 reductase. Both enzymes accepted¯avanones as well as¯avones, dihydro¯avonols and¯avonols, and both performed 3¢-as well as 3¢5¢-hydroxylation. Kinetics with C. roseus cultures on the level of enzyme activity, protein and RNA showed that the F3¢5¢H was present in dark-grown cells and was induced by irradiation. The same results were obtained for cinnamic acid 4-hydroxylase and avanone 3b-hydroxylase. In contrast, CHS expression was strictly dependent on light, although CHS is necessary in the synthesis of the F3¢5¢H substrates. Immunohistochemical localization of F3¢5¢H had not been performed before. A comparison of CHS and F3¢5¢H in cotyledons and¯ower buds from C. roseus identi®ed CHS expression preferentially in the epidermis, while F3¢5¢H was only detected in the phloem. The cell-type speci®c expression suggests that intercellular transport may play an important role in the compartmentation of the pathways to the different¯avonoids.

Purpose: Complete or partial loss of dihydropyrimidine dehydrogenase (DPD) function has been described in cancer patients with intolerance to fluoropyrimidine drugs like 5-fluorouracil (5-FU) or Xeloda. The intention of this population study is to assess and to evaluate gene variations in the entire coding region of the dihydropyrimidine dehydrogenase gene (DPYD), which could be implicated in DPD malfunction. Experimental Design: A cohort of 157 individuals was genotyped by denaturing highperformance liquid chromatography; 100 of these genotypes were compared with functional studies on DPD activity and mRNA expression. Results: Twenty-three variants in coding and noncoding regions of the DPYD gene were detected, giving rise to15 common haplotypes with a frequency of >1%. Rare sequence alterations included a frameshift mutation (295-298delTCAT) and three novel point mutations, 1218G>A (Met Ser). DPD enzyme activity showed high variation in the analyzed population and correlated with DPD mRNA expression. In particular, the novel variants were not accompanied with decreased enzyme activity. However, a statistically significant deviation from the median DPD activity of the population was associated with the mutations 1601G>A (Ser Dihydropyrimidine dehydrogenase (DPD; EC 1.3.1.2) is the initial and rate-limiting enzyme in the catabolism of pyrimidines. The homodimeric protein catalyzes the reduction of uracil and thymine in an NADPH-dependent manner and, furthermore, plays a critical role in the pharmacokinetics of fluoropyrimidine-based anticancer drugs. Eighty percent to 85% of administered standard doses of the common chemotherapeutic agent 5-fluorouracil (5-FU) are rapidly degraded by DPD to inactive compounds followed by excretion of a-fluoroh-alanine within 24 hours (1 -3). The rationally designed orally administered fluoropyrimidine drug Xeloda (capecitabine) is converted in situ into 5-FU due to intracellular thymidine phosphorylase activity. Capecitabine has been shown to be safer and more effective than 5-FU and has greater patient convenience (4, 5).

The glycosylphosphatidylinositol (GPI)-anchored, multifunctional receptor for the serine proteinase, urokinase plasminogen activator (uPAR, CD87), regulates plasminogen activation and cell migration, adhesion, and proliferation. uPAR occurs in functionally distinct, membrane-anchored and soluble isoforms (s-uPAR) in vitro and in vivo. Recent evidence indicates that s-uPAR present in the circulation of cancer patients correlates with tumor malignancy and represents a valuable prognostic marker in certain types of cancer. We have therefore analyzed the mechanism of uPAR shedding in vitro. We present evidence that uPAR is actively released from ovarian cancer cells since the rate of receptor shedding did not correlate with uPAR expression. While s-uPAR was derived from the cell surface, it lacked the hydrophobic portion of the GPI moiety indicating anchor cleavage. We show that uPAR release is catalyzed by cellular GPI-specific phospholipase D (GPI-PLD), an enzyme cleaving the GPI anchor of the receptor. Thus, recombinant GPI-PLD expression increased receptor release up to fourfold. Conversely, a 40% reduction in GPI-PLD activity by GPI-PLD antisense mRNA expression inhibited uPAR release by more than 60%. We found that GPI-PLD also regulated uPAR expression, possibly by releasing a GPI-anchored growth factor. Our data suggest that cellular GPI-PLD might be involved in the generation of circulating prognostic markers in cancer and possibly regulate the function of GPI-anchored proteins by generating functionally distinct, soluble counterparts.

The serine protease urokinase-type plasminogen activator, uPA, when bound to its specific receptor, uPAR (CD87), plays a significant role in tumor cell invasion and metastasis. In breast cancer, enhanced uPA antigen in the primary tumor is correlated with poor prognosis of the patient. In an in vivo nude mouse model, we tested tumor growth and metastasis of human breast carcinoma cells that had been transfected with an expression plasmid encoding a soluble form of uPAR (suPAR). We explored, whether suPAR/uPA interaction reduces the binding of uPA to cell surface-associated uPAR, and, as a consequence, could suppress tumor growth and metastasis of the human breast cancer cell line MDA-MB-231 BAG. Overexpressed, secreted suPAR was shown to bind and thus scavenge the uPA secreted by the transfected lines suPAR3 and suPAR10. In vitro, an overexpression of suPAR did not alter the proliferation rate of the transfected tumor cells, nor did it affect the expression of uPA. Overexpression of suPAR led to a reduction in the plasminogen activation-related proteolytic activity of breast carcinoma cells. Primary tumor growth in the mammary fat pad of nude mice was followed up for 52 days. Overexpression of suPAR correlated with a reduction in tumor growth (from day 21, reaching 30% by day 34) as well as lung colonization (lung metastasis-positive mice in suPAR3: 4 of 17; suPAR10: 3 of 10; parental MDA-MB-231 BAG: 13 of 18). We conclude that suPAR overexpression leading to effective scavenge of uPA impairs proteolysis as well as the tumor growth and metastatic potential of breast carcinoma cells in vivo. Cancer Gene Therapy (2000) 7, 292-299