Abstract: Novel polypeptide compositions are provided which inhibit human tumor cell growth, which may or may not stimulate autophosphorylation of pp60 src and induce the release of a 52kDal polypeptide from neoplastic cells. Individual polypeptides may be isolated from mammalian blood platelets by selected extraction and purification procedures, may be synthesized or produced by hybrid DNA technology.

Abstract: Novel cytotoxic agents are provided as small polypeptides related to a low molecular weight peptide derived from Crotalus atrox. The compounds may be used by themselves or in combination with other reagents, such as antibodies, for inhibiting cell growth.

Abstract: Polypeptides, polynucleotide sequences, DNA constructs and compositions are provided for the preparation and use of polypeptides associated with naturally occurring polypeptides found in brains. The small molecular weight polypeptides are growth inhibitors for neoplastic cells without inhibiting normal cells. The polypeptides comprise specific regions which are highly conserved, separated by less conserved regions. The polypeptides find use in inhibiting neoplastic growth and detecting receptors for the polypeptides. Antibodies are provided in conjunction with the polypeptides, which may be used together or separately for detecting the presence of the neoplastic cell retarding polypeptides.

Abstract: A substantially purified substance having the property of inhibiting tumor cell growth without inhibiting the growth of normal human cells and without having antiviral effect, further having the properties of: (a) ranging from about 3,500 to 45,000 daltons in molecular weight; (b) being heat stable at about 56.degree. C. when exposed for about 30 minutes; (c) possessing isoelectric point ranging from pI 4-8; and (d) eluting on high pressure liquid chromatography at about 10-35% of 2-propanol or about 25-50% of acetonitrile gradient, has been disclosed. The substance has utility as an antitumor or antineoplastic agent. The substance may also be useful as an index or tumorgenic activity in an organism. The mitogenic and growth stimulatory activity possessed by the substance of the present invention may be useful in wound healing and treating burn-victims.

Abstract: Novel polypeptide compositions are provided which inhibit human tumor cell growth, which may or may not stimulate autophosphorylation of pp60 src and induce the release of a 52 kDal polypeptide from neoplastic cells. Individual polypeptides may be isolated from mammalian blood platelets by selected extraction and purification procedures, may be synthesized or produced by hybrid DNA technology.

Abstract: Polypeptide compositions are provided which inhibit human tumor cell growth. The compositions may be obtained from mammalian blood platelets by selective extraction and purification procedures and are shown to inhibit tumor growth in vitro.