A ring-deleted analog of atrial natriuretic factor--des[Gln18, Ser19, Gly20, Leu21, Gly22] ANF4-23-NH2 (C-ANF4-23)--binds with high affinity to approximately 99% of ANF receptors in the isolated perfused rat kidney. In this preparation, C-ANF4-23 is devoid of detectable renal effects and does not antagonize any of the known renal hemodynamic and natriuretic actions of biologically active ANF1-28. In contrast, both C-ANF4-23 and ANF1-28 increase sodium excretion and decrease blood pressure in intact anesthetized rats. This apparent contradiction is resolved by the finding that the ring-deleted analog markedly increases plasma levels of endogenous immunoreactive ANF in the rat. The results show that the majority of the renal receptors of ANF are biologically silent. This new class of receptors may serve as specific peripheral storage-clearance binding sites, acting as a hormonal buffer system to modulate plasma levels of ANF.

Transforming growth factor-␤ (TGF-␤) suppresses tumor formation by blocking cell cycle progression and maintaining tissue homeostasis. In pancreatic carcinomas, this tumor suppressive activity is often lost by inactivation of the TGF-␤-signaling mediator, Smad4. We found that human pancreatic carcinoma cell lines that have undergone deletion of MADH4 constitutively expressed high endogenous levels of phosphorylated receptor-associated Smad proteins (pR-Smad2 and pR-Smad3), whereas Smad4-positive lines did not. These elevated pR-Smad levels could not be attributed to a decreased dephosphorylation rate nor to increased expression of TGF-␤ type I (T␤R-I) or type II (T␤R-II) receptors. Although minimal amounts of free bioactive TGF-␤1 and TGF-␤2 were detected in conditioned medium, treatment with a pan-specific (but not a TGF-␤3 specific) TGF-␤-neutralizing antibody and with anti-␣ V ␤ 6 integrin antibody decreased steady-state pSmad2 levels and activation of a TGF-␤-inducible reporter gene in neighboring cells, respectively. Thus, activation of TGF-␤ at the cell surface was responsible for the increased autocrine endogenous and paracrine signaling. Blocking T␤R-I activity using a selective kinase inhibitor (SD-093) strongly decreased the in vitro motility and invasiveness of the pancreatic carcinoma cells without affecting their growth characteristics, morphology, or the subcellular distribution of E-cadherin and F-actin. Moreover, exogenous TGF-␤ strongly stimulated in vitro invasiveness of BxPC-3 cells, an effect that could also be blocked by SD-093. Thus, the motile and invasive properties of Smad4-deficient pancreatic cancer cells are at least partly driven by activation of endogenous TGF-␤ signaling. Therefore, targeting the T␤R-I kinase represents a potentially powerful novel therapeutic approach for the treatment of this disease.

Two cardioacceleratory peptides from the corpora cardiaca of Periplaneta americana have been purified by gel filtration and reversed-phase liquid chromatography. Based on analysis of the intact factors and their chymotryptic fragments, we have assigned the primary structure of these octapeptides as pGlu-Val-Asn-Phe-Ser-Pro-Asn-Trp-NH2, designated periplanetin CC-1, and pGlu-Leu-Thr-Phe-Thr-ProAsn-Trp-NH2, designated periplanetin CC-2. They represent new members of a family of invertebrate peptides that includes locust adipokinetic hormone and crustacean red-pigment concentrating hormone. Both peptides show adipokinetic activity in grasshoppers and hyperglycemic activity in cockroaches.One of these peptides (CC-2) has provocative sequence homology with the N112-terminal portion of glucagon.The insect corpora cardiaca (CC) are major neurohemal organs that are analogous to the vertebrate hypothalamohypophyseal system. Not only do the CC store and release products synthesized in the brain, but also they contain intrinsic glandular cells producing a variety of bioactive factors affecting developmental, metabolic, and myotropic processes (1). Many of these factors appear to be peptides; only one, adipokinetic hormone (AKH) from Locusta migratoria, has been identified (2).Corpora cardiaca of the cockroach Periplaneta americana have proven a rich and accessible source of bioactive factors. Previous studies have demonstrated that CC homogenates and partially purified fractions affect the cockroach heartbeat (3-6) and elevate the concentration of hemolymph trehalose (the main sugar in blood of most insects) (7-9). These factors appear to be peptides (3, 7), but it is difficult to assess how many are actually distinct substances or whether some of them have multiple activities (8,(10)(11)(12) In this paper we report the isolation and sequence determination of two structurally related octapeptides from the CC of P. americana that have cardioacceleratory and hyperglycemic activity in the host insect.MATERIALS AND METHODS Insects. Cockroaches (P. americana) were raised at 28°C and 50% relative humidity under a 16-hr light/8-hr dark photo regime and were fed on dry dog food. Corpora cardiaca with corpora allata attached were dissected from 0-to 6-wk-old cockroaches and collected in saline (5 mM CaCl2/1 mM MgCl2/5 mM KCI/140 mM NaCl/4 mM NaHCO3/5 mM trehalose/20 mM Hepes, pH 7.0) at 0°C prior to freezing (-20°C). A total of -4000 cockroach CC were used.Heart Bioassay. Aliquots of all fractions from purifications were assayed for bioactivity by using a semiisolated heart preparation (6). Heart rate was monitored with an impedance converter (UFI model 2991) connected to a frequency integrator and recorder. A heart was selected on the basis of frequency (-60 beats per min) and regularity and then was bathed in saline to stabilize (30 min). Test samples to be assayed were applied to the heart in a volume of 50 ,u.Carbohydrate and Lipid Bioassays. Hemolymph carbohydrate levels in P. americana and hemolymph lipid levels in th...

Transforming growth factor-beta (TGF-beta) is a proinvasive and immunosuppressive cytokine that plays a major role in the malignant phenotype of gliomas. One novel strategy of disabling TGF-beta activity in gliomas is to disrupt the signaling cascade at the level of the TGF-beta receptor I (TGF-betaRI) kinase, thus abrogating TGF-beta-mediated invasiveness and immune suppression. SX-007, an orally active, small-molecule TGF-betaRI kinase inhibitor, was evaluated for its therapeutic potential in cell culture and in an in vivo glioma model. The syngeneic, orthotopic glioma model SMA-560 was used to evaluate the efficacy of SX-007. Cells were implanted into the striatum of VM/Dk mice. Dosing began three days after implantation and continued until the end of the study. Efficacy was established by assessing survival benefit. SX-007 dosed at 20 mg/kg p.o. once daily (q.d.) modulated TGF-beta signaling in the tumor and improved the median survival. Strikingly, approximately 25% of the treated animals were disease-free at the end of the study. Increasing the dose to 40 mg/kg q.d. or 20 mg/kg twice daily did not further improve efficacy. The data suggest that SX-007 can exert a therapeutic effect by reducing TGF-beta-mediated invasion and reversing immune suppression. SX-007 modulates the TGF-beta signaling pathway and is associated with improved survival in this glioma model. Survival benefit is due to reduced tumor invasion and reversal of TGF-beta-mediated immune suppression, allowing for rejection of the tumor. Together, these results suggest that treatment with a TGF-betaRI inhibitor may be useful in the treatment of glioblastoma.