Basement membrane biosynthesis as a target to tumor therapy.

Tricyclodecan-9-yl-xanthate (D609) was identified as an agent that caused selective killing of tumor cells by an unknown mechanism of action. We report an inhibition by D609 of basement membrane collagen biosynthesis in the chick chorioallantoic membrane system in vitro. In the same system in vivo D609 inhibits angiogenesis. Also treatment of rats bearing Walker 256 carcinoma with D609 results in a dose-dependent antitumor effect. These results indicate that basement membrane synthesis may be a target for developing anti-angiogenic compounds with antitumor properties.

Antiangiogenic action of heparin plus cortisone is associated with decreased collagenous protein synthesis in the chick chorioallantoic membrane system.

In the chick chorioallantoic membrane system heparin plus cortisone caused a marked depression in the rate of collagenous protein biosynthesis in vivo during inhibition of angiogenesis. This suggests that monitoring the rate of collagenous protein biosynthesis in the chick chorioallantoic membrane system can be used as a quantitative method for evaluating angiogenesis inhibitors.

Inhibition of basement membrane biosynthesis prevents angiogenesis.

GPA1734, an inhibitor of BM collagen biosynthesis, was investigated in the CAM model system for its effect on angiogenesis. Evaluation of angiogenesis was performed by placing a thin plastic coverslip inscribed with concentric circles on the CAM and counting the number of vessels intercepting the circles. The rate of BM collagen biosynthesis was monitored using [U-14C] proline incorporation into CAM proteins and determining the collagenase-digestible protein fraction. A marked depression in the vascular density was observed in the CAM area under a plastic disc containing GPA1734 as compared to control discs placed on the CAM about 1 cm apart from days 9 to 12 of incubation. A concomitant decrease in collagenous protein biosynthesis was observed in the area under the discs containing GPA1734 and [U-14C]proline as compared to control discs containing only the radiolabeled proline. The forementioned effects of GPA1734 on CAM were specific because no similar effects were observed with a closely related compound, 9,10-dihydroxy-7-methyl-benzo[b]quinolizinium bromide or with GPA1734 plus Fe++, which did not affect the rate of BM collagen biosynthesis. These results suggest that inhibitors of BM collagen biosynthesis prevent angiogenesis by interfering with the formation of an essential component of the vessel wall. The search for such inhibitors may be a new approach in the development of antiangiogenic agents.

Rate of basement membrane biosynthesis as an index to angiogenesis.

A method was developed for assessing collagenous protein biosynthesis from [U-14C]proline in relation to angiogenesis in the chick chorioallantoic membrane (CAM). The rate of collagenous protein biosynthesis both in vitro and in vivo was maximum between days 8 and 11 of chick embryo development. This was the stage of maximum angiogenesis as shown by morphological evaluation of the vascular density. At day 10 the rate of collagenous protein biosynthesis was 11-fold higher than that of day 15, when angiogenesis had reached a plateau. The collagenous protein formed by CAM co-elutes on SDS-agarose chromatography with the collagenous component of [3H]-acetylated-basement membrane (BM) from bovine lens capsule. 8,9-dihydroxy-7-methyl-benzo[b]quinolizinium bromide (GPA1734), which was shown previously to be a specific inhibitor of BM collagen biosynthesis, caused about 80% reduction in collagenous protein synthesis by CAM. These results indicate that most of the collagenous protein synthesized by CAM was BM collagen and this can be used as a biochemical index of angiogenesis.