Herein is reported a convergent synthesis of isocombretastatins A, a novel class of potent antitubulin agents. These compounds having a 1,1-diarylethylene scaffold constitute the simplest isomers of natural Z-combretastatins A that are easy to synthesize without need to control the Z-olefin geometry. The discovery of isoCA-4 with biological activities comparable to that of CA-4 represents a major progress in this field.

Activation of the cellular Src tyrosine kinase depends upon dephosphorylation of the carboxyl-terminal inhibitory tyrosine phosphorylation site. Herein we show that Src isolated from human platelets and Jurkat T cells is preferentially dephosphorylated at its inhibitory phosphotyrosine site by the SHP-1 tyrosine phosphatase. The data also revealed association of Src with SHP-1 in both platelets and lymphocytes and the capacity of Src to phosphorylate SHP-1 and interact with the SHP-1 NH 2 -terminal SH2 domain in vitro. Analysis of Src activity in thymocytes from SHP-1-deficient motheaten and viable motheaten mice revealed this kinase activity to be substantially lower than that detected in wild-type thymocytes, but to be enhanced by in vitro exposure to SHP-1. Similarly, immunoblotting analysis of thymocyte Src expression before and after selective depletion of active Src protein indicated that the proportion of active relative to inactive Src protein is markedly reduced in motheaten compared with wild-type cells. These observations, together with the finding of reduced Src activity in HEY cells expressing a dominant negative form of SHP-1, provide compelling evidence that SHP-1 functions include the positive regulation of Src activation.Both the kinase and transforming activities of the pp60 c-src (Src) protein-tyrosine kinase (PTK) 1 are repressed by phosphorylation of a tyrosine residue within the Src carboxyl terminus (1-5). The negative regulatory effect of this phosphotyrosine (Tyr-530 and Tyr-529 in human and murine Src, respectively) has been ascribed to its association with the Src SH2 domain and consequent SH2, as well as SH3 domain-mediated intramolecular interactions that repress activity of the kinase domain (6 -8). The catalytic activities of the other Src family members are similarly inhibited by phosphorylation of this conserved C-tail tyrosine (9), and activation of each of these PTKs thus depends on dephosphorylation at this site. However, while several lines of evidence implicate the Csk tyrosine kinase (10 -12) as well as Src-mediated autophosphorylation (13) in the phosphorylation of the COOH-terminal regulatory tyrosine, relatively little is known about the mechanisms whereby this inhibitory phosphotyrosine residue is dephosphorylated and Src activation achieved. In contrast to the Src-related Lck and possibly Fyn PTKs, the Src COOH-terminal phosphotyrosine does not appear subject to dephosphorylation by the transmembrane protein-tyrosine phosphatase (PTP), CD45 (14 -16). Moreover, while Src activity has been found to be increased in rodent cell lines overexpressing the receptor-like protein-tyrosine phosphatase, RPTP␣ (17, 18), a direct role for this PTP in dephosphorylating Tyr-529 in vivo has not been established. However, recent data from studies of the SHP-1 tyrosine phosphatase, a cytosolic, dual SH2 domain-containing protein expressed primarily in hemopoietic and epithelial cells (19 -22), have raised the possibility that this PTP plays a role in the dephosphorylation and activation ...

The cytotoxic activity of a series of 23 new isoerianin derivatives with modifications on both the A and B rings was studied. Several compounds exhibited excellent antiproliferative activity at nanomolar concentrations against a panel of human cancer cell lines. The most cytotoxic compound, isoerianin (3), strongly inhibits tubulin polymerization in the micromolar range. Moreover, isoerianin leads to G2/M phase cell-cycle arrest in H1299 and K562 cancer cells, and strongly induces apoptosis. Isoerianin also disrupts the vessel-like structures formed by human umbilical vein endothelial cells (HUVECs) in vitro, suggesting that this compound may act as a vascular disrupting agent. It clearly appears that in this compound series, the 1,1-ethane bridge encountered in isoerianin derivatives can replace the 1,2-ethane bridge of natural erianin with no loss of activity. This reinforces the bioisosteric replacement approach in the combretastatin series previously reported by our research group.

The tetrapeptide acetyl-Ser-Asp-Lys-Pro (AcSDKP), purified from bone marrow and constitutively synthesized in vivo, belongs to the family of negative regulators of hematopoiesis. It protects the stem cell compartment from the toxicity of anticancer drugs and irradiation and consequently contributes to a reduction in marrow failure. This current work provides experimental evidence for another novel biologic function of AcSDKP. We report that AcSDKP is a mediator of angiogen-

The cytotoxic activities of 23 new isocombretastatin A derivatives with modifications on the B-ring were investigated. Several compounds exhibited excellent antiproliferative activity at nanomolar concentrations against a panel of human cancer cell lines. Compounds isoFCA-4 (2 e), isoCA-4 (2 k) and isoNH(2)CA-4 (2 s) were the most cytotoxic, and strongly inhibited tubulin polymerization with IC(50) values of 4, 2 and 1.5 microM, respectively. These derivatives were found to be 10-fold more active than phenstatin and colchicine with respect to growth inhibition but displayed similar activities as tubulin polymerization inhibitors. In addition, cell cycle arrest in the G(2)/M phase and subsequent apoptosis was observed in three cancer cell lines when treated with these compounds. The disruptive effect of 2 e, 2 k and 2 s on the vessel-like structures formed by human umbilical vein endothelial cells (HUVEC) suggest that these compounds may act as vascular disrupting agents. Both compounds 2 k and 2 s have the potential for further prodrug modification and development as vascular disrupting agents for treatment of solid tumors.

One new norlignan (1) and five new lignans (2-6) were isolated from the leaves and stems of Justicia patentiflora by a bioassay-guided purification. Five known compounds, carinatone, diphyllin, justicidin A, taiwanin E, and tuberculatin, were also found in J. patentiflora. Most of the new compounds display significant activity in in vitro cytotoxic assays against KB, HCT116, and MCF-7 cancer cell lines and arrest the cell cycle in the G0/G1 phase.

The synthesis and evaluation of a new series of IsoCombretaQuinolines (IsoCoQuines) 2 with a 2-substituted-quinoline in place of the 3,4,5-trimethoxyphenyl ring present in isoCA-4 and CA-4 are described. Most of these compounds displayed a potent cytotoxic activity (IC < 10 nM) against a panel of five human cancer cell lines and inhibited tubulin assembly at a micromolar level. The most potent analogue 2b, having a 3-hydroxy-4-methoxyphenyl as B-ring, led to cell cycle arrest in G2/M phase. Docking studies indicate that 2b showed a binding mode comparable to those previously observed with quinazoline analogous (IsoCoQ) and with isoCA-4 at the colchicine binding site of tubulin.

A novel series of dihydronaphtalene, tetrahydronaphtalene and naphtalene derivatives as restricted analogues of isoCA-4 were designed, synthesized and evaluated for their anticancer properties. High cell growth inhibition against four tumour cell lines was observed at a nanomolar level with dihydronaphtalenes 1d, e and 1h, tetrahydronaphtalene 2c and naphtalene 3c. Structure-activity relationships are also considered. These compounds exhibited a significant inhibitory activity toward tubulin polymerization (IC(50) = 2-3 μM), comparable to that of isoCA-4. The effect of the lead compounds 1e and 2c on the cancer cells tested was associated with cell cycle arrest in the G(2)/M phase. Docking studies reveal that these compounds showed a binding mode similar to those observed with their non-constraint isoCA-4 and isoerianin congeners.