Control oftumorgrowthinanimals byinfusion of anangiogenesis inhibitor

Angiogenesis andtumor growth wereinhibited intwodifferent animal models byregional infusion ofapar- tially purified cartilage extract. Inrabbits bearing corneal im- plants ofV2carcinoma andreceiving theinhibitor, vascular growth rates were<3%ofthose incontrol animals receiving either Ringer's solution orbovine trypsin inhibitor (Trasylol). Subconjunctival B16melanoma implants- inmicereceiving the inhibitor weighed <2.5%ofimplants inmice receiving Ringer's solution, Trasylol, oralbumin. Histplogic study ofmajor organs andstandard blood tests revealed notoxic effects inanyofthe animals. Theinhibitor didnotretard thegrowth ofeither tumor cell type intissue culture atconcentrations ashigh as1mg/ml. These results suggest that thecartilage factor does notinterfere with thegrowth ofthetumor cell population directly butthat itprevents tumor growth byinhibiting angiogenesis. Thecapacity toinduce thegrowth ofnewcapillaries inthehost isacharacteristic commontomost solid malignant tumors. This phenomenon hasbeen called "tumor angiogenesis." Ithasbeen hypothesized (1, 2)that until atumor nodule ispenetrated by newcapillaries thelimitations imposed bydiffusion ofoxygen andnutrients prevent itfrom growing beyond afewmillimeters indiameter. This hypothesis implies that inhibition ofangio- genesis, bywhatever means, might control tdmor growth. For this reason, "antiangiogenesis" wasproposed asapotential therapeutic approach (3). Indirect evidence forthis hypothesis wasdrawn fromex- periments with tumors inisolated perfused organs (4), tumor spheroids grown insoft agar (2), andtumorimplants floating intheanterior chamber oftherabbit eye(5). Sorgente etat. (6) showed that whencartilage wasextracted with 1M guanidine itlost its resistance tovascular invasion. Eisenstein etal.(7) reported that a1M guanidine extract of cartilage inhibited thegrowth ofaortic endothelial cells in culture. BremandFolkman (8) showed that animplant of cartilage placed adjacent toaV2carcinoma intherabbit cornea inhibited growth ofnewblood vessels toward thetumor. Langer etal. (9) isolated apartially purified factor fromcartilage that, whenadministered locally byasustained-release polymer (10), inhibited angiogenesis induced byV2carcinoma implanted in therabbit cornea. Wenowshowthat this angiogenesis inhibitor limits tumor growth bystopping neovascularization whentheinhibitor is infused regionally ineither miceorrabbits. Furthermore, the inhibitor appears tohave notoxic effect ontumor cells andno short-term toxicity forthehost. Inonesetofexperiments, thetumor(V2carcinoma) was separated from thenearest vascular bedbyarelatively large Thepublication costs ofthis article weredefrayed inpart bypage charge payment. This article musttherefore behereby marked "ad- vertisement" inaccordance with 18U.S.C.§1734 solely toindicate this fact. 4331 distance (approximately 1.0mm)byimplanting thetumor i therabbit cornea. This system permitted daily measurements ofvessel growth rate anddemonstrated that vascular prolifer- ation wasinhibited and,subsequently, tumorgrowth was controlled. Inasecond set ofexperiments, thetumor (B16 melanoma) wasimplanted directly onto adense capillary bedinthemouse conjunctiva. This contiguous relationship between tumor and vascular bedmoreclosely resembles mosthumanandanimal tumors. Inthis experimental design, tumorgrowth wasmea- sured directly andthevascular response wasdetermined his- tologically. Regional infusion oftheangiogenesis inhibitor again prevented neovascularization andmarkedly limited tumor growth.